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7The role of biotherapies (interleukins, interferons and erythropoietin) in multiple myeloma
7 The role of biotherapies (interleukins, interferons and erythropoietin) in multiple myeloma G I U S E P P E AVVISATI MARIA TERESA PETRUCCI FRANCO MANDELLI
During the past decade, the rapid development of recombinant DNA technologies has permitted the production of large amounts of cytokines and growth factors, favouring the use of biotherapies in haematological malignancies. Among these products, the interferons (IFNs) have been the most extensively used in clinical trials (Mandelli et al, 1994); however, more recently, other cytokines and growth factors have been introduced in the clinical practice. In this review, we summarize the available results from published clinical trials dealing with the use of biotherapies in the treatment of multiple myeloma (MM) patients.
INTERLEUKINS Interleukins (ILs) represent a class of signal peptides that act as autocrine, paracrine and endocrine hormones. Moreover, they are involved in a variety of physiological and pathological activities, such as immunomodulation, growth promotion and growth inhibition (Aulitzky et al, 1994). Therefore, interleukins represent a major communication network in living organisms, and their numerous activities constitute the theoretical basis for their clinical use, particularly in malignant diseases. As for the clinical use of interleukins in MM, only limited data concerning IL-2 and antibody anti-IL-6 are available in the medical literature.
Biological role of IL-2 IL-2 was originally discovered in the supernatant fluid of human lymphocyte culture as an activity that supported the growth and proliferation of T lymphocytes. It is mainly secreted by T helper lymphocytes in response to IL-1 and antigen. Its reported biological effects have expanded, from the Bailli~re' s Clinical H a e m a t o l o g y -
Vol. 8, No. 4, December 1995 ISBN 0-7020-2073-7
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originally described capacity of supporting the growth and proliferation of T lymphocytes, to include interactions with macrophages, activated B cells, natural killer (NK) cells and other cytotoxic cells, leading to the use of IL2 as immunotherapy for several cancers (Whittington and Faulds, 1993). This variety of effects is mediated via specific cell surface receptors. The interaction of IL-2 with IL-2 receptors induces the proliferation and differentiation of a number of T lymphocyte subsets, and stimulates a cytokine cascade that includes several interleukins and interferons as well as tumour necrosis factor (Whittington and Faulds, 1993). The antitumour effects of IL-2 appear to be mediated by its effect on NK, lymphokine-activated killer (LAK) and other cytotoxic cells (Whittington and Faulds, 1993). Biological role of IL-2 in M M Following the focus of several authors in T cell subsets and functions in MM, it has been clarified that there is an influence of the T cell compartment on B cell proliferation and differentiation. Experimental studies have generally reported an imbalance in the ratio of the CD4+: CDS+ T lymphocytes (Metlstedt et al, 1982; Bergmann et al, 1984); moreover, a significantly lower LAK activity of peripheral blood T and non-T lymphocytes against standard LAK cell targets was found in MM patients than in normal controls (Massaia et al, 1990). Furthermore, the proportion of peripheral blood NK cells was reported to be increased in MM patients in earlier stages of the disease (Gonzales et al, 1992), while in advanced stages, low values were measured compared with normal controls (Osterborg et al, 1990). All these data associated with the findings of a strong bone marrow NK activity in MM patients (Uchida et al, 1984) suggest a tumour cell growth--modulating function of NK cells. Finally, Cimino et al (1990) have also found high serum concentrations of endogenously produced IL-2 in MM patients who have a better prognosis, and in vitro experiments have provided evidence that IL-2 activated lymphocytes can kill autologous myeloma cells and that control of the growth MM tumour cells by autologous T lymphocytes was enhanced by stimulation with IL-2 (Bianchi et al, 1989; Peest et al, 1989) As a consequence, all of the above observations actually reflect the presence of an active immunological tumour control mechanism in MM, giving the rationale for using IL-2 in MM patients. Therapeutic use of IL-2 Despite all the above data being in favour of the use of IL-2 in MM, no large series of myeloma patients treated with IL-2 has been reported, and only few early phase I studies of IL-2 administration have included myeloma patients. IL-2 was firstly used as maintenance therapy after autologous bone marrow transplantation (ABMT) to eradicate residual malignant cells and prevent or delay relapses (Gottlieb et al, 1990). These investigators reported that of four MM patients who received IL-2 after ABMT, two had
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measurable disease, and in both, the disease remained stable for more than 2 years after IL-2 treatment. Very recently, Peest et al (1995) evaluated the effects of low-dose recombinant IL-2 on several immunological parameters as well as on tumour response in 18 advanced-stage MM patients with primary or secondary resistance to standard chemotherapy. Patients received 9 MU/m 2 recombinant IL-2 twice daily on days 1 and 2, and 0.9 MU/m 2 twice daily for 5 subsequent days per week subcutaneously from days 3 to 56 (repeated every 12 weeks until progression). A response was experienced in 6 patients. Of these, 2 had an objective tumour mass reduction, and 4 a longlasting stable disease following tumour progression before initiation of IL2. During therapy, the diminished pre-treatment CD4+: CD8+ ratio normalized, and NK and LAK cell activity was significantly enhanced. Endogenous IL-2 production and elevated soluble IL-2 receptor serum concentrations were induced. Because most of the responders experienced termination of tumour progression rather than tumour regression, IL-2 maintenance of chemotherapy-induced remissions should be further investigated.
Biological role of IL-6 Human IL-6 is a pleiotropic, multifunctional cytokine produced by many cell types, for example T cells, monocytes/macrophages, fibroblasts, endothelial cells and hepatocytes, in response to stimuli that include antigens and other cytokines (Kishimoto, 1989). IL-6 was originally described as a differentiating factor for B cells (Hirano et al, 1986); however, subsequent studies have clarified that IL-6 not only induces B cells to produce immunoglobulins but also has a wide variety of biological actions on various tissues and cells (Kishimoto, 1989). In particular, IL-6 acts not only on B cells but also on haemopoietic progenitors and hepatocytes, and is involved in haemopoiesis and acute phase reactions. It also acts on nerve cells, epidermal keratinocytes and kidney mesangial cells. The physiological effects exerted by IL-6 include induction of immunoglobulin synthesis in activated B cells, activation of T cells and NK cells, stimulation of megakaryopoiesis, induction of acute-phase protein synthesis by the liver and induction of fever.
Biological role of IL-6 in MM Because MM represents the malignant transformation of a B cell clone into immunoglobulin-producing plasma cells, several investigators have studied the role of IL-6 in MM. A critical review of the literature indicates that IL-6 is capable of stimulating the growth of myeloma cells (Zhang et al, 1989; Suzuki et al, 1992), suggesting a possible involvement of IL-6 in the generation of MM. Fresh myeloma cells often produce IL-6 constitutively, express IL-6 receptor and exhibit enhanced DNA synthesis in response to exogenous IL-6 (Svenatsu et al, 1990).
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The source of IL-6 in MM remains controversial. While some experiments suggest that, in myelomatous bone marrow, IL-6 is produced by the bone marrow stromal cells (paracrine mechanism) (Klein et al, 1989; Nilsson et al, 1990), others have found that IL-6 is produced mainly by plasma cells (autocrine loop) in response to exogenous IL-6 (Kawano et al, 1988; Hata et al, 1993). Finally, in MM, serum levels of IL-6 have been reported to be a marker of high tumour burden and correlated with disease severity, and may therefore have prognostic implications (Bataille et al, 1989; Ludwig et al, 1991; Du Villard et al, 1995; Pelliniemi et al, 1995). Therapeutic use of anti-IL-6 monocional antibodies Taking into account the above data, Klein et al (1991) have used routine anti IL-6 monoclonal antibodies (MoAbs) to treat a patient with plasma cell leukaemia. The patient was treated for 2 months with daily intravenous anti-IL-6 MoAbs, obtaining a substantial although short-lived, response. This trial provided the in vivo evidence of the central role played by IL6 in the myeloma cell growth. In fact, anti-IL-6 MoAbs blocked myeloma cell proliferation for 45 days in vivo. Moreover, it demonstrated the feasibility of blocking IL-6 activity for 2 months without undesirable effects and with improvement in the patient's clinical status throughout the treatment. Furthermore, the doses of anti-IL-6 MoAbs injected were sufficient completely to block the production of C-reactive protein (an acute-phase reactant protein) throughout the treatment. INTERFERONS The term 'interferon' was originally used to identify a soluble proteinic factor produced by cells in response to a wide range of viruses (Isaacs and Lindemann, 1957). At present, three main subtypes of human IFN have been recognized--o~, [3 and y--produced by leukocytes, fibroblasts and T lymphocytes respectively. To exert their action on cells, IFNs must bind to specific cell surface membrane receptors. Two distinct IFN receptors are present on the cell membrane: the receptor for both c~ and [3 IFN, and the receptor for Y IFN. Following the binding of IFNs to their specific receptors, the IFN-receptor complex transmits signals to the nucleus for inducing, upregulating or downregulating the expression of some cellular genes. Biological role of IFNs in malignancies IFNs have an antitumoural activity via antigrowth and immunomodulatory properties. The potent inhibitory effect of IFNs on cell proliferation has been clearly demonstrated in several laboratory studies, even though the mechanisms
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responsible for this antiproliferative effect range from the downregulation of some oncogenes (Samid et al, 1985; Kimci, 1987) to the inhibition of protein translation (Revel et al, 1980; Senn, 1984; Bishoff and Samuel, 1985). The immunomodulatory effect of IFNs may also play a role in tumour control because IFNs, as members of the cytokine network, induce the secretion of other cytokines. The most relevant immune change produced by IFNs appears to be the enhancement of the cytotoxic activity of NK cells and macrophages (Edwards et al, 1984). Biological role of IFNs in MM In patients with MM, it has been demonstrated that IFN-{x possesses the ability to increase the NK activity of peripheral lymphocytes (Heinhorn et al, 1982), as well as raise the levels of ~2-microglobulin (Tienhaara et al, 1991). In vitro studies have demonstrated that IFN-cx decreases the production of the monoclonal immunoglobulin by the myelomatous plasma cells (Tanaka et al, 1989), independently of the cytotoxic effect of IFN-{x on myeloma cells (Grand6r et al, 1991). Moreover, IFN-o~ decreases both in vitro colony formation and the labelling index of myeloma cells (Salmon et al, 1983; Brenning, 1985; Brenning et al, 1985). Furthermore, in vitro studies indicate that IFN-o~ inhibits both IL-6-dependent and independent myeloma cell lines, while IFN-y inhibits only the IL-6-dependent cell lines (Jernberg-Wiklund et al, 1991; Portier et al, 1993). Therapeutic use of IFNs A comprehensive review dealing with the results obtained in clinical trials using IFN-{x in the treatment of MM has been already published (Avvisati and Mandelli, 1992). From this review, it emerged that the best results have been obtained combining IFN-¢~ and conventional chemotherapy for induction treatment in newly diagnosed MM patients, or using IFN-cx as maintenance treatment in those patients who have already responded to conventional induction therapies. Here, we give an update of the results obtained in MM using IFN-cx as induction treatment, associated with standard chemotherapies, or as maintenance treatment. IFN-a associated with conventional induction therapy in newly diagnosed MM patients The evidence of in vitro synergy between IFN-cx and some chemotherapeutic agents, such as cyclophosphamide, melphalan, Adriamycin and vinca alkaloids (Aapro et al, 1983; Balkwill et al, 1984; Balkwill and Moodey, 1985; Welander et al, 1985), and the results obtained using IFN-o~ as a single agent for inducing a response in MM, stimulated some investigators to evaluate the role of IFN-cx combined with conventional chemotherapies for induction treatment in newly diagnosed MM patients.
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Following the good results obtained in early studies using this modality of treatment (Cooper et al, 1986; Oken et al, 1989), several co-operative groups designed randomized clinical trials to better evaluate the role of IFN-cz combined with standard induction chemotherapies in untreated M M patients. The published results of these randomized trials are conflicting. Some studies did not indicate that the addition of IFN-0t to standard induction chemotherapies improves either the response rate or the duration of response and/or survival (Corrado et al, 1991; Cooper et al, 1993), whereas other studies have confirmed a higher response rate and a longer response and/or survival duration in the arm containing IFN-cz (Scheithauer et al, 1989; Montuoro et al, 1990; Osterborg et al, 1993). In particular, the CALGB study comparing melphalan and prednisone (MP) + IFN-c~2b versus MP as induction therapy of previously untreated 278 MM patients did not show any advantage to the concomitant delivery of MP + IFN-o~2b as initial treatment for patients with MM (Cooper et al, 1993); these results are in agreement with those observed by Corrado et al (1991). On the contrary, three other randomized studies indicate that, by combining IFN-c~ with standard induction chemotherapy, it is possible to obtain a better response rate as well as a longer duration of survival (Scheithauer et al, 1989; Montuoro et al, 1990; Osterborg et al, 1993). In the more recent of these studies (C)sterborg et al, 1993), the MGCS (Myeloma Group of Central Sweden), using natural IFN-~, has demonstrated a response rate of 68% in the MP + natural IFN-~ treated group, compared with 42% (P = 0.0001) in the MP-treated group. This difference was more marked in patients with IgA or Bence Jones myeloma: 85% of IgA myelomas and 71% of Bence Jones myelomas responded to MP + natural IFN-cz, compared with 48% and 27% respectively responding to MP treatment ( P = 0.001). There was no difference in the overall survival between the two treatment groups. However, the survival of 72 patients with IgA or Bence Jones myeloma randomized to receive MP + natural IFN-~ was significantly longer (median 32 months) than that of 71 patients treated with MP alone (median 17 months) (P < 0.05). These conflicting results may be due either to the different schedules of IFN administration or to the different IFN dosages used by the investigators, as well as to different elegibility criteria.
IFN-o~ as maintenance treatment in MM patients responding to standard induction therapies The rationale for using IFN-~ as maintenance treatment in MM patients responding to conventional induction chemotherapy originated from in vitro evidence that, at the end of the induction treatment, the myeloma cells of responding patients are in a 'plateau phase', similar to the Go phase of the cell cycle. Therefore, considering the anti-proliferative effects of IFNs and that IFN-c£ markedly reduces the self-renewal capacity of myelomaforming cells, it appears more appropriate to use IFN-cx as an agent for
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maintaining the response obtained with conventional induction treatments. At present the results of four randomized studies dealing with the use of IFN-ot are available in the medical literature; these studies have been conducted in different parts of the world: three in Europe (Mandelli et al, 1990; Peest et al, 1990; Westin et al, 1995) and one in USA, by the South West Oncology Cooperative Group (SWOG). In addition to these studies, two other ongoing randomized trials are being conducted in Canada (Browman et al, 1994) and Australia (Joshua et al, 1994), and have been published only as abstracts.
The Italian study (Mandelli et al, 1990) This was the first published study in which IFN-~ was employed as an agent for maintaining the response already obtained with conventional therapy, rather than as an agent for inducing a response. MM patients responding to 12-monthly courses of traditional first-line induction chemotherapy were randomized to receive (N = 50) or not (N = 51) recombinant IFN-ct2b as maintenance treatment at the dose of 3 MU three times per week subcutaneously until relapse. The overall results of the study were as follows: the median duration of response (from the time of randomization to maintenance treatment) was 26 months in the patients given IFN and 14 months in the untreated patients (P = 0.0002), while the median duration of survival (from the time of randomization to maintenance therapy) was 52 months in the IFN group and 39 months in the control group ( P = 0.0526). However, among the patients who had an objective reponse to induction chemotherapy, the difference in survival was statistically significant (P = 0.0352). After 5 more years of follow-up from the inclusion of the last patient in this study, the updated results confirm that IFN-c~2b is a useful therapeutic tool in controlling the plateau phase of responding MM patients (P = 0.0002). However, despite the median survival duration for responding patients being 50.9 months in the IFN arm, compared with 36.6 months in the control arm, the difference between the two arms is no more significant using the log-rank test, while using the Wilcoxon statistical test, the difference between the two arms is marginally significant (P=0.05) (personal unpublished data).
The German study (Peest et al, 1990) In this study, 71 out of 140 MM patients with stable disease after induction chemotherapy were randomized to receive or not receive IFN-~2b as maintenance treatment. As for the relapse rate, the published results reveal no differences between the two randomized groups, the median response duration being 7 months in both groups. No data on the overall survival duration of both groups were available. However, in this study, the absence of benefit in the IFN-~-maintained group may be due to the presence of some differences in the modalities of randomization with respect to the other studies, such as: (a) the absence of a stratification for the induction
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treatment before the randomization to the maintenance arm, and (b) the shorter duration of the plateau phase, compared with the longer duration of the plateau phase of other studies.
The Swedish study (Westin et al, 1995) In this study, following the MP induction treatment, 155 out of 314 evaluable patients achieved a plateau phase, defined as response (greater than 50% reduction of the monoclonal component) lasting 4 months. Of these 155 patients in the plateau phase, 125 were randomized to receive (N = 61) or not receive (N = 64) IFN-~2b at the dose of 5 MU three times per week subcutaneously until relapse. After an average observation time from randomization of 51 months (minimum 36 months), the plateau phase was significantly prolonged in the group of patients treated with interferon (P < 0.0001). In particular, the median duration of plateau was 13.9 months in the IFN arm and 5.7 months in the control arm. However, the median survival from randomization was similar in both groups (36 versus 35 months). This well-designed study indicates that the use of IFN-c~ as maintenance treatment in MM patients responding to initial induction treatment and achieving a well defined 'plateau phase' can significantly prolong the response duration, and it therefore partially confirms the results of the Italian study.
The SWOG study (Salmon et al, 1994) Patients achieving a response, defined as 75% of myeloma mass regression, to conventional induction chemotherapies, at random assigned to treatment with VMCP/VBAP (vincristine + melphalan + cyclophosphamide + prednisone/vincristine + BCNU + Adriamycin + prednisone) or VAD (vincristine + Adriamycin + prednisone) or VMCPP/VBAPP) (VMCP + alternate day prednisone between chemotherapy cycles/VBAP + alternate day prednisone between chemotherapy cycles) were randomized to receive (N= 97) or not receive (N= 96) IFN-~2b until relapse. No differences in relapse-free or overall survival duration for patients receiving IFN have been observed. The median relapse-free duration from the start of maintenance therapy was 12 months in the IFN-~2b ann and 11 months in the control arm (P = 0.95). Moreover, median overall survival duration was 32 months in the IFN-~2b arm and 38 months in the control arm (P =0.39). Two main differences between the SWOG and the Italian and Swedish studies may be responsible for the different results observed. Firstly, in the SWOG study, the responding patients are only those with a reduction of at least 75% of myeloma mass, while in the Italian and Swedish studies the cut-off for response is a reduction of at least 50% of myeloma mass. Secondly, the patient population with stage III myeloma is greater, while the number with stage I myeloma is lower in the SWOG study. As a consequence, the proportion of cases with high-risk myeloma is higher in this study than in the Italian and Swedish studies.
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It is therefore possible that these differences in response definition and in patient population may partially explain the negative results of this study, taking into account that encouraging results have been obtained by using IFN0~2b + dexamethazone (DEX) in those 79 patients with a lower reduction (less than 75%) of myeloma mass after induction chemotherapy, who had an overall median survival of 48 months from the start of IFN-~2b + DEX.
The Canadian study (Browman et al, 1994) In this trial, when response criteria were met, patients were randomized to IFN-~2b at a dose of 2 MU/m ~ three times per week subcutaneously until relapse (N = 85), or to a control group (N = 92). MP induction therapy was continued in both arms until the monoclonal protein had stabilized for at least 4 months; thereafter, MP was discontinued. Median progression-free survival was 16 months for IFN and 12 months for the controls, while median overall survival was 39 and 34 months for the IFN and control groups respectively. The relative risk (RR) of progression was 0.61 (95% CI 0.42-0.87; P = 0.007) and the RR for death was 0.60 (95% CI 0.38-0.95; P = 0.03), both favouring IFN-c~2b. Therefore, IFN-o~2b maintenance in this study prolongs the duration of response and overall survival of patients with MM.
The Australian study (Joshua et al, 1994) A total of 1 t 3 M M patients were randomized to receive, as induction, the combination therapy of prednisone, cyclophosphamide, Adriamycin and BCNU (PCAB), with or without IFN-o~2b at a dose of 3 MU/m 2 5 days a week subcutaneously at the commencement of the third cycle of treatment. Whereas PCAB was given for a total of 12 cycles, IFN-~2b was continued until progression. Despite the fact that the addition of IFN-~2b to PCAB during induction therapy did not produce any benefit in terms of response to treatment or achievement of the plateau phase, there was a trend for patients in the IFN-~2a arm to have a longer duration of plateau phase and overall survival than patients on the PCAB alone arm.
IFN-~ as maintenance treatment in MM patients after transplantation procedures High-dose chemotherapy (HDC) was developed to improve survival of aggressive myeloma. However, even though HDC is capable of giving a high response rate, it is associated with severe life-threatening toxicities that can be reduced by autologous bone marrow transplantation (ABMT) or peripheral stem cell infusion (PSCI). As a consequence, an increasing number of patients with MM ale now treated with HDC followed by ABMT or PSCI. However, relapse remains a major problem, so in an attempt to improve the response and survival durations of these patients, a number of investigators have begun to use 1FN-~ as maintenance treatment following HDC and ABMT or PSCI in myeloma. Attal et al were among the first investigators who adopted this type of
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therapy in previously untreated aggressive myeloma. They have recently published the results of a trial initiated to determine the feasibility and efficacy of three-phase treatment, consisting of an induction chemotherapy followed by high-dose melphalan and total body irradiation, supported by unpurged ABMT and IFN-o~ maintenance treatment. After a median followup of 24 months after diagnosis and 15.5 months after ABMT, only one of the 15 patients who had obtained a complete response (CR) has relapsed, while among the 15 patients who did not obtain a CR, there were 7 relapses (Attal et al, 1992). The results of Attal et al have been very recently confirmed in a randomized study by English investigators (Cunningham et al, 1993). In this study, 84 patients with myeloma were randomized to receive maintenance IFN-c~2b, 3 MU/m 2 subcutaneously three times weekly, or no treatment following induction therapy with C-VAMP (cyclophosphamide, vincristine, Adriamycin and methylprednisolone), consolidated with highdose melphalan (HDM) 200 mg/m2 and unpurged ABMT. At a median follow-up of 24 months, median progression-free survival from high dose melphalan (HDM) was 27 months in the control group and 39 months in the IFN-o~2b group (P < 0.025). For the 62 patients who achieved CR with HDM, there was a significant prolongation of remission (P < 0.01), and 53% of these patients who received IFN-o~2b have remained in remission 4 years after treatment. However, for partial response and non-responders to HDM, there was no significant prolongation of progression-free survival. Overall survival was also significantly longer for IFN-~x2b group, with 1 death, compared with 6 deaths in the control group (P < 0.05). The results obtained in these two studies suggest that the small residual tumour mass of patients achieving CR after ABMT could be higly sensitive to IFN-o~ maintenance treatment. As far as IFN-I3 and IFN-7 are concerned, to date there are only a few negative published reports in which these types of IFN have been used as salvage treatment, with an overall response rate of less than 5%. Therefore, it does not seem at present that 13and 7 IFNs used alone may have a role in MM. However, experimental reports indicate that, at least for IFN-7, there may be a potential therapeutic use in MM, considering that this cytokine is capable of inhibiting either the myeloma cell proliferation, by blocking IL6-receptor expression (Portier et al, 1993) or the cytokine-mediated bone resorption, one of the major clinical problems in MM. ERYTHROPOIETIN
Erythropoietin (EPO) is a glycoprotein hormone normally produced by the peritubular cells of the kidney in response to tissue hypoxia (Koury et al, 1988; Lacombe et al, 1988). It has its predominant effect on the committed erythroid cells, colony-forming unit erythroids (CFU-E), promoting their proliferation and differentiation into proerythroblasts (Eaves and Eaves, 1978). To exert these functions, EPO must bind to specific cell surface EPO
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receptors; however, the molecular events that are activated after binding of EPO to these receptors are still unknown (Krantz, 1991). EPO in clinical settings was first used in patients undergoing dialysis who had anaemia owing to chronic renal failure. These patients showed a consistent and sustained beneficial effect on haematocrit, reticulocyte count and transfusion requirements. Extending these treatments to patients with renal failure not yet requiring dialysis, the same results were obtained (Lim et al, 1989). Since then, EPO has been used not only in patients with anaemia due to renal failure, but also in patients with other types of chronic anaemia, such as those secondary to cancer. Therapeutic use of erythropoietin in MM In patients with MM, anaemia is a common complication, with multifactorial pathogenic mechanisms, including extensive bone marrow involvement by tumour cells, cytokine production, renal failure and prior cytotoxic chemotherapy. Therefore, because it is often characterized as the anaemia of chronic disease, it seemed appropriate to use EPO for reducing either the symptoms due to anaemia or the number of packed red cell transfusions needed to ameliorate the low haemoglobin levels. The first study dealing with the use of EPO in the treatment of the anaemia associated with MM was published in 1990 (Ludwig et al, 1990). EPO was administered subcutaneously three times a week at an initial dose of 150 U/kg body weight to 13 patients with advanced MM, all previously treated with chemotherapy + local radiotherapy, for a median period of 30 weeks. If no response was observed within 3 weeks, the dose was increased to 200 U/kg body weight; if after a further 3 weeks of treatment there was no substantial response, the dose was increased by 50 U/kg. If a response occurred, the dose was reduced to maintain the haemoglobin levels between 12 and 14 g/dl. Eleven patients (85%) responded to EPO, obtaining a steady increase in haemoglobin levels of at least 2 g/dl without any adverse side-effects and with excellent tolerance of the treatment. Moreover, while only some of the patients had an improvement in performance status, all the 11 responding patients had experienced subjective improvement in their quality of life. A second study on the use of EPO in MM, published by Barlogie (1993) showed that patients with a relatively high level of endogenous EPO (> 100U/I) had late responses or failed to respond. On the contrary, a beneficial effect of EPO therapy was observed in those patients with anaemia associated to inappropriately low endogenous EPO levels. Both these studies provide clinical evidences that EPO is a promising and effective therapeutic tool for the management of MM-associated anaemia. THE F U T U R E The next years will better clarify whether, and to what extent, the use of biotherapies will increase in MM. So far, their potential role has been only
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partially explored, and interventions directed at manipulating the complex cytokine networks pertinent to the pathogenesis of MM are an exciting new area of investigation, which might be the cornerstone of future treatment of this disease. The mounting evidence that IL-1 [3 and TNF-~, along with IL6, play a role in myeloma cell proliferation and in mediating bone destruction (Garrett et al, 1987; Carter et al, 1990) provides the biological background for using anti-IL-1 and anti-TNF MoAbs as future possible interventions in MM patients. Moreover, recent data indicate that retinoic acid can be beneficial in MM because it is able to significantly inhibit human myeloma cell growth in vitro (Palumbo et al, 1995) by downregulating IL-6 receptors and interfering with IL-6 signal transduction (Sidell et al, 1991; Ogata et al, 1994),
SUMMARY During the last decade, the availability of large numbers of cytokines and growth factors has greatly favoured the use of biotherapies in several haematological diseases. For MM, the majority of clinical studies have dealt with the use of IFN-~. From these studies it appears that IFN-~ has a definite role in the treatment of MM especially in the setting of minimal residual disease, as maintenance therapy after response to conventional therapies or HDC followed by BMT procedures or PBSCI. Data on the use of EPO have consistently demonstrated the role of this growth factor in ameliorating the grade of anaemia as well as the quality of life of those MM patients whose disease is complicated by the presence of a severe or moderate anemia. Despite the large amount of experimental data indicating a role for IL-2 and IL-6 in controlling tumour growth, there are only a few clinical studies dealing with their use in MM. From these, it appears that IL-2 and anti-IL6 antibodies should be further investigated as therapeutic tools useful in maintaining responses, because results show that they arrest tumour progression rather than aid, tumour regression. Finally, in the next years, there will be a wider diffusion of biotherapies in MM that should take into account the roles that IL-113 and TNFo~ play in myeloma cell proliferation and bone destruction and the finding that retinoic acid is capable of inhibiting the growth of human myeloma cells in vitro through modulation of IL-6 and its receptor.
REFERENCES Aapro MS, Alberts DS & Salmon SE (1983) Interactions of human leukocyte interferon with vinca alkaloids and other chemotherapeutic agents against human tumors in clonogenic assay. Cancer Chemotherapy and Pharmacology 10: 161-166. Attal M, Huguet F, Schlaifer D et al (1992) Intensive combined therapy for previously untreated aggressive myeloma. Blood 79:1 t30-1136. Aulitz&y WA, Schuler M, Peschel C & Huber C (1994) lnterleukins: clinical pharmacology and therapeutic use. Drugs 48: 667-677.
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Avvisati G & Mandelli F (1992) The role of Interferon-~ in the management of myelomatosis. Hematolog?#Oncology Clinic's of North America 6: 395-405. Balkwill FR & Moodey EM (1985) Positive interactions between human interferon and cyclophosphamide or adriamycin in a human tumor model system. Cancer Research 44: 906-908. Balkwill FR, Monshowitz S & Seilman S (1984) Positive interaction between interferon and chemotherapy due to direct tumor action rather than effects on host drug-metabolizing enzymes. Cancer Research 44: 5249-5255. Baflogie B (1993) Treatment of the anemia of multiple myeloma: the role of recombinant erythropoietin. Seminars in Hematology 30: 25-27. Bataille R, Jourdan M, Zhang XG & Klein B (t989) Serum levels of interleukin-6, a potent myeloma cell growth factor, as lxeflectof disease severity in plasma cell dyscrasia. Journal of Clinical Investigation 84:2008-201 l. Bergmann L, Mitrou PS, Weber KC & Kelber W (1984) Imbalances ofT-cells subsets in monoclonal gammopathies. Cancer Immunology and lmmunotherapy 17:112-116. Bianchi AC, Hesplop HE, Veys P e t al (1989) Enhancement of monoclonal antibody dependent cell mediated cytotoxicity by IL-2 and GM-CSF. British Journal of Haematology 73: 468474. Bishoff JR & Samuel CE (1985) Mechanism of interferon action. Journal of Biological Chemistry 260: 8237-8239. Brenning G (1985) The in vitro effect of leukocyte alpha-interferon on human myeloma cells in a semisolid agar culture system. Scandinavian Journal of Haematology 35: 178-185. Brenning G, Ahre A & Nilsson K (1985) Correlation between in vitro and in vivo sensitivity to human leukocyte interferon in patients with multiple myeloma. Scandinavian Journal of Haematology 35: 543-549. Browman GP, Rubin S, Walker Iet al (1994) Interferon a-2b (IFN) maintenance therapy prolongs progression-free and overall survival in plasma cell myeloma (PCM): results of a randomized trial. Proceedings of the American Society of Clinical Oncology 13:408 (abstract 139I). Carter A, Merchav S, Silvian-Draxler Iet al (1990) The rote of interleukin 1 and tumor necrosis factor alpha in human multiple myeloma. British Journal of Haematology 74:424-431. Cimino G, Avvisati G, Amadori Set al (1990) High serum 11,-2 levels are predictive of prolonged survival in multiple myeloma. British Journal of Haematology 75- 373-377. Cooper MR, Fefer A, Thompson Jet al (1986). Alpha-2 interferon/melphalan/prednisone in previous untreated patients with multiple myeloma: a phase I-II triM. Cancer Treatment Reports 70: 473-476. Cooper RB, Dear K, McIntyre RO et al (1993) A randomised trial comparing melphalan/prednisone with or without interferon alfa-2b in newly diagnosed patients with multiple myeloma: a cancer and leukemia group B study. Journal of Clinical Oncology 11: 155-160. Col~do C, Flores A, Pavlovsky S et al (199t) Randomised trial of melphalan (L-PAM)-prednisone (PRED) with or without recombinant Alpha2 interferon (r ~2 IFN) in multiple myetoma. Proceedings of the American Society of Clinical Ontology 10:304 (Abstract 1064). Cunningham D, Viner C, Montes A et al (1993) A randomised trim of maintenance therapy with Intron-A following high-dose melphalan and ABMT in myeloma. Proceedings of the American Society of Clinical Oncology 12:364 (abstract 1232). Du ViUard L, Guiguet M, Casasnovas RO et al (1995) Diagnostic value of serum IL-6 level in monoelonal gammopathies. British Journal of Haematology 89: 243-249. Eaves CJ & Eaves AC (1978) Erytbropoietin (Ep) dose-response curves for three classes of erythroid progenitors in normal human marrow and in patients with polycythemia vera. Blood 52: 1196-1210. Edwards BS, Hawkins MJ & Borden EC (1984) Comparative in vivo and in vitro action of human NK cells by two recombinant ~-interferons differing in antiviral activity. Cancer Research 44: 3135-3139. Garrett LR, Durie BG Nedwin GE et al (1987) Production of the bone resorbing cytokine lymphotoxin by cultured human myeloma cells. New England Journal of Medicine 317: 526532. Gonzales M, San Miguel JF, Gascon A e t al (1992) Increased expression of natural-killer-associated and activation antigens in multiple myeloma. American Journal of Hematology 39: 84-89. Gottlieb DJ, Prentice HG, Mehta AB et al (1990) Malignant plasma cells are sensitive to MHC unrestricted lysis: preclinical and clinical studies of interleukin-2 in the treatment of multiple myeloma. British Journal of Haematology 75: 499-505.
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Grandtr D, von Stedingk LV, von Stedingk M e t al (I99t) Influence of interferon on antibody production and viability of malignant cells from patients with multiple myeloma. European Journal of Haematology 46: 17-25. Hata H, Xiao H, Petrucci MT et al (1993) lnterleukin-6 gene expression in multiple myeloma: a characteristic of inunature tumor cells. Blood 81: 3357-3364. Heinhorn S, Ahre A, Blomgren H et al (1982) Interferon and natural killer activity in MM. Lack of correlation between interferon-induced enhancement of natural killer activity and clinical response to human interferon-alpha. International Journal of Cancer 30: 167-172. Hirano T, Yasukawa K, Harada H et al (1986) Complementary cDNA for a novel haman interleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin. Nature 324: 73-76. Isaacs A & Lindemann J (1957) Virus interference. Proceedings of the Royal Society of London (Biology) 147: 249-267. Jernberg-Wiklund H, Pette~son M & Nilsson K (1991) Recombinant interferon-gamma inhibits the growth of IL-6-dependent human multiple myeloma cell lines in vitro, European Journal of Haematology 46: 231-236. Joshua DE, Penny R, Baldwin R et al (1994) The study of combination therapy plus or minus Roferon A in multiple myeloma. Blood 84: Supplement 1: 179a (abstract 701). Kawano M, Hirano T, Matsuda T et al (1988) Autocrine generation and essential requirement of BSF/2 IL-6 for human multiple myeloma. Nature 322: 73. Kimci A (1987) Autocrine interferon and the suppression of the c-myc nuclear oncogene. Interferon 8:86-110. Kishimoto T (1989) The biology of interleukin 6. Blood 74: 1-10. Klein B, Zhang XG, Jourdan Met al (1989) Paracrine but not autocrine regulation of myeloma cell growth and differentiation by interleukin-6. Blood 73:517-522, Klein B, Wijdenes J, Zhang XG et al (1991) Marine anti-IL-6 monoclonal antibody therapy for a patient with plasma cell leukemia. Blood 78: 1198-1204. Koury ST, Bondurant MC & Koury MJ (1988) Localization of erythropoietin synthesizing cells in marine kidneys by in situ hybridization. Blood 71: 524-527. Krantz SB (1991) Erythropoietin. Blood 77: 419-434. Lacombe C, Da Silva J-L, Bruneval P et al (1988) Peritubular cells are the site of erythropoietin synthesis in murine hypoxic kidney. Journal of Clinical Investigation 81: 620-623. Lira VS, DeGowin RL, Zavala D et al (1989) Recombinant human erythropoietin treatment in predialysis patients: a double-blind placebo-controlled trial. Annals of Internal Medicine 110: 108-114. Ludwig H, Fritz E, Kotzmann H et al (I990) Erythropoietin treatment of anemia associated with multiple myeloma. New England Journal of Medicine 322: 1693-1699. Ludwig H, Nachbaur DM, Fritz E et al (1991) Interleukin-6 is a prognostic factor in multiple myeloma. Blood 7: 2794-2795. Mandelli F, Arcese W & Avvisati G (1994) The interferons in haematological malignancies. Baillikre 's Clinical Haematology 7:91-113. Mandelli F, Avvisati G, Amadori S et al (1990) Maintenance treatment with recombinant interferon alfa-2b in patients with multiple myeloma responding to conventional induction chemotherapy. New England Journal of Medicine 322: 1430-1434. Massaia M, Bianchi A, Dianzani U et al (1990) Defective intedeukin-2 induction of lymphockineactivated killer (LAK) activity in peripheral blood T lymphocytes of patients with monoclonal gammopathies. Clinical and Experimental Immunology 79: 100-104. Mellstedt H, Holm G, Pettersson D et al (1982) T cells in monoclonal gammopathies. Scandinavian Journal of Haematology 29: 57--64. Montuoro A, De Rosa L, De Blasio A et al (1990) Alpha-2a interferon/melphalan/prednisone versus melphalardprednisone in previously untreated patients with multiple myeloma. British Journal of Haematology 76: 365-368. Nilsson K, Jerveberg H & Patterson M (1990) IL-6 as a growth factor for human multiple myeloma cells--a short overview. Current Topics in Microbiology and Immunology 166: 3-12, Ogata A, Nishimoto N, Shima Y et al (1994) Inhibitory effect of all-trans retinoic acid on the growth of freshly isolated myeloma cells via interference with interleukin-6 signal tmnsduction. Blood 84: 3040-3046. Oken MM, Kyle RA, Greipp PR et al (1989) Complete remission (CR) induction with VBMCP + interferon (rlFNo~2) in multiple myeloma: 3 year follow-up. Proceedings of the American Society of Clinical Oncology 8:272 (abstract 1062).
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Osterborg A, Nilsson B, Bj6rkolm M e t al (1990) Natural killer cell activity in monoclonal gammopathies: relation to disease activity, European Journal of Haematology 45: 153-157. Osterborg A, Bj6rkhohn M, Bj6eman M e t al (1993) Natural interferon-~ in combination with melphalan/prednisone versus melphalan/prednisone in the treatment of multiple myelorna stage II and IlI: a randomised study from the myeloma group of central Sweden. Blood 81: 1428-1434. Palumbo A, Battaglio S, Napoli P et al (1995) Retinoic acid inhibits the growth of human myeloma cells in vitro. British Journal of Haematology 89: 555-560. Peest D, de Vries I, HOscher R, et al (1989) Effect of Interleukin-2 on the ex vivo growth of human myeloma cells. Cancer Immunology and Immunotherapy 30: 227-232. Peest D, Deicher H, Coldewey R et al (1990) Melphalan and prednisone (MP) versus vincristine, BCNU, adriamycin, melphalan and dexamethasone (VBAMDex) induction chemotherapy and interferon maintenance treatment in multiple myeloma. Current results of a multicenter trial. Onkologie 13: 458-460. Peest I3, Leo R, Bloche S e t al (1995) Low-dose recombinant interleukin-2 therapy in advanced multiple myeloma. British Journal of Haematology 89: 328-337. Pelliniemi T-T, Irjala K, Mattila K et al (1995) Immunoreactive interleukin-6 and acute phases proteins as prognostic factors in multiple myeloma. Blood 85:765-771. Pottier M, Zhang XG, Caron E et al (1993) Gamma interferon in multiple myeloma: inhibition of interleukin-6 (IL-6)-dependent myeloma cell growth and downregulation of IL-6-receptor expression in vivo. Blood 81: 3076-3082. Revel M, Kimci A & Shulman L (1980) Role of interferon-induced enzymes in the antiviral and antimitogenic effects of interferon. Annals of the New York Academy of Sciences 350: 459-473. Salmon SE, Durie BG, Yung L e t al (1983) Effects of cloned leukocyte interferons in the human tumor stem cell assay. Journal of Clinical Oncology 1: 217-225. Salmon SE, Crowley J J, Grogan TM et al (1994) Combination chemotherapy, glucocorticoids, and Interferon alfa in the treatment of multiple myeloma: a Southwest Oncology Group Study. Journal ~[ Clinical Oncology 12: 2405-2414. Samid D, Chang Ell & Friedman RM (1985) Development of transformed phenotype induced by a human RAS oncogene is inhibited by interferon. Biochemical and Biophysical Research Communications 126: 509-516. Scheithauer W, Cortelezzi A, Fritz E et al (1989) Combined c~-2c-interferon/VMCP polychemotherapy versus VMCP polychemotherapy as induction therapy in multiple myeloma: a prospective randomised trial. Journal of Biological Response Modifiers 8:109-115. Senn CC (1984) Biochemical pathways in interferon action. Pharmacology and Therapeutics 24: 235-257. Sidell N, Taga T, Hirano T et al (1991) RA induced growth inhibitor of a human cell line, by downregulation of IL-6 receptors. Journal of Immunology 146: 3809-3814. Suzuki H, Yasukawa K, Saito T et al (1992) Anti-human interleukin-6 receptor antibody inhibits human myeloma growth in vivo. European Journal oflmmunology 22: 1989-1993. Svenatsu S, Hibi M, Sugita T et al (1990) IL-6 and IL-6 R in myeloma plasmacytoma. Current Topics in Microbiology and Immunology 166:13-22. Tanaka H, Tanabe O, Iwato K et al (1989) Sensitive inhibitory effect of interferon-alpha on M-protein secretion of human myeloma cells. Blood 74: 1718-1722. Tienhaara A, Remes K & Pelliniemi TT (1991) Alpha interferon raises serum beta-2-microglobulin in patients with multiple myeloma. British Journal of Haematology 77: 335-338. Uchida A, Yagita M, Sugiyama H et al (1984) Strong natural killer (NK) cell activity in bone marrow of myeloma patients: accelerated maturation of bone marrow NK cells and their interaction with other bone marrow cells. International Journal of Cancer 34: 375-381. Welander CE, Morgan TM, Homesley HD et al (1985) Combined recombinant human interferon alpha 2 and cytotoxic agents in a elonogenic assay. International Journal of Cancer 35: 721-729. Westin J, R6djer S, Turesson Iet al (1995) Interferon alfa-2b versus no maintenance therapy during the plateau phase in multiple myeloma: a randomized study. British Journal of HaematoIogy 89: 561-568. Whittington R & Faulds D (1993) lnterleukin-2. A review of its pharmacological properties and thel~peutic use in patients with cancer. Drugs 46: 446-514. Zhang XG, Klein B & Bataille R (1989) lnterleukin-6 is a potent myeloma-cell growth factor in patients with aggressive multiple myeloma. Blood 74:11-13.
During the past decade, the rapid development of recombinant DNA technologies has permitted the production of large amounts of cytokines and growth factors, favouring the use of biotherapies in haematological malignancies. Among these products, the interferons (IFNs) have been the most extensively used in clinical trials (Mandelli et al, 1994); however, more recently, other cytokines and growth factors have been introduced in the clinical practice. In this review, we summarize the available results from published clinical trials dealing with the use of biotherapies in the treatment of multiple myeloma (MM) patients.
INTERLEUKINS Interleukins (ILs) represent a class of signal peptides that act as autocrine, paracrine and endocrine hormones. Moreover, they are involved in a variety of physiological and pathological activities, such as immunomodulation, growth promotion and growth inhibition (Aulitzky et al, 1994). Therefore, interleukins represent a major communication network in living organisms, and their numerous activities constitute the theoretical basis for their clinical use, particularly in malignant diseases. As for the clinical use of interleukins in MM, only limited data concerning IL-2 and antibody anti-IL-6 are available in the medical literature.
Biological role of IL-2 IL-2 was originally discovered in the supernatant fluid of human lymphocyte culture as an activity that supported the growth and proliferation of T lymphocytes. It is mainly secreted by T helper lymphocytes in response to IL-1 and antigen. Its reported biological effects have expanded, from the Bailli~re' s Clinical H a e m a t o l o g y -
Vol. 8, No. 4, December 1995 ISBN 0-7020-2073-7
815 Copyright © 1995, by Bailli~re Tindall All rights of reproduction in any form reserved
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originally described capacity of supporting the growth and proliferation of T lymphocytes, to include interactions with macrophages, activated B cells, natural killer (NK) cells and other cytotoxic cells, leading to the use of IL2 as immunotherapy for several cancers (Whittington and Faulds, 1993). This variety of effects is mediated via specific cell surface receptors. The interaction of IL-2 with IL-2 receptors induces the proliferation and differentiation of a number of T lymphocyte subsets, and stimulates a cytokine cascade that includes several interleukins and interferons as well as tumour necrosis factor (Whittington and Faulds, 1993). The antitumour effects of IL-2 appear to be mediated by its effect on NK, lymphokine-activated killer (LAK) and other cytotoxic cells (Whittington and Faulds, 1993). Biological role of IL-2 in M M Following the focus of several authors in T cell subsets and functions in MM, it has been clarified that there is an influence of the T cell compartment on B cell proliferation and differentiation. Experimental studies have generally reported an imbalance in the ratio of the CD4+: CDS+ T lymphocytes (Metlstedt et al, 1982; Bergmann et al, 1984); moreover, a significantly lower LAK activity of peripheral blood T and non-T lymphocytes against standard LAK cell targets was found in MM patients than in normal controls (Massaia et al, 1990). Furthermore, the proportion of peripheral blood NK cells was reported to be increased in MM patients in earlier stages of the disease (Gonzales et al, 1992), while in advanced stages, low values were measured compared with normal controls (Osterborg et al, 1990). All these data associated with the findings of a strong bone marrow NK activity in MM patients (Uchida et al, 1984) suggest a tumour cell growth--modulating function of NK cells. Finally, Cimino et al (1990) have also found high serum concentrations of endogenously produced IL-2 in MM patients who have a better prognosis, and in vitro experiments have provided evidence that IL-2 activated lymphocytes can kill autologous myeloma cells and that control of the growth MM tumour cells by autologous T lymphocytes was enhanced by stimulation with IL-2 (Bianchi et al, 1989; Peest et al, 1989) As a consequence, all of the above observations actually reflect the presence of an active immunological tumour control mechanism in MM, giving the rationale for using IL-2 in MM patients. Therapeutic use of IL-2 Despite all the above data being in favour of the use of IL-2 in MM, no large series of myeloma patients treated with IL-2 has been reported, and only few early phase I studies of IL-2 administration have included myeloma patients. IL-2 was firstly used as maintenance therapy after autologous bone marrow transplantation (ABMT) to eradicate residual malignant cells and prevent or delay relapses (Gottlieb et al, 1990). These investigators reported that of four MM patients who received IL-2 after ABMT, two had
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measurable disease, and in both, the disease remained stable for more than 2 years after IL-2 treatment. Very recently, Peest et al (1995) evaluated the effects of low-dose recombinant IL-2 on several immunological parameters as well as on tumour response in 18 advanced-stage MM patients with primary or secondary resistance to standard chemotherapy. Patients received 9 MU/m 2 recombinant IL-2 twice daily on days 1 and 2, and 0.9 MU/m 2 twice daily for 5 subsequent days per week subcutaneously from days 3 to 56 (repeated every 12 weeks until progression). A response was experienced in 6 patients. Of these, 2 had an objective tumour mass reduction, and 4 a longlasting stable disease following tumour progression before initiation of IL2. During therapy, the diminished pre-treatment CD4+: CD8+ ratio normalized, and NK and LAK cell activity was significantly enhanced. Endogenous IL-2 production and elevated soluble IL-2 receptor serum concentrations were induced. Because most of the responders experienced termination of tumour progression rather than tumour regression, IL-2 maintenance of chemotherapy-induced remissions should be further investigated.
Biological role of IL-6 Human IL-6 is a pleiotropic, multifunctional cytokine produced by many cell types, for example T cells, monocytes/macrophages, fibroblasts, endothelial cells and hepatocytes, in response to stimuli that include antigens and other cytokines (Kishimoto, 1989). IL-6 was originally described as a differentiating factor for B cells (Hirano et al, 1986); however, subsequent studies have clarified that IL-6 not only induces B cells to produce immunoglobulins but also has a wide variety of biological actions on various tissues and cells (Kishimoto, 1989). In particular, IL-6 acts not only on B cells but also on haemopoietic progenitors and hepatocytes, and is involved in haemopoiesis and acute phase reactions. It also acts on nerve cells, epidermal keratinocytes and kidney mesangial cells. The physiological effects exerted by IL-6 include induction of immunoglobulin synthesis in activated B cells, activation of T cells and NK cells, stimulation of megakaryopoiesis, induction of acute-phase protein synthesis by the liver and induction of fever.
Biological role of IL-6 in MM Because MM represents the malignant transformation of a B cell clone into immunoglobulin-producing plasma cells, several investigators have studied the role of IL-6 in MM. A critical review of the literature indicates that IL-6 is capable of stimulating the growth of myeloma cells (Zhang et al, 1989; Suzuki et al, 1992), suggesting a possible involvement of IL-6 in the generation of MM. Fresh myeloma cells often produce IL-6 constitutively, express IL-6 receptor and exhibit enhanced DNA synthesis in response to exogenous IL-6 (Svenatsu et al, 1990).
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The source of IL-6 in MM remains controversial. While some experiments suggest that, in myelomatous bone marrow, IL-6 is produced by the bone marrow stromal cells (paracrine mechanism) (Klein et al, 1989; Nilsson et al, 1990), others have found that IL-6 is produced mainly by plasma cells (autocrine loop) in response to exogenous IL-6 (Kawano et al, 1988; Hata et al, 1993). Finally, in MM, serum levels of IL-6 have been reported to be a marker of high tumour burden and correlated with disease severity, and may therefore have prognostic implications (Bataille et al, 1989; Ludwig et al, 1991; Du Villard et al, 1995; Pelliniemi et al, 1995). Therapeutic use of anti-IL-6 monocional antibodies Taking into account the above data, Klein et al (1991) have used routine anti IL-6 monoclonal antibodies (MoAbs) to treat a patient with plasma cell leukaemia. The patient was treated for 2 months with daily intravenous anti-IL-6 MoAbs, obtaining a substantial although short-lived, response. This trial provided the in vivo evidence of the central role played by IL6 in the myeloma cell growth. In fact, anti-IL-6 MoAbs blocked myeloma cell proliferation for 45 days in vivo. Moreover, it demonstrated the feasibility of blocking IL-6 activity for 2 months without undesirable effects and with improvement in the patient's clinical status throughout the treatment. Furthermore, the doses of anti-IL-6 MoAbs injected were sufficient completely to block the production of C-reactive protein (an acute-phase reactant protein) throughout the treatment. INTERFERONS The term 'interferon' was originally used to identify a soluble proteinic factor produced by cells in response to a wide range of viruses (Isaacs and Lindemann, 1957). At present, three main subtypes of human IFN have been recognized--o~, [3 and y--produced by leukocytes, fibroblasts and T lymphocytes respectively. To exert their action on cells, IFNs must bind to specific cell surface membrane receptors. Two distinct IFN receptors are present on the cell membrane: the receptor for both c~ and [3 IFN, and the receptor for Y IFN. Following the binding of IFNs to their specific receptors, the IFN-receptor complex transmits signals to the nucleus for inducing, upregulating or downregulating the expression of some cellular genes. Biological role of IFNs in malignancies IFNs have an antitumoural activity via antigrowth and immunomodulatory properties. The potent inhibitory effect of IFNs on cell proliferation has been clearly demonstrated in several laboratory studies, even though the mechanisms
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responsible for this antiproliferative effect range from the downregulation of some oncogenes (Samid et al, 1985; Kimci, 1987) to the inhibition of protein translation (Revel et al, 1980; Senn, 1984; Bishoff and Samuel, 1985). The immunomodulatory effect of IFNs may also play a role in tumour control because IFNs, as members of the cytokine network, induce the secretion of other cytokines. The most relevant immune change produced by IFNs appears to be the enhancement of the cytotoxic activity of NK cells and macrophages (Edwards et al, 1984). Biological role of IFNs in MM In patients with MM, it has been demonstrated that IFN-{x possesses the ability to increase the NK activity of peripheral lymphocytes (Heinhorn et al, 1982), as well as raise the levels of ~2-microglobulin (Tienhaara et al, 1991). In vitro studies have demonstrated that IFN-cx decreases the production of the monoclonal immunoglobulin by the myelomatous plasma cells (Tanaka et al, 1989), independently of the cytotoxic effect of IFN-{x on myeloma cells (Grand6r et al, 1991). Moreover, IFN-o~ decreases both in vitro colony formation and the labelling index of myeloma cells (Salmon et al, 1983; Brenning, 1985; Brenning et al, 1985). Furthermore, in vitro studies indicate that IFN-o~ inhibits both IL-6-dependent and independent myeloma cell lines, while IFN-y inhibits only the IL-6-dependent cell lines (Jernberg-Wiklund et al, 1991; Portier et al, 1993). Therapeutic use of IFNs A comprehensive review dealing with the results obtained in clinical trials using IFN-{x in the treatment of MM has been already published (Avvisati and Mandelli, 1992). From this review, it emerged that the best results have been obtained combining IFN-¢~ and conventional chemotherapy for induction treatment in newly diagnosed MM patients, or using IFN-cx as maintenance treatment in those patients who have already responded to conventional induction therapies. Here, we give an update of the results obtained in MM using IFN-cx as induction treatment, associated with standard chemotherapies, or as maintenance treatment. IFN-a associated with conventional induction therapy in newly diagnosed MM patients The evidence of in vitro synergy between IFN-cx and some chemotherapeutic agents, such as cyclophosphamide, melphalan, Adriamycin and vinca alkaloids (Aapro et al, 1983; Balkwill et al, 1984; Balkwill and Moodey, 1985; Welander et al, 1985), and the results obtained using IFN-o~ as a single agent for inducing a response in MM, stimulated some investigators to evaluate the role of IFN-cx combined with conventional chemotherapies for induction treatment in newly diagnosed MM patients.
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Following the good results obtained in early studies using this modality of treatment (Cooper et al, 1986; Oken et al, 1989), several co-operative groups designed randomized clinical trials to better evaluate the role of IFN-cz combined with standard induction chemotherapies in untreated M M patients. The published results of these randomized trials are conflicting. Some studies did not indicate that the addition of IFN-0t to standard induction chemotherapies improves either the response rate or the duration of response and/or survival (Corrado et al, 1991; Cooper et al, 1993), whereas other studies have confirmed a higher response rate and a longer response and/or survival duration in the arm containing IFN-cz (Scheithauer et al, 1989; Montuoro et al, 1990; Osterborg et al, 1993). In particular, the CALGB study comparing melphalan and prednisone (MP) + IFN-c~2b versus MP as induction therapy of previously untreated 278 MM patients did not show any advantage to the concomitant delivery of MP + IFN-o~2b as initial treatment for patients with MM (Cooper et al, 1993); these results are in agreement with those observed by Corrado et al (1991). On the contrary, three other randomized studies indicate that, by combining IFN-c~ with standard induction chemotherapy, it is possible to obtain a better response rate as well as a longer duration of survival (Scheithauer et al, 1989; Montuoro et al, 1990; Osterborg et al, 1993). In the more recent of these studies (C)sterborg et al, 1993), the MGCS (Myeloma Group of Central Sweden), using natural IFN-~, has demonstrated a response rate of 68% in the MP + natural IFN-~ treated group, compared with 42% (P = 0.0001) in the MP-treated group. This difference was more marked in patients with IgA or Bence Jones myeloma: 85% of IgA myelomas and 71% of Bence Jones myelomas responded to MP + natural IFN-cz, compared with 48% and 27% respectively responding to MP treatment ( P = 0.001). There was no difference in the overall survival between the two treatment groups. However, the survival of 72 patients with IgA or Bence Jones myeloma randomized to receive MP + natural IFN-~ was significantly longer (median 32 months) than that of 71 patients treated with MP alone (median 17 months) (P < 0.05). These conflicting results may be due either to the different schedules of IFN administration or to the different IFN dosages used by the investigators, as well as to different elegibility criteria.
IFN-o~ as maintenance treatment in MM patients responding to standard induction therapies The rationale for using IFN-~ as maintenance treatment in MM patients responding to conventional induction chemotherapy originated from in vitro evidence that, at the end of the induction treatment, the myeloma cells of responding patients are in a 'plateau phase', similar to the Go phase of the cell cycle. Therefore, considering the anti-proliferative effects of IFNs and that IFN-c£ markedly reduces the self-renewal capacity of myelomaforming cells, it appears more appropriate to use IFN-cx as an agent for
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maintaining the response obtained with conventional induction treatments. At present the results of four randomized studies dealing with the use of IFN-ot are available in the medical literature; these studies have been conducted in different parts of the world: three in Europe (Mandelli et al, 1990; Peest et al, 1990; Westin et al, 1995) and one in USA, by the South West Oncology Cooperative Group (SWOG). In addition to these studies, two other ongoing randomized trials are being conducted in Canada (Browman et al, 1994) and Australia (Joshua et al, 1994), and have been published only as abstracts.
The Italian study (Mandelli et al, 1990) This was the first published study in which IFN-~ was employed as an agent for maintaining the response already obtained with conventional therapy, rather than as an agent for inducing a response. MM patients responding to 12-monthly courses of traditional first-line induction chemotherapy were randomized to receive (N = 50) or not (N = 51) recombinant IFN-ct2b as maintenance treatment at the dose of 3 MU three times per week subcutaneously until relapse. The overall results of the study were as follows: the median duration of response (from the time of randomization to maintenance treatment) was 26 months in the patients given IFN and 14 months in the untreated patients (P = 0.0002), while the median duration of survival (from the time of randomization to maintenance therapy) was 52 months in the IFN group and 39 months in the control group ( P = 0.0526). However, among the patients who had an objective reponse to induction chemotherapy, the difference in survival was statistically significant (P = 0.0352). After 5 more years of follow-up from the inclusion of the last patient in this study, the updated results confirm that IFN-c~2b is a useful therapeutic tool in controlling the plateau phase of responding MM patients (P = 0.0002). However, despite the median survival duration for responding patients being 50.9 months in the IFN arm, compared with 36.6 months in the control arm, the difference between the two arms is no more significant using the log-rank test, while using the Wilcoxon statistical test, the difference between the two arms is marginally significant (P=0.05) (personal unpublished data).
The German study (Peest et al, 1990) In this study, 71 out of 140 MM patients with stable disease after induction chemotherapy were randomized to receive or not receive IFN-~2b as maintenance treatment. As for the relapse rate, the published results reveal no differences between the two randomized groups, the median response duration being 7 months in both groups. No data on the overall survival duration of both groups were available. However, in this study, the absence of benefit in the IFN-~-maintained group may be due to the presence of some differences in the modalities of randomization with respect to the other studies, such as: (a) the absence of a stratification for the induction
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treatment before the randomization to the maintenance arm, and (b) the shorter duration of the plateau phase, compared with the longer duration of the plateau phase of other studies.
The Swedish study (Westin et al, 1995) In this study, following the MP induction treatment, 155 out of 314 evaluable patients achieved a plateau phase, defined as response (greater than 50% reduction of the monoclonal component) lasting 4 months. Of these 155 patients in the plateau phase, 125 were randomized to receive (N = 61) or not receive (N = 64) IFN-~2b at the dose of 5 MU three times per week subcutaneously until relapse. After an average observation time from randomization of 51 months (minimum 36 months), the plateau phase was significantly prolonged in the group of patients treated with interferon (P < 0.0001). In particular, the median duration of plateau was 13.9 months in the IFN arm and 5.7 months in the control arm. However, the median survival from randomization was similar in both groups (36 versus 35 months). This well-designed study indicates that the use of IFN-c~ as maintenance treatment in MM patients responding to initial induction treatment and achieving a well defined 'plateau phase' can significantly prolong the response duration, and it therefore partially confirms the results of the Italian study.
The SWOG study (Salmon et al, 1994) Patients achieving a response, defined as 75% of myeloma mass regression, to conventional induction chemotherapies, at random assigned to treatment with VMCP/VBAP (vincristine + melphalan + cyclophosphamide + prednisone/vincristine + BCNU + Adriamycin + prednisone) or VAD (vincristine + Adriamycin + prednisone) or VMCPP/VBAPP) (VMCP + alternate day prednisone between chemotherapy cycles/VBAP + alternate day prednisone between chemotherapy cycles) were randomized to receive (N= 97) or not receive (N= 96) IFN-~2b until relapse. No differences in relapse-free or overall survival duration for patients receiving IFN have been observed. The median relapse-free duration from the start of maintenance therapy was 12 months in the IFN-~2b ann and 11 months in the control arm (P = 0.95). Moreover, median overall survival duration was 32 months in the IFN-~2b arm and 38 months in the control arm (P =0.39). Two main differences between the SWOG and the Italian and Swedish studies may be responsible for the different results observed. Firstly, in the SWOG study, the responding patients are only those with a reduction of at least 75% of myeloma mass, while in the Italian and Swedish studies the cut-off for response is a reduction of at least 50% of myeloma mass. Secondly, the patient population with stage III myeloma is greater, while the number with stage I myeloma is lower in the SWOG study. As a consequence, the proportion of cases with high-risk myeloma is higher in this study than in the Italian and Swedish studies.
ROLE OF BIOTHERAPIES IN MULTIPLE MYELOMA
823
It is therefore possible that these differences in response definition and in patient population may partially explain the negative results of this study, taking into account that encouraging results have been obtained by using IFN0~2b + dexamethazone (DEX) in those 79 patients with a lower reduction (less than 75%) of myeloma mass after induction chemotherapy, who had an overall median survival of 48 months from the start of IFN-~2b + DEX.
The Canadian study (Browman et al, 1994) In this trial, when response criteria were met, patients were randomized to IFN-~2b at a dose of 2 MU/m ~ three times per week subcutaneously until relapse (N = 85), or to a control group (N = 92). MP induction therapy was continued in both arms until the monoclonal protein had stabilized for at least 4 months; thereafter, MP was discontinued. Median progression-free survival was 16 months for IFN and 12 months for the controls, while median overall survival was 39 and 34 months for the IFN and control groups respectively. The relative risk (RR) of progression was 0.61 (95% CI 0.42-0.87; P = 0.007) and the RR for death was 0.60 (95% CI 0.38-0.95; P = 0.03), both favouring IFN-c~2b. Therefore, IFN-o~2b maintenance in this study prolongs the duration of response and overall survival of patients with MM.
The Australian study (Joshua et al, 1994) A total of 1 t 3 M M patients were randomized to receive, as induction, the combination therapy of prednisone, cyclophosphamide, Adriamycin and BCNU (PCAB), with or without IFN-o~2b at a dose of 3 MU/m 2 5 days a week subcutaneously at the commencement of the third cycle of treatment. Whereas PCAB was given for a total of 12 cycles, IFN-~2b was continued until progression. Despite the fact that the addition of IFN-~2b to PCAB during induction therapy did not produce any benefit in terms of response to treatment or achievement of the plateau phase, there was a trend for patients in the IFN-~2a arm to have a longer duration of plateau phase and overall survival than patients on the PCAB alone arm.
IFN-~ as maintenance treatment in MM patients after transplantation procedures High-dose chemotherapy (HDC) was developed to improve survival of aggressive myeloma. However, even though HDC is capable of giving a high response rate, it is associated with severe life-threatening toxicities that can be reduced by autologous bone marrow transplantation (ABMT) or peripheral stem cell infusion (PSCI). As a consequence, an increasing number of patients with MM ale now treated with HDC followed by ABMT or PSCI. However, relapse remains a major problem, so in an attempt to improve the response and survival durations of these patients, a number of investigators have begun to use 1FN-~ as maintenance treatment following HDC and ABMT or PSCI in myeloma. Attal et al were among the first investigators who adopted this type of
824
G . A V V I S A T I ET A L
therapy in previously untreated aggressive myeloma. They have recently published the results of a trial initiated to determine the feasibility and efficacy of three-phase treatment, consisting of an induction chemotherapy followed by high-dose melphalan and total body irradiation, supported by unpurged ABMT and IFN-o~ maintenance treatment. After a median followup of 24 months after diagnosis and 15.5 months after ABMT, only one of the 15 patients who had obtained a complete response (CR) has relapsed, while among the 15 patients who did not obtain a CR, there were 7 relapses (Attal et al, 1992). The results of Attal et al have been very recently confirmed in a randomized study by English investigators (Cunningham et al, 1993). In this study, 84 patients with myeloma were randomized to receive maintenance IFN-c~2b, 3 MU/m 2 subcutaneously three times weekly, or no treatment following induction therapy with C-VAMP (cyclophosphamide, vincristine, Adriamycin and methylprednisolone), consolidated with highdose melphalan (HDM) 200 mg/m2 and unpurged ABMT. At a median follow-up of 24 months, median progression-free survival from high dose melphalan (HDM) was 27 months in the control group and 39 months in the IFN-o~2b group (P < 0.025). For the 62 patients who achieved CR with HDM, there was a significant prolongation of remission (P < 0.01), and 53% of these patients who received IFN-o~2b have remained in remission 4 years after treatment. However, for partial response and non-responders to HDM, there was no significant prolongation of progression-free survival. Overall survival was also significantly longer for IFN-~x2b group, with 1 death, compared with 6 deaths in the control group (P < 0.05). The results obtained in these two studies suggest that the small residual tumour mass of patients achieving CR after ABMT could be higly sensitive to IFN-o~ maintenance treatment. As far as IFN-I3 and IFN-7 are concerned, to date there are only a few negative published reports in which these types of IFN have been used as salvage treatment, with an overall response rate of less than 5%. Therefore, it does not seem at present that 13and 7 IFNs used alone may have a role in MM. However, experimental reports indicate that, at least for IFN-7, there may be a potential therapeutic use in MM, considering that this cytokine is capable of inhibiting either the myeloma cell proliferation, by blocking IL6-receptor expression (Portier et al, 1993) or the cytokine-mediated bone resorption, one of the major clinical problems in MM. ERYTHROPOIETIN
Erythropoietin (EPO) is a glycoprotein hormone normally produced by the peritubular cells of the kidney in response to tissue hypoxia (Koury et al, 1988; Lacombe et al, 1988). It has its predominant effect on the committed erythroid cells, colony-forming unit erythroids (CFU-E), promoting their proliferation and differentiation into proerythroblasts (Eaves and Eaves, 1978). To exert these functions, EPO must bind to specific cell surface EPO
R O L E OF B I O T H E R A P I E S IN M U L T I P L E M Y E L O M A
825
receptors; however, the molecular events that are activated after binding of EPO to these receptors are still unknown (Krantz, 1991). EPO in clinical settings was first used in patients undergoing dialysis who had anaemia owing to chronic renal failure. These patients showed a consistent and sustained beneficial effect on haematocrit, reticulocyte count and transfusion requirements. Extending these treatments to patients with renal failure not yet requiring dialysis, the same results were obtained (Lim et al, 1989). Since then, EPO has been used not only in patients with anaemia due to renal failure, but also in patients with other types of chronic anaemia, such as those secondary to cancer. Therapeutic use of erythropoietin in MM In patients with MM, anaemia is a common complication, with multifactorial pathogenic mechanisms, including extensive bone marrow involvement by tumour cells, cytokine production, renal failure and prior cytotoxic chemotherapy. Therefore, because it is often characterized as the anaemia of chronic disease, it seemed appropriate to use EPO for reducing either the symptoms due to anaemia or the number of packed red cell transfusions needed to ameliorate the low haemoglobin levels. The first study dealing with the use of EPO in the treatment of the anaemia associated with MM was published in 1990 (Ludwig et al, 1990). EPO was administered subcutaneously three times a week at an initial dose of 150 U/kg body weight to 13 patients with advanced MM, all previously treated with chemotherapy + local radiotherapy, for a median period of 30 weeks. If no response was observed within 3 weeks, the dose was increased to 200 U/kg body weight; if after a further 3 weeks of treatment there was no substantial response, the dose was increased by 50 U/kg. If a response occurred, the dose was reduced to maintain the haemoglobin levels between 12 and 14 g/dl. Eleven patients (85%) responded to EPO, obtaining a steady increase in haemoglobin levels of at least 2 g/dl without any adverse side-effects and with excellent tolerance of the treatment. Moreover, while only some of the patients had an improvement in performance status, all the 11 responding patients had experienced subjective improvement in their quality of life. A second study on the use of EPO in MM, published by Barlogie (1993) showed that patients with a relatively high level of endogenous EPO (> 100U/I) had late responses or failed to respond. On the contrary, a beneficial effect of EPO therapy was observed in those patients with anaemia associated to inappropriately low endogenous EPO levels. Both these studies provide clinical evidences that EPO is a promising and effective therapeutic tool for the management of MM-associated anaemia. THE F U T U R E The next years will better clarify whether, and to what extent, the use of biotherapies will increase in MM. So far, their potential role has been only
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G. AVVISATI ET AL
partially explored, and interventions directed at manipulating the complex cytokine networks pertinent to the pathogenesis of MM are an exciting new area of investigation, which might be the cornerstone of future treatment of this disease. The mounting evidence that IL-1 [3 and TNF-~, along with IL6, play a role in myeloma cell proliferation and in mediating bone destruction (Garrett et al, 1987; Carter et al, 1990) provides the biological background for using anti-IL-1 and anti-TNF MoAbs as future possible interventions in MM patients. Moreover, recent data indicate that retinoic acid can be beneficial in MM because it is able to significantly inhibit human myeloma cell growth in vitro (Palumbo et al, 1995) by downregulating IL-6 receptors and interfering with IL-6 signal transduction (Sidell et al, 1991; Ogata et al, 1994),
SUMMARY During the last decade, the availability of large numbers of cytokines and growth factors has greatly favoured the use of biotherapies in several haematological diseases. For MM, the majority of clinical studies have dealt with the use of IFN-~. From these studies it appears that IFN-~ has a definite role in the treatment of MM especially in the setting of minimal residual disease, as maintenance therapy after response to conventional therapies or HDC followed by BMT procedures or PBSCI. Data on the use of EPO have consistently demonstrated the role of this growth factor in ameliorating the grade of anaemia as well as the quality of life of those MM patients whose disease is complicated by the presence of a severe or moderate anemia. Despite the large amount of experimental data indicating a role for IL-2 and IL-6 in controlling tumour growth, there are only a few clinical studies dealing with their use in MM. From these, it appears that IL-2 and anti-IL6 antibodies should be further investigated as therapeutic tools useful in maintaining responses, because results show that they arrest tumour progression rather than aid, tumour regression. Finally, in the next years, there will be a wider diffusion of biotherapies in MM that should take into account the roles that IL-113 and TNFo~ play in myeloma cell proliferation and bone destruction and the finding that retinoic acid is capable of inhibiting the growth of human myeloma cells in vitro through modulation of IL-6 and its receptor.
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