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Emerging Biological Insights and Novel Treatment Strategies in Primary Mediastinal Large B-Cell Lymphoma
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Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma Kieron Dunleavy, Christian Steidl
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S0037-1963(15)00003-7 http://dx.doi.org/10.1053/j.seminhematol.2015.01.002 YSHEM50801
To appear in: Semin Hematol
Cite this article as: Kieron Dunleavy, Christian Steidl, Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma, Semin Hematol , http://dx.doi.org/10.1053/j.seminhematol.2015.01.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
January 6, 2015
Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma
Kieron Dunleavy1 and Christian Steidl2
1 2
Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA Centre for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, Canada
Address correspondence: Kieron Dunleavy MD, National Cancer Institute, Building 10, Room 12N226, 10 Center Drive, Bethesda, MD 20892, USA. Email: [email protected] Word count: Abstract: 148; Manuscript: 3124
ABSTRACT While primary mediastinal large B-cell lymphoma (PMBCL) is considered to be a subtype of diffuse large B-cell lymphoma (DLBCL), it is a distinct clinicopathologic entity, with clinical and biological features closely resembling nodular sclerosing Hodgkin lymphoma (NSHL). Recent studies have highlighted the shared biology of these two entities and identified novel critical pathways of lymphomagenesis including the presence of distinct mutations. Mediastinal grey zone lymphomas (MGZL) with features in between PMBCL and NSHL have been described as the missing link between the two parent entities. While the standard therapeutic approach to PMBCL has been immunochemotherapy followed by mediastinal radiation, strategies that obviate the need for radiation and thus eliminate its long-term toxicities have recently been developed. The identification of novel targets in PMBCL and MGZL pave the way for the testing of agents such as small molecule inhibitors of janus kinase pathways and immune checkpoint inhibitors. Future directions in these diseases should focus on combining effective novel agents with immunochemotherapy platforms.
INTRODUCTION Primary mediastinal B-cell lymphoma (PMBCL) constitutes 10% of all diffuse large B-cell lymphomas (DLBCL). It has demographic, clinical and biological characteristics that are distinct from the other subtypes of DLBCL (germinal center B-cell like (GCB) and activated B-cell like (ABC)) and more closely resembling those of nodular sclerosing Hodgkin lymphoma (NSHL) arising in the mediastinum. Gene expression profiling (GEP) studies have demonstrated that PMBCL and NSHL share a third of their genes and recent work has identified common driver mutations in both diseases(1, 2). Mediastinal grey zone lymphomas (MGZL) are much less frequently encountered than PMBCL and studies, albeit few, that have investigated their biological features, suggest that they represent a unique molecular entity(3). There has been much controversy as to what the optimal management of PMBCL patients should be owing to the rarity of the disease and lack of prospective studies. While most standard approaches have included rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) chemotherapy followed by mediastinal radiation, recent increased dose intensity approaches have eliminated the routine need for mediastinal radiation while maintaining high cure rates. Regarding future investigation, these diseases harbor several interesting targetable pathways that could be amenable to specific inhibitors of NF-kappa B and janus kinase pathways as well as immune checkpoint blockade. BIOLOGICAL INSIGHTS Pathogenic hallmarks PMBCL is recognized as a distinct entity in the 2008 WHO classification of Haematopoietic and Lymphoid tissues owing to the distinct gene expression profile, immunophenotype and clinical presentation that is markedly different from activated B cell (ABC)- and germinal center B cell (GCB)-type DLBCL.(4) Although a pathological and clinical spectrum including ABC/GCB-type DLBCL, PMBCL, MGZL, NS-HL has been recognized for a long time, pivotal gene expression profiling data and more recent genomic data define PMBCL as a unique lymphoid cancer characterized by molecular and clinical features that are shared with the related entities of the spectrum.(5) Summarizing the knowledge about genetic alterations, pathway pertubations and expression phenotypes, the most prominent PMBCL molecular hallmarks include activation of the JAK-STAT and NF B pathways, and avoiding immune destruction.(6) In the most recent past, high-resolution genomics approaches have added texture to our knowledge about these pathways and provided a number of genetic events that underlie phenotypic changes including point mutations, genomic rearrangements and copy number changes.(7-9) Interestingly, most of these genetic changes are present across the above mentioned pathobiological spectrum providing additional evidence for the molecular relatedness of these diseases. With the emergence of novel treatments targeting JAK-STAT signaling and the crosstalk of malignant cells with cells in the microenvironment via immune checkpoint blockade, a focused review of the JAK-STAT pathway, acquired immune privilege and related biomarkers is warranted in PMBCL. JAK-STAT pathway Activation of JAK-STAT signaling in PMBCL is a shared feature with CHL and well supported by gene expression profiling experiments and studies investigating the functional consequences of specific somatic gene mutations found in PMBCL patients and derived cell lines. In normal B cells the JAK-STAT pathway is activated by interleukin receptor subunit ligation by various interleukins or interferons, heterodimerization and phosphorylation of subunits and subsequent (auto)-phosphorylation of Janus kinases (JAKs) and STAT molecules that regulate gene transcription.(10) In PMBCL, JAK-STAT signaling is likely the summation of paracrine IL13 receptor-mediated signaling and constitutive activation by various somatic gene mutations in pathway molecules.(11) As evidence of intact paracrine signaling, IL13 stimulation led to increased and reversible levels of phosphorylated STAT5 in PMBCL-derived cell lines Med-B1.(12) Moreover, IL4 or IL13 stimulation of the PMBCL-derived cell line KARPAS 1106P induced an inflammatory phenotype reminiscent of CHL.(13) In
addition, amplification of JAK2, deletions or inactivating mutations of the negative regulators SOCS1 and PTPN1, and mutations in STAT6 are reported to result in constitutive pathway activation. As a result of these pathway perturbations, phosphorylated STAT6 has been suggested as a reliable marker to distinguish PMBCL from other large cell lymphoma subtypes.(11) However, patterns of concurrent or mutational exclusive pathway hits as well as the relative contributions of paracrine vs constitutive activation needs to be determined in future studies with implications for potential therapeutic targeting of the pathway. Gains and amplifications of the JAK2 locus on chromosome 9p were one of the first descriptions of somatic genetic alterations of JAK-STAT pathway members.(9, 14) Typically, the minimally amplified region contains multiple genes, including JAK2, the programmed death ligands CD274 (PDL1), PDCD1LG2 (PDL2) and JMJD2C(15), that act synergistically in the pathogenesis of PMBCL.(6) Although, 9p amplifications are present in more than half of all PMBCLs, there is now evidence that somatic point mutations of SOCS1 are at least as frequent. Melzner et al found point mutations including biallelic mutations in 45% of cases, and these high frequencies were confirmed and extended by whole transcriptome analysis (RNA-seq) identifying single nucleotide variants and indels in 7 of 7 clinical PMBCL cases.(16) Moreover, RNA-seq confirmed previously identified SOCS1 mutations in the cell lines Med-B1 and KARPAS 1106P.(7) SOCS1 mutations were also found in CHL and nodular lymphocyte predominant Hodgkin lymphoma, supporting the concept of shared genetic features across the pathological spectrum.(17, 18) In functional analyses inactivating SOCS1 mutations were shown to abrogate SOCS box function leading to hyperphosphorylation of JAK2 and STAT5.(16) As such SOCS1 acts a classical tumor suppressor controlling downstream signaling. Recently, mutations in an additional negative regulator of JAK-STAT signaling have been discovered through next generation sequencing. Using whole genome, transcriptome and targeted re-sequencing, Gunawardana and colleagues identified coding sequence mutations in the PTPN1 gene in 22% of PMCBL and 20% of CHL cases consisting of nonsense, missense and frameshift mutations.(7) PTPN1 encodes PTP1B, a non-receptor member of the superfamily of protein tyrosine phosphatases that was found to be a negative regulator of IL-4-induced STAT6 signaling.(19) The observed PTPN1 nonsense and missense mutations were confirmed as deleterious by partial or complete reduction of phosphatase activity of PTPN1 leading to sustained phosporylation of STAT3, STAT5 and STAT6. While JAK2 amplification, SOCS1 and PTPN1 all result in increased phosphorylation of STATs, there is also strong evidence that direct point mutations in STATs, specifically STAT6, might alter transcriptional programs and thereby contribute to the pathogenesis of PMBCL. Recurrent somatic mutations in STAT6 were reported in 36% of PMBCL cases (20). In summary, the frequent somatic mutations in the pathway and related constitutive pathway activation pinpoint JAK-STAT signaling as a very promising drug target. Acquired immune privilege The crosstalk of malignant cells with the cells in the lymphoma microenvironment is well recognized in the literature and the specific composition of the microenvironment represents a characteristic feature of many lymphoma subtypes.(21) In PMBCL, this tumor microenvironment is highly variable and reflects the pathological relatedness to the above described entities of the spectrum with resemblance to CHL on one end of the spectrum (very diverse cell types, relatively low abundance of malignant cells) and DLBCL on the other end (uniform appearance with high tumor content and sheets of neoplastic cells).(4) Importantly, from a biology point of view, the diversity of lymphoma-associated microenvironments is very likely the result of variable immune cell crosstalk between malignant and non-malignant cells that is selected for during disease progression. In PMBCL, the tumor hallmark of “immune privilege” is mainly supported by downregulation of MHC class I and II molecules and overexpression of programmed death ligands leading to reduced immunogenicity and T cell anergy. Recently, the genetic basis of these expression phenotypes has been partly elucidated highlighting the acquired nature of this oncogenic mechanism and suggesting therapeutic interference with acquired immune privilege as an effective approach in a subset of patients. Loss of major histocompatibility (MHC) molecules, in particular MHC class II has been described as a common feature in PMBCL.(22, 23) First indications that genomic changes underlie these expression changes came from microsatellite analysis and copy number analysis identifying allelic imbalances on chromosome 6p
harboring the MHC class I and II genes, although the number of affected cases was low.(9, 22) Interestingly, similar genomic imbalances are frequently found in cases of immune-privilege site (IP)-DLBCL (primary testicular DLBCL and primary central nervous system lymphoma) suggesting a possible genetic link between PMBCL and IP-DLBCL. Whole transcriptome sequencing analysis of CHL cell lines and subsequent screening by fluorescence in-situ hybridization (FISH) revealed recurrent chromosomal rearrangement of the CIITA locus on chromosome 16p.(24) CIITA encoded for the master transcriptional regulator of MHC class II expression and a tight correlation of CIITA and MHC class II expression has been observed previously in PMBCL.(23) CIITA rearrangements result in gene fusions with various gene partners, of which one specific fusion (CIITA-FLJ27352) was shown to act in a dominant negative fashion to reduce MHC class II expression in functional analyses.(24) Additional study is needed to establish CIITA loss of function mutations as a bona-fide mechanism in the pathogenesis of PMBCL. Increased expression of programmed death ligand 2 (encoded by PDCD1LG2 / PDL2) was discovered in early gene expression profiling studies in which PDL2 was part of the gene signature distinguishing PMBCL from ABC- and GCB-type DLBCL(1, 25). Integrative analysis of copy number and gene expression data in subsequent studies confirmed that PDL2 and its close paralog PDL1 (CD274) are both critical target genes of 9p gains and amplifications that are detectable in more than half of PMBCL cases.(8, 26) Moreover, recurrent genomic rearrangements involving the 9p locus were discovered by next generation sequencing and subsequent FISH analysis in 20% of PMBCL cases resulting in PDL1 and PDL2 gene fusions (8, 24). These findings confirm these genes as the critically deregulated genes on chromosome 9p24 and suggest upregulation of programmed death ligands and expression of PDL1- and PDL2-containing gene chimera as novel pathogenic events. Interestingly, PDL1 and PDL2 expression was found to be highest in the rearranged cases compared to cases with gains or amplifications (8). Moreover, ectopic expression of a CIITA-PDL2 gene fusion in DLBCL cell line U2932 inactivated JURKAT T cells in a co-culture system, and this inactivation could be reversed by blockade of the PD-1 receptor or ligand. These data demonstrate the functional consequence of these gene fusions for tumor microenvironment crosstalk and strongly suggest that blockade of the PD-1 axis could reverse acquired immune privilege. Co-amplification of JAK2 with the programmed death ligand locus on chromosome 9p24 suggests that JAKSTAT signaling and acquired immune privilege synergize in PMBCL lymphomagenesis. While it is intuitive that enhanced survival signaling and escape from immune destruction both independently contribute to tumor progression, a direct link between both pathways could be established by a PDL1 promoter study demonstrating STAT-dependent expression of PDL1.(26) Thus, combined inhibition of JAK-STAT and immune checkpoints seems promising in light of these findings. MANAGEMENT OF PMBCL AND MGZL Due to the rarity of PMBCL and the fact that it is a recently described entity, there are very few studies and no randomized comparisons of strategies to guide up-front therapy selection (table 1). It is a distinct clinicopathologic entity and should be approached as such therapeutically. Early trials that were principally led by Italian groups suggested that radiation was a critical component of curative therapy and today, consolidative mediastinal radiation remains part of standard therapy for a significant proportion of patients(27, 28). Given the young age and female gender of most patients with this disease, radiation leads to a long-term risk of breast cancer and other malignancies as well as ischemic heart disease and the high frequency of these complications has now been well documented in many childhood and adolescent cancer survivorship studies(29). Though some advocate that these complications are reduced with lower doses and more focused radiation fields, this has not been clearly demonstrated and may only be properly assessed with time and longer follow-up(30). It is therefore critical to develop strategies that remove the need for routine mediastinal radiation if they can maintain high cure rates in PMBCL. While R-CHOP has been extensively studied in other subtypes of DLBCL, the published experience in PMBCL is limited to retrospective studies or retrospective evaluations of prospective studies and in these, the
majority of patients received radiation therapy(31-33). The largest evaluation to date was a subgroup analysis of the randomized MabThera International Trial (MInT) where most patients received R-CHOP(31). Although the 3-year event-free survival was 78%, 73% received pre-planned radiation and adding radiation improved remission rates. It is important to note that this analysis was confined to patients with an age-adjusted international prognostic index (IPI) score of 0-1 and therefore does not reflect the entire clinical spectrum of the disease. In another retrospective analysis, 58 PMBCL patients had a PFS of 68% at 5 years after R-CHOP with 77% of responders receiving radiation(32). There was a high rate of primary induction failure (21%) and patients with higher IPI scores and disease that was not limited to the mediastinum fared significantly worse. Is it possible to use end of therapy FDGPET to guide who needs radiation? Ongoing studies in PMBCL, such as a large randomized IELSG multicenter study, are investigating if an end of therapy negative FDG-PET can identify patients who do not require radiation but with respect to patients who have received R-CHOP, a British Columbia study demonstrated that a sizeable portion of (end of therapy) FDG-PET negative cases subsequently relapsed(34). Due to the observation from retrospective studies that dose intensity has been important in PMBCL, an NCI study investigated dose adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin and rituximab (DA-EPOCH-R) without radiation in all clinical risk groups of PMBCL and in 51 patients, EFS and OS were 93% and 97% respectively at 5 years(35). In addition, 16 PMBCL patients who received the regimen at Stanford had an EFS and OS of 100% without radiation and the approach is under investigation in other studies including pediatric groups where an early report suggested high efficacy without the need for radiation(36). Regarding the role of FDG-PET in the management of PMBCL, it is important to consider that an end of treatment FDG-PET has a low positive predictive value in contrast to the high clinical accuracy of the technique in other aggressive lymphomas(28, 35). Therefore, alternative, more-specific imaging technologies should be evaluated in this disease in the future. MGZLs, with histological and immunophenotypical features that are transitional between PMBCL and NSHL were only recently identified and are exceedingly rare. Therefore, they have not been well studied. Previously, these tumors were likely identified as “anaplastic large-cell lymphoma Hodgkin-like” and this entity was reported to have a poor outcome with chemotherapy(37). The indeterminate pathobiology of MGZL has led to uncertainty about its optimal therapeutic approach(38). A recent prospective study looked at the outcome of MGZL following treatment with DA-EPOCH-R and reported an inferior survival compared to that of PMBCL, although both patient groups had similar clinical characteristics. (EFS and OS of 62% and 74% versus 93% and 97% for PMBCL)(39). Studies looking at the molecular characteristics of MGZL are ongoing and are attempting to explain the biological basis for the inferior outcome of this lymphoma. NOVEL AGENTS AND EMERGING STRATEGIES Due to significant strides over recent years in elucidating the molecular biology of PMBCL and MGZL, several new targets have now been recognized and this paves the way for testing novel agents in these diseases (figure 1). The close clinical and biological relationship of these lymphomas to HL is important to consider as new agents that are effective in HL may also have good activity in PMBCL and MGZL. Brentuximab vedotin is an antibody drug conjugate consisting of a chimeric anti-CD30 monoclonal antibody on which the microtubule inhibitor monomethyl auristatin E (MMAE) is attached via a valine citrulline linker(40). Following its binding to CD30, brentuximab vedotin is internalized and MMAE released. This agent induces responses in a high percentage of cases of relapsed and refractory Hodgkin lymphoma and is currently being investigated in upfront therapy(41, 42). As CD30 is variably expressed in PMBCL and MGZL, brentuximab is a rational agent to study in these diseases and is currently under investigation in combination with R-CHOP in newly diagnosed PMBCL and MGZL. 70% of cases of PMBCL have amplification on a region of chromosome 9p24 that constitutes critical targets such as the PD1 ligands programmed cell death ligand 1 (PD-L1) and PD-L2 and janus kinase 2 (JAK2)(14, 15, 26). The PD-1 checkpoint pathway appears to facilitate evasion of the anti-tumor immune response and immune
checkpoint inhibitors have demonstrated exciting activity in a wide range of cancers such as melanoma(43). AntiPD1 activity likely results from both direct anti-tumor effects related to binding to PD-1 or PD-L1 and also restoration of the immune anti-tumor response by enhancing T-cell and NK-cell function(44). Pidilizumab is a humanized monoclonal antibody that binds to PD-1 - in one phase 2 trial of the agent in relapsed aggressive B-cell lymphoma, patients with primary mediastinal B-cell lymphoma were included but it is difficult to interpret the activity of the agent as the primary end-point of the study was to prevent disease relapse and the number of patients with PMBCL was small(45). Nivolumab is another fully humanized IgG-4 blocking antibody and is currently under investigation in relapsed and refractory Hodgkin lymphoma – in an early report of its activity in this disease population, an objective response was reported in 87% of patients including 17% with a complete response(46). Several other immune checkpoint inhibitors are in development and given their activity in HL, they represent an interesting and promising class of agents to study in PMBCL and MGZL. The Janus kinases (JAKs) that mediate cytokine receptor signaling play a role in many hematological malignancies. JAK2 signaling is important in both PMBCL and HL and selective JAK2 inhibition has been shown to specifically decrease PMBCL and HL growth in vitro and in vivo (47). The JAK2/FLT3 inhibitor, SB1518, was tested in relapsed or refractory HL and NHL and demonstrated encouraging activity but there were not enough cases of PMBCL to specifically evaluate its activity in that group(48). Several other JAK inhibitors are in clinical development including ruxolitinib, an oral JAK1/2 inhibitor, that is FDA approved for myelofibrosis. Other interesting strategies for PMBCL include using genetically modified T-cells – a recent study that treated patients with autologous T-cells expressing an anti-CD19 chimeric antigen receptor (CAR) reported a high complete remission rate in DLBCL and indolent lymphomas(49). Most cases of PMBCL have expression of CD19 and two patients who had received several lines of previous treatment had complete responses lasting beyond 12 months with this approach. CONCLUSIONS PMBCL and MGZL are intriguing mediastinal lymphomas and significant progress has been made recently in elucidating their biological characteristics. Though recognized as a subtype of DLBCL, PMBCL is cliniopathologically distinct from other DLBCLs and should be approached differently, therapeutically. While radiation therapy has historically been a standard treatment modality for PMBCL, novel approaches obviate its need and importantly, eliminate its long-term risks. Insights into the biology of these diseases have paved the way for investigating small molecule inhibitors and novel immunotherapeutic approaches in the future. Authorship CS and KD contributed to the writing of the manuscript and approved the final version. CS and KD have no relevant conflicts of interest. KD receives funding from the Intramural Program of the National Cancer Institute. C.S. is supported by a New Investigator Award from the Canadian Institutes of Health Research (CIHR) and a Career Investigator Award from the Michael Smith Foundation for Health Research.
References 1. Rosenwald A, Wright G, Leroy K, Yu X, Gaulard P, Gascoyne RD, et al. Molecular diagnosis of primary mediastinal B cell lymphoma identifies a clinically favorable subgroup of diffuse large B cell lymphoma related to Hodgkin lymphoma. J Exp Med. 2003;198(6):851-62. 2. Gunawardana J, Chan FC, Telenius A, Woolcock B, Kridel R, Tan KL, et al. Recurrent somatic mutations of PTPN1 in primary mediastinal B cell lymphoma and Hodgkin lymphoma. Nature genetics. 2014;46(4):329-35. Epub 2014/02/18. 3. Eberle FC, Salaverria I, Steidl C, Summers TA, Jr., Pittaluga S, Neriah SB, et al. Gray zone lymphoma: chromosomal aberrations with immunophenotypic and clinical correlations. Mod Pathol. 2011;24(12):1586-97. Epub 2011/08/09. 4. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al., editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France: IARC 2008. 5. Grant C, Dunleavy K, Eberle FC, Pittaluga S, Wilson WH, Jaffe ES. Primary mediastinal large B-cell lymphoma, classic Hodgkin lymphoma presenting in the mediastinum, and mediastinal gray zone lymphoma: what is the oncologist to do? Curr Hematol Malig Rep. 2011;6(3):157-63. Epub 2011/05/19. 6. Steidl C, Gascoyne RD. The molecular pathogenesis of primary mediastinal large B-cell lymphoma. Blood. 2011;118(10):2659-69. Epub 2011/06/28. 7. Gunawardana J, Chan FC, Telenius A, Woolcock B, Kridel R, Tan KL, et al. Recurrent somatic mutations of PTPN1 in primary mediastinal B cell lymphoma and Hodgkin lymphoma. Nat Genet. 2014. Epub 2014/02/18. 8. Twa DDW, Chan FC, Ben-Neriah S, Woolcock BW, Tan KL, Slack GW, et al. Genomic Rearrangements Involving Programmed Death Ligands Are Recurrent In Primary Mediastinal Large B-Cell Lymphoma. Blood. 2013;122(21):635. 9. Wessendorf S, Barth TF, Viardot A, Mueller A, Kestler HA, Kohlhammer H, et al. Further delineation of chromosomal consensus regions in primary mediastinal B-cell lymphomas: an analysis of 37 tumor samples using high-resolution genomic profiling (array-CGH). Leukemia. 2007;21(12):2463-9. 10. Darnell JE, Jr., Kerr IM, Stark GR. Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins. Science. 1994;264(5164):1415-21. Epub 1994/06/03. 11. Guiter C, Dusanter-Fourt I, Copie-Bergman C, Boulland ML, Le Gouvello S, Gaulard P, et al. Constitutive STAT6 activation in primary mediastinal large B-cell lymphoma. Blood. 2004;104(2):543-9. Epub 2004/03/27. 12. Raia V, Schilling M, Bohm M, Hahn B, Kowarsch A, Raue A, et al. Dynamic mathematical modeling of IL13-induced signaling in Hodgkin and primary mediastinal B-cell lymphoma allows prediction of therapeutic targets. Cancer Res. 2011;71(3):693-704. Epub 2010/12/04. 13. Andersson E, Schain F, Sjoberg J, Bjorkholm M, Claesson HE. Interleukin-13 stimulation of the mediastinal B-cell lymphoma cell line Karpas-1106P induces a phenotype resembling the Hodgkin lymphoma cell line L1236. Exp Hematol. 2010;38(2):116-23. Epub 2009/11/26. 14. Joos S, Otano-Joos MI, Ziegler S, Bruderlein S, du Manoir S, Bentz M, et al. Primary mediastinal (thymic) B-cell lymphoma is characterized by gains of chromosomal material including 9p and amplification of the REL gene. Blood. 1996;87(4):1571-8. Epub 1996/02/15. 15. Rui L, Emre NC, Kruhlak MJ, Chung HJ, Steidl C, Slack G, et al. Cooperative epigenetic modulation by cancer amplicon genes. Cancer Cell. 2010;18(6):590-605. Epub 2010/12/16. 16. Melzner I, Bucur AJ, Bruderlein S, Dorsch K, Hasel C, Barth TF, et al. Biallelic mutation of SOCS-1 impairs JAK2 degradation and sustains phospho-JAK2 action in the MedB-1 mediastinal lymphoma line. Blood. 2005;105(6):2535-42. Epub 2004/12/02. 17. Mottok A, Renne C, Willenbrock K, Hansmann ML, Brauninger A. Somatic hypermutation of SOCS1 in lymphocyte-predominant Hodgkin lymphoma is accompanied by high JAK2 expression and activation of STAT6. Blood. 2007;110(9):3387-90. Epub 2007/07/27.
18. Weniger MA, Melzner I, Menz CK, Wegener S, Bucur AJ, Dorsch K, et al. Mutations of the tumor suppressor gene SOCS-1 in classical Hodgkin lymphoma are frequent and associated with nuclear phospho-STAT5 accumulation. Oncogene. 2006;25(18):2679-84. 19. Lu X, Malumbres R, Shields B, Jiang X, Sarosiek KA, Natkunam Y, et al. PTP1B is a negative regulator of interleukin 4-induced STAT6 signaling. Blood. 2008;112(10):4098-108. Epub 2008/08/22. 20. Ritz O, Guiter C, Castellano F, Dorsch K, Melzner J, Jais JP, et al. Recurrent mutations of the STAT6 DNA binding domain in primary mediastinal B-cell lymphoma. Blood. 2009;114(6):1236-42. Epub 2009/05/09. 21. Scott DW, Gascoyne RD. The tumour microenvironment in B cell lymphomas. Nat Rev Cancer. 2014;14(8):517-34. Epub 2014/07/11. 22. Rigaud G, Moore PS, Taruscio D, Scardoni M, Montresor M, Menestrina F, et al. Alteration of chromosome arm 6p is characteristic of primary mediastinal B-cell lymphoma, as identified by genome-wide allelotyping. Genes Chromosomes Cancer. 2001;31(2):191-5. Epub 2001/04/25. 23. Roberts RA, Wright G, Rosenwald AR, Jaramillo MA, Grogan TM, Miller TP, et al. Loss of major histocompatibility class II gene and protein expression in primary mediastinal large B-cell lymphoma is highly coordinated and related to poor patient survival. Blood. 2006;108(1):311-8. 24. Steidl C, Shah SP, Woolcock BW, Rui L, Kawahara M, Farinha P, et al. MHC class II transactivator CIITA is a recurrent gene fusion partner in lymphoid cancers. Nature. 2011;471(7338):377-81. Epub 2011/03/04. 25. Savage KJ, Monti S, Kutok JL, Cattoretti G, Neuberg D, De Leval L, et al. The molecular signature of mediastinal large B-cell lymphoma differs from that of other diffuse large B-cell lymphomas and shares features with classical Hodgkin lymphoma. Blood. 2003;102(12):3871-9. 26. Green MR, Monti S, Rodig SJ, Juszczynski P, Currie T, O'Donnell E, et al. Integrative analysis reveals selective 9p24.1 amplification, increased PD-1 ligand expression, and further induction via JAK2 in nodular sclerosing Hodgkin lymphoma and primary mediastinal large B-cell lymphoma. Blood. 2010;116(17):3268-77. Epub 2010/07/16. 27. Zinzani PL, Martelli M, Bertini M, Gianni AM, Devizzi L, Federico M, et al. Induction chemotherapy strategies for primary mediastinal large B-cell lymphoma with sclerosis: a retrospective multinational study on 426 previously untreated patients. Haematologica. 2002;87(12):1258-64. Epub 2002/12/24. 28. Martelli M, Ceriani L, Zucca E, Zinzani PL, Ferreri AJ, Vitolo U, et al. [18F]Fluorodeoxyglucose Positron Emission Tomography Predicts Survival After Chemoimmunotherapy for Primary Mediastinal Large B-Cell Lymphoma: Results of the International Extranodal Lymphoma Study Group IELSG-26 Study. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2014. Epub 2014/05/07. 29. Castellino SM, Geiger AM, Mertens AC, Leisenring WM, Tooze JA, Goodman P, et al. Morbidity and mortality in long-term survivors of Hodgkin lymphoma: a report from the Childhood Cancer Survivor Study. Blood. 2011;117(6):1806-16. Epub 2010/11/03. 30. O'Brien MM, Donaldson SS, Balise RR, Whittemore AS, Link MP. Second malignant neoplasms in survivors of pediatric Hodgkin's lymphoma treated with low-dose radiation and chemotherapy. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2010;28(7):1232-9. Epub 2010/02/04. 31. Rieger M, Osterborg A, Pettengell R, White D, Gill D, Walewski J, et al. Primary mediastinal B-cell lymphoma treated with CHOP-like chemotherapy with or without rituximab: results of the Mabthera International Trial Group study. Ann Oncol. 2011;22(3):664-70. Epub 2010/08/21. 32. Soumerai JD, Hellmann MD, Feng Y, Sohani AR, Toomey CE, Barnes JA, et al. Treatment of primary mediastinal B-cell lymphoma with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone is associated with a high rate of primary refractory disease. Leuk Lymphoma. 2014;55(3):538-43. Epub 2013/06/06. 33. Savage KJ, Al-Rajhi N, Voss N, Paltiel C, Klasa R, Gascoyne RD, et al. Favorable outcome of primary mediastinal large B-cell lymphoma in a single institution: the British Columbia experience. Ann Oncol. 2006;17(1):123-30. Epub 2005/10/21. 34. Savage KJ, Yenson PR, Shenkier T, Klasa R, Villa D, Goktepe O, et al. The Outcome of Primary Mediastinal Large B-Cell Lymphoma (PMBCL) in the R-CHOP Treatment Era. Blood (ASH Annual Meeting Abstracts) 2012 120: Abstract 303.
35. Dunleavy K, Pittaluga S, Maeda LS, Advani R, Chen CC, Hessler J, et al. Dose-adjusted EPOCH-rituximab therapy in primary mediastinal B-cell lymphoma. N Engl J Med. 2013;368(15):1408-16. Epub 2013/04/12. 36. Woessmann W, Lisfeld J, Burkhardt B. Therapy in primary mediastinal B-cell lymphoma. N Engl J Med. 2013;369(3):282. Epub 2013/07/19. 37. Cazals-Hatem D, Andre M, Mounier N, Copin MC, Divine M, Berger F, et al. Pathologic and clinical features of 77 Hodgkin's lymphoma patients treated in a lymphoma protocol (LNH87): a GELA study. Am J Surg Pathol. 2001;25(3):297-306. Epub 2001/02/27. 38. Dunleavy K, Grant C, Eberle FC, Pittaluga S, Jaffe ES, Wilson WH. Gray zone lymphoma: better treated like hodgkin lymphoma or mediastinal large B-cell lymphoma? Current hematologic malignancy reports. 2012;7(3):241-7. Epub 2012/07/27. 39. Wilson WH, Pittaluga S, Nicolae A, Camphausen K, Shovlin M, Steinberg SM, et al. A prospective study of mediastinal gray zone lymphoma. Blood. 2014. Epub 2014/07/16. 40. Provencio M, Sanchez A, Sanchez-Beato M. New drugs and targeted treatments in Hodgkin's lymphoma. Cancer treatment reviews. 2014;40(3):457-64. Epub 2013/10/08. 41. de Claro RA, McGinn K, Kwitkowski V, Bullock J, Khandelwal A, Habtemariam B, et al. U.S. Food and Drug Administration approval summary: brentuximab vedotin for the treatment of relapsed Hodgkin lymphoma or relapsed systemic anaplastic large-cell lymphoma. Clin Cancer Res. 2012;18(21):5845-9. Epub 2012/09/11. 42. Monjanel H, Deville L, Ram-Wolff C, Venon MD, Franchi P, Benet C, et al. Brentuximab vedotin in heavily treated Hodgkin and anaplastic large-cell lymphoma, a single centre study on 45 patients. British journal of haematology. 2014;166(2):306-8. Epub 2014/03/29. 43. Naidoo J, Page DB, Wolchok JD. Immune modulation for cancer therapy. British journal of cancer. 2014. Epub 2014/09/12. 44. Bryan LJ, Gordon LI. Blocking tumor escape in hematologic malignancies: The anti-PD-1 strategy. Blood reviews. 2014. Epub 2014/09/28. 45. Armand P, Nagler A, Weller EA, Devine SM, Avigan DE, Chen YB, et al. Disabling immune tolerance by programmed death-1 blockade with pidilizumab after autologous hematopoietic stem-cell transplantation for diffuse large B-cell lymphoma: results of an international phase II trial. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2013;31(33):4199-206. Epub 2013/10/16. 46. Ansell SM, Lesokhin AM, Borrello I, Halwani A, Scott EC, Gutierrez M, et al. PD-1 Blockade with Nivolumab in Relapsed or Refractory Hodgkin's Lymphoma. N Engl J Med. 2014. Epub 2014/12/09. 47. Hao Y, Chapuy B, Monti S, Sun HH, Rodig SJ, Shipp MA. Selective JAK2 inhibition specifically decreases Hodgkin lymphoma and mediastinal large B-cell lymphoma growth in vitro and in vivo. Clin Cancer Res. 2014;20(10):2674-83. Epub 2014/03/13. 48. Younes A, Romaguera J, Fanale M, McLaughlin P, Hagemeister F, Copeland A, et al. Phase I study of a novel oral Janus kinase 2 inhibitor, SB1518, in patients with relapsed lymphoma: evidence of clinical and biologic activity in multiple lymphoma subtypes. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2012;30(33):4161-7. Epub 2012/09/12. 49. Kochenderfer JN, Dudley ME, Kassim SH, Somerville RP, Carpenter RO, Stetler-Stevenson M, et al. Chemotherapy-Refractory Diffuse Large B-Cell Lymphoma and Indolent B-Cell Malignancies Can Be Effectively Treated With Autologous T Cells Expressing an Anti-CD19 Chimeric Antigen Receptor. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2014. Epub 2014/08/27.
Table 1: Selected recent studies treating PMBCL.
Figure legend Figure 1: Targetable molecular features of primary mediastinal large B cell lymphoma. A. The main activation cascades of JAK-STAT and NFκB signaling are shown leading to altered transcriptional regulation. Only representative pathway molecules are displayed. Known gene alterations in the pathway are highlighted in color and pathway inhibitors are shown in the red boxes. B. A selection of surface markers as part of a PMBCL-specific expression profile is depicted alongside the respective targeted therapeutic approaches. C. Structural genomic alterations of chromosome 9p24 lead to over-expression of programmed death ligands, predominantly PDL2 (PDCD1LG2). Engagement of the cognate PD-1 receptors, induce T cell anergy that is potentially reversible by immunological checkpoint inhibition.
STAT inhibitors
JAK inhibitors
brentuximab vedotin
CAR T cells
rituximab
B. Targetable surface markers
CD30
CD19
CD20
P
P
P
p65
REL
IκBα IκBε
NEMO IKKα IKKβ
TRAF
RIP
9p24 - amplification - translocation - rearrangement - variable expression of B cell markers - overlap with classical Hodgkin lymphoma
proteasomal degradation
Immunological checkpoint inhibitors
PMBC PMBCL cellll
PDL2
PDL1
Anergic/ regulatory microenvironment
T cellll
PD-1
PD-1
C. Programmed death ligand axis
Proteasome inhibitors
A20
Structural genomic alterations
- inflammation - proliferation - differentiation
Transcriptional regulation
NFκB complex
SOCS1
STAT6
STAT6
STAT dimers/ oligomers
STAT6
STAT6
JAK2
P
STAT6
P
P
P
TNF receptor superfamily
PMBCL expression profile
PTPN1
STAT6
Interleukin receptors
A. Deregulated receptor signaling
Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma Kieron Dunleavy, Christian Steidl
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S0037-1963(15)00003-7 http://dx.doi.org/10.1053/j.seminhematol.2015.01.002 YSHEM50801
To appear in: Semin Hematol
Cite this article as: Kieron Dunleavy, Christian Steidl, Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma, Semin Hematol , http://dx.doi.org/10.1053/j.seminhematol.2015.01.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
January 6, 2015
Emerging biological insights and novel treatment strategies in primary mediastinal large B-cell lymphoma
Kieron Dunleavy1 and Christian Steidl2
1 2
Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA Centre for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, Canada
Address correspondence: Kieron Dunleavy MD, National Cancer Institute, Building 10, Room 12N226, 10 Center Drive, Bethesda, MD 20892, USA. Email: [email protected] Word count: Abstract: 148; Manuscript: 3124
ABSTRACT While primary mediastinal large B-cell lymphoma (PMBCL) is considered to be a subtype of diffuse large B-cell lymphoma (DLBCL), it is a distinct clinicopathologic entity, with clinical and biological features closely resembling nodular sclerosing Hodgkin lymphoma (NSHL). Recent studies have highlighted the shared biology of these two entities and identified novel critical pathways of lymphomagenesis including the presence of distinct mutations. Mediastinal grey zone lymphomas (MGZL) with features in between PMBCL and NSHL have been described as the missing link between the two parent entities. While the standard therapeutic approach to PMBCL has been immunochemotherapy followed by mediastinal radiation, strategies that obviate the need for radiation and thus eliminate its long-term toxicities have recently been developed. The identification of novel targets in PMBCL and MGZL pave the way for the testing of agents such as small molecule inhibitors of janus kinase pathways and immune checkpoint inhibitors. Future directions in these diseases should focus on combining effective novel agents with immunochemotherapy platforms.
INTRODUCTION Primary mediastinal B-cell lymphoma (PMBCL) constitutes 10% of all diffuse large B-cell lymphomas (DLBCL). It has demographic, clinical and biological characteristics that are distinct from the other subtypes of DLBCL (germinal center B-cell like (GCB) and activated B-cell like (ABC)) and more closely resembling those of nodular sclerosing Hodgkin lymphoma (NSHL) arising in the mediastinum. Gene expression profiling (GEP) studies have demonstrated that PMBCL and NSHL share a third of their genes and recent work has identified common driver mutations in both diseases(1, 2). Mediastinal grey zone lymphomas (MGZL) are much less frequently encountered than PMBCL and studies, albeit few, that have investigated their biological features, suggest that they represent a unique molecular entity(3). There has been much controversy as to what the optimal management of PMBCL patients should be owing to the rarity of the disease and lack of prospective studies. While most standard approaches have included rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) chemotherapy followed by mediastinal radiation, recent increased dose intensity approaches have eliminated the routine need for mediastinal radiation while maintaining high cure rates. Regarding future investigation, these diseases harbor several interesting targetable pathways that could be amenable to specific inhibitors of NF-kappa B and janus kinase pathways as well as immune checkpoint blockade. BIOLOGICAL INSIGHTS Pathogenic hallmarks PMBCL is recognized as a distinct entity in the 2008 WHO classification of Haematopoietic and Lymphoid tissues owing to the distinct gene expression profile, immunophenotype and clinical presentation that is markedly different from activated B cell (ABC)- and germinal center B cell (GCB)-type DLBCL.(4) Although a pathological and clinical spectrum including ABC/GCB-type DLBCL, PMBCL, MGZL, NS-HL has been recognized for a long time, pivotal gene expression profiling data and more recent genomic data define PMBCL as a unique lymphoid cancer characterized by molecular and clinical features that are shared with the related entities of the spectrum.(5) Summarizing the knowledge about genetic alterations, pathway pertubations and expression phenotypes, the most prominent PMBCL molecular hallmarks include activation of the JAK-STAT and NF B pathways, and avoiding immune destruction.(6) In the most recent past, high-resolution genomics approaches have added texture to our knowledge about these pathways and provided a number of genetic events that underlie phenotypic changes including point mutations, genomic rearrangements and copy number changes.(7-9) Interestingly, most of these genetic changes are present across the above mentioned pathobiological spectrum providing additional evidence for the molecular relatedness of these diseases. With the emergence of novel treatments targeting JAK-STAT signaling and the crosstalk of malignant cells with cells in the microenvironment via immune checkpoint blockade, a focused review of the JAK-STAT pathway, acquired immune privilege and related biomarkers is warranted in PMBCL. JAK-STAT pathway Activation of JAK-STAT signaling in PMBCL is a shared feature with CHL and well supported by gene expression profiling experiments and studies investigating the functional consequences of specific somatic gene mutations found in PMBCL patients and derived cell lines. In normal B cells the JAK-STAT pathway is activated by interleukin receptor subunit ligation by various interleukins or interferons, heterodimerization and phosphorylation of subunits and subsequent (auto)-phosphorylation of Janus kinases (JAKs) and STAT molecules that regulate gene transcription.(10) In PMBCL, JAK-STAT signaling is likely the summation of paracrine IL13 receptor-mediated signaling and constitutive activation by various somatic gene mutations in pathway molecules.(11) As evidence of intact paracrine signaling, IL13 stimulation led to increased and reversible levels of phosphorylated STAT5 in PMBCL-derived cell lines Med-B1.(12) Moreover, IL4 or IL13 stimulation of the PMBCL-derived cell line KARPAS 1106P induced an inflammatory phenotype reminiscent of CHL.(13) In
addition, amplification of JAK2, deletions or inactivating mutations of the negative regulators SOCS1 and PTPN1, and mutations in STAT6 are reported to result in constitutive pathway activation. As a result of these pathway perturbations, phosphorylated STAT6 has been suggested as a reliable marker to distinguish PMBCL from other large cell lymphoma subtypes.(11) However, patterns of concurrent or mutational exclusive pathway hits as well as the relative contributions of paracrine vs constitutive activation needs to be determined in future studies with implications for potential therapeutic targeting of the pathway. Gains and amplifications of the JAK2 locus on chromosome 9p were one of the first descriptions of somatic genetic alterations of JAK-STAT pathway members.(9, 14) Typically, the minimally amplified region contains multiple genes, including JAK2, the programmed death ligands CD274 (PDL1), PDCD1LG2 (PDL2) and JMJD2C(15), that act synergistically in the pathogenesis of PMBCL.(6) Although, 9p amplifications are present in more than half of all PMBCLs, there is now evidence that somatic point mutations of SOCS1 are at least as frequent. Melzner et al found point mutations including biallelic mutations in 45% of cases, and these high frequencies were confirmed and extended by whole transcriptome analysis (RNA-seq) identifying single nucleotide variants and indels in 7 of 7 clinical PMBCL cases.(16) Moreover, RNA-seq confirmed previously identified SOCS1 mutations in the cell lines Med-B1 and KARPAS 1106P.(7) SOCS1 mutations were also found in CHL and nodular lymphocyte predominant Hodgkin lymphoma, supporting the concept of shared genetic features across the pathological spectrum.(17, 18) In functional analyses inactivating SOCS1 mutations were shown to abrogate SOCS box function leading to hyperphosphorylation of JAK2 and STAT5.(16) As such SOCS1 acts a classical tumor suppressor controlling downstream signaling. Recently, mutations in an additional negative regulator of JAK-STAT signaling have been discovered through next generation sequencing. Using whole genome, transcriptome and targeted re-sequencing, Gunawardana and colleagues identified coding sequence mutations in the PTPN1 gene in 22% of PMCBL and 20% of CHL cases consisting of nonsense, missense and frameshift mutations.(7) PTPN1 encodes PTP1B, a non-receptor member of the superfamily of protein tyrosine phosphatases that was found to be a negative regulator of IL-4-induced STAT6 signaling.(19) The observed PTPN1 nonsense and missense mutations were confirmed as deleterious by partial or complete reduction of phosphatase activity of PTPN1 leading to sustained phosporylation of STAT3, STAT5 and STAT6. While JAK2 amplification, SOCS1 and PTPN1 all result in increased phosphorylation of STATs, there is also strong evidence that direct point mutations in STATs, specifically STAT6, might alter transcriptional programs and thereby contribute to the pathogenesis of PMBCL. Recurrent somatic mutations in STAT6 were reported in 36% of PMBCL cases (20). In summary, the frequent somatic mutations in the pathway and related constitutive pathway activation pinpoint JAK-STAT signaling as a very promising drug target. Acquired immune privilege The crosstalk of malignant cells with the cells in the lymphoma microenvironment is well recognized in the literature and the specific composition of the microenvironment represents a characteristic feature of many lymphoma subtypes.(21) In PMBCL, this tumor microenvironment is highly variable and reflects the pathological relatedness to the above described entities of the spectrum with resemblance to CHL on one end of the spectrum (very diverse cell types, relatively low abundance of malignant cells) and DLBCL on the other end (uniform appearance with high tumor content and sheets of neoplastic cells).(4) Importantly, from a biology point of view, the diversity of lymphoma-associated microenvironments is very likely the result of variable immune cell crosstalk between malignant and non-malignant cells that is selected for during disease progression. In PMBCL, the tumor hallmark of “immune privilege” is mainly supported by downregulation of MHC class I and II molecules and overexpression of programmed death ligands leading to reduced immunogenicity and T cell anergy. Recently, the genetic basis of these expression phenotypes has been partly elucidated highlighting the acquired nature of this oncogenic mechanism and suggesting therapeutic interference with acquired immune privilege as an effective approach in a subset of patients. Loss of major histocompatibility (MHC) molecules, in particular MHC class II has been described as a common feature in PMBCL.(22, 23) First indications that genomic changes underlie these expression changes came from microsatellite analysis and copy number analysis identifying allelic imbalances on chromosome 6p
harboring the MHC class I and II genes, although the number of affected cases was low.(9, 22) Interestingly, similar genomic imbalances are frequently found in cases of immune-privilege site (IP)-DLBCL (primary testicular DLBCL and primary central nervous system lymphoma) suggesting a possible genetic link between PMBCL and IP-DLBCL. Whole transcriptome sequencing analysis of CHL cell lines and subsequent screening by fluorescence in-situ hybridization (FISH) revealed recurrent chromosomal rearrangement of the CIITA locus on chromosome 16p.(24) CIITA encoded for the master transcriptional regulator of MHC class II expression and a tight correlation of CIITA and MHC class II expression has been observed previously in PMBCL.(23) CIITA rearrangements result in gene fusions with various gene partners, of which one specific fusion (CIITA-FLJ27352) was shown to act in a dominant negative fashion to reduce MHC class II expression in functional analyses.(24) Additional study is needed to establish CIITA loss of function mutations as a bona-fide mechanism in the pathogenesis of PMBCL. Increased expression of programmed death ligand 2 (encoded by PDCD1LG2 / PDL2) was discovered in early gene expression profiling studies in which PDL2 was part of the gene signature distinguishing PMBCL from ABC- and GCB-type DLBCL(1, 25). Integrative analysis of copy number and gene expression data in subsequent studies confirmed that PDL2 and its close paralog PDL1 (CD274) are both critical target genes of 9p gains and amplifications that are detectable in more than half of PMBCL cases.(8, 26) Moreover, recurrent genomic rearrangements involving the 9p locus were discovered by next generation sequencing and subsequent FISH analysis in 20% of PMBCL cases resulting in PDL1 and PDL2 gene fusions (8, 24). These findings confirm these genes as the critically deregulated genes on chromosome 9p24 and suggest upregulation of programmed death ligands and expression of PDL1- and PDL2-containing gene chimera as novel pathogenic events. Interestingly, PDL1 and PDL2 expression was found to be highest in the rearranged cases compared to cases with gains or amplifications (8). Moreover, ectopic expression of a CIITA-PDL2 gene fusion in DLBCL cell line U2932 inactivated JURKAT T cells in a co-culture system, and this inactivation could be reversed by blockade of the PD-1 receptor or ligand. These data demonstrate the functional consequence of these gene fusions for tumor microenvironment crosstalk and strongly suggest that blockade of the PD-1 axis could reverse acquired immune privilege. Co-amplification of JAK2 with the programmed death ligand locus on chromosome 9p24 suggests that JAKSTAT signaling and acquired immune privilege synergize in PMBCL lymphomagenesis. While it is intuitive that enhanced survival signaling and escape from immune destruction both independently contribute to tumor progression, a direct link between both pathways could be established by a PDL1 promoter study demonstrating STAT-dependent expression of PDL1.(26) Thus, combined inhibition of JAK-STAT and immune checkpoints seems promising in light of these findings. MANAGEMENT OF PMBCL AND MGZL Due to the rarity of PMBCL and the fact that it is a recently described entity, there are very few studies and no randomized comparisons of strategies to guide up-front therapy selection (table 1). It is a distinct clinicopathologic entity and should be approached as such therapeutically. Early trials that were principally led by Italian groups suggested that radiation was a critical component of curative therapy and today, consolidative mediastinal radiation remains part of standard therapy for a significant proportion of patients(27, 28). Given the young age and female gender of most patients with this disease, radiation leads to a long-term risk of breast cancer and other malignancies as well as ischemic heart disease and the high frequency of these complications has now been well documented in many childhood and adolescent cancer survivorship studies(29). Though some advocate that these complications are reduced with lower doses and more focused radiation fields, this has not been clearly demonstrated and may only be properly assessed with time and longer follow-up(30). It is therefore critical to develop strategies that remove the need for routine mediastinal radiation if they can maintain high cure rates in PMBCL. While R-CHOP has been extensively studied in other subtypes of DLBCL, the published experience in PMBCL is limited to retrospective studies or retrospective evaluations of prospective studies and in these, the
majority of patients received radiation therapy(31-33). The largest evaluation to date was a subgroup analysis of the randomized MabThera International Trial (MInT) where most patients received R-CHOP(31). Although the 3-year event-free survival was 78%, 73% received pre-planned radiation and adding radiation improved remission rates. It is important to note that this analysis was confined to patients with an age-adjusted international prognostic index (IPI) score of 0-1 and therefore does not reflect the entire clinical spectrum of the disease. In another retrospective analysis, 58 PMBCL patients had a PFS of 68% at 5 years after R-CHOP with 77% of responders receiving radiation(32). There was a high rate of primary induction failure (21%) and patients with higher IPI scores and disease that was not limited to the mediastinum fared significantly worse. Is it possible to use end of therapy FDGPET to guide who needs radiation? Ongoing studies in PMBCL, such as a large randomized IELSG multicenter study, are investigating if an end of therapy negative FDG-PET can identify patients who do not require radiation but with respect to patients who have received R-CHOP, a British Columbia study demonstrated that a sizeable portion of (end of therapy) FDG-PET negative cases subsequently relapsed(34). Due to the observation from retrospective studies that dose intensity has been important in PMBCL, an NCI study investigated dose adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin and rituximab (DA-EPOCH-R) without radiation in all clinical risk groups of PMBCL and in 51 patients, EFS and OS were 93% and 97% respectively at 5 years(35). In addition, 16 PMBCL patients who received the regimen at Stanford had an EFS and OS of 100% without radiation and the approach is under investigation in other studies including pediatric groups where an early report suggested high efficacy without the need for radiation(36). Regarding the role of FDG-PET in the management of PMBCL, it is important to consider that an end of treatment FDG-PET has a low positive predictive value in contrast to the high clinical accuracy of the technique in other aggressive lymphomas(28, 35). Therefore, alternative, more-specific imaging technologies should be evaluated in this disease in the future. MGZLs, with histological and immunophenotypical features that are transitional between PMBCL and NSHL were only recently identified and are exceedingly rare. Therefore, they have not been well studied. Previously, these tumors were likely identified as “anaplastic large-cell lymphoma Hodgkin-like” and this entity was reported to have a poor outcome with chemotherapy(37). The indeterminate pathobiology of MGZL has led to uncertainty about its optimal therapeutic approach(38). A recent prospective study looked at the outcome of MGZL following treatment with DA-EPOCH-R and reported an inferior survival compared to that of PMBCL, although both patient groups had similar clinical characteristics. (EFS and OS of 62% and 74% versus 93% and 97% for PMBCL)(39). Studies looking at the molecular characteristics of MGZL are ongoing and are attempting to explain the biological basis for the inferior outcome of this lymphoma. NOVEL AGENTS AND EMERGING STRATEGIES Due to significant strides over recent years in elucidating the molecular biology of PMBCL and MGZL, several new targets have now been recognized and this paves the way for testing novel agents in these diseases (figure 1). The close clinical and biological relationship of these lymphomas to HL is important to consider as new agents that are effective in HL may also have good activity in PMBCL and MGZL. Brentuximab vedotin is an antibody drug conjugate consisting of a chimeric anti-CD30 monoclonal antibody on which the microtubule inhibitor monomethyl auristatin E (MMAE) is attached via a valine citrulline linker(40). Following its binding to CD30, brentuximab vedotin is internalized and MMAE released. This agent induces responses in a high percentage of cases of relapsed and refractory Hodgkin lymphoma and is currently being investigated in upfront therapy(41, 42). As CD30 is variably expressed in PMBCL and MGZL, brentuximab is a rational agent to study in these diseases and is currently under investigation in combination with R-CHOP in newly diagnosed PMBCL and MGZL. 70% of cases of PMBCL have amplification on a region of chromosome 9p24 that constitutes critical targets such as the PD1 ligands programmed cell death ligand 1 (PD-L1) and PD-L2 and janus kinase 2 (JAK2)(14, 15, 26). The PD-1 checkpoint pathway appears to facilitate evasion of the anti-tumor immune response and immune
checkpoint inhibitors have demonstrated exciting activity in a wide range of cancers such as melanoma(43). AntiPD1 activity likely results from both direct anti-tumor effects related to binding to PD-1 or PD-L1 and also restoration of the immune anti-tumor response by enhancing T-cell and NK-cell function(44). Pidilizumab is a humanized monoclonal antibody that binds to PD-1 - in one phase 2 trial of the agent in relapsed aggressive B-cell lymphoma, patients with primary mediastinal B-cell lymphoma were included but it is difficult to interpret the activity of the agent as the primary end-point of the study was to prevent disease relapse and the number of patients with PMBCL was small(45). Nivolumab is another fully humanized IgG-4 blocking antibody and is currently under investigation in relapsed and refractory Hodgkin lymphoma – in an early report of its activity in this disease population, an objective response was reported in 87% of patients including 17% with a complete response(46). Several other immune checkpoint inhibitors are in development and given their activity in HL, they represent an interesting and promising class of agents to study in PMBCL and MGZL. The Janus kinases (JAKs) that mediate cytokine receptor signaling play a role in many hematological malignancies. JAK2 signaling is important in both PMBCL and HL and selective JAK2 inhibition has been shown to specifically decrease PMBCL and HL growth in vitro and in vivo (47). The JAK2/FLT3 inhibitor, SB1518, was tested in relapsed or refractory HL and NHL and demonstrated encouraging activity but there were not enough cases of PMBCL to specifically evaluate its activity in that group(48). Several other JAK inhibitors are in clinical development including ruxolitinib, an oral JAK1/2 inhibitor, that is FDA approved for myelofibrosis. Other interesting strategies for PMBCL include using genetically modified T-cells – a recent study that treated patients with autologous T-cells expressing an anti-CD19 chimeric antigen receptor (CAR) reported a high complete remission rate in DLBCL and indolent lymphomas(49). Most cases of PMBCL have expression of CD19 and two patients who had received several lines of previous treatment had complete responses lasting beyond 12 months with this approach. CONCLUSIONS PMBCL and MGZL are intriguing mediastinal lymphomas and significant progress has been made recently in elucidating their biological characteristics. Though recognized as a subtype of DLBCL, PMBCL is cliniopathologically distinct from other DLBCLs and should be approached differently, therapeutically. While radiation therapy has historically been a standard treatment modality for PMBCL, novel approaches obviate its need and importantly, eliminate its long-term risks. Insights into the biology of these diseases have paved the way for investigating small molecule inhibitors and novel immunotherapeutic approaches in the future. Authorship CS and KD contributed to the writing of the manuscript and approved the final version. CS and KD have no relevant conflicts of interest. KD receives funding from the Intramural Program of the National Cancer Institute. C.S. is supported by a New Investigator Award from the Canadian Institutes of Health Research (CIHR) and a Career Investigator Award from the Michael Smith Foundation for Health Research.
References 1. Rosenwald A, Wright G, Leroy K, Yu X, Gaulard P, Gascoyne RD, et al. Molecular diagnosis of primary mediastinal B cell lymphoma identifies a clinically favorable subgroup of diffuse large B cell lymphoma related to Hodgkin lymphoma. J Exp Med. 2003;198(6):851-62. 2. Gunawardana J, Chan FC, Telenius A, Woolcock B, Kridel R, Tan KL, et al. Recurrent somatic mutations of PTPN1 in primary mediastinal B cell lymphoma and Hodgkin lymphoma. Nature genetics. 2014;46(4):329-35. Epub 2014/02/18. 3. Eberle FC, Salaverria I, Steidl C, Summers TA, Jr., Pittaluga S, Neriah SB, et al. Gray zone lymphoma: chromosomal aberrations with immunophenotypic and clinical correlations. Mod Pathol. 2011;24(12):1586-97. Epub 2011/08/09. 4. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al., editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France: IARC 2008. 5. Grant C, Dunleavy K, Eberle FC, Pittaluga S, Wilson WH, Jaffe ES. Primary mediastinal large B-cell lymphoma, classic Hodgkin lymphoma presenting in the mediastinum, and mediastinal gray zone lymphoma: what is the oncologist to do? Curr Hematol Malig Rep. 2011;6(3):157-63. Epub 2011/05/19. 6. Steidl C, Gascoyne RD. The molecular pathogenesis of primary mediastinal large B-cell lymphoma. Blood. 2011;118(10):2659-69. Epub 2011/06/28. 7. Gunawardana J, Chan FC, Telenius A, Woolcock B, Kridel R, Tan KL, et al. Recurrent somatic mutations of PTPN1 in primary mediastinal B cell lymphoma and Hodgkin lymphoma. Nat Genet. 2014. Epub 2014/02/18. 8. Twa DDW, Chan FC, Ben-Neriah S, Woolcock BW, Tan KL, Slack GW, et al. Genomic Rearrangements Involving Programmed Death Ligands Are Recurrent In Primary Mediastinal Large B-Cell Lymphoma. Blood. 2013;122(21):635. 9. Wessendorf S, Barth TF, Viardot A, Mueller A, Kestler HA, Kohlhammer H, et al. Further delineation of chromosomal consensus regions in primary mediastinal B-cell lymphomas: an analysis of 37 tumor samples using high-resolution genomic profiling (array-CGH). Leukemia. 2007;21(12):2463-9. 10. Darnell JE, Jr., Kerr IM, Stark GR. Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins. Science. 1994;264(5164):1415-21. Epub 1994/06/03. 11. Guiter C, Dusanter-Fourt I, Copie-Bergman C, Boulland ML, Le Gouvello S, Gaulard P, et al. Constitutive STAT6 activation in primary mediastinal large B-cell lymphoma. Blood. 2004;104(2):543-9. Epub 2004/03/27. 12. Raia V, Schilling M, Bohm M, Hahn B, Kowarsch A, Raue A, et al. Dynamic mathematical modeling of IL13-induced signaling in Hodgkin and primary mediastinal B-cell lymphoma allows prediction of therapeutic targets. Cancer Res. 2011;71(3):693-704. Epub 2010/12/04. 13. Andersson E, Schain F, Sjoberg J, Bjorkholm M, Claesson HE. Interleukin-13 stimulation of the mediastinal B-cell lymphoma cell line Karpas-1106P induces a phenotype resembling the Hodgkin lymphoma cell line L1236. Exp Hematol. 2010;38(2):116-23. Epub 2009/11/26. 14. Joos S, Otano-Joos MI, Ziegler S, Bruderlein S, du Manoir S, Bentz M, et al. Primary mediastinal (thymic) B-cell lymphoma is characterized by gains of chromosomal material including 9p and amplification of the REL gene. Blood. 1996;87(4):1571-8. Epub 1996/02/15. 15. Rui L, Emre NC, Kruhlak MJ, Chung HJ, Steidl C, Slack G, et al. Cooperative epigenetic modulation by cancer amplicon genes. Cancer Cell. 2010;18(6):590-605. Epub 2010/12/16. 16. Melzner I, Bucur AJ, Bruderlein S, Dorsch K, Hasel C, Barth TF, et al. Biallelic mutation of SOCS-1 impairs JAK2 degradation and sustains phospho-JAK2 action in the MedB-1 mediastinal lymphoma line. Blood. 2005;105(6):2535-42. Epub 2004/12/02. 17. Mottok A, Renne C, Willenbrock K, Hansmann ML, Brauninger A. Somatic hypermutation of SOCS1 in lymphocyte-predominant Hodgkin lymphoma is accompanied by high JAK2 expression and activation of STAT6. Blood. 2007;110(9):3387-90. Epub 2007/07/27.
18. Weniger MA, Melzner I, Menz CK, Wegener S, Bucur AJ, Dorsch K, et al. Mutations of the tumor suppressor gene SOCS-1 in classical Hodgkin lymphoma are frequent and associated with nuclear phospho-STAT5 accumulation. Oncogene. 2006;25(18):2679-84. 19. Lu X, Malumbres R, Shields B, Jiang X, Sarosiek KA, Natkunam Y, et al. PTP1B is a negative regulator of interleukin 4-induced STAT6 signaling. Blood. 2008;112(10):4098-108. Epub 2008/08/22. 20. Ritz O, Guiter C, Castellano F, Dorsch K, Melzner J, Jais JP, et al. Recurrent mutations of the STAT6 DNA binding domain in primary mediastinal B-cell lymphoma. Blood. 2009;114(6):1236-42. Epub 2009/05/09. 21. Scott DW, Gascoyne RD. The tumour microenvironment in B cell lymphomas. Nat Rev Cancer. 2014;14(8):517-34. Epub 2014/07/11. 22. Rigaud G, Moore PS, Taruscio D, Scardoni M, Montresor M, Menestrina F, et al. Alteration of chromosome arm 6p is characteristic of primary mediastinal B-cell lymphoma, as identified by genome-wide allelotyping. Genes Chromosomes Cancer. 2001;31(2):191-5. Epub 2001/04/25. 23. Roberts RA, Wright G, Rosenwald AR, Jaramillo MA, Grogan TM, Miller TP, et al. Loss of major histocompatibility class II gene and protein expression in primary mediastinal large B-cell lymphoma is highly coordinated and related to poor patient survival. Blood. 2006;108(1):311-8. 24. Steidl C, Shah SP, Woolcock BW, Rui L, Kawahara M, Farinha P, et al. MHC class II transactivator CIITA is a recurrent gene fusion partner in lymphoid cancers. Nature. 2011;471(7338):377-81. Epub 2011/03/04. 25. Savage KJ, Monti S, Kutok JL, Cattoretti G, Neuberg D, De Leval L, et al. The molecular signature of mediastinal large B-cell lymphoma differs from that of other diffuse large B-cell lymphomas and shares features with classical Hodgkin lymphoma. Blood. 2003;102(12):3871-9. 26. Green MR, Monti S, Rodig SJ, Juszczynski P, Currie T, O'Donnell E, et al. Integrative analysis reveals selective 9p24.1 amplification, increased PD-1 ligand expression, and further induction via JAK2 in nodular sclerosing Hodgkin lymphoma and primary mediastinal large B-cell lymphoma. Blood. 2010;116(17):3268-77. Epub 2010/07/16. 27. Zinzani PL, Martelli M, Bertini M, Gianni AM, Devizzi L, Federico M, et al. Induction chemotherapy strategies for primary mediastinal large B-cell lymphoma with sclerosis: a retrospective multinational study on 426 previously untreated patients. Haematologica. 2002;87(12):1258-64. Epub 2002/12/24. 28. Martelli M, Ceriani L, Zucca E, Zinzani PL, Ferreri AJ, Vitolo U, et al. [18F]Fluorodeoxyglucose Positron Emission Tomography Predicts Survival After Chemoimmunotherapy for Primary Mediastinal Large B-Cell Lymphoma: Results of the International Extranodal Lymphoma Study Group IELSG-26 Study. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2014. Epub 2014/05/07. 29. Castellino SM, Geiger AM, Mertens AC, Leisenring WM, Tooze JA, Goodman P, et al. Morbidity and mortality in long-term survivors of Hodgkin lymphoma: a report from the Childhood Cancer Survivor Study. Blood. 2011;117(6):1806-16. Epub 2010/11/03. 30. O'Brien MM, Donaldson SS, Balise RR, Whittemore AS, Link MP. Second malignant neoplasms in survivors of pediatric Hodgkin's lymphoma treated with low-dose radiation and chemotherapy. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2010;28(7):1232-9. Epub 2010/02/04. 31. Rieger M, Osterborg A, Pettengell R, White D, Gill D, Walewski J, et al. Primary mediastinal B-cell lymphoma treated with CHOP-like chemotherapy with or without rituximab: results of the Mabthera International Trial Group study. Ann Oncol. 2011;22(3):664-70. Epub 2010/08/21. 32. Soumerai JD, Hellmann MD, Feng Y, Sohani AR, Toomey CE, Barnes JA, et al. Treatment of primary mediastinal B-cell lymphoma with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone is associated with a high rate of primary refractory disease. Leuk Lymphoma. 2014;55(3):538-43. Epub 2013/06/06. 33. Savage KJ, Al-Rajhi N, Voss N, Paltiel C, Klasa R, Gascoyne RD, et al. Favorable outcome of primary mediastinal large B-cell lymphoma in a single institution: the British Columbia experience. Ann Oncol. 2006;17(1):123-30. Epub 2005/10/21. 34. Savage KJ, Yenson PR, Shenkier T, Klasa R, Villa D, Goktepe O, et al. The Outcome of Primary Mediastinal Large B-Cell Lymphoma (PMBCL) in the R-CHOP Treatment Era. Blood (ASH Annual Meeting Abstracts) 2012 120: Abstract 303.
35. Dunleavy K, Pittaluga S, Maeda LS, Advani R, Chen CC, Hessler J, et al. Dose-adjusted EPOCH-rituximab therapy in primary mediastinal B-cell lymphoma. N Engl J Med. 2013;368(15):1408-16. Epub 2013/04/12. 36. Woessmann W, Lisfeld J, Burkhardt B. Therapy in primary mediastinal B-cell lymphoma. N Engl J Med. 2013;369(3):282. Epub 2013/07/19. 37. Cazals-Hatem D, Andre M, Mounier N, Copin MC, Divine M, Berger F, et al. Pathologic and clinical features of 77 Hodgkin's lymphoma patients treated in a lymphoma protocol (LNH87): a GELA study. Am J Surg Pathol. 2001;25(3):297-306. Epub 2001/02/27. 38. Dunleavy K, Grant C, Eberle FC, Pittaluga S, Jaffe ES, Wilson WH. Gray zone lymphoma: better treated like hodgkin lymphoma or mediastinal large B-cell lymphoma? Current hematologic malignancy reports. 2012;7(3):241-7. Epub 2012/07/27. 39. Wilson WH, Pittaluga S, Nicolae A, Camphausen K, Shovlin M, Steinberg SM, et al. A prospective study of mediastinal gray zone lymphoma. Blood. 2014. Epub 2014/07/16. 40. Provencio M, Sanchez A, Sanchez-Beato M. New drugs and targeted treatments in Hodgkin's lymphoma. Cancer treatment reviews. 2014;40(3):457-64. Epub 2013/10/08. 41. de Claro RA, McGinn K, Kwitkowski V, Bullock J, Khandelwal A, Habtemariam B, et al. U.S. Food and Drug Administration approval summary: brentuximab vedotin for the treatment of relapsed Hodgkin lymphoma or relapsed systemic anaplastic large-cell lymphoma. Clin Cancer Res. 2012;18(21):5845-9. Epub 2012/09/11. 42. Monjanel H, Deville L, Ram-Wolff C, Venon MD, Franchi P, Benet C, et al. Brentuximab vedotin in heavily treated Hodgkin and anaplastic large-cell lymphoma, a single centre study on 45 patients. British journal of haematology. 2014;166(2):306-8. Epub 2014/03/29. 43. Naidoo J, Page DB, Wolchok JD. Immune modulation for cancer therapy. British journal of cancer. 2014. Epub 2014/09/12. 44. Bryan LJ, Gordon LI. Blocking tumor escape in hematologic malignancies: The anti-PD-1 strategy. Blood reviews. 2014. Epub 2014/09/28. 45. Armand P, Nagler A, Weller EA, Devine SM, Avigan DE, Chen YB, et al. Disabling immune tolerance by programmed death-1 blockade with pidilizumab after autologous hematopoietic stem-cell transplantation for diffuse large B-cell lymphoma: results of an international phase II trial. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2013;31(33):4199-206. Epub 2013/10/16. 46. Ansell SM, Lesokhin AM, Borrello I, Halwani A, Scott EC, Gutierrez M, et al. PD-1 Blockade with Nivolumab in Relapsed or Refractory Hodgkin's Lymphoma. N Engl J Med. 2014. Epub 2014/12/09. 47. Hao Y, Chapuy B, Monti S, Sun HH, Rodig SJ, Shipp MA. Selective JAK2 inhibition specifically decreases Hodgkin lymphoma and mediastinal large B-cell lymphoma growth in vitro and in vivo. Clin Cancer Res. 2014;20(10):2674-83. Epub 2014/03/13. 48. Younes A, Romaguera J, Fanale M, McLaughlin P, Hagemeister F, Copeland A, et al. Phase I study of a novel oral Janus kinase 2 inhibitor, SB1518, in patients with relapsed lymphoma: evidence of clinical and biologic activity in multiple lymphoma subtypes. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2012;30(33):4161-7. Epub 2012/09/12. 49. Kochenderfer JN, Dudley ME, Kassim SH, Somerville RP, Carpenter RO, Stetler-Stevenson M, et al. Chemotherapy-Refractory Diffuse Large B-Cell Lymphoma and Indolent B-Cell Malignancies Can Be Effectively Treated With Autologous T Cells Expressing an Anti-CD19 Chimeric Antigen Receptor. Journal of clinical oncology : official journal of the American Society of Clinical Oncology. 2014. Epub 2014/08/27.
Table 1: Selected recent studies treating PMBCL.
Figure legend Figure 1: Targetable molecular features of primary mediastinal large B cell lymphoma. A. The main activation cascades of JAK-STAT and NFκB signaling are shown leading to altered transcriptional regulation. Only representative pathway molecules are displayed. Known gene alterations in the pathway are highlighted in color and pathway inhibitors are shown in the red boxes. B. A selection of surface markers as part of a PMBCL-specific expression profile is depicted alongside the respective targeted therapeutic approaches. C. Structural genomic alterations of chromosome 9p24 lead to over-expression of programmed death ligands, predominantly PDL2 (PDCD1LG2). Engagement of the cognate PD-1 receptors, induce T cell anergy that is potentially reversible by immunological checkpoint inhibition.
STAT inhibitors
JAK inhibitors
brentuximab vedotin
CAR T cells
rituximab
B. Targetable surface markers
CD30
CD19
CD20
P
P
P
p65
REL
IκBα IκBε
NEMO IKKα IKKβ
TRAF
RIP
9p24 - amplification - translocation - rearrangement - variable expression of B cell markers - overlap with classical Hodgkin lymphoma
proteasomal degradation
Immunological checkpoint inhibitors
PMBC PMBCL cellll
PDL2
PDL1
Anergic/ regulatory microenvironment
T cellll
PD-1
PD-1
C. Programmed death ligand axis
Proteasome inhibitors
A20
Structural genomic alterations
- inflammation - proliferation - differentiation
Transcriptional regulation
NFκB complex
SOCS1
STAT6
STAT6
STAT dimers/ oligomers
STAT6
STAT6
JAK2
P
STAT6
P
P
P
TNF receptor superfamily
PMBCL expression profile
PTPN1
STAT6
Interleukin receptors
A. Deregulated receptor signaling