- Email: [email protected]
Circulating Melanoma Cells as a Predictive Biomarker
COMMENTARY
approach using embedded materials with well-defined elastic moduli, and at controlled depths within a phantom matrix, must also be undertaken. Furthermore, the experimental measurements must be used to validate computational models of these same scenarios, as in the study conducted by Roduit et al. (2009). When such data are forthcoming and a platform of confidence in the approach has been firmly established, then the pursuit of more intricate relationships, such as the depth dependence of filaggrin degradation suggested by Beard et al. (2013), ought to be possible. By undertaking parallel electrophysiology on targeted structures during the nanoindentation process, perhaps by the implementation of recent microfabrication innovations for intra-cellular recording (Duan et al., 2011), a realtime assessment of membrane trafficking can also be undertaken during the critical bulk penetration stage, which will inform on downstream viability profiles. The emergence of the new tomography technique is also rather timely: researchers will not have to go through the trouble and expense involved in generating their own ‘nano-needle’ tips, as commercially available entities have already emerged (viz NaugaNeedles.com or www.Nanotools.com for example). It would thus seem that the only short-term limitation with local probe tomography will rest in the collective imagination of its first wave of users. CONFLICT OF INTEREST
MCF7 human breast cancer cells. Proc. 15th European Microscopy Congress. Manchester Duan X, Gao R, Xie P et al. (2011) Intracellular recordings of action potentials by an extracellular nanoscale field-effect transistor. Nat Nanotechnol 7:174–9 Dulinska-Molak I, Lekka M, Lewandowska M et al. (2012) Preliminary studies on the characteristics of corneocytes using atomic force microscopy (AFM). Pol J Cosmetol 15:50–7 Gaikwad RM, Vasilyev SI, Datta S et al. (2010) Atomic force microscopy characterization of corneocytes: effect of moisturizer on their topology, rigidity, and friction. Skin Res Technol 16:275–82
O’Connor SD, Komisarek KL, Baldeschwieler JD (1995) Atomic force microscopy of human hair cuticles: a microscopic study of environmental effects on hair morphology. J Invest Dermatol 105:96–9 Pesen D, Hoh JH (2005) Micromechanical architecture of the endothelial cell cortex. Biophys J 88:670–9 Plodinec M, Loparic M, Monnier CA et al. (2012) The nanomechanical signature of breast cancer. Nat Nanotechnol 7:757–65 Roduit C, Sekatski S, Dietler G et al. (2009) Stiffness tomography by atomic force microscopy. Biophys J 97:674–7
See related article on pg 1582
Circulating Melanoma Cells as a Predictive Biomarker Giorgos Karakousis1, Ruifeng Yang2 and Xiaowei Xu2 The prognosis of patients with metastatic melanoma has improved significantly with targeted therapeutic agents and immunotherapies. Detection of early melanoma recurrence after treatment will be beneficial to switch patients who fail on one therapy to different modalities. Circulating tumor cells (CTCs) are cancer cells released by a tumor into the peripheral blood. These cells hold potential as prognostic, predictive, and pharmacodynamic biomarkers for treatment. In this issue, Khoja et al. report that melanoma CTCs can be detected using Melcam and high molecular weight melanoma–associated antibody. They found that in 101 stage IV melanoma patients, CTC numbers ranged between 0 and 36/ 7.5 ml blood; 26% of the patients had X2 CTCs at baseline. The CTC number (X2 CTCs) at baseline was significantly prognostic for median overall survival (OS) in univariate and multivariate analysis. Patients receiving treatment where CTC numbers remained X2 CTCs during their treatment had shorter median OS than those who maintained o2 CTCs (7 vs. 10 months, hazard ratio 0.34, 95% confidence interval 0.14–0.81, log-rank test P ¼ 0.015). The implications of this work are substantial in counseling patients about their prognosis and in helping to assess responses to systemic therapies. Journal of Investigative Dermatology (2013) 133, 1460–1462. doi:10.1038/jid.2013.34
The authors state no conflict of interest.
REFERENCES Beard J (2011) Electron beam deposited nanotools for nanomanipulation and biological applications. PhD Thesis. University of Bath: Bath, UK Beard JD, Guy RH, Gordeev SN (2013) Mechanical tomography of human corneocytes with a nanoneedle. J Invest Dermatol 133:1565–71 Bhushan Bharat (2012) Nanotribological and nanomechanical properties of skin with and without cream treatment using atomic force microscopy and nanoindentation. J Colloid Interface Sci 367:1–33
Targeted therapies such as the mutant BRAF selective inhibitors vemurafenib and dabrafenib have improved the survival of patients with metastatic melanoma (Flaherty et al., 2010, 2012a,b; Sosman et al., 2012). However, subsequent drug resistance and disease progression has been observed in most of the treated patients (Flaherty, 2012).
Anti-CTLA4 and anti-PD1 immunotherapies have also improved overall survival (OS) in metastatic melanoma patients, with a subset of patients having long-term survival (Hodi et al., 2010; Lipson et al., 2013). With effective therapies of this sort, it has become important to monitor patients and to identify early signs of treatment failure.
Binnig G, Rohrer H (1987) Scanning tunneling microscopy from birth to adolescence. Rev Mod Phys 59:615–25
1
Conneely M, Rolfsnes H, McGloin D et al. (2012) Influence of ultrasound exposure on cellmechanical properties: a preliminary study on
Correspondence: Xiaowei Xu, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA. E-mail: [email protected]
Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA and 2Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
1460 Journal of Investigative Dermatology (2013), Volume 133
COMMENTARY
Clinical Implications
Melanoma circulating tumor cells (CTCs) can be detected using antibodies against melanocyte surface markers.
In multivariate analysis CTC number (X2 CTCs) is an independent prognostic biomarker of overall survival (OS).
Patients receiving treatment where CTC number remained X2 CTCs during treatment had shorter median OS than those who maintained o2 CTCs.
However, detection of early recurrence and treatment failure is difficult, and obtaining tumor biopsies is not without risk. Less invasive approaches to assess treatment responses would therefore have clinical utility. During tumor progression, a subpopulation of tumor cells gain access and escape into the lymphatic or blood vessels and circulate until they are either eliminated by host response mechanisms or find an microenvironment in which to reside where they may eventually proliferate. In our own work, we found that lymphatic invasion occurs commonly in primary melanomas (Xu et al., 2008, 2012). Importantly, the detection of circulating tumor cells (CTCs) in the peripheral blood of patients with cancer has prognostic and therapeutic implications (Cristofanilli et al., 2004). However, the number of CTCs can be very small, and these cells are not easily detected. Therefore, a key to the use of CTCs as a biomarker is technology designed to enrich cancer cells from peripheral blood. FDA has approved the Veridex CellTrack Analyzer for use in monitoring therapeutic responses in patients with breast, prostate, or colon cancer. This technology relies on the expression of epithelial cellular adhesion molecular (EpCAM). Most CTC studies in the literature have focused on epithelial cancers. In the study reported by Khoja et al. (2013), the authors used a melanomaspecific CellSearch CTC kit, using Melcam and high molecular weight melanoma associated antibody (HMWMAA), which is also identified as a melanoma-associated chondroitin sulfate proteoglycan antibody for melanoma CTC capture and detection. Both
markers are reported to be expressed in up to 80% of metastatic melanoma lesions (Campoli et al., 2004). The authors found that 40% of melanoma patients in a cohort of 101 have one or more CTCs at baseline, with nearly 79% having advanced M1c disease. In patientso60 years of age, the sensitivity of CTCs above 0 was 33%. Using the threshold of X2 CTCs, which the authors proposed as useful, 26% of the patients fell into this category. Multivariate Cox proportional hazards regression analysis demonstrated that, after adjusting for other significant univariate factors, such as lactate dehydrogenase, performance status, treatment with a BRAF or MEK inhibitor, CTC number was an independent prognostic factor for OS (hazard ratio (HR) 2.403, 95% confidence interval (CI) 1.303–4.430, P ¼ 0.005). Although melanoma CTCs identified by Melcam and HMW-MAA indeed did identify a cohort of patients with extremely poor prognosis, the remaining cohort (74%) still had a relatively poor outcome with a median OS of only 7.2 months. Thus, it is conceivable that a majority of stage M1c melanoma patients have CTCs in their peripheral blood; however, these CTCs are not detectable by the combination of Melcam and HMWMAA antibodies. As pointed out by the authors, the level of antigen expression on melanoma cells in the circulation is unknown, especially with respect to the detection limits of the Veridex platform. CTCs may therefore have different surface antigen characteristics than do the corresponding tissue metastases. Low melanocytic marker expression on CTCs may be one of the reasons why the majority of their patients (75%) had
o2 CTCs and 60% had no CTCs. Therefore, other melanocytic markers should be tested to optimize detection of melanoma CTCs. The authors also explored the pharmacodynamic CTC changes and prognostic significance of CTC number after treatment. Although the sample size is relatively small (28 of 45 patients exhibited pharmacodynamic changes in CTC number), the prognostic significance of CTC number recorded before and at any time point during treatment for all 45 patients confirmed longer survival for patients with o2 CTCs at any time point during treatment (10 vs. 7 months, HR 0.34, CI 0.14–0.81, log-rank test P ¼ 0.015). As CTCs were measured at 6–9 weeks post initiation of treatment in the current study, it would be interesting to measure the CTC number at very early time points after initiation of therapy, to see if clinical responses could be predicted prior to their occurrence. Nevertheless, the implications of this work are significant both for counseling patients on prognosis and also for helping to assess the response to systemic therapies. Despite the progress of research on CTCs, the biology of CTCs needs to be further characterized. It is still unclear whether CTCs are similar to the bulk of tumor cells in the primary site or to solid metastases, whether they represent the so-called ‘‘tumor-initiating cells’’, and whether there is heterogeneity among CTCs in an individual patient on the molecular level. More studies are needed to address these important issues. Summary
The work by Khoja et al. (2013) imparts important insights into the melanoma biology. The investigators provide evidence that melanoma CTCs can be detected using antibodies against melanocyte surface markers. CTC number (X2 CTCs) is an independent worse prognostic biomarker of OS. Patients receiving treatment where CTC number remained at X2 CTCs during treatment had a shorter median OS than those that maintained o2 CTCs. Their work generates further impetus for studies aimed at increasing the sensitivity of melanoma CTC detection www.jidonline.org 1461
COMMENTARY
and at addressing whether melanoma CTCs can help serve as predictive biomarkers for risk stratification of patients for clinical treatments and for early prediction of response to therapies. CONFLICT OF INTEREST
The authors state no conflict of interest.
See related article on pg 1610
The Dark Side of Cyclophosphamide: Cyclophosphamide-Mediated Ablation of Regulatory T Cells Ju¨rgen C. Becker1 and David Schrama1
ACKNOWLEDGMENTS The writing of this Commentary was made possible in part by research grants from the NIH grant R01AR054593.
REFERENCES Campoli MR, Chang CC, Kageshita T et al. (2004) Human high molecular weight-melanomaassociated antigen (HMW-MAA): a melanoma cell surface chondroitin sulfate proteoglycan (MSCP) with biological and clinical significance. Crit Rev Immunol 24:267–96 Cristofanilli M, Budd GT, Ellis MJ et al. (2004) Circulating tumor cells, disease progression, and survival in metastatic breast cancer. N Engl J Med 351:781–91 Flaherty KT (2012) Targeting metastatic melanoma. Annu Rev Med 63:171–83 Flaherty KT, Infante JR, Daud A et al. (2012a) Combined BRAF and MEK inhibition in melanoma with BRAF V600 mutations. N Engl J Med 367:1694–703 Flaherty KT, Puzanov I, Kim KB et al. (2010) Inhibition of mutated, activated BRAF in metastatic melanoma. N Engl J Med 363:809–19 Flaherty KT, Robert C, Hersey P et al. (2012b) Improved survival with MEK inhibition in BRAF-mutated melanoma. N Engl J Med 367:107–14 Hodi FS, O’Day SJ, McDermott DF et al. (2010) Improved survival with ipilimumab in patients with metastatic melanoma. N Engl J Med 363:711–23 Khoja L, Loriqan P, Zhou C et al. (2013) Biomarker utility of circulating tumour cells in metastatic cutaneous melanoma. J Invest Dermatol 133:1582–90 Lipson EJ, Sharfman WH, Drake CG et al. (2013) Durable cancer regression off-treatment and effective re-induction therapy with an antiPD-1 antibody. Clin Cancer Res 19:462–8 Sosman JA, Kim KB, Schuchter L et al. (2012) Survival in BRAF V600-mutant advanced melanoma treated with vemurafenib. N Engl J Med 366:707–14 Xu X, Chen L, Guerry D et al. (2012) Lymphatic invasion is independently prognostic of metastasis in primary cutaneous melanoma. Clin Cancer Res 18:229–37 Xu X, Gimotty PA, Guerry D et al. (2008) Lymphatic invasion revealed by multispectral imaging is common in primary melanomas and associates with prognosis. Hum Pathol 39:901–9
Cancer immune escape is frequently associated with the induction of an inappropriate immune response, i.e., a response that does not inhibit but perhaps even promotes the tumor. Indeed, increased frequencies of tumor-infiltrating regulatory T cells (Tregs) are associated with an impaired prognosis in several cancers. Thus, depletion of Tregs, e.g., by cyclophosphamide, was proposed as a means to boost immune responses to cancer. In the present issue of the Journal, Sevko et al., however, provide evidence that cyclophosphamide exerted the unexpected effect of induction of myeloid-derived suppressor cells. Journal of Investigative Dermatology (2013) 133, 1462–1465. doi:10.1038/jid.2013.67
Malignant cells can be detected and destroyed by cells of the immune system in general, and by cells of the adaptive immune system in particular. In fact, there is strong evidence that immunological recognition has an impact on prognosis (Mellman et al., 2011; Wang et al., 2012). Nevertheless, there is equally strong evidence that in many cancer patients the cancerous cells impair beneficial immune responses (Kerkar and Restifo, 2012). Many of the immune escape mechanisms are based on the induction of what we presume is an inappropriate immune response, i.e., a response that does not inhibit but perhaps even promotes the tumor (Grivennikov et al., 2010). Indeed, virtually all solid tumors contain infiltrates of diverse leukocyte subsets including both myeloid- and lymphoid-lineage cells, whose profile and activation status vary depending on the tissue/organ milieu as well as stage of malignancy. Notably, in some tumors these inflammatory infiltrates are similar in their effect to the resolution phase of wound healing, i.e., they contain immune-competent cells that convey immunosuppressive activity (Hanahan and Coussens, 2012). These
congregations include regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), type 2 tumor-associated macrophages, neutrophils, and mast cell subtypes; these cells may collectively or alone enable cancer cells to escape killing by cytotoxic cells (Sakaguchi et al., 2008; Qian and Pollard, 2010; Kodumudi et al., 2012) (Figure 1). Thus, ablation or reprogramming of this aberrant microenvironment might dramatically augment cancer therapies, and this strategy is currently being deployed in a variety of clinical trials (Mellman et al., 2011; Wang et al., 2012). Since the rediscovery of suppressor T cells as CD4 þ CD25 þ regulatory T cells, this cell subset has become an intense focus of cancer research (Sakaguchi et al., 2008). Tregs can develop in the thymus or can be converted in the periphery by, for example, exposure to transforming growth factor (TGF)-b. Both ‘natural’ and ‘inducible’ Tregs utilize similar mechanisms to mediate immune suppression: (i) secretion of immunesuppressive cytokines, e.g., TGF-b, IL-35, and IL-10; (ii) direct killing of effector T cells; (iii) metabolic commotion, e.g., IL-2 deprivation; and
1
Division of General Dermatology, Department of Dermatology, Medical University of Graz, Graz, Austria
Correspondence: Division of General Dermatology, Medical University of Graz, Auenbruggerplatz 8, Graz A-8036, Austria. E-mail: [email protected]
1462 Journal of Investigative Dermatology (2013), Volume 133
approach using embedded materials with well-defined elastic moduli, and at controlled depths within a phantom matrix, must also be undertaken. Furthermore, the experimental measurements must be used to validate computational models of these same scenarios, as in the study conducted by Roduit et al. (2009). When such data are forthcoming and a platform of confidence in the approach has been firmly established, then the pursuit of more intricate relationships, such as the depth dependence of filaggrin degradation suggested by Beard et al. (2013), ought to be possible. By undertaking parallel electrophysiology on targeted structures during the nanoindentation process, perhaps by the implementation of recent microfabrication innovations for intra-cellular recording (Duan et al., 2011), a realtime assessment of membrane trafficking can also be undertaken during the critical bulk penetration stage, which will inform on downstream viability profiles. The emergence of the new tomography technique is also rather timely: researchers will not have to go through the trouble and expense involved in generating their own ‘nano-needle’ tips, as commercially available entities have already emerged (viz NaugaNeedles.com or www.Nanotools.com for example). It would thus seem that the only short-term limitation with local probe tomography will rest in the collective imagination of its first wave of users. CONFLICT OF INTEREST
MCF7 human breast cancer cells. Proc. 15th European Microscopy Congress. Manchester Duan X, Gao R, Xie P et al. (2011) Intracellular recordings of action potentials by an extracellular nanoscale field-effect transistor. Nat Nanotechnol 7:174–9 Dulinska-Molak I, Lekka M, Lewandowska M et al. (2012) Preliminary studies on the characteristics of corneocytes using atomic force microscopy (AFM). Pol J Cosmetol 15:50–7 Gaikwad RM, Vasilyev SI, Datta S et al. (2010) Atomic force microscopy characterization of corneocytes: effect of moisturizer on their topology, rigidity, and friction. Skin Res Technol 16:275–82
O’Connor SD, Komisarek KL, Baldeschwieler JD (1995) Atomic force microscopy of human hair cuticles: a microscopic study of environmental effects on hair morphology. J Invest Dermatol 105:96–9 Pesen D, Hoh JH (2005) Micromechanical architecture of the endothelial cell cortex. Biophys J 88:670–9 Plodinec M, Loparic M, Monnier CA et al. (2012) The nanomechanical signature of breast cancer. Nat Nanotechnol 7:757–65 Roduit C, Sekatski S, Dietler G et al. (2009) Stiffness tomography by atomic force microscopy. Biophys J 97:674–7
See related article on pg 1582
Circulating Melanoma Cells as a Predictive Biomarker Giorgos Karakousis1, Ruifeng Yang2 and Xiaowei Xu2 The prognosis of patients with metastatic melanoma has improved significantly with targeted therapeutic agents and immunotherapies. Detection of early melanoma recurrence after treatment will be beneficial to switch patients who fail on one therapy to different modalities. Circulating tumor cells (CTCs) are cancer cells released by a tumor into the peripheral blood. These cells hold potential as prognostic, predictive, and pharmacodynamic biomarkers for treatment. In this issue, Khoja et al. report that melanoma CTCs can be detected using Melcam and high molecular weight melanoma–associated antibody. They found that in 101 stage IV melanoma patients, CTC numbers ranged between 0 and 36/ 7.5 ml blood; 26% of the patients had X2 CTCs at baseline. The CTC number (X2 CTCs) at baseline was significantly prognostic for median overall survival (OS) in univariate and multivariate analysis. Patients receiving treatment where CTC numbers remained X2 CTCs during their treatment had shorter median OS than those who maintained o2 CTCs (7 vs. 10 months, hazard ratio 0.34, 95% confidence interval 0.14–0.81, log-rank test P ¼ 0.015). The implications of this work are substantial in counseling patients about their prognosis and in helping to assess responses to systemic therapies. Journal of Investigative Dermatology (2013) 133, 1460–1462. doi:10.1038/jid.2013.34
The authors state no conflict of interest.
REFERENCES Beard J (2011) Electron beam deposited nanotools for nanomanipulation and biological applications. PhD Thesis. University of Bath: Bath, UK Beard JD, Guy RH, Gordeev SN (2013) Mechanical tomography of human corneocytes with a nanoneedle. J Invest Dermatol 133:1565–71 Bhushan Bharat (2012) Nanotribological and nanomechanical properties of skin with and without cream treatment using atomic force microscopy and nanoindentation. J Colloid Interface Sci 367:1–33
Targeted therapies such as the mutant BRAF selective inhibitors vemurafenib and dabrafenib have improved the survival of patients with metastatic melanoma (Flaherty et al., 2010, 2012a,b; Sosman et al., 2012). However, subsequent drug resistance and disease progression has been observed in most of the treated patients (Flaherty, 2012).
Anti-CTLA4 and anti-PD1 immunotherapies have also improved overall survival (OS) in metastatic melanoma patients, with a subset of patients having long-term survival (Hodi et al., 2010; Lipson et al., 2013). With effective therapies of this sort, it has become important to monitor patients and to identify early signs of treatment failure.
Binnig G, Rohrer H (1987) Scanning tunneling microscopy from birth to adolescence. Rev Mod Phys 59:615–25
1
Conneely M, Rolfsnes H, McGloin D et al. (2012) Influence of ultrasound exposure on cellmechanical properties: a preliminary study on
Correspondence: Xiaowei Xu, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA. E-mail: [email protected]
Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA and 2Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
1460 Journal of Investigative Dermatology (2013), Volume 133
COMMENTARY
Clinical Implications
Melanoma circulating tumor cells (CTCs) can be detected using antibodies against melanocyte surface markers.
In multivariate analysis CTC number (X2 CTCs) is an independent prognostic biomarker of overall survival (OS).
Patients receiving treatment where CTC number remained X2 CTCs during treatment had shorter median OS than those who maintained o2 CTCs.
However, detection of early recurrence and treatment failure is difficult, and obtaining tumor biopsies is not without risk. Less invasive approaches to assess treatment responses would therefore have clinical utility. During tumor progression, a subpopulation of tumor cells gain access and escape into the lymphatic or blood vessels and circulate until they are either eliminated by host response mechanisms or find an microenvironment in which to reside where they may eventually proliferate. In our own work, we found that lymphatic invasion occurs commonly in primary melanomas (Xu et al., 2008, 2012). Importantly, the detection of circulating tumor cells (CTCs) in the peripheral blood of patients with cancer has prognostic and therapeutic implications (Cristofanilli et al., 2004). However, the number of CTCs can be very small, and these cells are not easily detected. Therefore, a key to the use of CTCs as a biomarker is technology designed to enrich cancer cells from peripheral blood. FDA has approved the Veridex CellTrack Analyzer for use in monitoring therapeutic responses in patients with breast, prostate, or colon cancer. This technology relies on the expression of epithelial cellular adhesion molecular (EpCAM). Most CTC studies in the literature have focused on epithelial cancers. In the study reported by Khoja et al. (2013), the authors used a melanomaspecific CellSearch CTC kit, using Melcam and high molecular weight melanoma associated antibody (HMWMAA), which is also identified as a melanoma-associated chondroitin sulfate proteoglycan antibody for melanoma CTC capture and detection. Both
markers are reported to be expressed in up to 80% of metastatic melanoma lesions (Campoli et al., 2004). The authors found that 40% of melanoma patients in a cohort of 101 have one or more CTCs at baseline, with nearly 79% having advanced M1c disease. In patientso60 years of age, the sensitivity of CTCs above 0 was 33%. Using the threshold of X2 CTCs, which the authors proposed as useful, 26% of the patients fell into this category. Multivariate Cox proportional hazards regression analysis demonstrated that, after adjusting for other significant univariate factors, such as lactate dehydrogenase, performance status, treatment with a BRAF or MEK inhibitor, CTC number was an independent prognostic factor for OS (hazard ratio (HR) 2.403, 95% confidence interval (CI) 1.303–4.430, P ¼ 0.005). Although melanoma CTCs identified by Melcam and HMW-MAA indeed did identify a cohort of patients with extremely poor prognosis, the remaining cohort (74%) still had a relatively poor outcome with a median OS of only 7.2 months. Thus, it is conceivable that a majority of stage M1c melanoma patients have CTCs in their peripheral blood; however, these CTCs are not detectable by the combination of Melcam and HMWMAA antibodies. As pointed out by the authors, the level of antigen expression on melanoma cells in the circulation is unknown, especially with respect to the detection limits of the Veridex platform. CTCs may therefore have different surface antigen characteristics than do the corresponding tissue metastases. Low melanocytic marker expression on CTCs may be one of the reasons why the majority of their patients (75%) had
o2 CTCs and 60% had no CTCs. Therefore, other melanocytic markers should be tested to optimize detection of melanoma CTCs. The authors also explored the pharmacodynamic CTC changes and prognostic significance of CTC number after treatment. Although the sample size is relatively small (28 of 45 patients exhibited pharmacodynamic changes in CTC number), the prognostic significance of CTC number recorded before and at any time point during treatment for all 45 patients confirmed longer survival for patients with o2 CTCs at any time point during treatment (10 vs. 7 months, HR 0.34, CI 0.14–0.81, log-rank test P ¼ 0.015). As CTCs were measured at 6–9 weeks post initiation of treatment in the current study, it would be interesting to measure the CTC number at very early time points after initiation of therapy, to see if clinical responses could be predicted prior to their occurrence. Nevertheless, the implications of this work are significant both for counseling patients on prognosis and also for helping to assess the response to systemic therapies. Despite the progress of research on CTCs, the biology of CTCs needs to be further characterized. It is still unclear whether CTCs are similar to the bulk of tumor cells in the primary site or to solid metastases, whether they represent the so-called ‘‘tumor-initiating cells’’, and whether there is heterogeneity among CTCs in an individual patient on the molecular level. More studies are needed to address these important issues. Summary
The work by Khoja et al. (2013) imparts important insights into the melanoma biology. The investigators provide evidence that melanoma CTCs can be detected using antibodies against melanocyte surface markers. CTC number (X2 CTCs) is an independent worse prognostic biomarker of OS. Patients receiving treatment where CTC number remained at X2 CTCs during treatment had a shorter median OS than those that maintained o2 CTCs. Their work generates further impetus for studies aimed at increasing the sensitivity of melanoma CTC detection www.jidonline.org 1461
COMMENTARY
and at addressing whether melanoma CTCs can help serve as predictive biomarkers for risk stratification of patients for clinical treatments and for early prediction of response to therapies. CONFLICT OF INTEREST
The authors state no conflict of interest.
See related article on pg 1610
The Dark Side of Cyclophosphamide: Cyclophosphamide-Mediated Ablation of Regulatory T Cells Ju¨rgen C. Becker1 and David Schrama1
ACKNOWLEDGMENTS The writing of this Commentary was made possible in part by research grants from the NIH grant R01AR054593.
REFERENCES Campoli MR, Chang CC, Kageshita T et al. (2004) Human high molecular weight-melanomaassociated antigen (HMW-MAA): a melanoma cell surface chondroitin sulfate proteoglycan (MSCP) with biological and clinical significance. Crit Rev Immunol 24:267–96 Cristofanilli M, Budd GT, Ellis MJ et al. (2004) Circulating tumor cells, disease progression, and survival in metastatic breast cancer. N Engl J Med 351:781–91 Flaherty KT (2012) Targeting metastatic melanoma. Annu Rev Med 63:171–83 Flaherty KT, Infante JR, Daud A et al. (2012a) Combined BRAF and MEK inhibition in melanoma with BRAF V600 mutations. N Engl J Med 367:1694–703 Flaherty KT, Puzanov I, Kim KB et al. (2010) Inhibition of mutated, activated BRAF in metastatic melanoma. N Engl J Med 363:809–19 Flaherty KT, Robert C, Hersey P et al. (2012b) Improved survival with MEK inhibition in BRAF-mutated melanoma. N Engl J Med 367:107–14 Hodi FS, O’Day SJ, McDermott DF et al. (2010) Improved survival with ipilimumab in patients with metastatic melanoma. N Engl J Med 363:711–23 Khoja L, Loriqan P, Zhou C et al. (2013) Biomarker utility of circulating tumour cells in metastatic cutaneous melanoma. J Invest Dermatol 133:1582–90 Lipson EJ, Sharfman WH, Drake CG et al. (2013) Durable cancer regression off-treatment and effective re-induction therapy with an antiPD-1 antibody. Clin Cancer Res 19:462–8 Sosman JA, Kim KB, Schuchter L et al. (2012) Survival in BRAF V600-mutant advanced melanoma treated with vemurafenib. N Engl J Med 366:707–14 Xu X, Chen L, Guerry D et al. (2012) Lymphatic invasion is independently prognostic of metastasis in primary cutaneous melanoma. Clin Cancer Res 18:229–37 Xu X, Gimotty PA, Guerry D et al. (2008) Lymphatic invasion revealed by multispectral imaging is common in primary melanomas and associates with prognosis. Hum Pathol 39:901–9
Cancer immune escape is frequently associated with the induction of an inappropriate immune response, i.e., a response that does not inhibit but perhaps even promotes the tumor. Indeed, increased frequencies of tumor-infiltrating regulatory T cells (Tregs) are associated with an impaired prognosis in several cancers. Thus, depletion of Tregs, e.g., by cyclophosphamide, was proposed as a means to boost immune responses to cancer. In the present issue of the Journal, Sevko et al., however, provide evidence that cyclophosphamide exerted the unexpected effect of induction of myeloid-derived suppressor cells. Journal of Investigative Dermatology (2013) 133, 1462–1465. doi:10.1038/jid.2013.67
Malignant cells can be detected and destroyed by cells of the immune system in general, and by cells of the adaptive immune system in particular. In fact, there is strong evidence that immunological recognition has an impact on prognosis (Mellman et al., 2011; Wang et al., 2012). Nevertheless, there is equally strong evidence that in many cancer patients the cancerous cells impair beneficial immune responses (Kerkar and Restifo, 2012). Many of the immune escape mechanisms are based on the induction of what we presume is an inappropriate immune response, i.e., a response that does not inhibit but perhaps even promotes the tumor (Grivennikov et al., 2010). Indeed, virtually all solid tumors contain infiltrates of diverse leukocyte subsets including both myeloid- and lymphoid-lineage cells, whose profile and activation status vary depending on the tissue/organ milieu as well as stage of malignancy. Notably, in some tumors these inflammatory infiltrates are similar in their effect to the resolution phase of wound healing, i.e., they contain immune-competent cells that convey immunosuppressive activity (Hanahan and Coussens, 2012). These
congregations include regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), type 2 tumor-associated macrophages, neutrophils, and mast cell subtypes; these cells may collectively or alone enable cancer cells to escape killing by cytotoxic cells (Sakaguchi et al., 2008; Qian and Pollard, 2010; Kodumudi et al., 2012) (Figure 1). Thus, ablation or reprogramming of this aberrant microenvironment might dramatically augment cancer therapies, and this strategy is currently being deployed in a variety of clinical trials (Mellman et al., 2011; Wang et al., 2012). Since the rediscovery of suppressor T cells as CD4 þ CD25 þ regulatory T cells, this cell subset has become an intense focus of cancer research (Sakaguchi et al., 2008). Tregs can develop in the thymus or can be converted in the periphery by, for example, exposure to transforming growth factor (TGF)-b. Both ‘natural’ and ‘inducible’ Tregs utilize similar mechanisms to mediate immune suppression: (i) secretion of immunesuppressive cytokines, e.g., TGF-b, IL-35, and IL-10; (ii) direct killing of effector T cells; (iii) metabolic commotion, e.g., IL-2 deprivation; and
1
Division of General Dermatology, Department of Dermatology, Medical University of Graz, Graz, Austria
Correspondence: Division of General Dermatology, Medical University of Graz, Auenbruggerplatz 8, Graz A-8036, Austria. E-mail: [email protected]
1462 Journal of Investigative Dermatology (2013), Volume 133