No abstract

Human malignant melanoma is highly resistant to chemotherapy and current immunotherapeutic approaches induce long term remission only in the minority of patients. The transforming growth factor-β (TGF-β) has attracted much attention as a therapeutic target because it plays an important and pleiotropic role in melanoma progression. TGF-β is a multifunctional cytokine involved in the regulation of many cellular processes including cell proliferation, differentiation and survival. Resistance to the growth inhibitory effects of TGF-β without alterations of TGF-β signaling molecules is characteristic of cutaneous melanoma. Melanoma produces increasing amounts of TGF-β with disease progression, inhibiting immune responses and providing an optimal microenvironment for undisturbed tumor growth. In addition, TGF-β exerts its tumor promoting functions via direct effects on tumor cell motility and invasiveness and indirectly by modulating tumor stroma and extracellular matrix, supporting angiogenesis and inhibiting immune surveillance. TGF-β acts through multiple intracellular signaling pathways and the outcome of TGF-β signaling is context-dependent. Defining the impact of the different TGF-β signaling pathways on melanoma progression will help to identify suitable therapeutic targets. Here we review the current knowledge of TGF-β in melanoma and discuss recent therapeutic approaches targeting the TGF-β pathway.

Different molecular markers have been identified for melanoma-initiating cells including CD133 and nestin. Assuming that metastasis requires a dissemination of tumor-initiating cells, presence of circulating tumor-initiating cells should be associated with worse patient outcome. In this study, 20 ml blood was collected from 32 consecutive patients affected by metastatic melanoma and blood was enriched for circulating melanoma cells (CMCs) by CD45 depletion of the non-melanoma cell fraction. Multiparameter cytometry was carried out to co-stain with combinations of CD133 and nestin (NES). Six tissue samples from metastatic lesions of six different patients were stained with the same antibodies by immunohistochemistry. Percentage of NES-positive CMCs correlated with tumor burden and number of metastatic sites. Cox regression analysis revealed levels of lactate dehydrogenase (LDH; hazard ratio: 12.8 (1.35-121.5); P=0.02), number of metastatic sites (hazard ratio 3.87 (1.66-9.03); P=0.02), tumor burden (hazard ratio 5.72 (1.57-20.9); P=0.01), and percentage of NES-expressing CMCs ≥ 35% (hazard ratio 5.73 (1.66-19.7); P=0.006) to be factors related to shorter overall survival. CD133- and NES-expression profiles on CMCs were similar to matched metastatic tissue. These findings show that CMCs expressed stem cell-associated markers NES and CD133. Higher expression of NES on CMCs might represent an index of poor prognosis.

Purpose: The aim of this study was to determine in patients with high-risk primary uveal melanoma whether the detection of circulating tumor cells by quantitative reverse transcription-PCR (RT-PCR) is of prognostic relevance. Experimental Design: Blood samples from 110 patients with high-risk nonmetastatic uveal melanoma were collected on the occasion of primary treatment or follow-up visit. mRNA expression of tyrosinase and MelanA/MART1 were analyzed by real-time RT-PCR and compared with clinical data at presentation and follow-up by univariate and multivariate analyses. Results: The RT-PCR assay yielded a positive result in 11 of 110 patients, with five positive findings for tyrosinase and five for MelanA/MART1, and one sample positive for both markers. At a median follow-up of 22 months, 25% of patients had developed metastases and 15% had died. Univariate statistical analysis revealed RT-PCR and the largest tumor diameter as important prognostic factors for the development of metastases and for survival. In a Cox proportional hazard model, RT-PCR result and largest tumor diameter predicted metastases (hazard ratios 7.3 and 2.6, respectively), whereas PCR result, largest tumor diameter, and Karnofsky performance status were significant variables for disease-specific survival (hazard ratios 22.6, 4.7, and 6.0, respectively). Analysis of individual RT-PCR results revealed both tyrosinase and MelanA/ MART1 transcripts as independent prognostic factors. Conclusion: The presence of tyrosinase or MelanA/MART1 transcripts is an independent prognostic factor in patients with high-risk primary uveal melanoma for subsequent development of metastases and for survival and can be used to select patients for adjuvant treatment studies.A major problem with uveal melanoma is the development of systemic metastases, which occur in up to 35% of cases even after successful treatment of the primary tumor (1 -6). The survival rate of patients with metastatic uveal melanoma remains poor with a median of between 2 and 9 months in spite of a variety of systemic therapeutic approaches (5, 7 -9). There is an urgent need to define risk factors for systemic metastasis to evaluate novel adjuvant treatments for high-risk patients.Several clinical, histologic, and genetic factors (e.g., tumor size and monosomy 3) have been identified as important risk factors for local recurrence, development of metastases, and survival (5, 6, 10 -15). However, histologic and genetic predictive factors are not usually identified because most patients with uveal melanoma are treated with radiotherapy (6,16,17). It is therefore necessary to rely on clinical features, such as largest basal tumor diameter, ciliary body involvement, and extraocular growth, which have firmly been established as important clinical prognostic factors by the Collaborative Ocular Melanoma Study (COMS; ref. 6).The detection of disseminated tumor cells in the blood by reverse transcription-PCR (RT-PCR) is particularly relevant to uveal melanoma, which metastasizes early and ex...