Expression of differentiation melanoma-associated antigen genes is associated with favorable disease outcome in advanced-stage melanomas.

Cutaneous melanomas have been found to express several immunogenic differentiation melanoma-associated antigens (MAAs) that have been suggested to play an important role in disease outcome. Adaptive host immunity to MAAs has shown some level of control on melanoma progression. To date, there has been no definitive report correlating the level of differentiated MAAs gene expression in melanomas with overall disease outcome. Metastasis of melanoma to distant visceral organ sites usually indicates a survival of less than 1 year; however, a subset of patients who undergo cytoreductive surgery of distant metastases survive for a longer period. We hypothesized that the gene expression level of differentiation MAAs in metastatic melanoma (AJCC stage IV) lesions would be predictive of survival. We focused on three known differentiation MAAs: tyrosinase (TYR), TYR-related protein 2 (TRP-2), and melanoma antigen recognized by T cells 1 (MART-1); all three of them are known to induce immune responses in melanoma patients and are frequently expressed in melanomas. A quantitative reverse-transcriptase RealTime PCR (qRT) assay was developed for these MAAs to assess mRNA expression in metastatic melanoma tumors obtained from cytoreductive surgery of AJCC stage IV melanoma patients (n = 35). Patients were followed up for over 60 months. There was a variation in mRNA copy levels for individual MAAs in melanoma tumors. Elevated MAA mRNA copy levels of TYR and TRP-2 significantly (P < 0.03 and < 0.009, respectively) correlated with improved overall survival. Patients having at least one MAA expressed in their tumors had a significantly (P = 0.01) better overall survival (median 16 months). These studies demonstrate that levels of differentiated MAA mRNA expression of advanced-stage metastatic melanomas can be used as molecular predictive factors of disease outcome. The studies also imply that an assessment of melanoma tumor MAAs may provide a stratification factor targeted for active-specific immunotherapy.