Decitabine Up-regulates S100A2 Expression and Synergizes with IFN-γ to Kill Uveal Melanoma Cells

Abstract

Purpose: Metastatic uveal melanoma is resistant to conventional chemotherapy and immunotherapy. In this study, we investigated the responsiveness of uveal melanoma cell lines to IFNs and the hypomethylating agent decitabine. Experimental Design: The uveal melanoma cell lines 92-1, UW-1, OCM-1, and MKT-BR were exposed to varying concentrations of IFN-a, IFN-g, and decitabine, alone and in combination. The effects of decitabine on gene expression were examined using DNA microarray analysis. Results: We found that IFN-g and decitabine induced cell death in uveal melanoma. Whereas a high concentration of IFN-g (1,000 units/mL) was required to induce cell death, we observed a dose-related increase in cell death when decitabine was used at a range of 0.1 to 10 Amol/L. Strikingly, 1 Amol/L decitabine synergized with 10 to 1,000 units/mL IFN-g to induce massive cell death. In contrast, decitabine had no effect on three cutaneous melanoma cell lines and exhibited no synergy with either IFN. In uveal melanoma, decitabine up-regulated the expression of genes involved in growth control and apoptosis and down-regulated genes that have been implicated in the malignant phenotype of cutaneous melanoma. The gene up-regulated to the greatest degree by decitabine and whose expression showed a dose-effect across the three concentrations of decitabine was S100A2, a putative tumor suppressor.The genes modulated by decitabine in uveal melanoma were largely unaffected in cutaneous melanoma. Conclusions: These findings form a basis for testing the decitabine/IFN-g combination in metastatic uveal melanoma and for exploring the role of S100A2 in the susceptibility of uveal melanoma to IFN-mediated cell death.Metastatic uveal melanoma is an aggressive malignancy with a median survival of <6 months (1). Patients with locally advanced primary lesions also have a poor prognosis because up to 50% will subsequently develop disseminated metastases within 10 years (2). Although hepatic metastases can respond partially to intra-arterial chemotherapy or chemoembolization, metastatic uveal melanoma is largely resistant to systemic chemotherapy (3). Immunomodulatory drugs used to treat advanced cutaneous melanoma, including interleukin 2 (IL-2) and IFN-a, have also had very limited activity in uveal melanoma (4).The mechanism underlying the antitumor effect of IFN-a or IL-2 in select patients with advanced cutaneous melanoma remains poorly defined. The association of good outcome with the development of autoimmune breakthrough events (5,6) suggests that overcoming tolerance to self-antigens plays a role in cytokine-mediated antitumor immunity. However, IFN-a and IFN-g can also exert direct antiproliferative and/or proapoptotic effects on cutaneous melanoma cell lines (7, 8), illustrating how certain cytokines can have antitumor effects that are independent of the induction of antigen-specific cellular or humoral immunity.The epigenetic suppression of gene expression through DNA methylation has been linked to the relative resistance of a cuta...

The Roles of S100 Proteins and RAGE in Melanoma

“…We recently confirmed this observation using a panel of 40 stage III and stage IV melanoma tissue samples and we showed a significant reduction in S100A2 mRNA level in both stage III and stage IV compared to the control samples (Leclerc, Heizmann, and Vetter 2009). A role of S100A2 in uveal melanoma was also suggested by a recent study where cotreatment of uveal melanoma cells with decitabine and cell death inducing interferon-γ resulted in a dose-dependent increase in S100A2 expression, both at the transcription and protein level (Gollob and Sciambi 2007). As mentioned earlier, S100A2 locates in the nucleus where its most evident target appears to be p53.…”

Clinically feasible approaches to potentiating cancer cell-based immunotherapies

“…Furthermore, a demethylating agent decitabine has been shown to sensitize melanoma cell lines to the cytotoxic effects of IFNs by inducing the expression of proapoptotic and growth-inhibitory genes. 107 The anti-apoptotic members of the Bcl -2 family are potential targets for immunosensitizing drugs. Bcl -2 is also upregulated in many cancer cells, and inactivating its function may result in a proapoptotic cancer cell inflammatory milieu facilitating cytotoxic activity of vaccine-induced immune cells.…”

Epigenetic Modifications: Therapeutic Potential in Cancer

“…A major disadvantage of 5-azacytidine and 5-aza-2'-deoxycytidine is their instability in neutral aqueous solution and poor pharmacokinetic profile, although 5,6-dihydro-5-azacytidine and 5-fluoro-2'-deoxycytidine have demonstrated high toxicity in several preclinical studies. Another example was a phase 1 study, which showed that decitabine caused grade 4 neutropenia in most interleukin-2 inmelanoma and renal cell carcinoma patients (Gollob and Sciambi 2007). Myelosuppression was also the predominant toxicity observed in a study combining decitabine with carboplatin (Appleton et al 2007).…”