Combined treatment with Ad-TRAIL and chemotherapy (DTIC and SAHA) in human melanoma cell lines.

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Distant metastases from malignant melanoma are known to be highly aggressive and chemoresistant, we have therefore studied the combinations of traditional and novel chemotherapy and TRAIL gene therapy in melanoma cell lines. Dacarbazine (DTIC) is the only approved treatment for metastatic malignant melanoma today, despite the modest efficacy of this treatment. New classes of drugs, such as histone deacetylase inhibitor (HDACI) are highly relevant as potential new therapy in metastatic melanoma. Moreover, TNF-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that selectively induces apoptosis in tumor cells. However, the possibility for the use of any of these agents as monotherapy is probably limited. In the present study we have evaluated the cytotoxic effects of the combined treatments of full-length TRAIL delivered from an adenoviral vector (Ad-hTRAIL) and DTIC or the HDACI SAHA (suberoylanilide hydroxamic acid), in cell lines established from melanoma patients. Five human melanoma cell lines were treated with Ad-hTRAIL alone or in combination with DTIC or SAHA. Cell growth was measured by MTS-assay 72 hours after the treatment was added, and the results obtained for each treatment group were compared with untreated cells. The combined treatment with DTIC and Ad-hTRAIL effectively reduced the cell growth of four of the five cell lines compared to each treatment used alone. By the use of CalcuSyn software the two treatments proved to act synergistically. The HDACI also facilitated growth inhibition, as the combination of SAHA and Ad-hTRAIL was defined as additive or synergistic in all melanoma cell lines. However, the combination of DTIC and Ad-hTRAIL was more effective than the combination with SAHA and Ad-hTRAIL in the melanoma cell lines tested. Both combination therapies were accompanied by increased apoptosis assayed by increased TUNEL-staining and the effect on specific apoptotic mediators (PARP, caspases, Bid) was investigated. Caspase involvement was also observed by the rescue of the treated cells by the pan-caspase inhibitor z-VAD-fmk. In conclusion, these results suggest that treatment with DTIC and SAHA in combination with TRAIL delivered from an adenoviral vector is effective for the inhibition of melanoma cell growth in vitro. A melanoma-targeted approach for the TRAIL gene therapy will be studied further and evaluated in relevant animal models for the possible use in melanoma patients in the future.