Tetramodality treatment of human melanoma in vitro

We evaluated the in vitro cytotoxic effects of combined human tumour necrosis factor alpha (TNF), human Interferon gamma (IFN-γ), melphalan (L-PAM) and hyperthermia (HTX) on human melanoma cell lines using the crystal violet assay. HTX (40°C, 1 h) alone had no effect. The responses of the cell lines to TNF were in the rank order of 939 cells > 987 > 284 > C8161 > 852 > A2058 ~0, and all displayed shallow dose-response curves; no significant thermal enhancement of TNF cytotoxicity was apparent with this heat dose. All cell lines were sensitive to L-PAM, with 284 cells being the most sensitive; HTX caused only slightly increased sensitization to L-PAM. The combination of TNF and L-PAM resulted in generally subadditive or additive cytotoxicity, with or without HTX. The response to IFN-γ alone was heterogeneous; the 939,284 and 852 cell lines were sensitive to a dose as low as 20 ng/ml, whereas the 987 line was resistant to 2.0 μg/ml, even with HTX. IFN-γ enhanced the response to TNF only of the TNF-resistant A2058 cell line, but there was no enhancement of the response to L-PAM for any line. Thus, this tetramodality combination achieved generally subadditive or additive cytoxicity in vitro.