Heterogeneity and phenotypic instability of chemotherapeutic and immunologic sensitivity in murine and human melanoma cell clones.

The aim of the present study was to examine the phenotypic heterogeneity of murine and human melanoma cell lines with particular reference to anticancer drug sensitivity, growth pattern and susceptibility to lysis by lymphokine (rIL2) activated killer (LAK cells). Clones selected for a different drug sensitivity were tested to evaluate the stability of such properties after different in vitro passages. A possible relationship between drug sensitivity and LAK susceptibility was also analyzed. The results indicated a high heterogeneity in murine and in human melanoma clones for all the parameters. However, drug sensitivity, which was stable although for only a few passages in an untreated human melanoma, was highly unstable in murine naturally or drug-induced resistant cells. Finally, whereas human drug-resistant clones were sensitive to lysis by LAK cells and an inverse correlation was found with the level of drug resistance, murine clones appeared to be LAK sensitive, and no correlation was found between the level of drug resistance and LAK sensitivity. Our data indicate a different stability in drug response of human and murine cells and a different behaviour of human and murine drug-resistant cells in response to LAK lysis.