[Effect of filipin, a polyene antibiotic, on human tumor cell killing in vitro by peplomycin].

Four kinds of cultured human tumor cell lines sensitive or resistant to bleomycin (BLM) were examined for the effect of filipin, a polyene antibiotic, on peplomycin (PEP)-induced cell killing. Although PEP was more effective than BLM against BLM-resistant HeLa cells (HeLa-BLMr), neoplastic cells derived from salivary gland (HSG) and melanoma cells (MEC), these three cell lines were still at least ten times more resistant to PEP than epidermoid carcinoma cell lines including HeLa cells by comparison of IC50, and showed lower cellular accumulation of 3H-PEP as compared with HeLa cells. When these lines were pretreated with filipin, 3H-PEP accumulation by the cells was increased 1.33-, 2.34-, 1.91- and 1.14-fold in HeLa, HeLa-BLMr, HSG and MEC cells, respectively. Combination use of PEP and filipin resulted in a remarkable enhancement of cytocidal effect in HeLa-BLMr and HSG cells (100- and 25-fold decrease of IC50, respectively), and a slight enhancement in HeLa cells, but not in MEC cells. It is therefore suggested that there are differences among cell types in the potentiation of PEP-induced cell killing by filipin.