[Enhancement of the effects of anticancer agents on B16 melanoma cells by combination with cepharanthine--II. Antimetabolite, alkylating agent, nitrosourea].

We have studied chemotherapy enhancement by the combination of the biscoclaurine alkaloid, Cepharanthine (Ceph), using the inhibition of colony forming efficiency (CFE) of B16 melanoma cells in vitro. Hydroxyurea, antimetabolite, showed a time-dependent inhibition of CFE, and the combination with Ceph enhanced CFE inhibition by 29%, which is stable and independent of the treatment time. Dacarbazine, a biological alkylating agent, given with Ceph showed a time-dependent inhibition of CFE (43%). MCNU, a nitrosourea, with Ceph showed the greatest inhibition of CFE (67%) among the anticancer agents used. The CFE inhibition was time-dependent and required a higher concentration of MCNU. In this series of studies using CFE inhibition of B16 melanoma cells in vitro, etoposide showed the best effect by the combination with Ceph, which seems to be a candidate for in vivo evaluation.