Four permanent strains of human malignant melanoma, derived from a single melanoma nodule in one patient, exhibited different survival responses to the S-phase-specific drug, arabinosylcytosine. In one strain, survival was reduced by a fraction equivalent to the proportion of cells in S phase. The other three stains were much more resistant to drug doses as high as 100 µg/ml treated for 1 hr; however, treatments of longer duration (up to 8 hr) did cause a reduction in the surviving fraction of one resistant strain tested. Different mechanisms of cell killing by arabinosylcytosine may be responsible for the differential responses observed in these four melanoma strains.


Supported by Damon Runyon Memorial Cancer Fund 1059 and Contract PH 43-66-1156, Chemotherapy, National Cancer Institute, NIH, USPHS.

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