Response to X-radiation and cytotoxic drugs of clonal subpopulations of different ploidy and metastatic potential isolated from RIF-1 mouse sarcoma.

Clonal subpopulations of different ploidy values and metastatic capacities, isolated from the RIF-1 mouse sarcoma, have been tested for in vitro X-radiation sensitivity, for in vitro sensitivity to adriamycin and for in vitro and in vivo sensitivity to melphalan and CCNU. Following X-radiation, no consistent differences in the survival curve characteristics (Do and n) of diploid, tetraploid and octoploid cells were observed. In addition no relationship between radiation response and metastatic capacity was observed. For drug response, no marked differences were found in the dose response curves of RIF-1 clones treated in vitro with adriamycin. However, a wide variation in the responses of RIF-1 clones to in vitro melphalan treatment was observed which was independent of both ploidy and metastatic capacity. Although the responses of RIF-1 clones to in vitro CCNU treatment were similarly independent of metastatic capacity, a clear relationship between CCNU sensitivity and ploidy was observed. Thus, all diploid RIF-1 clones were markedly more sensitive to CCNU treatment than either tetraploid or octoploid RIF-1 clones. For both melphalan and CCNU treatment the relative sensitivities in vitro correlated with in vivo sensitivities as assayed by clonogenic cell survival.