Adriamycin response of two human tumor xenografts using a double-radiolabel organ culture method

A double-radiolabel method of quantitating drug response in a simple organ culture system was used to study the effects of adriamycin on two human tumor xenografts in vitro. Explants of X56, an adenocarcinoma of colon, and HXG2, an amelanotic melanoma, both maintained by serial transplantation in athymic mice, were sequentially incubated in vitro with 14C-thymidine, one of several concentrations of adriamycin, and then 3H-thymidine. The ratios of second to first radiolabel incorporation declined as a function of adriamycin concentration. HXG2 was significantly more responsive to adriamycin than X56 in the double-radiolabeled assay. Greater sensitivity of HXG2 was confirmed by three additional methods: The human tumor stem cell assay (HTSCA), chemotherapy trials in tumor-bearing athymic mice, and a double-radiolabel protocol in vivo in tumor-bearing athymic mice. An organ culture method of this type may be useful in screening individual patients' tumors for drug resistance.