[Anti-tumor effects of carmofur on human 5-FU resistant cells].

As a part of studies to clarify the efficacy mechanism of carmofur (HCFU), a 5-FU analog, the degree of cross-resistance to HCFU of cell lines of cultured human colon cancer DLD-1 and a stomach cancer NUGC-3, both of which had acquired resistance to 5-FU, was studied in vitro and in vivo. In vitro, both resistant cell lines showed no or little cross-resistance to HCFU under a short-term drug exposure, and very low cross-resistance to HCFU, as compared to resistance to 5-FU, under a long-term drug exposure. In therapeutic experiments using nude mice bearing parent or subcutaneously transplanted 5-FU-resistant DLD-1 cells, HCFU exerted almost the same growth-inhibitory effects on both tumors. These results suggest that HCFU itself may have its own anti-tumor mechanism, different from that of 5-FU.