BMY 25282, a newly designed analogue of
mitomycin C (MMC), was assessed for its non-cross-resistant cytotoxic and biochemical action against MMC-resistant human colon
carcinoma cells. The analogue has an amidine substituted at position 7 of MMC and has a more efficient intracellular activation to its active species than MMC. In this study we demonstrated that
BMY 25282 can overcome MMC resistance in a series of previously described human colon
carcinoma cells resistant to MMC (
Cancer Res., 44: 5880, 1984). The non-cross-resistance of the analogue in the model was confirmed in vivo by treating
tumor xenograft-bearing athymic mice with equitoxic doses of MMC or
BMY 25282. We further investigated the formation of interstrand
DNA cross-link (IDC) formation by
BMY 25282 and MMC. MMC-sensitive cells contained 3 to 8 times as many IDCs as resistant colon
carcinoma cells, while no significant differences in IDCs were found between the MMC-sensitive or -resistant cells incubated with
BMY 25282. When MMC-sensitive or -resistant cells were exposed to the 70% inhibition concentration of either MMC or
BMY 25282, no differences were seen with respect to IDC formation. These studies demonstrate that
BMY 25282 is able to overcome MMC resistance in a series of human colon
carcinoma cells and that IDC formation in the MMC-sensitive or -resistant cells parallels cytotoxicity for both MMC and the analogue.