[Inhibitory effects of aromatic retinoic acid analog, administered alone or in combination with mitomycin C, on the in vitro growth of rat bladder carcinoma cells].

The effects of an aromatic retinoic acid analog (Ro 10-9359), its metabolite (Ro 10-1670) and mitomycin C (MMC) on the in vitro growth of rat bladder carcinoma cells, BC50-TC were examined. The growth of the cells treated with 10(-4) M of either of the retinoids for 1 hour was not inhibited. The growth of the cells was inhibited by 37% and 93%, respectively, by the 3-day treatment with Ro 10-9359 and Ro 10-1670, at the concentration of 5 X 10(-5) M. The retinoids given in combination with MMC produced additive effects. Slight synergism was suggested at high concentrations of the retinoid. The fact that the retinoids exhibited anti-tumor activity in vitro might preclude indirect effects from being the only factor in the inhibition of the tumor growth in vivo, but the fact that antagonism with MMC did not occur in vitro whereas it did in vivo suggests that the indirect effects of the retinoid might be more important in mediating the anti-tumor effects. Regardless of the mechanism of action, care should be taken when prescribing retinoids with MMC or other cytotoxic agents.