Inhibition of mammary and urinary bladder carcinogenesis by a retinoid and a maleic anhydride-divinyl ether copolymer (MVE-2).

N-(4-hydroxyphenyl)retinamide (4-HPR), a synthetic retinoid, and MVE-2, a maleic anhydride-divinyl ether copolymer, were both effective inhibitors of mammary carcinogenesis induced in Sprague-Dawley rats by N-methyl-N-nitrosourea and of urinary bladder carcinogenesis induced in C57BL/6 x DBA/2F1 mice by N-butyl-N-(4-hydroxybutyl)-nitrosamine. However, combined administration of 4-HPR and MVE-2 was no more effective in cancer inhibition than was either agent alone. Retinoids and maleic anhydridedivinyl ethers may exhibit a mechanistic or metabolic antagonism which precludes an additive or synergistic interaction in inhibiting chemical carcinogenesis.