Platinum anticancer drugs modulate P-450 mRNA levels and differentially alter hepatic drug and steroid hormone metabolism in male and female rats.

Treatment of male rats with the anticancer drug cisplatin leads to feminization of the profile of cytochrome P-450 and other microsomal enzymes involved in steroid hormone and drug metabolism (G.A. LeBlanc, and D.J. Waxman, J. Biol. Chem., 263: 15732-15739, 1988). The present study uses the rat model to evaluate the differential effects of cisplatin treatment on liver microsomal enzymes between genders, and also examines whether the modulation of enzyme activities by cisplatin and its analogues involves changes in P-450 gene expression. While cisplatin treatment of male rats caused a severalfold increase in female-predominant hepatic enzymes, including testosterone 5 alpha-reductase and testosterone 7 alpha-hydroxylase (P-450 form 2A1), it partially decreased the expression of these enzymes in females. The reduced expression of these estrogen-dependent enzymes in females may derive from the loss of circulating estradiol that was shown to occur in response to cisplatin treatment. Analysis of mRNA levels of individual P-450 forms revealed that the effects of cisplatin on P-450-catalyzed steroid hydroxylase activities in both male and female rats are primarily operative through the drug's effects on P-450 mRNA expression. P-450-dependent cyclophosphamide activation was significantly compromised in male rats after cisplatin administration; however, this activity was not altered in cisplatin-treated females. This sex-dependent effect of cisplatin was due to its suppression of P-450 form 2C11, a male-specific P-450 that is a major contributor to microsomal cyclophosphamide bioactivation in male rat liver. The clinically active cisplatin analogue iproplatin elicited effects very similar to those of cisplatin, while carboplatin and transplatin did not have significant effects on hepatic P-450 expression. Together, these findings demonstrate that the response of rat liver to cisplatin-induced changes in hepatic P-450 enzyme profiles and cyclophosphamide bioactivation capacity differs between the sexes, and in addition, these effects can be minimized by use of carboplatin in place of cisplatin.