Sex differences in the MB49 syngeneic, murine model of bladder cancer.

The MB49 syngeneic, murine model of bladder cancer has been widely used for more than 35 years. In humans, bladder cancer is one third as prevalent in women as in men, with a trend toward lower prevalence in parous compared to nulliparous women. Our objective was to determine if the MB49 bladder cancer model reproduces the sex differences observed in humans, and to determine its sensitivity to testosterone and the pregnancy hormone, human chorionic gonadotropin (hCG). Male and female C57BL/6 mice were implanted with MB49 murine bladder cancer cells, and observed for tumor growth. MB49 dose responses to hCG and dihydrotestosterone were determined in vitro. MB49 tumor growth was significantly greater in male mice than female mice. Pregnancy did not affect MB49 tumor growth in female mice. MB49 cells did not proliferate in response to hCG in vitro and the functional receptor for gonadotropins was absent. Dihydrotestosterone strongly stimulated growth of MB49 cells in vitro. The MB49 murine model of bladder cancer reproduced some aspects of the sex differences observed in humans. Our results suggest that testosterone may stimulate MB49 cell proliferation, which may explain the more rapid MB49 tumor growth observed in male mice.