Cholera‐toxin‐enhanced growth of human breast cancer cell lines in vitro and in vivo: Interaction with estrogen

Abstract

Cholera toxin (which increases intracellular cAMP levels) significantly (p < 0.05) increased the growth of MCF‐7, T47‐D and Hs578T human breast carcinoma cells in vitro. The effect of cholera toxin on growth of MCF‐7 and T47‐D cells was more pronounced in the presence of 17β‐estradiol (pp < 0.05) increased growth of the tumors. Cholera toxin treatments, in addition, significantly (p < 0.05) increased cAMP levels in tumor cells and tumor tissue, in vitro and in vivo, respectively. The results of this study clearly demonstrated that an increase in cAMP levels via cholera toxin treatment causes enhanced growth (in vitro and in vivo) of estrogen‐receptorpositive and ‐negative human breast carcinoma cells and, although estrogen alone was not mitogenic to the estrogen‐receptor‐positive breast carcinoma cells in vitro, the steroid was mitogenic to these cells in the presence of elevated cellular cAMP levels.