2-Bromo-α-Ergocryptine (CB-154) and Tamoxifen (ICI 46,474) Induced Suppression of the Genesis of Mammary Carcinomas in Female Rats Treated with 7,12-Dimethylbenzanthracene (DMBA): A Comparison

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Abstract
Daily treatment of female Sprague-Dawley rats with CB-154 (prolactin suppressor) or Tamoxifen (estrogen antagonist) for 33 days before and after 7,12-dimethylbenzanthracene (DMBA) administration reduced (p < 0.05) the incidence of mammary carcinomas by 58 and 49%, respectively. A combination of CB-154 and Tamoxifen further reduced (p < 0.05) mammary carcinoma incidence by an additional 50–59%. Treatment with Tamoxifen for 66 days beginning 33 days after carcinogen treatment reduced (p < 0.05) the incidence of mammary carcinomas by 65%; CB-154 treatment, during the same time period, did not significantly effect the final yield of mammary carcinomas. The combination of Tamoxifen and CB-154 was comparable to Tamoxifen alone in suppressing the incidence of mammary carcinomas in the latter study. These results demonstrate a substantial suppressive and synergistic effect of Tamoxifen and CB-154 in the initiating phases of mammary carcinogenesis while in the early promoting phases of this oncogenic process, short-term treatment with Tamoxifen was superior to CB-154 treatment; no synergism between these clinically important compounds was observed.