3αHP results in suppression and regression of 5αP-induced ER/PR-negative tumors. (A) 3αHP suppresses ER/PR-negative breast cell tumorigenesis in 5αP-pretreated mice. Fourteen mice were treated with 5αP on day -3 and day 11 and then were divided into two groups. One group (Group I) continued to be treated with 5αP, whereas the other group (Group II) was treated with 3αHP on days 27, 36, and 47 (Inset). One mouse from each group was excluded from the final analysis, as explained under Results. The data are presented as the percentage of mice with tumors at termination. (B) 3αHP results in regression of 5αP-induced ER/PR-negative breast cell tumors. Twenty-four mice with MDA-MB-231 cell implants received injections of 5αP on days 0, 20, and 61 (inset); on day 75, the 14 mice with approximately similar-sized small palpable tumors (18 to 34 mm3) were divided into two groups, consisting of seven mice each, which received a single injection of either vehicle (veh) or 3αHP, and the experiment was terminated 24 days later. Bars represent size (mm3; mean ± SEM) of tumors that developed of a total number of mice per treatment (bracketed values), at the start of treatments (day 75, Initial) and at termination (day 99, Final).