Increase cyclin A expression is associated with antiprogestin resistance and progesterone receptor isoforms ratio in experimental models of breast cancer

BRITTA M. JACOBSEN; VICTORIA T. FABRIS; MELINA E. BILINSKI; CLAUDIA LANARI; MARINA AYRE

Conferencia; AACR Special Conference on Advances in Breast Cancer Research; 2017

American Association for Cancer Research

Deregulation of cyclin A expression has been associated with prognosis and tamoxifen responsiveness in breast cancer. We have previously reported an overexpression of cyclin A in two antiprogestin resistant tumors derived from a hormone dependent mammary carcinoma induced by medroxyprogesterone acetate (MPA). MPA-induced tumors show high levels of estrogen (ER) and progesterone receptors (PR) and transit through different stages of hormone dependency. Taking into account that antiprogestin sensitive tumors show higher levels of PR isoform A (PRA) than isoform B (PRB), and that the opposite ratio is observed in the antiprogestin resistant tumors, we decided to examine the expression of cyclin A in other experimental models containing different PRA/PRB ratios. An increase in cyclin A expression was observed by Western blot (WB) in the acquired antiprogestin resistant variant C7-2-HIR and in the constitutive resistant C7-HI tumor (1.7 fold and 1.5 fold, respectively) compared to the antiprogestin responsive tumor C7-2-HI (p