nteraction between Fibroblast Growth Factor Receptors (FGFR) and Progesterone Receptors (PR) in experimental breast cancer

CERLIANI, JUAN PABLO; LAMB, CAROLINE A.; LANARI, CLAUDIA

Denver, Colorado, USA

Congreso; American Association for Cancer Research; 2009

AACR

We have developed a murine model of breast cancer progression in which ductal, hormone-dependent (HD) carcinomas transit through different stages of hormone responsiveness retaining the expression of high levels of estrogen (ER) and progesterone receptors (PR). Unlike HD carcinomas, hormone-independent (HI) tumors do not need the exogenous administration of medroxyprogesterone acetate (MPA) to grow. In vitro, however, there are no differences in hormone responsiveness between both types, suggesting the involvement of host factors regulating in vivo tumor growth. We have previously observed a) an increase in FGFR (1-4) expression, mainly FGFR-2 and -3, in HI tumors and in HD tumors growing with MPA as compared with untreated HD tumors; b) higher levels of FGF-2 in stroma from HI tumors; c) that the pharmacological or genetic blockage of FGFR-2 with antiprogestins or SiRNA respectively, inhibited the stimulation induced by carcinoma associated fibroblasts on epithelial cell growth. We hypothesize that the stroma from HI tumors participates regulating HI tumor growth by releasing FGF-2 that acts as a paracrine growth factor which activates FGFR-2 in the epithelial cells, which in turn activates PR. The aim of this study was to evaluate a direct interaction between PR and FGFRs using our murine tumor model and human T47D cells. Purified epithelial cells of C4-HI or T47D cells were seeded in chamber slides and after few days of culture, they were starved in 1% charcoalized fetal calf serum and treated with FGF-2 (50 ng/ml), MPA (10-8M) or vehicle for different periods of time. Confocal imaging showed an intimate interaction between FGFR-2 and PR when the cells (C4-HI or T47D) were treated with FGF-2 or MPA. Under these experimental conditions there was almost no interaction between PR and FGFR-1, FGFR-3 or FGFR-4 (p<0.05). We showed that the peak of co-localization was observed after 20 min of incubation (p<0.05) with MPA and 1 hour with FGF-2 in C4-HI cells or 20 min. with both treatments in T47D (p<0.05). Inmunoprecipitation assays using C4-HI and T47D cells confirmed confocal observations. In time course experiments (5, 10, 30 min., and 1 hour incubation with FGF-2 50 ng/ml or MPA 10-8M) we have also observed that the increased pSer190 phosphorylation of PR in both cell types correlated with an activation of Erk and Akt pathways, an increase in c-Myc expression and early phosphorylation of Stat-5 in both models. These results show for the first time nuclear interactions between FGFR-2 and PR in two different breast cancer models suggesting that Stat 5 may be implicated in this interaction. In addition, these data are in agreement with our hypothesis regarding FGF-2 activating FGFR-2 in epithelial cells as a mechanism of PR ligand independent activation indicating that FGFR, are potential targets in the treatment of hormone related breast cancer.