FGF-2 STIMULATES BREAST CANCER GROWTH ACTIVATING ER AND PR

GUILLARDOY, TOMAS; GOROSTIAGA, MARIA ALICIA; LANARI, CLAUDIA; GIULIANELLI, SEBASTIÁN

San Diego

Congreso; Advances in Breast Cancer Research: Genetics, Biology and Clinical Applications, AACR; 2013

American Association for Cancer Research (AACR)

Estrogen and progesterone receptors (ERa and PR respectively) are prognostic markers and dictate therapeutic decisions in breast cancer patients. Although most of the evidence suggests that estrogens are the major etiological factors in breast cancer, there is experimental and epidemiological data that also points to the involvement of PR in mammary gland carcinogenesis and breast cancer growth. Both ERa and PR are activated by their natural ligands or by ligand-independent pathways. Carcinoma-associated fibroblasts produce growth factors that stimulate epithelial cell proliferation. We have recently demonstrated that Fibroblast growth factor 2 (FGF-2) is able to activate PR and induce progestin-dependent tumor growth. In addition, we have demonstrated an interaction between ERa and PR at the promoters of Cyclin D1 (CCND1) and MYC, which is necessary to mediate progestin-induced gene transcription and cell proliferation. The aim of this study was to evaluate the role of ERa in FGF-2-induced cell proliferation. We used C4-HD and C4-HI tumors from the medroxyprogesterone acetate (MPA)-induced murine breast cancer model and two human cell lines, T47D and MCF-7. The C4-HD tumors only grow with the exogenous administration of progestins or FGF-2. High levels of activated ERa expression were observed in C4-HD tumors growing in NOD/SCID female mice treated with FGF-2 (5 μg/day) or MPA (20 mg/depot). The inhibitor of FGF receptors (PD173074, 25 mg/kg) which inhibits C4-HI tumor growth and PR phosphorylation also reduced the expression and phosphorylation of ERa. FGF-2 (50 ng/ml) stimulated cell proliferation of primary cultures of C4-HD and C4-HI tumor cells, and of T47D and MCF-7 cells. The antiestrogen ICI 182.780 (ICI, 1-100 nM), the FGFR inhibitors (PD 0.1 μM and BGJ398 1 nM), and siRNAs against ERa, all blocked the FGF-2 stimulation in the aforementioned models. An increase in pSer118 and pSer167 ERa, and in the nuclear interaction between ERa with the coactivator AIB1 and with FOXA1, were observed in FGF-2-treated MCF-7 and T47D cells. Moreover, FGF-2 induced an increase in the expression of the estrogen responsive elements (ERE)-Luc reporter, that was blocked by ICI and PD. FGF-2 also mediated the up-regulation of two ERa-regulated genes, MYC and pS2/TFF1, which was inhibited by ICI. Finally, ERa and FOXA1 were recruited to ERE sites at pS2/TFF1 promoter after FGF-2 incubation in MCF-7 cells. Our results indicate that FGF-2 mediates PR and ERa activation in breast cancer cells, suggesting that the combination of antiestrogens, antiprogestins and FGF-2-signaling inhibitors may be an option in selected breast cancer patients.