Hormone receptor and FGFR expression in mammospheres of a hormone-dependent murine mammary carcinoma and its hormone independent-variant

GUILLARDOY T; CERLIANI JP; LANARI C

Orlando

Encuentro; 102nd Annual Meeting of the American Association for Cancer Research; 2011

American Asociation for Cancer Research

It has been postulated that breast cancer stem cells (CSC) or progenitor cells express low levels of hormone receptors. Mouse mammary carcinomas induced by medroxyprogesterone acetate (MPA) are maintained by syngeneic transplantation and tumor variants with different hormone responsiveness have been generated. Tumors that only grow with MPA supply are named hormone dependent (HD), and tumors which grow without MPA were defined as hormone independent (HI). The main goal of our project is to study the evolution of the CSC compartment in mouse mammary carcinomas which transit through different stages of hormone dependence, focusing in the profiling of estrogen receptors alpha (ERá), progesterone receptors (PR), and fibroblast growth factor receptors 1-4 (FGFR1-4). Mammary cancer cells can be cultured using different methods: adhered to plastic, in matrigel, in soft agar or in suspension as non adherent spherical clusters of cells named mammospheres. It is accepted that there is an enrichment of the mammary CSC population when cells are grown as mamospheres. We performed primary cell cultures of the C4-HD tumor, a hormone-dependent mouse mammary carcinoma maintained by syngeneic transplantations in MPA-treated BALB/c mice, and of one of its hormone independent variants, C4-HI. Cells were cultured on plastic or as mammospheres. Using flow cytometry we analyzed the expression profile of the surface markers ALDH1 or CD44 and CD24, which have been reported to define the SC subpopulation (CD44High/CD24low/- cells). An increase of the CSC population was observed in both tumors when cultured as mammospheres, as compared with those growing in plastic. However, we did not detect differences between the HD and the HI tumors. Next, we compared the expression of ERá, PR and FGFR1-4 by western blot, using protein extracts of epithelial cells growing as mammospheres or monolayers. Although there were no differences in the expression of PR or ERá in extracts from both culture types, we did observe an increase in the expression of FGFR2 and 4 (p < 0,05) in mammospheres from both tumors. Flow cytometry analysis showed that most of the cells CD24low express PR. Taken together our results suggest that the CSC of this model are progenitor cells that express high levels of ERá, PR, FGFR2 and 4. The high levels of FGFR4 are almost exclusive of cells growing as mammospheres, suggesting that these receptors might be used as a CSC marker in this breast cancer model. It remains to be determined if this high expression is the consequence of the anchorage independent growth. Ongoing studies will reveal the evolution of these progenitor cells in hormone resistant variants.