The direct and indirect effects of corticosterone and primary adipose tissue on MCF7 breast cancer cell cycle progression.

BACKGROUND: Breast cancer is the second leading cause of cancer-related mortality in women. Glucocorticoids (GCs) have the potential to directly affect breast cancer or indirectly via changes to the tumor growth microenvironment a breast cancer is exposed to. The role of GCs in breast cancer progression by direct and indirect means are not fully understood. AIM: To study the direct and indirect effects of GCs on breast cancer cell cycle regulation.
METHODS: MCF7 breast cancer cells were incubated with increasing concentrations of corticosterone (CORT) to investigate the direct effects. In addition, MCF7 cells were cultured in conditioned media (CM) from primary adipose tissue excised from CORT-supplemented lean and obese male rats.
RESULTS: CORT alone resulted in dose-dependent increases in p27 and hypophosphorylated retinoblastoma protein (Rb) which was accompanied by a reduction in the number of cells in S-phase. CM prepared from adipose tissue overrode these direct CORT effects, suggesting that the tumor growth microenvironment created in the CM dominates MCF7 cell cycle regulation.
CONCLUSIONS: The direct inhibitory effects of CORT on cancer cell cycle progression are largely limited by the hormone's effects on adipose tissue biology.