Role of progesterone in human astrocytomas growth.

Progesterone (P) participates in the regulation of several reproductive processes such as ovulation and sexual behavior, however, this hormone also participates in non-reproductive processes, such as neural excitability, learning and memory, and pathological processes such as cancer. P mainly elicits its effects by interaction with its intracellular receptor (PR), which is a ligand-activated transcription factor that modifies the expression of genes involved in the control of cell growth and proliferation, such as vascular endothelial growth factor and epidermal growth factor receptor. Two PR isoforms have been reported: PR-B and PR-A, which present different function and regulation. PR isoforms are expressed in U373 and D54 cell lines, which are derived from grades III and IV of human astrocytomas, respectively. In both cells lines P increases the number of astrocytomas cells. The PR antagonist, RU486, blocked P effects and its treatment alone significantly reduced human astrocytomas cell growth in vitro. The over-expression of PR-A in U373 cells significantly reduced P effects. These data suggest that P regulates human astrocytomas cell proliferation through the interaction with PR.