Progesterone Induces the Growth and Infiltration of Human Astrocytoma Cells Implanted in the Cerebral Cortex of the Rat

Progesterone (P(4)) promotes cell proliferation in several types of cancer, including brain tumors such as astrocytomas, the most common and aggressive primary intracerebral neoplasm in humans. In this work, we studied the effects of P(4) and its intracellular receptor antagonist, RU486, on growth and infiltration of U373 cells derived from a human astrocytoma grade III, implanted in the motor cortex of adult male rats, using two treatment schemes. In the first one, fifteen days after cells implantation, rats were daily subcutaneously treated with vehicle (propylene glycol, 160 μL), P(4) (1 mg), RU486 (5 mg), or P(4) + RU486 (1 mg and 5 mg, resp.) for 21 days. In the second one, treatments started 8 weeks after cells implantation and lasted for 14 days. In both schemes we found that P(4) significantly increased the tumor area as compared with the rest of the treatments, whereas RU486 blocked P(4) effects. All rats treated with P(4) showed tumor infiltration, while 28.6% and 42.9% of the animals treated with RU486 and P(4) + RU486, respectively, presented it. Our data suggest that P(4) promotes growth and migration of human astrocytoma cells implanted in the motor cortex of the rat through the interaction with its intracellular receptor.