Hypoxia downregulates continuous and interleukin-1-induced expression of human chorionic gonadotropin in choriocarcinoma cells.

The effects of hypoxia on JEG-3, BeWo, and JAr cells were investigated and it was demonstrated that choriocarcinoma cells can be used as a model to study the molecular mechanism of hypoxia-mediated repression of human chorionic gonadotropin (hCG). Cells were maintained under hypoxia (3.5 per cent O2) for 72 h without loss of variability, as demonstrated by the fact that 93-98 per cent of the cells excluded trypan blue. Up to 48 h, cell growth was not significantly influenced by hypoxia, and analysis by flow cytometry did not reveal major changes in cell cycle distribution. JEG-3, BeWo, and JAr cells which were grown for 48 h under hypoxia secreted 81, 67, and 71 per cent less hCG than cells cultivated under normoxic conditions. The extent of hCG reduction was dependent on the oxygen concentration. Moreover, release of the hormone from hypoxic JAr cells was not stimulated upon addition of interleukin-1 (IL-1). Treatment of JEG-3 cells with methotrexate (MTX) led to a 4.3-fold augmentation in hCG secretion and to an increase in the amount of G0/G1 cells. However, when cells were cultured in the presence of MTX and hypoxia, hCG secretion decreased 10-fold and beta hCG mRNA declined to almost undetectable levels suggesting that downregulation of beta hCG mRNA is the major cause of diminished hCG release under hypoxic conditions.