HYPOXIA DOWN-REGULATES 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 m odel to study the molecular mechanism of hypoxia-mediated repression o f human chorionic gonadotropin (hCG). Cells were maintained under hypo xia (3.5 per cent O-2) for 72 h without loss of viability, as demonstr ated 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 c ycle 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 cu ltivated under normoxic conditions. The extent of hCG reduction was de pendent on the oxygen concentration. Moreover, release of the hormone from hypoxic JAr cells was not stimulated upon addition of interleukin -1 (IL-l). 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 G(0)/G(1) cells. Hoc-ever, when cells were cultured in the presenc e of MTX and hypoxia, hCG secretion decreased 10-fold and beta hCG mRN A declined to almost undetectable levels suggesting that downregulatio n of beta hCG mRNA is the major cause of diminished hCG release under hypoxic conditions. (C) 1997 W.B. Saunders Company Ltd.