Effect of hypoxia on uPAR protein and mRNA levels in HTR-8/SVneo cells. (A) Analysis of uPAR expression by HTR-8/SVneo cells using flow cytometry showed an average increase of 68% in the mean fluorescence intensity when cells were cultured under hypoxic conditions and labeled with MoAb 3937. This figure is representative of seven independent experiments. (B) Northern blot analysis showed a 2.5-fold increase in uPAR mRNA levels after only 4 hours of hypoxic culture when compared with uPAR mRNA levels in cells cultured under standard conditions. The levels of uPAR transcript increased by fivefold at 6 hours of culture under hypoxia and remained high at 8 and 24 hours. Relative levels of uPAR mRNA were determined with a SigmaGel gel analysis program using 28S rRNA to correct for differences in the amount of RNA loaded onto the gel.