HUMAN ENDOMETRIAL FIBROBLASTS IMMORTALIZED BY SIMIAN-VIRUS-40 LARGE T-ANTIGEN DIFFERENTIATE IN RESPONSE TO A DECIDUALIZATION STIMULUS

Human endometrial fibroblasts have been immortalized by infection with simian virus 40 large T antigen and established as a permanent cell l ine, St-2. Biochemical differentiation of this cell line has been demo nstrated by the ability of a decidualizing stimulus, 8-bromo-cAMP plus medroxyprogesterone acetate (MPA), to induce PRL secretion and increa se the enzymatic activity of estrone sulfatase. MPA, alone or in combi nation with estradiol, was unable to elicit this response, but potenti ated the effect of 8-bromo-cAMP on PRL production and estrone sulfatas e activity. The increase in PRL protein was accompanied by an increase in PRL messenger RNA and increased expression of the insulin like gro wth factor-binding protein-1 messenger RNA. The St-2 cell PRL transcri pt was larger than the pituitary PRL transcript, suggesting its initia tion from the distal, nonpituitary, PRL promoter. This was confirmed b y reverse transcription-PCR analysis of PRL transcripts using primers specific for the additional sequences present only in the 5'-untransla ted region of RNA initiated from the distal promoter. Transient transf ection of a reporter construct containing 3000 bp of DNA 5' to the dec idual-specific promoter of the human PRL gene demonstrated that cAMP w as capable of activating this distal promoter in St-2 cells. In conclu sion, this novel cell line provides an interesting new model in which to pursue aspects of biochemical differentiation of human endometrium in vitro.