A SEQUENCE IN THE 5'-FLANKING REGION CONFERS PROGESTIN RESPONSIVENESSON THE HUMAN C-MYC GENE

Previous reports have shown that progestins stimulate the proliferatio n of the human breast cancer cell Line T47D in culture. Under differen t conditions other reports have shown progestin stimulation, inhibitio n or no effect on growth. It has also been shown that c-myc expression is stimulated at early times by progestins. We are currently testing the hypothesis that the mechanism of growth enhancement by progestins involves the stimulation of expression of c-myc. This hypothesis predi cts a progesterone regulatory region in or near the c-myc gene. We hav e identified a region, from -2327 to -1833, which serves this function . This region includes a 15 bp sequence with homology to the PRE (prog esterone response element) consensus sequence. Human progesterone rece ptor (PR) binds to this sequence in a specific, Ligand-enhanced manner in electrophoretic mobility shift assays (EMSA). A 3507 bp HindIII-Xb aI fragment of the 5' flanking region of the c-myc gene, -2327 to +118 0, containing the progestin regulatory region and the c-myc promoter, confers progestin responsiveness to the CAT (chloramphenicol acetyl tr ansferase) reporter gene in progesterone receptor (PR)-rich T47D human breast cancer cells, but not in PR-negative MDA-MB-231 cells. Removal of the progestin regulatory region abrogates progestin responsiveness . These data demonstrate that the sequence from -2327 to -1833 of the human c-myc gene includes a positive progestin regulatory region. (C) 1997 Elsevier Science Ltd.