title: Enhanced c-jun activity alters responsiveness to medroxyprogesterone acetate in Ishikawa human endometrial carcinoma cells.
abstract: The involvement of altered c-jun activity in medroxyprogesterone acetate (MPA)-induced growth responses in human endometrial carcinoma cells is examined in this paper. Under conditions of MPA-induced growth inhibition, c-jun mRNA and protein levels are decreased in Ishikawa cells. This decrease is accompanied by an overall decrease in endogenous AP-1 activity in these cells. Only a transient decrease in c-jun mRNA level without any effect on endogenous AP-1 activity is seen in HEC-50 human endometrial carcinoma cells after MPA treatment. Increased expression and activity of c-jun was achieved in Ishikawa cells by transient transfection of Rous sarcoma virus (RSV)-c-jun alone or RSV-c-jun plus AP-1 binding sites (5x-4-beta-phorobol 12-myristate 13-acetate response element-thymidine kinase-chloramphenicol acetyltransferase), respectively. These treatments were accompanied by an increase in cell numbers due to MPA treatment in Ishikawa cells. In contrast, MPA treatment of mock-transfected, RSV-jun-B-transfected, or 5x-4 beta-phorbol 12-myristate 13-acetate response element-thymidine kinase-chloramphenicol acetyltransferase alone transfected Ishikawa cells resulted in the expected decrease in cell numbers. The data presented in this paper are consistent with the hypothesis that altered c-jun activity in a target cell can alter proliferative responsiveness to MPA and suggest that such a mechanism may be associated with resistance to hormonal manipulative therapies used in the treatment of both human breast and endometrial cancer.
authors.affiliation: Department of Biochemistry, University of Manitoba, Winnipeg, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Alkhalaf
authors.forename: L J
authors.initials: LJ
authors.lastname: Murphy
authors.forename: L C
authors.initials: LC
authors.lastname: Murphy
mesh_terms: D002277:Carcinoma / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D003864:Depression, Chemical; D016889:Endometrial Neoplasms / Q000473:pathology*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000502:physiology; D011980:Receptors, Progesterone / Q000187:drug effects / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D009363:Neoplasm Proteins; D016755:Proto-Oncogene Proteins c-jun; D011965:Receptors, Glucocorticoid; D011980:Receptors, Progesterone; D011993:Recombinant Fusion Proteins; D017258:Medroxyprogesterone Acetate