title: Distinct molecular pathways mediate progesterone-induced growth inhibition and focal adhesion.
abstract: We have reported previously that reactivation of progesterone receptor (PR) expression in estrogen receptor (ER)- and PR-negative MDA-MB-231 breast cancer cells enabled progesterone to inhibit cell growth and invasiveness, and to induce remarkable focal adhesions. The present study addressed molecular mechanisms that mediate these anticancer effects of progesterone in the PR-transfected breast cancer cells ABC28. In response to progesterone treatment are the marked up-regulation of cyclin-dependent kinase inhibitor protein p21WAF1/CIP1 and decreased expression of cyclin A, cyclin B1, and cyclin D1 that are required for G1 progression and during cell mitosis. Progesterone also induced down-regulation of phosphorylated MAPK (p42/44 MAPK). Furthermore, this study also demonstrated that MEK inhibitor PD98059 that inhibits the phosphorylation of p42/44 MAPK also caused reduction of cyclin D1 level and inhibition of cell proliferation. These results suggest that inhibition of p42/44 MAPK pathway is part of the mechanisms mediating progesterone's growth-inhibitory effect. On the other hand, progesterone-induced focal adhesion is mediated by separate pathway. Whereas PD98059 exhibited no effects on cell adhesion, inhibitory antibody to beta1-integrin was able to reverse progesterone-induced focal adhesion and progesterone-induced increase in the phosphorylation of focal adhesion kinase. On the other hand, beta1-integrin antibody had no effect on progesterone-mediated growth inhibition and on progesterone-mediated expression of cyclins p21CIP1/WAF1 and phosphorylation of P42/P44 MAPK. In the context of complex functions of progesterone in breast cancer and reproductive organs, identification of distinct pathways offers new strategies for designing therapeutic agents to target the specific pathway so as to minimize the side effects.
authors.affiliation: Department of Clinical Research, Singapore General Hospital, School of Biological Sciences, School, Singapore 637616. cllin@ntu.edu.sg.
authors.forename: Valerie C L
authors.initials: VC
authors.lastname: Lin
authors.forename: Chow Thai
authors.initials: CT
authors.lastname: Woon
authors.forename: Swee Eng
authors.initials: SE
authors.lastname: Aw
authors.forename: Chunhua
authors.initials: C
authors.lastname: Guo
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D001943:Breast Neoplasms; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D019938:Cyclin D1 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism; D048728:MAP Kinase Kinase Kinase 1; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism; D011980:Receptors, Progesterone / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000906:Antibodies; C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D019925:Cyclin A; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D019012:Integrin beta1; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D019938:Cyclin D1; D011374:Progesterone; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one