Progesterone induces focal adhesion in breast cancer cells MDA-MB-231 transfected with progesterone receptor complementary DNA.
Since the effects of progesterone are mediated mainly via estrogen-dependent progesterone receptor (PR), the expression of the effects of progesterone may be masked or overridden by the influence of estrogen under conditions in which priming with estrogens is required. We have established a PR-positive but estrogen receptor-alpha (ER-alpha) negative breast cancer cell model by transfecting PR cDNA into ER-alpha- and PR-negative MDA-MB-231 cells in order that the functions of progesterone can be studied independently of estrogens. We have demonstrated using this model that progesterone markedly inhibited cell growth. We have also discovered that progesterone induced remarkable changes in cell morphology and specific adhesion structures. Progesterone-treated cells became considerably more flattened and well spread than vehicle-treated control cells. This was associated with a striking increase of stress fibers, both in number and diameter, and increased focal contacts as shown by the staining of focal adhesion proteins paxillin and talin. There were also distinct increases in tyrosine phosphorylation of focal adhesion protein paxillin and focal adhesion kinase in association with increased focal adhesion. The staining of tyrosine-phosphorylated proteins was concentrated at focal adhesions in progesterone-treated cells. More interestingly, monoclonal antibody (Ab) to beta1 integrin was able to inhibit progesterone-induced cell spreading and formation of actin cytoskeleton. To our knowledge, this is the first report describing a direct effect of progesterone in inducing spreading and adhesion of breast cancer cells, and beta1-integrin appeared to play an essential role in the effect. It is known that the initial step of tumor metastasis is the breakaway of tumor cells from primary tumor mass when they lose the ability to attach. Hence, progesterone-induced cell spreading and adhesion may have significant implications in tumor metastasis.
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Department of Clinical Research, Singapore General Hospital, Republic of Singapore. gcrlcl@sgh.gov.sg
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D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002277:Carcinoma / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D048429:Cell Size; D003598:Cytoskeletal Proteins / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D005260:Female; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000172:deficiency / Q000502:physiology; D011980:Receptors, Progesterone / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D019012:Integrin beta1; D009363:Neoplasm Proteins; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D011993:Recombinant Fusion Proteins; D011374:Progesterone; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human