title: Convergence of progesterone and epidermal growth factor signaling in breast cancer. Potentiation of mitogen-activated protein kinase pathways.
abstract: During late stages of breast cancer progression, tumors frequently acquire steroid hormone resistance with concurrent amplification of growth factor receptors; this alteration predicts a poor prognosis. We show here that following treatment with the progestin, R5020, breast cancer cells undergo a "biochemical shift" in the regulation of epidermal growth factor (EGF)-stimulated signaling pathways: R5020 potentiates the effects of EGF by up-regulating EGFR, c-ErbB2 and c-ErbB3 receptors, and by enhancing EGF-stimulated tyrosine phosphorylation of signaling molecules known to associate with activated type I receptors. Independently of EGF, R5020 increases Stat5 protein levels, association of Stat5 with phosphotyrosine-containing proteins, and tyrosine phosphorylation of JAK2 and Shc. Furthermore, progestins "prime" breast cancer cells for growth signals by potentiating EGF-stimulated p42/p44 mitogen-activated protein kinase (MAPK), p38 MAP kinase, and JNK activities. Although the levels of cyclin D1, cyclin E, and p21(WAF1), are up-regulated by R5020 alone, they are synergistically up-regulated by EGF in the presence of R5020. Up-regulation of cell cycle proteins by EGF is blocked by inhibition of p42/p44 MAPK only in the presence of R5020, supporting a shift in the regulation of these cell cycle mediators from MAPK-independent to MAPK-dependent pathways. In summary, progesterone selectively increases the sensitivity of key kinase cascades to growth factors, thereby priming cells for stimulation by latent growth signals. These data support a model in which breast cancer cell growth switches from steroid hormone to growth factor dependence.
authors.affiliation: Department of Medicine, Campus Box B151, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. Carol.Lange@UCHSC.edu
authors.forename: C A
authors.initials: CA
authors.lastname: Lange
authors.forename: J K
authors.initials: JK
authors.lastname: Richer
authors.forename: T
authors.initials: T
authors.lastname: Shen
authors.forename: K B
authors.initials: KB
authors.lastname: Horwitz
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005260:Female; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D008954:Models, Biological; D019000:Phosphotyrosine / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism*; D011397:Promegestone / Q000494:pharmacology; D020239:Receptor Cross-Talk; D017978:Receptors, Growth Factor / Q000096:biosynthesis; D015398:Signal Transduction; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D017978:Receptors, Growth Factor; D019000:Phosphotyrosine; D011374:Progesterone; D004815:Epidermal Growth Factor; D011397:Promegestone; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases