A potential role of progestin-induced laminin-5/α6-integrin signaling in the formation of side branches in the mammary gland.
Mammary organoids from adult mice produce tubules, analogous to mammary ducts in vivo, in response to hepatocyte growth factor (HGF) when cultured in collagen gels. The combination of HGF plus progestin (R5020) causes reduced tubule number and length. We hypothesized that the inhibitory effect on tubulogenesis was due to progestin-mediated alteration of HGF/c-Met signaling. Using molecular inhibitors and short hairpin RNA, it was determined that HGF activation of Ras-related C3 botulinum toxin substrate (Rac1) was required for the formation of cytoplasmic extensions, the first step of tubulogenesis, and that Rac1 activity was Src kinase (Src) and focal adhesion kinase (FAK) dependent. The highly novel finding was that R5020 reduced tubulogenesis by up-regulating and increasing extracellular laminin and α6-integrin ligation to reduce activation of the Src, focal adhesion kinase, and Rac1 pathway. Receptor activator of nuclear factor-κB ligand, another progesterone-induced paracrine factor, did not replicate this effect of R5020. The inhibitory effect of R5020 on tubulogenesis was likely mediated through progesterone receptor (PR) isoform A (PRA), because PRA is the predominant PR isoform expressed in the organoids, and the progestin-induced effect was prevented by the PR antagonist RU486. These results provide a plausible mechanism that explains progestin/PRA-mediated blunting of HGF-induced tubulogenesis in vitro and is proposed to be relevant to progesterone/PRA-induced side-branching in vivo during pregnancy.
Department of Physiology and Breast Cancer and the Environment Research Center, Michigan State University, East Lansing, Michigan 48824, USA.
Gabriele
G
Meyer
Jeffrey
J
Leipprandt
Jianwei
J
Xie
Mark D
MD
Aupperlee
Sandra Z
SZ
Haslam
D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002465:Cell Movement / Q000502:physiology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000494:pharmacology; D006727:Hormone Antagonists / Q000494:pharmacology; D039503:Integrin alpha6 / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D000097794:Kalinin
D015815:Cell Adhesion Molecules; D051416:Focal Adhesion Protein-Tyrosine Kinases; D017228:Hepatocyte Growth Factor; D006727:Hormone Antagonists; D039503:Integrin alpha6; D015735:Mifepristone; D016392:Proto-Oncogene Proteins pp60(c-src); D011980:Receptors, Progesterone; D020830:rac1 GTP-Binding Protein; D000097794:Kalinin; C101118:progesterone receptor A