title: Decreased autocrine EGFR signaling in metastatic breast cancer cells inhibits tumor growth in bone and mammary fat pad.
abstract: Breast cancer metastasis to bone triggers a vicious cycle of tumor growth linked to osteolysis. Breast cancer cells and osteoblasts express the epidermal growth factor receptor (EGFR) and produce ErbB family ligands, suggesting participation of these growth factors in autocrine and paracrine signaling within the bone microenvironment. EGFR ligand expression was profiled in the bone metastatic MDA-MB-231 cells (MDA-231), and agonist-induced signaling was examined in both breast cancer and osteoblast-like cells. Both paracrine and autocrine EGFR signaling were inhibited with a neutralizing amphiregulin antibody, PAR34, whereas shRNA to the EGFR was used to specifically block autocrine signaling in MDA-231 cells. The impact of these was evaluated with proliferation, migration and gene expression assays. Breast cancer metastasis to bone was modeled in female athymic nude mice with intratibial inoculation of MDA-231 cells, and cancer cell-bone marrow co-cultures. EGFR knockdown, but not PAR34 treatment, decreased osteoclasts formed in vitro (p<0.01), reduced osteolytic lesion tumor volume (p<0.01), increased survivorship in vivo (p<0.001), and resulted in decreased MDA-231 growth in the fat pad (p<0.01). Fat pad shEGFR-MDA-231 tumors produced in nude mice had increased necrotic areas and decreased CD31-positive vasculature. shEGFR-MDA-231 cells also produced decreased levels of the proangiogenic molecules macrophage colony stimulating factor-1 (MCSF-1) and matrix metalloproteinase 9 (MMP9), both of which were decreased by EGFR inhibitors in a panel of EGFR-positive breast cancer cells. Thus, inhibiting autocrine EGFR signaling in breast cancer cells may provide a means for reducing paracrine factor production that facilitates microenvironment support in the bone and mammary gland.
authors.affiliation: Medical Sciences Program, Indiana University School of Medicine, Bloomington, Indiana, United States of America.
authors.forename: Nicole K
authors.initials: NK
authors.lastname: Nickerson
authors.forename: Khalid S
authors.initials: KS
authors.lastname: Mohammad
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Gilmore
authors.forename: Erin
authors.initials: E
authors.lastname: Crismore
authors.forename: Angela
authors.initials: A
authors.lastname: Bruzzaniti
authors.forename: Theresa A
authors.initials: TA
authors.lastname: Guise
authors.forename: John
authors.initials: J
authors.lastname: Foley
mesh_terms: D066258:Amphiregulin; D000818:Animals; D001842:Bone and Bones / Q000473:pathology*; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D066255:EGF Family of Proteins; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D010012:Osteogenesis / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation / Q000235:genetics / Q000502:physiology; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D055114:X-Ray Microtomography
chemical_list: C587848:AREG protein, human; D066258:Amphiregulin; C587849:Areg protein, mouse; D066255:EGF Family of Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D066246:ErbB Receptors