title: A novel CYR61-triggered 'CYR61-alphavbeta3 integrin loop' regulates breast cancer cell survival and chemosensitivity through activation of ERK1/ERK2 MAPK signaling pathway.
abstract: The angiogenic inducer CYR61 is differentially overexpressed in breast cancer cells exhibiting high levels of Heregulin (HRG), a growth factor closely associated with a metastatic breast cancer phenotype. Here, we examined whether CYR61, independently of HRG, actively regulates breast cancer cell survival and chemosensitivity, and the pathways involved. Forced expression of CYR61 in HRG-negative MCF-7 cells notably upregulated the expression of its own integrin receptor alphavbeta3 (>200 times). Small peptidomimetic alphavbeta3 integrin antagonists dramatically decreased cell viability of CYR61-overexpressing MCF-7 cells, whereas control MCF-7/V remained insensitive. Mechanistically, functional blockade of alphavbeta3 specifically abolished CYR6-induced hyperactivation of ERK1/ERK2 MAPK, whereas the activation status of AKT did not decrease. Moreover, CYR61 overexpression rendered MCF-7 cells significantly resistant (>10-fold) to Taxol-induced cytotoxicity. Remarkably, alphavbeta3 inhibition converted the CYR61-induced Taxol-resistant phenotype into a hypersensitive one. Thus, the augmentation of Taxol-induced apoptotic cell death in the presence of alphavbeta3 antagonists demonstrated a strong synergism as verified by the terminal transferase-mediated dUTP nick-end labeling (TUNEL) assay and by flow cytometric analysis for DNA content. Indeed, functional blockade of alphavbeta3, similarly to the pharmacological MAPK inhibitor U0126, synergistically increased both the proportion of CYR61-overexpressing breast cancer cells in the G2 phase of the cell cycle and the appearance of sub-G1 hypodiploid (apoptotic) cells caused by Taxol. Strikingly, CYR61 overexpression impaired the accumulation of wild-type p53 following Taxol exposure, while inhibition of alphavbeta3 or ERK1/ERK2 MAPK signalings completely restored Taxol-induced upregulation of p53. Moreover, antisense downregulation of CYR61 expression abolished the anchorage-independent growth of breast cancer cells engineered to overexpress HRG, and significantly increased their sensitivity to Taxol. Our data provide evidence that CYR61 is sufficient to promote breast cancer cell proliferation, cell survival, and Taxol resistance through a alphavbeta3-activated ERK1/ERK2 MAPK signaling. The identification of a 'CYR61-alphavbeta3 autocrine loop' in the epithelial compartment of breast carcinoma strongly suggests that targeting alphavbeta3 may simultaneously prevent breast cancer angiogenesis, growth, and chemoresistance.
authors.affiliation: Department of Medicine, Breast Cancer Translational Research Laboratory, Evanston Northwestern Healthcare Research Institute, Evanston, IL 60201, USA.
authors.forename: Javier A
authors.initials: JA
authors.lastname: Menendez
authors.forename: Luciano
authors.initials: L
authors.lastname: Vellon
authors.forename: Inderjit
authors.initials: I
authors.lastname: Mehmi
authors.forename: Poh K
authors.initials: PK
authors.lastname: Teng
authors.forename: David W
authors.initials: DW
authors.lastname: Griggs
authors.forename: Ruth
authors.initials: R
authors.lastname: Lupu
mesh_terms: D043925:Angiogenesis Inducing Agents; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D055515:Cysteine-Rich Protein 61; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology*; D016023:Integrins / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D019030:Receptors, Vitronectin / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: D043925:Angiogenesis Inducing Agents; C501848:CCN1 protein, human; D055515:Cysteine-Rich Protein 61; D017874:Immediate-Early Proteins; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D019030:Receptors, Vitronectin; D016159:Tumor Suppressor Protein p53; C094340:integrin alphavbeta1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D017239:Paclitaxel