title: Altered purinergic receptor-Ca²⁺ signaling associated with hypoxia-induced epithelial-mesenchymal transition in breast cancer cells.
abstract: Hypoxia is a feature of the microenvironment of many cancers and can trigger epithelial-mesenchymal transition (EMT), a process by which cells acquire a more invasive phenotype with enriched survival. A remodeling of adenosine 5'-triphosphate (ATP)-induced Ca(2+) signaling via purinergic receptors is associated with epidermal growth factor (EGF)-induced EMT in MDA-MB-468 breast cancer cells. Here, we assessed ATP-mediated Ca(2+) signaling in a model of hypoxia-induced EMT in MDA-MB-468 cells. Like EGF, hypoxia treatment (1% O2) was also associated with a significant reduction in the sensitivity of MDA-MB-468 cells to ATP (EC50 of 0.5 μM for normoxic cells versus EC50 of 5.8 μM for hypoxic cells). Assessment of mRNA levels of a panel of P2X and P2Y purinergic receptors following hypoxia revealed a change in levels of a suite of purinergic receptors. P2X4, P2X5, P2X7, P2Y1 and P2Y11 mRNAs decreased with hypoxia, whereas P2Y6 mRNA increased. Up-regulation of P2Y6 was a common feature of both growth factor- and hypoxia-induced models of EMT. P2Y6 levels were also significantly increased in basal-like breast tumors compared to other subtypes and breast cancer patients with higher P2Y6 levels showed reduced overall survival rates. P2Y6 siRNA-mediated silencing and the P2Y6 pharmacological inhibitor MRS2578 reduced hypoxia-induced vimentin protein expression in MDA-MB-468 cells. P2Y6 inhibition also reduced the migration of mesenchymal-like MDA-MB-231 breast cancer cells. The up-regulation of P2Y6 appears to be a common feature of the mesenchymal phenotype of breast cancer cells and inhibition of this receptor may represent a novel therapeutic target in breast cancer metastasis.
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia; Mater Research Institute, The University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia.
authors.forename: Iman
authors.initials: I
authors.lastname: Azimi
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Hannah
authors.initials: H
authors.lastname: Beilby
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Felicity M
authors.initials: FM
authors.lastname: Davis
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Daneth L
authors.initials: DL
authors.lastname: Marcial
authors.affiliation: Kabara Cancer Research Institute, Gundersen Medical Foundation, La Crosse, WI, USA.
authors.forename: Paraic A
authors.initials: PA
authors.lastname: Kenny
authors.affiliation: Institute of Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Kelvin Grove, Queensland, Australia; University of Melbourne Department of Surgery, St Vincent's Hospital, Fitzroy, Victoria, Australia; St Vincent's Institute, Fitzroy, Victoria, Australia.
authors.forename: Erik W
authors.initials: EW
authors.lastname: Thompson
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Roberts-Thomson
authors.affiliation: School of Pharmacy, The University of Queensland, Brisbane, Queensland, Australia; Mater Research Institute, The University of Queensland, Translational Research Institute, Brisbane, Queensland, Australia. Electronic address: gregm@uq.edu.au.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Monteith
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D020013:Calcium Signaling; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D020868:Gene Silencing; D006801:Humans; D011983:Receptors, Purinergic / Q000235:genetics / Q000378:metabolism*; D016019:Survival Analysis
chemical_list: D011983:Receptors, Purinergic
keywords: Breast cancer; Calcium; Epithelial-mesenchymal transition; Hypoxia; Purinergic receptors