title: An siRNA screen identifies the GNAS locus as a driver in 20q amplified breast cancer.
abstract: Poor-prognosis oestrogen receptor-positive breast cancer is characterised by the presence of high-level focal amplifications. We utilised a focused small interfering RNA screen in 14 breast cancer cell lines to define genes that were pathogenic in three genomic regions focally amplified in oestrogen receptor-positive breast cancer, 8p11-12, 11q13 and 20q. Silencing the GNAS locus, that encodes the G protein alpha stimulatory subunit Gαs, specifically reduced the growth of 20q amplified breast cancer cell lines. Examination of a publically available small hairpin RNA data set confirmed GNAS silencing to be selective for 20q amplified cancer cell lines. Cell lines with 20q amplification were found to overexpress specifically the extra long Gαs splice variant (XLαs). Overexpression of XLαs induced cAMP levels to a greater extent than Gαs, suggesting that amplification of the GNAS locus, and overexpression of the XLαs variant in particular, enhanced cAMP signalling. GNAS silencing in amplified cell lines reduced extracellular-signal-regulated kinase 1/2 (ERK1/2) phosphorylation, and conversely overexpression of exogenous XLαs in a non-amplified cell line increased MEK-ERK1/2 phosphorylation, identifying one potential downstream consequence of enhanced cAMP signalling. Our data indicate that amplification of the GNAS locus may contribute to the pathogenesis of breast cancer, and highlight a previously unrecognised role for the GNAS XLαs variant in cancer.
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: I
authors.initials: I
authors.lastname: Garcia-Murillas
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: R
authors.initials: R
authors.lastname: Sharpe
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Pearson
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Campbell
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: R
authors.initials: R
authors.lastname: Natrajan
authors.affiliation: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ashworth
authors.affiliation: 1] The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, UK [2] Breast Unit, Royal Marsden Hospital, London, UK.
authors.forename: N C
authors.initials: NC
authors.lastname: Turner
mesh_terms: D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D002864:Chromogranins; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D005784:Gene Amplification; D056426:Genetic Loci; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002864:Chromogranins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs