title: ATG9A loss confers resistance to trastuzumab via c-Cbl mediated Her2 degradation.
abstract: Acquired or de novo resistance to trastuzumab remains a barrier to patient survival and mechanisms underlying this still remain unclear. Using stable isotope labelling by amino acids in cell culture (SILAC)-based quantitative proteomics to compare proteome profiles between trastuzumab sensitive/resistant cells, we identified autophagy related protein 9A (ATG9A) as a down-regulated protein in trastuzumab resistant cells (BT474-TR). Interestingly, ATG9A ectopic expression markedly decreased the proliferative ability of BT474-TR cells but not that of the parental line (BT474). This was accompanied by a reduction of Her2 protein levels and AKT phosphorylation (S473), as well as a decrease in Her2 stability, which was also observed in JIMT1 and MDA-453, naturally trastuzumab-resistant cells. In addition, ATG9A indirectly promoted c-Cbl recruitment to Her2 on T1112, a known c-Cbl docking site, leading to increased K63 Her2 polyubiquitination. Whereas silencing c-Cbl abrogated ATG9A repressive effects on Her2 and downstream PI3K/AKT signaling, its depletion restored BT474-TR proliferative rate. Taken together, our findings show for this first time that ATG9A loss in trastuzumab resistant cells allowed Her2 to escape from lysosomal targeted degradation through K63 poly-ubiquitination via c-Cbl. This study identifies ATG9A as a potentially druggable target to overcome resistance to anti-Her2 blockade.
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Joao
authors.initials: J
authors.lastname: Nunes
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Nicos
authors.initials: N
authors.lastname: Angelopoulos
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Chhetri
authors.affiliation: Department of Microbiology and Immunology, Cardinal Bernardin Cancer Center of Loyola University Chicago, Health Sciences Division, Maywood, Illinois, USA.
authors.forename: Clodia
authors.initials: C
authors.lastname: Osipo
authors.affiliation: School of Life Sciences, University of Sussex, Brighton, UK.
authors.forename: Arnhild
authors.initials: A
authors.lastname: Grothey
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.
authors.forename: Justin
authors.initials: J
authors.lastname: Stebbing
authors.affiliation: Department of Surgery and Cancer, Division of Cancer, Imperial College London, Hammersmith Hospital Campus, London, UK.|School of Life Sciences, University of Sussex, Brighton, UK.
authors.forename: Georgios
authors.initials: G
authors.lastname: Giamas
mesh_terms: D000074322:Antineoplastic Agents, Immunological / Q000494:pharmacology; D000071183:Autophagy-Related Proteins / Q000172:deficiency / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008565:Membrane Proteins / Q000172:deficiency / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D000068878:Trastuzumab / Q000494:pharmacology*; D033921:Vesicular Transport Proteins / Q000172:deficiency / Q000378:metabolism*
chemical_list: D000074322:Antineoplastic Agents, Immunological; D000071183:Autophagy-Related Proteins; D008565:Membrane Proteins; D050721:Proto-Oncogene Proteins c-cbl; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; D033921:Vesicular Transport Proteins; C574794:ATG9A protein, human; C508053:ERBB2 protein, human; C067419:CBL protein, human
keywords: ATG9A; SILAC; breast cancer; resistance; trastuzumab