ATG9A loss confers resistance to trastuzumab via c-Cbl mediated Her2 degradation Journal Article

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Authors: Nunes, J.; Zhang, H; Angelopoulos, N.; Chhetri, J.; Osipo, C; Grothey, A.; Stebbing, J.; Giamas, G.
Article 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.
Journal Title: Oncotarget
ISSN: 1949-2553; 1949-2553
Publisher: Unknown  
Date Published: 2016
Language: ENG
DOI/URL:

10.18632/oncotarget.8504
Notes: LR: 20160407; JID: 101532965; OTO: NOTNLM; 2016/01/04 [received]; 2016/03/18 [accepted]; aheadofprint