title: The epidermal growth factor receptor antibody cetuximab induces autophagy in cancer cells by downregulating HIF-1alpha and Bcl-2 and activating the beclin 1/hVps34 complex.
abstract: Autophagy is a regulated catabolic process triggered in cells deprived of nutrients or growth factors that govern nutrient uptake. Here, we report that autophagy is induced by cetuximab, a therapeutic antibody that blocks epidermal growth factor receptor function. Cancer cell treatment with cetuximab triggered autophagosome formation, conversion of microtubule-associated protein 1 light chain 3 from its cytoplasmic to membrane-associated form, and increased acidic vesicular organelle formation. Autophagy occurred when cetuximab inhibited the class I phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin pathway, but not when it inhibited only the mitogen-activated protein/extracellular signal-regulated kinase kinase/Erk pathway, and it was accompanied by decreased levels of hypoxia inducible factor-1 alpha (HIF-1alpha) and Bcl-2. Stable overexpression of a HIF-1alpha mutant prevented cetuximab-induced autophagy and decrease in Bcl-2 levels. Knockdown of autophagy regulator beclin 1 or cell treatment with autophagy inhibitor 3-methyladenine, a class III PI3K (hVps34) inhibitor, also inhibited cetuximab-induced autophagy. Furthermore, knockdown of beclin 1 or Atg7 or treatment with the lysosome inhibitor chloroquine sensitized cancer cells to cetuximab-induced apoptosis. Mechanistic analysis argued that cetuximab acted by promoting an association between beclin 1 and hVps34, which was inhibited by overexpression of Bcl-2. Our findings suggest that the autophagy protects cancer cells from the proapoptotic effects of cetuximab.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Xinqun
authors.initials: X
authors.lastname: Li
authors.forename: Zhen
authors.initials: Z
authors.lastname: Fan
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000473:pathology; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology; D000068818:Cetuximab; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000473:pathology; D015536:Down-Regulation / Q000187:drug effects; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis* / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D058570:TOR Serine-Threonine Kinases; D033921:Vesicular Transport Proteins / Q000378:metabolism; D014846:Vulvar Neoplasms / Q000188:drug therapy / Q000473:pathology
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D000068818:Cetuximab; D066246:ErbB Receptors; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D058570:TOR Serine-Threonine Kinases; D033921:Vesicular Transport Proteins; C491997:BECN1 protein, human; C497442:HIF1A protein, human; C419573:VPS35 protein, human; C546842:MTOR protein, human