title: Suppression of autophagy by CUB domain-containing protein 1 signaling is essential for anchorage-independent survival of lung cancer cells.
abstract: CUB (C1r/C1s, urchin embryonic growth factor, BMP1) domain-containing protein 1 (CDCP1) has been implicated in promoting metastasis of cancer cells through several mechanisms, including the inhibition of anoikis, which is cell death triggered by the loss of extracellular matrix interactions. However, the mechanism inhibiting cell death regulated by CDCP1 remains elusive. Inhibition of CDCP1 expression using small interfering RNA (siRNA) induced the cell death of suspended cancer cells without cleaving caspase-3, a marker of apoptosis; cell death was not inhibited by a general caspase inhibitor, suggesting that the loss of CDCP1 induces caspase-independent cell death. In contrast, knockdown of CDCP1 as well as protein kinase Cδ (PKCδ), a downstream effector of CDCP1, in a suspension culture of lung cancer cells resulted in marked induction of membranous microtubule-associated protein 1 light chain 3 (LC3)-II protein, a hallmark of autophagy, and caused the formation of an autophagosome structure visualized using green fluorescent protein-tagged LC3-II. Expression and phosphorylation of exogenous CDCP1 by Fyn kinase reduced the formation of autophagosomes and inhibited phosphorylation of CDCP1 by PP2, a Src kinase inhibitor or inhibited PKCδ by rottlerin, stimulating autophagosome formation. Moreover, death of suspended lung cancer cells induced by CDCP1 siRNA or by PKCδ siRNA was reduced by the autophagy inhibitor 3-methyladenine. These results indicate that CDCP1-PKCδ signaling plays a critical role in inhibiting autophagy, which is responsible for anoikis resistance of lung cancer cells.
authors.affiliation: Division of Metastasis and Invasion Signaling, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: Takamasa
authors.initials: T
authors.lastname: Uekita
authors.forename: Satoko
authors.initials: S
authors.lastname: Fujii
authors.forename: Yuri
authors.initials: Y
authors.lastname: Miyazawa
authors.forename: Akinori
authors.initials: A
authors.lastname: Hashiguchi
authors.forename: Hitosi
authors.initials: H
authors.lastname: Abe
authors.forename: Michiie
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Sakai
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D000077192:Adenocarcinoma of Lung; D023102:Anoikis / Q000187:drug effects / Q000235:genetics; D015703:Antigens, CD / Q000235:genetics* / Q000378:metabolism*; D000951:Antigens, Neoplasm; D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D010588:Phagosomes / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; C432044:CDCP1 protein, human; D015815:Cell Adhesion Molecules; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; C025946:3-methyladenine; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases; D051745:Protein Kinase C-delta; D053148:Caspase 3; D000225:Adenine