Suppression of autophagy by CUB domain-containing protein 1 signaling is essential for anchorage-independent survival of lung cancer cells

Cancer Sci. 2013 Jul;104(7):865-70. doi: 10.1111/cas.12154. Epub 2013 Apr 19.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism*
  • Adenocarcinoma / pathology*
  • Adenocarcinoma of Lung
  • Anoikis / drug effects
  • Anoikis / genetics
  • Antigens, CD / genetics*
  • Antigens, CD / metabolism*
  • Antigens, Neoplasm
  • Autophagy / drug effects
  • Autophagy / genetics*
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Cell Adhesion Molecules / antagonists & inhibitors
  • Cell Adhesion Molecules / genetics*
  • Cell Adhesion Molecules / metabolism*
  • Cell Death / drug effects
  • Cell Death / genetics
  • Cell Line, Tumor
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism*
  • Lung Neoplasms / pathology*
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / genetics*
  • Neoplasm Proteins / metabolism*
  • Phagosomes / drug effects
  • Phagosomes / genetics
  • Phagosomes / metabolism
  • Phagosomes / pathology
  • Phosphorylation / drug effects
  • Phosphorylation / genetics
  • Protein Kinase C-delta / genetics
  • Protein Kinase C-delta / metabolism
  • Proto-Oncogene Proteins c-fyn / genetics
  • Proto-Oncogene Proteins c-fyn / metabolism
  • RNA, Small Interfering / administration & dosage
  • RNA, Small Interfering / genetics
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • src-Family Kinases / genetics
  • src-Family Kinases / metabolism

Substances

  • Antigens, CD
  • Antigens, Neoplasm
  • CDCP1 protein, human
  • Cell Adhesion Molecules
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Neoplasm Proteins
  • RNA, Small Interfering
  • 3-methyladenine
  • FYN protein, human
  • Proto-Oncogene Proteins c-fyn
  • src-Family Kinases
  • Protein Kinase C-delta
  • Caspase 3
  • Adenine