Klotho endows hepatoma cells with resistance to anoikis via VEGFR2/PAK1 activation in hepatocellular carcinoma

PLoS One. 2013;8(3):e58413. doi: 10.1371/journal.pone.0058413. Epub 2013 Mar 13.

Abstract

Klotho was originally characterized as an aging suppressor gene that predisposed Klotho-deficient mice to premature aging-like syndrome. Although Klotho was recently reported to exhibit tumor suppressive properties during various malignant transformations, the functional role and molecular mechanism of Klotho in hepatocarcinogenesis remains poorly understood. In our present study, immunohistochemical Klotho staining levels in a clinical follow-up of 52 hepatoma patients were significantly associated with liver cirrhosis, tumor multiplicity and venous invasion. The overall survival rate of hepatoma patients with high Klotho expression was significantly lower than those patients with low Klotho expression. Moreover, Klotho overexpression increased cellular migration, anchorage-independent growth, and anoikis resistance in hepatoma cells. Klotho overexpression elevated p21-activated kinase 1 (PAK1) expression and shRNA-mediated PAK1 knockdown and kinase activity inhibition with kinase dead mutant PAK1 K299R coexpression or allosteric inhibitor IPA3 treatment reversed anoikis resistance in Klotho-overexpressed hepatoma cells. More importantly, the pivotal significance of upregulated VEGFR2 protein levels mediated by Klotho expression was confirmed by VEGFR2 inhibitor Axitinib and blocking antibody treatment in hepatoma cells. Axitinib treatment sensitized anoikis was reversed by constitutive active mutant PAK1 T423E coexpression in Klotho-overexpressed hepatoma cells. Conversely, knockdown of Klotho reduced VEGFR2/PAK1 dependent anoikis resistance, which could be reversed by PAK1 T423E. These results revealed a novel oncogenic function of Klotho in promoting anoikis resistance via activating VEGFR2/PAK1 signaling, thus facilitating tumor migration and invasion during hepatoma progression, which could provide a putative molecular mechanism for tumor metastasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anoikis* / genetics
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / metabolism*
  • Carcinoma, Hepatocellular / mortality
  • Carcinoma, Hepatocellular / pathology
  • Cell Line, Tumor
  • Cell Proliferation
  • Enzyme Activation
  • Female
  • Glucuronidase / genetics
  • Glucuronidase / metabolism*
  • Humans
  • Liver Neoplasms / genetics
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / mortality
  • Liver Neoplasms / pathology
  • Male
  • Middle Aged
  • Neoplasm Grading
  • Neoplasm Staging
  • RNA Interference
  • Signal Transduction
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism*
  • p21-Activated Kinases / metabolism*

Substances

  • Vascular Endothelial Growth Factor Receptor-2
  • p21-Activated Kinases
  • Glucuronidase
  • klotho protein

Grant support

This work was supported by grants from National Basic Research Program of China 973 Program (2012CB822104, 2010CB912104) and State Key Project Specialized for Infectious Diseases of China (2012ZX10002-008, 2012ZX10002-012), National High-Tech R&D 863 Program (2012AA020203), and National Natural Science Fund (30930025, 31010103906, 31170766, 31100629, 31270863). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.