The Molecular Mechanism Of Klotho Promoting The Apoptosis Resistance Of Hepatocellular Carcinoma Cells By VEGFR2 / PAK1 Signaling Pathway

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 of52hepatoma 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 kinase1(PAK1) expression and shRNA-mediated PAKl knockdown and kinase activity inhibition with kinase dead mutant PAK1K299R coexpression or allosteric inhibitor IPA3treatment reversed anoikis resistance in Klotho-overexpressed hepatoma cells. More importantly, the pivotal significance of upregulated VEGFR2protein levels mediated by Klotho expression was confirmed by VEGFR2inhibitor Axitinib and blocking antibody treatment in hepatoma cells. Axitinib treatment sensitized anoikis was reversed by constitutive active mutant PAK1T423E coexpression in Klotho-overexpressed hepatoma cells. Conversely, knockdown of Klotho reduced VEGFR2/PAK1 dependent anoikis resistance, which could be reversed by PAK1T423E. These results revealed a novel oncogenic function of Kotho in promoting anoikis resistance via activating VEGFR2/PAK1signaling, thus facilitating tumor migration and invasion during hepatoma progression, which could provide a putative molecular mechanism for tumor metastasis.