Lysophosphatidic Acid Promotes Hepatocellular Carcinoma Cell Invasion through EGFR, Cytokeratin 19 Expression and NF-κB Activation

Abstract

Background: Lysophosphatidic acid (LPA) is a lipid mediator that has diverse biological activities associated with cell proliferation, migration and survival. LPA has been implicated in the etiology of cancer due to its involvement in tumor growth, invasion and metastasis. The aim of this study was to investigate if LPA promotes invasion of hepatocellular carcinoma (HCC) cells and to elucidate which signaling pathway is modulated by LPA under hypoxic condition.

Methods and Results: We performed in vitro experiments using human HCC cell line (SNU761). Invasion of cells was assessed using invasion assay kit and the phenotypic changes after LPA treatment were examined using immunoblot analysis. The cells were treated with AG 1478 and guggulsterone, which are inhibitors of epidermal growth factor receptor (EGFR) and nuclear factor kappa B (NF-κB) activation, respectively. Treatment of LPA significantly augmented CK 19 expression leading to acceleration of invasion of HCC cells under hypoxic condition (1% O2, 5% CO2, 94% N2). Knockdown of CK 19 by siRNA transfection under hypoxia attenuated invasion of HCC cells stimulated by LPA. AG 1478 attenuated invasion of HCC cells and CK 19 expression augmented by LPA. AG 1478 and guggulsterone showed additive effect on attenuation of invasion of HCC cells stimulated by LPA.

Conclusions: Collectively, these results suggest that LPA promotes invasiveness of HCC cells by augmenting EGFR transactivation, CK 19 expression and NF-κB activation under hypoxic condition. Therefore, selective blockade of LPA receptor may have therapeutic potential in CK 19-positive HCCs, particularly in the tumors exposed to hypoxic environments.