Cytosolic phospholipase A2α modulates cell-matrix adhesion via the FAK/paxillin pathway in hepatocellular carcinoma

Objective: To explore the effect of cytosolic phospholipase A2α (cPLA2α) on hepatocellular carcinoma (HCC) cell adhesion andthe underlying mechanisms. Methods: Cell adhesion, detachment, and hanging-drop assays were utilized to examine the effect of cPLA2α on the cell-matrixand cell-cell adhesion. Downstream substrates and effectors of cPLA2α were screened via a phospho-antibody microarray.Associated signaling pathways were identified by the functional annotation tool DAVID. Candidate proteins were verified usingwestern blot and colocalization was investigated via immunofluorescence. Western blot and immunohistochemistry were used todetect protein expression in HCC tissues. Prognosis evaluation was conducted using Kaplan-Meier and Cox-proportional hazardsregression analyses. Results: Our findings showed that cPLA2α knockdown decreases cell-matrix adhesion but increases cell-cell adhesion in HepG2cells. Microarray analysis revealed that phosphorylation of multiple proteins at specific sites were regulated by cPLA2α. Thesephosphorylated proteins were involved in various biological processes. In addition, our results indicated that the focal adhesionpathway was highly enriched in the cPLA2α-relevant signaling pathway. Furthermore, cPLA2α was found to elevatephosphorylation levels of FAK and paxillin, two crucial components of focal adhesion. Moreover, localization of p-FAK to focaladhesions in the plasma membrane was significantly reduced with the downregulation of cPLA2α. Clinically, cPLA2α expressionwas positively correlated with p-FAK levels. Additionally, high expression of both cPLA2α and p-FAK predicted the worstprognoses for HCC patients. Conclusions: Our study indicated that cPLA2α may promote cell-matrix adhesion via the FAK/paxillin pathway, which partlyexplains the malignant cPLA2α phenotype seen in HCC.