Knockdown of BDNF suppressed invasion of HepG2 and HCCLM3 cells, a mechanism associated with inactivation of RhoA or Rac1 and actin skeleton disorganization

Abstract

Brain-derived neurotrophic factor (BDNF) and its primary receptor tropomysin-related kinase B (TrkB) mediate critical signalings for supporting survival and growth of neurons. Even though we have previously confirmed that more expressions of BDNF and TrkB were closely correlated with multiple and advanced hepatocellular carcinoma (HCC), the exact mechanisms underlying have not been investigated. The expressions of BDNF and TrkB were examined by western blot and BDNF secretion was evaluated by ELISA in human HCC cell lines of HepG2 and HCCLM3 with high metastatic potential. BDNF knockdown was performed by specific BDNF-siRNA transfection in HCC cells, actin cytoskeleton was shown by FITC-phalloidin staining and the activations of RhoA, Rac1 or Cdc42 were determined using western blot. Cell apoptosis and invasion were examined by flow cytometry and transwell assay, respectively. More expressions of BDNF and TrkB were found in HCCLM3 than in HepG2 cells. Inhibited expression of BDNF by specific siRNA showed impaired actin polymerization and decreased activations of RhoA or Rac1 in both HepG2 and HCCLM3 cells. BDNF knockdown also induced apoptosis and suppressed invasion of both HepG2 and HCCLM3 cells. Our results suggested a role of BDNF/TrkB in confering HCCLM3 cells advantage of metastasis, and BDNF knockdown inhibited cell invasion probably through the blocked actin polymerization and the correlated inactivation of RhoA or Rac1. Aiming at BDNF/TrkB signaling interruption may be an effective strategy to prevent HCC progression.