Signal Pathway of Cell Migration Mediated by HBx Figure 1. 5-LOX is responsible for the upregulation of OPN mediated by HBx. (A) The promoter activities of OPN were detected by luciferase reporter gene assay in HepG2-X and HepG2 cells treated with MK886 or Indo, respectively (**P,0.01, ns, not significant, Student’s t test). (B) The promoter activity of OPN was detected by luciferase reporter gene assay in HepG2-X (or H7402-X) cells treated with the indicated doses of siRNA targeting 5-LOX mRNA (Si-5-LOX) (**P,0.01, Student’s t test). (C) The protein levels of OPN, 5-LOX and HBx were examined in the cells by western blot analysis. doi:10.1371/journal.pone.0031458.g001 manner in HepG2 (or H7402) cells (Figure 3D). Furthermore, Capn4 mRNA and protein levels were increased in the cells by the overexpression of OPN in a dose-dependent manner (Figure 3E and F). Our data suggest that OPN is able to stimulate the expression of Capn4. NF-kB is responsible for the OPN-mediated upregulation of Capn4 It is known that OPN induces NF-kB activation, resulting in the upregulation of its downstream effectors via attachment to b-3 integrin receptors and the induction of cell spreading and PLoS ONE | www.plosone.org 3 February 2012 | Volume 7 | Issue 2 | e31458