Signal Pathway of Cell Migration Mediated by HBx Figure 4. NF-kB is responsible for the OPN-mediated upregulation of Capn4. (A, B and C) OPN-overexpressed HepG2 (or H7402) cells were treated with the indicated doses of siRNA targeting NF-kB mRNA (Si-NF-kB) for 48 h. (A) The promoter activity of Capn4 was examined by reporter gene assay (**P,0.01 Student’s t test). (B) The mRNA levels of Capn4, OPN and NF-kB/p65 were detected by RT-PCR. (C) The protein levels of Capn4, OPN and NF-kB/p65 were measured by western blot analysis. doi:10.1371/journal.pone.0031458.g004 abolishment of enhanced promoter activity of OPN mediated by Capn4 in a dose-dependent manner (Figure 6A). Additionally, the upregulation of Capn4 mediated by OPN could be attenuated by Si-NF-kB at the levels of mRNA and protein in a dose-dependent manner (Figure 6B and C). Thus, we conclude that NF-kB is responsible for the Capn4-mediated upregulation of OPN. PLoS ONE | www.plosone.org 6 February 2012 | Volume 7 | Issue 2 | e31458