Co-treatment of PAM with TRAIL induces apoptosis via DR5 upregulation. (a) Combined treatment of PAM with TRAIL upregulates DR5 protein levels and downregulates c-FLIP protein levels in HeLa cells. Cells were treated with 0.2× PAM, TRAIL (20 ng/mL), or PAM/TRAIL (0.2× PAM with 20 ng/mL TRAIL). Cell extracts were prepared for immunoblotting of DR5, DR4, c-FLIP, Bcl-2, and β-actin. For immunoblotting, β-actin used as loading control. (b) DR5 mRNA levels were determined by qRT-PCR. GAPDH used as an internal control. (c) Silencing of DR5 gene was abrogated synergistic effects of TRAIL to PAM-mediated cell survival inhibition. shCTL or shDR5-transfected HeLa cells were treated 0 or 20 ng/mL TRAIL with serial diluted PAM for 24 h. Cellular growth inhibition was determined via the MTT assay. * p < 0.05, ** p < 0.01, *** p < 0.001.