Reduced DENV-induced phosphorylated p38 MAPK, TNF-α and apoptosis in HepG2 cells by siRNA against CD137. HepG2 cells were transfected with either CD137 siRNA or control siRNA. Twenty-four hours post transfection, cells were infected with DENV at MOI 5 for 60 h. Cells were collected and analyzed for (A) CD137 mRNA (B) CD137 positive cells (C) phosphorylation of p38 and (D) Apoptosis by flow cytometry. The cells were collected and analyzed for TNF-α mRNA (E) and the culture supernatant was analyzed for TNF-α protein (F). All data were obtained from three independent experiments and reported as the mean ± SEM. Statistical differences between the groups were tested with an unpaired t-test using StatView version 5.0 and P value less than 0.05 was considered significant.