Wang et al.,12 demonstrated that doxorubicin when combined with quercetin causes a synergistic induction of apoptosis through the accumulation of p53, and the activation of the intrinsic apoptotic pathway via the activation of caspase 9 and 3 in human hepatoma cell lines (SMMC7721 and QGY7701).13 Thus it is interesting that the intrinsic pathway is still activated even within the p53 null cell lines investigated in the current study. Here, CASP9 is linked to hepatocellular carcinoma.