Consistent with the findings that a synergistic effect of sorafenib and ATRA on cell death could be blocked by the caspase inhibitor zVAD, cleavage of caspase 9 and caspase 3 were robustly detected upon combinational treatment of sorafenib and ATRA, indicating that sorafenib and ATRA synergistically inhibit tumor growth by inducing apoptosis. Here, CASP9 is linked to neoplasm.