Effects of tocotrienols on cytochrome c release of A549 and U87MG cells. Cytochrome c levels of A549 and U87MG cells treated with (A) alpha-, (B) gamma- and (C) delta-tocotrienols at IC50 and ICmax concentrations for 4 h with or without pretreatment of 50 μM of caspase-8 inhibitor, z-IETD-fmk are detected by ELISA. Significantly higher level of cytochrome c is released from all alpha-, gamma- and delta-tocotrienols-treated A549 and U87MG cells (p < 0.05) than that of untreated counterparts. The caspase-8 inhibitor, z-IETD-fmk has a direct effect in suppressing the cytochrome c release from treated cells. *Significance levels (*p < 0.05; **p < 0.01; ***p < 0.001) are set to compare between samples. α-T3: alpha-tocotrienol; γ-T3: gamma-tocotrienol; δ-T3: delta-tocotrienol.