Mitochondrial membrane permeability (MMP) alterations in A549 and U87MG cells treated with tocotrienols and vinblastine. Representative images showing the effects of (B) alpha-, (C) gamma- (D) delta-tocotrienols at 3 h treatment period on MMP of untreated (A) and treated A549 and U87MG cells in the presence or absence of caspase-8 inhibitor z-IETD-fmk. Untreated cancer cells possess intact mitochondrial membranes exhibiting intense red fluorescence, whereas treated cells show deep green fluorescence owing to loss of mitochondrial permeability. Cells pre-treated with z-IETD-fmk are not affected by either tocotrienol treatment, which still exhibit intense red fluorescence. (E) Representative images showing the effects of vinblastine at 3 h and 24 h treatment periods on MMP of treated A549 and U87MG cells. Vinblastine induces MMP very minimally where majority of treated A549 and U87MG cells show strong red fluorescence without being affected by the increased treatment period and concentration used. Bar: 20 μm. α-T3: alpha-tocotrienol; γ-T3: gamma-tocotrienol; δ-T3: delta-tocotrienol.