a-Tomatine, a tomato glycoalkaloid, has been reported to possess antibiotic properties against human pathogens. However,the mechanism of its action against leukemia remains unclear. In this study, the therapeutic potential of a-tomatine againstleukemic cells was evaluated in vitro and in vivo. Cell viability experiments showed that a-tomatine had significant cytotoxic effects on the human leukemia cancer cell lines HL60 and K562, and the cells were found to be in the Annexin V-positive/ propidium iodidenegative phase of cell death. In addition, a-tomatine induced both HL60 and K562 cell apoptosis in a cell cycle- and caspase-independent manner. a-Tomatine exposure led to a loss of the mitochrondrial membrane potential, and this finding was consistent with that observed on activation of the Bak and Mcl-1 short form (Mcl-1s) proteins. Exposure to a-tomatine also triggered the release of the apoptosis-inducing factor (AIF) from the mitochondria into the nucleus and down-regulated survivin expression. Furthermore, a-tomatine significantly inhibited HL60 xenograft tumor growth without causing loss of body weight in severe combined immunodeficiency (SCID) mice. Immunohistochemical test showed that the reduced tumor growth in the a-tomatine-treated mice was a result of increased apoptosis, which was associated with increased translocation of AIF in the nucleus and decreased survivin expression ex vivo. These results suggest that a-tomatine may be a candidate for leukemia treatment.
