RÉSUMÉ
OBJECTIVE: To study the effect of Bt9875 crystal protein treated with proteinase K on human cancer cells, HL-60. METHODS: We used the methods of Thiazolyl Blue Tetrazolium Bromide, fluorescence microscopy examination, agarose gel electrophores and flow cytometry to detect the growth inhibition rate and apoptosis characters of the HL-60 cells that were treated with different concentration of Bt9875 crystal protein. RESULTS: Bt9875 crystal protein inhibited the growth of HL-60 cells evidently in a dose-dependent manner, with minimal effects on normal human peripheral blood mononuclear cells (PBMCs). The nuclei of HL-60 cells showed the characteristics of apoptosis. The analysis by flow cytometry indicated that the apoptosis rate of HL-60 cells was 52% after treatment with Bt9875 crystal protein (100 microg/mL). DNA analyzed by agarose gel electrophoresis showed "ladder" pattern. CONCLUSION: Bt9875 crystal protein could inhibit the growth of HL-60 and induced its apoptosis, which provided a foundation for use of Bt9875 crystal protein to cure the acute myeloid leukemia.