Ribonucleases (RNAses) isolated from different organisms could be considered as new antitumor drugs. Bacterial RNAses are perspective as antitumor agents because they are resistant to mammal cytosolic RNAse inhibitor. The possibility of apoptosis induction in K562 myelogenic erythroleukemia cells and normal human peripheral blood lymphocytes (PBMC) for Bacillus intemedius RNAse (binase) was studied. Apoptotic changes of cells were determined by flow cytometry with double-stainig by MC540 and 7-AAD. Binase showed a dose-dependent apoptosis-inducing effect and suppressed proliferation of K562 cells at 2–60mM. Enzyme did not exert proapoptotic effect on PBMCs. The induction of nonspecific immune response was investigated with flow cytometry by the expression level of CD69 antigen and IFN-[gamma] in human CD4+,CD8+ lymphocytes treated with binase. Neither CD69, nor IFN-[gamma] were expressed by cells in presence of binase at 2–60mM. The selective apoptogenic effect of binase to malignant cells and the absence of immunogenic properties support that bacterial RNAses are promising for designing alternative antitumor drugs.

This work was supported by grants RFBR 04-04-49385, ASRT 03-3.10-29, SC.02.434.11.3020.