Russells Viper Venom Purified Toxin Drct-II Inhibits the Cell Proliferation and Induces G1 Cell Cycle Arrest in Human Leukemic Cancer Cells

The present study was an effort to establish the anticancer activity of the purified protein toxin (drCT-II) from Indian Russell’s viper (Daboia russelli russelli) venom in leukemic cell line and animal model. Isolation and purification of drCT-II was done through CM-cellulose ion exchange chromatography and RP- HPLC. SDS- PAGE molecular weight and first 20 amino acid sequence of drCT-II was done. The anti-leukemic activity using U937 and K562 cell line was established through cytotoxicity, apoptosis, cell cycle study, morphology, cancer marker proteins. The mean survival time of EAC induced male albino mice was established. Human lymphocyte cytotoxicity was done. drCT-II was eluted with 0.1 M NaCl on CM-cellulose ion exchange chromatography. On RP-HPLC, drCT-II produced single peak with retention time of 14.6 min. SDS-PAGE molecular weight was found to be 6.6 KDa and the first 20 amino acid sequence was found to be LQXNKLVPIASKTXPPGKNL. drCT-II produced time and dose dependent cell (U937 and K562) growth inhibition. The IC50 was found to be 35.5 μg/ml for U937 cell and 48.2 μg/ml for K562 cells. drCT-II produced membrane disruption, blebbing and nuclear disintegration in U937 and K562 cells observed through confocal and scanning electron microscopy. It exhibited DNA fragmentation and comet formation in leukemic cells. drCT-II produced apoptosis, cell cycle arrest at G1 phase and increased the expression of P21, P27 and P53. drCT-II induced apoptosis in leukemic cells was followed through caspase 3 and 9 pathway activation. EAC cell growth in male albino mice was significantly inhibited by drCT-II, thus increased the mean survival time. drCT-II significantly reduced the human lymphocyte count (in culture). It may be concluded that drCT-II, a 6.6 KDa protein purified from Daboia russelli russelli venom would be a novel pro-apoptotic agent that induced cancer cell killing through p53 and caspase pathway.