Rabiya Majeed, Abid Hamid, PR Sharma, Payare L. Sangwan, Surrinder Koul and Ajit K. Saxena
Accepted Abstracts: J Cancer Sci Ther
In light of the scientific promise of chemoprevention, there is an overwhelming need to develop new chemopreventive agents that are both effective and safe. Natural compounds of diverse structures have been considered prototypes, leads or heads of series. Approximately half of the drugs currently used in the clinic are derived from natural products and in the case of cancer this proportion surpasses 60%. The modulation of signalling pathways that are deregulated in cancer offers a promising strategy for the discovery of novel anti-cancer therapeutics. In the present study, we examined the effect of a novel cyano derivative of betulinic acid (CBA), to induce apoptosis in a panel of human cancer cell lines representing diverse cancers. Using CBA we observed the appreciable IC50 values ranging from 1 μM to 7.1 μM in various cancer cells used in the present study. However, HL-60 cells representing leukemia was found to be most sensitive with IC 50 value of 1 μM 12 μM and 24 μM after 48 hr, 24 hr and 12 hr treatments respectively. The mechanism of cell death involved the increased sub-G0 DNA fraction, enhanced annexin V/FITC binding of the cells, DNA fragmentation, chromatin-condensation, formation of apoptotic bodies and morphological changes in the HL-60 cells. It was also observed that the CBA induced substantial reactive oxygen species (ROS) generation which also forms important aspect of chemotherapeutic efficiency in cancer. A persistent high level of ROS was associated with decline of the mitochondrial membrane potential with simultaneous activation of caspase 8 and 9. Western blot analysis showed the poly ADP-ribose polymerase (PARP) cleavage also occurs on HBA treatment which therefore suggests its involvement in the functioning of DNA repair machinery. Furthermore, CBA inhibited DNA binding of NF-kB and caused nuclear cleavage of p65/Rel which demonstrates that NF-kB mediated gene expression is down regulated under such conditions. These findings indicated that CBA can be potential candidate that may be found useful in the management of human leukemia.