Effect of HA14-1 on apoptosis-regulating proteins in HeLa cells

Overexpression of Bcl-2 has been recognized in various malignancies. Recently, HA14-1, a Bcl-2 antagonist, has been identified for its anti-apoptotic effect. However, mode of action of HA14-1 still remains to be elucidated. In this study, we examined HA14-1 binding efficiency with receptor proteins through molecular docking. Cell viability using HeLa cells was evaluated through MTT assay after exposure to different concentration of HA14-1. Moreover, after HA14-1 exposure, expressions of tumor suppressor protein (p53), BH3-only protein (Puma) and apoptosis-associated proteins were analyzed by Western blotting. From the results, it was found that HA14-1 occupied all three domains; BH1, BH2, and BH3 within the hydrophobic pocket of Bcl-2. However, HA14-1 occupied only BH1 and BH3 of Bcl-xl, conversely, no such stable bond was observed for Bax and Bak. ARG107 and TYR101 were the amino acids involved in the binding of HA14-1 to Bcl-2 and Bcl-xl, respectively. Additionally, decrease in Bcl-2 and Bcl-xl expression along with increase in p53 and Puma expression after exposure to HA14-1 was observed. The results suggested p53 pathway to be the probable mechanism of action for the induction of apoptosis in HeLa cell by downregulating the effect of anti-apoptotic proteins suggesting that HA14-1 may provide therapeutic potential for the treatment of human cervical cancer.