Mitochondrially Targeted p53-Bad* Fusion Gene Therapy Promotes Apoptosis in Hepatocellular Carcinoma by Pan-Bcl-2 Inhibition

Presenting a considerable disease burden and global health threat, hepatocellular carcinoma (HCC) is in desperate need of potent and effective therapies. p53-Bad* is designed to provide mitochondrial targeting, enhance binding interactions with antiapoptotic Bcl-2 family members, and improve apoptotic activity in various cancers. While we have shown that fusion of p53 and Bad* improves mitochondrial localization and increases apoptosis in HCC, critically, the mechanism of action and nature of this heightened apoptotic function have not been delineated. Here, the functional activity and apoptotic mechanism of action of our p53-Bad* construct was explored, demonstrating that fusion of pro-apoptotic Bad* to p53 does indeed enhance interactions with antiapoptotic Bcl-2 family members Mcl-1, Bcl-2, and Bcl-xL relative to p53-WT. We confirm that p53-Bad* acts as a pro-apoptotic agent specifically at the mitochondria by inhibition and blockade of downstream Bak/Bax oligomerization events, rescuing cells from p53-Bad*-induced cytotoxicity and apoptosis. Using mutant p53-Bad* variants designed to disrupt binding interactions with antiapoptotic targets, a direct relationship between functional binding interactions and the apoptotic activity of p53-Bad* is established. These findings present strong evidence for the use of p53-Bad* as a pan-Bcl-2 inhibitor and synergistic pro-apoptotic agent in cancers with upregulation of multiple antiapoptotic and prognostic markers.