Mitochondrially targeted polypeptides have killing ability against cancer cells

4385 Objective of the study : The tumor suppressor function of p53 is performed mainly by induction of apoptosis as a transcription factor, and also p53 has a direct apoptotic role at mitochondria. At mitochondria, p53 promotes oligomelization of the BH1,2,3 pro-apoptotic protein, leading outer mitochondrial membrane permeabilization and induces apoptosis as a result. One important mechanism by which p53 induces mitochondrial membrane permeabilization is that p53 forms a comprex with anti-apoptotic BclXL protein. Previously we reported that mitochondrially targeted p53 protein fused with protein transduction domain embedded in the human immunodeficiency virus TAT protein (TAT-PTD) had ability to induce apoptosis and tumor suppressor activity in the mouse-inoculated model of human colon cancer cell line. Here we generated polypeptides including BclXL binding domain, which consist of three parts of the DNA binding domain of p53, to investigate the apoptotic activity of each polypeptide and combination of these polypeptides.
 Methods : The mitochondrially targeted polypeptides derived from p53 fused with TAT-PTD protein were administered to human colon cancer cell line, LoVo. Apoptotic ability was evaluated at the time of 30 minutes, 1 hour and 2 hours after administration by TUNEL assay.
 Resul t: Administration of single or combinated polypeptides including BclXL binding domains demonstrated killing ability against cells, while the polypeptide consisting of N-terminus or proline rich domain of p53 showed no apoptotic activity.
 Conclusion : The mitochondrially targeted polypeptides including BclXL binding domain of p53 can induce apoptosis and they could be applied for new treatment of cancer.