Abstract A144: Restoration of tumor suppressor function by mitochondrially targeting p14 peptide in tumor cells

Abstract

Abstract Introduction Loss of CDKN2A (encoding p16INK4a and p14ARF) gene mainly by epigenetic alternations is associated with an increased susceptibility for development of malignant tumors. We previously reported the loss of the p14ARF function especially on the gefitinib-resistant lung adenocarcinomas (NSCLCs). In the present study, we identified the p14MIS (p14 minimal inhibitory sequence) peptide covering the functional core sequence of p14ARF, which is targeted to the mitochondria in the tumor cells and report its utility in growth suppression of biologically aggressive cancer cells of diverse origins. Experimental procedures Human tumor lines of various origins were treated with 10 μM of the p14MIS for 24 h or 48 h. The intracellular localization of p14MIS and growth suppression which is correlated to mitochondrial membrane potential by the p14MIS were examined by MTT assay and inverted fluorescence microscopy which is available to the peptide-treated living tumor cells. For in vivo study, the tumor xenograft mouse models were made by intraperitoneal injection of the human pancreatic adenocarcinoma cell, GFP-expressing BxPC3, and examined the antitumor effect of the peptide. The mice were daily treated with the 300ug/mouse of the p14MIS or with the polyarginine peptide (R9) as a control for a week, respectively. After the sequential treatment of the peptide, the mice of each group were autopsied and evaluated intraperitoneal dissemination (metastasis) of the GFP-expressing tumors. Results The p14MIS successfully targeted to the mitochondria and triggered an apoptosis to the various lineage of tumor cells by reduction of their mitochondrial membrane potential. The sensitivity and efficacy of the p14MIS was dependent on the expression level of endogenous mitochondrial ATPAF1 (F1-ATPase assembly protein) and also the magnitude of downregulation of the mitochondrial membrane potential in each tumor line. Moreover, in vivo delivery of the p14MIS to the pancreatic tumor model mice resulted in a 75% reduction in tumor volume compared with those in the control mice. Conclusions These results support the biological significance of the tumor suppressor molecule, p14ARF, especially localized at mitochondrias on tumor cells, and the utility of p14MIS peptide as an antitumor biotool against highly aggressive cancers. Although molecular details in tumor cells still remain to be clarified with respect to mitochondrial action of the p14MIS, it a potential of the peptide-based molecular therapy in intractable human malignancies of diverse origins. Citation Format: Ken Saito, Eisaku Kondo. Restoration of tumor suppressor function by mitochondrially targeting p14 peptide in tumor cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A144.