Abstract C33: N-terminal fragment of Bit1 apoptotic protein induces autophagy in tumor cells

Abstract

Abstract Bit1 is a proapoptotic mitochondrial protein associated with anoikis, cell death resulting from the loss of cell attachment to extracellular matrix. Upon cell detachment, Bit1 is released into the cytoplasm, where it complexes with the Groucho family protein amino-terminal enhancer of split, and triggers cell death through a caspase-independent pathway. Bit1 consists of 179 amino acids; the N-terminal 62 amino acid mitochondrial localization domain, a transmembrane domain, and the C-terminal peptidyl-tRNA hydrolase domain. In the present study, we localized the Bit1 cell death domain (BCDD) to the N-terminal 62 amino acids of Bit1 by introducing truncated Bit1 proteins into the cytoplasm with cDNAtransfection and protein transduction. BCDD was more potent than the full-length Bit1 protein, when equivalent amounts of cDNA was transfected. Treatment of cultured prostate and breast cancer cells with recombinant proteins in which BCDD was fused with two cell-internalizing peptides, one of which is tumor specific, also caused cell death. Bit1 and BCDD shared the characteristics previously attributed to Bit1-induced cell death. In addition, we found that the cells exhibited the signs of autophagy. These results define the cell death domain in Bit1 and reveal autophagy as the main mechanism of Bit1-induced cell death. Tumor-targeted exogenous BCDD may have potential as an anticancer agent. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C33.