P2-04-02: Identification of a Novel Glycosyltransferase-Like Gene as an Autophagic Inducer in Human Mammary Carcinoma Cells Via Down Regulation of BCL-2.

Abstract

Abstract Here we report the identification of a previously undescribed glycosyltransferase-like gene, GLTx, and its cellular effect on mammary carcinoma cells. GLTx codes for a novel human protein which is highly conserved in primates. Data obtained from the mRNA expression database Oncomine, demonstrate that GLTx is differentially expressed in a variety of cancers including breast cancer. Western blot analysis of a multiple human tissue blot using a rabbit polyclonal antibody against GLTx demonstrated that GLTx was highly expressed in liver, moderately in kidney, intestine and stomach and undetectable in any other tissues. To functionally characterize GLTx, we attempted to establish stable cell lines with forced expression. However, forced expression of GLTx was completely lethal and resulted in severe cell death in the mammary carcinoma cell lines, MCF-7 and BT549, as well as in any other cell lines tested. Staining of MCF-7 cells transiently transfected with a GLTx expression plasmid by either Hoechst 33258 or fluorescein isothiocyanate-conjugated annexin V and propidium iodide confirmed that the observed cell death was not caused by apoptosis. Further investigation confirmed that GLTx expressing cells exhibited cytoplasmic accumulation of autophagosomes, consistent with the induction of autophagy, as measured by the fluorescently labelled autophagosome marker LC3. In addition we have shown that GLTx downregulated BCL-2, an inhibitor of autophagy, as measured by BCL-2 gene promoter luciferase activity assay and western blot assay following transient transfection of a GLTx expressing plasmid. Thus, we have demonstrated that GLTx is a novel autophagic inducer that causes cell death by down regulating BCL-2. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-04-02.