Abstract 2261: Heat-shock and autophagy in cancer: Novel role for DGK iota
| Autor: | Christina T.K. Wales, Buddhini Samarasinghe, Aaron T. Jacobs |
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| Rok vydání: | 2012 |
| Předmět: | |
| Zdroj: | Cancer Research. 72:2261-2261 |
| ISSN: | 1538-7445 0008-5472 |
| DOI: | 10.1158/1538-7445.am2012-2261 |
| Popis: | Autophagy is a cellular process by which damaged proteins, protein aggregates, and organelles are sequestered by lysosome-like compartments and degraded. Autophagy contributes to quality control, cell death, and senescence. Defects in autophagy cause the accumulation of cellular damage, inhibit cell death processes, and promote an inflammatory state that facilitates tumor development. In contrast, the heat shock response, which is mediated primarily by the transcription factor, HSF1 is frequently enhanced in cancer. Despite this inverse relationship between autophagy and heat-shock in cancer, the direct influence of heat-shock and HSF1-mediated gene expression on autophagy has not been investigated. Our study suggests that heat-shock mediated gene expression suppresses autophagy in a human colorectal cancer cell line. Our data show that diacylglycerol kinase iota (DGK iota) expression is regulated by HSF1. DGK iota phosphorylates diacylglycerol, generating phosphatidic acid (PA), which is a potent suppressor of autophagy through its activation of the serine/threonine kinase mTOR (mammalian target of rapamycin). The aim of our study was to evaluate the influence of HSF-1-mediated gene expression on autophagy, and to examine the specific contribution of DGK iota in this effect. We utilized RKO colorectal cancer cells for this investigation and assayed autophagy using complimentary techniques, including: conversion of LC3-I to LC3-II, which was monitored by Western blot; and the formation of autophagic vesicles (autophagosomes), which were visualized by high-content screening confocal microscopy of cells harboring an LC3-GFP expression construct. The influence of basal and heat-shock (42°C)-simulated HSF1 activity on autophagy was analyzed using siRNA. Silencing of HSF1 led to a profound increase in autophagic markers, suggesting a role for HSF1-driven gene expression in the suppression of autophagy. In HSF1-deficient cells we also observed increased phosphorylation of p70S6K, which is a surrogate marker for mTOR activation. We confirmed that DGK iota mRNA and protein expression is mediated by HSF1. Using biochemical inhibitors of DGK activity, we observed a significant increase in autophagy, supporting our hypothesis that DGK iota participates in suppressing autophagy. Additional siRNA experiments of DGK iota are being performed to confirm this effect, along with measurements of cellular PA levels. Taken together, these results indicate an important role for HSF1 in the suppression of autophagy, and provides mechanistic insight into a potential, tumor-promoting role for DGK iota. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2261. doi:1538-7445.AM2012-2261 |
| Databáze: | OpenAIRE |
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