Abstract 1870: Green tea polyphenol EGCG upregulates mir-210 expression in lung cancer cells by transiently stabilizing HIF1α

Abstract

Abstract Epigallocatechin-3-gallate (EGCG) has been reported to affect many cellular regulatory pathways. This study aims to determine whether EGCG could target microRNA, one of the mechanisms for cells to achieve subtle change in multiple targets. We found that, in both human and mouse lung cancer cells in culture, EGCG specifically upregulated the expression of mir-210, a major microRNA regulated by HIF1α. Furthermore, we found that overexpression of mir-210 led to reduced cell proliferation rate and anchorage-independent growth as well as reduced sensitivity to EGCG. To explore the mechanisms of mir-210 regulation by EGCG, we demonstrated that the regulation was mediated through hypoxia-response element in mir-210 promoter. Consistently, the upregulation of mir-210 was found to be correlated with the transiently stabilized HIF1α in lung cancer cell lines after EGCG treatment. Such stabilization was further shown by the stabilization of HA-tagged HIF1α, but not the P402A/P564A mutated HIF1α, by EGCG, suggesting that EGCG targets the oxygen-dependent degradation (ODD) domain. Direct evidence was obtained by affinity binding assay showing that EGCG specifically binds HIF1α with a Kd=3.47 μM. This result implies that EGCG binding interferes with the hydroxylation of key Pro residues in the ODD domain, preventing HIF1α from the Pro hydroxylation-induced ubiquitination and subsequent proteosome-mediated degradation. In summary, our results demonstrate the elevation of mir-210 by EGCG and this is mediated by the stabilization of HIF1α. This event may contribute to the anti-cancer activity of EGCG (Supported by NIH grant CA 122474 and CA133021). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1870. doi:10.1158/1538-7445.AM2011-1870