Abstract 2052: MicroRNA-101 promotes apoptosis and suppresses proliferation in esophageal squamous cell carcinoma by repressing the polycomb group protein EZH2

Abstract

Abstract Background: MicroRNAs (miRNAs) are ∼22 nucleotide non-coding RNA molecules that regulate gene expression post-transcriptionally. Although aberrant expression of miRNAs has been observed in various types of human cancer, their pathophysiologic role and their relevance to tumorigenesis are still largely unknown. Overexpression of the enhancer of zeste homolog 2 (EZH2) protein, a known repressor of gene transcription, has been reported to be associated with biological malignancy in several types of cancer. Purpose: The aim of this study was (1) to analyze the expression and function of microRNA-101 (miR-101) in esophageal squamous cell carcinoma (ESCC), (2) to elucidate the regulation of the EZH2 expression by miR-101 as its target gene. Methods: miR-101 expression was investigated in 27 matched normal esophageal epitheliums and ESCCs and 12 ESCC cell lines (TE1, 4, 6, 8, 9, 10, 11, 12, 13, 14, 15, KYSE30) by TaqMan quantitative real-time-polymerase chain reaction (qRT-PCR). To evaluate the role of miR-101, cell proliferation and apoptosis was analyzed with pre-miR-101-precursor transfected cells. Next, the regulation of EZH2 by miR-101 was analyzed by real-time PCR and western blotting. In addition, to elucidate the role of EZH2 gene in ESCC, we immunohistochemically examined the expression of EZH2 protein in 120 resected ESCC specimens and determined its association with the clinicopathological characteristics and prognosis. Results: In matched 27 resected specimens, the expression of miR-101 was significantly down-regulated in ESCCs compared with normal epitheliums. All 15 ESCC cell lines also showed down-regulation of miR-101. Pre-miR-101-precursor transfected cells promote cellular apoptosis and showed significant reduction in cellular proliferation. Pre-miR-101-precursor transfected cells significantly repressed EZH2 expression in both mRNA level and protein level. In the immunohistochemical analysis of EZH2, 78 (65%) showed positive staining, while 42 (35%) lacked the staining. Positive staining for EZH2 was associated with a poor prognosis significantly. Conclusions: miR-101 promotes apoptosis and suppresses proliferation in ESCC by repressing EZH2 expression as a tumor-suppressive-microRNA. It plays an important role in progression of ESCC and may serve as a novel therapeutic target. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2052.