Abstract 3955: Epigenetic silencing of microRNA-34b/c plays a pivotal role in pathogenesis of small-cell lung cancers

Abstract

Abstract Background: Lung cancer is the leading cause of cancer-related death in the world. Small-cell lung cancer (SCLC) accounts for approximately 13% of lung cancers. Although chemotherapy results in initially high response rates, survival of patients with extensive stage disease is dismal. MicroRNAs (miRNAs) have been implicated in cancer initiation and progression via their ability to affect expression of genes that regulate cell proliferation and apoptosis. Recent studies have shown that, in cancer cells, expression of some miRNAs is silenced with DNA methylation in promoter region. Aberrant methylation of miR-34b/c has been reported in human malignancies, but not in SCLCs, causing up-regulation of oncogenes. In this study, we investigated the methylation and expression status of the miR-34b/c and the anti-proliferative effect by induction of miR-34b/c in SCLCs. Methods: We examined 11 SCLC cell lines and 6 resected primary SCLC tumors (one tumor treated with preoperative chemotherapy and five without preoperative chemotherapy). Methylation and expression status of miR-34b/c were determined by methylation-specific PCR and quantitative PCR, respectively. Colony formation assay was applied to examine the anti-proliferative effect by induction of miR-34b/c and scramble sequence control with plasmid vector. The ability of cell migration was examined using cell migration assay. Results: Aberrant methylation of miR-34b/c was found in 7 (64%) of 11 SCLC cell lines and 3 (50%) of 6 primary SCLC tumors. Expression of miR-34b/c in all methylation cell lines was silenced and restored with 5-aza-2’-deoxycytidine treatment, indicating that methylation caused gene silencing. Ectopic induction of miR-34b/c gene in SCLC cell line (H1048) showed significant inhibition of colony formation compared with induction of control vector, demonstrating anti-proliferative effect of miR-34b/c on SCLC. The cell migration was also significantly inhibited by induction of miR-34b/c in SCLC cell line tested. Conclusion: Our results demonstrated that miR-34b/c methylation is frequent in SCLCs and induction of miR-34b/c inhibits the cell proliferation and migration, resulting that miR-34b/c silencing plays an important role in pathogenesis of SCLCs. 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 3955. doi:10.1158/1538-7445.AM2011-3955