Abstract 2057: Cigarette smoke enhances pulmonary carcinogenesis via downregulation of has-miR-487b in respiratory epithelial cells

Abstract

Abstract Limited information is available regarding the mechanisms by which miRNA alternations contribute to initiation and progression of lung cancer. In order to examine this issue, array techniques were used to assess miRNA expression profiles in short term normal human bronchial epithelia (NHBE) and small airway epithelial cells (SAEC), as well as A549 and Calu-6 lung cancer cells cultured in normal media (NM) with or without cigarette smoke condensate (CSC). Under relevant exposure conditions, CSC consistently mediated a 3.4 − 5.5 fold decrease in has-miR-487b expression in cultured normal as well as lung cancer cells. Quantitative RT-PCR experiments demonstrated that expression levels of has-miR-487b were significantly downregulated (2.9 − 21 fold) in a panel of resected lung cancers relative to adjacent normal tissues. Software-guided analysis revealed numerous potential targets for has-miR-487b including H2AZ, encoding a histone variant modulating expression of developmentally regulated genes as well as SUZ12, which encodes a component of polycomb repressor complexes implicated in aberrant silencing of tumor suppressor genes such as Dickkopf-1 (Dkk-1) in lung cancer cells. Quantitative RT-PCR experiments revealed that constitutive over-expression of has-miR-487b mediated 3-35 fold reductions in H2AZ and SUZ12 expression in SAEC, A549, and Calu-6 cells. RNA cross-link immunoprecipitation (CLIP) experiments confirmed direct interference of has-miR-487b with H2AZ and SUZ12 transcripts. Overexpression of has-miR-487b enhanced sensitivity to cisplatin in lung cancer cells. Collectively, these data suggest that CSC-mediated downregulation of has-miR-487b promotes pulmonary carcinogenesis, in part, via activation of genes encoding proteins implicated in epigenetic regulation of stem cell gene expression. 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 2057.