P2.03-47 Deregulation of a Novel Cis-Acting lncRNA in Non-Small Cell Lung Cancer May Control HMGA1 Expression

Abstract

Since the discovery of long non-coding RNAs (lncRNAs), they have been increasingly implicated in cancer-associated phenotypes. Recently, some lncRNAs have been shown to regulate the expression of neighbouring protein-coding genes, including oncogenes and tumour suppressor genes. High mobility group A1 (HMGA1) is aberrantly expressed in several aggressive cancer types, including non-small cell lung cancer (NSCLC), where high HMGA1 expression has been associated with poor overall survival and chemotherapy resistance. While HMGA1 is known to be deregulated in lung cancer, the mechanisms that mediate its expression remain unknown. These lncRNAs, known as cis-acting, may represent undiscovered therapeutic action points in cancer driving pathways. Here we investigate the deregulation of a putative cis-acting lncRNA in NSCLC, and its relationship with the oncogene HMGA1. LncRNA expression was generated from RNA-sequencing data from 36 microdissected tumour and matched non-malignant tissues. Normalized sequence read counts were used to identify transcripts with significantly deregulated expression (Wilcoxon Signed-Rank Test, BH-p<0.05). Validation was performed in sequencing data obtained from The Cancer Genome Atlas (TCGA). SiRNA-mediated knockdown of lncRNA candidates were performed in a non-malignant epithelial lung cell line (BEAS-2B). Quantitative real-time PCR was used to observe the effects of lncRNA knockdown on the expression of neighbouring protein-coding genes. Our analyses identified a lncRNA neighbour to HMGA1, RP11.513I15.6, to be significantly downregulated in 2 cohorts of LUAD samples. Conversely, we found HMGA1 expression to be significantly overexpressed in LUAD tumours, and was found to be anticorrelated with RP11.513I15.6. Additionally while RP11.513I15.6 decreased with tumour stage, HMGA1 expression increased with stage. In vitro experiments demonstrated siRNA-mediated inhibition of RP11.513I15.6 in immortalized lung epithelial cells resulted in a significant increase in HMGA1 expression. Our results suggest that RP11.513I15.6 is a novel cis-acting lncRNA that negatively regulates HMGA1, and may contribute mechanistically to the maintenance of lung cancer phenotypes. Further characterization of this oncogene regulatory mechanism may uncover a novel therapeutic intervention point for tumours driven by HMGA1.