Abstract 3483: Genome-wide analysis of the antisense transcriptome in cancer

Abstract Natural antisense transcripts (NATs) are the most abundant class of long noncoding RNAs (lncRNAs). Importantly, NATs are one of the most unknown ncRNAs. However, due to their highly gene locus-specific effects, NATs may provide a unique entry point for therapeutic intervention in targeted gene regulation. For this reason we are interested in studying the regulation of sense/antisense transcription in cancer related locus. In our previous work we found that, at the important cancer-related locus vimentin (VIM) there is a previously uncharacterized antisense transcript (VIM-AS1), which is transcribed head-to-head with VIM gene. This antisense transcript enhances R loop formation; it allows the binding of transcription factors as NF-kB, low nucleosome occupancy and the transcription of VIM gene. Our results are the first example of R loop mediated enhancement of gene expression involving head-to-head antisense transcription at cancer related locus. We also observed that in colon and breast cancer there was a positive expression correlation between VIM and VIM-AS1 and we have observed that hypermethylation silences both transcripts in colon primary tumors. In the present work we have seen that this positive correlation between sense and antisense transcripts is present in most of the tumor types from patients that we have obtained from Genomic Data Commons Data Portal (GDC Portal). Importantly this positive correlation correlates better in the cases in which the antisense transcript is downregulated or maintains the expression than in tumors where VIM and VIM-AS1 are up-regulated. Furthermore, we wanted to see if the cellular function is also coordinated. VIM is a component of the intermediate filament family of proteins that has an important role in epithelial mesenchymal transition. We found that specific depletion of VIM-AS1 results in a decrease of VIM expression, and now we have found that this depletion produces low migration rate and more invasion capability, as expected. On the other hand, the mechanisms used by antisense transcripts to regulate their corresponding sense mRNAs are not fully understood and in view of these results we are investigating from a genome-wide perspective the regulation of sense/antisense transcription, the involvement of R loop structures and DNA methylation in cancer. For this, we have applied a number of techniques: RNAseq strand specific, Illumina’s HumanMethylation450 Bead Chip array, RNAseq strand specific with overexpression of RNaseH (which specifically degrades the RNA in RNA/DNA hybrids), and DRIPseq (which immunoprecipitates the hybrids DNA-RNAs). The analysis of these data sheds light on the study of the role of sense/antisense transcripts in cancer-related locus. Citation Format: Raquel Boque-Sastre, Manuel Castro de Moura, Antonio Gomez, Sònia Guil, Manel Esteller. Genome-wide analysis of the antisense transcriptome in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3483. doi:10.1158/1538-7445.AM2017-3483