Abstract 2235: High frequency of fusion transcripts involving TCF7L2 in colorectal cancer: Novel fusion partner and splice variants

Abstract

Abstract VTI1A-TCF7L2 was reported as a recurrent fusion gene in colorectal cancer (CRC), found to be expressed in three out of 97 primary cancers, and one cell line, NCI-H508, where a genomic deletion joins the two genes (Bass et al. Nature Genetics, 2011). To investigate this fusion further, we analyzed high-throughput DNA and RNA sequencing data from seven CRC cell lines in addition to publicly available data from the NCI-H508 cell line. From both genome and transcriptome data, the gene RP11-57H14.3 (ENSG00000225292) was identified as a novel fusion partner for TCF7L2 in the HCT 116 cell line. The originally reported fusion VTI1A-TCF7L2 was identified as expected from the analysis of NCI-H508 data. By triplicate nested RT-PCR, we tested both the novel fusion transcript and VTI1A-TCF7L2 for expression in a series of 106 CRC tissues, 21 colon cancer cell lines, 14 normal colonic mucosa, and 20 normal tissues from miscellaneous anatomical sites. Altogether, 42% and 45% of the CRC samples expressed VTI1A-TCF7L2 and TCF7L2-RP11-57H14.3 fusion transcripts, respectively. The two fusion transcripts were both seen in 29% of the normal colonic mucosa samples, and in 25% and 75% of the tested normal tissues from other organs. Seven different splice variants were detected for the VTI1A-TCF7L2 fusion, of which three are novel. Four different splice variants were detected for the TCF7L2-RP11-57H14.3 fusion. In conclusion, we have identified novel variants of VTI1A-TCF7L2 fusion transcripts, including a novel fusion partner gene, RP11-57H14.3. We demonstrated detectable levels of TCF7L2 involving fusion transcripts in a large fraction of CRC samples, as well as in normal colonic mucosa and other normal tissue types, revealing that these fusions, at transcript level, are neither specific to cancer nor to the colon and rectum. Citation Format: Andreas M. Hoff, Torfinn Nome, Anne Cathrine Bakken, Torleiv O. Rognum, Arild Nesbakken, Rolf I. Skotheim. High frequency of fusion transcripts involving TCF7L2 in colorectal cancer: Novel fusion partner and splice variants. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2235. doi:10.1158/1538-7445.AM2014-2235