Abstract 1438: The dynamics of genetic aberrations in Crohn's disease associated colorectal carcinogenesis

Abstract

Abstract Crohn’s disease, a condition of chronic inflammation of the intestine, significantly increases the risk for the development of colorectal cancer (CRC). Sporadic CRCs are characterized by a specific pattern of genomic imbalances and a landscape of acquired gene mutations. In this study we aimed to compare CRCs that arise as a consequence of chronic inflammation in Crohn’s disease with sporadic CRCs. We analyzed 26 Crohn’s disease associated CRCs, four matched dysplastic lesions, six matched inflamed mucosa samples, and two matched lymph node metastases using array comparative genomic hybridization, targeted sequencing (564 cancer related genes) and gene expression profiling. As a control, we used normal intestinal mucosa from the resection margin of these CRCs and 24 sporadic CRCs. In general, CRCs that developed in patients with Crohn’s disease had a similar distribution of genomic imbalances compared to sporadic CRC. However, we identified distinct mutation signatures: in the Crohn's disease associated CRCs the most frequently mutated gene was TP53, which occurred in 65% of the samples. The second, third and fourth most frequently mutated genes were KRAS (27%), APC (23%) and PIK3CA (19%). In the control group of sporadically arising CRCs, the most commonly mutated gene was APC (75%), followed by KRAS (54%), TP53 (33%), SMAD3 (29%) and SMAD2 (25%). The genetic analyses of multiple lesions from individual patients revealed a high degree of intertumoral heterogeneity with diverse patterns of gene mutations and allowed the reconstruction of the sequence of genetic events during Crohn’s disease associated tumorigenesis. In contrast to sporadic colorectal carcinogenesis, TP53 mutations were observed as early and common events while APC mutations occurred rather late and were infrequent. Our comprehensive molecular profiling of Crohn’s disease associated CRCs suggests that the genetic landscape of CRC is influenced by the activation of inflammation related pathways. Furthermore, our findings offer potential for establishing an early detection marker for dysplasia in patients with Crohn’s disease. Citation Format: Daniela D. Hirsch, Darawalee Wangsa, Yue Hu, Jack Zhu, David Petersen, Daniel C. Edelman, Paul S. Meltzer, Bao Tran, Kerstin Heselmeyer-Haddad, Thomas Ried, Timo Gaiser. The dynamics of genetic aberrations in Crohn's disease associated colorectal carcinogenesis [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 1438. doi:10.1158/1538-7445.AM2017-1438