Comparative genomic analysis to identify a signature of sporadic colorectal cancer development in young adults.

Abstract

208 Background: Young-onset sporadic CRC is an important yet understudied heterogeneous group of aggressive cancers with distinct clinical and histopathological features. There is a steady increase in the incidence of cancer in this group of patients and currently, there are no screening guidelines to identify these patients due to a lack of understanding of the molecular mechanisms driving cancer in this patient group. Introduction: Despite screening guidelines and recent advances in cancer treatment, colorectal cancer (CRC) remains the second most diagnosed cancer and the second and third leading cause of cancer-related mortality in Canadian men and women, respectively [Canadian Cancer Statistics 2017.]. More striking is the rise in incidence of CRC in young adults in the United States [Siegel, R.L., et al, Bailey, C.E., et al., Dozois, E.J., et al., Deen, K.I., et al.], and the expectation that by the year 2030, the incidence rate will increase by 90% in this patient population. Data from the Surveillance and Cancer registry at Cancer Care Ontario shows a similar trend with increased rates in younger adults (ages 30 to 49) by 5.2 per cent per year between 2005 and 2012 [Ontario, C.C., Cancer Fact.]. Moreover, these younger patient groups are often diagnosed with aggressive forms and advanced stages of the disease [Ontario, C.C., Cancer Fact.]. Methods: In this study, using a total of 30 colorectal cancer patient samples from Windsor Regional Hospital Cancer Program, we performed comprehensive targeted gene sequencing to identify single nucleotide variants, small insertions/deletions, copy number variants in over 500 genes that are implicated in cancer. Mean age of the patients in this study was 44 years and only patients without any personal or family history of colon cancer /other malignancies or IBD were enrolled in the study. Results: While identifying previously known colorectal cancer associated genetic variants, our preliminary data shows distinct missense mutations in several genes potentially contributing to the development and progression of cancer in these patients. In addition to showing pathogenic mutations in colorectal cancers associated genes, such as PIK3CA (H1047R, E545K, E545G, R93W, V344A), KRAS (G12V, G12D, A146T) and APC, our study showed recurring missense mutations in several genes including AXIN2, ALK, CDKN1A, MAP3K1, ROS1, EPCAM, KDM5A and AURKA in over 50% of our samples. Conclusions: The genomic profiling performed using biopsies from young colorectal cancer patients through this study provides a unique ability to identify the potential “genomic triggers” for the development and progression of cancer in young sporadic colorectal cancer patients. This information can not only be used to develop targeted treatment options for these patients but also to design new screening protocols as well as optimal surveillance strategies.