Abstract 1759: Description of molecular marker disparities and KRAS mutational spectrum of colorectal tumors from Puerto Rican Hispanics
Authors: Perez-Mayoral Julyann , Rivera-Lynch Camila , Soto-Salgado Marievelisse , Llor Xavier , Tous-Lopez Luis , Torres-Torres Marla , Reyes Jose S. , Torres Carlos , Goel Ajay , Rodriguez-Quillichini Segundo , Cruz-Correa Marcia 
Published: July 2017

Colorectal cancer (CRC) causes 27% of all cancer deaths among Puerto Rican Hispanics (PRH). Most CRC cases are due to sporadic genetic or epigenetic events that lead to the development of the tumor. These events aggregate to cause CRC carcinogenesis and involve genes that regulate cell growth and differentiation. Improving understanding of the molecular events that lead to CRC carcinogenesis has the potential to reduce CRC mortality by risk stratifying individuals as well as developing prevention strategies. Currently, there are a set of molecular markers that are used to characterize CRC tumors and inform prognosis and treatment decisions. These markers include: microsatellite instability (MSI), CpG island methylation and mutational analysis of the KRAS and BRAF oncogenes. The objective of this study was to characterize the molecular markers present in the CRC tumors of PRH and understand the disparities present at the molecular level in these tumors. The frequency of the MSI and CIMP were evaluated in 488 CRC tumors from PRH. Mutations in the KRAS gene and the BRAF V600E mutation were evaluated using SuperArray technology. Additionally, information regarding sociodemographic and clinicopathologic characteristics of the study population was obtained. Of the 488 evaluated CRC tumors 1.6% (n=2) showed MSI and 90.2% of the studied tumors had CIMP low phenotype (n=102). MSI-High tumors were more likely to be distal tumors compared to MSS tumors (p=0.02). The V600E mutation in the BRAF gene were found in 9.17% (n=11) of the studied tumors. KRAS mutations were found in 31.25% (n=40) of tumors. The most common KRAS mutations found in the CRC tumors of PRH were: c.35G&gt;A (KRAS COSMIC521) (n=12) and c.38G&gt;A (n=8) (KRAS COSMIC532). Furthermore, the traditional CRC carcinogenesis pathway was the predominant pathway observed for the development of the CRC tumors of our study population. The following study highlights a distinct molecular signature for the CRC tumors from PRH descent. The disparities observed in the prevalence of the molecular markers (low MSI, CIMP Low and mainly wild-type for KRAS and BRAF) suggest that the drivers for CRC in this population might differ from other populations. Additional studies are required to fully elucidate the CRC carcinogenesis pathway in PRH.

Citation Format: Julyann Perez-Mayoral, Camila Rivera-Lynch, Marievelisse Soto-Salgado, Xavier Llor, Luis Tous-Lopez, Marla Torres-Torres, Jose S. Reyes, Carlos Torres, Ajay Goel, Segundo Rodriguez-Quillichini, Marcia Cruz-Correa. Description of molecular marker disparities and KRAS mutational spectrum of colorectal tumors from Puerto Rican Hispanics [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 1759. doi:10.1158/1538-7445.AM2017-1759