Abstract 3618: Mutational analysis of colon tumors from African American patients and potential association with cancer disparities
Authors: Paredes Jenny , Garai Jone , Li Li , Baddoo Melody , Ji Ping , Imtiaz Sayed , Spagnardi Marzia , Akadri Mubarak , Gupta Raavi , Alshal Mohamed , Agaronov Maksim , Talus Henry , Williams Jennie L. , Martello-Rooney Laura , Zabaleta Jovanny 
Published: September 2020

Background: Colorectal cancer is the third most deadly cancer among African Americans (AA). When compared to Caucasian Americans (CA), AA present with more advanced disease and lower survival rates. We have previously demonstrated that colon tumors from AA and CA differ in their immune cell recruitment and their systemic cytokines secretion profiles. Therefore, in this study we investigated if differences in gene expression and mutational profiles could relate to the disparities observed between these populations.

Methods: We examined gene expression of colon tumor and non-tumor adjacent tissues from AA (n=20) and CA (n=20) by whole transcriptome sequencing (Illumina); and determined the differential expression of the 170 genes of the Illumina's TruSight Tumor 170 panel (TST170) in AA (n=12) and CA (n=17) colon tumor and non-tumor adjacent tissues.

Results: From our gene expression studies, we found that colon tumors from AA patients showed significant fold-change increases in gene expression when compared to CA for FOXP3 (6.97 vs. 3.15), IL1B (122 vs. 14) and IL8 (262 vs. 28) (p &lt; 0.05). In contrast, among CA we observed statistically higher gene expression of markers associated with antitumor activity such as GZMB (Granzyme B), IFNG and immunotherapy targets PDL1 (CD274) and CTLA4 (p &lt; 0.05). Through our mutational profiling we identified 38 genes in AA and 6 in CA differentially expressed between tumor and non-tumor tissues (p &lt; 0.01). Of those, 5 genes associated with several roles in cancer ETV4 (poor prognosis), CCND1 (tumorigenesis), FGFR2 (activation of the RAS-MAPK and the PI3K-AKT pathways) BRCA2 (genome stability), BCL2 (apoptosis regulator) were commonly altered in both cohorts.

Conclusions: Our study demonstrates significant differences in the genetic characteristics of colon tumors from AA compared to CA that suggest a deficiency of appropriate immune defense features in terms of gene expression. We also observed divergence in the mutational profiling between the groups, including numerous genes that are indicative of prognosis, treatment and outcomes in colon cancer. As such, these deficits could be mitigated through population-specific therapeutic approaches.

Citation Format: Jenny Paredes, Jone Garai, Li Li, Melody Baddoo, Ping Ji, Sayed Imtiaz, Marzia Spagnardi, Mubarak Akadri, Raavi Gupta, Mohamed Alshal, Maksim Agaronov, Henry Talus, Jennie L. Williams, Laura Martello-Rooney, Jovanny Zabaleta. Mutational analysis of colon tumors from African American patients and potential association with cancer disparities [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3618.