Colorectal cancer (CRC) is the third most common cancer among African Americans (AAs) in the US. When compared to Caucasian Americans (CAs), AAs present with higher incidence and death rates as well as worse prognosis after treatment with 5-Fluorouacil (5-FU). Previous studies have shown a correlation between microsatellite instability (MSI) and response to 5-FU and our recent findings suggest that differences in the tumor immunology and MSI status of AA and CA CRC patients are associated with the observed disparities between these populations. Therefore, we examined if cytokines secretion, protein production and cellular response to 5-FU treatment, differs between colon cancer cell lines from AAs generated in Dr. Williams’ laboratory (SB521, SB501 and CHTN06) and colon cancer cell lines from CA patients (HT29 and HCT116). Methods: We performed whole transcriptome sequencing of colon cancer cell lines (RNAseq), utilizing the NextSeq 500/550 High Output Kit v2.5 (Illumina) and Partek Flow data analysis to correlate gene expression to immune-oncology pathways. ELISA assays (RayBiotech) were used to examine the secretion of cytokines in supernatants from cells treated with interleukin 1β and tumor necrosis factor alpha. We used western blotting for protein detection of the phosphorylated form of c-Jun N-terminal kinases (JNK) as well as cell viability assays for establishing the IC50 of the cell lines to 5-FU. Results: The gene expression results indicated that the immune profiles of AA cell lines differ from CA in genes and cytokines related to cellular anti-tumor activity, including CD8B, IL-1R, IL-1R2, Granzyme B and NFKB. ELISAs of supernatants from CA and AA CRC cell lines revealed a differential cytokines secretion between the two races, namely IL-8. Lastly, the MSI AA cell line showed sensitivity to 5-FU (tenfold less) when compared to the CA cell lines and a distinct protein production pattern. Conclusions: Our gene expression findings demonstrated the differential expression of immunological pathways involved in immune-surveillance and cancer progression in the CRC cell lines between the two races. These results were in accordance with the cytokines’ and protein’s expression patterns observed in the two cohorts of cell lines. Importantly, our data indicates that 5-FU is more efficient in reducing cell viability in the MSI AA cell line than in the two CA cell lines regardless of their MSI status. Altogether, our results illustrate the value of these in vitro models to study 5-FU treatment in AA patients with MSI and MMR mutations and to elucidate the differences in chemotherapy treatment responses between AAs and CAs. In conclusion, we demonstrated distinct immunological profiles and 5-FU sensitivity of AA and CA CRC cell lines. As such, these differences observed could be used to guide new therapeutic strategies.

Citation Format: Marzia Spagnardi, Jenny Paredes, Jone Garai, Ping Ji, Ellen Li, Jovanny Zabaleta, Laura Martello-Rooney, Jennie Williams. Tumor biology and cancer health disparity: Gene expression, cytokine secretion, and protein production in African American colon cancer cell lines [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B134.