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Immune-Related Gene Expression and Cytokine Secretion is Reduced Among African American Colon Cancer Patients

ABSTRACT: 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. Here, we investigated if differences in tumor immunology could contribute to the disparities observed between these populations. Methods: We examined gene expression of 20 tumor and 20 non-tumor adjacent tissues from AA and the same number from CA by whole transcriptome sequencing and generated scores for immune cell populations by NanoString. In addition, we utilized “The Cancer Genome Atlas” (TCGA) database from AA (n = 55) and CA (n = 193) as a validation cohort. Finally, we measured the secretion of cytokines characteristic of effector T helper cell (Th) subsets by ELISA using plasma from each AA and CA participant. Results: Colon tumors from AA patients showed significant fold-change increase in gene expression when compared to CA for FOXP3 (6.97 vs. 3.15), IL1B (122 vs. 14) and IL8 (262 vs. 28) (p < 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 < 0.05). TCGA data validated our observed higher expression of GZMB and PDL1 in CA patients as well as showed a 50% higher 5-year survival rate in AA patients with high expression of GZMB. Notably, our observations on immune cell populations show that AA tumors have significantly higher number of exhausted CD8+ cells (p < 0.01), mast cells (p < 0.02) and increased T regulatory cells when compared to CA. AA colon cancer patients differed from CA in cytokine production patterns in plasma (i.e. reduced IL-12). Conclusions: Our study demonstrates significant differences of the immunological profiles of colon tumors from AA compared to CA that suggest a deficiency of appropriate immune defense mechanisms in terms of gene expression, recruitment of immune cells and systemic secretion of cytokines. As such, these immune differences could be mitigated through population-specific therapeutic approaches.

ORGANISM(S): Homo sapiens

PROVIDER: GSE146009 | GEO | 2020/09/23

REPOSITORIES: GEO

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Project description:Background: African Americans (AA) have increased burdens of cardiovascular disease and cancer compared to Caucasian Americans (CA). This study addresses the possibility that genetic differences affecting the biology of the vascular endothelium could be a factor contributing to this health disparity. Methods: From self-identified, healthy, 20-29 year old AA (n=21) and CA (n=17), we established cultures of blood outgrowth endothelial cells (BOEC) and applied microarray profiling. BOEC have never been exposed to in vivo influences, and their gene expression reflects culture conditions (meticulously controlled) and donor genetics. Analysis used two distinct approaches. Significance Analysis of Microarray, a FDR-based test, identified significant differential expression of single genes. Gene Set Enrichment Analysis examined expression of pre-determined gene sets that survey each of nine biological systems relevant to endothelial cell biology. Results: At the highly stringent threshold of FDR=0, we identified 31 single genes that were differentially expressed, 4 higher and 27 lower in AA. “PSPH” exhibited the greatest fold-change (AA>CA), but this was entirely accounted for by a homolog (PSPHL) hidden within the PSPH probe set. Among other significantly different genes were: for AA>CA, SOS1, AMFR, FGFR3; and for AA<CA, ARVCF, BIN3, EIF4B. Many more (221 transcripts for 204 genes) were differentially expressed at the more customary, less stringent threshold of FDR<.05. Using the biological systems approach, we identified shear response biology as being significantly altered for AA versus CA. It detected an apparent tonic increase of expression (AA>CA) for 46/157 genes within that system. Conclusions: The most significant single gene changes detected for AA involved genes having substantial, known roles in endothelial biology. Biological systems analysis suggested that shear stress response, a critical regulator of endothelial function and vascular homeostasis, may be different between AA and CA. These results potentially have direct implications for the role of endothelial cells in both vascular disease (e.g., hypertension and stroke) and cancer (via angiogenesis). The present findings are consistent with our overarching hypothesis that genetic influences stemming from ancestral continent-of-origin could impact upon endothelial cell biology and thereby contribute to disparity of vascular-related disease burden amongst AA.

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Immune-Related Gene Expression and Cytokine Secretion is Reduced Among African American Colon Cancer Patients

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