Role of CD8+ T-cell infiltration in breast tumors of Black women compared to White women.

Abstract

e13608 Background: Literature regarding racial differences in tumor immune responses in breast cancer remains sparse. To address this research gap, we assessed CD8+ T-cells in breast tumor samples from the Women’s Circle of Health Study (WCHS) population of predominantly Black breast cancer patients. We characterized and compared the density of CD8+ T cells, their prognostic value and their association with pharmacologic beta-blockers. Prior studies suggest that reducing adrenergic signaling through beta blockers can stimulate CD8+ T-cells. Methods: Tumor-infiltrating CD8+ T-cells were assessed by IHC staining of tissue microarray cores from 688 breast cancer patients, including 550 Blacks and 138 Whites. CD8+ T cells were scored with digital image analysis. Comparisons of demographic and clinical variables (including CD8+ T cell density) were made using the Mann-Whitney U or Kruskal-Wallis and Fisher’s exact tests. Associations with overall survival (OS) and disease-specific (DSS) survival were evaluated using the log-rank test of Cox regression. Analyses were performed in the overall sample and by disease sub-type. Results: Higher CD8+ T cell density was seen in Black women compared to White, with mean values of 756.2/mm2 and 292.4/mm2 respectively (p < 0.001). Within the overall population and in black women, CD8+ T cell density was significantly higher in younger patients, patients with high grade, and ER negative tumors. No significant associations were observed between CD8+ T cell density and OS or DSS. However, when stratified by subtype, Black patients with triple negative breast cancer and high CD8+ T cell density showed a trend towards improved OS in comparison to patients with low CD8+ T cell density (p = 0.065). 170 patients with information on beta blocker usage were analyzed. No significant associations were noted between CD8+ T cell density and beta blocker use. Conclusions: We observe a significantly higher CD8+ T cell density in Blacks compared to Whites, but this does not confer a survival advantage. Additionally, beta-blockers did not seem to enhance CD8+ T cell infiltration in tumors from Black patients. Our data raise the possibility that distinct mechanisms of immune cell action may occur in different racial groups. Future studies are needed to determine the functional properties of CD8+ T cells in Black women and to characterize additional immune cell subtypes that may also play a role.