Novel immune cell subtypes linked to survival among African American women with triple-negative breast cancer

ABSTRACT Triple negative breast cancer (TNBC) is an aggressive disease that is twice as likely to be diagnosed in African American (AA) women compared to white women, with poor clinical outcomes. Tumor infiltrating lymphocytes (TILs) are associated with improved survival for TNBC, but the relevance of TILs and immune cell subtypes to survival in AA women with TNBC is unknown. We evaluated histopathologic TIL counts and molecular characteristics among 60 AA women diagnosed with TNBC with linkage to clinical outcomes using data from the Metropolitan Detroit Cancer Surveillance System. We utilized whole genome expression profiling of TN tumors and cell type deconvolution analysis to evaluate the underlying mechanisms and immune cell subtypes associated with survival patterns in the context of TILs. TILs were significantly associated with improved survival [1-10% Hazard Ratio (HR)=0.32, 95% Confidence Interval (CI) 0.12-0.90, p=0.031; >10% HR=0.18, 95% CI 0.05-0.67, 9.9×10 −3 ]. 524 transcripts (326 coding, 198 non-coding) were associated with TIL levels, 34 of which were associated with both TILs and survival (p<0.05). While only naïve B cells were associated with survival when considering individual cell types [Median HR=2.43, 95% CI 1.07-5.55, p=0.035], increased naïve B cells, plasma cells, and activated NK cells, and decreased resting mast cells, M1 macrophages, and monocytes were associated with transcripts that predicted worse survival. These data provide evidence for novel roles for these immune cells types in TNBC, and further studies are needed to validate these findings and identify determinants of patterns of immune response in TNBC relevant to the AA population. Summary We found that increased naïve B cells, plasma cells, and activated natural killer cells, and decreased resting mast cells, M1 macrophages, and monocytes were associated with expression biomarkers of worse survival among African American women with triple negative breast cancer.