Abstract 2842: Vesal Yaghoobi

Abstract

Abstract Background: It has been shown that even after adjusting for clinical stage at presentation and socio-economic variables, Triple Negative Breast Cancer (TNBC) still has a worse overall outcome in African American (AA) compared to Non-African American (NAA) patients. The abundance and composition of immune cells in the tumor microenvironment is a powerful prognostic factor in TNBC. Our goal was to assess if differences exist in CD8, CD68 and PD-L1 protein expression between AA and NAA TNBC. We hypothesize that the microenvironment of African AA TNBC patients may be different than that of NAAs. Method: We selected N=43 AA and N=43 NAA TNBC samples from the Yale Pathology archives that were matched by diagnosis date. We measured CD8, CD68 and PD-L1 protein expression in both the tumor and stromal compartments in whole slides from formalin fixed paraffin embedded (FFPE) tissues using multiplexed quantitative immunofluorescence (QIF). The average of each marker expression was calculated in all Fields of View (FOV), and the top 10% brightest FOV of each slide (i.e. hotspot). Results: The frequency of macrophages, as assessed by the expression of CD68 was significantly higher in AA compared to NAA. This was seen by overall assessment for all FOV (mean NAA=2273au versus mean AA=3627au; p = 0.0052), and in hotspot FOVs (mean NAA=4858au versus mean AA=6371au; p = 0.0411), and also for assessments in tumor and stromal subcompartments. Expression of CD8 positive cytotoxic T cells was significantly lower in AA compared to NAA, but only when measuring hotspots in the tumor compartment (p=0.017). Conclusion: The significantly higher CD68 and lower CD8 expression in AA compared to NAA TNBC might contribute to a more immune attenuated microenvironment. We are currently further characterizing the macrophage polarity and the cytokine milieu of these samples. Citation Format: Vesal Yaghoobi, Vasiliki Pelekanou, Tess O'Meara, Andrea Silber, Lajos Pusztai, David Rimm. Vesal Yaghoobi [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2842.