Abstract P4-04-09: CD4 and CD8 T cell densities are increased in benign breast disease compared to normal breast tissue

Introduction: CD4+ and CD8+ T cells are important effector cells in the adaptive immune response against cancers. In premalignant proliferative breast tissues, the role of the immune system remains relatively undefined. In this study, we sought to investigate and quantify the presence of CD4 and CD8 expressing immune cells in benign breast tissues and their association with breast cancer risk. Method: Archived breast tissue samples from women with benign breast disease (BBD) or no clinical breast disease [Komen Tissue Bank (KTB)] were obtained for this age-matched case-control study. BBD samples included BBD cases (subsequently developed breast cancer) and BBD controls). Tissue sections were characterized for non-proliferative or proliferative disease and degree of lobular involution. CD4+ and CD8+ cell densities (cells/mm 2 ) were obtained by digital image quantitation for up to 10 individual lobules per sample and a per-sample estimate of cell density was calculated as the median cell density across lobules within a sample. Statistical analysis was performed using Wilcoxon signed-rank and Kruskal-Wallis tests. Results: Among 267 women (median age 52, range 35-75) comprising 89 age-matched triplets, 2417 lobules were evaluated [783 KTB, 804 BBD case, 830 BBD control]. 1372 (57%) lobules were normal and 1045 (43%) were fibrocystic. CD4+ cells were present in 1903 (79%) lobules while CD8+ cells were present in 2214 (92%) lobules. CD4 and CD8 densities showed a moderate positive correlation (r = 0.39) with each other, but overall, lobules showed a lower density of CD4+ than CD8+ cells (mean difference -54 cells/mm 2 , 95% CI: -68 to -39 cells/mm 2 ). At the per sample level (see Table), BBD controls showed significantly higher levels of both CD4+ (p=0.009) and CD8+ cells (p=0.0001) compared to KTB samples. In contrast, the BBD cases only showed elevated CD8 (p=0.007) and not CD4 (p=0.21) cell infiltrates compared to KTB samples. Comparing BBD cases to BBD controls, BBD cases showed significantly lower CD8 cell density as compared to BBD controls (p=0.002) and cases had lower CD4 cell density but the difference was not significant (p=0.07). Despite these differences in the cell densities, the ratio of CD4:CD8+ cells did not differ significantly across groups (p=0.83). The CD4:CD8+ ratio also did not differ significantly by histologic impression (p=0.74), degree of involution (p=0.27), or age (p=0.32). Conclusion: Our findings suggest that BBD is associated with increased infiltration of T cells into the breast tissue. Furthermore, these immune responses appear more robust in BBD patients at lower risk of developing breast cancer. Citation Format: Pena Jimenez A, Hoskin TL, Arshad MA, Visscher DW, Brahmbhatt RD, Miller EE, Stallings Mann ML, Carter JM, Murphy LM, Winham SJ, Radisky DC, Denison LA, Knutson KA, Degnim AC. CD4 and CD8 T cell densities are increased in benign breast disease compared to normal breast tissue. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-04-09.