Abstract 1287: Characterization of B cells infiltrating human breast cancer

Abstract

Abstract Recent advances in tumor immunology have shown that an important link exists between tumor infiltrating lymphocytes (TIL) and patient outcome. In human breast cancer (BC), more extensive lymphocyte infiltration is associated with a better prognosis and also predicts responses to pre-operative chemotherapy. TIL are principally composed of T cells; however, approximately 20% of BC patients have a significant B cell infiltration, which can be diffuse and/or aggregated in stroma-located tertiary lymphoid structures (TLS). B cell infiltration in human BC has been associated with better survival and a longer disease-free interval, although the pro-/anti-tumor activities of B cells remain under debate. We undertook this study to more fully characterize the B cell infiltrate in human BC and the role humoral immunity potentially plays in generating effective anti-tumor immune responses. Flow cytometric analysis of fresh breast tissue homogenates detected an increased density of infiltrating B cells in all untreated primary BC (n = 223) compared with normal (mammary reductions; n = 53) and non-tumor non-adjacent (NANT; n = 198) breast tissues. This increase is not observed in BC tissue from metastatic and recurrent BC nor neoadjuvant-treated primary tumors. Potential correlations between infiltrating B cell density and clinicopathological parameters were examined, revealing that B cell density was associated with Ki67, ER and PgR status but not with age, tumor size, nodal status, grade, vascular invasion, HER-2 status, stage, histotype, subtype or in situ lesions. B cell infiltration was also correlated with the number of infiltrating CD4+ and CD8+ T cells and CD14+ monocytes. All stages of B cell differentiation were detected in the infiltrate; however, memory B cells significantly increased in BC compared to normal breast tissues. An increase in centroblasts and centrocytes, the germinal center B cells, was associated with a TFH cell presence (our data previously demonstrating that TFH cells predict good clinical outcomes). Furthermore, the presence of centroblasts-centrocytes and TFH cells was positively correlated with antibody-secreting cells, suggesting local humoral immune responses are generated in TLS. This hypothesis is supported by the increased immunoglobulin secretion detected in primary supernatants from tumors compared with normal breast tissues. Embedded BC tissues, examined by confocal microscopy, confirm that infiltrating B cells are principally located in TLS, which are composed of marginal, follicular mantle and germinal center zones surrounded by T cells. These data show that B cell infiltration is correlated with the overall extent of TIL and their presence likely functions to generate a humoral immune response adjacent to the tumor bed. B cells in extensively infiltrated tumors potentially play other important functional roles in generating effective anti-tumor immune responses, an aspect currently under investigation. Citation Format: Soizic Garaud, Laurence Buisseret, Céline Naveaux, Anaïs Boisson, Jean-Nicolas Lodewyckx, Hugues Duvillier, Ligia Craciun, Denis Larsimont, Karen Willard-Gallo. Characterization of B cells infiltrating human breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1287. doi:10.1158/1538-7445.AM2015-1287