Abstract 4646: Relative contribution of tumor infiltrating B cells to the tumor microenvironment assessed using an immuno-oncology focussed multi-tumor tissue microarray
Authors: Bhagat Milan , Memeo Leorenzo , Womack Christopher , Kim Woo Hoo , Cumberbatch Marie 
Published: April 2023

Abstract
Although cancer immunotherapy approaches have focused primarily on driving T cell mediated immunity, attention has turned to other immune cell types within the tumor microenvironment (TME) to improve efficacy. Growing evidence supports a role for tumor-infiltrating B cells in complementing T cell-mediated immunity and contributing to the immunomodulation of cancer. Analyses of RNA sequencing data from The Cancer Genome Atlas (TCGA) have correlated high expression of B cell genes with improved patient survival in a range of cancer types. However, it is likely that effective anti-tumor immunity involves interactions between both B and T cells. To investigate the relative contribution of B cells to the overall TME across multiple tumor types simultaneously, we have examined a multi-tumor tissue microarray (TMA) comprising 29 different cancer types represented by approximately 12 unique donors per indication and duplicate 1mm cores per donor (1 from invasive margin [IM] and 1 from tumor center [TC]). Serial sections were stained by single-plex immunohistochemistry for CD20, CD3, CD4 and CD8, and immune cells enumerated by digital image analysis (CellProfilerTM). Analysis of overall immune infiltration regardless of core location (IM and TC combined) revealed tumor indications such as NSCLC, gastric, TNBC, cutaneous SCC and cervical to be most highly infiltrated, and GIST, GBM and prostate to exhibit the fewest tumor-infiltrating immune cells. B cell frequencies correlated with T cell densities for most tumor types with some notable exceptions including, for example, ER+ BC and gallbladder cancer where the proportion of B cells was higher relative to T cells, and TNBC where the converse pattern was evident. Spatial analyses revealed increased B cell frequencies in IM compared with TC, correlating with the distribution of T cells in the TME for the majority of tumor indications. However, a contrasting expression pattern was observed for ER+ BC, NSCLC SCC and cutaneous SCC where B cell frequencies were greater in TC. Clear evidence for presence of B cells in tertiary lymphoid structures (TLS) was observed for some tumor donor cores (e.g. gastric cancer). Taken together, we describe the relative distribution of B cells in the TME across multiple tumor types simultaneously. This approach demonstrates the benefits of utilizing an immuno-oncology focussed multi-tumor TMA to interrogate B cell biology and to dissect how heterogeneity of this cell population may contribute to anti-tumor immunity.
Citation Format: Milan Bhagat, Leorenzo Memeo, Christopher Womack, Woo Hoo Kim, Marie Cumberbatch. Relative contribution of tumor infiltrating B cells to the tumor microenvironment assessed using an immuno-oncology focussed multi-tumor tissue microarray. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4646.