Cancer-Associated B Cells in Sarcoma

SIMPLE SUMMARY: B cells are increasingly appreciated as important contributors to the tumor microenvironment in a myriad of cancer histologies, including sarcoma. In sarcoma, recent investigations have revealed associations between B cell expression signatures, the presence of tertiary lymphoid structures, and responses to immunotherapy. In this paper, we aim to provide a comprehensive review of the multiple putative roles of B cells in sarcoma, including a historical overview, an assessment of B cells within the sarcoma microenvironment, the role of tertiary lymphoid structures, the relationship between immunotherapy efficacy and B cell signatures, sarcoma antigens and anti-tumor antibodies, pro-tumor B cell relationships, and future research directions. ABSTRACT: Despite being one of the first types of cancers studied that hinted at a major role of the immune system in pro- and anti-tumor biology, little is known about the immune microenvironment in sarcoma. Few types of sarcoma have shown major responses to immunotherapy, and its rarity and heterogeneity makes it challenging to study. With limited systemic treatment options, further understanding of the underlying mechanisms in sarcoma immunity may prove crucial in advancing sarcoma care. While great strides have been made in the field of immunotherapy over the last few decades, most of these efforts have focused on harnessing the T cell response, with little attention on the role B cells may play in the tumor microenvironment. A growing body of evidence suggests that B cells have both pro- and anti-tumoral effects in a large variety of cancers, and in the age of bioinformatics and multi-omic analysis, the complexity of the humoral response is just being appreciated. This review explores what is currently known about the role of B cells in sarcoma, including understanding the various B cell populations associated with sarcoma, the organization of intra-tumoral B cells in tertiary lymphoid structures, recent trials in immunotherapy in sarcoma, intra-tumoral immunoglobulin, the pro-tumor effects of B cells, and exciting future areas for research.