B cells in cancer: functions, mechanisms and therapeutic advances.

Across various cancer entities, a wide array of subtypes of B cells that infiltrate tumors can be identified. These subtypes confer these cells with high adaptability in their functions and significant involvement in tumor progression. Tumor-infiltrating B cells act as distinctive microenvironmental mediators that build tertiary lymphoid structures, secrete diverse factors, and generate a wide antibody repertoire, thereby offering a valuable indicator of immunotherapy response. Recent clinical trials have demonstrated that intervening in tumor-infiltrating B cells can be an effective treatment strategy for tumors, including common types such as breast cancer, colorectal carcinoma, and non-small cell lung cancer. These findings suggest that tumor-infiltrating B cells should not be overlooked as therapeutic targets, as they offer significant potential to reduce the incidence of nonresponse, drug resistance, and immune-related adverse effects commonly seen in current treatment techniques. In this review, we explore the historical development of B cells in the context of tumors. We then discuss the various subtypes of tumor-infiltrating B cells, analyzing their diverse roles in tumor development. Additionally, we delve into the signaling pathways of tumor-infiltrating B cells, intercellular crosstalk, and multilevel regulatory mechanisms. Finally, based on immune checkpoints and therapeutic targets on the surface of tumor-infiltrating B cells, we summarize the current understanding which can lead to the development of new intervention methods targeting tumor-infiltrating B cells in the future. This review aims to provide a comprehensive summary of B-cell classification and therapeutic potential, emphasizing their critical role in guiding clinical treatment strategies.