Double-edge Role of B Cells in Tumor Immunity: Potential Molecular Mechanism

B cells are a heterogeneous population, which have distinct functions of antigen presentation, activating T cells, and secreting antibodies, cytokines as well as protease. It is supposed that the balance among these B cells subpopulation (resting B cells, activated B cells, Bregs, and other differentiated B cells) will determine the ultimate role of B cells in tumor immunity. There has been increasing evidence supporting opposite roles of B cells in tumor immunity, though there are no general acceptable phenotypes for them. Recent years, a new designated subset of B cells identified as Bregs has emerged from immunosuppressive and/or regulatory functions in tumor immune responses. Therefore, transferring activated B cells would be possible to become a promising strategy against tumor via conquering the immunosuppressive status of B cells in future. Understanding the potential mechanism of double-edge role of B cells will help researchers utilize activated B cells to improve their anti-tumor response. Moreover, the molecular pathways related to B cell differentiation are involved in its tumor-promoting effect, such as NF-κB, STAT3, BTK. So, we review the molecular and signaling pathway mechanisms of B cells involved in both tumor-promoting and tumor-suppressive immunity, in order to help researchers optimize B cells to fight cancer better.