Plexin-B1: a potential diagnostic biomarker for glioma and a future target for glioma immunotherapy

Gliomas are the most common tumors in the central nervous system. Plexin-B1 is abundantly expressed in the nervous system as an axonal guidance molecule during neuronal development. However, the correlation between its expression and the clinical characteristics of gliomas, and its therapeutic significance, remain largely unexplored. In this study, we detected the expression of Plexin-B1 in clinical glioma tissue samples. Plexin-B1 was highly expressed in the cytoplasm and on the membrane of glioma tissues, while only trace levels of Plexin-B1 were present in normal brain tissue. The expression level of Plexin-B1 in glioma tissue was associated with the pathological grade of the glioma. In addition, we used flow cytometry to analyze the expression of Plexin-B1 in glioma cell lines and its ligand, semaphorin 4D (Sema4D), in natural killer (NK) cell lines. Cytotoxicity assays showed cytolysis of the U251 glioma cell line by the NK cell line, NK92, and this was markedly downregulated when the neutralizing antibody to Plexin-B1 was added. This study demonstrates that Plexin-B1 could be used as a diagnostic biomarker, and also suggests that it may be involved in the cytotoxicity of NK cells to glioma cells. Plexin-B1 could be a useful future target for glioma immunotherapy.