The relationship of immune control checkpoint molecules in meningioma with clinicopathological parameters and microsatellit instability

Meningiomas are benign neoplasms originating from meningothelial cells in the brain and spinal cord, which usually show slow growth. It is the most common primary brain tumor in the central nervous system and accounts for 39.7% of all brain tumors. With current therapeutic approaches, the overall 10-year survival rates of grade 1, 2 and 3 tumors are 84%, 53% and 0%, respectively. Surgical resection is the primary treatment approach in symptomatic meningiomas. However, there are no effective systemic treatments that can be recommended in cases with a progressive course that do not respond to surgical or radiation therapy. Cancer immunotherapy aims to strengthen the immune system that fights cancer. Thanks to its specificity, long-lasting effects and contributions to recovery, it continues to consolidate its place in cancer treatment. Since meningiomas also express immune checkpoint molecules, they are seen as potential candidates for targeted therapy. Therefore, we aimed to investigate the relationship between the expression of PD-1 and PD-L1 molecules in the immune checkpoint in tumor and immune cells, clinicopathological data and microsatellite instability in meningiomas. Our study included 200 cases of meningioma (grade 1 and grade 2) diagnosed in our department between 2007- 2021. New blocks were obtained by tissue microarray method from selected suitable blocks. New sections were stained with PD-1, PD-L1, MLH1, MSH2, MSH6 and PMS2 immunohistochemistry antibodies. The data were evaluated with the help of statistical analyses. The incidence rate of PD-L1 expression in tumor cells is 29%. A significant increase in the rate of membranous PD-L1 expression was found as a result of an increase in histopathological grade, the presence of spontaneous necrosis, brain invasion, an increase in the size and number of mitoses. The rate of PD-L1 staining in tumor infiltrating lymphocytes is 19.5%. An increase in the degree of tumor and the presence of spontaneous necrosis increases the incidence of PD-L1 positive immune cells. The survival rate decreases in cases with PD-L1 positive immune cells. The rate of PD-1 staining in tumor infiltrating lymphocytes is 12%. In cases with brain invasion, both the incidence rate of PD-1 positive immune cells and the increase in the number of cells are statistically significant. In cases with a high risk of microsatellite instability, there was no significant difference when comparing the PD-L1 and PD-1 relationship. PD-L1 and PD-1 expression are associated with tumor aggressiveness in meningiomas and have been interpreted as a poor prognostic factor. It is thought that immunotherapy may be a promising treatment method thanks to the routine investigation of the status of immunocheckpoint molecules in meningiomas and the increase in clinical experience.