Immunohistochemical analysis of the immune checkpoint molecule Galectin-9 in meningiomas

Purpose: Most meningiomas can be treated by surgical resection. However, depending on the location of the lesion, incomplete resection or high-grade meningiomas may have a poor prognosis. The new methods such as immunotherapy may improve our options for effective, patient-specific treatment of meningiomas. We aim to contribute to the development of new personalized treatment strategies by investigating the status of Gal-9 in meningiomas. Materials and Methods: Four hundred two cases diagnosed in our laboratory between 2007 and 2020 were used for the study. New blocks of multiple tissues were prepared for immunohistochemistry using the tissue microarray method. Immunohistochemical staining of Gal-9 antibody was evaluated using the H-score method. Results: Of the 402 cases studied, 289 were female and 113 were male. Two hundred and seventy-one (67.4%) cases were WHO grade 1; 121 (30.1%) were grade 2 and 10 (2.5%) were grade 3. A high H-score was observed in grade 1 and 2 tumors (H-score: 93.38 and 93.91) and a low H-score in grade 3 tumors (H-score: 59.40). There was no significant correlation between brain invasion and Gal-9 expression. No significant correlation was found between Gal-9 expression and minor criteria used in tumor grading. Conclusion: A statistically significant difference was found between Gal-9 H-score and tumor grade. Gal-9 had a lower H-score in high-grade meningiomas and its expression level decreased. Therefore, Gal-9 with different expression levels can be used as a prognostic and predictive biomarker as well as an important molecule for treatment.