PD-L1 expression in meningiomas.

The management of meningiomas, especially inoperable, previously irradiated recurrent and anaplastic meningiomas has been challenging due to the paucity of effective chemotherapy. Numerous studies suggest that tumor-mediated immunosuppression may facilitate progression of many malignancies. Recent identification of PD-L1 expression in some types of cancer cells has raised the possibility that its inhibition of host immunosurveillance may be part of the mechanism. Thus, tumor cell PD-L1 might be a useful new target for chemotherapy in PD-L1- bearing tumors. Several a monoclonal antibodies against PD-L1 are now in use in the management of treatment refractory or metastatic non-small cell carcinoma of the lung, metastatic renal cell carcinoma, melanoma and other malignancies. The extent of PD-L1 expression is not established in meningiomas. Depending on the degree of expression, anti-PD-L1, might be an effective treatment for meningiomas. In this study, we used a monoclonal antibody, approved by the FDA for clinical screening to evaluate PD-L1 expression in a series of 58 meningiomas including 13 with bone, brain or dural invasion. PD-L1 immunoreactivity was detected in 1 of 31 grade I, 1 of 16 grade II and 2 of 11 WHO grade III meningiomas. PD-L1 was seen in 1 grade II tumor invading brain and 1 grade III tumor invading bone but was not at sites of invasion. In each case, immunoreactivity was scored as limited. The findings suggest anti-PD-L1 therapy might be worth evaluating in a select number of positive tumors but its overall applicability may be limited.