EVALUATION OF IMMUNOINHIBITORY CHECKPOINTS IN ORAL OSTEOSARCOMAS

Objective Cancers have been categorized into 4 different tumor microenvironments (TME) based on the presence of PD-L1 expression and tumor-infiltrating lymphocytes (TIL). However, oral osteosarcoma (OO) has not yet been studied. This research evaluated the immunoexpression of PD-L1 and TIL CD8+ and PD-1+ in a series of cases of OO. Study Design It is a multicenter, observational and cross-sectional study. The sample was composed of 20 cases of primary OO diagnosed in various centers of reference in oncology. Immunohistochemistry was used to identify PD-L1+, TIL CD8+, and PD-1+ cells. Analysis of positivity was assessed by the percentage of PD-L1+ neoplastic cells (1 = absent [ 50%) and densities of TIL per mm2 (1 = absent [25 cells/mm2], 2 = low [25 a 130 cells/mm2], and 3 = high [130 cells/mm2]) adapted from Van Erp et al. (2017). Results From all cases studied, 75% showed overexpression of PD-L1 (score 3). On the other hand, all samples revealed absent or low TIL CD8+ (score 1 or 2) and absent TIL PD-1+ (score 1). Conclusions OO showed an immune profile characterized by high PD-L1/low CD8/absent PD-1, which may represent a TME type unresponsive to immunotherapy. Grant: CNPq 305897/2015-2.