Immune landscape characterization of neurofibromas with atypical features in Neurofibromatosis1 reveals PD-1 and the Tim-3/Galectin-9 pathway as potential therapeutic targets.

mouse model-derived tumors. Using multiplex immunofluorescence, we showed that CD3+ T-cells express the inhibitory IC PD-1, while CD163+ macrophages express both Tim-3 and Gal9. Furthermore, tumor cells within ANF/ANNUBPs were positive for activated caspase-3, suggesting a possible role of the immune microenvironment in controlling tumor growth or inducing cell death. Through deep-targeted DNA sequencing, we detected loss of cell cycle regulators (especially CDKN2A) in ANF/ANNUBPs but no somatic alteration of polycomb repressor complex components EED and SUZ12, the latter typically associated with MPNSTs, even at low frequencies. Additionally, loss of H3K27me3 was associated with even lower densities of CD3+ T-cells and CD163+ macrophages in MPNSTs, and the loss of p16 seemed to act synergistically. Taken together, these findings suggest that an immune response involving both T-lymphocytes and macrophages may play a role in controlling or delaying the malignant transformation of ANF/ANNUBPs into MPNSTs and point to IC molecules as novel immunopreventive strategies in NF1 patients with ANF/ANNUBPs.