High-Dimensional Imaging of Vestibular Schwannoma Reveals Distinctive Immunological Networks Across Histomorphic Niches inNF2-related Schwannomatosis

Abstract

AbstractNF2-related Schwannomatosis (NF2SWN) is a rare tumour-predisposition syndrome characterised by the growth of multiple central and peripheral nervous system neoplasms. The drivers ofNF2SWN are pathogenic variants in the tumour suppressor geneNF2, encoding the protein Merlin, leading to development of bilateral vestibular schwannoma (VS) in >95% of patients. VS tumours are characterised by infiltration of myeloid cells and lymphocytes, highlighting the potential of immunotherapy for VS. However, the immunological landscape in VS and the spatial determinants within the tumour microenvironment that shape the trajectory of disease are presently unknown. In this study, to elucidate the complex immunological networks across VS, we performed imaging mass cytometry (IMC) on clinically annotated VS samples fromNF2SWN patients. We reveal the heterogeneity in neoplastic cell, myeloid cell and T cell populations that co-exist within VS, determining that the cellular composition of VS tumours is independent ofNF2-SWN genetic severity. We show that distinct myeloid cell and Schwann cell populations exist within varied spatial contextures across characteristic Antoni A and B histomorphic niches. Interestingly, we show that T-cell populations associate with tumour-associated macrophages (TAMs) in Antoni A regions, seemingly limiting their ability to interact with tumorigenic Schwann cells. This spatial landscape is altered in Antoni B regions, where T-cell populations appear to interact with PD-L1+ Schwann cells. We also demonstrate that prior bevacizumab treatment (VEGF-A antagonist) preferentially reduces alternatively-activated TAMs, whilst enhancing CD44 expression, in bevacizumab-treated tumours. Together, we describe niche-dependent modes of T-cell regulation inNF2SWN VS, indicating the potential for microenvironment-altering therapies for VS.TeaserImaging mass cytometry and spatial omic analyses illustrate spatially-distinct regions of T-cell regulation in vestibular schwannoma.