Single-Nucleus RNA-Sequencing Reveals a MET+ Oligodendrocyte Subpopulation That Promotes Proliferation of Radiation-Induced Gliomas

Abstract

PurposeRadiation-induced gliomas (RIGs) are fatal late complications of radiotherapy, with a median survival time of 6–11 months. RIGs demonstrate unique molecular landscape and may originate from a glial lineage distinct from that of primary malignancies or diffuse midline gliomas (DMGs). This study aimed to explore the intratumoral diversity within RIGs to uncover their cellular origin and characteristics, and enhance our understanding of this uncommon tumor type. Methods and MaterialsFormalin-fixed, paraffin-embedded samples were collected from two RIGs and two DMGs for single-nucleus RNA sequencing. A detailed analysis was conducted to assess intratumoral heterogeneity and cellular interactions, including gene set enrichment, pseudotime trajectory, and cell communication analyses. Immunofluorescence staining, proliferation assay, and RNA-seq analysis were also applied to validate our findings. ResultsOur analysis revealed distinct heterogeneity in oligodendrocytes between the DMG and RIG samples. A unique subpopulation of oligodendrocytes in RIGs, which was characterized by gene encoding mesenchymal-epithelial transition factor (c-MET) and therefore termed MET+ ODs, exhibited characteristics typical of cancer cells, such as increased mitotic activity, cancer-related gene expression, and extensive copy number variations. Cell communication studies indicated that MET+ ODs interact vigorously with G1/S and G2/M cycling cells via the neural cell adhesion molecule (NCAM) signaling pathway, potentially enhancing the proliferation of cycling malignant cells. Integrating our results with existing RNA-seq data further supported our hypothesis. The presence of MET+ ODs in RIGs was confirmed by immunostaining, and activation of the NCAM signaling pathway in vitro significantly promoted the proliferation of RIG tumor cells. Moreover, in-vitro radiation induced the transformation of oligodendrocytes to be more similar to MET+ ODs. ConclusionsRIGs are characterized by an oligodendrocyte composition distinct from that of DMGs. A specific subpopulation of MET+ ODs in RIGs may be crucial in tumorigenesis and promote the growth of malignant cells. Identifying MET+ ODs offers a valuable target for future clinical surveillance and therapeutic strategies.