Wentao Zhan

The role of glioma-associated myeloid cells in tumor growth and immune evasion remains poorly understood. We performed single-cell RNA sequencing of immune and tumor cells from 33 gliomas, identifying two distinct myeloid-derived suppressor cell (MDSC) populations in isocitrate dehydrogenase–wild-type (IDT-WT) glioblastoma: an early progenitor MDSC (E-MDSC) population with up-regulation of metabolic and hypoxia pathways and a monocytic MDSC (M-MDSC) population. Spatial transcriptomics demonstrated that E-MDSCs geographically colocalize with metabolic stem-like tumor cells in the pseudopalisading region. Ligand-receptor analysis revealed cross-talk between these cells, where glioma stem-like cells produce chemokines attracting E-MDSCs, which in turn produce growth factors for the tumor cells. This interaction is absent in IDH-mutant gliomas, associated with hypermethylation and repressed gene expression of MDSC-attracting chemokines. Our study elucidates specific MDSCs that may facilitate glioblastoma progression and mediate tumor immunosuppression.

Regulatory T cells (T_reg) are conventionally viewed as suppressors of endogenous and therapy-induced antitumor immunity; however, their role in modulating responses to immune checkpoint blockade (ICB) is unclear. In this study, we integrated single-cell RNA-seq/T cell receptor sequencing (TCRseq) of >73,000 tumor-infiltrating T_reg(TIL-T_reg) from anti–PD-1–treated and treatment-naive non–small cell lung cancers (NSCLC) with single-cell analysis of tumor-associated antigen (TAA)–specific T_regderived from a murine tumor model. We identified 10 subsets of human TIL-T_reg, most of which have high concordance with murine TIL-T_regsubsets. Only one subset selectively expresses high levels ofTNFRSF4(OX40) andTNFRSF18(GITR), whose engangement by cognate ligand mediated proliferative programs and NF-κB activation, as well as multiple genes involved in T_regsuppression, includingLAG3. Functionally, the OX40^hiGITR^hisubset is the most highly suppressive ex vivo, and its higher representation among total TIL-T_regcorrelated with resistance to PD-1 blockade. Unexpectedly, in the murine tumor model, we found that virtually all TIL-T_reg–expressing T cell receptors that are specific for TAA fully develop a distinct T_H1-like signature over a 2-week period after entry into the tumor, down-regulatingFoxP3and up-regulating expression ofTBX21 (Tbet), IFNG, and certain proinflammatory granzymes. Transfer learning of a gene score from the murine TAA-specific T_H1-like T_regsubset to the human single-cell dataset revealed a highly analogous subcluster that was enriched in anti–PD-1–responding tumors. These findings demonstrate that TIL-T_regpartition into multiple distinct transcriptionally defined subsets with potentially opposing effects on ICB-induced antitumor immunity and suggest that TAA-specific TIL-T_regmay positively contribute to antitumor responses.