Tumor and Stromal Sphingolipid Imbalance Are Associated with T Cell Tissue Residency in Glioblastoma

T cells within solid tumors often switch from a recirculating to a tissue-resident state, which may blunt antitumor activity, but the signal driving this switch in vivo remains unclear. We asked whether alterations in sphingosine-1-phosphate (S1P) signaling in tumor or the surrounding stromal cells are associated with T cell residency in glioblastoma (GBM).

We analyzed five single-cell RNA-sequencing cohorts: three human glioma datasets, an in-house mouse CT2A glioblastoma cohort, and a human melanoma tumor-infiltrating lymphocyte cohort. T cell egress and tissue-residency programs, together with stromal S1P production and degradation, were scored per cell using curated gene modules. Cell-state contrasts were quantified as Cohen's d, and sample-level coupling as Spearman ρ.

In human GBM, T cell residency programs were elevated in CD4+ helper and regulatory T cells in tumors compared with low-grade glioma controls. In mouse CT2A-derived GBM tumors, stromal S1P production correlated negatively with T cell residency across four independent stromal cell types. In human GBM microglia, S1P production was reduced compared with control microglia. The same CD8+ residency phenotype was replicated in CD3-sorted GBM tumor-infiltrating lymphocytes (TILs) and in melanoma TILs.

A loss of stromal S1P production accompanies T cell tissue residency in GBM. Thus, stromal S1P metabolism is a candidate axis for modulating T cell recirculation and TIL biology in GBM. These findings are transcriptomic associations from single-cell RNA sequencing that do not directly measure S1P metabolite levels or signaling activity and will require functional and lipidomic validation.