Abstract
Glioblastomas are embedded into an immunosuppressive microenvironment resulting in limited success of immunotherapies. Although, we and others observed defined myeloid-tumor crosslinks reducing T cell homing and activation, the spatial context of these interactions remained unexplored. Here, we provide evidence, that local T cell infiltration results in a defined activation of myeloid cells causing transcriptional reprogramming of tumor cells reminiscent of reactive transformation in mature astrocytes. Through integration of spatially resolved transcriptomics and imaging mass cytometry (n=18, 39 protein glioma panel) we mapped defined transcriptional responses in areas of high or low T cell infiltration respectively. Functional analysis revealed that areas of large T cell infiltration are enriched for glial (CHI3L1, GFAP and VIM) and inflammatory genes (HLA-DRA, C3, CCL4, CCL3). We found that marker genes of common reactive states in mature astrocytes significantly overlap with the reactive immune program of glioblastoma cells (f-score 0.76, p=2.2e-10). Increased numbers of CD163+ cells were found in surrounding areas of T cell infiltration and spatially linked to defined immunosuppressive release of IL10, recently reported as a major driver of T cell exhaustion. To support our findings, we injected a primary glioblastoma cell line into cortex slices of three different human and rodent donors. After 7 days of tumor growth, we performed scRNA-sequencing of FACS-sorted tumor cells and baseline cell culture cells. Compared to baseline, we found cells of all reported transcriptional states, confirming the dynamic adaptation of cells within a neural environment. In elderly donors, a significant accumulation of reactive immune programs (ANOVA p< 0.001) was observed. Immunostainings confirmed an increased myeloid cell activation in these donors. Our data suggest that inflammatory stimuli in the glioblastoma microenvironment cause transcriptional reprogramming in glioblastoma similar to inflammatory transformation of reactive astrocytes. The spatial exclusivity of these programs highlights the value of a spatial perspective on heterogeneity.
Salmonella Breaks Tumor Immune Tolerance by Downregulating Tumor Programmed Death-Ligand 1 Expression
