The objective was to identify pathways and/or ligand-receptor pairs that are differentially expressed between the inner and outer Glioblastoma margin areas. This might suggest a system for further exploration, as it may be involved in the “early” transformation of normal brain tissue to tumorigenic tissue and/or tumor recurrence.

I analyzed single-cell RNA sequencing from 3 paired GBM human samples. Each sample consisted of an inner-tumor-margin biopsy, which fluoresced intra-operatively with 5-aminolevulinic acid (5ALA+), and an outer-margin-biopsy, which did not fluoresce (5ALA-). Glioma and microglia within the samples were identified using canonical lineage markers and analyzed. I conducted differential gene expression (DGE) analysis and used CellChat to examine microglia-to-glioma communication probabilities.

The probability of microglia-to-glioma communication, specifically SPP1 secreted by microglia binding to the CD44 receptor and integrin beta-1 (ITGB1) receptor on glioma, was higher in 5ALA+ tissue. SPP1 showed a higher microglial expression in the 5ALA+ tissue (p<0.001), and CD44 and ITGB1 showed a higher expression in 5ALA- tissue among glioma (p<0.001).

The CellChat and DGE results suggest that microglia may upregulate their secretion of osteopontin (SPP1) in 5ALA+ tissue. This likely contributes to tumor proliferation and glioma invasion into surrounding brain tissue. SPP1’s major signaling “role” may evolve spatially-temporally. Its prominence in microglia-to-tumor signaling in 5ALA+ tissue might suggest its implication in the “early” transformation of normal brain tissue to tumorigenic tissue. This makes it worthy of further exploration as a therapeutic target.