Radiation-induced glioblastoma stem cell-mediated T cell exhaustion via EGR1-Gal3-LAG3 axis in glioblastoma.

Glioblastoma (GBM), a highly aggressive brain tumor, inevitably recurs due to therapy-resistant glioblastoma stem cells (GSCs). Lymphocyte activation gene 3 (LAG3), an inhibitory immune checkpoint, contributes to T cell exhaustion and facilitates tumor immune escape. Here, we investigate the evolution of GSC-T cell interaction and the functional status of GBM-infiltrating T cells following radiotherapy. Using single-cell RNA sequencing analysis, we identified that T cells from recurrent GBM patients exhibited more exhausted status than those in newly diagnosed GBM patients. We identified LAG3 as a key factor driving T cell exhaustion in recurrent GBM. Furthermore, radiation exposure induced the expression of galectin-3 (Gal3), a canonical ligand of LAG3. EGR1 transcriptionally upregulated Gal3 expression in irradiated GSCs, impairing cytotoxic activity of both CD4+ and CD8+ T-cell. The small molecule inhibitor targeting EGR1 in combination with anti-LAG3 blockade suppressed Irradiated GBM tumor growth and extended the survival of orthotopic xenograft-bearing mice. Gal3 secreted by GSCs plays critical roles in maintaining T cell exhaustion, highlighting a radio-induced interplay between GSCs and GBM-infiltrating T cells. Targeting upstream regulator EGR1 and LAG3 informs a promising treatment strategy for GBM.