CD274 and glioblastoma: Next, the PD-L1-ex was co-cultured with TS-GBM cells, and we found that PD-L1-ex upregulated PD-L1 protein levels in TS-GBM cells (Fig. 2c), but had little effects on PD-L1 mRNA levels (Fig. 2d), suggesting that GSCs-derived PD-L1-ex delivered PD-L1 protein into TS-GBM cells.