CD274 and glioblastoma: To gain insight into the effects of Delta24-RGD infection on PD-L1 expression in human GBM, patient-derived GBM cultures (n = 12) were infected with the IC50 dosage of Delta24-RGD or were treated with IFNγ, a known inducer of tumor PD-L1 expression.15 PD-L1 expression was assessed with flow cytometry after 24 h when cell viability was not yet affected by the virus (>85% 7-AAD negative tumor cells; data not shown).