P4HB and glioblastoma: • PD-L1 has been observed to be an overexpressed biomarkerin GBM tissue as compared to normal brain tissue. Impeding the T cell activation of CD-4 and CD-8 and enabling gliomasto escape immune-mediated attacks, PD-I expression plays an importantrole in diagnosis and clinical response in patients; however, it cannotbe completely categorized as positive or negative signaling, whichmakes it incompetent to be used alone as a helpful biomarker for GBM.213,220