PD-1 and PD-L1 are more highly expressed in high-grade bladder cancer than in low-grade cases: PD-L1 might function as a mediator of stage progression in bladder cancer.

Background: Bladder cancers have been characterized as a tumor group in which the immunological response is relatively well preserved. Programmed death ligand 1 (PD-L1, B7-H1, CD274) has been shown to be expressed in several malignancies, including bladder cancer. However, the clinicopathological impact of this biomarker has not yet been established. In the present study, a quantitative real-time polymerase chain reaction (qPCR) was performed using paired normal and cancerous bladder cancer tissue to investigate PD-1/PD-L1 gene expression.

Methods: We examined the mRNA expression of PD-1/PD-L1 by a qPCR using 58 pairs of normal and cancerous human bladder tissue specimens. We also examined the correlation with the expressions of the STAT1 and NFAT genes, which are thought to be upstream and downstream of the PD-L1 pathway, respectively.

Results: There were no significant differences between normal and cancerous tissue in the expression of the PD-1 and PD-L1 genes (p = 0.724 and p = 0.102, respectively). However, PD-1 and PD-L1 were both more highly expressed in high-grade bladder cancer than in low-grade bladder cancer (p < 0.050 and p < 0.010). PD-L1 was positively correlated with the expressions of both the STAT1 (r = 0.681, p < 0.001) and the NFATc1 genes (r = 0.444. p < 0.001).

Conclusions: PD-1 and PD-L1 might be a new biomarker that correlates with the pathological grade of bladder cancer. PD-L1 might function as a mediator of stage progression in bladder cancer and STAT1-NFAT pathway might associate this function.