Prognostic importance of PD-L1 expression in bladder cancer patients

Abstract

Background: PD-L1/PD-1 molecules are known as important mediators in immune-escape mechanisms of tumors. PD-L1 is highly expressed in various malignancies, including bladder cancer. However, the prognostic value of PD-L1 in bladder cancer patients remains controversial.

Aim: To investigate the prognostic significance of PD-L1 expression in tumor tissues of bladder cancer patients.

Subjects and Methods: RNA was isolated from FFPE tumor tissues of 48 bladder cancer patients using the monophasic phenol and guanidine isothiocyanate method. Total RNA was converted to cDNA and gene expression levels were analyzed by qRT-PCR. The differential expression levels of the PD-L1 gene between tumor grade and cancer stage groups were analyzed by independent student’s t-test and one-way ANOVA.

Results: Statistically significantly increased PD-L1 expression was observed in the high-grade tumor group (p < 0.05). No significant difference in PD-L1 expression was found among pTa, pT1, and pT2 groups. In addition, the difference in overall survival was not significantly different between groups.

Conclusion: The results showed that high PD-L1 expression in bladder cancer was associated with tumor aggressiveness and grade. Despite the inability of the qRT-PCR to show the PD-L1 expression at different locations of tumor tissue, evaluation of PD-L1 mRNA expression by qRT-PCR, which is a highly sensitive and specific assay, appears to be a robust approach. Furthermore, these findings may contribute to a rationale for recommending anti-PD-L1 immunotherapy as an alternative to standard therapy for bladder cancer patients who are most likely to benefit from it.