PDCD1 and bladder transitional cell carcinoma: However, with more immune checkpoints identified, independent PD-1/PD-L1 expression is now considered as an unstable biomarker as there is significant heterogeneity between PD-1/PD-L1 expression and the clinical outcome in BLCA patients (Bellmunt et al., 2014; Massard et al., 2016; Rosenberg et al., 2016; Sharma et al., 2017b).