The immune system is important to control tumor development and progression in humans.
However, tumor cells and cells of the tumor microenvironment can induce immune escape mechanisms
including activation of immune checkpoints such as PD-1/PD-L1. Based on this knowledge,
new immune therapies, including PD-1 and PD-L1 inhibition, have been developed and are already
recommended as a standard treatment in metastatic bladder and kidney cancer patients. In addition to
its role as a therapeutic target, PD-L1 seems to be a prognostic parameter although data are controversial.
Only little is known about signaling pathways inducing PD-L1 expression in tumor cells on one
hand and about its functional role for tumor cells itself. However, the understanding of the complex
biological function of PD-L1 will improve therapeutic options in urological malignancies. This review
is giving an overview of the current knowledge concerning the PD-1/PD-L1 axis in urological tumors
including bladder, kidney, prostate, testicular and penile cancer.
Keywords: Checkpoint inhibition, PD-L1, bladder cancer, prostate cancer, kidney cancer, testicular germ cell tumors, penile
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