PDCD1 and melanoma: On the other hand, we observed higher UBQLN4 and PD-L1 levels in the tumor region of melanoma patients who responded to anti-PD-1 therapy than in the tumor region of nonresponders, indicating that UBQLN4 and PD-L1 might be potential biomarkers for assessing and predicting the efficacy of anti-PD-1 therapy in the clinic.