PDCD1LG2 and head and neck squamous cell carcinoma: Yearley et al.33 reported that PD-L2 status was a significant predictor of progression-free survival with pembrolizumab independent of PD-L1 status, and the objective response rate was the highest in patients expressing both PD-L1 and PD-L2 in head and neck squamous cell carcinoma cases.