In addition, Yearley et al. used a unique immunohistochemistry assay to investigate the expression of PD-L2 in tumor tissues and the correlation between clinical response and PD-L2 status in tumor tissues from patients with relapsed/metastatic (R/M) HNSCC treated with pembrolizumab. Here, PDCD1LG2 is linked to head and neck squamous cell carcinoma.