PD-L2 Expression in Human Tumors: Relevance to Anti-PD-1 Therapy in Cancer

PD-L2 expression was observed in all tumor types and present in stromal, tumor, and endothelial cells. The prevalence and distribution of PD-L2 correlated significantly with PD-L1 (P = 0.0012–<0.0001); however, PD-L2 was detected in the absence of PD-L1 in some tumor types. Both PD-L1 and PD-L2 positivity significantly predicted clinical response to pembrolizumab on combined tumor, stromal and immune cells, with PD-L2 predictive independent of PD-L1. Response was greater in patients positive for both PD-L1 and PD-L2 (27.5%) than those positive only for PD-L1 (11.4%). PD-L2 status was also a significant predictor of progression-free survival (PFS) with pembrolizumab independent of PD-L1 status. Longer median times for PFS and overall survival were observed for PD-L2–positive than PD-L2–negative patients.

Clinical response to pembrolizumab in patients with HNSCC may be related partly to blockade of PD-1/PD-L2 interactions. Therapy targeting both PD-1 ligands may provide clinical benefit in these patients. Clin Cancer Res; 23(12); 3158–67. ©2017 AACR.