WNK3 inhibition elicits antitumor immunity by suppressing PD-L1 expression on tumor cells and activating T-cell function

Immune checkpoint therapies, such as programmed cell death ligand 1 (PD-L1) blockade, have shown remarkable clinical benefit in many cancers by restoring the function of exhausted T cells. Hence, the identification of novel PD-L1 regulators and the development of their inhibition strategies have significant therapeutic advantages. Here, we conducted pooled shRNA screening to identify regulators of membrane PD-L1 levels in lung cancer cells targeting druggable genes and cancer drivers. We identified WNK lysine deficient protein kinase 3 (WNK3) as a novel positive regulator of PD-L1 expression. The kinase-dead WNK3 mutant failed to elevate PD-L1 levels, indicating the involvement of its kinase domain in this function. WNK3 perturbation increased cancer cell death in cancer cell–immune cell coculture conditions and boosted the secretion of cytokines and cytolytic enzymes, promoting antitumor activities in CD4 + and CD8 + T cells. WNK463, a pan-WNK inhibitor, enhanced CD8 + T-cell-mediated antitumor activity and suppressed tumor growth as a monotherapy as well as in combination with a low-dose anti-PD-1 antibody in the MC38 syngeneic mouse model. Furthermore, we demonstrated that the c-JUN N-terminal kinase (JNK)/c-JUN pathway underlies WNK3-mediated transcriptional regulation of PD-L1. Our findings highlight that WNK3 inhibition might serve as a potential therapeutic strategy for cancer immunotherapy through its concurrent impact on cancer cells and immune cells. Cancer treatment: A new approach to boosting anti-tumor immunity Inhibiting the activity of the protein WNK lysine deficient protein kinase 3 (WNK3) boosts anti-tumor immunity by suppressing the production of another protein (PD-L1) whose activity promotes the programmed cell death of immune system T cells. Hyun Seok Kim, Ho-Keun Kwon and colleagues at Yonsei University in Seoul, South Korea, undertook a wide search for factors that could regulate PD-L1 levels in human lung cancer cells. While identifying WNK3 inhibition as a route towards restoring the anti-cancer activity of T cells, the research also revealed details of the molecular signaling pathways that allow WNK3 to affect PD-L1 production. Tests in mice confirmed that WNK3 inhibition can suppress tumor growth. Drugs that inhibit WNK3 can now be investigated as a new approach to treating cancer, due to their effects on both immune system cells and cancer cells.