PDCD1 and cancer: PD‐L1 expression is a widely used biomarker to predict the response to PD‐1 or PD‐L1 inhibitors.[11, 12] PD‐L1 can be induced by inflammatory cytokines produced in the tumor microenvironment, such as interferon‐gamma (IFN‐γ) and tumor necrosis factor‐alpha (TNF‐α).[2, 13, 14] Oncogenic pathways,[15, 16] genetic alteration,[17, 18, 19] epigenetic modification,[20, 21] as well as post‐translation modification[22, 23] are also regulatory mechanisms of PD‐L1 expression in cancer.