PDCD1 and extranodal nasal NK/T cell lymphoma: Although a single-arm clinical trial reported that PD1 antibody has promising efficiency in NKTCL, there is no report of a randomized, head-to-head clinical trial or preclinical animal study to explore whether PD-1 antibody combined with a histone deacetylase inhibitor is superior to every single agent and shows synergistic.