TNFRSF9 and neoplasm: Guo et al. [33] found two subsets of Tregs in the lung tumor microenvironment, distinguished by high or low expression of tumor necrosis factor receptor superfamily member 9 (TNFRSF9, encoding 4-1BB); they showed that the activated tumor Treg subset (expressing high levels of immune checkpoints) was associated with poor prognosis in NSCLC, which was further supported by a recent independent study of bladder tumors [37].