Using a discovery cohort of 83 NSCLC patients and a validation cohort of 49 NSCLC patients treated with anti-PD1 inhibitors, Koh et al. found that responders had a higher frequency of circulating Tregs (characterized by CD25+ FOXP3+ CD4+ T cells) than non-responders one week after treatment initiation. This evidence concerns the gene FOXP3 and non-small cell lung carcinoma.