Koh et al. [165] demonstrated that in patients with advanced NSCLC undergoing anti-PD-1 therapy (pembrolizumab or nivolumab), elevated circulating levels of Treg cells (CD25+FOXP3+CD4+) one week after onset of therapy were strongly associated with an improved PFS and OS. The gene discussed is CD4; the disease is non-small cell lung carcinoma.