T-cell co-stimulation is a hierarchical process that is crucial for the formation of an effective immune response, while Tregs are a subpopulation of CD4+ T cells that play a critical role in tumor immune escape and angiogenesis (Facciabene et al., 2012; Tanaka and Sakaguchi, 2017; Chao and Savage, 2018). The gene discussed is CD4; the disease is neoplasm.