Treg cells in the tumor microenvironment can restrict the activation and development of CD4 helper T cells and CD8 cytotoxic T cells via a variety of mechanisms (Li and Rudensky, 2016; Newton et al., 2016), resulting in diminished tumor antigen-expressing responsiveness and immunological escape (Cuadrado et al., 2018; Campbell and Rudensky, 2020). The gene discussed is CD4; the disease is neoplasm.