In particular, it is a powerful regulator of T cell activity and is capable of: inducing Foxp3 expression in peripheral CD4+ T cells, and polarising them towards a more suppressive T regulatory cell (Treg) phenotype [27, 28]; increasing Treg infiltration into the tumor [18]; polarizing CD4+ T cells towards different T helper subsets; and promoting CD4 effector responses [29, 30]. This evidence concerns the gene CD4 and neoplasm.