Furthermore, recent studies using mouse models of colon cancer have shown that IL-22 produced by CD4+ T cells acts upon cancer cells to activate STAT3 and promote the expression of the histone 3 lysine 79 (H3K79) methyltransferase DOT1L, which induces key cancer stem cell genes that contribute to tumor progression (34, 52, 53). Here, CD4 is linked to cancer.