A productive antitumor response requires the contribution of an effective antigen presentation by antigen-presenting cells (APCs) to CD4 T lymphocytes via MHC-II; following activation, CD4 T lymphocytes can activate a cytotoxic T response or can directly carry out a cytotoxic action toward tumor cells in case the latter expose MHC-II–cancer epitope complexes on the surface [22]. This evidence concerns the gene CD4 and cancer.