CD4 and neoplasm: To determine whether cancer cells are capable of directly inducing FOXP3 expression in naïve T cells, we purified CD45RA+ CD4 T cells from human peripheral blood and stimulated them for 5 days with anti-CD3/28 antibody-coated beads, in the presence or absence of culture supernatants from five cancer cell lines representing tumours of the colon, lung, liver and brain.