E2F6 and teratocarcinoma: They reported that human stem cells and teratocarcinoma cells show a selective reduction in the expression of E2F1, E2F2, E2F3 and p105 (encoded by NFKB1) and enhanced expression of E2F4, E2F5, E2F6 and p130 (encoded by RBL2) compared with human normal somatic IMR90 cells [57].