EGF and neoplasm: The sequence upstream S76 R69DSGRGDS76 (RXXXRXXS) is different from the canonical consensus sequence RXRXXS of S6K1 substrate, but there is homology between the sequences around the three phosphorylation sites S67, S76 and S457 by S6K1 in PDCD4 protein, as shown in Figure 6B. Thus, the induction mechanism of PDCD4 degradation explains, at least partly, the mechanism of EGF or TPA function as a tumor promotor.