EIF4B and neoplasm: All manipulations of eIFs and PDCD4 intended to decrease helicase activity caused diminished proliferation and entry of cells in S phase, consistent with previous findings regarding the individual inhibition of eIF4A1 and eIF4B in leukemia19 and HeLa cells.13 In addition, our finding that we could replicate the inhibitory effect on cell growth by overexpressing PDCD4 was consistent with the known inhibitory effect of PDCD4 on eIF4A1 function, and supports a role for PDCD4 expression in restricting tumor growth.