The present invention relates to chimeric molecules comprising portions of rat PEG-3 ("rPEG-3") and human GADD34 ("hGADD34") having apoptotic activity. It is based, at least in part, on the discovery that a chimeric protein comprising amino acids 1-347 of rat PEG-3 fused with residues 418-674 of human GADD34 exhibited anti-proliferative activity when expressed in transformed cells. The present invention provides for this and other rPEG3/hGADD34 chimeras, and the use of such proteins in inhibiting cell proliferation, angiogenesis, and tumor growth.