Described herein are novel compositions comprising, for example, PDCL3 polypeptides having VEGFR-2 inhibitory activity, inhibitory PDCL3 antibodies and PDCL3-binding fragments thereof, or PDCL3 inhibitory nucleic acid molecules, and methods of their use in anti-angiogenesis and anti-tumor proliferation and invasiveness therapies, such as the treatment of cancer, as well as the treatment of those vascular diseases where pathological angiogenesis plays a role, such as in carotid artery disease, macular degeneration, and plaque neovascularization. Also described herein are novel compositions comprising engineered PDCL3 polypeptides having enhanced chaperone activity, recombinant cells comprising such engineered PDCL3 polypeptides having enhanced chaperone activity, and methods thereof for therapeutic protein production and in vitro protein synthesis.