Since collagen biosynthesis and more specifically, collagen prolyl hydroxylase competes with DNA and histone demethylases for ascorbate and α-KG, the inhibition of collagen biosynthesis could attenuate epigenetically cancer progression, while proline (saved in this process) could serve as an inhibitor of prolyl hydroxylase and substrate for PRODH/POX-dependent apoptosis. This evidence concerns the gene PRODH and cancer.