Identification of a dihydroorotate dehydrogenase inhibitor thatinhibits cancer cell growth by proteomic profiling

Dihydroorotate dehydrogenase(DHODH)is a central enzyme of the de novo pyrimidine biosynthesis pathway and is a promising drug target for the treatment of cancer and autoimmune diseases.This study presents the identification of a potent DHODH inhibitor by proteomic profiling.Cell-based screening revealed that NPD723,which is reduced to H-006 in cells,strongly induces myeloid differentiation and inhibits cell growth in HL-60 cells.H-006 also suppressed the growth of various cancer cells.Proteomic profiling of NPD723-treated cells in ChemProteoBase showed that NPD723 was clustered with DHODH inhibitors.H-006 potently inhibited human DHODH activity in vitro,whereas NPD723 was approximately 400 times less active than H-006.H-006-induced cell death was rescued by the addition of the DHODH product orotic acid.Moreover,metabolome analysis revealed that H-006 treatment promotes marked accumulation of the DHODH substrate dihydroorotic acid.These results suggest that NPD723 is reduced in cells to its active metabolite H-006,which then targets DHODH and suppresses cancer cell growth.Thus,H-006-related drugs represent a potentially powerful treatment for cancer and other diseases.

Triazole Ureas Covalently Bind to Strigolactone Receptor and Antagonize Strigolactone Responses

Strigolactones,a class of plant hormones with multiple functions,mediate plant-plant and plantmicroorganism communications in the rhizosphere.In this study,we developed potent strigolactone antagonists,which covalently bindto the strigolactone receptor D14,by preparing an array of triazole urea compounds.Using yeast two-hybrid and rice-tillering assays,we identified a triazole urea compound KK094 as a potent inhibitor of strigolactone receptors.Liquid chromatography-tandem mass spectrometry analysis and X-ray crystallography revealed that KK094 was hydrolyzed by D14,and that a reaction product of this degradation covalently binds to the Ser residue of the catalytic triad of D14.Furthermore,we identified two triazole urea compounds KK052 and KK073,whose effects on D14-D53/D14-SLR1 complex formation were opposite due to the absence (KK052)or presence (KK073)of a trifluoromethyl group on their phenyl ring.These results demonstrate that triazole urea compounds are potentially powerful tools for agricultural application and may be useful for the elucidation of the complicated mechanism underlying strigolactone perception.