Novel tricyclic inhibitors of farnesyl protein transferase. Biochemical characterization and inhibition of Ras modification in transfected Cos cells.
Ras protooncogenes encode 21-kDa membrane-associated guanine nucleotide-binding proteins, which play a critical role in control of cellular proliferation and differentiation. Oncogenic, activated forms of Ras proteins are associated with a broad range of human cancers. The elucidation of the post-translational modifications that occur at the carboxyl terminus of Ras and the demonstration that farnesylation of Ras by farnesyl protein transferase is essential for Ras-induced cellular transformation has opened up a new and promising approach to the development of anti-Ras therapeutics. We report here a novel series of potent farnesyl protein transferase (FPT) inhibitors, represented by SCH 44342. This compound inhibits both rat brain and recombinant human FPT with an IC50 of approximately 250 nM, while it is only weakly active against rat brain geranylgeranyl protein transferase-1 (IC50 > 114 microM). FPT inhibition has been observed using both Ha-Ras protein and Ki-Ras-derived peptide substrates in two different assay formats. SCH 44342 and its analogs also inhibit farnesylation of Ras in Cos cells transiently expressing [Val12]Ha-Ras with IC50 values in the low micromolar range. At these concentrations they do not inhibit sterol biosynthesis or geranylgeranylation of protein. In addition, we observed that Cos cells undergo pronounced morphological changes upon overexpression of [Val12]activated forms of Ha-Ras containing COOH-terminal sequences allowing farnesylation (CVLS) or geranylgeranylation (CVLL) but not upon overexpression of activated Ras lacking the isoprenylated Cys (SVLS). Ras-induced morphological changes can be partially reverted with lovastatin. Importantly, SCH 44342 can block morphological changes induced by [Val12]Ha-Ras-CVLS but not [Val12]Ha-Ras-CVLL. Recently, a number of other FPT inhibitors have been reported. Most of the compounds reported to have cell-based activity are peptidomimetic analogs of the CAAX substrate. Our FPT inhibitors are novel in that although they compete with Ras protein in kinetic experiments they are entirely nonpeptidic in nature, they do not have oxidizable sulfhydryl functions, and they are active in cells at low micromolar concentrations.
Department of Molecular Pharmacology, Schering-Plough Research Institute, Kenilworth, New Jersey 07033, USA.
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Bishop
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Bond
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Petrin
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Wang
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Patton
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Doll
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Njoroge
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Catino
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Schwartz
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Windsor
D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001552:Benzazepines / Q000494:pharmacology*; D001921:Brain / Q000201:enzymology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002522:Chlorocebus aethiops; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010880:Piperidines / Q000494:pharmacology*; D017354:Point Mutation; D011499:Protein Processing, Post-Translational; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000302:isolation & purification; D013379:Substrate Specificity; D014162:Transfection; D014166:Transferases / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000302:isolation & purification
D001552:Benzazepines; D004791:Enzyme Inhibitors; D009838:Oligodeoxyribonucleotides; D010880:Piperidines; D011994:Recombinant Proteins; C097312:SCH 44342; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C064911:p21(ras) farnesyl-protein transferase; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)