Farnesyl Pyrophosphate Analogue Research Articles

Mevalonate Pathway Promiscuity Enables Noncanonical Terpene Production.

Lepidoptera (butterflies and moths) make the six-carbon compounds homoisopentenyl pyrophosphate (HIPP) and homodimethylallyl pyrophosphate (HDMAPP) that are incorporated into 16, 17, and 18 carbon farnesyl pyrophosphate (FPP) analogues. In this work we heterologously expressed the lepidopteran modified mevalonate pathway, a propionyl-CoA ligase, and terpene cyclases in E. coli to produce several novel terpenes containing 16 carbons. Changing the terpene cyclase generated different novel terpene product profiles. To further validate the new compounds we confirmed 13C propionate was incorporated, and that the masses and fragmentation patterns were consistent with novel 16 carbon terpenes by GC-QTOF. On the basis of the available farnesyl pyrophosphate analogues lepidoptera produce, this approach should greatly expand the reachable biochemical space with applications in areas where terpenes have traditionally found uses.

ChemInform Abstract: An Expeditious Synthesis of Pyrophosphate Analogues of Farnesyl Pyrophosphate Using the Phosphonylating Agent Methyl Methylphosphonomorpholidate.

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A Tagging-via-substrate Approach to Detect the Farnesylated Proteome Using Two-dimensional Electrophoresis Coupled with Western Blotting

Prenylation is a post-translational modification critical for the proper function of multiple physiologically important proteins, including small G-proteins, such as Ras. Methods allowing rapid and selective detection of protein farnesylation and geranylgeranylation are fundamental for the understanding of prenylated protein function and for monitoring efficacy of drugs such as farnesyltransferase inhibitors (FTIs). Although the natural substrates for prenyltransferases are farnesyl pyrophosphate and geranylgeranyl pyrophosphate, farnesyltransferase has been shown to incorporate isoprenoid analogues into protein substrates. In this study, protein prenyltransferase targets were labeled using anilinogeraniol, the alcohol precursor to the unnatural farnesyl pyrophosphate analogue 8-anilinogeranyl diphosphate in a tagging-via-substrate approach. Antibodies specific for the anilinogeranyl moiety were used to detect the anilinogeranyl-modified proteins. Coupling this highly effective labeling/detection method with two-dimensional electrophoresis and subsequent Western blotting allowed simple, rapid analysis of the complex farnesylated proteome. For example, this method elucidated the differential effects induced by two chemically distinct FTIs, BMS-214,662 and L-778,123. Although both FTIs strongly inhibited farnesylation of many proteins such as Lamins, NAP1L1, N-Ras, and H-Ras, only the dual prenylation inhibitor L-778,123 blocked prenylation of Pex19, RhoB, K-Ras, Cdc42, and Rap1. This snapshot approach has significant advantages over traditional techniques, including radiolabeling, anti-farnesyl antibodies, or mass spectroscopy, and enables dynamic analysis of the farnesylated proteome.

Towards the synthesis of bisubstrate inhibitors of protein farnesyltransferase: Synthesis and biological evaluation of new farnesylpyrophosphate analogues

Protein farnesyltransferase (FTase) has recently appeared as a new target of parasitic diseases, a field poor in drugs in development. With the aim of creating new bisubstrate inhibitors of FTase, new farnesyl pyrophosphate analogues have been studied. Farnesyl analogues with a malonic acid function exhibited the best inhibitory activity on FTase. This group was introduced into our imidazole-containing model leading to new compounds with submicromolar activities. Kinetic experiments have been realized to determine their binding mode to the enzyme.

A Novel Proteomic Approach to Define Leukemia Cell Resistance to Farnesyltransferase Inhibitors.

Abstract 3761Poster Board III-697Farnesylation is a post-translational modification critical for the proper function of multiple physiologically important proteins, including small G-proteins, such as RAS. Methods allowing rapid and selective detection of protein farnesylation are fundamental for the understanding of farnesylated protein function and for monitoring efficacy of farnesyltransferase inhibitors (FTI). While the natural substrates for prenyltransferases are farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), FTase has been shown to incorporate isoprenoid analogues into protein substrates. Materials and MethodsFTase targets in three different myeloid leukemia cell lines (HL-60, K562 and NB-4) were labeled using the unnatural FPP analogue 8-anilinogeranyl diphosphate (AGPP) in a tagging-via-substrate approach. Antibodies specific for the anilinogeranyl moiety were used to detect AG-modified proteins. This highly effective labeling/detection method was coupled with two-dimensional electrophoresis (2-DE) and subsequent Western blotting. Identities of individual protein spots were determined by overlaying anti-AG immunoblots and immunoblots probed with antibodies specific for different known prenylation target proteins, such as RAS-family proteins. The clinically tested FTIs BMS-214,662 and L-778,123 as well as the nitrogen-containing bisphosphonate zoledronate were used to further validate the specificity of this labeling technique. As a proof of principle of the ability of this approach to identify target proteins important for FTI resistance, RNA interference (RNAi) was applied to investigate the role of one of the specific protein targets (K-RAS) which remained AG-labelled in the presence of FTI BMS-214,662. Following confirmation of K-RAS silencing by Western blotting, flow cytometric analysis of Annexin-V stained cells was used to quantify the effect of K-RAS silencing on BMS-214,662-induced apoptosis. ResultsMetabolic labeling of prenylated proteins with anilinogeranyl (AG) occurred in a time-dependent manner. This method provided increased resolution of the prenylated proteome as we were able to detect as many as ten distinct protein spots corresponding to a single band at approximately 20 kDa observed by 1D SDS-PAGE. Some of the proteins we have identified using this overlay method include H-RAS, K-RAS, N-RAS, Rap1, RhoB, RhoC, pre-Lamin A, Lamin B, and LKB1. AG-specific signals decreased upon FTI treatment, further substantiating the specificity of this method. Additional evidence of the specificity of this approach was the observation that the bisphosphonate inhibitor zoledronate did not inhibit protein AG-labeling. Interestingly, this method allowed direct evaluation of specific FTI targets as demonstrated by the different efficacies we observed between the two FTIs studied here – BMS-214,662 and L-778,123. This method even allowed identification of subtle differences among the leukemia cell lines tested. Closer evaluation of the farnesylated proteome demonstrated clear differences between BMS-214,662 and L-778,123, consistent with earlier reports that FTIs elicit numerous cellular effects, including induction of apoptosis and cytostatic effects. While BMS-214,662 effectively inhibited farnesylation of the majority of larger molecular weight proteins, L-778,123 also blocked prenylation of smaller molecular weight proteins such as N-RAS and K-RAS. However, RhoB and RhoC remained farnesylated regardless of FTI treatment. BMS-214,662-induced apoptosis was substantially potentiated by RNAi knock-down of K-RAS expression. ConclusionsThis snapshot approach allowed simple, rapid and dynamic analysis of the complex farnesylated proteome in leukemia cells. Our results demonstrate that this method can be used to identify and validate specific inhibitor targets. Importantly, this approach also successfully identified proteins (e.g. K-RAS) which may be important for resistance to some FTIs, and thus may be useful in directing development of more efficient therapeutic regimens. Disclosures:No relevant conflicts of interest to declare.

Synthesis of imidazole-containing analogues of farnesyl pyrophosphate and evaluation of their biological activity on protein farnesyltransferase

With the aim of creating new bisubstrate inhibitors of protein farnesyltransferase (FTase), new carboxylic farnesyl pyrophosphate analogues have been designed and synthesized. The original structures are built around three elements: a prenyl moiety, a 1,4-diacid motif and an imidazole ring. All the compounds were evaluated for their ability to inhibit FTase and compared with the corresponding derivatives lacking the imidazole ring, synthesized for that purpose. These new compounds are not bisubstrate inhibitors probably because the imidazole ring is not in the right position to interact with the zinc atom. However these derivatives display FPP competitive inhibition with a good activity in the carboxylic farnesyl pyrophosphate analogues series.

Crystal Structures of Undecaprenyl Pyrophosphate Synthase in Complex with Magnesium, Isopentenyl Pyrophosphate, and Farnesyl Thiopyrophosphate: ROLES OF THE METAL ION AND CONSERVED RESIDUES IN CATALYSIS

Undecaprenyl pyrophosphate synthase (UPPs) catalyzes the consecutive condensation reactions of a farnesyl pyrophosphate (FPP) with eight isopentenyl pyrophosphates (IPP), in which new cis-double bonds are formed, to generate undecaprenyl pyrophosphate that serves as a lipid carrier for peptidoglycan synthesis of bacterial cell wall. The structures of Escherichia coli UPPs were determined previously in an orthorhombic crystal form as an apoenzyme, in complex with Mg(2+)/sulfate/Triton, and with bound FPP. In a further search of its catalytic mechanism, the wild-type UPPs and the D26A mutant are crystallized in a new trigonal unit cell with Mg(2+)/IPP/farnesyl thiopyrophosphate (an FPP analogue) bound to the active site. In the wild-type enzyme, Mg(2+) is coordinated by the pyrophosphate of farnesyl thiopyrophosphate, the carboxylate of Asp(26), and three water molecules. In the mutant enzyme, it is bound to the pyrophosphate of IPP. The [Mg(2+)] dependence of the catalytic rate by UPPs shows that the activity is maximal at [Mg(2+)] = 1 mm but drops significantly when Mg(2+) ions are in excess (50 mm). Without Mg(2+), IPP binds to UPPs only at high concentration. Mutation of Asp(26) to other charged amino acids results in significant decrease of the UPPs activity. The role of Asp(26) is probably to assist the migration of Mg(2+) from IPP to FPP and thus initiate the condensation reaction by ionization of the pyrophosphate group from FPP. Other conserved residues, including His(43), Ser(71), Asn(74), and Arg(77), may serve as general acid/base and pyrophosphate carrier. Our results here improve the understanding of the UPPs enzyme reaction significantly.

Zoledronic Acid Mediates Ras-Independent Growth Inhibition of Prostate Cancer Cells

Zoledronic acid (ZOL), the most potent known bisphosphonate, is clinically efficacious against advanced prostate cancer, although the molecular mechanism by which bisphosphonates prevent prostate cancer cell growth remains unknown. Because Ras is the most thoroughly characterized member of the small G-proteins involved in the regulation of many cellular functions including several oncogenic pathways, the aim of this study was to clarify whether Ras is the molecular target of ZOL in prostate cancer cells. The prostate cancer cell lines PC-3, DU145, and LNCaP were used. Cell proliferation was determined by a modified MTT assay. Geranylgeranyol (GGOH) and famesol (FOH) were used as analogues of geranylgeranyl-pyrophosphate and farnesyl-pyrophosphate, respectively. Changes in expression and/or membrane localization of Ras, Rap1, and phosphorylated MAPK were evaluated by Western blotting. ZOL mediated growth inhibition of prostate cancer cells in a dose- and time-dependent manner. The ZOL-induced growth inhibitory effect was circumvented by the addition of GGOH. In contrast, FOH did not reverse the growth inhibitory effect of ZOL. The amount of membrane-anchored Ras was clearly independent of ZOL-mediated growth inhibition. Unexpectedly, ZOL induced N- and H-Ras expression of the cytosolic fraction. Ras does not appear to be the molecular target for ZOL-induced growth inhibition. Prevention of geranylgeranylation rather than farnesylation is an important therapeutic target in prostate cancer.

Synthesis and Activity of Fluorescent Isoprenoid Pyrophosphate Analogues

New fluorescent analogues of farnesol and geranylgeraniol have been prepared and then converted to the corresponding pyrophosphates. These analogues incorporate anthranylate or dansyl-like groups anchored to the terpenoid skeleton through amine bonds that would be expected to be relatively stable to metabolism. After addition of the alcohols or the pyrophosphates to the culture medium, their fluorescence is readily observed inside a human-derived leukemia cell line. Enzyme assays have revealed that the farnesyl pyrophosphate analogue is an inhibitor of FTase, while the corresponding alcohol is not. These results, together with Western blot analyses of cell lysates, indicate that the farnesyl pyrophosphate analogue penetrates the cells as an intact pyrophosphate and that it does so at a biologically relevant concentration.

α‐Phosphono Lactone Analogues of Farnesyl Pyrophosphate: An Asymmetric Synthesis via Ring‐Closing Metathesis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Alpha-phosphono lactone analogues of farnesyl pyrophosphate: an asymmetric synthesis via ring-closing metathesis.

An alpha-phosphono lactone derivative of farnesol has been prepared, in both racemic and nonracemic forms, to provide a new type of farnesyl pyrophosphate analogue. Attempted preparation of the racemic alpha-phosphono lactone through rearrangement of a vinyl phosphate derived from the parent lactone resulted in both rearrangement and lactone ring opening, revealing that the farnesyl lactone was not stable to the excess of strong base required for the rearrangement. A procedure for C-P bond formation based on generation of the lactone enolate, reaction with a P(III) reagent, and oxidation was successful in providing the racemic alpha-phosphono lactone, in part, because only 1 equiv of strong base was required. The same strategy for phosphonate synthesis then was applied to the nonracemic farnesyl lactone, prepared through a sequence including allylation of farnesal with a nonracemic borane reagent, reaction of the product alcohol with acryloyl chloride, and formation of an unsaturated lactone through ring-closing metathesis. A similar strategy gave the corresponding racemic alpha-phosphono lactam through a six-step sequence from farnesal.

Photoaffinity analogues of farnesyl pyrophosphate transferable by protein farnesyl transferase.

Farnesylation is a posttranslational lipid modification in which a 15-carbon farnesyl isoprenoid is linked via a thioether bond to specific cysteine residues of proteins in a reaction catalyzed by protein farnesyltransferase (FTase). We synthesized analogues (3-6) of farnesyl pyrophosphate (FPP) to probe the range of modifications possible to the FPP skeleton which allow for efficient transfer by FTase. Photoaffinity analogues of FPP (5, 6) were prepared by substituting perfluorophenyl azide functional groups for the omega-terminal isoprene of FPP. Substituted anilines replace the omega-terminal isoprene in analogues 3 and 4. Compounds 3-5 were prepared by reductive amination of the appropriate anilines with 8-oxo-geranyl acetate, followed by ester hydrolysis, chlorination, and pyrophosphorylation. Additional substitution of three methylenes for the beta-isoprene of FPP gave photoprobe 6 in nine steps. Preparation of the analogues required TiCl(4)-mediated imine formation prior to NaBH(OAc)(3) reduction for anilines with a pK(a) < 1. The azide moiety was not affected by Ph(3)PCl(2) conversion of allylic alcohols 13-16 into corresponding chlorides 17-20. Analogues 3-6 are efficiently transferred to target N-dansyl-GCVLS peptide substrate by mammalian FTase. Comparison of analogue structures and kinetics of transfer to those of FPP reveals that ring fluorination and para substituents have little effect on the affinity of the analogue pyrophosphate for FTase and its transfer efficiency. These results are also supported with models of the analogue binding modes in the active site of FTase. The transferable azide photoprobe 5 photoinactivates FTase. Transferable analogues 5 and 6 allow the formation of appropriately posttranslationally modified photoreactive peptide probes of isoprene function.

Probing the Conformational Change of Escherichia coliUndecaprenyl Pyrophosphate Synthase during Catalysis Using an Inhibitor and Tryptophan Mutants

Undecaprenyl pyrophosphate synthase (UPPS) catalyzes the consecutive condensation reactions of eight isopentenyl pyrophosphate (IPP) with farnesyl pyrophosphate (FPP) to generate C(55) undecaprenyl pyrophosphate (UPP). In the present study, site-directed mutagenesis, fluorescence quenching, and stopped-flow methods were utilized to examine the substrate binding and the protein conformational change. (S)-Farnesyl thiopyrophosphate (FsPP), a FPP analogue, was synthesized to probe the enzyme inhibition and events associated with the protein fluorescence change. This compound with a much less labile thiopyrophosphate shows K(i) value of 0.2 microm in the inhibition of Escherichia coli UPPS and serves as a poor substrate, with the k(cat) value (3.1 x 10(-7) s(-1)) 10(7) times smaller than using FPP as the substrate. Reduction of protein intrinsic fluorescence was observed upon addition of FPP (or FsPP) to the UPPS solution. Moreover, fluorescence studies carried out using W91F and other mutant UPPS with Trp replaced by Phe indicate that FPP binding mainly quenches the fluorescence of Trp-91, a residue in the alpha3 helix that moves toward the active site during substrate binding. Using stopped-flow apparatus, a three-phase protein fluorescence change with time was observed by mixing the E.FPP complex with IPP in the presence of Mg(2+). However, during the binding of E.FsPP with IPP, only the fastest phase was observed. These results suggest that the first phase is due to the IPP binding to E.FPP complex, and the other two slow phases are originated from the protein conformational change. The two slow phases coincide with the time course of FPP chain elongation from C(15) to C(55) and product release.

Synthesis of vinyl pyrophosphonate analogues of farnesyl pyrophosphate: New potential inhibitors of farnesyl protein transferase

AbstractThe synthesis of new bioisosteric analogues of farnesyl pyrophosphate where a vinyl pyrophosphonate replaced the pyrophosphate moiety is described. These compounds have been prepared using a Horner–Wadsworth–Emmons procedure and a modified Michelson reaction. They have been evaluated for the inhibition of farnesyl protein transferase. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:654–661, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10081

Non-peptidic prenyltransferase inhibitors: diverse structural classes and surprising anti-cancer mechanisms.

The development of farnesyltransferase inhibitors (FTIs) has been one of the most active areas of anticancer drug development for the past ten years. This review presents a general overview of the developments in this area, along with a critical appraisal of the anticancer activity of FTIs. A historical survey of the protein prenylation field is given, in particular to emphasize the key role played by the Ras oncoprotein in driving the discovery of prenyltransferase enzymes. The different classes of prenylated proteins will be described along with the biochemical characteristics of the key drug target--farnesyltransferase (FTase). Numerous potent farnesyltransferase inhibitors have been developed. The FTIs developed can be separated into three different categories, based on their origin and/or mechanism of action: a) natural products; b) peptidomimetics and other CAAX-competitive inhibitors; c) farnesyl pyrophosphate (FPP) mimetics or analogs and other FPP-competitive inhibitors. Along with a survey of newer FTIs in each class, the development of several representative, potent compounds will be discussed in depth as we discuss the potential advantages and liabilities of each class. Particular emphasis is given to the discovery of new, more potent FPP-competitive FTIs of several diverse structural classes. Testing of different FTIs for their ability to block the growth of various cancer cell types in animal models will be discussed. There are a number of key differences between these compounds and traditional cytotoxic cancer chemotherapeutic agents, with surprising exceptions to their expected modes of action. As some FTIs have entered human clinical trials, answers may soon become available to key mechanistic questions concerning the extent and nature of their antitumor growth properties.

Protein farnesyltransferase isoprenoid substrate discrimination is dependent on isoprene double bonds and branched methyl groups.

Farnesylation is a posttranslational lipid modification in which a 15-carbon farnesyl isoprenoid is linked via a thioether bond to specific cysteine residues of proteins in a reaction catalyzed by protein farnesyltransferase (FTase). We synthesized the benzyloxyisoprenyl pyrophosphate (BnPP) series of transferable farnesyl pyrophosphate (FPP) analogues (1a-e) to test the length dependence of the isoprenoid substrate on the FTase-catalyzed transfer of lipid to protein substrate. Kinetic analyses show that pyrophosphates 1a-e and geranyl pyrophosphate (GPP) transfer with a lower efficiency than FPP whereas geranylgeranyl pyrophosphate (GGPP) does not transfer at all. While a correlation was found between K(m) and analogue hydrophobicity and length, there was no correlation between k(cat) and these properties. Potential binding geometries of FPP, GPP, GGPP, and analogues 1a-e were examined by modeling the molecules into the active site of the FTase crystal structure. We found that analogue 1d displaces approximately the same volume of the active site as does FPP, whereas GPP and analogues 1a-c occupy lesser volumes and 1e occupies a slightly larger volume. Modeling also indicated that GGPP adopts a different conformation than the farnesyl chain of FPP, partially occluding the space occupied by the Ca(1)a(2)X peptide in the ternary X-ray crystal structure. Within the confines of the FTase pocket, the double bonds and branched methyl groups of the geranylgeranyl chain significantly restrict the number of possible conformations relative to the more flexible lipid chain of analogues 1a-e. The modeling results also provide a molecular explanation for the observation that an aromatic ring is a good isostere for the terminal isoprene of FPP.

2-(Acyloxy)ethylphosphonate analogues of prenyl pyrophosphates: synthesis and biological characterization

2-(Acyloxy)ethylphosphonate analogues of geranyl, farnesyl, and geranylgeranyl pyrophosphate have been prepared. Horner–Wadsworth–Emmons condensation of different terpene aldehydes with an unsymmetrical bisphosphonate was the key step in syntheses of the phosphonates bearing α,β-unsaturated acyloxy groups. After preparation of the respective phosphonic acids through reaction with TMSBr, both acids and esters were tested for their effects on DNA synthesis in human-derived myeloid and lymphoid leukemia cell lines. The phosphonate esters varied substantially in their ability to impair proliferation of the different cell lines, but testing against one possible target, farnesyl protein transferase (FPTase), revealed little impact at concentrations ranging up to 10 μM. Because the corresponding 2,3-dihydro compounds showed similar biological activity, conjugate addition would not appear to be involved in the toxicity.

Inhibitors of prenylation of Ras and other G-proteins and their application as therapeutics

Anchoring of small G-proteins to cellular membranes via a covalently bound lipophylic prenyl group is essential for the functioning of these proteins. For example, the farnesylation of Ras by the action of the enzyme protein:farnesyl transferase (PFT) is pivotal for its signalling function in cell growth and differentiation. The development of inhibitors of PFT was triggered by the role of mutated Ras in certain types of cancer and by the observation that non-farnesylated Ras is inactive. Besides the screening of existing compounds for PFT inhibition, rational drug design has also led to new inhibitors. Our research is in the field of atherosclerosis and concerns the development of inhibitors of the growth of vascular smooth muscle cells. The latter process gives rise to reocclusion of the coronary artery (restenosis) after balloon angioplasty. We and others have developed several analogues of the two substrates of PFT, i.e. farnesyl pyrophosphate (FPP) and the so-called CAAX peptide consensus sequence, which were tested in vitro for the inhibition of PFT and of other enzymes involved in protein prenylation, such as protein:geranylgeranyl transferase-1 (PGGT-1). The FPP analogue TR006, a strong inhibitor of PFT ( ic 50 of 67 nM), blocked the proliferation of cultured human smooth muscle cells and inhibited platelet-derived growth factor- and basic fibroblast growth factor-induced DNA synthesis. Similar but more highly charged compounds failed in this respect, probably because of an impaired uptake in the cells. Less charged derivatives were designed to circumvent this problem. The effect on the GF-induced activation of intermediates in signal transduction pathways was investigated in order to gain insight into the mechanism of action within the cells. TR006 decreased the bFGF activation of extracellular signal-regulated kinase 1 (ERK1), suggesting its involvement in inhibiting Ras activity. Although other analogues inhibited DNA synthesis, they affected neither ERK1 activation nor p38/stress-activated protein kinase 2 or Jun N-terminal kinase 1 activation. Since some of these compounds were also shown to be inhibitors of in vitro PGGT-1 activity, the geranylgeranylation of other G-proteins may be decreased by these compounds. Rho seems to be a good candidate as a target for inhibitors of PGGT-1. This uncertainty as to the mechanism of action within non-transformed as well as transformed cells applies to all prenylation inhibitors, but is not holding back their further development as drugs. Their current and possible future application as therapeutics in cancer, restenosis, angiogenesis, and osteoporosis is briefly discussed.

Inhibition of farnesyltransferase with A-176120, a novel and potent farnesyl pyrophosphate analogue

Farnesylation of Ras is required for its transforming activity in human cancer and the reaction is catalysed by the enzyme farnesyltransferase. Recently, we discovered a novel chemical series of potent farnesyl pyrophosphate (FPP) analogues which selectively inhibited farnesyltransferase. Our most potent compound to date in this series, A-176120, selectively inhibited farnesyltransferase activity (IC 50 1.2±0.3 nM) over the closely related enzymes geranylgeranyltransferase I (GGTaseI) (IC 50 423±1.8 nM), geranylgeranyltransferase II (GGTaseII) (IC 50 3000 nM) and squalene synthase (SSase) (IC 50>10 000 nM). A-176120 inhibited ras processing in H- ras-transformed NIH3T3 cells and HCT116 K- ras-mutated cells (ED 50 1.6 and 0.5 μM, respectively). The anti-angiogenic potential of A-176120 was demonstrated by a decrease in Ras processing, cell proliferation and capillary structure formation of human umbilical vein endothelial cells (HUVEC), and a decrease in the secretion of vascular endothelial growth factor (VEGF) from HCT116 cells. In vivo, A-176120 reduced H- ras NIH3T3 tumour growth and extended the lifespan of nude mice inoculated with H- or K- ras-transformed NIH3T3 cells. A-176120 also had an additive effect in combination with cyclophosphamide in nude mice inoculated with K- ras NIH3T3 transformed cells. Overall, our results demonstrate that A-176120 is a potent FPP mimetic with both antitumour and anti-angiogenic properties.

Design and Synthesis of a Transferable Farnesyl Pyrophosphate Analogue to Ras by Protein Farnesyltransferase

The posttranslational addition of a farnesyl moiety to the Ras oncoprotein is essential for its membrane localization and is required for both its biological activity and ability to induce malignant transformation. We describe the design and synthesis of a farnesyl pyrophosphate (FPP) analogue, 8-anilinogeranyl pyrophosphate 3 (AGPP), in which the omega-terminal isoprene unit of the farnesyl group has been replaced with an aniline functionality. The key steps in the synthesis are the reductive amination of the alpha,beta-unsaturated aldehyde 5 to form the lipid analogue 6, and the subsequent conversion of the allylic alcohol 7 to the chloride 8 via Ph(3)PCl(2) followed by displacement with [(n-Bu)(4)N](3)HP(2)O(7) to give AGPP (3). AGPP is a substrate for protein farnesyltransferase (FTase) and is transferred to Ras by FTase with the same kinetics as the natural substrate, FPP. AGPP is highly selective, showing little inhibitory activity against either geranylgeranyl-protein transferase type I (GGTase I) (K(i) = 0.06 microM, IC(50) = 20 microM) or squalene synthase (IC(50) = 1000 microM). AGPP is the first efficiently transferable analogue of FPP to be modified at the omega-terminus that provides a platform from which additional analogues can be made to probe the biological function of protein farnesylation. AGPP is the first example of a class of compounds that are alternate substrates for protein isoprenylation that are not inhibitors of squalene synthase.