Biochemical evaluation of the anticancer potential of the polyamine-based nanocarrier Nano11047

Synthesizing polycationic polymers directly from existing drugs overcomes the drug-loading limitations often associated with pharmacologically inert nanocarriers. We recently described nanocarriers formed from a first-generation polyamine analogue, bis(ethyl)norspermine (BENSpm), that could simultaneously target polyamine metabolism while delivering therapeutic nucleic acids. In the current study, we describe the synthesis and evaluation of self-immolative nanocarriers derived from the second-generation polyamine analogue PG-11047. Polyamines are absolutely essential for proliferation and their metabolism is frequently dysregulated in cancer. Through its effects on polyamine metabolism, PG-11047 effectively inhibits tumor growth in cancer cell lines of multiple origins as well as in human tumor mouse xenografts. Promising clinical trials have been completed verifying the safety and tolerance of this rotationally restricted polyamine analogue. We therefore used PG-11047 as the basis for Nano11047, a biodegradable, prodrug nanocarrier capable of targeting polyamine metabolism. Following exposure of lung cancer cell lines to Nano11047, uptake and intracellular degradation into the parent compound PG-11047 was observed. The release of PG-11047 highly induced the polyamine catabolic enzyme activities of spermidine/spermine N1-acetyltransferase (SSAT) and spermine oxidase (SMOX). By contrast, the activity of ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine biosynthesis and a putative oncogene, was decreased. Consequently, intracellular levels of the natural polyamines were depleted concurrent with tumor cell growth inhibition. This availability of Nano11047 as a novel drug form and potential nucleic acid delivery vector will potentially benefit and encourage future clinical studies.

Synthesis of novel cationic spermine-conjugated phosphotriester oligonucleotide for improvement of cell membrane permeability

A spermine-conjugated ethyl phosphotriester oligonucleotide was obtained by solid-phase synthesis based on phosphoramidite chemistry. The ethyl phosphotriester linkage was robust to exonuclease digestion and stable in fetal bovine serum. Cell membrane permeability of the spermine-conjugated ethyl phosphotriester oligonucleotide was studied by fluorescence experiments. The effective cell penetrating potency of the spermine-conjugated ethyl phosphotriester oligonucleotide was determined by confocal laser scanning microscopy and measurement of intracellular fluorescence intensity.

[Stable analogues of coenzyme-substrate complex of spermidine/spermine-N1-acetyltransferase reaction. synthesis, interaction with the enzyme]

Convenient two-step synthesis of conjugates of HS-CoA and D-pantetheine with aminooxy analogues of Spm, Spd and Put was suggested. The use of acetone linker provided target conjugates with quantitative yields. The activity of CoA-derived "bisubstrate" inhibitors being active at microM concentrations was at least 100 times better than that of corresponding derivatives of D-pantetheine.

Macrophage mannose receptor-specific gene delivery vehicle for macrophage engineering

Macrophages are the most plastic cells in the hematopoietic system and they exhibit great functional diversity. They have been extensively applied in anti-inflammatory, anti-fibrotic and anti-cancer therapies. However, the application of macrophages is limited by the efficiency of their engineering. The macrophage mannose receptor (MMR, CD206), a C-type lectin receptor, is ubiquitously expressed on macrophages and has a high affinity for mannose oligosaccharides. In the present study, we developed a novel non-viral vehicle with specific affinity for MMR. Mannan was cationized with spermine at a grafted ratio of ∼12% to deliver DNA and was characterized as a stable system for delivery. This spermine-mannan (SM)-based delivery system was evaluated as a biocompatible vehicle with superior transfection efficiency on murine macrophages, up to 28.5-fold higher than spermine-pullulan, 11.5-fold higher than polyethylenimine and 3.0-fold higher than Lipofectamine™ 2000. We confirmed that the SM-based delivery system for macrophages transfection was MMR-specific and we described the intracellular transport of the delivery system. To our knowledge, this is the first study using SM to demonstrate a mannose receptor-specific gene delivery system, thereby highlighting the potential of a novel specific non-viral delivery vehicle for macrophage engineering.

[Acetylsalicylic acid strengthens the effects of ANISpm against hepatocellular carcinoma and its molecular mechanism]

The objective of this study is to examine the effects of ANISpm, a novel polyamine naphthalimide conjugate, with acetylsalicylic acid against hepatocellular carcinoma in vivo and in vitro and elucidate its potential molecular mechanism. The proliferation inhibition was detected by MTT assay. Cell apoptosis, intracellular fluorescence intensity and mitochondrial membrane potential (MMP) were detected by high content screening (HCS) analysis. Polyamines content was analyzed by reverse-phase high performance liquid chromatography Protein expression levels were quantified by Western blotting assay. The combination treatment strongly inhibited cell proliferation, induced cell apoptosis in HepG2 cells and H22 hepatoma cells, which was mediated by enhanced ANISpm uptake via up-regulation of spermidine/spermine N1-acetyltransferase (SSAT) and depression of intracellular polyamine. Furthermore, this synergistic apoptosis was involved in mitochondria and death-receptor signal pathway. All these findings demonstrated that the combination treatment with acetylsalicylic acid and ANISpm resulted in synergistic antitumor effects on hepatoma cells. Thus, combination therapy with these agents may be useful as a potential template for the development of better chemotherapeutic strategy against hepatoma.

Fluorescent substrates for polyamine catabolic enzymes and transport

The most widely used methods for measuring polyamine enzyme activities are radioisotope methods that measure the radioactivity of compounds produced from radiolabeled substrate by the enzyme reaction. Several fluorescent polyamines have been developed for the measurement of the polyamine transport system (PTS) or transglutaminase. Although fluorophores in the fluorescent polyamines may affect the affinity of the polyamine moiety to the enzyme protein, the assays that use fluorescent substrate are sensitive and simple for common laboratory usage.In this chapter, the uses of dansyl polyamines with a simple high-performance liquid chromatography system for the measurement of the PTS and polyamine catabolic enzymes including spermidine/spermine N¹-acetyltransferase and N¹-acetylpolyamine oxidase are described.

Identification, chemical synthesis, and biological functions of unusual polyamines produced by extreme thermophiles

Unusual long polyamines such as caldopentamine and caldohexamine, and branched polyamines such as tetrakis(3-aminopropyl)ammonium and N (4)-aminopropylspermidine were often found in cells of extreme thermophiles and hyperthermophiles belonging to both Bacteria and Archaea domains. Some of these unusual polyamines are essential for life at extreme temperatures. In some cases, the unusual polyamines also exist in cells of nonthermophilic organisms and play important physiological roles under normal conditions. Methods for chromatographic analysis, isolation, and chemical syntheses of unusual polyamines as well as experimental methods for measuring their physiological roles are discussed. Especially, many newly improved methods for chemical syntheses are presented in this article.

Synthesis and biological characterization of novel charge-deficient spermine analogues

Biogenic polyamines, spermidine and spermine, are positively charged at physiological pH. They are present in all cells and essential for their growth and viability. Here we synthesized three novel derivatives of the isosteric charge-deficient spermine analogue 1,12-diamino-3,6,9-triazadodecane (SpmTrien, 5a) that are N(1)-Ac-SpmTrien (5c), N(12)-Ac-SpmTrien (5b), and N(1),N(12)-diethyl-1,12-diamino-3,6,9-triazadodecane (N(1),N(12)-Et(2)-SpmTrien, 5d). 5a and 5d readily accumulated in DU145 cells at the same concentration range as natural polyamines and moderately competed for the uptake with putrescine (1) but not with spermine (4a) or spermidine (2). 5a efficiently down-regulated ornithine decarboxylase and decreased polyamine levels, while 5d proved to be inefficient, compared with N(1),N(11)-diethylnorspermine (6). None of the tested analogues were substrates for human recombinant spermine oxidase, but those having free aminoterminus, including 1,8-diamino-3,6-diazaoctane (Trien, 3a), were acetylated by mouse recombinant spermidine/spermine N(1)-acetyltransferase. 5a was acetylated to 5c and 5b, and the latter was further metabolized by acetylpolyamine oxidase to 3a, a drug used to treat Wilson's disease. Thus, 5a is a bioactive precursor of 3a with enhanced bioavailability.

New stereoselective titanium reductive amination synthesis of 3-amino and polyaminosterol derivatives possessing antimicrobial activities

A series of 3-amino and polyaminosterol analogues of squalamine and trodusquemine were synthesized involving a new stereoselective titanium reductive amination reaction in high chemical yields of up to 95% in numerous cases. These derivatives were evaluated for their in vitro antimicrobial properties against human pathogens. Activity was highly dependent on the different compounds' structures involved and best results have been obtained with aminosterol derivatives 4b, 4e and 6i exhibiting activities against yeasts, Gram positive and Gram negative bacteria at average concentrations of 6.25-12.5 microg/mL.

Spermined dextran, a cationized polymer, as absorption enhancer for pulmonary application of peptide drugs

Sperminated dextrans (SD) having different average molecular weights (MWs; 10, 40 and 70 kDa) and numbers of amino groups were prepared as cationized polymers for use as absorption enhancers. The absorption enhancing effects on the pulmonary absorption of insulin in rats and the permeation of FITC-dextran (MW 4,400, FD4) through calu-3 cell (human airway epithelial cell) monolayers by SD were evaluated. SD significantly enhanced the pulmonary absorption of insulin SD and the permeation of FD4 through calu-3 cells. The enhancing effects on the absorption insulin and permeation of FD4 through calu-3 cells increased with an increase in the molecular weigh of SD over the range 10-70 kDa. SD may interact directly with the luminal surface of mucus membranes via an ion-ion interaction and then induce signals that open tight junctions resulting in intercellular permeation of water soluble drugs. SD may be useful as an absorption enhancer for pulmonary delivery of peptide and protein drugs.

Novel approach to design an isosteric charge-deficient analogue of spermine and its biochemically important derivatives

The design and synthesis of SpmTrien (1,12-diamino-3,6,9-triazadodecane), an isosteric and charge-deficient analogue of spermine with excellent chelating properties towards Cu2+ ions, as well as novel N1- and N12-Ac-SpmTriens and bis-Et-SpmTrien (N1,N12-diethyl-1,12-diamino-3,6,9-triazadodecane) are described. Possible applications of SpmTrien and its derivatives to the investigation of the enzymes of polyamine metabolism and spermine cellular functions, including interaction with DNA, are discussed.

Polycationic Sulfonamides for the Sequestration of Endotoxin

Lipopolysaccharides (LPS) play a key role in the pathogenesis of septic shock, a major cause of mortality in the critically ill patient. We had previously shown that monoacylated polyamine compounds specifically bind to and neutralize the activity of LPS with high in vitro potency and afford complete protection in a murine model of endotoxic shock. Fatty acid amides of polyamines may be rapidly cleared from systemic circulation due to their susceptibility to nonspecific serum amidases and, thus, would be predicted to have a short duration of action. In a systematic effort to increase the likelihood of better bioavailability properties together with structural modifications that may result in gains in activity, we now report structure-activity relationships pertaining to endotoxin-binding and -neutralizing activities of homologated polyamine sulfonamides.

Varying the unsaturation in N4,N9-dioctadecanoyl spermines: nonviral lipopolyamine vectors for more efficient plasmid DNA formulation

PURPOSE

The aim of the study is to analyze the effect of varying the degree of unsaturation in synthesized N4,N9-dioctadecanoyl spermines on DNA condensation and then to compare their transfection efficiency in cell culture.

METHODS

The N4,N9-di-C18 lipopolyamines-saturated (stearoyl), C9-cis- (oleoyl), and C9,12-di-cis- (linoleoyl)-were synthesized from the naturally occurring polyamine spermine. The ability of these novel compounds to condense DNA and form nanoparticles was studied using ethidium bromide fluorescence quenching and nanoparticle characterization techniques. Transfection efficiency was studied in several primary skin cells (FEK4, FCP4, FCP5, FCP7, and FCP8) and in an immortalized cancer cell line (HtTA) and was compared with the commercially available nonliposomal transfection formulation Transfectam (dioctadecylamidoglycyl spermine), which also contains two saturated C18 lipid chains.

RESULTS

N4,N9-Dilinoleoyl spermine (C18, di-cis-9,12) is efficient at circular plasmid DNA (pEGFP) condensation and gives the most effective transfection in a series of primary skin cells and cancer cell lines at low charge ratios of 5.5 (+/-ammonium/phosphate).

CONCLUSIONS

The dienoic fatty acyl spermine conjugate N4,N9-dilinoleoyl spermine efficiently condenses DNA and achieves the highest transfection levels among the studied lipopolyamines in cultured cells.

[Aminooxy analogues of spermine and their monoacetyl derivatives]

Convenient methods of synthesis of 1-aminooxy-3,8-diaza-11-aminoundecane, its earlier unknown N1-and N1 -acetyl derivatives, and also 1,10-bis(aminooxy)-3,8-diazadecane are suggested. It is shown a possibility to selectively delete the acid-labile ethoxyethylidene protection of aminooxy group by hydrosulfates in the presence of N-tert-butyloxycarbonyl group.

Alpha-methyl polyamines: efficient synthesis and tolerance studies in vivo and in vitro. First evidence for dormant stereospecificity of polyamine oxidase

Efficient syntheses of metabolically stable alpha-methylspermidine 1, alpha-methylspermine 2, and bis-alpha,alpha'-methylated spermine 3 starting from ethyl 3-aminobutyrate are described. The biological tolerance for these compounds was tested in wild-type mice and transgenic mice carrying the metallothionein promoter-driven spermidine/spermine N(1)-acetyltransferase gene (MT-SSAT). The efficient substitution of natural polyamines by their derivatives was confirmed in vivo with the rats harboring the same MT-SSAT transgene and in vitro with the immortalized fibroblasts derived from these animals. Enantiomers of previously unknown 1-amino-8-acetamido-5-azanonane dihydrochloride 4 were synthesized starting from enantiomerically pure (R)- and (S)-alaninols. The studies with recombinant human polyamine oxidase (PAO) showed that PAO (usually splits achiral substrates) strongly favors the (R)-isomer of 4 that demonstrates for the first time that the enzyme has hidden potency for stereospecificity.

Relationships between chemical composition, physical properties and transfection efficiency of polysaccharide-spermine conjugates

Biodegradable water-soluble polysaccharide-spermine (SPM) polycation conjugates for nucleic acid delivery were synthesized by oxidizing polysaccharides using potassium periodate, followed by SPM conjugation. The polycations differ in their polysaccharide type, arabinogalactan (AG) or dextran (D), and/or in the IO(4)- /saccharide mole ratio used for polysaccharide oxidation (1:1, 1:3, or 1:5), resulting in either D(1:1)-SPM, AG(1:1)-SPM, D(1:3)-SPM, AG(1:3)-SPM, or AG(1:5)-SPM. Chemical structure of the conjugates was characterized for total nitrogen and primary amino groups. Surface pH and electrical surface potential were determined by means of spectral changes of covalently attached 7-hydroxycoumarin (HC, a pH- and electrical surface potential-sensitive fluorophore). The binding and the electrostatic neutralization of the polycations by plasmid DNA, as well as the relationship between chemical structure, physical parameters, and transfection of NIH3T3 cells, were also studied. D(1:1)-SPM, the only polycation that showed efficient cell transfection in culture, was shown to have: (1) high SPM content (2000 nmol/mg); (2) high levels of cross-linked SPM (39-51%); (3) at DNA P-/NH3+ ratio of 2.0, a plateau in neutralization of cationic groups (+48 mV, as determined by HC-labeled D(1:1)-SPM titration with DNA), and a drop in zeta-potential from +42 mV for the polymer alone to 0 mV for the polyplex, suggesting that some of the charges are hidden from the DNA; (4) pH(surface) value of 9.2, suggesting that at physiological bulk pH the polymer is only partially ionized, and therefore can act as a "proton sponge" in the endosome; and (5) high sensitivity to serum-rich growth medium. An oleyl derivative, N-oleyl-dextran-spermine (ODS), was synthesized and demonstrated improved transfection efficiency in serum-rich medium.

Lysine-spermine conjugates: hydrophobic polyamine amides as potent lipopolysaccharide sequestrants

Lipopolysaccharides (LPS), otherwise termed 'endotoxins', are outer-membrane constituents of Gram-negative bacteria. Lipopolysaccharides play a key role in the pathogenesis of 'Septic Shock', a major cause of mortality in the critically ill patient. Therapeutic options aimed at limiting downstream systemic inflammatory processes by targeting lipopolysaccharide do not exist at the present time. We have defined the pharmacophore necessary for small molecules to specifically bind and neutralize LPS and, using animal models of sepsis, have shown that the sequestration of circulatory LPS by small molecules is a therapeutically viable strategy. In this paper, the interactions of a focused library of lysine-spermine conjugates with lipopolysaccharide (LPS) have been characterized. Lysine-spermine conjugates with the epsilon-amino terminus of the lysinyl moiety derivatized with long-chain aliphatic hydrophobic substituents in acyl or alkyl linkage bind and neutralize bacterial lipopolysaccharides, and may be of use in the prevention or treatment of endotoxic shock states.

[New syntheses of alpha-methyl- and alpha,alpha'-dimethylspermine]

alpha-Methylspermine and alpha,alpha'-dimethylspermine were synthesized in high overall yields starting from N-(benzyloxycarbonyl)-3-aminobutanol in order to study polyamine biochemistry in vitro and in vivo.

Synthesis and biological evaluation of aminopolyamines

Exploitation of the polyamine backbone as a vector for intracellular transport of various pharmacophores has focused largely on fixing the cargo molecule to one of the nitrogens in the linear chain. This communication describes the assembly of a model aminopolyamine analogue, 6-amino-N(1),N(12)-diethylspermine, and its biological properties. This amino polyamine presents an additional site of attachment for cargo molecules, reduces cell growth, and achieves cellular concentrations that are higher than those of N(1),N(12)-diethylspermine.

A Charge-Deficient Analogue of Spermine with Chelating Properties

1,12-Diamino-3,6,9-triazadodecane, a new isosteric and charge-deficient analogue of spermine, is synthesized. Unlike spermine, the new analogue is an excellent chelator of Cu2+ ions. Possible applications of this compound for studying enzymes of polyamine metabolism and cellular functions of spermine are discussed. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.

Lipopolysaccharide sequestrants: structural correlates of activity and toxicity in novel acylhomospermines

Lipopolysaccharides (LPS), otherwise termed "endotoxins", are outer membrane constituents of Gram-negative bacteria. Lipopolysaccharides play a key role in the pathogenesis of "septic shock", a major cause of mortality in the critically ill patient. Therapeutic options aimed at limiting downstream systemic inflammatory processes by targeting lipopolysaccharide do not exist at the present time. We have defined the pharmacophore necessary for small molecules to specifically bind and neutralize LPS and, using animal models of sepsis, have shown that the sequestration of circulatory LPS by small molecules is a therapeutically viable strategy. In this paper, the interactions of a series of acylated homologated spermine compounds with LPS have been characterized. The optimal acyl chain length for effective sequestration of LPS was identified to be C(16) for the monoacyl compounds. The most promising of these compounds, 4e, binds LPS with an ED(50) of 1.37 muM. Nitric oxide production in murine J774A.1 cells, as well as TNF-alpha in human blood, is inhibited in a dose-dependent manner by 4e at concentrations orders of magnitude lower than toxic doses. Administration of 4e to d-galactosamine-sensitized mice challenged with supralethal doses of LPS provided significant protection against lethality. Potent antiendotoxic activity, low toxicity, and ease of synthesis render this class of compounds candidate endotoxin-sequestering agents of potential significant therapeutic value.

[New oxaanalogues of spermine]

A new isosteric charge-deficient spermine analogue, 1,12-diamino-4,9-diaza-5-oxadodecan, and O-(7-amino-4-azaheptyl)oxime of 3-aminopropanal, a stable analogue of the Schiff base intermediate in the enzymatic oxidation of spermine, were synthesized. The possible use of these compounds for the inhibition of spermine oxidase is discussed.

Ionic, Structural, and Temperature Effects on DNA Nanoparticles Formed by Natural and Synthetic Polyamines

We synthesized analogues of spermine and studied the effects of chemical structure, ionic strength, and temperature on lambda-DNA nanoparticle formation. Effective concentration of polyamines for DNA condensation (EC50) was lowest for hexamines (0.2 microM) and highest for spermine (tetramine, 4.2 microM). The EC50 value increased with [Na+]. Dynamic light scattering showed nanoparticles with hydrodynamic radii (R(h)) of 40-50 nm. Effect of temperature on R(h) was measured between 20 and 70 degrees C. For spermine, R(h) remained relatively stable until 50 degrees C and increased significantly at >60 degrees C. In contrast, the hexa- and penta-valent analogues exhibited a gradual increase in R(h) between 20 and 70 degrees C. The nanoparticles were mainly toroidal, as revealed by electron microscopy (EM). EM studies showed changes in morphology and size of condensed structures with an increase in temperature. A possible mechanism for the differential effects of temperature on DNA nanoparticles might involve different modes of DNA-polyamine interactions.

Transfection with Fluorinated Lipoplexes Based on New Fluorinated Cationic Lipids and in the Presence of a Bile Salt Surfactant

The synthesis of two fluorinated cationic lipids, which are analogues of frequently used synthetic gene carrier agents (including the cationic 2,3-dioleoyloxy-N-[2-(spermine-carboxamido)ethyl]-N,N-dimethyl-1-propanaminium (DOSPA) component of the commercially available liposomal Lipofectamine), and the disintegration and DNA accessibility (evaluated by the ethidium bromide (BET) intercalation assay) as well as the in vitro transfection efficacy of cationic lipoplexes formulated with these new lipids in conjunction with conventional or fluorinated helper lipids, in the absence or presence of sodium taurocholate (STC), a powerful anionic bile salt detergent, is reported. A higher stability, with respect to the STC lytic activity and DNA accessibility, of the fluorinated cationic lipoplexes as compared with their respective lipofectamine-based ones was demonstrated. Indeed, while the Lipofectamine lipoplexes were fully disintegrated at a [STC]/[lipid] molar ratio of 2000, only 40-60% of the DNA intercalation sites of the lipoplexes based on the fluorinated analogue of DOSPA were accessible to ethidium bromide. A higher transfection potential in the presence of STC was further found for the lipoplexes formulated with the fluorinated analogue of DOSPA as compared with the Lipofectamine preparation. For a STC concentration of 7.5 mM, lipofection mediated with these fluorinated lipoplexes was significantly higher (nearly 30- to 50-fold, p < 0.05) than with the Lipofectamine ones. These results confirm the remarkable transfection potential of fluorinated lipoplexes.

The synthesis and properties of oligoribonucleotide-spermine conjugates

Polyamines stabilise nucleic acids against chemical and enzymatic degradation, facilitate the formation of secondary and tertiary structures and enhance cellular uptake. Therefore methods for the syntheses of polyamine-nucleic acid conjugates are of interest. A route for the syntheses of RNA-spermine conjugates has been developed. The polyamine was introduced to the C-5 position of uridine via an ethyl tether and the molecule elaborated into a synthon suitable for oligoribonucleotide assembly. The resultant oligomers were components of the hairpin ribozyme. Characterisation of the spermine-conjugated catalytic RNA revealed that attachment of the polyamine was well tolerated in three of four positions, namely U41, U37 and U34, suggesting that conjugation to C-5 brings about minimal structural perturbation.

Polyamine-iron chelator conjugate

The current study demonstrates unequivocally that polyamines can serve as vectors for the intracellular delivery of the bidentate chelator 1,2-dimethyl-3-hydroxypyridin-4-one (L1). The polyamine-hydroxypyridinone conjugate 1-(12-amino-4,9-diazadodecyl)-2-methyl-3-hydroxy-4(1H)-pyridinone is assembled from spermine and 3-O-benzylmaltol. The conjugate is shown to form a 3:1 complex with Fe(III) and to be taken up by the polyamine transporter 1900-fold against a concentration gradient. The K(i) of the conjugate is 3.7 microM vs spermidine for the polyamine transporter. The conjugate is also at least 230 times more active in suppressing the growth of L1210 murine leukemia cells than is the parent ligand, decreases the activities of the polyamine biosynthetic enzymes ornithine decarboxylase and S-adenosylmethionine decarboxylase, and upregulates spermidine-spermine N (1)-acetyltransferase. However, the effect on native polyamine pools is a moderate one. These findings are in keeping with the idea that polyamines can also serve as efficient vectors for the intracellular delivery of other iron chelators.

Differential incorporation of biotinylated polyamines by transglutaminase 2

Polyamine incorporation or cross-linking of proteins, post-translational modifications mediated by transglutaminase 2 (TGase 2), have been implicated in a variety of physiological functions including cell adhesion, extracellular matrix formation and apoptosis. To better understand the intracellular regulation mechanism of TGase 2, the properties of biotinylated polyamines as substrates for determining in situ TGase activity were analyzed. We synthesized biotinylated spermine (BS), and compared the in vitro and in situ incorporation of BS with that of biotinylated pentylamine (BP), which is an artificial polyamine derivative. When measured in vitro, BP showed a significantly higher incorporation rate than BS. In contrast, in situ incorporation of both BS and BP was not detected even in TGase 2-overexpressed 293 cells. Cells exposed to high calcium showed a marked increase of BP incorporation but not of BS. These data indicate that the in situ activity of TGase 2 gives different results with different substrates, and suggest the possibility of overrepresentation of in situ TGase 2 activity when assayed with BP. Therefore, careful interpretation or evaluation of in situ TGase 2 activity may be required.

Effect of spermine conjugation on the cytotoxicity and cellular transport of acridine

Polyamines are believed to be potent vectors for the selective delivery of chemotherapeutic agents into cancer cells. In this paper, we report the effect of spermine conjugation on the cytotoxic and transport properties of acridine. Six derivatives, composed of a spermine chain attached at its N(1) position to an acridine via an aliphatic chain, were synthesized. The aliphatic linker, comprised of 3-5 methylene units, was connected to the position-9 of the heterocycle through either an amide (amidoacridines 8-10) or an amine (aminoacridines 11-13) linkage. Independently of their architecture, all ligands showed a high affinity for DNA binding but a limited DNA sequence selectivity. In a whole cell assay with L1210 and Chinese hamster ovary (CHO) cells, the aminoacridines (IC(50) values around 2 microM) were more potent than the amidoacridines (IC(50) values between 20 and 40 microM). This was related to a less efficient transport for the latter. As determined from competitive uptake studies with [(14)C]spermidine, all conjugates had a high affinity for the polyamine transport system (PTS). However, on the basis of competitive studies with an excess of spermidine and on the differential effect on cell growth and accumulation in CHO and in the mutant PTS deficient CHO-MG cells, the accumulation of the conjugates through the PTS was found to be poor but still more efficient for the aminoacridines. alpha-Difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, which induces an up-regulation of the activity of the PTS, enhanced accumulation of all acridine conjugates through the PTS and had a synergistic effect on the potency of the acridine conjugates to inhibit cell growth. Despite their high affinity for the PTS, the low amount of derivatives transiting through the PTS is likely to be related to their ability to repress rapidly and efficiently the activity of the PTS and, consequently, to inhibit their own uptake via this system.

Efficient synthesis and cell-transfection properties of a new multivalent cationic lipid for nonviral gene delivery

Lipid-mediated delivery of DNA into cells holds great promise both for gene therapy and basic research applications. This paper describes the efficient and facile synthesis and the characterization of a new multivalent cationic lipid with a double-branched headgroup structure for gene delivery applications. The synthetic scheme can be extended to give cationic lipids of different charge, spacer, or lipid chain length. The chemical and physical properties of self-assembled complexes of the cationic liposomes (CLs) with DNA give indications of why multivalent cationic lipids possess superior transfection properties. The lipid bears a headgroup with five charges in the fully protonated state, which is attached to an unsaturated double-chain hydrophobic moiety based on 3,4-dihydroxybenzoic acid. Liposomes consisting of the new multivalent lipid and the neutral lipid 1,2-dioleoyl-sn-glycerophosphatidylcholine (DOPC) were used to prepare complexes with DNA. Investigations of the structures of these complexes by optical microscopy and small-angle X-ray scattering reveal a lamellar L(alpha)(C) phase of CL-DNA complexes with the DNA molecules sandwiched between bilayers of the lipids. Experiments using plasmid DNA containing the firefly luciferase reporter gene show that these complexes efficiently transfect mammalian cells. When compared to the monovalent cationic lipid 2,3-dioleyloxypropyltrimethylammonium chloride (DOTAP), the higher charge density of the membranes of CL-DNA complexes achievable with the new multivalent lipid greatly increases transfection efficiency in the regime of small molar ratios of cationic to neutral lipid. This is desired to minimize the known toxicity effects of cationic lipids.

Novel oxa-spermine homologues: synthesis and cytotoxic properties

New oxa-spermine homologues 5-9 were synthesised and their anticancer properties were evaluated against a broad spectrum of cancer cells. All compounds, except 9 showed average GI(50) values in the range of 1.89-7.56 microM. SAR studies showed that the cytotoxic activity of these novel oxa-spermines depended on the length of the alkyl chain, the position of the oxa-amino functionality and also, on the type of sulphonamido group in the molecule. Although the mechanism of action of these compound remains to be elucidated, it would appear that direct drug-DNA interactions are not involved in the mode of action of these drugs.

Cytotoxic effects of metal complexes of biogenic polyamines. I. Platinum(II) spermidine compounds: prediction of their antitumour activity

Cytotoxicity and cell growth inhibition studies were performed for three distinct polynuclear platinum(II) complexes of spermidine, which showed to have significant cytotoxic and antiproliferative properties on the HeLa cancer cell line. The chemical environment of the metal centres in the drugs, as well as the coordination pattern of the ligand, were found to be strongly determinant of their cytotoxic ability. In the light of the results gathered, the most effective anticancer compound among the ones tested (IC50=5 microM) was found to be the one displaying three difunctional (PtCl2N2) moieties ((PtCl2)3(spd)2). Both the cytotoxic activity and the antiproliferative properties of the complexes studied showed to be irreversible for all the concentrations tested.

Amino acid/spermine conjugates: polyamine amides as potent spermidine uptake inhibitors

In this paper we describe the synthesis and characterization of a series of simple spermine/amino acid conjugates, some of which potently inhibit the uptake of spermidine into MDA-MB-231 breast cancer cells. The presence of an amide in the functionalized polyamine appeared to add to the affinity for the polyamine transporter. The extensive biological characterization of an especially potent analogue from this series, the Lys-Spm conjugate (31), showed this molecule will be an extremely useful tool for use in polyamine research. It was shown that the use of 31 in combination with DFMO led to a cytostatic growth inhibition of a variety of cancer cells, even when used in the presence of an extracellular source of transportable spermidine. It was furthermore shown that this combination effectively reduced the cellular levels of putrescine and spermidine while not affecting the levels of spermine. These facts together with the nontoxic nature of 31 make it a novel lead for further anticancer development.

Influence of polyamine architecture on the transport and topoisomerase II inhibitory properties of polyamine DNA-intercalator conjugates

An efficient five-step synthetic method was developed to access a series of spermine derivatives containing appended acridine, anthracene, and 7-chloroquinoline motifs. The derivatives were composed of a spermine fragment covalently tethered at its N4 and N9 positions to an aromatic nucleus via an aliphatic chain (e.g., 8: acridine -[C4 aliphatic tether]-spermine-[C4 aliphatic tether]-acridine). The distance separating the spermine and aromatic nuclei was altered via different tethers composed of four or five methylene units. These bis ligands (8, 9, 12, and 13) were shown to inhibit human DNA topoisomerase II (topo II) activity at 5 microM. Enzymatic activity was assessed as the ability to unknot (decatenate) and cleave kinetoplast DNA (kDNA). Polyamine conjugation did not disrupt the ability of the acridine-spermine conjugates 8 and 9 to inhibit topo II activity as compared with the 9-aminoacridine and 9-(N-butyl)aminoacridine controls (at 5 microM). The parent polyamines, spermine (5 microM) and spermidine (10 microM), had little effect on topo II activity. In general, the bis-substituted spermine derivatives (8, 9, 12, and 13) were more efficient topo II inhibitors at 5 microM than their monosubstituted spermidine counterparts (22-25) at 10 microM. Within the bisintercalator spermine series, insertion of an additional methylene unit (i.e., C5 tethers) increased potency 2-fold (8, bis-C4-acridine, 47 h IC(50) = 40 microM; 9, bis-C5-acridine, IC(50) = 17 microM). Comparison of the bis- and monoacridine spermine motifs (8 and 17) revealed a 4-fold increase in potency for the latter architecture (94 h IC(50) for 8, 74 microM; for 17, 17 microM). In general the bisintercalators (8, 9, 12, and 13) behaved as cytostatic agents, while the monosubstituted acridine and anthracene derivatives (22-25) were cytotoxic. Anthracene-containing conjugates were generally more toxic than their acridine counterparts in an L1210 (murine leukemia) cell assay. Of the conjugates tested the (monointercalator)-spermine motif (e.g., 17) had the highest affinity for the L1210 polyamine transporter as revealed by spermidine protection experiments.

Synthesis and evaluation of hydroxylated polyamine analogues as antiproliferatives

A new means of accessing N(1)-cyclopropylmethyl-N(11)-ethylnorspermine (CPMENSPM) and the first synthesis of (2R,10S)-N(1)-cyclopropylmethyl-2,10-dihydroxy-N(11)-ethylnorspermine [(2R,10S)-(HO)(2)CPMENSPM] are described. Both of these polyamine analogues are shown to be more active against L1210 murine leukemia cell growth than either N(1),N(11)-diethylnorspermine (DENSPM) or (2R,10R)-N(1),N(11)-diethyl-2,10-dihydroxynorspermine [(2R,10R)-(HO)(2)DENSPM] after 96 h of treatment; the activity was comparable to that of (2S,10S)-N(1),N(11)-diethyl-2,10-dihydroxynorspermine [(2S,10S)-(HO)(2)DENSPM] at 96 h. Both cyclopropyl compounds reduced putrescine and spermidine pools, but less effectively than did DENSPM and its derivatives. Only CPMENSPM, and not (2R,10S)-(HO)(2)CPMENSPM, lowered spermine pools. As with DENSPM and (2R,10R)-(HO)(2)DENSPM, both cyclopropyl analogues diminished ornithine decarboxylase and S-adenosylmethionine decarboxylase activity. Unlike the hydroxylated DENSPM compounds, both cyclopropyl norspermines substantially upregulated spermidine/spermine N(1)-acetyltransferase. The most interesting effect of hydroxylating CPMENSPM is the profound reduction in toxicity compared with that of the parent drug. The same phenomenon had been observed for the DENSPM/(2R,10R)-(HO)(2)DENSPM pair. Thus, hydroxylation of norspermine analogues appears to be a way to maintain the compounds' antiproliferative activity while reducing their toxicity.

In vitro gene transfer with a novel galactosylated spermine bolaamphiphile

We describe the synthesis of a alpha-galacto-omega-spermine bolaamphiphile (GalSper) and report on the gene transfer mediated with lipoplexes it forms either when used alone or in conjunction with DOPE or with DOGS (Transfectam). Lipofection with GalSper was investigated with human HepG2 or murine BNL-CL2 hepatocytes expressing the asialo-glycoprotein (ASGP) receptor, which displays a high affinity for galactosyl residues, or with A549 cells which do not express ASGP. Although lower luciferase expression levels in BNL-CL2 and in HepG2 cells were obtained with GalSper/DOPE N/P 2.5 lipoplexes as compared with control DOGS/DOPE N/P 2.5 particles or with the more positively charged N/P 5 particles (yet through a different mechanism), specific receptor-mediated endocytosis of DNA can be achieved with this targeted cationic GalSper bolaamphiphile presenting a single galactose residue. The present work suggests that GalSper-based DNA formulations appear as promising synthetic vectors for specific gene delivery to ASGP(+) cells.

Synthesis and transfecting properties of a glycosylated polycationic DNA vector

A glycosylated analogue of dialkylamidoglycylcarboxyspermine was synthesized. The physico-chemical and transfecting properties of 11 were evaluated indicating that this cationic lipid forms stable particles at low charge ratio and is efficient for gene delivery.

cis-Unsaturated analogues of 3,8,13,18,23-pentaazapentacosane (BE-4-4-4-4): synthesis and growth inhibitory effects on human prostate cancer cell lines

From the results of our previous physicochemical studies of polyamine-nucleic acid interactions, we concluded that polyamine analogues in cisoidal conformation are capable of wrapping around the major groove of the double helix, of displacing natural polyamines from their nucleic acid binding sites, and of inhibiting cell division. On the basis of this hypothesis, nine unsaturated pentamines, formally derived from the cytotoxic pentamine 3,8,13,18,23-pentaazapentacosane (BE-4-4-4-4), were prepared in an attempt to increase antineoplastic activity. Cis-double bonds were introduced in all possible sites in the saturated pentaazapentacosane structure of BE-4-4-4-4 to yield two pentacosenes, four pentacosadienes, two pentacosatrienes, and one pentacosatetraene. Cis-double bonds should also provide good targets for mixed-function oxidases that might eliminate the accumulation of unsaturated pentamines in serum, thereby reducing systemic toxicity in animals. We determined the ability of these new pentamines to inhibit growth in four cultured human prostate cancer cell lines (LnCap, DU145, PC-3, and DuPro) using a MTT assay. LnCap and DU145 cells were very sensitive, PC-3 cells were relatively resistant, and DuPro cells were intermediate in sensitivity to most of these synthetic pentamines. In all cell lines, pentamines that had unsaturation(s) at the end of the chain showed the highest cell growth inhibitory effects. The cellular uptake, effects on cellular polyamine levels, and cytotoxicity of these pentamines on one representative prostate cancer cell line (DuPro) were further examined with a colony-forming efficiency (CFE) assay. The pentamines with unsaturation(s) at the end of the chain were once again the most cytotoxic among both the saturated (BE-4-4-4-4) and unsaturated analogues. Appreciable amounts of all pentamines entered DuPro cells and depleted cellular polyamine pools by day 6 of treatment. For most pentamines, however, cell growth inhibitory and cytotoxic effects could not be directly correlated either with their cellular uptake or with their ability to deplete cellular polyamine pools. The position of the double bonds in the aliphatic backbone seems to be the most important determinant of cytotoxicity. For some pentamines, however, depletion of cellular polyamines may add to their efficacy.

Conformationally restricted analogues of 1N,14N-bisethylhomospermine (BE-4-4-4): synthesis and growth inhibitory effects on human prostate cancer cells

Twelve analogues of 1N,14N-bisethylhomospermine (BE-4-4-4) with restricted conformations were synthesized in the search for cancer chemotherapeutic agents with higher cytotoxic activities and lower systemic toxicities than BE-4-4-4. The central butane segment of BE-4-4-4 was replaced with a 1,2-substituted cyclopropane ring, a 1,2-substituted cyclobutane ring, and a 2-butene residue. In each case, the cis/trans-isomeric pair was synthesized. Cis-monounsaturation(s) was also introduced at the outer butane segment(s) of BE-4-4-4. The two possible cis-dienes and a cis-triene formally derived from the tetraazaeicosane skeleton of BE-4-4-4 were also prepared. Four cultured human prostate cancer cell lines (LnCap, DU145, DuPro, and PC-3) were treated with the new tetramines to examine their effects on cell growth with a MTT assay. One representative cell line (DuPro) was selected to further study the cellular uptake of the novel tetramines, their effects on intracellular polyamine pools, and their cytotoxicity. All tetramines entered the cells, reduced cellular putrescine and spermidine pools while exerting only a small effect on the spermine pool, inhibited cell growth, and killed 2-3 logs of cells after 6 days of treatment at 10 microM. Four new tetramines, the two cyclopropyl isomers, the trans-cyclobutyl isomer, and the (5Z)-tetraazaeicosene, were more cytotoxic than their saturated counterpart (BE-4-4-4). Their cytotoxicity, however, could not be correlated either with their cellular uptake or with their ability to deplete intracellular polyamine pools. We attribute their cytotoxicity to their specific molecular structures. The cytotoxicity was markedly reduced when the central butane segment was deprived of its rotational freedom by replacing it with a double bond. Introduction of a triple bond or a benzene-1,2-dimethyl residue at the central segment of the polyamine chain, led to complete loss of biological activity. The conformationally restricted alicyclic derivatives were not only more cytotoxic than was the freely rotating BE-4-4-4 by several orders of magnitude but also had much lower systemic toxicities than the latter. Thus, we obtained new tetramines with a wider therapeutic window than BE-4-4-4.

Polyamine analogue antidiarrheals: a structure-activity study

The syntheses of a group of spermine polyamine analogues and their evaluation as antidiarrheals are described. Each compound was assessed in a rodent castor oil-induced diarrhea model for its ability to reduce stool output and weight loss in a dose-dependent manner. The spermine pharmacophore is shown to be an excellent platform from which to construct antidiarrheals. The activity of the compounds is very dependent on both the nature of the terminal alkyl groups and the geometry of the methylene spacers separating the nitrogens. The toxicity profile is also quite dependent on these same structural features. On the basis of subcutaneous dose-response data and toxicity profiles, two compounds, N(1),N(12)-diisopropylspermine and N(1),N(12)-diethylspermine, were taken forward into more complete evaluation. These measurements included formal acute and chronic toxicity trials, drug and metabolic tissue distribution studies, and assessment of the impact of these analogues on tissue polyamine pools. Finally, the remarkable activity of N,N'-bis[3-(ethylamino)propyl]-trans-1,4-cyclohexanediamine underscores the need to further explore this framework as a pharmacophore for the construction of other antidiarrheal agents.

Pyrrolidyl polyamines: branched, chiral polyamine analogues that stabilize DNA duplexes and triplexes

[figure: see text] Pyrrolidyl polyamines (III-VI) are conformationally restricted, chiral analogues of linear spermine elaborated by the addition of aminopropyl chains to yield branched diastereomers. It is demonstrated that in concentrations as low as 0.01 mM, these compounds remarkably stabilize DNA duplexes and triplexes through strong electrostatic interactions. The synthesized compounds are potential dendrons with a chiral pyrrolidine core, and such molecules may have potential as DNA delivery and transfection agents.

Highly fluorinated lipospermines for gene transfer: synthesis and evaluation of their in vitro transfection efficiency

Fluorinated double-chain lipospermines (one or both of these chains being ended by a highly fluorinated tail of various length) which are close analogues of DOGS (Transfectam) were designed as synthetic vectors for gene delivery. For N/P ratios (N = number of amine functions of the lipid; P = number of DNA phosphates) from 0.8 to 10, these lipospermines condensed DNA, with or without the use of DOPE, to form fluorinated lipoplexes. The efficiency of the fluorinated lipoplexes to transfect lung epithelial A549 cells was significantly higher than that of the DOGS lipoplexes. No specific cell toxicity was evidenced for the fluorinated lipoplexes as compared to that of the DOGS ones. The palette of structural elements explored allowed to determine those required for efficient transfection, highlighting the importance of highly fluorinated chains, the unique properties of unsaturated double-chain lipids and of the use of DOPE as helper lipid on transfection.

Novel lysine-spermine conjugate inhibits polyamine transport and inhibits cell growth when given with DFMO

Polyamines are ubiquitous molecules with multiple intracellular functions. Cells tightly regulate their levels through feedback mechanisms affecting synthesis, intracellular conversion, and transport. Because polyamines have an important role in regulating cell growth, they are a target for cancer therapeutic development. However, to effectively inhibit cell growth through polyamine depletion one needs to inhibit both polyamine synthesis and import. Although the mammalian polyamine transporter has not been cloned, we have identified ORI 1202, an N(1)-spermine-L-lysinyl amide, as an effective polyamine transport inhibitor. ORI 1202 prevents the cellular accumulation of [(3)H]spermidine over a 20-h test period. ORI 1202 (30-100 microM) effectively inhibits cell growth when used in conjunction with the polyamine synthesis inhibitor alpha-difluoromethylornithine (DFMO; > or =230 microM). Human breast, prostate, and bladder carcinoma cell lines and melanoma cell lines show ORI 1202 EC(50) values in the low micromolar range when tested in conjunction with DFMO. This cytostatic effect correlates with a reduction in the intracellular levels of putrescine and spermidine. When ORI 1202 (45 mg/kg, i.p., tidx5) and DFMO (1% in drinking water) were delivered over 14 days, MDA-MB-231 breast tumor xenografts in nude mice showed 50% growth inhibition. Polyamine depletion therapy provides a cytostatic therapy that could be useful against cancer and other diseases resulting from uncontrolled cell growth.

Organometallic photonucleases: synthesis and DNA-cleavage studies of cyclopentadienyl metal-substituted dendrimers designed to increase double-strand scission

[reaction: see text] A series of metal complex-substituted polyamine dendrimers have been synthesized and examined for their ability to cleave plasmid DNA in a double-stranded manner. While photolysis of the dimetallic spermine derivative and the tetrametallic DAB-Am-4 complex led to double-strand scission, in the larger DAB-Am-8 and DAB-Am-16 systems, DNA aggregation/precipitation was the predominant competing process observed.

The synthesis and in vitro cytotoxic studies of novel bis-naphthalimidopropyl polyamine derivatives

Bis-naphthalimidopropyl putrescine (BNIPPut), spermidine (BNIPSpd), spermine (BNIPSpm) and oxa-putrescine (BNIPOPut) were synthesised and their growth-inhibitory properties characterised. All these compounds except for BNIPOPut, showed high in vitro cytotoxic activity (with mean GI50 values between 0.5 and 8.45 microM) and selectivity against cancer cells derived from nine different human tumours. The increased content of nitrogen atoms in the linker chain of BNIPSpd and BNIPSpm significantly improved their aqueous dissolution properties with a marginal decrease in their cytotoxic activity.

Ionic and structural specificity effects of natural and synthetic polyamines on the aggregation and resolubilization of single-, double-, and triple-stranded DNA

DNA condensation, precipitation, and aggregation are related phenomena involving DNA-DNA interactions in the presence of multivalent cations, and studied for their potential implications in DNA packaging in the cell. Recent studies have shown that the condensation/aggregation is a prerequisite for the cellular uptake of DNA for gene therapy applications. To elucidate the ionic and structural factors involved in DNA aggregation, we studied the precipitation and resolubilization of high molecular weight and sonicated calf thymus DNA, two therapeutic oligonucleotides, and poly(dA).2Poly(dT) triplex DNA in the presence of the tetravalent polyamine spermine using a centrifugation assay, Tm measurements, and CD spectroscopy. The ability of spermine to provoke DNA precipitation was in the following order: triplex DNA > duplex DNA > single-stranded DNA. In contrast, their resolubilization at high polyamine concentrations followed a reverse order. The effective concentration of spermine to precipitate DNA increased with Na+ in the medium. Tm data indicated the DNA stabilizing effect of spermine even in the resolubilized state. CD spectroscopy revealed a series of sequential conformational alterations of duplex and triplex DNA, with the duplex form regaining the B-DNA conformation at high concentrations (approximately 200 mM) of spermine. The triplex DNA, however, remained in a Psi-DNA conformation in the resolubilized state. Chemical structural specificity effects were exerted by spermidine and spermine analogues in precipitating and resolubilizing sonicated calf thymus DNA, with N4-methyl substitution of spermidine and a heptamethylene separation of the imino groups of spermine having the maximal difference in the precipitating ability of the analogues compared to spermidine and spermine, respectively. Therapeutically important bis(ethyl) substitution reduced the precipitating ability of the analogues compared to spermine. The effect of the cationicity of polyamines was evident with the pentamines being much more efficacious than the tetramines and triamines. These results provide new insights into the mechanism of DNA precipitation by polyamines, and suggest the importance of polyamine structure in developing gene delivery vehicles for therapeutic applications.

Conformationally restricted analogues of 1N,12N-bisethylspermine: synthesis and growth inhibitory effects on human tumor cell lines

Eight analogues of 1N,12N-bisethylspermine (BES) with restricted conformations were synthesized in the search for new spermine mimetics with cytotoxic activities. By replacing the central butane segment of BES with a 1,2-disubstituted cyclopropane ring, a pair of cis/trans-isomers was obtained that introduced a spatial constraint in the otherwise freely mobile butane chain. An analogous pair of isomers was obtained when the butane segment was replaced with a 1, 2-disubstituted cyclobutane ring or with a 2-butene residue. The six new BES analogues thus obtained (three pairs of cis/trans-isomers) were growth inhibitory at low-micromolar concentrations against four human tumor cell lines (A549, HT-29, U251MG, and DU145) but were less growth inhibitory against two other human tumor cell lines (PC-3 and MCF7). 1N,12N-Bisethylspermyne, where the central butane segment of BES was replaced by the rigid 2-butyne segment, was devoid of growth inhibitory activity against five of the six human cell lines studied (DU145 being the only exception), a clear indication of the importance of conformational mobility at the 4N, 9N-butane segment of BES for its biological activity. When the butane segment was replaced by a benzene-1,2-dimethyl residue, the resulting BES analogue was devoid of growth inhibitory activity despite its cisoid conformation. The cytotoxicity of the analogues does not seem to be directly related to their uptake by the cells or to their effects on cellular polyamine levels. BES analogues with restricted conformations but which contained the equivalent of a two-carbon unit, rather than the natural four-carbon unit, at the central segment, such as 1,2-diaminocyclopropyl or 1, 2-diaminocyclobutyl derivatives, were devoid of growth inhibitory effects at the concentrations studied. The development of conformationally restricted polyamine analogues appears to show promise in the further quest for polyamine-related therapeutic agents with specificity of action.

Spermine conjugated peptide nucleic acids (spPNA): UV and fluorescence studies of PNA-DNA hybrids with improved stability

Peptide Nucleic Acids (PNAs), the achiral DNA mimics with amide backbone, are emerging as attractive leads for drug development by antisense approach. Two major limitations of PNAs from an application perspective are their limited solubility in aqueous systems and pronounced self-organization. In this paper, it is shown that covalent conjugation of spermine at C-terminus of PNA (spPNA) improves its solubility and binds to complementary DNA 20 times stronger than the corresponding binding of PNA. Fluorescence kinetics shows a 2 fold acceleration of the bimolecular association process in spPNA:DNA hybrids, due to electrostatic interaction cationic spermine tagged to PNA with anionic DNA. This modification is easy to incorporate into PNA synthetic protocols to make them more effective in biological applications and may improve the poor cell uptake of PNA.

Boron-containing polyamines as DNA targeting agents for neutron capture therapy of brain tumors: synthesis and biological evaluation

Three series of new boron-containing spermidine/spermine (SPD/SPM) analogues have been synthesized: N1- and N5-(4-carboranylbutyl) SPD/SPM derivatives (SPD-1, SPD-5, SPM-1, SPM-5); N1,N10-diethyl-N5-(4-carboranylbutyl)spermidine (DESPD-5), N1,N14-diethyl-N5-(4-carboranylbutyl)spermine (DESPM-5); and N5,N10-bis(4-carboranylbutyl)spermine (SPM-5,10). In vitro studies using rat F98 glioma cells have shown that these polyamines retain the ability to displace ethidium bromide from calf thymus DNA and are rapidly taken up by F98 glioma cells. However, their cytotoxicities, especially those with terminal N-substituted (SPD-1, SPM-1) boron compounds, are greater than those of SPD/SPM. Nevertheless, the groundwork has been created for a new class of boron-containing compounds that maybe useful for boron neutron capture therapy of tumors.

New spermine and spermidine derivatives as potent inhibitors of Trypanosoma cruzi trypanothione reductase

Several spermine and spermidine derivatives containing 2-amino diphenylsulfide substituents were prepared and tested for their inhibiting effects on Trypanosoma cruzi trypanothione reductase. IC50 values were assessed between 0.3 and 3 microM. Compound 32 (Ki = 0.4 microM) is the most potent TR inhibitor described so far.

2,2'-Dithiobis(N-ethyl-spermine-5-carboxamide) is a high affinity, membrane-impermeant antagonist of the mammalian polyamine transport system

We have synthesized 2,2'-dithiobis(N-ethyl-spermine-5-carboxamide) (DESC), its thiol monomer (MESC), and the mixed MESC-cysteamine disulfide (DEASC) as potential inhibitors of polyamine transport in mammalian cells. DESC was the most potent antagonist of spermine transport in ZR-75-1 human breast cancer cells, with Ki values of 5. 0 +/- 0.7, 80 +/- 31, and 16 +/- 3 microM for DESC, MESC, and DEASC, respectively. DESC also strongly blocked putrescine and spermidine uptake in ZR-75-1 cells (Ki = 1.6 +/- 0.5 and 2.7 +/- 1.1 microM, respectively). While DESC and MESC were purely competitive inhibitors of putrescine transport, DEASC was a mixed competitive/noncompetitive antagonist. Remarkably, DESC was virtually impermeant in ZR-75-1 cells despite its low Ki toward polyamine transport. The marked difference in affinity between DESC and MESC was essentially due to the tail-to-tail juxtaposition of two spermine-like structures, suggesting that dimeric ligands of the polyamine transporter might simultaneously interact with more than one binding site. While DESC strongly decreased the initial rate of [3H]spermidine transport, even a 40-fold molar excess of antagonist could not completely abolish intracellular spermidine accumulation. Moreover, as little as 0.3 microM spermidine fully restored growth in ZR-75-1 cells treated with an inhibitor of polyamine biosynthesis in the presence of 50 microM DESC, thus emphasizing the importance of uptake of trace amounts of exogenous polyamines. Thus, reducing the exogenous supply of polyamines with a potent competitive inhibitor may be kinetically inadequate to block replenishment of the polyamine pool in polyamine-depleted tumor cells that display high transport capacity. These results demonstrate that polyamine analogues cross-linked into a dimeric structure such as DESC interact with high affinity with the mammalian polyamine carrier without being used as substrates. These novel properties provide a framework for the design of specific irreversible inhibitors of the polyamine transporter, which should present advantages over competitive antagonists for an efficient blockade of polyamine transport in tumor cells.