Targeting polyamine metabolism: a viable therapeutic/preventative solution for cancer?

Metabolic support by macrophages sustains colonic epithelial homeostasis

The intestinal epithelium has a high turnover rate and constantly renews itself through proliferation of intestinal crypt cells, which depends on insufficiently characterized signals from the microenvironment. Here, we showed that colonic macrophages were located directly adjacent to epithelial crypt cells in mice, where they metabolically supported epithelial cell proliferation in an mTORC1-dependent manner. Specifically, deletion of tuberous sclerosis complex 2 (Tsc2) in macrophages activated mTORC1 signaling that protected against colitis-induced intestinal damage and induced the synthesis of the polyamines spermidine and spermine. Epithelial cells ingested these polyamines and rewired their cellular metabolism to optimize proliferation and defense. Notably, spermine directly stimulated proliferation of colon epithelial cells and colon organoids. Genetic interference with polyamine production in macrophages altered global polyamine levels in the colon and modified epithelial cell proliferation. Our results suggest that macrophages act as "commensals" that provide metabolic support to promote efficient self-renewal of the colon epithelium.

Characterization of nanoparticles combining polyamine detection with photodynamic therapy

Polyamine detection and depletion have been extensively investigated for cancer prevention and treatment. However, the therapeutic efficacy is far from satisfactory, mainly due to a polyamine compensation mechanism from the systemic circulation in the tumor environment. Herein, we explore a new solution for improving polyamine detection as well as a possible consumption therapy based on a new photosensitizer that can efficiently consume polyamines via an irreversible chemical reaction. The new photosensitizer is pyrrolopyrroleaza-BODIPY pyridinium salt (PPAB-PyS) nanoparticles that can react with the over-expressed polyamine in cancer cells and produce two photosensitizers with enhanced phototoxicity on cancer destruction. Meanwhile, PPAB-PyS nanoparticles provide a simultaneous ratiometric fluorescence imaging of intracellular polyamine. This combination polyamine consumption with a chemical reaction provides a new modality to enable polyamine detection along with photodynamic therapy as well as a putative depletion of polyamines for cancer treatment and prevention.

Use of amantadine as substrate for SSAT-1 activity as a reliable clinical diagnostic assay for breast and lung cancer

Aim:

Spermidine/spermine N¹-acetyltransferase (SSAT-1) plays a critical role in cell growth, proliferation and death, and is known to be activated in human cancer cells. Amantadine, a US FDA-approved antiviral drug, is a substrate for SSAT-1 and can be used to indirectly measure SSAT-1 activity because of its conversion to acetylamantadine (AA). This study was undertaken to further validate SSAT-1 activity in breast and lung cancer patients.

Results:

An increase in the urinary concentration of AA in lung and breast cancer patients was observed. The 0–2 h collection time point was determined to be optimal in revealing significant differences in urinary AA concentration between healthy controls and cancer patients.

Conclusion:

The high urine concentration of AA could be used as a simple and useful test for the detection of breast and lung cancer.

This study describes a novel noninvasive urine test for detecting and screening of breast and lung cancer using a safe and approved drug called amantadine. Higher concentration of the acetylated form of amantadine in the urine are detectable in the urine of both breast and lung cancer patients as compared with healthy adult volunteers. This test is simple and may serve as a useful tool for determining the presence of breast and lung cancer.

Polyamine synthesis as a target of MYC oncogenes

This paper is in recognition of the 100th birthday of Dr. Herbert Tabor, a true pioneer in the polyamine field for over 70 years, who served as the editor-in-chief of the Journal of Biological Chemistry from 1971 to 2010. We review current knowledge of MYC proteins (c-MYC, MYCN, and MYCL) and focus on ornithine decarboxylase 1 (ODC1), an important bona fide gene target of MYC, which encodes the sentinel, rate-limiting enzyme in polyamine biosynthesis. Although notable advances have been made in designing inhibitors against the "undruggable" MYCs, their downstream targets and pathways are currently the main avenue for therapeutic anticancer interventions. To this end, the MYC-ODC axis presents an attractive target for managing cancers such as neuroblastoma, a pediatric malignancy in which MYCN gene amplification correlates with poor prognosis and high-risk disease. ODC and polyamine levels are often up-regulated and contribute to tumor hyperproliferation, especially of MYC-driven cancers. We therefore had proposed to repurpose α-difluoromethylornithine (DFMO), an FDA-approved, orally available ODC inhibitor, for management of neuroblastoma, and this intervention is now being pursued in several clinical trials. We discuss the regulation of ODC and polyamines, which besides their well-known interactions with DNA and tRNA/rRNA, are involved in regulating RNA transcription and translation, ribosome function, proteasomal degradation, the circadian clock, and immunity, events that are also controlled by MYC proteins.

[Enantioselective Synthesis of (R)- and (S)-3-Methylspermidines]

Earlier unknown enantiomerically pure (R)- and (S)-1,8-diamino-3-methyl-4-azaoctane's (3-MeSpd's) were synthesized with high overall yields and optical purity starting from commercially available R- and S-isomers of N-Boc-2-aminopropanol-1. Application of R- and S-isomers of 3-MeSpd for the investigation of the stereospecificity of spermidine transporter and peculiarities of deoxyhypusine synthase reaction are discussed.

The antitumor effects of geraniol: Modulation of cancer hallmark pathways (Review)

Geraniol is a dietary monoterpene alcohol that is found in the essential oils of aromatic plants. To date, experimental evidence supports the therapeutic or preventive effects of geraniol on different types of cancer, such as breast, lung, colon, prostate, pancreatic, and hepatic cancer, and has revealed the mechanistic basis for its pharmacological actions. In addition, geraniol sensitizes tumor cells to commonly used chemotherapy agents. Geraniol controls a variety of signaling molecules and pathways that represent tumor hallmarks; these actions of geraniol constrain the ability of tumor cells to acquire adaptive resistance against anticancer drugs. In the present review, we emphasize that geraniol is a promising compound or chemical moiety for the development of a safe and effective multi-targeted anticancer agent. We summarize the current knowledge of the effects of geraniol on target molecules and pathways in cancer cells. Our review provides novel insight into the challenges and perspectives with regard to geraniol research and to its application in future clinical investigation.

Hydroxylamine derivatives for regulation of spermine and spermidine metabolism

The biogenic polyamines spermine, spermidine, and their precursor putrescine are present in micro-to-millimolar concentrations in all cell types and are vitally important for their normal growth. High intracellular content of spermine and spermidine determines the multiplicity of the cellular functions of the polyamines. Many of these functions are not well characterized at the molecular level, ensuring the ongoing development of this field of biochemistry. Tumor cells have elevated polyamine level if compared with normal cells, and this greatly stimulates the search for new opportunities to deplete the intracellular pool of spermine and spermidine resulting in decrease in cell growth and even cell death. O-Substituted hydroxylamines occupy their own place among chemical regulators of the activity of the enzymes of polyamine metabolism. Varying the structure of the alkyl substituent made it possible to obtain within one class of chemical compounds highly effective inhibitors and regulators of the activity of all the enzymes of putrescine, spermine and spermidine metabolism (with the exception of FAD-dependent spermine oxidase and acetylpolyamine oxidase), effectors of the polyamine transport system, and even actively transported in cells "proinhibitor" of ornithine decarboxylase. Some principles for the design of specific inhibitors of these enzymes as well as the peculiarities of cellular effects of corresponding O-substituted hydroxylamines are discussed.

Dynamics of arginase gene evolution in metazoans

In the present study, a comprehensive analysis of the arginase gene family in metazoans was performed. A total of 126 arginase genes have been identified in 44 species. Phylogenetic analyses indicate that arginase genes consist of four groups. Conservative and divergent gene structures are found among the groups. The syntenies also exist in distantly related genomes among multiple species. Adaptive evolution shows that, while purifying selection may have been the main force driving the evolution of the arginases, some of critical sites responsible for the functional divergence may have been under positive selection. Overall, the data obtained from our investigation contribute to a better understanding of the complexity of the arginase gene family and of the function and evolution of this family in metazoans.

A central role for polyamines in microtubule assembly in cells

Owing to preferential electrostatic adsorption of multivalent cations on highly anionic surfaces, natural multivalent polyamines and especially quadrivalent spermine can be considered as potential regulators of the complex dynamical properties of anionic MTs (microtubules). Indeed, the C-terminal tails of tubulin display many negative residues in a row which should enable the formation of a correlated liquid-like phase of multivalent counterions on its surface. Although it is known that polyamine counterions promote MT assembly in vitro, little is known about the relevance of this interaction in vivo. In the present study, we have explored the relationship between polyamine levels and MT assembly in HeLa and epithelial NRK (normal rat kidney) cells using DFMO (α-difluoromethylornithine), an irreversible inhibitor of ornithine decarboxylase, and APCHA [N-(3-aminopropyl)-N-cyclohexylamine], a spermine synthase inhibitor. Under conditions of intracellular polyamine depletion, the MT network is clearly disrupted and the MT mass decreases. Addition of spermine to polyamine-depleted cells reverses this phenotype and rapidly promotes the extensions of the MT network. Finally, we show that polyamine levels modulate the coating of MTs with MAP4 (MT-associated protein 4), an MT-stabilizing protein, and the spatial distribution of EB1 (end-binding protein 1), an MT plus-end-binding protein. In addition, polyamines favour the formation of gap junctions in NRK cells, a process which requires MT extensions at the cell periphery. The present study provides a basis for a better understanding of the role played by polyamines in MT assembly and establishes polyamine metabolism as a potential cellular target for modulating MT functions.

Metabolic signatures of malignant progression in prostate epithelial cells

Prognostic markers that can distinguish indolent from aggressive prostate cancer could have substantial patient benefit, helping to target patients most in need of radical intervention, while avoiding overtreatment of a highly prevalent condition. The search for novel cancer biomarkers has been facilitated by the development of technologies for "global" biomolecular profiling, used in the sciences of transcriptomics, proteomics and metabolic profiling (metabonomics/metabolomics). Using an NMR-based approach we compared intracellular and extracellular metabolic profiles from the immortalised, non-tumourigenic prostate epithelial cell line, RWPE-1 and two tumourigenic sublines with increasing malignant phenotypes, WPE1-NB14 and WPE1-NB11, generated by N-methyl-N-nitrosourea (MNU) mutagenesis. Collectively, these cell lines present an in vitro model of prostate cancer progression and disease aggression. We observed progressive alterations to intracellular levels of multiple metabolites from choline and branched chain amino acid metabolic pathways from RWPE-1 to WPE1-NB14 to WPE1-NB11 cells. In addition specific perturbations to intracellular glycine and lactate and extracellular lactate and alanine were observed relative to the parent line. The pathways implicated by comparative metabolic profiling in this model are known to be altered in human prostate cancer, and potentially represent a source of biomarkers for prostate cancer aggression.

Polyamine metabolism in Leishmania: from arginine to trypanothione

Polyamines (PAs) are essential metabolites in eukaryotes, participating in a variety of proliferative processes, and in trypanosomatid protozoa play an additional role in the synthesis of the critical thiol trypanothione. The PAs are synthesized by a metabolic process which involves arginase (ARG), which catalyzes the enzymatic hydrolysis of L-arginine (L-Arg) to L-ornithine and urea, and ornithine decarboxylase (ODC), which catalyzes the enzymatic decarboxylation of L-ornithine in putrescine. The S-adenosylmethionine decarboxylase (AdoMetDC) catalyzes the irreversible decarboxylation of S-adenosylmethionine (AdoMet), generating the decarboxylated S-adenosylmethionine (dAdoMet), which is a substrate, together with putrescine, for spermidine synthase (SpdS). Leishmania parasites and all the other members of the trypanosomatid family depend on spermidine for growth and survival. They can synthesize PAs and polyamine precursors, and also scavenge them from the microenvironment, using specific transporters. In addition, Trypanosomatids have a unique thiol-based metabolism, in which trypanothione (N1-N8-bis(glutathionyl)spermidine, T(SH)(2)) and trypanothione reductase (TR) replace many of the antioxidant and metabolic functions of the glutathione/glutathione reductase (GR) and thioredoxin/thioredoxin reductase (TrxR) systems present in the host. Trypanothione synthetase (TryS) and TR are necessary for the protozoa survival. Consequently, enzymes involved in spermidine synthesis and its utilization, i.e. ARG, ODC, AdoMetDC, SpdS and, in particular, TryS and TR, are promising targets for drug development.

TRPV1: on the road to pain relief

Historically, drug research targeted to pain treatment has focused on trying to prevent the propagation of action potentials in the periphery from reaching the brain rather than pinpointing the molecular basis underlying the initial detection of the nociceptive stimulus: the receptor itself. This has now changed, given that many receptors of nociceptive stimuli have been identified and/or cloned. Transient Receptor Potential (TRP) channels have been implicated in several physiological processes such as mechanical, chemical and thermal stimuli detection. Ten years after the cloning of TRPV1, compelling data has been gathered on the role of this channel in inflammatory and neuropathic states. TRPV1 activation in nociceptive neurons, where it is normally expressed, triggers the release of neuropeptides and transmitters resulting in the generation of action potentials that will be sent to higher CNS areas where they will often be perceived as pain. Its activation also will evoke the peripheral release of pro-inflammatory compounds that may sensitize other neurons to physical, thermal or chemical stimuli. For these reasons as well as because its continuous activation causes analgesia, TRPV1 has become a viable drug target for clinical use in the management of pain. This review will provide a general picture of the physiological and pathophysiological roles of the TRPV1 channel and of its structural, pharmacological and biophysical properties. Finally, it will provide the reader with an overall view of the status of the discovery of potential therapeutic agents for the management of chronic and neuropathic pain.

Micronutrients and amino acids, main regulators of physiological processes

Human physiology is supposed to be a complex interaction of regulating processes, in which hormones, genes, their proteins and apoptosis are thought to play a dominant role. We hypothesize that regulation of physiological processes is mainly influenced by amino acids and micronutrients with hormones, proteins, apoptosis and gene modifications being their derivatives. Furthermore, we suppose that the cells power plant, the mitochondrion, is in fact an intracellular bacterium, living in absolute symbiosis. Because of its intracellular existence it depends on the host's micronutrients completely. Within the host these micronutrients regulate their own formation, degradation, uptake and excretion. Known deficiencies, such as iodine and vitamin D, affect billions of people. Many micronutrients neither have been investigated, nor have they been studied in relation to each other and solid data are not available. Optimal levels of many micronutrients and all amino acids are not known. Amino acids, vitamins and minerals are capable of altering gene expression, inducing apoptosis and regulating chemical processes. It makes them highly attractive for creating better health, against low cost, as we have already proven in the case of rickets, cretinism and scurvy in severe deficiencies. By creating optimal living conditions and study mitochondria from a symbiotic point of view we suppose that diseases not only can be prevented, but the course of diseases can be altered as well.

The activity of Plasmodium falciparum arginase is mediated by a novel inter-monomer salt-bridge between Glu295-Arg404

A recent study implicated a role for Plasmodium falciparum arginase in the systemic depletion of arginine levels, which in turn has been associated with human cerebral malaria pathogenesis. Arginase (EC 3.5.3.1) is a multimeric metallo-protein that catalyses the hydrolysis of arginine to ornithine and urea by means of a binuclear spin-coupled Mn(2+) cluster in the active site. A previous report indicated that P. falciparum arginase has a strong dependency between trimer formation, enzyme activity and metal co-ordination. Mutations that abolished Mn(2+) binding also caused dissociation of the trimer; conversely, mutations that abolished trimer formation resulted in inactive monomers. By contrast, the monomers of mammalian (and therefore host) arginase are also active. P. falciparum arginase thus appears to be an obligate trimer and interfering with trimer formation may therefore serve as an alternative route to enzyme inhibition. In the present study, the mechanism of the metal dependency was explored by means of homology modelling and molecular dynamics. When the active site metals are removed, loss of structural integrity is observed. This is reflected by a larger equilibration rmsd for the protein when the active site metal is removed and some loss of secondary structure. Furthermore, modelling revealed the existence of a novel inter-monomer salt-bridge between Glu295 and Arg404, which was shown to be associated with the metal dependency. Mutational studies not only confirmed the importance of this salt-bridge in trimer formation, but also provided evidence for the independence of P. falciparum arginase activity on trimer formation.

Antitumor activity of new substituted 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones: selectivity against colon tumor cells and effect on cell cycle-related events

The synthesis of new 3-(5-imidazo[2,1-b]thiazolylmethylene)-2-indolinones and 3-(5-imidazo[2,1-b]thiadiazolylmethylene)-2-indolinones is reported. The antitumor activity was evaluated according to the protocols available at the National Cancer Institute (NCI), Bethesda, MD. To investigate the mechanism of action of the most potent antitumor agent of this series, its effect on growth of HT-29 colon carcinoma cells was studied. Its ability to inhibit cellular proliferation was mediated by cell cycle arrest at the G2/M phase, accompanied by inhibition of ornithine decarboxylase (ODC), the limiting enzyme of polyamine synthesis, and followed by induction of apoptosis.