Ornithine decarboxylase activity is critical for cell transformation

Polyamine depletion limits progression of acute leukaemia

Cancer cells are addicted to polyamines, polycations essential for cellular function. While dual targeting of cellular polyamine biosynthesis and polyamine uptake is under clinical investigation in solid cancers, preclinical and clinical studies into its potential in haematological malignancies are lacking. Here we investigated the preclinical efficacy of polyamine depletion in acute leukaemia. The polyamine biosynthesis inhibitor difluoromethylornithine (DFMO) inhibited growth of a molecularly diverse panel of acute leukaemia cell lines, while non-malignant cells were unaffected. Responsiveness to DFMO was linked to decreased levels of its molecular target, the rate-limiting polyamine biosynthesis enzyme ODC1, and of the polyamine transporters ATP13A2 and ATP13A3. DFMO increased polyamine uptake and upregulated expression of polyamine transporters in acute leukaemia cells, a compensatory effect abolished by treatment with the polyamine transport inhibitor AMXT 1501. This drug, currently in a phase 1 clinical trial in solid tumours in combination with DFMO, potentiated the inhibitory effects of DFMO, and their combination synergistically inhibited the growth of acute leukaemia cell lines by inducing apoptosis. DFMO and AMXT 1501 limited disease progression in highly aggressive xenograft models of infant KMT2A-rearranged leukaemia, even when treatment was initiated at high disease burden. Increased expression of c-MYC was associated with enhanced sensitivity to the combination of DFMO and AMXT 1501, suggesting this oncoprotein as a potential predictive marker of response to the drug combination. In conclusion, targeting polyamine biosynthesis and polyamine uptake limits disease progression in models of acute leukaemia, supporting further preclinical and clinical investigation into this approach for acute leukaemia.

Polyamine Inhibition with DFMO: Shifting the Paradigm in Neuroblastoma Therapy

Neuroblastoma is a common childhood malignancy, and high-risk presentations, including an MYCN amplified status, continue to result in poor survival. Difluoromethylornithine (DFMO) is a new and well-tolerated treatment for high-risk neuroblastoma. This review article discusses preclinical and clinical data that resulted in the establishment of DFMO as a treatment for neuroblastoma. The review of preclinical data includes a summary of the contribution of polyamine synthetic pathways to high-risk neuroblastoma, the effect that MYCN has on polyamine synthetic pathways, and the proposed mechanism by which DFMO inhibits tumorigenesis. This understanding has led to the discussion of various preclinical combination therapies that may result in a synergistic therapeutic response for high-risk neuroblastoma. We review the clinical trials that show the successful treatment of high-risk neuroblastoma with DFMO, including comparative analysis and traditional neuroblastoma trials using propensity score matching. We review the regulatory path by which DFMO gained approval from the Federal Drug Administration for use as a maintenance therapy following the traditional high-risk neuroblastoma therapy. Finally, we discuss the role of DFMO in future clinical research for neuroblastoma and additional pediatric cancers.

Metabolic insights into tumor lymph node metastasis in melanoma

Although accounting for only a small amount of skin cancers, melanoma contributes prominently to skin cancer-related deaths, which are mostly caused by metastatic diseases, and lymphatic metastasis constitutes the main route. In this review, we concentrate on the metabolic mechanisms of tumor lymph node (LN) metastasis in melanoma. Two hypotheses of melanoma LN metastasis are introduced, which are the premetastatic niche (PMN) and parallel progression model. Dysregulation of oxidative stress, lactic acid concentration, fatty acid synthesis, amino acid metabolism, autophagy, and ferroptosis construct the metabolic mechanisms in LN metastasis of melanoma. Moreover, melanoma cells also promote LN metastasis by interacting with non-tumor cells through metabolic reprogramming in TIME. This review will deepen our understanding of the mechanism of lymph node metastasis in melanoma.

Protein degradation of antizyme depends on the N-terminal degrons

Antizyme (AZ) is a regulatory protein that plays a crucial role in modulating the activity of ornithine decarboxylase (ODC), which is the initial and rate-limiting enzyme in the complex pathway of polyamine biosynthesis. AZ facilitates the swift degradation of ODC, thereby modulating the levels of cellular polyamines. This study unveils a new ubiquitin-independent mechanism for AZ degradation, emphasizing the essential role of N-terminal degrons. Contrary to traditional ubiquitin-dependent degradation, our findings reveal that AZ degradation is significantly influenced by its N-terminal region. By conducting a series of experiments, including in vitro degradation assays, cycloheximide chase experiments, differential scanning calorimetry, and measurement of cellular concentrations of polyamines, we demonstrate that N-terminal truncation significantly enhances AZ's stability and facilitates the reduction of polyamine levels by accelerating ODC degradation. The removal of the N-terminal portion of AZ results in a reduced degradation rate and enhanced thermal stability of the protein, leading to a more efficient inhibition of polyamine synthesis. These findings are corroborated by the analysis of AZ isoforms, AZ1, AZ2, and AZ3, which display differential degradation patterns based on the specific N-terminal segments. This substantiates a degradation mechanism driven by an intrinsically disordered N-terminal region acting as a degron, independent of lysine ubiquitination. These results underscore the significant regulatory function of the N-terminal domain in the activity of AZ and the maintenance of polyamine homeostasis.

Spermine and spermidine inhibit or induce programmed cell death in Arabidopsis thaliana in vitro and in vivo in a dose-dependent manner

Polyamines are ubiquitous biomolecules with a number of established functions in eukaryotic cells. In plant cells, polyamines have previously been linked to abiotic and biotic stress tolerance, as well as to the modulation of programmed cell death (PCD), with contrasting reports on their pro-PCD and pro-survival effects. Here, we used two well-established platforms for the study of plant PCD, Arabidopsis thaliana suspension cultures cells and the root hair assay, to examine the roles of the polyamines spermine and spermidine in the regulation of PCD. Using these systems for precise quantification of cell death rates, we demonstrate that both polyamines can trigger PCD when applied exogenously at higher doses, whereas at lower concentrations they inhibit PCD induced by both biotic and abiotic stimuli. Furthermore, we show that concentrations of polyamines resulting in inhibition of PCD generated a transient ROS burst in our experimental system, and activated the expression of oxidative stress- and pathogen response-associated genes. Finally, we examined PCD responses in existing Arabidopsis polyamine synthesis mutants, and identified a subtle PCD phenotype in Arabidopsis seedlings deficient in thermo-spermine. The presented data show that polyamines can have a role in PCD regulation; however, that role is dose-dependent and consequently they may act as either inhibitors, or inducers, of PCD in Arabidopsis.

Preventing Cancer by Inhibiting Ornithine Decarboxylase: A Comparative Perspective on Synthetic vs. Natural Drugs

This perspective delves into the investigation of synthetic and naturally occurring inhibitors, their patterns of inhibition, and the effectiveness of newly utilized natural compounds as inhibitors targeting the Ornithine decarboxylase enzyme. This enzyme is known to target the MYC oncogene, thereby establishing a connection between polyamine metabolism and oncogenesis in both normal and cancerous cells. ODC activation and heightened polyamine activity are associated with tumor development in numerous cancers and fluctuations in ODC protein levels exert a profound influence on cellular activity for inhibition or suppressing tumor cells. This perspective outlines efforts to develop novel drugs, evaluate natural compounds, and identify promising inhibitors to address gaps in cancer prevention, highlighting the potential of newly designed synthetic moieties and natural flavonoids as alternatives. It also discusses natural compounds with potential as enhanced inhibitors.

Bachmann-Bupp syndrome and treatment

Bachmann-Bupp syndrome (BABS) is a neurodevelopmental disorder characterized by developmental delay, hypotonia, and varying forms of non-congenital alopecia. The condition is caused by 3'-end mutations of the ornithine decarboxylase 1 (ODC1) gene, which produce carboxy (C)-terminally truncated variants of ODC, a pyridoxal 5'-phosphate-dependent enzyme. C-terminal truncation of ODC prevents its ubiquitin-independent proteasomal degradation and leads to cellular accumulation of ODC enzyme that remains catalytically active. ODC is the first rate-limiting enzyme that converts ornithine to putrescine in the polyamine pathway. Polyamines (putrescine, spermidine, spermine) are aliphatic molecules found in all forms of life and are important during embryogenesis, organogenesis, and tumorigenesis. BABS is an ultra-rare condition with few reported cases, but it serves as a convincing example for drug repurposing therapy. α-Difluoromethylornithine (DFMO, also known as eflornithine) is an ODC inhibitor with a strong safety profile in pediatric use for neuroblastoma and other cancers as well as West African sleeping sickness (trypanosomiasis). Patients with BABS have been treated with DFMO and have shown improvement in hair growth, muscle tone, and development.

Polyamines: their significance for maintaining health and contributing to diseases

Polyamines are essential for the growth and proliferation of mammalian cells and are intimately involved in biological mechanisms such as DNA replication, RNA transcription, protein synthesis, and post-translational modification. These mechanisms regulate cellular proliferation, differentiation, programmed cell death, and the formation of tumors. Several studies have confirmed the positive effect of polyamines on the maintenance of health, while others have demonstrated that their activity may promote the occurrence and progression of diseases. This review examines a variety of topics, such as polyamine source and metabolism, including metabolism, transport, and the potential impact of polyamines on health and disease. In addition, a brief summary of the effects of oncogenes and signaling pathways on tumor polyamine metabolism is provided. Video Abstract.

The oncogenic properties of the EWSR1::CREM fusion gene are associated with polyamine metabolism

The EWSR1::CREM fusion gene, caused by a chromosomal translocation t(10;22)(p11;q12), has been discovered in divergent malignancies, ranging from low-grade to highly malignant cancers. The translocation gives rise to a chimeric protein, EWSR1::CREM. The molecular mechanisms behind the oncogenic properties of the EWSR1::CREM protein have not previously been systematically characterized. In this study, we performed transcriptional profiling of the melanoma cell line CHL-1, with depletion of endogenous EWSR1::CREM protein using siRNA mediated knockdown. We found that the expression of 712 genes was altered (Log2 fold-change ≥ 2). We performed pathway analysis to identify EWSR1::CREM mediated pathways and cell studies to examine functional differences brought upon by the knockdown. Altered pathways involved cell cycle and proliferation, this was further validated by the cell studies where cell migration was affected as well. Among the target genes with the greatest downregulation, we discovered ODC1-a well-established oncogenic enzyme that can be pharmacologically inhibited and is essential for polyamine synthesis. We found that the main effects seen upon EWSR1::CREM knockdown can be reproduced by directly silencing ODC1 expression. These findings provide novel insights into pathogenesis of tumors harboring a EWSR1::CREM fusion gene, hopefully facilitating the development of novel therapeutic strategies.

c-MYC-Driven Polyamine Metabolism in Ovarian Cancer: From Pathogenesis to Early Detection and Therapy

c-MYC and its paralogues MYCN and MYCL are among the most frequently amplified and/or overexpressed oncoproteins in ovarian cancer. c-MYC plays a key role in promoting ovarian cancer initiation and progression. The polyamine pathway is a bona fide target of c-MYC signaling, and polyamine metabolism is strongly intertwined with ovarian malignancy. Targeting of the polyamine pathway via small molecule inhibitors has garnered considerable attention as a therapeutic strategy for ovarian cancer. Herein, we discuss the involvement of c-MYC signaling and that of its paralogues in promoting ovarian cancer tumorigenesis. We highlight the potential of targeting c-MYC-driven polyamine metabolism for the treatment of ovarian cancers and the utility of polyamine signatures in biofluids for early detection applications.

L-norvaline affects the proliferation of breast cancer cells based on the microbiome and metabolome analysis

AIMS

The altered fecal metabolites and microbiota might be involved in the development of breast cancer. We aimed to investigate the effect of differential metabolites on the proliferative activity of breast cancer cells.

METHODS AND RESULTS

We collected fecal samples from 14 breast cancer patients and 14 healthy subjects. Untargeted metabolomics analysis, short-chain fatty acid (SCFA) targeted analysis, and 16S rDNA sequencing was performed. The gut metabolite composition of patients changed significantly. Levels of norvaline, glucuronate, and galacturonate were lower in the Cancer group than in the Control (p < 0.05). 4-Methylcatechol and guaiacol increased (p < 0.05). Acetic acid and butyric acid were lower in the Cancer group than in the Control group (p < 0.05). Isobutyric acid and pentanoic acid were higher in the Cancer group than in the Control (p < 0.05). In the genus, the abundance of Rothia and Actinomyces increased in the Cancer group, compared with the Control group (p < 0.05). The differential microbiotas were clearly associated with differential metabolites but weakly with SCFAs. The abundance of Rothia and Actinomyces was markedly positively correlated with 4-methylcatechol and guaiacol (p < 0.05) and negatively correlated with norvaline (p < 0.05). L-norvaline inhibited the content of Arg-1 in a concentration-dependent manner. Compared with the L-norvaline or doxorubicin hydrochloride (DOX) group, the proliferation abilities of 4T1 cells were the lowest in the L-norvaline combined with DOX (p < 0.05). The apoptosis rate increased (p < 0.05).

CONCLUSIONS

Fecal metabolites and microbiota were significantly altered in breast cancer. Levels of differential metabolites (i.e., Norvaline) were significantly correlated with the abundance of differential microbiota. L-norvaline combined with DOX could clearly inhibit the proliferation activity of breast cancer cells.

SIGNIFICANCE AND IMPACT OF STUDY

This might provide clues to uncover potential biomarkers for breast cancer diagnosis and treatment.

Structural Basis for Allostery in PLP-dependent Enzymes

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are found ubiquitously in nature and are involved in a variety of biological pathways, from natural product synthesis to amino acid and glucose metabolism. The first structure of a PLP-dependent enzyme was reported over 40 years ago, and since that time, there is a steady wealth of structural and functional information revealed for a wide array of these enzymes. A functional mechanism that is gaining more appreciation due to its relevance in drug design is that of protein allostery, where binding of a protein or ligand at a distal site influences the structure, organization, and function at the active site. Here, we present a review of current structure-based mechanisms of allostery for select members of each PLP-dependent enzyme family. Knowledge of these mechanisms may have a larger potential for identifying key similarities and differences among enzyme families that can eventually be exploited for therapeutic development.

CDC27-ODC1 Axis Promotes Metastasis, Accelerates Ferroptosis and Predicts Poor Prognosis in Neuroblastoma

Neuroblastoma (NB) is a devastating malignancy threatening children’s health, and amplification of MYCN is associated with treatment failure and a poor outcome. Here, we aimed to demonstrate the role of cell division cycle 27 (CDC27), an important core subunit of the anaphase-promoting complex, and its clinical significance in NB patients. In functional assays, we illustrated that CDC27 promoted the cell growth, metastasis and sphere-formation ability of NB cells both in vitro and in vivo. To further understand the potential mechanism, SK-N-SH cells were transfected with CDC27 siRNA, and RNA-sequencing was performed. The results revealed that downregulation of CDC27 led to markedly reduced expression of ODC1, which is a well-established direct target of MYCN. Subsequently, we further illustrated that suppression of ODC1 significantly attenuated the promotion effect of CDC27 on the proliferation, metastasis, and sphere-formation ability of NB cells, hinting that CDC27 exerted its biological behavior in NB at least partly in an ODC1-dependent manner. In addition, CDC27 rendered cells more vulnerable to ferroptosis, while knockdown of ODC1 markedly reversed the pro-ferroptotic effect of CDC27. Collectively, our data is the first to report that the CDC27/ODC1 axis promotes tumorigenesis and acts as a positive regulator of ferroptosis in NB, highlighting that CDC27 may represent a novel therapeutic strategy and prognostic biomarker in neuroblastoma.

Antitumor Effects of Natural Compounds Derived from Allium sativum on Neuroblastoma: An Overview

Garlic (Allium sativum) has been used in alternative medicine to treat several diseases, such as cardiovascular and neurodegenerative diseases, cancer, and hepatic diseases. Several publications have highlighted other features of garlic, including its antibacterial, antioxidative, antihypertensive, and antithrombotic properties. The properties of garlic result from the combination of natural compounds that act synergistically and cause different effects. Some garlic-derived compounds have been studied for the treatment of several types of cancer; however, reports on the effects of garlic on neuroblastoma are scarce. Neuroblastoma is a prevalent childhood tumor for which the search for therapeutic alternatives to improve treatment without affecting the patients’ quality of life continues. Garlic-derived compounds hold potential for the treatment of this type of cancer. A review of articles published to date on some garlic compounds and their effect on neuroblastoma was undertaken to comprehend the possible therapeutic role of these compounds. This review aimed to analyze the impact of some garlic compounds on cells derived from neuroblastoma.

Hyperglycemic conditions proliferate triple negative breast cancer cells: role of ornithine decarboxylase

PURPOSE

Several cancer subtypes (pancreatic, breast, liver, and colorectal) rapidly advance to higher aggressive stages in diabetes. Though hyperglycemia has been considered as a fuel for growth of cancer cells, pathways leading to this condition are still under investigation. Cellular polyamines can modulate normal and cancer cell growth, and inhibitors of polyamine synthesis have been approved for treating colon cancer, however the role of polyamines in diabetes-mediated cancer advancement is unclear as yet. We hypothesized that polyamine metabolic pathway is involved with increased proliferation of breast cancer cells under high glucose (HG) conditions.

METHODS

Studies were performed with varying concentrations of glucose (5-25 mM) exposure in invasive, triple negative breast cancer cells, MDA-MB-231; non-invasive, estrogen/progesterone receptor positive breast cancer cells, MCF-7; and non-tumorigenic mammary epithelial cells, MCF-10A.

RESULTS

There was a significant increase in proliferation with HG (25 mM) at 48-72 h in both MDA-MB-231 and MCF-10A cells but no such effect was observed in MCF-7 cells. This was correlated to higher activity of ornithine decarboxylase (ODC), a rate-limiting enzyme in polyamine synthesis pathway. Inhibitor of polyamine synthesis (difluoromethylornithine, DFMO, 5 mM) was quite effective in suppressing HG-mediated cell proliferation and ODC activity in MDA-MB-231 and MCF-10A cells. Polyamine (putrescine) levels were significantly elevated with HG treatment in MDA-MB-231 cells. HG exposure also increased the metastasis of MDA-MB-231 cells.

CONCLUSIONS

Our cellular findings indicate that polyamine inhibition should be explored in patient population as a target for future chemotherapeutics in diabetic breast cancer.

DDX3 depletion represses translation of mRNAs with complex 5' UTRs

DDX3 is an RNA chaperone of the DEAD-box family that regulates translation. Ded1, the yeast ortholog of DDX3, is a global regulator of translation, whereas DDX3 is thought to preferentially affect a subset of mRNAs. However, the set of mRNAs that are regulated by DDX3 are unknown, along with the relationship between DDX3 binding and activity. Here, we use ribosome profiling, RNA-seq, and PAR-CLIP to define the set of mRNAs that are regulated by DDX3 in human cells. We find that while DDX3 binds highly expressed mRNAs, depletion of DDX3 particularly affects the translation of a small subset of the transcriptome. We further find that DDX3 binds a site on helix 16 of the human ribosomal rRNA, placing it immediately adjacent to the mRNA entry channel. Translation changes caused by depleting DDX3 levels or expressing an inactive point mutation are different, consistent with different association of these genetic variant types with disease. Taken together, this work defines the subset of the transcriptome that is responsive to DDX3 inhibition, with relevance for basic biology and disease states where DDX3 is altered.

Antizyme inhibitor 2 (AZIN2) associates with better prognosis of head and neck minor salivary gland adenoid cystic carcinoma

The key regulator of the polyamine biosynthetic pathway is ornithine decarboxylase (ODC). ODC is activated by antizyme inhibitor 1 (AZIN1) and 2 (AZIN2). AZIN1 and recently AZIN2 have been related to cancer; however, their functions in adenoid cystic carcinoma (ACC) have not been studied. We performed immunohistochemical study on minor salivary and mucous gland ACC tissue samples of patients treated at the Helsinki University Hospital (Helsinki, Finland) during 1974-2012. We scored AZIN1 and 2 immunoexpression in 42 and 45 tumor tissue samples, respectively, and correlated them with clinicopathological factors and survival. Enhanced AZIN2 expression was associated with better survival. In addition, both AZINs were seen more commonly in cribriform and tubular than in solid growth patterns. AZIN1 expression did not correlate with the studied clinicopathological factors. It seems that AZIN2 expression is higher in cancer tissue with secretory functions. In ACC tissue, high AZIN2 expression could be related to well-differentiated histological type which still has a functioning vesicle transportation system. Thus, AZIN2 could be a prognostic factor for better survival of ACC patients.

Hypoxia-induced antizyme inhibitors 2 regulates cisplatin resistance through epithelia-mesenchymal transition pathway in non-small cell lung cancer

Antizyme inhibitors 2 (AZIN2) was found to be associated with poor prognosis of patients with rectal cancer. However, no studies have reported whether AZIN2 functions in non-small cell lung cancer (NSCLC). This study aimed to investigate the role of AZIN2 in cisplatin (DDP) resistance in NSCLC. We established DDP resistant A549 and H1299 cell lines. The transcriptional and translational expression levels were examined using quantitative real-time polymerase chain reaction and western blot. Cell apoptosis was evaluated by caspase-3 activity and nucleosome ELISA assays. Luciferase reporter assay was employed to evaluate the impact of hypoxia-inducible factor (HIF-1α) on AZIN2 transcription. AZIN2 expression was found to be associated with DDP resistance and poor prognosis in patients with NSCLC. AZIN2 overexpression promoted cell viability, colony formation, and reduced cell apoptosis in H1299 cells and A549 upon DDP treatment. Correspondingly, AZIN2 knockdown significantly inhibited cell viability and colony formation, and increased cell apoptosis upon DDP treatment. Interestingly, AZIN2 expression in NSCLC cells was significantly induced by hypoxia condition. The occupancy of HIF-1α, an important regulator of the hypoxia response, remarkably enriched at the promoter region of AZIN2 under hypoxia condition. In addition, AZIN2 overexpression resulted in epithelial-mesenchymal transition (EMT). The results suggested that hypoxia-induced AZIN2 high expression may contribute to DDP resistance development by promoting the EMT.

Capryloyl glycine and soy isoflavonoids in hypertrichosis: An experimental and placebo-controlled clinical study

Background

The management of acquired hypertrichosis (HT) is based on the search of the causes and subsequent specific treatment. However, simultaneous hair removal is important. No single method for hair removal is appropriate for all patients and skin areas. Treatment options are actually limited and clinical results are often unsatisfactory. Ornithine decarboxylase 1 (ODC1), an enzyme present in hair follicles, is considered as a potential target to inhibit hair growth. Only eflornithine hydrochloride, an inhibitor of ODC1, showed to be partially effective in the management of acquired HT.

Aims

The aim of our study was to evaluate the potential inhibition of ODC1 activity by a cream containing 4% capryloyl glycine, an ODC1 inhibitor, and 1% glycine soy‐fermented extract (soy isoflavonoids). Furthermore, we present the results of a placebo‐controlled clinical study that evaluated the efficacy and tolerability of this cream.

Methods

The ODC1 activity was detected by measuring absorbance at 340 nm. In the presence of ODC1 inhibitors, absorbance decreases as a function of inhibition. Difluoromethylornithine (DFMO) was provided as an inhibitor control. ODC1 activity inhibition was expressed as percentage of control (untreated sample). All data were presented as mean ± standard deviation of three independent experiments. To determine if statistically significant differences between treatments were present, a t test analysis was performed. The differences between groups were considered significant at p < 0.05. Twelve Caucasian female adult patients, with HT located on the forearms, were enrolled. The study cream (product A) was applied twice/day for four months on the right forearm. A placebo cream (product B) was applied twice/day for four months on the left forearm. Clinical efficacy was evaluated by means of macrophotography.

Results

The cream significantly inhibited ODC1 activity (35.1 ± 0.5% inhibition, equivalent to a 64.9 ± 0.5% ODC1 activity). DFMO completely abolished the enzymatic activity (100 ± 5% inhibition, equivalent to 0 ± 5% ODC1 activity). All patients were considered evaluable. In 11 out of 12 patients (91.7%), who were treated with product A, an improvement was observed. No improvement was observed in patients treated with product B. The global assessment showed good efficacy in 7 patients (58.3%) and moderate efficacy in 5 patients (41.7%) treated with the product A. No efficacy was detected in patients treated with product B.

Conclusions

The study cream showed to be effective in Caucasian, adult, female patients with hypertrichosis located on the forearms.

Copper-Catalyzed Enantioselective Difluoromethylation of Amino Acids via Difluorocarbene

Difluoromethyl amino acids (DFAA) exhibit intriguing biological properties, making them highly desirable motifs in agrochemical and pharmaceutical science. However, stereochemical control of direct difluoromethyl transformation via the difluorocarbene species has not been demonstrated. Here we describe an efficient copper-catalyzed asymmetric difluoromethylation reaction that systematically delivers chiral DFAA as rationally designed mechanism-based inhibitors of PLP-dependent amino acid decarboxylases. The reaction employs difluoromonochloromethane, an abundant raw material, as the direct precursor of difluorocarbene species, enabling the unprecedentedly direct conversion of amino esters into corresponding valuable DFAA products in good yields with excellent enantioselectivities. This de novo synthesis creates opportunities to integrate an asymmetric catalytic platform for the preparation of diverse libraries of biologically important DFAA derivatives and will support efforts in both drug discovery and development.

Emerging Role of ODC1 in Neurodevelopmental Disorders and Brain Development

Ornithine decarboxylase 1 (ODC1 gene) has been linked through gain-of-function variants to a rare disease featuring developmental delay, alopecia, macrocephaly, and structural brain anomalies. ODC1 has been linked to additional diseases like cancer, with growing evidence for neurological contributions to schizophrenia, mood disorders, anxiety, epilepsy, learning, and suicidal behavior. The evidence of ODC1 connection to neural disorders highlights the need for a systematic analysis of ODC1 genotype-to-phenotype associations. An analysis of variants from ClinVar, Geno2MP, TOPMed, gnomAD, and COSMIC revealed an intellectual disability and seizure connected loss-of-function variant, ODC G84R (rs138359527, NC_000002.12:g.10444500C > T). The missense variant is found in ~1% of South Asian individuals and results in 2.5-fold decrease in enzyme function. Expression quantitative trait loci (eQTLs) reveal multiple functionally annotated, non-coding variants regulating ODC1 that associate with psychiatric/neurological phenotypes. Further dissection of RNA-Seq during fetal brain development and within cerebral organoids showed an association of ODC1 expression with cell proliferation of neural progenitor cells, suggesting gain-of-function variants with neural over-proliferation and loss-of-function variants with neural depletion. The linkage from the expression data of ODC1 in early neural progenitor proliferation to phenotypes of neurodevelopmental delay and to the connection of polyamine metabolites in brain function establish ODC1 as a bona fide neurodevelopmental disorder gene.

Regulation of polyamine homeostasis through an antizyme citrullination pathway

This study reveals an uncovered mechanism for the regulation of polyamine homeostasis through protein arginyl citrullination of antizyme (AZ), a natural inhibitor of ornithine decarboxylase (ODC). ODC is critical for the cellular production of polyamines. AZ binds to ODC dimers and promotes the degradation of ODC via the 26S proteasome. This study demonstrates the protein citrullination of AZ catalyzed by peptidylarginine deiminase type 4 (PAD4) both in vitro and in cells. Upon PAD4 activation, the AZ protein was citrullinated and accumulated, leading to higher levels of ODC proteins in the cell. In the PAD4-overexpressing and activating cells, the levels of ODC enzyme activity and the product putrescine increased with the level of citrullinated AZ proteins and PAD4 activity. Suppressing cellular PAD4 activity reduces the cellular levels of ODC and downregulates cellular polyamines. Furthermore, citrullination of AZ in the C-terminus attenuates AZ function in the inhibition, binding, and degradation of ODC. This paper provides evidence to illustrate that PAD4-mediated AZ citrullination upregulates cellular ODC and polyamines by retarding ODC degradation, thus interfering with the homeostasis of cellular polyamines, which may be an important pathway regulating AZ functions that is relevant to cancer biology.

Upregulation of Antioxidant Capacity and Nucleotide Precursor Availability Suffices for Oncogenic Transformation

The emergence of cancer from diverse normal tissues has long been rationalized to represent a common set of fundamental processes. However, these processes are not fully defined. Here, we show that forced expression of glucose-6-phosphate dehydrogenase (G6PD) affords immortalized mouse and human cells anchorage-independent growth in vitro and tumorigenicity in animals. Mechanistically, G6PD augments the NADPH pool by stimulating NAD+ kinase-mediated NADP+ biosynthesis in addition to converting NADP+ to NADPH, bolstering antioxidant defense. G6PD also increases nucleotide precursor levels through the production of ribose and NADPH, promoting cell proliferation. Supplementation of antioxidants or nucleosides suffices to convert immortalized mouse and human cells into a tumorigenic state, and supplementation of both is required when their overlapping metabolic consequences are minimized. These results suggest that normal cells have a limited capacity for redox balance and nucleotide synthesis, and overcoming this limit might represent a key aspect of oncogenic transformation.

Assessment of the skin efficacy and acceptability of a cosmetic product in the treatment of the forearm hypertrichosis in female patients

BACKGROUND

Treatment of unwanted body hair is a challenging area in cosmetic dermatology. Topical soy isoflavones and derivatives or eflornithine have been utilized in dermatocosmetology for their estrogenic and antiandrogenic activity.

AIMS

To evaluate the efficacy of a formulation containing capryloyl glycine 4% in decreasing hair growth on the forearms after topical application for 120 days vs placebo.

METHODS

A total of 69 female patients entered the study (age 37 ± 6). Hair growth was quantified using TrichoScan software on both forearms at 20-fold magnification (analyzed area 0.651 cm2). Hair density (number of hairs/cm² ), density vellus hair, density terminal hair, and median length of hairs were evaluated. The data were analyzed using ANOVA for repeated measures to evaluate changes during the treatment (T0, T60, and T120) and Student's t test (placebo vs active).

RESULTS

There was a significant decrease on hair density, median, and terminal hair at the end of the treatment in the active-treated site (P < .001) as measured by TrichoScan software. Direct comparison between active and placebo-treated sites showed no significant differences at T0, but highly significant differences at T120 (P < .001).

CONCLUSIONS

The study shows that a cosmetic formulation based on capryloyl glycine 4% is highly effective in reducing several parameters related to hair growth and hair thickness vs placebo, thus showing efficacy in the treatment of hypertrichosis.

Baicalein, 7,8-Dihydroxyflavone and Myricetin as Potent Inhibitors of Human Ornithine Decarboxylase

Background: Human ornithine decarboxylase (ODC) is a well-known oncogene, and the discovery of ODC enzyme inhibitors is a beneficial strategy for cancer therapy and prevention. Methods: We examined the inhibitory effects of a variety of flavone and flavonol derivatives on ODC enzymatic activity, and performed in silico molecular docking of baicalein, 7,8-dihydroxyflavone and myricetin to the whole dimer of human ODC to investigate the possible binding site of these compounds on ODC. We also examined the cytotoxic effects of these compounds with cell-based studies. Results: Baicalein, 7,8-dihydroxyflavone and myricetin exhibited significant ODC suppression activity with IC₅₀ values of 0.88 µM, 2.54 µM, and 7.3 µM, respectively, which were much lower than that of the active-site irreversible inhibitor α-DL-difluoromethylornithine (IC₅₀, the half maximal inhibitory concentration, of approximately 100 µM). Kinetic studies and molecular docking simulations suggested that baicalein, and 7,8-dihydroxyflavone act as noncompetitive inhibitors that are hydrogen-bonded to the region near the active site pocket in the dimer interface of the enzyme. Baicalein and myricetin suppress cell growth and induce cellular apoptosis, and both of these compounds suppress the ODC-evoked anti-apoptosis of cells. Conclusions: Therefore, we suggest that the flavone or flavonol derivatives baicalein, 7,8-dihydroxyflavone, and myricetin are potent chemopreventive and chemotherapeutic agents that target ODC.

Allicin, a Potent New Ornithine Decarboxylase Inhibitor in Neuroblastoma Cells

The natural product allicin is a reactive sulfur species (RSS) from garlic (Allium sativum L.). Neuroblastoma (NB) is an early childhood cancer arising from the developing peripheral nervous system. Ornithine decarboxylase (ODC) is a rate-limiting enzyme in the biosynthesis of polyamines, which are oncometabolites that contribute to cell proliferation in NB and other c-MYC/MYCN-driven cancers. Both c-MYC and MYCN directly transactivate the E-box gene ODC1, a validated anticancer drug target. We identified allicin as a potent ODC inhibitor in a specific radioactive in vitro assay using purified human ODC. Allicin was ∼23 000-fold more potent (IC₅₀ = 11 nM) than DFMO (IC₅₀ = 252 μM), under identical in vitro assay conditions. ODC is a homodimer with 12 cysteines per monomer, and allicin reversibly S-thioallylates cysteines. In actively proliferating human NB cells allicin inhibited ODC enzyme activity, reduced cellular polyamine levels, inhibited cell proliferation (IC₅₀ 9-19 μM), and induced apoptosis. The natural product allicin is a new ODC inhibitor and could be developed for use in conjunction with other anticancer treatments, the latter perhaps at a lower than usual dosage, to achieve drug synergism with good prognosis and reduced adverse effects.

The rational discovery of multipurpose inhibitors of the ornithine decarboxylase

Metabolic reprograming is a hallmark of cancer, and the polyamine metabolic network is dysregulated in many cancers. Ornithine decarboxylase (ODC) is a rate-limiting enzyme for polyamine synthesis in the polyamine metabolic network. In many cancer cells, ODC is over-expressed, so this enzyme has been an attracting anti-cancer drug target. In the catalysis axis (pathway), ODC converts ornithine to putrescine. Meanwhile, ODC's activity is regulated by protein-protein interactions (PPIs), including the ODC-OAZ1-AZIN1 PPI axis and its monomer-dimer equilibrium. Previous studies showed that when ODC's activity is inhibited, the PPIs might counteract the inhibition efficiency. Therefore, we proposed that multipurpose inhibitors that can simultaneously inhibit ODC's activity and perturb the PPIs would be very valuable as drug candidates and molecular tools. To discover multipurpose ODC inhibitors, we established a computational pipeline by combining positive screening and negative screening. We used this pipeline for the forward screening of multipurpose ligands that might inhibit ODC's activity, block ODC-OAZ1 interaction and enhance ODC non-functional dimerization. With a combination of different experimental assays, we identified three multipurpose ODC inhibitors. At last, we showed that one of these inhibitors is a promising drug candidate. This work demonstrated that our computational pipeline is useful for discovering multipurpose ODC inhibitors, and multipurpose inhibitors would be very valuable. Similar with ODC, there are a lot of proteins in human proteome that act as both enzymes and PPI components. Therefore, this work is not only presenting new molecular tools for polyamine study, but also providing potential insights and protocols for discovering multipurpose inhibitors to target more important protein targets.

Enzyme-mediated depletion of serum l-Met abrogates prostate cancer growth via multiple mechanisms without evidence of systemic toxicity

Extensive studies in prostate cancer and other malignancies have revealed that l-methionine (l-Met) and its metabolites play a critical role in tumorigenesis. Preclinical and clinical studies have demonstrated that systemic restriction of serum l-Met, either via partial dietary restriction or with bacterial l-Met-degrading enzymes exerts potent antitumor effects. However, administration of bacterial l-Met-degrading enzymes has not proven practical for human therapy because of problems with immunogenicity. As the human genome does not encode l-Met-degrading enzymes, we engineered the human cystathionine-γ-lyase (hMGL-4.0) to catalyze the selective degradation of l-Met. At therapeutically relevant dosing, hMGL-4.0 reduces serum l-Met levels to >75% for >72 h and significantly inhibits the growth of multiple prostate cancer allografts/xenografts without weight loss or toxicity. We demonstrate that in vitro, hMGL-4.0 causes tumor cell death, associated with increased reactive oxygen species, S-adenosyl-methionine depletion, global hypomethylation, induction of autophagy, and robust poly(ADP-ribose) polymerase (PARP) cleavage indicative of DNA damage and apoptosis.

Targeted delivery of thermoresponsive polymeric nanoparticle-encapsulated lycopene: in vitro anticancer activity and chemopreventive effect on murine skin inflammation and tumorigenesis

Naturally occurring lycopene has been reported for its chemopreventive and chemotherapeutic efficiency in various cancers, but its exceptional lipophilicity, poor aqueous solubility, instability, and consequently poor bioavailability limit its usage as a chemopreventive and chemotherapeutic agent. The present study aimed to synthesize co-polymeric nanoparticle-encapsulated formulations of commercial lycopene (NLY) and extracted lycopene (NLX) and evaluate their in vitro anticancer activity and inhibitory effect on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin inflammation and tumorigenesis in Swiss albino mice. To prepare the nanoparticle-encapsulated formulations of lycopene, thermosensitive PNIPAAM-PEG-based co-polymeric nanoparticles were synthesized and characterized by FTIR spectroscopy, NMR spectroscopy, DLS, and TEM. Nanolycopene, unlike free lycopene, could be readily dispersed in aqueous media. Nanolycopene demonstrated stronger antioxidant activity and comparable in vitro anticancer efficacy to free lycopene against the melanoma cell line B16. Furthermore, nanolycopene showed comparable reduction of TPA-induced skin edema, expression of COX-2, and oxidative stress response. Additionally, it showed significant inhibition of tumor promotion. It also altered Bax and Bcl2 expressions, which led to the induction of apoptosis. The results also supported that the extracted lycopene-encapsulated nanoparticles may be a good alternative to the expensive commercial lycopene for cancer treatment.

Large-scale analysis of zebrafish (Danio rerio) transcriptomes identifies functional modules associated with phenotypes

Zebrafish (Danio rerio) is an excellent model for biomedicine research due to its genetic accessibility and optical transparency. A large number of microarray based transcriptomes of zebrafish have been profiled in various cell types, tissues, development stages, toxicological exposures and other conditions. However, there is still no easy-to-use web tool to explore those precious data. We downloaded 1434 microarray data from National Center for Biotechnology Information Gene Expression Omnibus (NCBI GEO), constructed weighted gene co-expression network, and identified 50 modules of co-expressed genes that correspond to different cell types, tissues, development stages, and other experimental conditions. These modules were associated with experiments/traits, and may serve signature modules for phenotypes. Hub genes were screened by intra-modular connectivity. Higher-order module networks analysis suggested that nucleus and cell cycle modules are densely connected. Module-based gene function identification may help to discover novel gene function. Our web tool provides a new resource for gene function study in zebrafish (http://bioinformatics.fafu.edu.cn/zebrafish/).

Enhancement of the cancer inhibitory effect of the bioactive food component resveratrol by nanoparticle based delivery

Naturally occurring bioactive food components such as dietary polyphenols have shown many beneficial biological activities due to their good antioxidant properties. Among them significant attention has been given to resveratrol (RV) in recent years as it plays a promising role in cancer prevention. It has demonstrated anti-proliferative effects, as well as the ability to inhibit the initiation and progression of induced cancer in a wide variety of tumor models. However, the benefits of its therapeutic effects were found to be limited due to its poor pharmacokinetic properties such as poor aqueous solubility, instability and extensive first pass metabolism. To overcome these limitations, the present study aimed to synthesize thermosensitive copolymeric nanoparticle encapsulated formulations of resveratrol-nanoresveratrol (NRV) and evaluate their in vitro anticancer activity and inhibitory effect on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin inflammation and tumorigenesis in Swiss albino mice. For this purpose PNIPAAM-PEG based thermosensitive copolymeric nanoparticles were synthesized followed by the encapsulation of RV in their hydrophobic core. This enhanced the therapeutic bioavailability of resveratrol. Nanoresveratrol demonstrated stronger antioxidant activity and comparable anticancer efficacy to free resveratrol. Nanoparticles were characterized by IR, NMR, DLS and TEM. The best results were obtained with NRV at significantly lower doses. NRV demonstrated better in vitro anticancer activity against melanoma cell line B16. It showed comparable reduction of TPA induced skin edema, hyperplasia and oxidative stress response. In the promotion phase, a significant reduction was found in tumor incidence and tumor burden in mice pre-treated with NRV. Moreover, at all doses NRV altered Bax and Bcl2 expressions which lead to the induction of apoptosis.

Critical Factors in Human Antizymes that Determine the Differential Binding, Inhibition, and Degradation of Human Ornithine Decarboxylase

Antizyme (AZ) is a protein that negatively regulates ornithine decarboxylase (ODC). AZ achieves this inhibition by binding to ODC to produce AZ-ODC heterodimers, abolishing enzyme activity and targeting ODC for degradation by the 26S proteasome. In this study, we focused on the biomolecular interactions between the C-terminal domain of AZ (AZ_95–228) and ODC to identify the functional elements of AZ that are essential for binding, inhibiting and degrading ODC, and we also identified the crucial factors governing the differential binding and inhibition ability of AZ isoforms toward ODC. Based on the ODC inhibition and AZ-ODC binding studies, we demonstrated that amino acid residues reside within the α1 helix, β5 and β6 strands, and connecting loop between β6 and α2 (residues 142–178), which is the posterior part of AZ_95–228, play crucial roles in ODC binding and inhibition. We also identified the essential elements determining the ODC-degradative activity of AZ; amino acid residues within the anterior part of AZ_95–228 (residues 120–145) play crucial roles in AZ-mediated ODC degradation. Finally, we identified the crucial factors that govern the differential binding and inhibition of AZ isoforms toward ODC. Mutagenesis studies of AZ1 and AZ3 and their binding and inhibition revealed that the divergence of amino acid residues 124, 150, 166, 171, and 179 results in the differential abilities of AZ1 and AZ3 in the binding and inhibition of ODC.

Purification and Characterization of Ornithine Decarboxylase from Aspergillus terreus; Kinetics of Inhibition by Various Inhibitors

l-Ornithine decarboxylase (ODC) is the rate-limiting enzyme of de novo polyamine synthesis in humans and fungi. Elevated levels of polyamine by over-induction of ODC activity in response to tumor-promoting factors has been frequently reported. Since ODC from fungi and human have the same molecular properties and regulatory mechanisms, thus, fungal ODC has been used as model enzyme in the preliminary studies. Thus, the aim of this work was to purify ODC from fungi, and assess its kinetics of inhibition towards various compounds. Forty fungal isolates were screened for ODC production, twenty fungal isolates have the higher potency to grow on L-ornithine as sole nitrogen source. Aspergillus terreus was the most potent ODC producer (2.1 µmol/mg/min), followed by Penicillium crustosum and Fusarium fujikuori. These isolates were molecularly identified based on their ITS sequences, which have been deposited in the NCBI database under accession numbers MH156195, MH155304 and MH152411, respectively. ODC was purified and characterized from A. terreus using SDS-PAGE, showing a whole molecule mass of ~110 kDa and a 50 kDa subunit structure revealing its homodimeric identity. The enzyme had a maximum activity at 37 °C, pH 7.4-7.8 and thermal stability for 20 h at 37 °C, and 90 days storage stability at 4 °C. A. terreus ODC had a maximum affinity (K_m) for l-ornithine, l-lysine and l-arginine (0.95, 1.34 and 1.4 mM) and catalytic efficiency (k_cat/K_m) (4.6, 2.83, 2.46 × 10^-5 mM^-1·s^-1). The enzyme activity was strongly inhibited by DFMO (0.02 µg/mL), curcumin (IC₅₀ 0.04 µg/mL), propargylglycine (20.9 µg/mL) and hydroxylamine (32.9 µg/mL). These results emphasize the strong inhibitory effect of curcumin on ODC activity and subsequent polyamine synthesis. Further molecular dynamic studies to elucidate the mechanistics of ODC inhibition by curcumin are ongoing.

Ornithine decarboxylase antizyme inhibitor 2 (AZIN2) is a signature of secretory phenotype and independent predictor of adverse prognosis in colorectal cancer

Ornithine decarboxylase (ODC) is the rate-limiting enzyme of polyamine synthesis. The two ODC antizyme inhibitors (AZIN1) and (AZIN2) are regulators of the catalytic activity of ODC. While AZIN1 is a regulator of cell proliferation, AZIN2 is involved in intracellular vesicle transport and secretion. There are no previous reports on the impact of AZIN2 expression in human cancer. We applied immunohistochemistry with antibodies to human AZIN2 on tissue micro- arrays of colorectal cancers (CRC) from 840 patients with a median follow-up of 5.1 years (range 0-25.8). The 5-year disease-specific survival rate was 58.9% (95% Cl 55.0-62.8%). High AZIN2 expression was associated with mucinous histology (p = 0.002) and location in the right hemicolon (p = 0.021). We found no association with age, gender, stage, or histological tumor grade. High tumor expression of AZIN2 predicted an unfavorable prognosis (p<0.0001, log-rank test), compared to low AZIN2 expression. Cox multivariable analysis identified AZIN2 as an independent factor of an unfavorable prognosis in CRC. The strongest AZIN2 expression was seen in invasive tumor cells having morphological features of epithelial-mesenchymal transition (EMT). Induction of EMT in HT-29 CRC cells lead to upregulated expression of endogenous AZIN2. Given that AZIN2 is a regulator of vesicle transport and secretion, we overexpressed human AZIN2 cDNA in T84 CRC cells, and found strongly enhanced accumulation of CD63-positive exosomes in the culture medium. These findings indicate that AZIN2 expression is a signature of EMT-associated secretory phenotype that is linked to an adverse prognosis in CRC.

Human Fetal TNF-α-Cytokine-Producing CD4+ Effector Memory T Cells Promote Intestinal Development and Mediate Inflammation Early in Life

Although the fetal immune system is considered tolerogenic, preterm infants can suffer from severe intestinal inflammation, including necrotizing enterocolitis (NEC). Here, we demonstrate that human fetal intestines predominantly contain tumor necrosis factor-α (TNF-α)⁺CD4⁺CD69⁺ T effector memory (Tem) cells. Single-cell RNA sequencing of fetal intestinal CD4⁺ T cells showed a T helper 1 phenotype and expression of genes mediating epithelial growth and cell cycling. Organoid co-cultures revealed a dose-dependent, TNF-α-mediated effect of fetal intestinal CD4⁺ T cells on intestinal stem cell (ISC) development, in which low T cell numbers supported epithelial development, whereas high numbers abrogated ISC proliferation. CD4⁺ Tem cell frequencies were higher in inflamed intestines from preterm infants with NEC than in healthy infant intestines and showed enhanced TNF signaling. These findings reveal a distinct population of TNF-α-producing CD4⁺ T cells that promote mucosal development in fetal intestines but can also mediate inflammation upon preterm birth.

5'-Methylthioadenosine and Cancer: old molecules, new understanding

While the metabolic changes in cancer tissues were first observed by Warburg Otto almost a century ago, altered metabolism has recently returned as a focus of cancer research. 5'-Methylthioadenosine (MTA) is a naturally occurring sulfur-containing nucleoside found in numerous species. While MTA was first isolated several decades ago, a lack of sensitive and specific analytical methodologies designed for its direct quantification has hampered the study of its physiological and pathophysiological features. Many studies indicate that MTA suppresses tumors by inhibiting tumor cell proliferation, invasion, and the induction of apoptosis while controlling the inflammatory micro-environments of tumor tissue. In this review, we assessed the effects of MTA and of related materials on the growth and functions of normal and malignant cells.

Metabolism within the tumor microenvironment and its implication on cancer progression: An ongoing therapeutic target

Since reprogramming energy metabolism is considered a new hallmark of cancer, tumor metabolism is again in the spotlight of cancer research. Many studies have been carried out and many possible therapies have been developed in the last years. However, tumor cells are not alone. A series of extracellular components and stromal cells, such as endothelial cells, cancer-associated fibroblasts, tumor-associated macrophages, and tumor-infiltrating T cells, surround tumor cells in the so-called tumor microenvironment (TME). Metabolic features of these cells are being studied in deep in order to find relationships between metabolism within the TME and tumor progression. Moreover, it cannot be forgotten that tumor growth is able to modulate host metabolism and homeostasis, so that TME is not the whole story. Importantly, the metabolic switch in cancer is just a consequence of the flexibility and adaptability of metabolism and should not be surprising. Treatments of cancer patients with combined therapies including antitumor agents with those targeting stromal cell metabolism, antiangiogenic drugs, and/or immunotherapy are being developed as promising therapeutics.

Divergent roles of lysyl oxidase family members in ornithine decarboxylase- and RAS-transformed mouse fibroblasts and human melanoma cells

We have previously shown that proto-oncoprotein c-Jun is activated in ornithine decarboxylase (ODC)- and RAS-transformed mouse fibroblasts, and that the transformed morphology of these cells can be reversed by expressing the transactivation domain deletion mutant of c-Jun (TAM67). Here, we found that lysyl oxidase (Lox), encoding an extracellular matrix-modifying enzyme, is downregulated in a c-Jun-dependent manner in ODC-transformed fibroblasts (Odc cells). In addition to Lox, the Lox family members Lox-like 1 and 3 (Loxl1 and Loxl3) were found to be downregulated in Odc as well as in RAS-transformed fibroblasts (E4), whereas Lox-like 4 (Loxl4) was upregulated in Odc and downregulated in E4 cells compared to normal N1 fibroblasts. Tetracycline-regulatable LOX re-expression in Odc cells led to inhibition of cell growth and invasion in three-dimensional Matrigel in an activity-independent manner. On the contrary, LOX and especially LOXL2, LOXL3, and LOXL4 were found to be upregulated in several human melanoma cell lines, and LOX inhibitor B-aminopropionitrile inhibited the invasive growth of these cells particularly when co-cultured with fibroblasts in Matrigel. Knocking down the expression of LOX and especially LOXL2 in melanoma cells almost completely abrogated the invasive growth capability. Further, LOXL2 was significantly upregulated in clinical human primary melanomas compared to benign nevi, and high expression of LOXL2 in primary melanomas was associated with formation of metastases and shorter survival of patients. Thus, our studies reveal that inactive pro-LOX (together with Lox propeptide) functions as a tumor suppressor in ODC- and RAS-transformed murine fibroblasts by inhibiting cell growth and invasion, and active LOX and LOXL2 as tumor promoters in human melanoma cells by promoting their invasive growth.

Polyamines interfere with protein ubiquitylation and cause depletion of intracellular amino acids: a possible mechanism for cell growth inhibition

Spermidine is a polyamine present in eukaryotes with essential functions in protein synthesis. At high concentrations spermidine and norspermidine inhibit growth by unknown mechanisms. Transcriptomic analysis of the effect of norspermidine on the plant Arabidopsis thaliana indicates upregulation of the response to heat stress and denatured proteins. Accordingly, these polyamines inhibit protein ubiquitylation, both in vivo (in yeast, Arabidopsis, and human Hela cells) and in vitro (with recombinant ubiquitin ligase). This interferes with protein degradation by the proteasome, a situation known to deplete cells of amino acids. Norspermidine treatment of yeast cells induces amino acid depletion, and supplementation of media with amino acids counteracts growth inhibition and cellular amino acid depletion but not inhibition of protein polyubiquitylation.

A Multicomponent Neuronal Response Encodes the Larval Decision to Pupariate upon Amino Acid Starvation

Organisms need to coordinate growth with development, particularly in the context of nutrient availability. Thus, multiple ways have evolved to survive extrinsic nutrient deprivation during development. In Drosophila, growth occurs during larval development. Larvae are thus critically dependent on nutritional inputs; but after critical weight, they pupariate even when starved. How nutrient availability is coupled to the internal metabolic state for the decision to pupariate needs better understanding. We had earlier identified glutamatergic interneurons in the ventral ganglion that regulate pupariation on a protein-deficient diet. Here we report that Drosophila third instar larvae (either sex) sense arginine to evaluate their nutrient environment using an amino acid transporter Slimfast. The glutamatergic interneurons integrate external protein availability with internal metabolic state through neuropeptide signals. IP3-mediated calcium release and store-operated calcium entry are essential in these glutamatergic neurons for such integration and alter neuronal function by reducing the expression of multiple ion channels.SIGNIFICANCE STATEMENT Coordinating growth with development, in the context of nutrient availability is a challenge for all organisms in nature. After attainment of "critical weight," insect larvae can pupariate, even in the absence of nutrition. Mechanism(s) that stimulate appropriate cellular responses and allow normal development on a nutritionally deficient diet remain to be understood. Here, we demonstrate that nutritional deprivation, in postcritical weight larvae, is sensed by special sensory neurons through an amino acid transporter that detects loss of environmental arginine. This information is integrated by glutamatergic interneurons with the internal metabolic state through neuropeptide signals. These glutamatergic interneurons require calcium-signaling-regulated expression of a host of neuronal channels to generate complex calcium signals essential for pupariation on a protein-deficient diet.

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.

The antizyme family for regulating polyamines

The polyamines spermidine, spermine, and their precursor putrescine are organic polycations involved in various cellular processes and are absolutely essential for cellular proliferation. Because of their crucial function in the cell, their intracellular concentration must be maintained at optimal levels. To a large extent, this regulation is achieved through the activity of an autoregulatory loop that involves two proteins, antizyme (Az) and antizyme inhibitor (AzI), that regulate the first enzyme in polyamine biosynthesis, ornithine decarboxylase (ODC), and polyamine uptake activity in response to intracellular polyamine levels. In this Minireview, I will discuss what has been learned about the mechanism of Az expression and its physical interaction with both ODC and AzI in the regulation of polyamines.

Polyamine Metabolism and Gene Methylation in Conjunction with One-Carbon Metabolism

Recent investigations have revealed that changes in DNA methylation status play an important role in aging-associated pathologies and lifespan. The methylation of DNA is regulated by DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) in the presence of S-adenosylmethionine (SAM), which serves as a methyl group donor. Increased availability of SAM enhances DNMT activity, while its metabolites, S-adenosyl-l-homocysteine (SAH) and decarboxylated S-adenosylmethionine (dcSAM), act to inhibit DNMT activity. SAH, which is converted from SAM by adding a methyl group to cytosine residues in DNA, is an intermediate precursor of homocysteine. dcSAM, converted from SAM by the enzymatic activity of adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize the polyamines spermine and spermidine. Increased homocysteine levels are a significant risk factor for the development of a wide range of conditions, including cardiovascular diseases. However, successful homocysteine-lowering treatment by vitamins (B6, B12, and folate) failed to improve these conditions. Long-term increased polyamine intake elevated blood spermine levels and inhibited aging-associated pathologies in mice and humans. Spermine reversed changes (increased dcSAM, decreased DNMT activity, aberrant DNA methylation, and proinflammatory status) induced by the inhibition of ornithine decarboxylase. The relation between polyamine metabolism, one-carbon metabolism, DNA methylation, and the biological mechanism of spermine-induced lifespan extension is discussed.

Inhibition of the aryl hydrocarbon receptor/polyamine biosynthesis axis suppresses multiple myeloma

Polyamine inhibition for cancer therapy is, conceptually, an attractive approach but has yet to meet success in the clinical setting. The aryl hydrocarbon receptor (AHR) is the central transcriptional regulator of the xenobiotic response. Our study revealed that AHR also positively regulates intracellular polyamine production via direct transcriptional activation of 2 genes, ODC1 and AZIN1, which are involved in polyamine biosynthesis and control, respectively. In patients with multiple myeloma (MM), AHR levels were inversely correlated with survival, suggesting that AHR inhibition may be beneficial for the treatment of this disease. We identified clofazimine (CLF), an FDA-approved anti-leprosy drug, as a potent AHR antagonist and a suppressor of polyamine biosynthesis. Experiments in a transgenic model of MM (Vk*Myc mice) and in immunocompromised mice bearing MM cell xenografts revealed high efficacy of CLF comparable to that of bortezomib, a first-in-class proteasome inhibitor used for the treatment of MM. This study identifies a previously unrecognized regulatory axis between AHR and polyamine metabolism and reveals CLF as an inhibitor of AHR and a potentially clinically relevant anti-MM agent.

Curcumin mediates polyamine metabolism and sensitizes gastrointestinal cancer cells to antitumor polyamine-targeted therapies

Curcumin, a natural polyphenol that contributes to the flavor and yellow pigment of the spice turmeric, is known for its antioxidant, anti-inflammatory, and anticarcinogenic properties. Capable of affecting the initiation, promotion, and progression of carcinogenesis through multiple mechanisms, curcumin has potential utility for both chemoprevention and chemotherapy. Previous studies demonstrated that curcumin can inhibit ornithine decarboxylase (ODC) activity in human leukemia and breast cancer cells, and pretreatment with dietary curcumin blocks carcinogen-induced ODC activity in rodent models of skin, colon, and renal cancer. The current study investigated the regulation of polyamine metabolism in human gastric and colon carcinoma cell lines in response to curcumin. Curcumin treatment significantly induced spermine oxidase (SMOX) mRNA and activity, which results in the generation of hydrogen peroxide, a source of ROS. Simultaneously, curcumin down regulated spermidine/spermine N1-acetyltransferase (SSAT) activity and the biosynthetic enzymes ODC and S-adenosylmethionine decarboxylase (SAMDC), thereby diminishing intracellular polyamine pools. Combination treatments using curcumin with the ODC inhibitor 2-difluoromethylornithine (DFMO), an agent currently in clinical chemoprevention trials, significantly enhanced inhibition of ODC activity and decreased growth of GI cancer cell lines beyond that observed with either agent alone. Similarly, combining curcumin with the polyamine analogue bis(ethyl)norspermine enhanced growth inhibition that was accompanied by enhanced accumulation of the analogue and decreased intracellular polyamine levels beyond those observed with either agent alone. Importantly, cotreatment with curcumin permitted the lowering of the effective dose of ODC inhibitor or polyamine analogue. These studies provide insight into the polyamine-related mechanisms involved in the cancer cell response to curcumin and its potential as a chemopreventive or chemotherapeutic agent in the GI tract.

Myc, Oncogenic Protein Translation, and the Role of Polyamines

Deregulated protein synthesis is a common feature of cancer cells, with many oncogenic signaling pathways directly augmenting protein translation to support the biomass needs of proliferating tissues. MYC’s ability to drive oncogenesis is a consequence of its essential role as a governor linking cell cycle entry with the requisite increase in protein synthetic capacity, among other biomass needs. To date, direct pharmacologic inhibition of MYC has proven difficult, but targeting oncogenic signaling modules downstream of MYC, such as the protein synthetic machinery, may provide a viable therapeutic strategy. Polyamines are essential cations found in nearly all living organisms that have both direct and indirect roles in the control of protein synthesis. Polyamine metabolism is coordinately regulated by MYC to increase polyamines in proliferative tissues, and this is further augmented in the many cancer cells harboring hyperactivated MYC. In this review, we discuss MYC-driven regulation of polyamines and protein synthetic capacity as a key function of its oncogenic output, and how this dependency may be perturbed through direct pharmacologic targeting of components of the protein synthetic machinery, such as the polyamines themselves, the eukaryotic translation initiation factor 4F (eIF4F) complex, and the eukaryotic translation initiation factor 5A (eIF5A).

Urinary Excretion of Free and Acetylated Polyamines in Hepatocellular Carcinoma

Polyamines (putrescine, spermidine and spermine) are essential for the proliferation of normal and neoplastic cells, and have been repeatedly recommended as tumor markers, with contrasting and elusive results.

In the present study the urinary excretion of free and acetylated polyamines was measured in patients with hepatocellular carcinoma (HCC), cirrhotics and control subjects.

Separation and quantification of dansyl-derivatives of free, acetylated and total polyamines was performed by reverse-phase high-performance liquid chromatography.

The results show that the urinary excretion of total, free, and acetylated polyamines is significantly higher in HCC patients than in cirrhotics and controls (p<0.001). The N1/N8 acetyl-spermidine molar ratio was found to be higher in HCC patients than in cirrhotics and controls (p<0.001). No correlation was found between urinary excretion of polyamines and serum alpha-fetoprotein, tumor size and severity of liver cirrhosis. The results show that increased urinary excretion of free and acetylated polyamines, as well as an altered N1/N8-acetyl-spermidine molar ratio, is a sensible but not specific feature of HCC patients; polyamines may play a role in human carcinogenesis, but their determination does not seem reliable for the early detection of liver cancer.

Regulation of Polyamine Metabolism by Curcumin for Cancer Prevention and Therapy

Curcumin (diferuloylmethane), the natural polyphenol responsible for the characteristic yellow pigment of the spice turmeric (Curcuma longa), is traditionally known for its antioxidant, anti-inflammatory, and anticarcinogenic properties. Capable of affecting the initiation, promotion, and progression of carcinogenesis through multiple mechanisms, curcumin has potential utility for both chemoprevention and chemotherapy. In human cancer cell lines, curcumin has been shown to decrease ornithine decarboxylase (ODC) activity, a rate-limiting enzyme in polyamine biosynthesis that is frequently upregulated in cancer and other rapidly proliferating tissues. Numerous studies have demonstrated that pretreatment with curcumin can abrogate carcinogen-induced ODC activity and tumor development in rodent tumorigenesis models targeting various organs. This review summarizes the results of curcumin exposure with regard to the modulation of polyamine metabolism and discusses the potential utility of this natural compound in conjunction with the exploitation of dysregulated polyamine metabolism in chemopreventive and chemotherapeutic settings.

Polyamines, folic acid supplementation and cancerogenesis

Clinical practice and experimental studies have shown the necessity of sufficient quantities of folic acid intake for normal embryogenesis and fetal development in the prevention of neural tube defects (NTDs) and neurological malformations. So, women of childbearing age must be sure to have an adequate folate intake periconceptionally, prior to and during pregnancy. Folic acid fortification of all enriched cereal grain product flour has been implemented in many countries. Thus, hundreds of thousands of people have been exposed to an increased intake of folic acid. Folate plays an essential role in the biosynthesis of methionine. Methionine is the principal aminopropyl donor required for polyamine biosynthesis, which is up-regulated in actively growing cells, including cancer cells. Folates are important in RNA and DNA synthesis, DNA stability and integrity. Clinical and epidemiological evidence links folate deficiency to DNA damage and cancer. On the other hand, long-term folate oversupplementation leads to adverse toxic effects, resulting in the appearance of malignancy. Considering the relationship of polyamines and rapidly proliferating tissues (especially cancers), there is a need for better investigation of the relationship between the ingestion of high amounts of folic acid in food supplementation and polyamine metabolism, related to malignant processes in the human body.