Increased hepatic putrescine levels as a new potential factor related to the progression of metabolic dysfunction-associated steatotic liver disease.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic liver condition that often progresses to more advanced stages, such as metabolic dysfunction-associated steatohepatitis (MASH). MASH is characterized by inflammation and hepatocellular ballooning, in addition to hepatic steatosis. Despite the relatively high incidence of MASH in the population and its potential detrimental effects on human health, this liver disease is still not fully understood from a pathophysiological perspective. Deregulation of polyamine levels has been detected in various pathological conditions, including neurodegenerative diseases, inflammation, and cancer. However, the role of the polyamine pathway in chronic liver disorders such as MASLD has not been explored. In this study, we measured the expression of liver ornithine decarboxylase (ODC1), the rate-limiting enzyme responsible for the production of putrescine, and the hepatic levels of putrescine, in a preclinical model of MASH as well as in liver biopsies of patients with obesity undergoing bariatric surgery. Our findings reveal that expression of ODC1 and the levels of putrescine, but not spermidine nor spermine, are elevated in hepatic tissue of both diet-induced MASH mice and patients with biopsy-proven MASH compared with control mice and patients without MASH, respectively. Furthermore, we found that the levels of putrescine were positively associated with higher aspartate aminotransferase concentrations in serum and an increased SAF score (steatosis, activity, fibrosis). Additionally, in in vitro assays using human HepG2 cells, we demonstrate that elevated levels of putrescine exacerbate the cellular response to palmitic acid, leading to decreased cell viability and increased release of CK-18. Our results support an association between the expression of ODC1 and the progression of MASLD, which could have translational relevance in understanding the onset of this disease. © 2024 The Pathological Society of Great Britain and Ireland.

Identification and validation of a metabolism-related gene signature for predicting the prognosis of paediatric medulloblastoma.

Medulloblastoma (MB) is a malignant brain tumour that is highly common in children and has a tendency to spread to the brain and spinal cord. MB is thought to be a metabolically driven brain tumour. Understanding tumour cell metabolic patterns and characteristics can provide a promising foundation for understanding MB pathogenesis and developing treatments. Here, by analysing RNA-seq data of MB samples from the Gene Expression Omnibus (GEO) database, 12 differentially expressed metabolic-related genes (DE-MRGs) were chosen for the construction of a predictive risk score model for MB. This model demonstrated outstanding accuracy in predicting the outcomes of MB patients and served as a standalone predictor. An evaluation of functional enrichment revealed that the risk score showed enrichment in pathways related to cancer promotion and the immune response. In addition, a high risk score was an independent poor prognostic factor for MB in patients with different ages, sexes, metastasis stages and subgroups (SHH and Group 4). Consistently, the metabolic enzyme ornithine decarboxylase (ODC1) was upregulated in MB patients with poor survival time. Inhibition of ODC1 in primary and metastatic MB cell lines decreased cell proliferation, migration and invasion but increased immune infiltration. This study could aid in identifying metabolic targets for MB as well as optimizing risk stratification systems and individual treatment plans for MB patients via the use of a metabolism-related gene prognostic risk score signature.

Elevated expression of HIGD1A drives hepatocellular carcinoma progression by regulating polyamine metabolism through c-Myc-ODC1 nexus.

BACKGROUND: Hypoxia contributes to cancer progression through various molecular mechanisms and hepatocellular carcinoma (HCC) is one of the most hypoxic malignancies. Hypoxia-inducible gene domain protein-1a (HIGD1A) is typically induced via epigenetic regulation and promotes tumor cell survival during hypoxia. However, the role of HIGD1A in HCC remains unknown. METHODS: HIGD1A expression was determined in 24 pairs of human HCC samples and para-tumorous tissues. Loss-of-function experiments were conducted both in vivo and in vitro to explore the role of HIGD1A in HCC proliferation and metastasis. RESULTS: Increased HIGD1A expression was found in HCC tissues and cell lines, which was induced by hypoxia or low-glucose condition. Moreover, HIGD1A knockdown in HCC cells arrested the cell cycle at the G2/M phase and promoted hypoxia-induced cell apoptosis, resulting in great inhibition of cell proliferation, migration, and invasion, as well as tumor xenograft formation. Interestingly, these anti-tumor effects were not observed in normal hepatocyte cell line L02. Further, HIGD1A knockdown suppressed the expression of ornithine decarboxylase 1 (ODC1), a rate-limiting enzyme of polyamine metabolism under c-Myc regulation. HIGD1A was found to bind with the c-Myc promoter region, and its knockdown decreased the levels of polyamine metabolites. Consistently, the inhibitory effect on HCC phenotype by HIGD1A silencing could be reversed by overexpression of c-Myc or supplementation of polyamines. CONCLUSIONS: Our results demonstrated that HIGD1A activated c-Myc-ODC1 nexus to regulate polyamine synthesis and to promote HCC survival and malignant phenotype, implying that HIGD1A might represent a novel therapeutic target for HCC.

Expression of ornithine decarboxylase in peripheral blood mononuclear cells from patients with pancreatic adenocarcinoma: A preliminary report.

Ductal adenocarcinoma represents 90-95% of pancreatic cancer (PC) cases and it is an aggressive disease with asymptomatic evolution at early stages, non-specific symptoms and a typical late diagnosis with a 5-year survival rate estimated to be 8%. A window of opportunity lies in early diagnosis as there are currently no reliable biomarkers. CA 19-9 is one of the most frequently used biomarkers of PC, with 75 and 77.6% sensitivity (Se) and specificity (Sp), respectively, and the carcinoembryonic antigen (CEA) shows 39.5 and 81.3% of Se and Sp, respectively. A case-control study was conducted including adult patients with a histological diagnosis of PC (n=11) without previous treatment at the Oncology Service of the CMNO-IMSS between 2019 and 2020, and a control group of adult volunteers (n=11) who were clinically healthy or with controlled disease including hypertension, hypothyroidism and diabetes. Clinical, laboratory and sociodemographic data as well as blood, urine and saliva samples were collected following patient consent. Polyamines were quantified using high-performance liquid chromatography with fluorescence detection, CA 19-9 and CEA were evaluated using enzyme-linked immunosorbent assay, and the protein expression of ornithine decarboxylase (ODC) was evaluated using western blotting. Polyamine metabolism and modulation by means of ODC were increased in the serum and saliva of patients with PC, and the expression of ODC alone was increased in peripheral blood mononuclear cells (PBMCs). The present study focused on the evaluation of putrescine, spermine, spermidine and ODC in PBMCs associated with CA 19-9 and CEA as an auxiliary tool in PC diagnosis.

Polyamine Metabolism for Drug Intervention in Trypanosomatids.

Neglected tropical diseases transmitted by trypanosomatids include three major human scourges that globally affect the world's poorest people: African trypanosomiasis or sleeping sickness, American trypanosomiasis or Chagas disease and different types of leishmaniasis. Different metabolic pathways have been targeted to find antitrypanosomatid drugs, including polyamine metabolism. Since their discovery, the naturally occurring polyamines, putrescine, spermidine and spermine, have been considered important metabolites involved in cell growth. With a complex metabolism involving biosynthesis, catabolism and interconversion, the synthesis of putrescine and spermidine was targeted by thousands of compounds in an effort to produce cell growth blockade in tumor and infectious processes with limited success. However, the discovery of eflornithine (DFMO) as a curative drug against sleeping sickness encouraged researchers to develop new molecules against these diseases. Polyamine synthesis inhibitors have also provided insight into the peculiarities of this pathway between the host and the parasite, and also among different trypanosomatid species, thus allowing the search for new specific chemical entities aimed to treat these diseases and leading to the investigation of target-based scaffolds. The main molecular targets include the enzymes involved in polyamine biosynthesis (ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine synthase), enzymes participating in their uptake from the environment, and the enzymes involved in the redox balance of the parasite. In this review, we summarize the research behind polyamine-based treatments, the current trends, and the main challenges in this field.

Myricetin 3-rhamnoside retards the proliferation of hormone-independent breast cancer cells by targeting hyaluronidase.

Breast cancer is the second-leading cause of cancer-related death in women and the most often diagnosed malignancy. As the majority of chemotherapeutic medications are associated with recurrence, drug resistance, and side effects, scientists are shifting to beneficial agents for prevention and treatment, such as natural molecules. Myricetin 3-rhamnoside, a natural flavonol glycoside is known for diverse pharmacological activities but fewer reports describe the antiproliferative ability. The study aims to investigate the antiproliferative efficacy and target [hyaluronidase (HYAL) and ornithine decarboxylase (ODC), two poor breast cancer prognostic markers] modulatory potential of myricetin 3-rhamnoside on breast cancer cell lines using cytotoxicity assays and in silico docking, molecular dynamics analysis, cell-free and cell-based test methods. Myricetin 3-rhamnoside significantly retard the growth of MDA-MB-231 cells in SRB (IC50 88.64 ± 7.14 µM) and MTT (56.26 ± 8.50 µM) assay. It suppressed the transition of cells to the S-phase by inducing arrest in the G0/G1 phase with a fold change of 1.10. It shows robust binding interaction with ODC (-7.90 kcal/mol) and HYAL (-9.46 kcal/mol) and inhibits ODC (15.22 ± 2.61 µM) and HYAL (11.92 ± 2.89 µM) activity, but in a cell-based assay, the prominent response was observed against HYAL (21.46 ± 4.03 µM). Besides, it shows a 1.38 fold-down regulation of HYAL and forms a stable complex with HYAL. The binding pocket for myricetin 3-rhamnoside and the simulation pocket during the simulation are identical, indicating that myricetin 3-rhamnoside is actively blocking hyaluronidase. The computational prediction suggests it is a safe molecule. These observations imply that myricetin 3-rhamnoside could be used as a pharmacophore to design and synthesize a novel and safe agent for managing hormone-independent breast cancer.Communicated by Ramaswamy H. Sarma.

Characterization and Mechanism of Tea Polyphenols Inhibiting Biogenic Amine Accumulation in Marinated Spanish Mackerel.

Putrescine is a low-molecular-weight organic compound that is widely found in pickled foods. Although the intake of biogenic amines is beneficial to humans, an excessive intake can cause discomfort. In this study, the ornithine decarboxylase gene (ODC) was involved in putrescine biosynthesis. After cloning, expression and functional verification, it was induced and expressed in E. coli BL21 (DE3). The relative molecular mass of the recombinant soluble ODC protein was 14.87 kDa. The function of ornithine decarboxylase was analyzed by determining the amino acid and putrescine content. The results show that the ODC protein could catalyze the decarboxylation of ornithine to putrescine. Then, the three-dimensional structure of the enzyme was used as a receptor for the virtual screening of inhibitors. The binding energy of tea polyphenol ligands to the receptor was the highest at -7.2 kcal mol-1. Therefore, tea polyphenols were added to marinated fish to monitor the changes in putrescine content and were found to significantly inhibit putrescine production (p < 0.05). This study lays the foundation for further research on the enzymatic properties of ODC and provides insight into an effective inhibitor for controlling the putrescine content in pickled fish.

p53 inhibits the Urea cycle and represses polyamine biosynthesis in glioma cell lines.

Glioma is the most common malignant tumor of the central nervous system. The urea cycle (UC) is an essential pathway to convert excess nitrogen and ammonia into the less toxic urea in humans. However, less is known about the functional significance of the urea cycle in glioma. p53 functions as a tumor suppressor and modulates several cellular functions and disease processes. In the present study, we aimed to explore whether p53 influences glioma progression by regulating the urea cycle. Here, we demonstrated the inhibitory impact of p53 on the expression of urea cycle enzymes and urea genesis in glioma cells. The level of polyamine, a urea cycle metabolite, was also regulated by p53 in glioma cells. Carbamoyl phosphate synthetase-1 (CPS1) is the first key enzyme involved in the urea cycle. Functionally, we demonstrated that CPS1 knockdown suppressed glioma cell proliferation, migration and invasion. Mechanistically, we demonstrated that the expression of ornithine decarboxylase (ODC), which determines the generation of polyamine, was regulated by CPS1. In addition, the impacts of p53 knockdown on ODC expression, glioma cell growth and aggressive phenotypes were significantly reversed by CPS1 inhibition. In conclusion, these results demonstrated that p53 inhibits polyamine metabolism by suppressing the urea cycle, which inhibits glioma progression.

Improvement of dermatological symptoms in patients with Bachmann-Bupp syndrome using difluoromethylornithine treatment.

Bachmann-Bupp syndrome (OMIM #619075) is a novel autosomal dominant disorder caused by variants in the c-terminus of the ornithine decarboxylase 1 gene, resulting in increased levels of ornithine decarboxylase. This case report includes two patients diagnosed with Bachmann-Bupp syndrome who were treated with difluoromethylornithine through compassionate use approval from the United States Food and Drug Administration. In both patients, treatment with difluoromethylornithine has resulted in improved dermatologic signs, including regrowth of eyebrow and scalp hair and cessation of recurrent follicular cyst development.

DMSO-tolerant ornithine decarboxylase (ODC) tandem assay optimised for high-throughput screening.

Ornithine decarboxylase (ODC), the first rate-limiting enzyme in polyamine synthesis, has emerged as a therapeutic target for cancer and Alzheimer's disease (AD). To inhibit ODC, α-difluoromethylornithine (DFMO), an irreversible ODC inhibitor, has been widely used. However, due to its poor pharmacokinetics, the need for discovery of better ODC inhibitors is inevitable. For high-throughput screening (HTS) of ODC inhibitors, an ODC enzyme assay using supramolecular tandem assay has been introduced. Nevertheless, there has been no study utilising the ODC tandem assay for HTS, possibly due to its intolerability to dimethyl sulfoxide (DMSO), a common amphipathic solvent used for drug libraries. Here we report a DMSO-tolerant ODC tandem assay in which DMSO-dependent fluorescence quenching becomes negligible by separating enzyme reaction and putrescine detection. Furthermore, we optimised human cell-line-based mass production of ODC for HTS. Our newly developed assay can be a crucial first step in discovering more effective ODC modulators than DFMO.

MicroRNA-378a-3p prevents initiation and growth of colorectal cancer by fine tuning polyamine synthesis.

BACKGROUND: Inhibitors of ornithine decarboxylase (ODC) are effective at preventing colorectal cancer (CRC). However, their high toxicity limits their clinical application. This study was aimed to explore the potential of microRNAs (miRNAs) as an inhibitor of ODC. METHODS: miRNA array was used to identify dysregulated miRNAs in CRC tumors of mice and patients. Azoxymethane (AOM)/Dextran Sodium Sulfate (DSS) were used to induce CRC in mice. miRNA function in carcinogenesis was determined by soft-agar colony formation, flow cytometry, and wound healing of CRC cells. Mini-circle was used to deliver miRNA into colons. RESULTS: MiRNA profiling identified miR-378a-3p (miR-378a) as the most reduced miRNA in CRC tumors of patients and mice treated with AOM/DSS. Pathway array analysis revealed that miR-378a impaired c-MYC and ODC1 pathways. Further studies identified FOXQ1 (forkhead box Q1) and ODC1 as two direct targets of miR-378a. FOXQ1 activated transcription of c-MYC, a transcription activator of ODC1. In addition to directly targeting ODC1, miR-378a also inhibited expression of ODC1 via the FOXQ1-cMYC axis, thereby inhibiting polyamine synthesis in human CRC cells. Phenotypically, by reducing polyamine synthesis, miR-378a induced apoptosis and inhibited proliferation and migration of CRC cells, while disrupting the association of miR-378a with FOXQ1 and ODC1 offset the effects of miR-378a, suggesting that FOXQ1 and ODC1 were required for miR-378a to inhibit CRC cell growth. MiR-378a treatment robustly prevented growth of HCC by inhibiting polyamine synthesis in AOM/DSS mice. CONCLUSION: MiR-378a prevents CRC by inhibiting polyamine synthesis, suggesting its use as a novel ODC inhibitor against CRC.

Hypusinated eIF5A Promotes Ribosomal Frameshifting during Decoding of ODC Antizyme mRNA in Saccharomyces cerevisiae.

Polyamines are essential biogenic poly-cations with important roles in many cellular processes and diseases such as cancer. A rate-limiting step early in the biosynthesis of polyamines is the conversion of ornithine to putrescine by the homodimeric enzyme ornithine decarboxylase (ODC). In a conserved mechanism of posttranslational regulation, ODC antizyme (OAZ) binds to ODC monomers promoting their ubiquitin-independent degradation by the proteasome. Decoding of OAZ mRNA is unusual in that it involves polyamine-regulated bypassing of an internal translation termination (STOP) codon by a ribosomal frameshift (RFS) event. Using Saccharomyces cerevisiae, we earlier showed that high polyamine concentrations lead to increased efficiency of OAZ1 mRNA translation by binding to nascent Oaz1 polypeptide. The binding of polyamines prevents stalling of the ribosomes on OAZ1 mRNA caused by nascent Oaz1 polypeptide thereby promoting synthesis of full-length Oaz1. Polyamine depletion, however, also inhibits RFS during the decoding of constructs bearing the OAZ1 shift site lacking sequences encoding the Oaz1 parts implicated in polyamine binding. Polyamine depletion is known to impair hypusine modification of translation factor eIF5A. Using a novel set of conditional mutants impaired in the function of eIF5A/Hyp2 or its hypusination, we show here that hypusinated eIF5A is required for efficient translation across the OAZ1 RFS site. These findings identify eIF5A as a part of Oaz1 regulation, and thereby of polyamine synthesis. Additional experiments with DFMO, however, show that depletion of polyamines inhibits translation across the OAZ1 RFS site not only by reducing Hyp2 hypusination, but in addition, and even earlier, by affecting RFS more directly.

Targeting Myocardial Mitochondria-STING-Polyamine Axis Prevents Cardiac Hypertrophy in Chronic Kidney Disease.

Chronic kidney disease (CKD) is well recognized as a distinct contributor to cardiac hypertrophy, while the underlying mechanism remains incompletely understood. Here, the authors show that myocardial mitochondrial oxidative damage is early and prominent in CKD and distinctively stimulates the STING-NFκB pathway by releasing mitochondrial DNA to drive cardiac hypertrophy. Furthermore, the authors reveal that ornithine decarboxylase (ODC1)-putrescine metabolic flux is transactivated by NFκB and is required for the STING-NFκB pathway to drive cardiac hypertrophy. Finally, genetic or pharmacologic inhibition of the myocardial mitochondria-STING-NFκB-ODC1 axis significantly prevents CKD-associated cardiac hypertrophy. Therefore, targeting the myocardial mitochoandria-STING-NFκB-ODC1 axis is a promising therapeutic strategy for cardiac hypertrophy in patients with CKD.

Polyamine Metabolism in Leishmania Parasites: A Promising Therapeutic Target.

Parasites of the genus Leishmania cause a variety of devastating and often fatal diseases in humans and domestic animals worldwide. The need for new therapeutic strategies is urgent because no vaccine is available, and treatment options are limited due to a lack of specificity and the emergence of drug resistance. Polyamines are metabolites that play a central role in rapidly proliferating cells, and recent studies have highlighted their critical nature in Leishmania. Numerous studies using a variety of inhibitors as well as gene deletion mutants have elucidated the pathway and routes of transport, revealing unique aspects of polyamine metabolism in Leishmania parasites. These studies have also shed light on the significance of polyamines for parasite proliferation, infectivity, and host-parasite interactions. This comprehensive review article focuses on the main polyamine biosynthetic enzymes: ornithine decarboxylase, S-adenosylmethionine decarboxylase, and spermidine synthase, and it emphasizes recent discoveries that advance these enzymes as potential therapeutic targets against Leishmania parasites.

Carvacrol Arrests the Proliferation of Hypopharyngeal Carcinoma Cells by Suppressing Ornithine Decarboxylase and Hyaluronidase Activities.

Carvacrol, a monoterpene known for its pharmacological activities, is present in the essential oil of Origanum majorana, Origanum vulgare, Thymus vulgaris, and Lippia graveolens. It is used in food as a flavoring and preservative agent in cosmetics and medicines because of its useful bioactivities in clinical practice. However, carvacrol was not much explored for its anticancer potential. Targeting enzymes involved in carcinogenesis, such as ornithine decarboxylase (ODC), cyclooxygenase-2 (COX-2), lipoxygenase-5 (LOX-5), and hyaluronidase (HYAL) by monoterpenes are amongst the efficient approaches for cancer prevention and treatment. In this study, the efficacy of carvacrol was investigated against deregulated cancer biomarkers/targets in organ-specific human cancer cell lines (FaDu, K562, and A549) utilizing in vitro, in silico, and in vivo approaches. The efficacy of carvacrol was evaluated on human cancer cell lines using neutral red uptake (NRU), sulpho rhodamine B (SRB), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. The mechanistic study was carried out in cell-based test systems. Further, the potency of carvacrol was confirmed by the quantitative real-time PCR analysis and molecular docking studies. The in vivo anti-tumor potential of carvacrol was performed on mice S-180 model, and the toxicity examination was accomplished through in silico approach. Carvacrol significantly impeded the growth of FaDu, K562, and A549 cell lines with IC50 values ranging from 9.61 ± 0.05 to 81.32 ± 11.83 µM. Further, the efficacy of carvacrol was explored against different cancer targets in FaDu, K562, and A549 cell lines. Carvacrol inhibits the ODC, COX-2, LOX-5, and HYAL activities in FaDu cell line and ODC, COX-2, and HYAL activities in K562 cell line. The results were validated by expression analysis revealing the downregulation of the targeted gene with a significant change in the transcript level of ODC and HYAL in FaDu cell line with a fold change of 1.56 and 1.61, respectively. A non-significant effect of carvacrol was observed on the downstream signaling pathway of PI3K and HIF-1α/vascular endothelial growth factor (VEGF) in FaDu cells. The cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and Annexin V-fluorescein isothiocyanate (FITC) experiments demonstrate that carvacrol induces apoptosis of FaDu cells. Further, the potency of carvacrol was also evaluated in vivo on mice S-180 tumor model, wherein it inhibits tumor growth (72%) at 75 mg/kg body weight (bw). ADMET studies predicted carvacrol as a safe molecule. Overall, carvacrol delayed the growth of FaDu, K562, and A549 cell lines by targeting enzymes involved in the carcinogenesis process. The existence of one hydroxyl group at the para position of carvacrol could be responsible for the anti-proliferative activity. Thus, carvacrol could be used as a pharmacophore to develop a safe and effective multi-targeted anti-cancer medicament.

Human Decidual Mesenchymal Stem Cells Obtained From Early Pregnancy Improve Cardiac Revascularization Postinfarction by Activating Ornithine Metabolism.

BACKGROUND: Compared with bone marrow mesenchymal stem cells (BMSCs), decidual mesenchymal stem cells (DMSCs) are easy to obtain and exhibit excellent angiogenic effects, but their role in cell transplantation after myocardial infarction (MI) remains unclear. METHODS: BMSCs and DMSCs were harvested from healthy donors. The effects of both cell types on angiogenesis were observed in vitro. Metabonomics analysis was performed to compare different metabolites and screen critical metabolic pathways. A murine model of acute myocardial infarction (AMI) was established, which was randomized into five groups (control, BMSC, DMSC, DMSC + ODCshRNA and BMSC + ODC consisting of 50 animals, equally divided into each group). The therapeutic effect of DMSCs on MI in rats was assessed based on neovascularization and cardiac remodeling. RESULTS: DMSCs exhibited a better angiogenic effect on human umbilical vein endothelial cells (HUVECs) than BMSCs in vitro. In addition, ornithine metabolism, which is associated with vascularization, was significantly increased in DMSCs. The transplantation of DMSCs in the rat MI model significantly enhanced angiogenesis of the infarct border area and improved cardiac remodeling and dysfunction postinfarction compared with BMSCs. Furthermore, inhibition of ornithine metabolism by silencing ornithine decarboxylase (ODC) in DMSCs partly abolished the benefits of DMSC transplantation. CONCLUSION: Compared with BMSCs, DMSCs exhibited better efficacy in improving revascularization and heart remodeling post-MI via the activation of ODC-associated ornithine metabolism.

Inhibitory Effect of Ursolic Acid on the Migration and Invasion of Doxorubicin-Resistant Breast Cancer.

The cause of death in most breast cancer patients is disease metastasis and the occurrence of multidrug resistance (MDR). Ornithine decarboxylase (ODC), which is involved into multiple pathways, is closely related to carcinogenesis and development. Ursolic acid (UA), a natural triterpenoid compound, has been shown to reverse the MDR characteristics of tumor cells. However, the effect of UA on the invasion and metastasis of tumor cells with MDR is not known. Therefore, we investigated the effects of UA on invasion and metastasis, ODC-related polyamine metabolism, and MAPK-Erk-VEGF/MMP-9 signaling pathways in a doxorubicin-resistant breast cancer cell (MCF-7/ADR) model. The obtained results showed that UA significantly inhibited the adhesion and migration of MCF-7/ADR cells, and had higher affinities with key active cavity residues of ODC compared to the known inhibitor di-fluoro-methyl-ornithine (DFMO). UA could downregulate ODC, phosphorylated Erk (P-Erk), VEGF, and matrix metalloproteinase-9 (MMP-9) activity. Meanwhile, UA significantly reduced the content of metabolites of the polyamine metabolism. Furthermore, UA increased the intracellular accumulation of Dox in MCF-7/ADR cells. Taken together, UA can inhibit against tumor progression during the treatment of breast cancer with Dox, and possibly modulate the Erk-VEGF/MMP-9 signaling pathways and polyamine metabolism by targeting ODC to exert these effects.

Ornithine decarboxylase functions in both autophagy and apoptosis in response to ultraviolet B radiation injury.

We present a mechanism for how ornithine decarboxylase (ODC) regulates the crosstalk between autophagy and apoptosis. In cancer cells, low-intensity ultraviolet B (UVBL ) induces autophagy while high-intensity UVB (UVBH ) induces apoptosis. Overexpression of ODC decreases UVBL -induced autophagy by inhibiting Atg5-Atg12 conjugation and suppressing the expression of autophagy markers LC3, Atg7, Atg12, and BECN1 proteins. In contrast, when ODC-overexpressing cells are exposed to UVBH radiation, the levels of LC3-II, Atg5-Atg12 conjugate, BECN1, Atg7, and Atg12 increase, while the apoptosis marker cleaved-PARP proteins decrease, indicating that ODC overexpression induced UVBH -induced autophagy but inhibited UVBH -induced cellular apoptosis. Additionally, when exposed to UVBH radiation, silencing BECN1, Atg5, and Atg12 genes results in a decrease in the level of LC3-II proteins but an increase in the level of cleaved-PARP proteins, and apoptotic bodies were significantly increased while autophagosomes were significantly decreased. These findings imply that ODC inhibits apoptosis in cells via the autophagy pathway. The role of Atg12 in ODC-overexpressing cells exposed to UVBH radiation is investigated using site-directed mutagenesis. Our results indicate that the Atg12-D111S mutant has increased cell survival. The Atg12-ΔG186 mutant impairs autophagy and enhances apoptosis. We demonstrate that when ODC-overexpressing cells are silenced for the Atg12 protein, autophagy and apoptosis are strongly affected, and ODC-induced autophagy protects against UVBH -induced apoptosis via the Atg12 protein.

Genome wide survey, and expression analysis of Ornithine decarboxylase gene associated with alkaloid biosynthesis in plants.

Plant ODC (ornithine decarboxylase) plays a vital role in normalizing cell division in actively growing tissues. The ODC is a key precursor enzyme for nicotine and nornicotine biosynthesis in plants. ODCs are widely present in many plant families but have not been functionally validated and characterized at the molecular level. In the present study, 58 plant ODCs were identified and were found to contain two putative regulatory motifs, specifically PLP (Pyridoxal 5'-phosphate) and Orn/DAP/Arg decarboxylase family 2 pyridoxal-phosphate, that are highly conserved among diverse plant species. Further, the cis-regulatory elements and interacting partners of the gene revealed the importance of ODC in various metabolic pathways. The qRT-PCR revealed highest relative expression of ODC in floral meristem and roots. Our results suggest that ODC can be effectively used as an ideal candidate for engineering polyamine biosynthesis and would be crucial for developing ultra-low nicotine content tobacco lines via genome editing.

Structural basis of binding and inhibition of ornithine decarboxylase by 1-amino-oxy-3-aminopropane.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme for the synthesis of polyamines (PAs). PAs are oncometabolites that are required for proliferation, and pharmaceutical ODC inhibition is pursued for the treatment of hyperproliferative diseases, including cancer and infectious diseases. The most potent ODC inhibitor is 1-amino-oxy-3-aminopropane (APA). A previous crystal structure of an ODC-APA complex indicated that APA non-covalently binds ODC and its cofactor pyridoxal 5-phosphate (PLP) and functions by competing with the ODC substrate ornithine for binding to the catalytic site. We have revisited the mechanism of APA binding and ODC inhibition through a new crystal structure of APA-bound ODC, which we solved at 2.49 Šresolution. The structure unambiguously shows the presence of a covalent oxime between APA and PLP in the catalytic site, which we confirmed in solution by mass spectrometry. The stable oxime makes extensive interactions with ODC but cannot be catabolized, explaining APA's high potency in ODC inhibition. In addition, we solved an ODC/PLP complex structure with citrate bound at the substrate-binding pocket. These two structures provide new structural scaffolds for developing more efficient pharmaceutical ODC inhibitors.