Difluoromethylornithine in cancer: new advances

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.

A Contemporary Review on the Critical Role of Nonsteroidal Anti-inflammatory Agents in Colorectal Cancer Therapy

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) are widely recognized as effective pain relievers and function by inhibiting the cyclooxygenase enzyme (COXs). Moreover, they have been found to participate in various cellular processes through different signaling pathways, such as WNT, MAPK, NF-κB, and PI3K/AKT/mTOR. This makes them potential candidates for chemoprevention of several malignancies, particularly colorectal cancer (CRC). However, the use of NSAIDs in cancer prevention and treatment is a complex issue due to their adverse effects and gastrointestinal toxicity. Therefore, it is crucial to explore combination therapies that can minimize side effects while maximizing synergistic effects with other agents and to evaluate the success rate of such approaches in both pre-clinical and clinical studies. In this review, we aim to provide an overview of the effects of NSAIDs in the prevention and treatment of CRC. We will focus on elucidating the possible mechanisms of action of these drugs, the signaling pathways involved in CRC, and the potential synergistic effects when combined with other therapeutic agents.

Polyamine Dysregulation and Nucleolar Disruption in Alzheimer's Disease

A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli. Polyamines are essential in nucleolar functions, such as RNA folding and ribonucleoprotein assembly. Changes in the nucleolar pool of anionic RNA and cationic polyamines acting as counterions can cause significant nucleolar dynamics. Polyamine synthesis reduces S-adenosylmethionine which, at low levels, triggers tau phosphorylation. Also, polyamine recycling reduces acetyl-CoA needed for acetylcholine, which is low in Alzheimer's disease. Extraordinary nucleolar expansion and/or contraction can disrupt epigenetic control in peri-nucleolar chromatin, such as chromosome 14 with the presenilin-1 gene; chromosome 21 with the amyloid precursor protein gene; chromosome 17 with the tau gene; chromosome 19 with the APOE4 gene; and the inactive X chromosome (Xi; aka "nucleolar satellite") with normally silent spermine synthase (polyamine synthesis) and spermidine/spermine-N1-acetyltransferase (polyamine recycling) alleles. Chromosomes 17, 19 and the Xi have high concentrations of Alu elements which can be transcribed by RNA polymerase III if positioned nucleosomes are displaced from the Alu elements. A sudden flood of Alu RNA transcripts can competitively bind nucleolin which is usually bound to Alu sequences in structural RNAs that stabilize the nucleolar heterochromatic shell. This Alu competition leads to loss of nucleolar integrity with leaking of nucleolar polyamines that cause aggregation of phosphorylated tau. The hypothesis was developed with key word searches (e.g., PubMed) using relevant terms (e.g., Alzheimer's, lupus, nucleolin) based on a systems biology approach and exploring autoimmune disease tautology, gaining synergistic insights from other diseases.

Eflornithine as Postimmunotherapy Maintenance in High-Risk Neuroblastoma: Externally Controlled, Propensity Score-Matched Survival Outcome Comparisons

PURPOSE

Long-term survival in high-risk neuroblastoma (HRNB) is approximately 50%, with mortality primarily driven by relapse. Eflornithine (DFMO) to reduce risk of relapse after completion of immunotherapy was investigated previously in a single-arm, phase II study (NMTRC003B; ClinicalTrials.gov identifier: NCT02395666) that suggested improved event-free survival (EFS) and overall survival (OS) compared with historical rates in a phase III trial (Children Oncology Group ANBL0032; ClinicalTrials.gov identifier: NCT00026312). Using patient-level data from ANBL0032 as an external control, we present new analyses to further evaluate DFMO as HRNB postimmunotherapy maintenance.

PATIENTS AND METHODS

NMTRC003B (2012-2016) enrolled patients with HRNB (N = 141) after standard up-front or refractory/relapse treatment who received up to 2 years of continuous treatment with oral DFMO (750 ± 250 mg/m2 twice a day). ANBL0032 (2001-2015) enrolled patients with HRNB postconsolidation, 1,328 of whom were assigned to dinutuximab (ch.14.18) treatment. Selection rules identified 92 NMTRC003B patients who participated in (n = 87) or received up-front treatment consistent with (n = 5) ANBL0032 (the DFMO/treated group) and 852 patients from ANBL0032 who could have been eligible for NMTRC003B after immunotherapy, but did not enroll (the NO-DFMO/control group). The median follow-up time for DFMO/treated patients was 6.1 years (IQR, 5.2-7.2) versus 5.0 years (IQR, 3.5-7.0) for NO-DFMO/control patients. Kaplan-Meier and Cox regression compared EFS and OS for overall groups, 3:1 (NO-DFMO:DFMO) propensity score-matched cohorts balanced on 11 baseline demographic and disease characteristics with exact matching on MYCN, and additional sensitivity analyses.

RESULTS

DFMO after completion of immunotherapy was associated with improved EFS (hazard ratio [HR], 0.50 [95% CI, 0.29 to 0.84]; P = .008) and OS (HR, 0.38 [95% CI, 0.19 to 0.76]; P = .007). The results were confirmed with propensity score-matched cohorts and sensitivity analyses.

CONCLUSION

The externally controlled analyses presented show a relapse risk reduction in patients with HRNB treated with postimmunotherapy DFMO.

Plasmonic Functional Assay Platform Determines the Therapeutic Profile of Cancer Cells

Functional assay platforms could identify the biophysical properties of cells and their therapeutic response to drug treatments. Despite their strong ability to assess cellular pathways, functional assays require large tissue samples, long-term cell culture, and bulk measurements. Even though such a drawback is still valid, these limitations did not hinder the interest in these platforms for their capacity to reveal drug susceptibility. Some of the limitations could be overcome with single-cell functional assays by identifying subpopulations using small sample volumes. Along this direction, in this article, we developed a high-throughput plasmonic functional assay platform to identify the growth profile of cells and their therapeutic profile under therapies using mass and growth rate statistics of individual cells. Our technology could determine populations' growth profiles using the growth rate data of multiple single cells of the same population. Evaluating spectral variations based on the plasmonic diffraction field intensity images in real time, we could simultaneously monitor the mass change for the cells within the field of view of a camera with the capacity of > ∼500 cells/h scanning rate. Our technology could determine the therapeutic profile of cells under cancer drugs within few hours, while the classical techniques require days to show reduction in viability due to antitumor effects. The platform could reveal the heterogeneity within the therapeutic profile of populations and determine subpopulations showing resistance to drug therapies. As a proof-of-principle demonstration, we studied the growth profile of MCF-7 cells and their therapeutic behavior to standard-of-care drugs that have antitumor effects as shown in the literature, including difluoromethylornithine (DFMO), 5-fluorouracil (5-FU), paclitaxel (PTX), and doxorubicin (Dox). We successfully demonstrated the resistant behavior of an MCF-7 variant that could survive in the presence of DFMO. More importantly, we could precisely identify synergic and antagonistic effects of drug combinations based on the order of use in cancer therapy. Rapidly assessing the therapeutic profile of cancer cells, our plasmonic functional assay platform could be used to reveal personalized drug therapies for cancer patients.

Ototoxicity of Long-Term α-Difluoromethylornithine for Skin Cancer Prevention

OBJECTIVE

Evaluate the effects of α-difluoromethylornithine (DFMO) on hearing thresholds as part of a randomized, double-blind, placebo-controlled trial.

METHODS

Subjects were randomized and assigned to the control (placebo) or experimental (DFMO) group. DFMO or placebo were administered orally (500 mg/m2 /day) for up to 5 years.

RESULTS

Subjects taking DFMO had, on average, increased hearing thresholds from baseline across the frequency range compared to subjects in the control group. Statistical analysis revealed this was significant in the lower frequency range.

CONCLUSIONS

This randomized controlled trial revealed the presence of increased hearing thresholds associated with long-term DFMO use. As a whole, DFMO may help prevent and treat certain types of cancers; however, it can result in some degree of hearing loss even when administered at low doses. This study further highlights the importance of closely monitoring hearing thresholds in subjects taking DFMO. Laryngoscope, 133:676-682, 2023.

Gasdermin D Deficiency in Vascular Smooth Muscle Cells Ameliorates Abdominal Aortic Aneurysm Through Reducing Putrescine Synthesis

Abdominal aortic aneurysm (AAA) is a common vascular disease associated with significant phenotypic alterations in vascular smooth muscle cells (VSMCs). Gasdermin D (GSDMD) is a pore-forming effector of pyroptosis. In this study, the role of VSMC-specific GSDMD in the phenotypic alteration of VSMCs and AAA formation is determined. Single-cell transcriptome analyses reveal Gsdmd upregulation in aortic VSMCs in angiotensin (Ang) II-induced AAA. VSMC-specific Gsdmd deletion ameliorates Ang II-induced AAA in apolipoprotein E (ApoE)^-/- mice. Using untargeted metabolomic analysis, it is found that putrescine is significantly reduced in the plasma and aortic tissues of VSMC-specific GSDMD deficient mice. High putrescine levels trigger a pro-inflammatory phenotype in VSMCs and increase susceptibility to Ang II-induced AAA formation in mice. In a population-based study, a high level of putrescine in plasma is associated with the risk of AAA (p < 2.2 × 10^-16 ), consistent with the animal data. Mechanistically, GSDMD enhances endoplasmic reticulum stress-C/EBP homologous protein (CHOP) signaling, which in turn promotes the expression of ornithine decarboxylase 1 (ODC1), the enzyme responsible for increased putrescine levels. Treatment with the ODC1 inhibitor, difluoromethylornithine, reduces AAA formation in Ang II-infused ApoE^-/- mice. The findings suggest that putrescine is a potential biomarker and target for AAA treatment.

Druggable Metabolic Vulnerabilities Are Exposed and Masked during Progression to Castration Resistant Prostate Cancer

There is an urgent need for exploring new actionable targets other than androgen receptor to improve outcome from lethal castration-resistant prostate cancer. Tumor metabolism has reemerged as a hallmark of cancer that drives and supports oncogenesis. In this regard, it is important to understand the relationship between distinctive metabolic features, androgen receptor signaling, genetic drivers in prostate cancer, and the tumor microenvironment (symbiotic and competitive metabolic interactions) to identify metabolic vulnerabilities. We explore the links between metabolism and gene regulation, and thus the unique metabolic signatures that define the malignant phenotypes at given stages of prostate tumor progression. We also provide an overview of current metabolism-based pharmacological strategies to be developed or repurposed for metabolism-based therapeutics for castration-resistant prostate cancer.

Recent Advances in Fluorescent Methods for Polyamine Detection and the Polyamine Suppressing Strategy in Tumor Treatment

The biogenic aliphatic polyamines (spermine, spermidine, and putrescine) are responsible for numerous cell functions, including cell proliferation, the stabilization of nucleic acid conformations, cell division, homeostasis, gene expression, and protein synthesis in living organisms. The change of polyamine concentrations in the urine or blood is usually related to the presence of malignant tumors and is regarded as a biomarker for the early diagnosis of cancer. Therefore, the detection of polyamine levels in physiological fluids can provide valuable information in terms of cancer diagnosis and in monitoring therapeutic effects. In this review, we summarize the recent advances in fluorescent methods for polyamine detection (supramolecular fluorescent sensing systems, fluorescent probes based on the chromophore reaction, fluorescent small molecules, and fluorescent nanoparticles). In addition, tumor polyamine-suppressing strategies (such as polyamine conjugate, polyamine analogs, combinations that target multiple components, spermine-responsive supramolecular chemotherapy, a combination of polyamine consumption and photodynamic therapy, etc.) are highlighted. We hope that this review promotes the development of more efficient polyamine detection methods and provides a comprehensive understanding of polyamine-based tumor suppressor strategies.

Methyl Group Metabolism in Differentiation, Aging, and Cancer

Methyl group metabolism belongs to a relatively understudied field of research. Its importance lies in the fact that methyl group metabolic pathways are crucial for the successful conversion of dietary nutrients into the basic building blocks to carry out any cellular methylation reaction. Methyl groups play essential roles in numerous cellular functions such as DNA methylation, nucleotide- and protein biosynthesis. Especially, DNA methylation is responsible for organizing the genome into transcriptionally silent and active regions. Ultimately, it is this proper annotation that determines the quality of expression patterns required to ensure and shape the phenotypic integrity and function of a highly specialized cell type. Life is characterized by constantly changing environmental conditions, which are addressed by changes in DNA methylation. This relationship is increasingly coming into focus as it is of fundamental importance for differentiation, aging, and cancer. The stability and permanence of these metabolic processes, fueling the supplementation of methyl groups, seem to be important criteria to prevent deficiencies and erosion of the methylome. Alterations in the metabolic processes can lead to epigenetic and genetic perturbations, causative for diverse disorders, accelerated aging, and various age-related diseases. In recent decades, the intake of methyl group compounds has changed significantly due to, e.g., environmental pollution and food additives. Based on the current knowledge, this review provides a brief overview of the highly interconnected relationship between nutrition, metabolism, changes in epigenetic modifications, cancer, and aging. One goal is to provide an impetus to additionally investigate changes in DNA methylation as a possible consequence of an impaired methyl group metabolism.

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.

Polyamine biosynthesis and eIF5A hypusination are modulated by the DNA tumor virus KSHV and promote KSHV viral infection

Polyamines are critical metabolites involved in various cellular processes and often dysregulated in cancers. Kaposi’s sarcoma-associated Herpesvirus (KSHV), a defined human oncogenic virus, leads to profound alterations of host metabolic landscape to favor development of KSHV-associated malignancies. In our studies, we identified that polyamine biosynthesis and eIF5A hypusination are dynamically regulated by KSHV infection through modulation of key enzymes (ODC1 and DHPS) of these pathways. During KSHV latency, ODC1 and DHPS are upregulated along with increase of hypusinated eIF5A (hyp-eIF5A), while hyp-eIF5A is further induced along with reduction of ODC1 and intracellular polyamines during KSHV lytic reactivation. In return these metabolic pathways are required for both KSHV lytic reactivation and de novo infection. Further analysis unraveled that synthesis of critical KSHV latent and lytic proteins (LANA, RTA) depends on hypusinated-eIF5A. We also demonstrated that KSHV infection can be efficiently and specifically suppressed by inhibitors targeting these pathways. Collectively, our results illustrated that the dynamic and profound interaction of a DNA tumor virus (KSHV) with host polyamine biosynthesis and eIF5A hypusination pathways promote viral propagation, thus defining new therapeutic targets to treat KSHV-associated malignancies.

Understanding virus-host interactions is crucial to develop and improve therapies. Kaposi’s sarcoma associated Herpesvirus (KSHV) is a human gamma-herpesvirus which deeply modulates the host metabolism and is associated with various cancers of endothelial and lymphoid origin. Polyamines are critical metabolites often dysregulated in cancers. In this study we demonstrated KSHV dynamically modulates polyamine metabolism to favor eIF5A hypusination and translation of critical KSHV latent and lytic proteins (LANA, RTA). Consequently, we found KSHV lytic switch from latency and de novo infection were dependent on polyamines and hypusination and pharmacological inhibition efficiently and specifically restricted KSHV infection. Our study provides new insights into KSHV alteration of the host metabolism and describe new therapeutic targets to treat KSHV-associated malignancies.

The Potential Role of Spermine and Its Acetylated Derivative in Human Malignancies

Polyamines are essential biomolecules for normal cellular metabolism in humans. The roles of polyamines in cancer development have been widely discussed in recent years. Among all, spermine alongside with its acetylated derivative, N¹, N¹²-Diacetylspermine, demonstrate a relationship with the diagnosis and staging of various cancers, including lung, breast, liver, colorectal and urogenital. Numerous studies have reported the level of spermine in different body fluids and organ tissues in patients with different types of cancers. Currently, the role and the underlying mechanisms of spermine in cancer development and progression are still under investigation. This review summarized the roles of spermine in cancer development and as a diagnostic, prognostic and therapeutic tool in various cancers.

The eukaryotic initiation factor 5A (eIF5A1), the molecule, mechanisms and recent insights into the pathophysiological roles

Since the demonstration of its involvement in cell proliferation, the eukaryotic initiation factor 5A (eIF5A) has been studied principally in relation to the development and progression of cancers in which the isoform A2 is mainly expressed. However, an increasing number of studies report that the isoform A1, which is ubiquitously expressed in normal cells, exhibits novel molecular features that reveal its new relationships between cellular functions and organ homeostasis. At a first glance, eIF5A can be regarded, among other things, as a factor implicated in the initiation of translation. Nevertheless, at least three specificities: (1) its extreme conservation between species, including plants, throughout evolution, (2) its very special and unique post-translational modification through the activating-hypusination process, and finally (3) its close relationship with the polyamine pathway, suggest that the role of eIF5A in living beings remains to be uncovered. In fact, and beyond its involvement in facilitating the translation of proteins containing polyproline residues, eIF5A is implicated in various physiological processes including ischemic tolerance, metabolic adaptation, aging, development, and immune cell differentiation. These newly discovered physiological properties open up huge opportunities in the clinic for pathologies such as, for example, the ones in which the oxygen supply is disrupted. In this latter case, organ transplantation, myocardial infarction or stroke are concerned, and the current literature defines eIF5A as a new drug target with a high level of potential benefit for patients with these diseases or injuries. Moreover, the recent use of genomic and transcriptomic association along with metadata studies also revealed the implication of eIF5A in genetic diseases. Thus, this review provides an overview of eIF5A from its molecular mechanism of action to its physiological roles and the clinical possibilities that have been recently reported in the literature.

Gut Microbiota-Derived Metabolites in Colorectal Cancer: The Bad and the Challenges

Accumulating evidence from studies in humans and animal models has elucidated that gut microbiota, acting as a complex ecosystem, contributes critically to colorectal cancer (CRC). The potential mechanisms often reported emphasize the vital role of carcinogenic activities of specific pathogens, but in fact, a series of metabolites produced from exogenous dietary substrates or endogenous host compounds occupy a decisive position similarly. Detrimental gut microbiota-derived metabolites such as trimethylamine-N-oxide, secondary bile acids, hydrogen sulfide and N-nitroso compounds could reconstruct the ecological composition and metabolic activity of intestinal microorganisms and formulate a microenvironment that opens susceptibility to carcinogenic stimuli. They are implicated in the occurrence, progression and metastasis of CRC through different mechanisms, including inducing inflammation and DNA damage, activating tumorigenic signaling pathways and regulating tumor immunity. In this review, we mainly summarized the intimate relationship between detrimental gut microbiota-derived metabolites and CRC, and updated the current knowledge about detrimental metabolites in CRC pathogenesis. Then, multiple interventions targeting these metabolites for CRC management were critically reviewed, including diet modulation, probiotics/prebiotics, fecal microbiota transplantation, as well as more precise measures such as engineered bacteria, phage therapy and chemopreventive drugs. A better understanding of the interplay between detrimental microbial metabolites and CRC would hold great promise against CRC.

Polyamine homeostasis-based strategies for cancer: The role of combination regimens

Spermine, spermidine and putrescine polyamines are naturally occurring ubiquitous positively charged amines and are essential metabolites for biological functions in our life. These compounds play a crucial role in many cell processes, including cellular proliferation, growth, and differentiation. Intracellular levels of polyamines depend on their biosynthesis, transport and degradation. Polyamine levels are high in cancer cells, which leads to the promotion of tumor growth, invasion and metastasis. Targeting polyamine metabolism as an anticancer strategy is considerably rational. Due to compensatory mechanisms, a single strategy does not achieve satisfactory clinical effects when using a single agent. Combination regimens are more clinically promising for cancer chemoprevention because they work synergistically with causing little or no adverse effects due to each individual agent being used at lower doses. Moreover, bioactive substances have advantages over single chemical agents because they can affect multiple targets. In this review, we discuss anticancer strategies targeting polyamine metabolism and describe how combination treatments and effective natural active ingredients are promising therapies. The existing research suggests that polyamine metabolic enzymes are important therapeutic targets and that combination therapies can be more effective than monotherapies based on polyamine depletion.

Difluoromethylornithine Induces Apoptosis through Regulation of AP-1 Signaling via JNK Phosphorylation in Epithelial Ovarian Cancer

Difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase (ODC), has promising activity against various cancers and a tolerable safety profile for long-term use as a chemopreventive agent. However, the anti-tumor effects of DFMO in ovarian cancer cells have not been entirely understood. Our study aimed to identify the effects and mechanism of DFMO in epithelial ovarian cancer cells using SKOV-3 cells. Treatment with DFMO resulted in a significantly reduced cell viability in a time- and dose-dependent manner. DFMO treatment inhibited the activity and downregulated the expression of ODC in ovarian cancer cells. The reduction in cell viability was reversed using polyamines, suggesting that polyamine depletion plays an important role in the anti-tumor activity of DFMO. Additionally, significant changes in Bcl-2, Bcl-xL, Bax protein levels, activation of caspase-3, and cleavage of poly (ADP-ribose) polymerase were observed, indicating the apoptotic effects of DFMO. We also found that the effect of DFMO was mediated by AP-1 through the activation of upstream JNK via phosphorylation. Moreover, DFMO enhanced the effect of cisplatin, thus showing a possibility of a synergistic effect in treatment. In conclusion, treatment with DFMO alone, or in combination with cisplatin, could be a promising treatment for ovarian cancer.

Refractive Index Sensing for Measuring Single Cell Growth

Accessing cell growth on adhesive substrates is critical for identifying biophysical properties of cells and their therapeutic response to drug therapies. However, optical techniques have low sensitivity, and their reliability varies with cell type, whereas microfluidic technologies rely on cell suspension. In this paper, we introduced a plasmonic functional assay platform that can precisely measure cell weight and the dynamic change in real-time for adherent cells. Possessing this ability, our platform can determine growth rates of individual cells within only 10 min to map the growth profile of populations in short time intervals. The platform could successfully determine heterogeneity within the growth profile of populations and assess subpopulations exhibiting distinct growth profiles. As a proof of principle, we investigated the growth profile of MCF-7 cells and the effect of two intracellular metabolisms critical for their proliferation. We first investigated the negative effect of serum starvation on cell growth. We then studied ornithine decarboxylase (ODC) activity, a key enzyme which is involved in proliferation, and degraded under low osmolarity that inhibits cell growth. We successfully determined the significant distinction between growth profiles of MCF-7 cells and their ODC-overproducing variants that possess strong resistance to the negative effects of low osmolarity. We also demonstrated that an exogenous parameter, putrescine, could rescue cells from ODC inhibition under hypoosmotic conditions. In addition to the ability of accessing intracellular activities through ex vivo measurements, our platform could also determine therapeutic behaviors of cancer cells in response to drug treatments. Here, we investigated difluoromethylornithine (DFMO), which has antitumor effects on MCF-7 cells by inhibiting ODC activity. We successfully demonstrated the susceptibility of MCF-7 cells to such drug treatment, while its DFMO-resistant subpopulation could survive in the presence of this antigrowth agent. By rapidly determining cell growth kinetics in small samples, our plasmonic platform may be of broad use to basic research and clinical applications.

The First Insight Into the Supramolecular System of D,L-α-Difluoromethylornithine: A New Antiviral Perspective

Targeting the polyamine biosynthetic pathway by inhibiting ornithine decarboxylase (ODC) is a powerful approach in the fight against diverse viruses, including SARS-CoV-2. Difluoromethylornithine (DFMO, eflornithine) is the best-known inhibitor of ODC and a broad-spectrum, unique therapeutical agent. Nevertheless, its pharmacokinetic profile is not perfect, especially when large doses are required in antiviral treatment. This article presents a holistic study focusing on the molecular and supramolecular structure of DFMO and the design of its analogues toward the development of safer and more effective formulations. In this context, we provide the first deep insight into the supramolecular system of DFMO supplemented by a comprehensive, qualitative and quantitative survey of non-covalent interactions via Hirshfeld surface, molecular electrostatic potential, enrichment ratio and energy frameworks analysis visualizing 3-D topology of interactions in order to understand the differences in the cooperativity of interactions involved in the formation of either basic or large synthons (Long-range Synthon Aufbau Modules, LSAM) at the subsequent levels of well-organized supramolecular self-assembly, in comparison with the ornithine structure. In the light of the drug discovery, supramolecular studies of amino acids, essential constituents of proteins, are of prime importance. In brief, the same amino-carboxy synthons are observed in the bio-system containing DFMO. DFT calculations revealed that the biological environment changes the molecular structure of DFMO only slightly. The ADMET profile of structural modifications of DFMO and optimization of its analogue as a new promising drug via molecular docking are discussed in detail.

Dual Inhibition of Ornithine Decarboxylase and A1 Adenosine Receptor Efficiently Suppresses Breast Tumor Cells

Personized treatment of breast cancer is still a challenge, and more treatment options for breast cancer are warranted. Combination therapies have been a highly appreciated strategy for breast cancer treatment in recent years, and the development of new combination therapies could improve patient outcomes. Adenosine and polyamines are both endogenous metabolites with indispensable biological functions. Adenosine binds with the A₁ adenosine receptor (A₁AR) to downregulate cAMP concentration, and both low cAMP content and high polyamine levels stimulate the growth and proliferation of cancer cells. In this work, we initially used a polyamine synthesis inhibitor, DFMO (α-difluoromethylornithine), and an A₁AR inhibitor, DPCPX (8-cyclopentyl-1,3-dipropylxanthine) to investigate if simultaneously inhibiting A₁AR and polyamine synthesis has synergistical antitumor effects. Next, we investigated a dual inhibitor (ODC-MPI-2) of A₁AR and ODC (ornithine decarboxylase 1), the rate-limiting enzyme in polyamine biosynthesis. We investigated if ODC-MPI-2 could inhibit the proliferation and growth of breast cancer cells. Our data showed that DFMO and DPCPX synergistically inhibit the growth and proliferation of MCF-7 cells. We also demonstrated that ODC-MPI-2 reduces cellular polyamine levels and elevates cAMP concentration. We further showed that ODC-MPI-2 inhibits the growth, proliferation, and migration/invasion of MCF-7 cells. Finally, ODC-MPI-2 showed a preference for inhibiting triple-negative breast cancer cells. The dual inhibition of ODC and A₁AR is a new combination therapy strategy for treating breast cancer, and dual inhibitors of ODC and A₁AR may be effective future drugs for treating breast cancer.

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.

Simultaneous Inhibition of Ornithine Decarboxylase 1 and Pyruvate Kinase M2 Exerts Synergistic Effects Against Hepatocellular Carcinoma Cells

Purpose

Previously, we showed that lactate promoted the proliferation and mobility of hepatocellular carcinoma (HCC) cells by increasing the expression of ornithine decarboxylase 1 (ODC1). In this study, we determined the relationship between ODC1 and pyruvate kinase M2 (PKM2, a key lactate metabolism enzyme), and determined the combined effects of difluoromethylornithine (DFMO; an ODC1 inhibitor) and compound 3k (a PKM2 inhibitor) on HCC cells.

Methods

First, the relationship between PKM2 and ODC1 was analyzed using Western blotting, Cell Counting Kit (CCK)-8 assays, transwell assays, bioinformatics, quantitative real-time fluorescent PCR (qRT-PCR), and immunohistochemical staining. Thereafter, the ODC1 inhibitor DFMO and the PKM2 inhibitor compound 3k were employed. Their combined effects on HCC cell proliferation and mobility were evaluated via CCK-8 assay, flow cytometry, a subcutaneous xenograft tumor model in mice, wound healing assays, and transwell assays. Additionally, the effects of DFMO and compound 3k on the epithelial–mesenchymal transition phenotype and the AKT/GSK-3β/β-catenin pathway were explored using Western blotting and immunofluorescence.

Results

PKM2 knockdown significantly decreased the ODC1 expression, and the proliferation and invasion of HCC cells, while ODC1 overexpression reversed the inhibitory effects of PKM2 knockdown. Similarly, inhibition of ODC1 also decreased the expression of PKM2 via reducing the c-myc-induced transcription. PKM2 was co-expressed with ODC1 in HCC samples, while simultaneously upregulated PKM2 and ODC1 led to the poorest survival outcome. DFMO and compound 3k synergistically inhibited HCC cell proliferation, induced apoptosis, and suppressed cell mobility, as well as the EMT phenotype and the AKT/GSK-3β/β-catenin pathway. The AKT activator SC79 reversed the inhibitory effects.

Conclusion

PKM2/ODC1 are involved in a positive feedback loop. The simultaneous inhibition of ODC1 and PKM2 using DFMO and compound 3k exerts synergistic effects against HCC cells via the AKT/GSK-3β/β-catenin pathway. Thus, DFMO combined with compound 3k may be a novel effective strategy for treating HCC.

Polyamine regulation of porcine reproductive and respiratory syndrome virus infection depends on spermidine-spermine acetyltransferase 1

•

Inhibition of polyamine synthesis suppresses PRRSV proliferation.

•

PRRSV infection relies on spermidine and spermine.

•

PRRSV decreases the levels of intracellular polyamines.

•

PRRSV infection increases the mRNA level of SAT1.

•

SAT1 inhibits PRRSV propagation.

Like obligate intracellular parasites, viruses co-opt host cell resources to establish productive infections. Polyamines are key aliphatic molecules that perform important roles in cellular growth and proliferation. They are also needed for the successful multiplication of various viruses. Little is known about the effects of polyamines on Arteriviridae infections. Here, porcine reproductive and respiratory syndrome virus (PRRSV), an economically prominent porcine virus, was used to investigate virus–polyamine interactions. We found that PRRSV infection significantly downregulated the levels of cellular polyamines. Using an inhibitor or specific short interfering RNAs (siRNAs) of ornithine decarboxylase 1, a key anabolic enzyme involved in the classical de novo biosynthesis of polyamines, we found that polyamine depletion abrogated PRRSV proliferation, and this effect was recoverable by adding exogenous spermidine and spermine, but not putrescine to the cells, suggesting that the host inhibits polyamine biosynthesis to restrict PRRSV proliferation. Further analysis revealed that the expression level of spermidine-spermine acetyltransferase 1 (SAT1), a catabolic enzyme that reduces spermidine and spermine levels, was upregulated during PRRSV infection, but conversely, SAT1 had an inhibitory effect on PRRSV reproduction. Our data show that polyamines are important molecules during PRRSV-host interactions, and polyamines and their biosynthetic pathways are potential therapeutic targets against PRRSV infection.

Thymoquinone and Difluoromethylornithine (DFMO) Synergistically Induce Apoptosis of Human Acute T Lymphoblastic Leukemia Jurkat Cells Through the Modulation of Epigenetic Pathways

Thymoquinone (TQ), a natural anticancer agent exerts cytotoxic effects on several tumors by targeting multiple pathways, including apoptosis. Difluoromethylornithine (DFMO), an irreversible inhibitor of the ornithine decarboxylase (ODC) enzyme, has shown promising inhibitory activities in many cancers including leukemia by decreasing the biosynthesis of the intracellular polyamines. The present study aimed to investigate the combinatorial cytotoxic effects of TQ and DFMO on human acute T lymphoblastic leukemia Jurkat cells and to determine the underlying mechanisms. Here, we show that the combination of DFMO and TQ significantly reduced cell viability and resulted in significant synergistic effects on apoptosis when compared to either DFMO or TQ alone. RNA-sequencing showed that many key epigenetic players including Ubiquitin-like containing PHD and Ring finger 1 (UHRF1) and its 2 partners DNA methyltransferase 1 (DNMT1) and histone deacetylase 1 (HDAC1) were down-regulated in DFMO-treated Jurkat cells. The combination of DFMO and TQ dramatically decreased the expression of UHRF1, DNMT1 and HDAC1 genes compared to either DFMO or TQ alone. UHRF1 knockdown led to a decrease in Jurkat cell viability. In conclusion, these results suggest that the combination of DFMO and TQ could be a promising new strategy for the treatment of human acute T lymphoblastic leukemia by targeting the epigenetic code.

Ornithine decarboxylase, the rate-limiting enzyme of polyamine synthesis, modifies brain pathology in a mouse model of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a rare autosomal dominant neurodevelopmental disorder characterized by variable expressivity. TSC results from inactivating variants within the TSC1 or TSC2 genes, leading to constitutive activation of mechanistic target of rapamycin complex 1 signaling. Using a mouse model of TSC (Tsc2-RG) in which the Tsc2 gene is deleted in radial glial precursors and their neuronal and glial descendants, we observed increased ornithine decarboxylase (ODC) enzymatic activity and concentration of its product, putrescine. To test if increased ODC activity and dysregulated polyamine metabolism contribute to the neurodevelopmental defects of Tsc2-RG mice, we used pharmacologic and genetic approaches to reduce ODC activity in Tsc2-RG mice, followed by histologic assessment of brain development. We observed that decreasing ODC activity and putrescine levels in Tsc2-RG mice worsened many of the neurodevelopmental phenotypes, including brain growth and neuronal migration defects, astrogliosis and oxidative stress. These data suggest a protective effect of increased ODC activity and elevated putrescine that modify the phenotype in this developmental Tsc2-RG model.

Spermidine as a target for cancer therapy

Spermidine, as a natural component from polyamine members, is originally isolated from semen and also existed in many natural plants, and can be responsible for cell growth and development in eukaryotes. The supplementation of spermidine can extend health and lifespan across species. Although the elevated levels of polyamines and the regulation of rate-limiting enzymes for polyamine metabolism have been identified as the biomarkers in many cancers, recent epidemiological data support that an increased uptake of spermidine as a caloric restriction mimic can reduce overall mortality associated with cancers. The possible mechanisms between spermidine and cancer development may be related to the precise regulation of polyamine metabolism, anti-cancer immunosurveillance, autophagy, and apoptosis. Increased intake of polyamine seems to suppress tumorigenesis, but appears to accelerate the growth of established tumors. Based on these observations and the absolute requirement for polyamines in tumor growth, spermidine could be a rational target for chemoprevention and clinical therapeutics of cancers.

Diverse Functions of Polyamines in Virus Infection

As obligate intracellular parasites, viruses rely on host cells for the building blocks of progeny viruses. Metabolites such as amino acids, nucleotides, and lipids are central to viral proteins, genomes, and envelopes, and the availability of these molecules can restrict or promote infection. Polyamines, comprised of putrescine, spermidine, and spermine in mammalian cells, are also critical for virus infection. Polyamines are small, positively charged molecules that function in transcription, translation, and cell cycling. Initial work on the function of polyamines in bacteriophage infection illuminated these molecules as critical to virus infection. In the decades since early virus-polyamine descriptions, work on diverse viruses continues to highlight a role for polyamines in viral processes, including genome packaging and viral enzymatic activity. On the host side, polyamines function in the response to virus infection. Thus, viruses and hosts compete for polyamines, which are a critical resource for both. Pharmacologically targeting polyamines, tipping the balance to favor the host and restrict virus replication, holds significant promise as a broad-spectrum antiviral strategy.

Spermine synthesis inhibitor blocks 25-hydroxycholesterol-induced- apoptosis via SREBP2 upregulation in DLD-1 cell spheroids

The oxysterol 25-hydroxycholesterol (25-HC) has diverse physiological activities, including the ability to inhibit anchorage-independent growth of colorectal cancer cells. Here, we found that a polyamine synthesis inhibitor, DFMO, prevented 25-HC-induced apoptosis in non-anchored colorectal cancer DLD-1 cells. Additionally, we found that the spermine synthesis inhibitor APCHA also inhibited 25-HC-induced apoptosis in DLD-1 spheroids. Inhibiting the maturation of SREBP2, a critical regulator of cholesterol synthesis, reversed the effects of APCHA. SREBP2 knockdown also abolished the ability of APCHA to counteract 25-HC activity. Furthermore, APCHA induced SREBP2 maturation and upregulated its transcriptional activity, indicating that altered polyamine metabolism can increase SREBP2 activity and block 25-HC-induced apoptosis in spheroids. These results suggest that crosstalk between polyamine metabolism and cholesterol synthetic pathways via SREBP2 governs the proliferative and malignant properties of colorectal cancer cells.

•

DFMO inhibits 25-HC-induced apoptosis in non-anchored DLD-1 cells.

•

APCHA inhibits 25-HC-induced apoptosis in DLD-1 spheroids.

•

APCHA induces maturation and upregulation of SREBP2.

•

Chemical or genetic inhibition of SREBP2 abrogates anti-apoptotic activity.

A Supramolecular Approach to Structure-Based Design with A Focus on Synthons Hierarchy in Ornithine-Derived Ligands: Review, Synthesis, Experimental and in Silico Studies

The success of innovative drugs depends on an interdisciplinary and holistic approach to their design and development. The supramolecular architecture of living systems is controlled by non-covalent interactions to a very large extent. The latter are prone to extensive cooperation and like a virtuoso play a symphony of life. Thus, the design of effective ligands should be based on thorough knowledge on the interactions at either a molecular or high topological level. In this work, we emphasize the importance of supramolecular structure and ligand-based design keeping the potential of supramolecular H-bonding synthons in focus. In this respect, the relevance of supramolecular chemistry for advanced therapies is appreciated and undisputable. It has developed tools, such as Hirshfeld surface analysis, using a huge data on supramolecular interactions in over one million structures which are deposited in the Cambridge Structure Database (CSD). In particular, molecular interaction surfaces are useful for identification of macromolecular active sites followed by in silico docking experiments. Ornithine-derived compounds are a new, promising class of multi-targeting ligands for innovative therapeutics and cosmeceuticals. In this work, we present the synthesis together with the molecular and supramolecular structure of a novel ornithine derivative, namely N-α,N-δ)-dibenzoyl-(α)-hydroxymethylornithine, 1. It was investigated by modern experimental and in silico methods in detail. The incorporation of an aromatic system into the ornithine core induces stacking interactions, which are vital in biological processes. In particular, rare C=O…π intercontacts have been identified in 1. Supramolecular interactions were analyzed in all structures of ornithine derivatives deposited in the CSD. The influence of substituent was assessed by the Hirshfeld surface analysis. It revealed that the crystal packing is stabilized mainly by H…O, O…H, C…H, Cl (Br, F)…H and O…O interactions. Additionally, π…π, C-H…π and N-O…π interactions were also observed. All relevant H-bond energies were calculated using the Lippincott and Schroeder H-bond model. A library of synthons is provided. In addition, the large synthons (Long-Range Synthon Aufbau Module) were considered. The DFT optimization either in vacuo or in solutio yields very similar molecular species. The major difference with the relevant crystal structure was related to the conformation of terminal benzoyl C15-C20 ring. Furthermore, in silico prediction of the extensive physicochemical ADME profile (absorption, distribution, metabolism and excretion) related to the drug-likeness and medicinal chemistry friendliness revealed that a novel ornithine derivative 1 has the potential to be a new drug candidate. It has shown good in silico absorption and very low toxicity.

Basic Hallmarks of Urothelial Cancer Unleashed in Primary Uroepithelium by Interference with the Epigenetic Master Regulator ODC1

Urothelial carcinoma (UC) is a common disease causing significant morbidity and mortality as well as considerable costs for health systems. Extensive aberrant methylation of DNA is broadly documented in early UC, contributing to genetic instability, altered gene expression and tumor progression. However the triggers initiating aberrant methylation are unknown. Recently we discovered that several genes encoding key enzymes of methyl group and polyamine metabolism, including Ornithine Decarboxylase 1 (ODC1), are affected by DNA methylation in early stage UC. In this study, we investigated the hypothesis that these epigenetic alterations act in a feed-forward fashion to promote aberrant DNA methylation in UC. We demonstrate that siRNA-mediated knockdown of ODC1 expression elicits genome-wide LINE-1 demethylation, induction of LINE-1 transcripts and double-strand DNA breaks and decreases viability in primary cultured uroepithelial cells. Similarly, following siRNA-mediated knockdown of ODC1, UC cells undergo double-strand DNA breaks and apoptosis. Collectively, our findings provide evidence that ODC1 gene hypermethylation could be a starting point for the onset of genome-wide epigenetic aberrations in urothelial carcinogenesis. Furthermore, LINE-1 induction enabled by ODC1 interference provides a new experimental model to study mechanisms and consequences of LINE-1 activation in the etiology and progression of UC as well as presumably other cancers.

Hypusine biosynthesis in β cells links polyamine metabolism to facultative cellular proliferation to maintain glucose homeostasis

Deoxyhypusine synthase (DHPS) uses the polyamine spermidine to catalyze the hypusine modification of the mRNA translation factor eIF5A and promotes oncogenesis through poorly defined mechanisms. Because germline deletion of Dhps is embryonically lethal, its role in normal postnatal cellular function in vivo remains unknown. We generated a mouse model that enabled the inducible, postnatal deletion of Dhps specifically in postnatal islet β cells, which function to maintain glucose homeostasis. Removal of Dhps did not have an effect under normal physiologic conditions. However, upon development of insulin resistance, which induces β cell proliferation, Dhps deletion caused alterations in proteins required for mRNA translation and protein secretion, reduced production of the cell cycle molecule cyclin D2, impaired β cell proliferation, and induced overt diabetes. We found that hypusine biosynthesis was downstream of protein kinase C-ζ and was required for c-Myc-induced proliferation. Our studies reveal a requirement for DHPS in β cells to link polyamines to mRNA translation to effect facultative cellular proliferation and glucose homeostasis.

PGC1α Inhibits Polyamine Synthesis to Suppress Prostate Cancer Aggressiveness

Although tumorigenesis is dependent on the reprogramming of cellular metabolism, the metabolic pathways engaged in the formation of metastases remain largely unknown. The transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) plays a pleiotropic role in the control of cancer cell metabolism and has been associated with a good prognosis in prostate cancer. Here, we show that PGC1α represses the metastatic properties of prostate cancer cells via modulation of the polyamine biosynthesis pathway. Mechanistically, PGC1α inhibits the expression of c-MYC and ornithine decarboxylase 1 (ODC1), the rate-limiting enzyme for polyamine synthesis. Analysis of in vivo metastases and clinical data from patients with prostate cancer support the proposition that the PGC1α/c-MYC/ODC1 axis regulates polyamine biosynthesis and prostate cancer aggressiveness. In conclusion, downregulation of PGC1α renders prostate cancer cells dependent on polyamine to promote metastasis. SIGNIFICANCE: These findings show that a major regulator of mitochondrial metabolism controls polyamine synthesis and prostate cancer aggressiveness, with potential applications in therapy and identification of new biomarkers.

Coxsackievirus B3 Responds to Polyamine Depletion via Enhancement of 2A and 3C Protease Activity

Polyamines are small positively-charged molecules abundant in eukaryotic cells that are crucial to RNA virus replication. In eukaryotic cells, polyamines facilitate processes such as transcription, translation, and DNA replication, and viruses similarly rely on polyamines to facilitate transcription and translation. Whether polyamines function at additional stages in viral replication remains poorly understood. Picornaviruses, including Coxsackievirus B3 (CVB3), are sensitive to polyamine depletion both in vitro and in vivo; however, precisely how polyamine function in picornavirus infection has not been described. Here, we describe CVB3 mutants that arise with passage in polyamine-depleted conditions. We observe mutations in the 2A and 3C proteases, and we find that these mutant proteases confer resistance to polyamine depletion. Using a split luciferase reporter system to measure protease activity, we determined that polyamines facilitate viral protease activity. We further observe that the 2A and 3C protease mutations enhance reporter protease activity in polyamine-depleted conditions. Finally, we find that these mutations promote cleavage of cellular eIF4G during infection of polyamine-depleted cells. In sum, our results suggest that polyamines are crucial to protease function during picornavirus infection. Further, these data highlight viral proteases as potential antiviral targets and highlight how CVB3 may overcome polyamine-depleting antiviral therapies.

Polyamine Metabolism as a Therapeutic Target inHedgehog-Driven Basal Cell Carcinomaand Medulloblastoma

Hedgehog (Hh) signaling is a critical developmental regulator and its aberrant activation,due to somatic or germline mutations of genes encoding pathway components, causes Basal CellCarcinoma (BCC) and medulloblastoma (MB). A growing effort has been devoted at theidentification of druggable vulnerabilities of the Hedgehog signaling, leading to the identificationof various compounds with variable efficacy and/or safety. Emerging evidence shows that anaberrant polyamine metabolism is a hallmark of Hh-dependent tumors and that itspharmacological inhibition elicits relevant therapeutic effects in clinical or preclinical models ofBCC and MB. We discuss here the current knowledge of polyamine metabolism, its role in cancerand the available targeting strategies. We review the literature about the connection betweenpolyamines and the Hedgehog signaling, and the potential therapeutic benefit of targetingpolyamine metabolism in two malignancies where Hh pathways play a well-established role: BCCand MB.

Effects of topical 0.8% piroxicam and 50+ sunscreen filters on actinic keratosis in hypertensive patients treated with or without photosensitizing diuretic drugs: an observational cohort study

Background

Photosensitizing diuretics use (especially thiazide compounds) is associated with a significantly higher risk of squamous cell carcinoma (SCC). Actinic keratosis (AK) is a precursor of SCC.

Study aim

To evaluate in a prospective cohort study the efficacy of topical piroxicam 0.8% and sunscreen 50+ (ACTX) in the treatment of AK in hypertensive subjects with or without TD treatment.

Subjects and methods

A total of 119 hypertensive subjects with multiple AK (39 under chronic TD treatment; and 80 treated with other non-TD, non-photosensitizing antihypertensive drugs) were enrolled after their informed consent in a 6-month observational cohort study. All the subjects were treated with ACTX twice daily. The primary endpoint was the evolution of AK lesions at baseline, after 3 and 6 months. The secondary endpoint was the clearance of AK target lesions and field of cancerization by dermoscopic evaluation using a score evaluating erythema, scaling, pigmentation, and follicular plugs (ESPFP score; ranging from 0 to 20). An investigator, unaware of the type of antihypertensive treatments (TD or non-TD), performed all the clinical and dermoscopy evaluations.

Results

At baseline, AK mean (SD) lesion number in TD group was 14.1(4) and 14.6(4) in the non-TD group. ESPFP mean (SD) score at baseline was 5.8(1.2) in both groups. A significant reduction of AK lesions in comparison with baseline was observed in both groups. A statistically significant greater reduction was observed in TD in comparison with the non-TD group (−54% vs −32%). ESPFP score was reduced in a higher proportion in the TD group in comparison with the non-TD group (−60% vs −37%, respectively). ACTX treatment was very well tolerated.

Conclusion

In hypertensive subjects with multiple AK, the topical use of ACTX is associated with a significant reduction of lesions count with an improvement in the field cancerization. The clinical efficacy is more pronounced in subjects under thiazide diuretics treatment.

Targeting metabolic vulnerabilities of cancer: Small molecule inhibitors in clinic

BACKGROUND

Altered cell metabolism is an established hallmark of cancer. Advancement in our understanding of dysregulated cellular metabolism has aided drastically in identifying metabolic vulnerabilities that can be exploited therapeutically. Indeed, this knowledge has led to the development of a multitude of agents targeting various aspects of tumor metabolism.

RECENT FINDINGS

The intent of this review is to provide insight into small molecule inhibitors that target tumor metabolism and that are currently being explored in active clinical trials as either preventive, stand-alone, or adjuvant therapies for various malignancies. For each inhibitor, we outline the mechanism (s) of action, preclinical/clinical findings, and limitations. Sections are divided into three aspects based on the primary target of the small molecule inhibitor (s): those that impact (1) cancer cells directly, (2) immune cells present in the tumor microenvironment, or (3) both cancer cells and immune cells. We highlight small molecule targeting of metabolic pathways including de novo fatty acid synthesis, NAD+ biosynthesis, 2-hydroxyglutarate biosynthesis, polyamine metabolism, the kynurenine pathway, as well as glutamine and arginine metabolism.

CONCLUSIONS

Use of small molecule inhibitors aimed at exploiting tumor metabolic vulnerabilities continues to be an active area of research. Identifying metabolic dependencies specific to cancer cells and/or constituents of the tumor microenvironment is a viable area of therapeutic intervention that holds considerable clinical potential.

Ornithine Decarboxylase in Macrophages Exacerbates Colitis and Promotes Colitis-Associated Colon Carcinogenesis by Impairing M1 Immune Responses

Ornithine decarboxylase (ODC) is the rate-limiting enzyme for polyamine biosynthesis and restricts M1 macrophage activation in gastrointestinal (GI) infections. However, the role of macrophage ODC in colonic epithelial-driven inflammation is unknown. Here, we investigate cell-specific effects of ODC in colitis and colitis-associated carcinogenesis (CAC). Human colonic macrophages expressed increased ODC levels in active ulcerative colitis and Crohn's disease, colitis-associated dysplasia, and CAC. Mice lacking Odc in myeloid cells (OdcΔmye mice) that were treated with dextran sulfate sodium (DSS) exhibited improved survival, body weight, and colon length and reduced histologic injury versus control mice. In contrast, GI epithelial-specific Odc knockout had no effect on clinical parameters. Despite reduced histologic damage, colitis tissues of OdcΔmye mice had increased levels of multiple proinflammatory cytokines and chemokines and enhanced expression of M1, but not M2 markers. In the azoxymethane-DSS model of CAC, OdcΔmye mice had reduced tumor number, burden, and high-grade dysplasia. Tumors from OdcΔmye mice had increased M1, but not M2 macrophages. Increased levels of histone 3, lysine 9 acetylation, a marker of open chromatin, were manifest in tumor macrophages of OdcΔmye mice, consistent with our findings that macrophage ODC affects histone modifications that upregulate M1 gene transcription during GI infections. These findings support the concept that macrophage ODC augments epithelial injury-associated colitis and CAC by impairing the M1 responses that stimulate epithelial repair, antimicrobial defense, and antitumoral immunity. They also suggest that macrophage ODC is an important target for colon cancer chemoprevention.Significance: Ornithine decarboxylase contributes to the pathogenesis of colitis and associated carcinogenesis by impairing M1 macrophage responses needed for antitumoral immunity; targeting ODC in macrophages may represent a new strategy for chemoprevention. Cancer Res; 78(15); 4303-15. ©2018 AACR.

Cellular and Animal Model Studies on the Growth Inhibitory Effects of Polyamine Analogues on Breast Cancer

Polyamine levels are elevated in breast tumors compared to those of adjacent normal tissues. The female sex hormone, estrogen is implicated in the origin and progression of breast cancer. Estrogens stimulate and antiestrogens suppress the expression of polyamine biosynthetic enzyme, ornithine decarboxylate (ODC). Using several bis(ethyl)spermine analogues, we found that these analogues inhibited the proliferation of estrogen receptor-positive and estrogen receptor negative breast cancer cells in culture. There was structure-activity relationship in the efficacy of these compounds in suppressing cell growth. The activity of ODC was inhibited by these compounds, whereas the activity of the catabolizing enzyme, spermidine/spermine N¹-acetyl transferase (SSAT) was increased by 6-fold by bis(ethyl)norspermine in MCF-7 cells. In a transgenic mouse model of breast cancer, bis(ethyl)norspermine reduced the formation and growth of spontaneous mammary tumor. Recent studies indicate that induction of polyamine catabolic enzymes SSAT and spermine oxidase (SMO) play key roles in the anti-proliferative and apoptotic effects of polyamine analogues and their combinations with chemotherapeutic agents such as 5-fluorouracil (5-FU) and paclitaxel. Thus, polyamine catabolic enzymes might be important therapeutic targets and markers of sensitivity in utilizing polyamine analogues in combination with other therapeutic agents.

Oil for the cancer engine: The cross-talk between oncogenic signaling and polyamine metabolism

The study of metabolism has provided remarkable information about the biological basis and therapeutic weaknesses of cancer cells. Classic biochemistry established the importance of metabolic alterations in tumor biology and revealed the importance of various metabolite families to the tumorigenic process. We have evidence of the central role of polyamines, small polycatonic metabolites, in cell proliferation and cancer growth from these studies. However, how cancer cells activate this metabolic pathway and the molecular cues behind the oncogenic action of polyamines has remained largely obscure. In contrast to the view of metabolites as fuel (anabolic intermediates) for cancer cells, polyamines are better defined as the oil that lubricates the cancer engine because they affect the activity of biological processes. Modern research has brought back to the limelight this metabolic pathway, providing a strong link between genetic, metabolic, and signaling events in cancer. In this review, we enumerate and discuss current views of the regulation and activity of polyamine metabolism in tumor cell biology.

Ornithine decarboxylase as a therapeutic target for endometrial cancer

Ornithine Decarboxylase (ODC) a key enzyme in polyamine biosynthesis is often overexpressed in cancers and contributes to polyamine-induced cell proliferation. We noted ubiquitous expression of ODC1 in our published endometrial cancer gene array data and confirmed this in the cancer genome atlas (TCGA) with highest expression in non-endometrioid, high grade, and copy number high cancers, which have the worst clinical outcomes. ODC1 expression was associated with worse overall survival and increased recurrence in three endometrial cancer gene expression datasets. Importantly, we confirmed these findings using quantitative real-time polymerase chain reaction (qRT-PCR) in a validation cohort of 60 endometrial cancers and found that endometrial cancers with elevated ODC1 had significantly shorter recurrence-free intervals (KM log-rank p = 0.0312, Wald test p = 5.59e-05). Difluoromethylornithine (DFMO) a specific inhibitor of ODC significantly reduced cell proliferation, cell viability, and colony formation in cell line models derived from undifferentiated, endometrioid, serous, carcinosarcoma (mixed mesodermal tumor; MMT) and clear cell endometrial cancers. DFMO also significantly reduced human endometrial cancer ACI-98 tumor burden in mice compared to controls (p = 0.0023). ODC-regulated polyamines (putrescine [Put] and/or spermidine [Spd]) known activators of cell proliferation were strongly decreased in response to DFMO, in both tumor tissue ([Put] (p = 0.0006), [Spd] (p<0.0001)) and blood plasma ([Put] (p<0.0001), [Spd] (p = 0.0049)) of treated mice. Our study indicates that some endometrial cancers appear particularly sensitive to DFMO and that the polyamine pathway in endometrial cancers in general and specifically those most likely to suffer adverse clinical outcomes could be targeted for effective treatment, chemoprevention or chemoprevention of recurrence.

In-silico gene essentiality analysis of polyamine biosynthesis reveals APRT as a potential target in cancer

Constraint-based modeling for genome-scale metabolic networks has emerged in the last years as a promising approach to elucidate drug targets in cancer. Beyond the canonical biosynthetic routes to produce biomass, it is of key importance to focus on metabolic routes that sustain the proliferative capacity through the regulation of other biological means in order to improve in-silico gene essentiality analyses. Polyamines are polycations with central roles in cancer cell proliferation, through the regulation of transcription and translation among other things, but are typically neglected in in silico cancer metabolic models. In this study, we analysed essential genes for the biosynthesis of polyamines. Our analysis corroborates the importance of previously known regulators of the pathway, such as Adenosylmethionine Decarboxylase 1 (AMD1) and uncovers novel enzymes predicted to be relevant for polyamine homeostasis. We focused on Adenine Phosphoribosyltransferase (APRT) and demonstrated the detrimental consequence of APRT gene silencing on different leukaemia cell lines. Our results highlight the importance of revisiting the metabolic models used for in-silico gene essentiality analyses in order to maximize the potential for drug target identification in cancer.

Polyamines and Their Role in Virus Infection

Polyamines are small, abundant, aliphatic molecules present in all mammalian cells. Within the context of the cell, they play a myriad of roles, from modulating nucleic acid conformation to promoting cellular proliferation and signaling. In addition, polyamines have emerged as important molecules in virus-host interactions. Many viruses have been shown to require polyamines for one or more aspects of their replication cycle, including DNA and RNA polymerization, nucleic acid packaging, and protein synthesis. Understanding the role of polyamines has become easier with the application of small-molecule inhibitors of polyamine synthesis and the use of interferon-induced regulators of polyamines. Here we review the diverse mechanisms in which viruses require polyamines and investigate blocking polyamine synthesis as a potential broad-spectrum antiviral approach.

Torpor: The Rise and Fall of 3-Monoiodothyronamine from Brain to Gut-From Gut to Brain?

3-Monoiodothyronamine (T1AM), first isolated from rat brain, is reported to be an endogenous, rapidly acting metabolite of thyroxine. One of its numerous effects is the induction of a "torpor-like" state in experimental animals. A critical analysis of T1AM, to serve as an endogenous cryogen, is given. The proposed biosynthetic pathway for formation of T1AM, which includes deiodinases and ornithine decarboxylase in the upper intestinum, is an unusual one. To reach the brain via systemic circulation, enterohepatic recycling and passage through the liver may occur. The possible role of gut microbiota is discussed. T1AM concentrations in human serum, measured by a specific monoclonal assay are up to three orders of magnitude higher compared to values obtained by MS/MS technology. The difference is explained by the presence of a high-affinity binder for T1AM (Apolipoprotein B-100) in serum, which permits the immunoassay to measure the total concentration of the analyte but limits MS/MS technology to detect only the unbound (free) analyte, a view, which is contested here.