Polyamines prevent DFMO-mediated inhibition of angiogenesis

Polyamine Depletion by D, L-alpha-difluoromethylornithine Inhibits Ewing Sarcoma Metastasis by Inducing Ferroptosis

Polyamine metabolism and signaling play important roles in multiple cancers but have not previously been studied in Ewing sarcoma. Here, we show that blocking polyamine synthesis with D, L-alpha-difluoromethylornithine (DFMO) causes a G1 cell cycle arrest, dose-dependent decreases in sarcosphere formation from Ewing sarcoma cell lines growing in non-adherent conditions and a decrease in clonogenic growth in soft agar. Further, we utilized our orthotopic implantation/amputation model of Ewing sarcoma metastasis to demonstrate that DFMO slowed primary tumor growth in addition to limiting metastasis. RNA sequencing demonstrated gene expression patterns consistent with induction of ferroptosis caused by polyamine depletion. Induction of ferroptosis was validated in vitro by demonstrating that ferrostatin-1, an inhibitor of ferroptosis, allows sphere formation even in the presence of DFMO. Collectively, these results reveal a novel mechanism by which DFMO prevents metastasis - induction of ferroptosis due to polyamine depletion. Our results provide preclinical justification to test the ability of DFMO to prevent metastatic recurrence in Ewing sarcoma patients at high risk for relapse.

Glioma Metabolic Feedback In Situ: A First-In-Human Pharmacodynamic Trial of Difluoromethylornithine + AMXT-1501 Through High-Molecular Weight Microdialysis

BACKGROUND AND OBJECTIVES

No new drug has improved survival for glioblastoma since temozolomide in 2005, due in part to the relative inaccessibility of each patient's individualized tumor biology and its response to therapy. We have identified a conserved extracellular metabolic signature of enhancing high-grade gliomas enriched for guanidinoacetate (GAA). GAA is coproduced with ornithine, the precursor to protumorigenic polyamines through ornithine decarboxylase (ODC). AMXT-1501 is a polyamine transporter inhibitor that can overcome tumoral resistance to the ODC inhibitor, difluoromethylornithine (DFMO). We will use DFMO with or without AMXT-1501 to identify candidate pharmacodynamic biomarkers of polyamine depletion in patients with high-grade gliomas in situ . We aim to determine (1) how blocking polyamine production affects intratumoral extracellular guanidinoacetate abundance and (2) the impact of polyamine depletion on the global extracellular metabolome within live human gliomas in situ.

METHODS

DFMO, with or without AMXT-1501, will be administered postoperatively in 15 patients after clinically indicated subtotal resection for high-grade glioma. High-molecular weight microdialysis catheters implanted into residual tumor and adjacent brain will be used for postoperative monitoring of extracellular GAA and polyamines throughout therapeutic intervention from postoperative day (POD) 1 to POD5. Catheters will be removed on POD5 before discharge.

EXPECTED OUTCOMES

We anticipate that GAA will be elevated in tumor relative to adjacent brain although it will decrease within 24 hours of ODC inhibition with DFMO. If AMXT-1501 effectively increases the cytotoxic impact of ODC inhibition, we expect an increase in biomarkers of cytotoxicity including glutamate with DFMO + AMXT-1501 treatment when compared with DFMO alone.

DISCUSSION

Limited mechanistic feedback from individual patients' gliomas hampers clinical translation of novel therapies. This pilot Phase 0 study will provide in situ feedback during DFMO + AMXT-1501 treatment to determine how high-grade gliomas respond to polyamine depletion.

A review of the amino acid metabolism in placental function response to fetal loss and low birth weight in pigs

The fertility of sows mainly depends on the embryo losses during gestation and the survival rate of the post-farrowing piglets. The selection of highly-prolific sows has been mainly focused on the selection of genotypes with high ovulatory quota. However, in the early- and post-implantation stages, the rate of embryo losses was increased with the increase of zygotes. Among the various factors, placental growth and development is the vital determinant for fetal survival, growth, and development. Despite the potential survival of fetuses with deficient placental development, their life-conditions and growth can be damaged by a process termed intrauterine growth retardation (IUGR). The newborn piglets affected by IUGR are prone to increased morbidity and mortality rates; meanwhile, the growth, health and welfare of the surviving piglets will remain hampered by these conditions, with a tendency to exacerbate with age. Functional amino acids such as glycine, proline, and arginine continue to increase with the development of placenta, which are not only essential to placental growth (including vascular growth) and development, but can also be used as substrates for the production of glutathione, polyamines and nitric oxide to benefit placental function in many ways. However, the exact regulation mechanism of these amino acids in placental function has not yet been clarified. In this review, we provide evidence from literature and our own work for the role and mechanism of dietary functional amino acids during pregnancy in regulating the placental functional response to fetal loss and birth weight of piglets. This review will provide novel insights into the response of nutritionally nonessential amino acids (glycine and proline) to placental development as well as feasible strategies to enhance the fertility of sows.

Arginine, Agmatine, and Polyamines: Key Regulators of Conceptus Development in Mammals

Arginine is a key amino acid in pregnant females as it is the precursor for nitric oxide (NO) via nitric oxide synthase and for polyamines (putrescine, spermidine, and spermine) by either arginase II and ornithine decarboxylase to putrescine or via arginine decarboxylase to agmatine and agmatine to putrescine via agmatinase. Polyamines are critical for placental growth and vascularization. Polyamines stabilize DNA and mRNA for gene transcription and mRNA translation, stimulate proliferation of trophectoderm, and formation of multinucleated trophectoderm cells that give rise to giant cells in the placentae of species such as mice. Polyamines activate MTOR cell signaling to stimulate protein synthesis and they are important for motility through modification of beta-catenin phosphorylation, integrin signaling via focal adhesion kinases, cytoskeletal organization, and invasiveness or superficial implantation of blastocysts. Physiological levels of arginine, agmatine, and polyamines are critical to the secretion of interferon tau for pregnancy recognition in ruminants. Arginine, polyamines, and agmatine are very abundant in fetal fluids, fetal blood, and tissues of the conceptus during gestation. The polyamines are thus available to influence a multitude of events including activation of development of blastocysts, implantation, placentation, fetal growth, and development required for the successful establishment and maintenance of pregnancy in mammals.

Triggering doxorubicin release from responsive hydrogel films by polyamine uptake

Polyamines such as putrescine, spermidine and spermine are required in many inter- and intra-cellular processes. There is, however, evidence of anomalously high concentrations of these polyamines around cancer cells. Furthermore, high polyamine concentrations play a key role in accelerating the speed of cancer proliferation. Some current therapies target the reduction of the polyamine concentration to delay the cancer advance. In this study, we use a molecular theory to prove the concept that poly(methacrylic acid) (PMAA) hydrogels can play the dual role of incorporating and retaining polyamines as well as releasing preloaded drugs in response. Towards such a goal, we have developed a molecular model for each of the chemical species, which includes the shape, size, charge, protonation state, and configuration. Our results indicate that PMAA hydrogel films can incorporate significant amounts of polyamines; this absorption increases with the solution concentration of the polyamines. Doxorubicin was chosen as a model drug for this study, which can be successfully incorporated within the film; the optimal encapsulation conditions occur at low salt concentrations and pH values near neutral. Polyamine absorption within the film results in the desorption of the drug from the hydrogel. An increase in the concentration of the polyamines enhances the drug release. To validate our theoretical findings, poly(methacrylic acid) hydrogel thin films were synthesized by atom transfer radical polymerization. Absorption/desorption experiments followed by UV-Vis spectroscopy demonstrate doxorubicin encapsulation within these films and polyamine-dependent drug release.

Role of putrescine in ovary and embryo development in fruit bat Cynopterus sphinx during embryonic diapause

The aim of this study was to evaluate the effect of putrescine on ovarian activity and the rate of embryonic development in Cynopterus sphinx during delayed development. The result showed the presence of a rate-limiting enzyme, ornithine decarboxylase-1, in both ovary and utero-embryonic unit of C. sphinx suggests a synthesis of putrescine in these sites. The corpus luteum showed increased, whereas utero-embryonic unit showed decreased production of putrescine during delayed development as compared with the normal development. The bat treated in vivo with putrescine during delayed development showed increase in progesterone and estradiol synthesis, correlated with increased expression of luteinizing hormone receptor, steroidogenic acute receptor protein, and 3β-hydroxysteroid dehydrogenase through extracellular signal-regulated kinase (ERK1/2)-mediated pathway in the ovary; but showed increase in the weight and expression of progesterone receptor (PR), B-cell lymphoma 2, proliferating cell nucleus antigen, and vascular endothelial growth factor proteins in utero-embryonic unit. The in vitro treatment of putrescine showed stimulatory whereas treatment with an inhibitor of putrescine, 2-difluoromethylornithine caused an inhibitory effect on ovarian progesterone synthesis and cell proliferation, and cell survival in the utero-embryonic unit. In conclusion, the putrescine showed two separate roles during embryonic diapause, high concentration of putrescine in the ovary may support corpus luteum and basal synthesis of progesterone, whereas a low level of putrescine causes retarded embryonic development by inhibiting cell proliferation in the utero-embryonic unit. The bat treated with putrescine either directly promotes cell proliferation, cell survival, and angiogenic activities or acts indirectly increasing PR on utero-embryonic unit thereby activating development in delayed embryo in C. sphinx.

Physiological importance of polyamines

Polyamines are polycationic molecules that contain two or more amino groups (-NH3 +) and are present in all eukaryotic and prokaryotic cells. Polyamines are synthesized from arginine, ornithine, and proline, and from methionine as the methyl-group donor. In the traditional pathway for polyamine synthesis, arginase converts arginine into ornithine, which is decarboxylated by ornithine decarboxylase (ODC1) to generate putrescine. The latter is converted to spermidine and spermine. Recent studies have indicated the existence of 'non-classical pathways' for the generation of putrescine from arginine and proline in animal cells. Specifically, arginine decarboxylase (ADC) catalyzes the conversion of arginine into agmatine, which is hydrolyzed by agmatinase (AGMAT) to form putrescine. Additionally, proline is oxidized by proline oxidase to yield pyrroline-5-carboxylate, which undergoes transamination with glutamate to produce ornithine for decarboxylation by ODC1. Intracellular production of polyamines is controlled by antizymes binding to and inactivating ODC1. Polyamines exert effects that include stimulation of cell division and proliferation, gene expression for the survival of cells, DNA and protein synthesis, regulation of apoptosis, oxidative stress, angiogenesis, and cell-cell communication activity. Accordingly, polyamines are essential for early embryonic development and successful pregnancy outcome in mammals. In this paper the main concepts on the history, structure and molecular pathways of polyamines as well as their physiological role on angiogenesis, and reproductive physiology are reviewed.

Genetic polymorphism in ornithine decarboxylase and risk of breast cancer

Ornithine decarboxylase (ODC), the first enzyme in the biosynthesis of polyamines, has increased activity in breast cancer tissue compared with benign and normal tissues. The ODC gene contains a single nucleotide polymorphism in which a guanine is substituted for an adenine. This study investigated whether the ODC +316 G > A polymorphism (rs2302615) was associated with the risk of developing breast cancer. A case-control study involving 121 controls, without breast cancer, 46 patients with breast cancer but without a family history, and 130 breast cancer cases with a family history of breast cancer was conducted. A nested PCR-restriction fragment length polymorphism procedure and the TaqMan 5' nuclease assay was used to genotype individuals. Risk was significantly lower for heterozygote (GA genotype) individuals [odds ratio (OR) = 0.39, 95% confidence interval (CI) 0.17-0.86, P = 0.018], or individuals with at least one A allele (OR = 0.44, 95% CI 0.21-0.92, P = 0.027), without family history. This protective effect of having at least one copy of the variant A allele was not as strong, however, in those with a family history of the disease. In sporadic breast cancer, the presence of at least one A allele is protective against the disease. The influence of this polymorphism may be less important in individuals with an inherited breast cancer predisposition.

The novel polyamine analogue CGC-11093 enhances the antimyeloma activity of bortezomib

Multiple myeloma (MM) is an incurable plasma cell malignancy. The recent successes of the proteasome inhibitor bortezomib in MM therapy have prompted investigations of its efficacy in combination with other anticancer agents. Polyamines play important roles in regulating tumor cell proliferation and angiogenesis and represent an important therapeutic target. CGC-11093 is a novel polyamine analogue that has completed a phase I clinical trial for the treatment of cancer. Here, we report that CGC-11093 selectively augments the in vitro and in vivo antimyeloma activity of bortezomib. Specifically, the combination of CGC-11093 and bortezomib compromised MM viability and clonogenic survival, and increased drug-induced apoptosis over that achieved by either single agent. Xenografts of MM tumors treated with this combination had marked increases in phospho-c-Jun-NH(2)-kinase (JNK)-positive cells and apoptosis, and corresponding reductions in tumor burden, tumor vasculature, and the expression of proliferating cell nuclear antigen and the proangiogenic cytokine vascular endothelial growth factor. Furthermore, inhibition of JNK with a pharmacologic inhibitor or by selective knockdown blunted the efficacy of CGC-11093 and bortezomib. Therefore, CGC-11093 enhances the anticancer activity of bortezomib by augmenting JNK-mediated apoptosis and blocking angiogenesis. These findings support the study of the use of the combination of bortezomib and CGC-11093 in MM patients that fail to respond to frontline therapy.

Effects of difluoromethylornithine on growth inhibition and apoptosis in human cervical epithelial and cancerous cell lines

OBJECTIVE

Difluoromethylornithine(DFMO), an irreversible inhibitor of ornithine decarboxylase and an angiogenesis inhibitor, has been used in phase I cervical intraepithelial neoplasia (CIN) trials, producing a 50% regression of CIN 3 lesions. DFMO is currently in phase II trials. In the experiments reported here, DFMO's growth inhibition and apoptosis induction were explored in an in vitro model to elucidate mechanisms of action.

METHODS

Four immortalized cervical epithelial cell lines, serving as in vitro models of precancerous CIN lesions, and nine cervical carcinoma cell lines were studied. DFMO's growth inhibitory effect was tested in monolayer culture and in semisolid medium, and concentrations required for a 50% growth inhibition (IC(50)) with a 5-day treatment were determined. Apoptosis induction was analyzed using the terminal deoxynucleotidyl transferase assay of DNA fragmentation.

RESULTS

DFMO inhibited growth of immortalized cervical epithelial cell lines and cervical cancer cell lines in monolayer culture and in semisolid medium. The immortalized cervical epithelial cell lines were more sensitive than the cervical cancer cell lines to DFMO's growth inhibitory effect. Concentrations required for 50% growth inhibition after a 5-day treatment ranged from 100 microM to >5 mM for cervical carcinoma cell lines and from 100 microM to 1 mM for immortalized cervical epithelial cell lines. DFMO induced apoptosis in precancerous and cancerous cell lines at a concentration of 5 mM, regardless of the cells' human papillomavirus status.

CONCLUSION

DFMO inhibits the growth of cervical precancerous and cancerous cells in vitro in a dose-dependent and time-dependent manner, partially through inducing apoptosis.

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

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

Heparin inhibits phorbol ester-induced ornithine decarboxylase gene expression in endothelial cells

Glycosaminoglycans regulate angiogenesis by affecting the availability of different growth factors for the endothelial cell (EC). However, little is known about the molecular and functional consequences resulting from direct interaction of these polyelectrolytes with the EC. Here we show that heparin markedly inhibited serum-stimulated DNA synthesis and ornithine decarboxylase (ODC) mRNA expression in human endothelial cells (HEC). About 50% of the serum effect on DNA synthesis and ODC gene expression was prevented by the selective protein kinase C (PKC) inhibitor chelerythrine or by PKC down-regulation. Heparin was ineffective in counteracting that part of the effect of serum that was resistant to PKC inhibition or down-regulation. In serum-free cultured HEC, heparin completely abolished the increase in DNA synthesis and ODC mRNA expression elicited by a number of PKC activators. Cell exposure to difluoromethylornithine, an irreversible inhibitor of ODC enzyme, dramatically antagonised both serum- and phorbol 12-myristate 13-acetate (PMA)-stimulated DNA synthesis. These results suggest that inhibition of PKC-mediated ODC gene expression by glycosaminoglycans may represent an important mechanism in the regulation of HEC proliferation.

Hydrogen peroxide is involved in lymphocyte activation mechanisms to induce angiogenesis

T-lymphocytes from tumour-bearing mice are able to trigger the angiogenic cascade. Since it is known that tumour growth produces reactive oxygen species (ROS), the aim of this study was to evaluate the role of hydrogen peroxide (H2O2) on the activation of lymphocytes and their induction of this vascular response. Studies on lymphocytes, stimulated in vitro by ROS to induce angiogenesis, showed that only the enzyme catalase (CAT) could block the activation. The incubation of normal lymphocytes with H2O2 stimulated these cells to induce angiogenesis. The administration of H2O2 or an oxidative stress-producing drug (doxorubicin) to normal mice activated in vivo angiogenesis. In tumour-bearing mice, high levels of lipid peroxidation products were observed in the spleen, but not in the liver or kidney. Moreover, when the ROS scavenger enzyme activities (superoxide dismutase (SDM) and CAT) were determined, we observed low CAT activity in normal spleens, reflected in a high SDM/CAT ratio, when compared to liver or kidney values. We also showed an increasing value of the SDM/CAT ratio with tumour growth. These results strongly suggest that H2O2 could be involved in the mechanisms of lymphocyte activation and their induction of angiogenesis during tumour growth.

Characterization of F3II, a sarcomatoid mammary carcinoma cell line originated from a clonal subpopulation of a mouse adenocarcinoma

We characterized a new mammary tumor cell line, F3II, previously established in vitro from a clonal subpopulation of the BALB/c transplantable mammary adenocarcinoma M3, moderately metastatic to lung. The F3II cell line has been passaged > 50 times. It has grown as elongated cells adherent to the bottom of the flask. Cytogenetic studies showed that F3II cultures were nearly triploid. Tumor cells expressed fibronectin and showed high levels of cell-surface urokinase, a key protease in invasion and metastasis. F3II cells grew as poorly differentiated, spindle-cell carcinoma tumors (sarcomatoid carcinomas) with a prominent local invasiveness, a high angiogenic response, and a 90-100% incidence of lung metastases when inoculated s.c. into syngeneic mice. Ultrastructural and immunocytochemical analysis revealed characteristic features of carcinomas. Our data suggest that F3II is less differentiated and more aggressive than the original tumor line, supporting the notion that mammary carcinomas are heterogeneous neoplasms and contain subpopulations with diverse biologic behavior. The F3II mouse mammary sarcomatoid carcinoma line is a suitable model to examine antiinvasive, antiangiogenic, and antimetastatic agents.

Localization of S-adenosylmethionine decarboxylase in murine tissues by immunohistochemistry

S-adenosylmethionine decarboxylase (AdoMetDC), one of three key enzymes in polyamine biosynthesis, is present in minute concentrations in adult tissues, whereas increased AdoMetDC activity occurs in conjunction with differentiation and growth. The occurrence of AdoMetDC in tissues has earlier been studied by biochemical technique only. In this work, an antiserum against recombinant human AdoMetDC was used to investigate the localization of the enzyme in different mouse tissues. In all tissues studied, immunolabeling was seen in cytoplasm, while cell nuclei were negative. In the kidney, AdoMetDC immunoreactivity was confined to the inner part of the cortex; the outer part of the cortex and the medulla displayed only a weak AdoMetDC immunoreaction. In the cortex, renal tubules were strongly reactive, while renal corpuscules were weakly immunolabeled. In developing teeth, AdoMetDC immunoreactivity displayed a gradient of distribution, the immunolabeling intensity being increased from the cervical region to the tip of the cusps. In the incisor, post-secretory ameloblasts were strongly labeled. In the oral mucosa, epithelial cells demonstrated stronger immunolabeling than did cells of the subjacent connective tissue. As for muscle cells, immunoreactive material was confined to the periphery of the fibers. In vitro, treatment with DL-alpha-difluoromethylornithine (DFMO) or methylglyoxal bis-(guanylhydrazone) (MGBG) led to an increase in AdoMetDC. It can be concluded that antibodies to recombinant human AdoMetDC provide a tool for the immunohistochemical localization of AdoMetDC, and that the distribution of the enzyme in the tissues studied gives further support to the importance of polyamines in the development and functions of these organs.

Polyamines as biomarkers of cervical intraepithelial neoplasia

Polyamines (putrescine, spermidine and spermine) play critical roles in cell growth and transformation. Ornithine decarboxylase (ODC), key enzyme in polyamine biosynthesis, is considered a putative protooncogene crucial to the regulation of cell growth and transformation. Cancer patients have elevated levels of polyamines in their physiological fluids compared to normal counterparts. alpha-Difluoromethylornithine (DFMO), a specific suicide inhibitor of ODC, exhibits antitumor and antimetastasis activities, and displays effectiveness in many carcinogen-induced animal chemoprevention models. Therefore, we are using DFMO in a chemoprevention trial for cervical intraepithelial neoplasia grade III (CIN III), and evaluating patients for changes in polyamine metabolism as an intermediate marker of DFMO effect. A preliminary study showed that several milligrams of abnormal cervical biopsy tissue contained detectable levels of ODC activity and polyamines. Additionally, the presence of cadaverine suggested bacterial contamination of these tissues. For this reason, normal and abnormal biopsies collected during colposcopy were rinsed prior to frozen storage. In most patients, abnormal tissue showed greater ODC activities and lower spermidine/spermine ratios than normal tissues. Patients are now being treated with de-escalating doses of DFMO (1-0.06 g/m2/day) for one month. To study the effect of DFMO in patients with CIN III, we are collecting blood and cervical tissue specimens to measure the following parameters: plasma DFMO, ornithine and arginine levels; plasma N1-acetylspermidine levels; erythrocyte (blood polyamine carrier) free polyamine levels; cervical tissue free polyamine levels; cervical tissue N1-acetylspermidine levels; and cervical tissue ODC activities. N1-acetylspermidine will be examined as this compound is known to exist primarily in tumor tissues, not in normal tissues. We therefore established a high-performance liquid chromatography method for N1-acetylspermidine. We expect to find that polyamines are effective markers in analyzing DFMO effects in this chemoprevention trial, thus functioning as pharmacodynamic parameters as well as biomarkers for transformation.