Thymidine phosphorylase induces angiogenesis in vivo and in vitro: an evaluation of possible mechanisms

Astrogliosis in multiple sclerosis and neuro-inflammation: what role for the notch pathway?

Multiple sclerosis is an autoimmune inflammatory disease of the central nervous system leading to neurodegeneration. It affects 2.3 million people worldwide, generally younger than 50. There is no known cure for the disease, and current treatment options - mainly immunotherapies to limit disease progression - are few and associated with serious side effects. In multiple sclerosis, disruption of the blood-brain barrier is an early event in the pathogenesis of lesions, predisposing to edema, excito-toxicity and inflammatory infiltration into the central nervous system. Recently, the vision of the blood brain barrier structure and integrity has changed and include contributions from all components of the neurovascular unit, among which astrocytes. During neuro-inflammation, astrocytes become reactive. They undergo morphological and molecular changes named "astrogliosis" driving the conversion from acute inflammatory injury to a chronic neurodegenerative state. Astrogliosis mechanisms are minimally explored despite their significance in regulating the autoimmune response during multiple sclerosis. Therefore, in this review, we take stock of the state of knowledge regarding astrogliosis in neuro-inflammation and highlight the central role of NOTCH signaling in the process of astrocyte reactivity. Indeed, a very detailed nomenclature published in nature neurosciences in 2021, listing all the reactive astrocyte markers fully identified in the literature, doesn't cover the NOTCH signaling. Hence, we discuss evidence supporting NOTCH1 receptor as a central regulator of astrogliosis in the pathophysiology of neuro-inflammation, notably multiple sclerosis, in human and experimental models.

Developing Wound Dressings Using 2-deoxy-D-Ribose to Induce Angiogenesis as a Backdoor Route for Stimulating the Production of Vascular Endothelial Growth Factor

2-deoxy-D-Ribose (2dDR) was first identified in 1930 in the structure of DNA and discovered as a degradation product of it later when the enzyme thymidine phosphorylase breaks down thymidine into thymine. In 2017, our research group explored the development of wound dressings based on the delivery of this sugar to induce angiogenesis in chronic wounds. In this review, we will survey the small volume of conflicting literature on this and related sugars, some of which are reported to be anti-angiogenic. We review the evidence of 2dDR having the ability to stimulate a range of pro-angiogenic activities in vitro and in a chick pro-angiogenic bioassay and to stimulate new blood vessel formation and wound healing in normal and diabetic rat models. The biological actions of 2dDR were found to be 80 to 100% as effective as VEGF in addition to upregulating the production of VEGF. We then demonstrated the uptake and delivery of the sugar from a range of experimental and commercial dressings. In conclusion, its pro-angiogenic properties combined with its improved stability on storage compared to VEGF, its low cost, and ease of incorporation into a range of established wound dressings make 2dDR an attractive alternative to VEGF for wound dressing development.

2-deoxy-d-ribose (2dDR) upregulates vascular endothelial growth factor (VEGF) and stimulates angiogenesis

BACKGROUND

Delayed neovascularisation of tissue-engineered (TE) complex constructs is a major challenge that causes their failure post-implantation. Although significant progress has been made in the field of angiogenesis, ensuring rapid neovascularisation still remains a challenge. The use of pro-angiogenic agents is an effective approach to promote angiogenesis, and vascular endothelial growth factor (VEGF) has been widely studied both at the biological and molecular levels and is recognised as a key stimulator of angiogenesis. However, the exogenous use of VEGF in an uncontrolled manner has been shown to result in leaky, permeable and haemorrhagic vessels. Thus, researchers have been actively seeking alternative agents to upregulate VEGF production rather than exogenous use of VEGF in TE systems. We have previously revealed the potential of 2-deoxy-d-ribose (2dDR) as an alternative pro-angiogenic agent to induce angiogenesis and accelerates wound healing. However, to date, there is not any clear evidence on whether 2dDR influences the angiogenic cascade that involves VEGF.

METHODS

In this study, we explored the angiogenic properties of 2dDR either by its direct application to human aortic endothelial cells (HAECs) or when released from commercially available alginate dressings and demonstrated that when 2dDR promotes angiogenesis, it also increases the VEGF production of HAECs.

RESULTS

The VEGF quantification results suggested that VEGF production by HAECs was increased with 2dDR treatment but not with other sugars, including 2-deoxy-l-ribose (2dLR) and d-glucose (DG). The stability studies demonstrated that approximately 40-50% of the 2dDR had disappeared in the media over 14 days, either in the presence or absence of HAECs, and the reduction was higher when cells were present. The concentration of VEGF in the media also fell after day 4 associated with the reduction in 2dDR.

CONCLUSION

This study suggests that 2dDR (but not other sugars tested in this study) stimulates angiogenesis by increasing the production of VEGF. We conclude 2dDR appears to be a practical and effective indirect route to upregulating VEGF for several days, leading to increased angiogenesis.

Developing affordable and accessible pro-angiogenic wound dressings; incorporation of 2 deoxy D-ribose (2dDR) into cotton fibres and wax-coated cotton fibres

The absorption capacity of cotton dressings is a critical factor in their widespread use where they help absorb wound exudate. Cotton wax dressings, in contrast, are used for wounds where care is taken to avoid adhesion of dressings to sensitive wounds such as burn injuries. Accordingly, we explored the loading of 2-deoxy-D-ribose (2dDR), a small sugar, which stimulates angiogenesis and wound healing in normal and diabetic rats, into both types of dressings and measured the release of it over several days. The results showed that approximately 90% of 2dDR was released between 3 and 5 days when loaded into cotton dressings. For wax-coated cotton dressings, several methods of loading of 2dDR were explored. A strategy similar to the commercial wax coating methodology was found the best protocol which provided a sustained release over 5 days. Cytotoxicity analysis of 2dDR loaded cotton dressing showed that the dressing stimulated metabolic activity of fibroblasts over 7 days confirming the non-toxic nature of this sugar-loaded dressings. The results of the chick chorioallantoic membrane (CAM) assay demonstrated a strong angiogenic response to both 2dDR loaded cotton dressing and to 2dDR loaded cotton wax dressings. Both dressings were found to increase the number of newly formed blood vessels significantly when observed macroscopically and histologically. We conclude this study offers a simple approach to developing affordable wound dressings as both have the potential to be evaluated as pro-active dressings to stimulate wound healing in wounds where management of exudate or prevention of adherence to the wounds are clinical requirements.

Assessment of the Angiogenic Potential of 2-Deoxy-D-Ribose Using a Novel in vitro 3D Dynamic Model in Comparison With Established in vitro Assays

Angiogenesis is a highly ordered physiological process regulated by the interaction of endothelial cells with an extensive variety of growth factors, extracellular matrix components and mechanical stimuli. One of the most important challenges in tissue engineering is the rapid neovascularization of constructs to ensure their survival after transplantation. To achieve this, the use of pro-angiogenic agents is a widely accepted approach. The study of angiogenesis has gained momentum over the last two decades. Although there are various in vitro, ex vivo, and in vivo angiogenesis models that enable testing of newly discovered pro-angiogenic agents, the problem with researching angiogenesis is the choice of the most appropriate assay. In vivo assays are the most representative and reliable models, but they are expensive, time-consuming and can cause ethical concerns whereas in vitro assays are relatively inexpensive, practical, and reproducible, but they are usually lack of enabling the study of more than one aspect of angiogenesis, and they do not fully represent the complexity of physiological angiogenesis. Therefore, there is a need for the development of an angiogenesis model that allows the study of angiogenesis under physiologically more relevant, dynamic conditions without causing ethical concerns. Accordingly, in this study, we developed 3D in vitro dynamic angiogenesis model, and we tested the angiogenic potential of 2-deoxy-D-ribose (2dDR) in comparison with vascular endothelial growth factor (VEGF) using newly developed in vitro 3D dynamic model and well-established in vitro models. Our results obtained using conventional in vitro assays demonstrated that 2dDR promoted proliferation, migration and tube formation of human aortic endothelial cells (HAECs) in a dose-dependent manner. Then, the angiogenic activity of 2dDR was further assessed using the newly developed 3D in vitro model, which enabled the monitoring of cell proliferation and infiltration simultaneously under dynamic conditions. Our results showed that the administration of 2dDR and VEGF significantly enhanced the outgrowth of HAECs and the cellular density under either static or dynamic conditions.

Testican 1 (SPOCK1) and protein tyrosine phosphatase, receptor type S (PTPRS) show significant increase in saliva of tobacco users with oral cancer

Objectives:

To identify potential candidate proteins which are secretory in nature and present at a higher abundance in oral cancer patients with tobacco habits.

Methods:

Conditioned media of tobacco-treated and -untreated non-neoplastic oral keratinocytes were analyzed using iTRAQ-based mass spectrometry. Hypersecreted proteins; SPARC (osteonectin), cwcv and kazal like domains proteoglycan 1 (SPOCK1); prosaposin (PSAP); and protein tyrosine phosphatase, receptor type S (PTPRS) were validated by enzyme-linked immunosorbent assay (ELISA) using saliva samples from oral cancer patients who are tobacco users.

Results:

Proteomic analysis of tobacco-treated and -untreated cells led to the identification of 2873 proteins. Among these, 378 proteins showed high abundance and 253 proteins showed low abundance (2-fold cutoff) in conditioned-media of tobacco-treated cells. ELISA-based validation showed significantly higher levels of SPOCK1, PSAP, and PTPRS in oral cancer patients with tobacco chewing habits compared to healthy controls. However, PSAP showed low specificity compared to SPOCK1 and PTPRS.

Conclusions:

This study indicates significantly increased levels of SPOCK1, PSAP, and PTPRS in saliva of oral cancer patients with tobacco habits. These protein biomarkers might be useful to identify tobacco users with high risk of developing oral cancers.

Human chorionic villous mesenchymal stem/stromal cells protect endothelial cells from injury induced by high level of glucose

BACKGROUND

Mesenchymal stem/stromal cells derived from chorionic villi of human term placentae (pMSCs) protect human endothelial cells from injury induced by hydrogen peroxide (H₂O₂). In diabetes, elevated levels of glucose (hyperglycaemia) induce H₂O₂ production, which causes the endothelial dysfunction that underlies the enhanced immune responses and adverse complications associated with diabetes, which leads to thrombosis and atherosclerosis. In this study, we examined the ability of pMSCs to protect endothelial cell functions from the negative impact of high level of glucose.

METHODS

pMSCs isolated from the chorionic villi of human term placentae were cultured with endothelial cells isolated from human umbilical cord veins in the presence of glucose. Endothelial cell functions were then determined. The effect of pMSCs on gene expression in glucose-treated endothelial cells was also determined.

RESULTS

pMSCs reversed the effect of glucose on key endothelial cell functions including proliferation, migration, angiogenesis, and permeability. In addition, pMSCs altered the expression of many genes that mediate important endothelial cell functions including survival, apoptosis, adhesion, permeability, and angiogenesis.

CONCLUSIONS

This is the first comprehensive study to provide evidence that pMSCs protect endothelial cells from glucose-induced damage. Therefore, pMSCs have potential therapeutic value as a stem cell-based therapy to repair glucose-induced vascular injury and prevent the adverse complications associated with diabetes and cardiovascular disease. However, further studies are necessary to reveal more detailed aspects of the mechanism of action of pMSCs on glucose-induced endothelial damage in vitro and in vivo.

Direct Activation of NADPH Oxidase 2 by 2-Deoxyribose-1-Phosphate Triggers Nuclear Factor Kappa B-Dependent Angiogenesis

AIMS

Deoxyribose-1-phosphate (dRP) is a proangiogenic paracrine stimulus released by cancer cells, platelets, and macrophages and acting on endothelial cells. The objective of this study was to clarify how dRP stimulates angiogenic responses in human endothelial cells.

RESULTS

Live cell imaging, electron paramagnetic resonance, pull-down of dRP-interacting proteins, followed by immunoblotting, gene silencing of different NADPH oxidases (NOXs), and their regulatory cosubunits by small interfering RNA (siRNA) transfection, and experiments with inhibitors of the sugar transporter glucose transporter 1 (GLUT1) were utilized to demonstrate that dRP acts intracellularly by directly activating the endothelial NOX2 complex, but not NOX4. Increased reactive oxygen species generation in response to NOX2 activity leads to redox-dependent activation of the transcription factor nuclear factor kappa B (NF-κB), which, in turn, induces vascular endothelial growth factor receptor 2 (VEGFR2) upregulation. Using endothelial tube formation assays, gene silencing by siRNA, and antibody-based receptor inhibition, we demonstrate that the activation of NF-κB and VEGFR2 is necessary for the angiogenic responses elicited by dRP. The upregulation of VEGFR2 and NOX2-dependent stimulation of angiogenesis by dRP were confirmed in excisional wound and Matrigel plug vascularization assays in vivo using NOX2^-/- mice.

INNOVATION

For the first time, we demonstrate that dRP acts intracellularly and stimulates superoxide anion generation by direct binding and activation of the NOX2 enzymatic complex.

CONCLUSIONS

This study describes a novel molecular mechanism underlying the proangiogenic activity of dRP, which involves the sequential activation of NOX2 and NF-κB and upregulation of VEGFR2. Antioxid. Redox Signal. 28, 110-130.

Kinetics and mechanistic study of competitive inhibition of thymidine phosphorylase by 5-fluoruracil derivatives

In a previous investigation, cationic liposomes formulated with new 5-FU derivatives, differing for the length of the polyoxyethylenic spacer that links the N(3) position of 5-FU to an alkyl chain of 12 carbon atoms, showed a higher cytotoxicity compared to free 5-FU, the cytotoxic effect being directly related to the length of the spacer. To better understand the correlation of the spacer length with toxicity, we carried out initial rate studies to determine inhibition, equilibrium and kinetic constants (KI, KM, kcat), and get inside inhibition activity of the 5-FU derivatives and their mechanism of action, a crucial information to design structural variations for improving the anticancer activity. The experimental investigation was supported by docking simulations based on the X-ray structure of thymidine phosphorylase (TP) from Escherichia coli complexed with 3'-azido-2'-fluoro-dideoxyuridin. Theoretical and experimental results showed that all the derivatives exert the same inhibition activity of 5-FU either as monomer and when embedded in lipid bilayer.

HO-1/CO system in tumor growth, angiogenesis and metabolism - Targeting HO-1 as an anti-tumor therapy

Heme oxygenase-1 (HO-1, hmox-1) catalyzes the rate-limiting step in the heme degradation processes. Out of three by-products of HO-1 activity, biliverdin, iron ions and carbon monoxide (CO), the latter was mostly shown to mediate many beneficial HO-1 effects, including protection against oxidative injury, regulation of apoptosis, modulation of inflammation as well as contribution to angiogenesis. Mounting evidence suggests that HO-1/CO systemmay be of special benefit in protection inmany pathological conditions, like atherosclerosis or myocardial infarction. By contrast, the augmented expression of HO-1 in tumor tissues may have detrimental effect as HO-1 accelerates the formation of tumor neovasculature and provides the selective advantage for tumor cells to overcome the increased oxidative stress during tumorigenesis and during treatment. The inhibition of HO-1 has been proposed as an anti-cancer therapy, however, because of non-specific effects of known HO-1 inhibitors, the discovery of ideal drug lowering HO-1 expression/activity is still an open question. Importantly, in several types of cancer HO-1/CO system exerts opposite activities, making the possible treatment more complicated. All together indicates the complex role for HO-1/CO in various in vitro and in vivo conditions.

Thymidine phosphorylase expression is associated with time to progression in patients with metastatic colorectal cancer

Background

5-Fluorouracil (5-FU) is the cornerstone of chemotherapeutic treatment for patients with colorectal cancer. The enzyme thymidine phosphorylase (TP) catalyzes the conversion of 5-FU to its active metabolite, 5-fluoro-2’-deoxyuridine. TP is expressed in tumour epithelial cells and stromal cells, particularly in tumour-associated macrophages. These macrophages may affect sensitivity to chemotherapy. Previously, we identified TP as a predictive factor in microdissected tumour samples of patients with advanced colorectal cancer. In the present study, we analysed TP expression in tissues and associated stromal cells from patients with advanced colorectal cancer and associated TP levels to tumour response and time-to-event variables during first-line chemotherapy treatment. We also investigated the association between serum TP levels at the time of surgery and gene expression in primary tumour tissues.

Methods

This study included 125 patients with metastatic colorectal cancer treated with first-line 5-FU-based chemotherapy. To quantify TP gene expression levels in tumour tissues, real-time polymerase chain reaction was performed using the 7500 Fast Real-Time PCR system (Applied Biosystems, Foster City, CA, USA). TP protein concentration in matched serum samples was determined using an enzyme-linked immunosorbent assay system (USCN Life Science Inc.).

Results

The tumour response rate was 31%, and 30% of patients exhibited stable disease. No associations between TP expression level and age or gender were observed. Levels of TP mRNA in mucosa and tumours were positively correlated (r = 0.41, p < 0.01). No correlation between TP expression and tumour response rate was observed. Time to progression was significantly longer in patients with high TP expression (p < 0.01). Serum TP protein levels were not associated with tumour response or time-to-event variables and did not correlate with gene expression in tumour tissues.

Conclusions

High TP gene expression in non-microdissected tumour tissues of patients with advanced colorectal cancer correlates with longer time to progression, which could be related to treatment. These results are in contrast to previous studies where microdissected tumour cells were analysed and may be due to the presence of adjacent stromal cells. Serum TP protein expression does not correlate to TP gene expression in tissues of patients with advanced colorectal cancer.

Regulation and novel action of thymidine phosphorylase in non-small cell lung cancer: crosstalk with Nrf2 and HO-1

Proangiogenic enzyme thymidine phosphorylase (TP) is a promising target for anticancer therapy, yet its action in non-small cell lung carcinoma (NSCLC) is not fully understood. To elucidate its role in NSCLC tumor growth, NCI-H292 lung mucoepidermoid carcinoma cells and endothelial cells were engineered to overexpress TP by viral vector transduction. NSCLC cells with altered expression of transcription factor Nrf2 or its target gene heme oxygenase-1 (HO-1) were used to study the regulation of TP and the findings from pre-clinical models were related to gene expression data from clinical NSCLC specimens. Overexpression of Nrf2 or HO-1 resulted in upregulation of TP in NCI-H292 cells, an effect mimicked by treatment with an antioxidant N-acetylcysteine and partially reversed by HO-1 knockdown. Overexpression of TP attenuated cell proliferation and migration in vitro, but simultaneously enhanced angiogenic potential of cancer cells supplemented with thymidine. The latter was also observed for SK-MES-1 squamous cell carcinoma and NCI-H460 large cell carcinoma cells. TP-overexpressing NCI-H292 tumors in vivo exhibited better oxygenation and higher expression of IL-8, IL-1β and IL-6. TP overexpression in endothelial cells augmented their angiogenic properties which was associated with enhanced generation of HO-1 and VEGF. Correlation of TP with the expression of HO-1 and inflammatory cytokines was confirmed in clinical samples of NSCLC. Altogether, the increased expression of IL-1β and IL-6 together with proangiogenic effects of TP-expressing NSCLC on endothelium can contribute to tumor growth, implying TP as a target for antiangiogenesis in NSCLC.

Oncogenic potential of Nrf2 and its principal target protein heme oxygenase-1

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential component of cellular defense against a vast variety of endogenous and exogenous insults, including oxidative stress. Nrf2 acts as a master switch in the circuits upregulating the expression of various stress-response proteins, especially heme oxygenase-1 (HO-1). Paradoxically, however, recent studies have demonstrated oncogenic functions of Nrf2 and its major target protein HO-1. Levels of Nrf2 and HO-1 are elevated in many different types of human malignancies, which may facilitate the remodeling of the tumor microenvironment making it advantageous for the autonomic growth of cancer cells, metastasis, angiogenesis, and tolerance to chemotherapeutic agents and radiation and photodynamic therapy. In this context, the cellular stress response or cytoprotective signaling mediated via the Nrf2-HO-1 axis is hijacked by cancer cells for their growth advantage and survival of anticancer treatment. Therefore, Nrf2 and HO-1 may represent potential therapeutic targets in the management of cancer. This review highlights the roles of Nrf2 and HO-1 in proliferation of cancer cells, their tolerance/resistance to anticancer treatments, and metastasis or angiogenesis in tumor progression.

Simulation of a tetramer form of 5-chlorouracil: the vibrational spectra and molecular structure in the isolated and in the solid state by using DFT calculations

A Raman and FT-IR study of the biomolecule 5-chlorouracil in the solid state was carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify the assignments of the experimentally observed bands in the spectra. Calculations in the monomer form and comparisons with the experimental data in Ar matrix were also carried out. The error in the calculated frequencies was analyzed and reduced by using scaling equations and scaling factors deduced from the uracil molecule. The calculations with the B3LYP method and with the 6-31G(d,p) and 6-311+G(2d,p) basis set, appear in general to be useful, when combining with a scaling equation procedure or with the specific scale factors, for interpretation of the general features of the IR and Raman spectra. The scaled values were used in the reassignment of the IR and Raman experimental bands. Comparison of the results with those determined in uracil and 5-halogenated derivatives were performed. The substitution at 5-position of the uracil ring by a chlorine atom has a little effect on the geometric parameters.

Syntheses of 1-[2-(Phosphonomethoxy)Alkyl] thymine monophosphates and an evaluation of their inhibitory activity toward human thymidine phosphorylase

A series of new monophosphates of 1-[2-(phosphonomethoxy)alkyl]thymines, such as PMPTp(,) 3-MeO-PMPTp, HPMPTp, and FPMPTp, were synthesized and tested for their ability to inhibit human thymidine phosphorylase. Kinetic measurements of enzyme activity were performed using thymidine and inorganic phosphate as the substrates. The data show that some monophosphates provide a considerable increase of the multisubstrate inhibitory effect. The highest inhibitory potency was found with (R)-FPMPTp 4c (K (i) (dT) = 4.09 ± 0.47 μM, K (i)(P(i)) = 2.13 ± 0.29 μM) and (R) 3-MeO-PMPTp 4d (K (i) (dT) = 5.78 ± 0.71 μM, K (i)(P(i)) = 2.71 ± 0.37 μM).

Prognostic value of TP/PD-ECGF and thrombocytosis in gastric carcinoma

AIM

Thymidine phosphorylase/platelet-derived endothelial cell growth factor (TP/PD-ECGF) is upregulated in several cancers and plays an important role in angiogenesis and invasion of solid tumors. In this study, we investigated the expression of TP/PD-ECGF in gastric carcinoma and its correlation with clinicopathological features and thrombocytosis, and also determined their prognostic significance.

METHODS

Ninety-eight tissue specimens were resected from patients with gastric carcinoma. The immunohistochemical staining was used for expression of TP/PD-ECGF, platelet counts (PLT) of all patients before surgery were recorded. Patients were divided into high and low TP/PD-ECGF expression groups. Correlations among TP/PD-ECGF expression, PLT and the clinicopathological features of the patients and their prognostic values were studied statistically.

RESULTS

Sixty-one cases of high TP/PD-ECGF expression (62%) and 37 cases of low TP/PD-ECGF expression (38%) were detected. There were 21 patients with thrombocytosis (21%). The results show that high TP/PD-ECGF expression was correlated positively with thrombocytosis (P = 0.046, r = 0.20). The 5-year overall survival rate was 46.0% in patients with low TP/PD-ECGF expression, whereas it was only 14.8% in patients with high TP/PD-ECGF expression (P = 0.000). The 5-year survival rate for patients with and without thrombocytosis were 9.5% and 31.2%, respectively, and there was a significant difference between them (P = 0.0001). The multivariate Cox regression analysis showed that high TP/PD-ECGF expression and thrombocytosis would play a role as independent prognostic factors in patients with gastric carcinoma.

CONCLUSIONS

High TP/PD-ECGF expression and thrombocytosis can be regarded as valuable tools for predicting overall survival in patients with gastric carcinoma.

Platelet-derived endothelial cell growth factor/thymidine phosphorylase inhibitor augments radiotherapeutic efficacy in experimental colorectal cancer

PURPOSES

A lot of radiosensitizers have been developed. However, there are few to be available in the clinical setting. Thymidine phosphorylase inhibitor (TPI) regulates the phosphorolysis of thymidine to thymine and 2-deoxy-d-ribose-1-phosphate which is essential for tumor angiogenesis. The aim of this study is to evaluate whether TPI augments the radiotherapy for colorectal cancer in vitro and in vivo studies.

MATERIALS AND METHODS

The cytotoxicity of TPI with irradiation on HT29 and HCT116 cells was examined using MTT- and colony formation assay. At 10days post-inoculation, HT29 bearing orthotopic model mice (n=28) were divided into four groups and orally treated with TPI- (50mg/kg/day for 2weeks), radiation (RT, 2Gy×4: Total 8Gy), their combination or the vehicle. The mechanisms underlying the efficacy were assessed genomically and immunohistochemically.

RESULTS

Compared to each single treatment, the combination of TPI and RT synergistically inhibited the cell viability in a time- and dose-dependent manner. In the HT-29 bearing mice, the combination of TPI and RT reduced the tumor growth compared with RT alone. Notably, the mRNA levels of VEGF, TGF-β and, Rad51 and the protein expressions of VEGF and CD34 were significantly lower in the combination than the others. Furthermore, the combination markedly increased the TUNEL-positive cells, suggesting that TPI augments the cancer cell death through inhibition of angiogenesis and DNA repair system in the radiotherapy.

CONCLUSIONS

Our study first demonstrated that the combination of TPI and irradiation was effective in colon cancer. TPI would provide a promising therapeutic strategy as a radiosensitizer.

Angiogenic targets for potential disorders

This review shall familiarize the readers with various fundamental aspects of angiogenesis. Angiogenesis is a feature of a limited number of physiological processes like wound healing, ovulation, development of the corpus luteum, embryogenesis, lactating breast, during immune response, and during Inflammation. It is driven by a cocktail of growth factors and pro-angiogenic cytokines and is tempered by an equally diverse group of inhibitors of neovascularization. The properties and biological functions of angiogenic growth factors such as VEGF, FGF-2, nitric oxide, MMP, angiopoietin, TGF-β as well as various inhibitors such as angiostatin, endostatin, thrombospondin, canstatin, DII4, PEDF are discussed in this review with respect to their impact on angiogenic process. In recent years, it has become increasingly evident that excessive, insufficient, or abnormal angiogenesis contributes to the pathogenesis of many more disorders. A long list of disorders is characterized or caused by excessive or insufficient angiogenesis whereas several congenital or inherited diseases are also caused by abnormal vascular remodeling. It may be possible in the future to develop specific anti-angiogenic agents that offer a potential therapy for cancer and angiogenic diseases.

Thymidine phosphorylase in cancer cells stimulates human endothelial cell migration and invasion by the secretion of angiogenic factors

Background:

Thymidine phosphorylase (TP) is often overexpressed in tumours and has a role in tumour aggressiveness and angiogenesis. Here, we determined whether TP increased tumour invasion and whether TP-expressing cancer cells stimulated angiogenesis.

Methods:

Angiogenesis was studied by exposing endothelial cells (HUVECs) to conditioned medium (CM) derived from cancer cells with high (Colo320TP1=CT-CM, RT112/TP=RT-CM) and no TP expression after which migration (wound-healing-assay) and invasion (transwell-assay) were determined. The involvement of several angiogenic factors were examined by RT–PCR, ELISA and blocking antibodies.

Results:

Tumour invasion was not dependent on intrinsic TP expression. The CT-CM and RT-CM stimulated HUVEC-migration and invasion by about 15 and 40%, respectively. Inhibition by 10 μM TPI and 100 μM L-dR, blocked migration and reduced the invasion by 50–70%. Thymidine phosphorylase activity in HUVECs was increased by CT-CM. Reverse transcription-polymerase chain reaction revealed a higher mRNA expression of bFGF (Colo320TP1), IL-8 (RT112/TP) and TNF-α, but not VEGF. Blocking antibodies targeting these factors decreased the migration and invasion that was induced by the CT-CM and RT-CM, except for IL-8 in CT-CM and bFGF in RT-CM.

Conclusion:

In our cell line panels, TP did not increase the tumour invasion, but stimulated the migration and invasion of HUVECs by two different mechanisms. Hence, TP targeting seems to provide a potential additional strategy in the field of anti-angiogenic therapy.

Paracrine stimulation of endothelial cell motility and angiogenesis by platelet-derived deoxyribose-1-phosphate

OBJECTIVE

Micromolar concentrations of the proangiogenic metabolite deoxyribose-1-phosphate (dRP) were detected in platelet supernatants by mass spectrometry. In this study, we assessed whether the release of dRP by platelets stimulates endothelial cell migration and angiogenesis.

METHODS AND RESULTS

Protein-free supernatants from thrombin-stimulated platelets increased human umbilical vein endothelial cell migratory activity in transmigration and monolayer repair assays. This phenomenon was ablated by genetic silencing of dRP-generating uridine phosphorylase (UP) and thymidine phosphorylase (TP) or pharmacological inhibition of UP and restored by exogenous dRP. The stimulation of endothelial cell migration by platelet-derived dRP correlated with upregulation of integrin β(3), which was induced in a reactive oxygen species-dependent manner, and was mediated by the activity of the integrin heterodimer α(v)β(3). The physiological relevance of dRP release by platelets was confirmed in a chick chorioallantoic membrane assay, where the presence of this metabolite in platelet supernatants strongly induced capillary formation.

CONCLUSIONS

Platelet-derived dRP stimulates endothelial cell migration by upregulating integrin β(3) in a reactive oxygen species-dependent manner. As demonstrated by our in vivo experiments, this novel paracrine regulatory pathway is likely to play an important role in the stimulation of angiogenesis by platelets.

Accumulation of thymidine-derived sugars in thymidine phosphorylase overexpressing cells

Thymidine phosphorylase (TP) is often overexpressed in cancer and potentially plays a role in the stimulation of angiogenesis. The exact mechanism of angiogenesis induction is unclear, but is postulated to be related to thymidine-derived sugars. TP catalyzes the conversion of thymidine (TdR) to thymine and deoxyribose-1-phosphate (dR-1-P), which can be converted to dR-5-P, glyceraldehyde-3-phosphate (G3P) or deoxyribose (dR). However, it is unclear which sugar accumulates in this reaction. Therefore, in the TP overexpressing Colo320 TP1 and RT112/TP cells we determined by LC-MS/MS which sugars accumulated, their subcellular localization (using (3)H-TdR) and whether dR was secreted from the cells. In both TP-overexpressing cell lines, dR-1-P and dR-5-P accumulated intracellularly at high levels and dR was secreted extensively by the cells. A specific inhibitor of TP completely blocked TdR conversion, and thus no sugars were formed. To examine whether these sugars may be used for the production of angiogenic factors or other products, we determined with (3)H-TdR in which subcellular location these sugars accumulated. TdR-derived sugars accumulated in the cytoskeleton and to some extent in the cell membrane, while incorporation into the DNA was responsible for trapping in the nucleus. In conclusion, various metabolic routes were entered, of which the TdR-derived sugars accumulated in the cytoskeleton and membrane. Future studies should focus on which exact metabolic pathway is involved in the induction of angiogenesis.

Effects of thymidine phosphorylase on tumor aggressiveness and 5-fluorouracil sensitivity in cholangiocarcinoma

AIM: To evaluate the role of thymidine phosphorylase (TP) in cholangiocarcinoma using small interfering RNA (siRNA).

METHODS: A human cholangiocarcinoma-derived cell line KKU-M139, which has a naturally high level of endogenous TP, had TP expression transiently knocked down using siRNA. Cell growth, migration, in vitro angiogenesis, apoptosis, and cytotoxicity were assayed in TP knockdown and wild-type cell lines.

RESULTS: TP mRNA and protein expression were decreased by 87.1% ± 0.49% and 72.5% ± 3.2%, respectively, compared with control cells. Inhibition of TP significantly decreased migration of KKU-M139, and suppressed migration and tube formation of human umbilical vein endothelial cells. siRNA also reduced the ability of TP to resist hypoxia-induced apoptosis, while suppression of TP reduced the sensitivity of KKU-M139 to 5-fluorouracil.

CONCLUSION: Inhibition of TP may be beneficial in decreasing angiogenesis-dependent growth and migration of cholangiocarcinoma but may diminish the response to 5-fluorouracil chemotherapy.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

Thymidine phosphorylase (TP), also known as "platelet-derived endothelial cell growth factor" (PD-ECGF), is an enzyme, which is upregulated in a wide variety of solid tumors including breast and colorectal cancers. TP promotes tumor growth and metastasis by preventing apoptosis and inducing angiogenesis. Elevated levels of TP are associated with tumor aggressiveness and poor prognosis. Therefore, TP inhibitors are synthesized in an attempt to prevent tumor angiogenesis and metastasis. TP is also indispensable for the activation of the extensively used 5-fluorouracil prodrug capecitabine, which is clinically used for the treatment of colon and breast cancer. Clinical trials that combine capecitabine with TP-inducing therapies (such as taxanes or radiotherapy) suggest that increasing TP expression is an adequate strategy to enhance the antitumoral efficacy of capecitabine. Thus, TP plays a dual role in cancer development and therapy: on the one hand, TP inhibitors can abrogate the tumorigenic and metastatic properties of TP; on the other, TP activity is necessary for the activation of several chemotherapeutic drugs. This duality illustrates the complexity of the role of TP in tumor progression and in the clinical response to fluoropyrimidine-based chemotherapy.

Proteomics Identifies Thymidine Phosphorylase As a Key Regulator of the Angiogenic Potential of Colony-Forming Units and Endothelial Progenitor Cell Cultures

Endothelial progenitor cell (EPC) cultures and colony-forming units (CFUs) have been extensively studied for their therapeutic and diagnostic potential. Recent data suggest a role for EPCs in the release of proangiogenic factors. To identify factors secreted by EPCs, conditioned medium from EPC cultures and CFUs was analyzed using a matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometer combined with offline peptide separation by nanoflow liquid chromatography. Results were verified by RT-PCR and multiplex cytokine assays and complemented by a cellular proteomic analysis of cultured EPCs and CFUs using difference in-gel electrophoresis. This extensive proteomic analysis revealed the presence of the proangiogenic factor thymidine phosphorylase (TP). Functional experiments demonstrated that inhibition of TP by 5-bromo-6-amino-uracil or gene silencing resulted in a significant increase in basal and oxidative stress-induced apoptosis, whereas supplementation with 2-deoxy- d -ribose-1-phosphate (dRP), the enzymatic product of TP, abrogated this effect. Moreover, dRP produced in EPC cultures stimulated endothelial cell migration in a paracrine manner, as demonstrated by gene-silencing experiments in transmigration and wound repair assays. RGD peptides and inhibitory antibodies to integrin αvβ3 attenuated the effect of conditioned medium from EPC cultures on endothelial migration. Finally, the effect of TP on angiogenesis was investigated by implantation of Matrigel plugs in mice. In these in vivo experiments, dRP strongly promoted neovascularization. Our data support the concept that EPCs exert their proangiogenic activity in a paracrine manner and demonstrate a key role of TP activity in their survival and proangiogenic potential.

Adventitial delivery of platelet-derived endothelial cell growth factor gene prevented intimal hyperplasia of vein graft

BACKGROUND

Platelet-derived endothelial cell growth factor (PD-ECGF), also known as thymidine phosphorylase (TP) reportedly inhibits vascular smooth muscle cells (VSMCs) migration and proliferation. We hypothesized that adventitial administration of the PD-ECGF/TP gene will suppress intimal hyperplasia and prevent vein graft failure.

METHODS

The study used 68 female rabbits. Rabbit jugular vein was autogenously transplanted into carotid artery with a cuff anastomotic technique. To define vascular wall gene transfer efficiency, poloxamer hydrogel (20%) containing plasmid vector encoding the LacZ gene and different concentrations of trypsin (0%, 0.1%, 0.25%, and 0.5%, n = 5 for each group) was applied to the adventitia of the vein graft. Gene transfer efficiency was evaluated 7 days later by X-gal staining. An additional 48 rabbits received poloxamer hydrogel (20%) containing 0.25% trypsin and the human PD-ECGF/TP gene, LacZ gene, or saline. Intima thickness was evaluated at 2 and 8 weeks after grafting (n = 8 for each group at each time point). Transgene expression was examined by reverse transcriptase-polymerase chain reaction, immunoblotting assay, and immunohistochemical staining. Immunohistochemical staining was also used to determine VSMC proliferation, heme oxygenase-1 expression, and macrophage infiltration.

RESULTS

Incorporation of trypsin into the poloxamer hydrogel significantly increased vessel wall gene transfer. Trypsin at 0.25% and 0.5% resulted in higher gene transfer at the same level without effecting intimal hyperplasia and inflammation; thus, trypsin at 0.25% concentration was used for subsequent experiments. Compared with the LacZ and saline groups, grafts receiving the PD-ECGF/TP gene significantly reduced intimal thickness at 2 and 8 weeks after treatment. The ratio of proliferative VSMC was lower in PD-ECGF/TP treated grafts. Histologic examination of the PD-ECGF/TP transgene grafts demonstrated high expression of heme oxygenase-1, which has been reported to inhibit VSMC proliferation, suggesting that heme oxygenase-1 may be important in the inhibition effect of PD-ECGF/TP on VSMC. No neoplastic or morphologic changes were found in the remote organs.

CONCLUSIONS

A safe and highly efficient gene transfer method was developed by using poloxamer hydrogel and a low concentration of trypsin. Neointimal hyperplasia was significantly reduced by adventitial application of the PD-ECGF/TP gene to the vein graft. Our data suggest that adventitial delivery of the PD-ECGF/TP gene after grafting may be promising method for preventing vein graft failure.

Heme oxygenase-1 and the vascular bed: from molecular mechanisms to therapeutic opportunities

Heme oxygenase-1, an enzyme degrading heme to carbon monoxide, iron, and biliverdin, has been recognized as playing a crucial role in cellular defense against stressful conditions, not only related to heme release. HO-1 protects endothelial cells from apoptosis, is involved in blood-vessel relaxation regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in blood-vessel formation by means of angiogenesis and vasculogenesis. The latter functions link HO-1 not only to cardiovascular ischemia but also to many other conditions that, like development, wound healing, or cancer, are dependent on neovascularization. The aim of this comprehensive review is to address the mechanisms of HO-1 regulation and function in cardiovascular physiology and pathology and to demonstrate some possible applications of the vast knowledge generated so far. Recent data provide powerful evidence for the involvement of HO-1 in the therapeutic effect of drugs used in cardiovascular diseases. Novel studies open the possibilities of application of HO-1 for gene and cell therapy. Therefore, research in forthcoming years should help to elucidate both the real role of HO-1 in the effect of drugs and the clinical feasibility of HO-1-based cell and gene therapy, creating the effective therapeutic avenues for this refined antioxidant system.

Heme oxygenase-1 and carbon monoxide in vascular pathobiology: focus on angiogenesis

Angiogenesis involves the formation of new blood vessels and is critical for fundamental events such as development and repair after injury. Perturbances in angiogenesis contribute to the pathogenesis of diverse clinical conditions including cancer, complications of diabetes mellitus, ischemia/reperfusion injury of the heart and other organs, and preeclampsia, as well as a number of inflammatory disorders. Recent work has identified heme oxygenase-1 and its gaseous product, carbon monoxide, to possess potent proangiogenic properties in addition to well-recognized antiinflammatory, antioxidant, and antiapoptotic effects. Angiogenic factors, such as vascular endothelial growth factor and stromal cell-derived factor-1, mediate their proangiogenic effects through induction of heme oxygenase-1, making it an attractive target for therapeutic intervention. This review will provide an overview of the role of heme oxygenase-1 and carbon monoxide in angiogenesis.

Induction of platelet derived-endothelial cell growth factor in the brain after ischemia

OBJECTIVES

Platelet derived-endothelial cell growth factor (PD-ECGF) is a highly potent angiogenic factor. Although angiogenesis plays an active role in pathophysiology of stroke, the expression pattern of this molecule in ischemic brain has not been investigated. In the present study, therefore, we investigated the change of PD-ECGF expression in the brain after ischemia.

METHODS

Using male Wistar rats, the right middle cerebral artery was occluded by a nylon thread for 90 minutes. The animals were decapitated 3 hours, 1, 4 and 10 days after the reperfusion, and frozen sections were prepared. We then performed immunohistochemistry for PD-ECGF and identified the cell phenotype which strongly expressed it by fluorescent double staining.

RESULTS

In the sham-operated brain, only small numbers of cells slightly expressed PD-ECGF. The number of positively stained cells increased at the peri-ischemic area from hour 3 of reperfusion. Not only small-sized cells but also large-sized cells became stained. The number of stained cells further increased, and peaked at day 4 for large-sized cells and at day 10 as to small-sized cells. Fluorescent double staining revealed that both large-sized and small-sized cells were neurons, indicating that neurons are the main source of PD-ECGF production in the ischemic brain.

DISCUSSION

PD-ECGF has a strong angiogenic property without vascular permeability increasing effect. This molecule may have a therapeutic potential for ischemic stroke treatment.

Evidence for the involvement of p38 MAP kinase in the action of the vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA)

AIMS

DMXAA (AS1404), a small-molecule vascular disrupting agent that has now completed Phase II clinical trial, induces endothelial cell apoptosis, increased vascular permeability and decreased tumour blood flow in vivo. Its action is incompletely understood and we wished to develop an in vitro system to study its effects.

METHODS

Human tumour cell lines developed from aggressive tumours were grown on Matrigel to simulate a tumour microenvironment. Cells were analysed by light microscopy and by gene expression profiling.

RESULTS

Several cell lines formed networks when grown on Matrigel and the NZM7 melanoma cell line was chosen for further study. Addition of DMXAA at a clinically achievable concentration (30 microg/mL) prevented network formation, but co-addition of SB203580 (10 microM), a selective inhibitor of p38 MAP kinase, reversed the effect of DMXAA and restored network formation. Analysis of expression genes for endothelial and related functions showed that cells growing on Matrigel expressed a pattern similar to that of NZM7 cells growing as xenografts in vivo but different from that of cells grown on standard tissue culture plates. Addition of DMXAA resulted in the inhibition of expression of several genes including the transcriptional activator Ets1 and matrix metalloproteinase-2 (MMP2), but co-addition of SB203580 did not reverse these effects of DMXAA on gene expression.

CONCLUSION

The results suggest that p38 MAP kinase plays an important role in the action of DMXAA and that growth of tumour cells on Matrigel provides a promising model for further studies on the action of this drug.

Platelet-derived endothelial cell growth factor gene therapy for limb ischemia

OBJECTIVES

Platelet-derived endothelial cell growth factor (PD-ECGF) is identical to thymidine phosphorylase (TP), and it can induce angiogenesis, including arteriogenesis, in chronically ischemic canine myocardium. Because its effect on peripheral arterial disease has not been elucidated, we investigated whether overexpression of PD-ECGF/TP could ameliorate chronic limb ischemia in rabbits.

METHODS

Left femoral arteries were resected from 24 male rabbits. After 10 days, a plasmid vector containing human PD-ECGF/TP complimentary DNA was injected into 10 sites in the adductor muscles. Control groups received either the LacZ plasmid vector or saline vehicle only (n = 8 per group). Blood pressure was measured in the calf before surgery, at the onset of ischemia, 10 days later, and 20 and 30 days after gene transfer. Collateral vessel development and limb perfusion were assessed by angiography, and resected tissues underwent molecular and histologic examination.

RESULTS

In the PD-ECGF/TP group, human PD-ECGF/TP messenger RNA and protein were still detected at 30 days after treatment. Calf blood pressure decreased significantly after femoral artery resection in all three groups. It subsequently showed a greater increase in the PD-ECGF/TP group than in either control group, and the difference was significant at 20 days after treatment (PD-ECGF/TP, 97.4 +/- 7.4; LacZ, 58.6 +/- 6.9; saline, 41.3 +/- 3.6). Immunohistochemical staining demonstrated an increased ratio of capillaries and arterioles to muscle fibers in the PD-ECGF/TP group (2.14 +/- 0.13 and 1.51 +/- 0.06), but not in the LacZ group (1.39 +/- 0.04 and 0.71 +/- 0.05) or the saline group (1.34 +/- 0.05 and 0.71 +/- 0.04, P < .01). The angiographic score was higher in the PD-ECGF/TP group (0.96 +/- 0.08) than in the LacZ group (0.50 +/- 0.02) or saline group (0.51 +/- 0.03) at 30 days after gene transfer (P < .01).

CONCLUSIONS

This study demonstrated that PD-ECGF/TP gene transfer induced angiogenesis and decreased ischemia in a rabbit hindlimb model by promoting arteriogenesis, suggesting that targeting this gene may be a promising therapeutic strategy for peripheral vascular disease.

Anti-angiogenic and anti-inflammatory effects of statins: relevance to anti-cancer therapy

Angiogenesis is indispensable for the growth of solid tumors and angiogenic factors are also involved in the progression of hematological malignancies. Targeting the formation of blood vessels is therefore regarded as a promising strategy in cancer therapy. Interestingly, besides demonstration of some beneficial effects of novel anti-angiogenic compounds, recent data on the activity of already available drugs point to their potential application in anti-angiogenic therapy. Among these are the statins, the inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Statins are very efficient in the treatment of hypercholesterolemia in cardiovascular disorders; however, their effects are pleiotropic and some are not directly related to the inhibition of cholesterol synthesis. Some reports particularly highlight the pro-angiogenic effects of statins, which are caused by low, nanomolar concentrations and are regarded as beneficial for the treatment of cardiovascular diseases. On the other hand, the anti-angiogenic activities, observed at micromolar concentrations of statins, may be of special significance for cancer therapy. Those effects are caused by the inhibition of both proliferation and migration and induction of apoptosis in endothelial cells. Moreover, the statin-mediated inhibition of vascular endothelial growth factor synthesis, the major angiogenic mediator, may contribute to the attenuation of angiogenesis. It has been suggested that the anti-cancer effect of statins can be potentially exploited for the cancer therapy. However, several clinical trials aimed at the inhibition of tumor growth by treatment with very high doses of statins did not provide conclusive data. Herein, the reasons for those outcomes are discussed and the rationale for further studies is presented.

Proliferating fibroblasts at the invading tumour edge of colorectal adenocarcinomas are associated with endogenous markers of hypoxia, acidity, and oxidative stress

BACKGROUND

Stroma frequently forms at sites of active tumour invasion, and may be important for tumour growth and progression. The term "stromatogenesis" is used to describe this unique process that involves host peritumorous fibroblasts and is very different to reactive fibrosis.

AIMS/METHODS

To investigate the activation status of host fibroblasts at the invading tumour edge, assessed as MIB1 proliferation index and thymidine phosphorylase (TP) expression. Results were related to vascular density and certain properties of invading cancer cells-MIB1 proliferation activity, TP expression, expression of endogenous markers of hypoxia (hypoxia inducible factor-1alpha; HIF1alpha) and acidity (lactate dehydrogenase-5; LDH5). Standard immunohistochemical techniques were applied to 150 colorectal adenocarcinomas.

RESULTS

Normal fibroblasts at the tumour edge had a median MIB1 index of 2%-significantly higher than normal submucosal fibroblasts (0.3%) and significantly lower than cancer cells (40%). Normal peritumorous fibroblasts with a proliferation rate above the median strongly expressed TP and were supported by an increased vascular network. Cancer cells close to these fibroblasts had a high MIB1 proliferative index, high HIF1alpha and LDH5 reactivity, and a clear trend to extramural extension. All associations were significant.

CONCLUSIONS

These results suggest that activated fibroblastic status at the invading tumour front sets the stage for stromatogenesis and new blood vessel formation, facilitating deep transmural invasion in colorectal adenocarcinomas. This complicity of peritumorous fibroblasts in the overall aggressiveness/invasive and metastatic ability of colorectal tumours, occurring within the framework of cancer-stromal cell interactions, is probably favoured by the altered microenvironmental conditions of hypoxia and acidity.

Thymidine phosphorylase profiles in nonmalignant and malignant pancreatic tissue. Potential therapeutic role of capecitabine on tumoral and endothelial cells and tumor-infiltrating macrophages

The drug capecitabine (CAP) is a thymidine Pi-deoxyribosyltransferase (TP) activated oral fluorpyrimidine that generates 5-fluorouracil (5-FU), preferentially, within tumors. Here, in 38 patients with pancreatic cancer we analyzed immunohistochemical TP expression in pancreatic cancer tissue (PCT) and adjacent nonmalignant pancreatic tissue (ANMPT). In addition, a correlation with the main clinical pathological features was made. Furthermore, TP-positive macrophages (MO) isolated from neoplastic tissue were determined. The mean of TP-positive epithelial cells and endothelial cells in terms of microvessel density was significantly higher in PCT than in ANMPT. Because pancreatic cancer is sensitive to 5-FU, TP-activated oral CAP in tumoral and endothelial cells and tumor infiltrating MO could increase the concentration of 5-FU at tumor site, thus resulting in an enhanced antitumor activity.

Inhibition of thymidine phosphorylase (PD-ECGF) from SD-lymphoma by phosphonomethoxyalkyl thymines

A series of thymine phosphonomethoxyalkyl derivatives were evaluated for their ability to inhibit thymidine phosphorylase (dThdPase) purified from rat spontaneous T-cell lymphoma. A kinetic study of thymidine phosphorolysis catalyzed by dThdPase was performed with thymidine and/or inorganic phosphate as substrates. Data show that the substantial inhibitory effect of these acyclic nucleotide analogues is decreasing in the order of (R)-FPMPT>(S)-FPMPT>or=(R)-HPMPT>(S)-PMPT>(S)-HPMPT>PMET>or=(R)-PMPT. The inhibitory potency (K(i)/(dThd)K(m)) of the most efficient inhibitors from this series against T-cell lymphoma enzyme is 0.0026 for (R)-FPMPT and 0.0048 for (S)-FPMPT. The studied compounds do not inhibit Escherichia coli and human enzyme and possess lower inhibitory potency against rat liver thymidine phosphorylase.

Nitric oxide modulates hepatocyte growth factor/scatter factor-induced angiogenesis

OBJECTIVE

There is limited knowledge about potential therapeutic targets in Hepatocyte growth factor/scatter factor (HGF)-induced pathophysiological angiogenesis. Recent candidates have included phosphatidylinositol-3-kinase, which is an upstream activator for endothelial nitric oxide (NO) synthase (NOS III). The current study is the first to evaluate the possible involvement of NOS-NO cascade in HGF-induced angiogenesis.

METHODS AND RESULTS

NOS III inhibitors blocked the HGF-induced functional neovascularization in vivo, as quantified using vessel counts, 133Xe-clearance, and immunohistology. This was reversed by L-arginine. Western blot analysis of HGF-treated cells also revealed a temporal increase in HGF-induced phosphorylation. In a deconstructional approach, HGF induced the proliferation and chemokinesis of human endothelial cells. These phenotypic effects were inhibited by NOS inhibitors, L-NAME and L-NIO, and the NO scavenger, carboxy PTIO, but unaltered by 1400W, a NOS II inhibitor. This inhibition was reversed by spermine NONOate, a NO donor, which independently exerted a biphasic effect on endothelial cell proliferation. The modulation of NO did not alter HGF-induced chemoinvasion of endothelial cells, while spermine-NONOate destabilized HGF-induced tubulogenesis, suggesting that a single assay is not sufficient for predicting the final phenotypic outcome on angiogenesis.

CONCLUSIONS

The study is the first to demonstrate that the NOS III nitric oxide is a key signal cascade in HGF-induced angiogenesis, and represents a promising target for the clinical management of pathological conditions characterized by overt HGF signaling.

Thymidine phosphorylase gene transfer inhibits vascular smooth muscle cell proliferation by upregulating heme oxygenase-1 and p27KIP1

OBJECTIVE

Thymidine phosphorylase (TP) reportedly promotes endothelial cell migration and induces heme oxygenase (HO)-1 expression. However, its effect on vascular smooth muscle cells (VSMCs) is poorly understood. In this study, we examined the effect of TP on VSMCs in vitro and in vivo.

METHODS AND RESULTS

Phagemid vector encoding human TP gene was transfected into rat VSMCs, and a clone overexpressing TP was selected (C2). C2 showed a slower migration and proliferation than VSMCs cloned with empty vector (pC) under basal, serum-stimulated, and hypoxic conditions. This decrease in proliferation correlated with TP-induced HO-1 expression and was reversed by inhibitors of either TP or HO activity. Furthermore, in C2, the cyclin-dependent kinase inhibitor (p27KIP1) was much more abundant than in pC, and the cell cycle was arrested at the G1 phase. TP or HO activity inhibitors decreased p27(KIP1) expression in C2 to the level seen in pC. Adventitial TP gene delivery significantly reduced neointimal VSMC migration and neointima formation in balloon-injured rat carotid arteries.

CONCLUSIONS

TP overexpression upregulated HO-1 expression and consequently increased p27(KIP1) in cultured VSMCs, and inhibited VSMC migration and proliferation in vitro and in vivo. TP represents a promising target for treating vascular obstructive disease.

Bioactive Glass Stimulates the Secretion of Angiogenic Growth Factors and Angiogenesis in Vitro

Neovascularization of tissue-engineered constructs remains a limiting factor for the engineering of larger tissue constructs. Attempts to stimulate neovascularization, using recombinant protein or gene transfer of angiogenic growth factors, have been proposed; however, these approaches have been associated with problems regarding the delivery and duration of exposure of the growth factor. This study was performed to determine the ability of biologically active glass to stimulate the secretion of angiogenic growth factors from human stromal cells and subsequent angiogenesis. CCD18Co human fibroblasts were cultured on tissue culture surfaces coated with specific quantities of 45S5 Bioglass particles. At 24-, 48-, and 72-h intervals the gene expression of vascular endothelial growth factor (VEGF) and the protein secretion of VEGF and basic fibroblast growth factor (bFGF) from fibroblasts were measured. The effect of conditioned medium collected from Bioglass-stimulated fibroblasts on human dermal microvascular endothelial cells was assessed using in vitro angiogenesis assays. Results showed that surfaces coated with Bioglass produced a significant increase in the secretion of VEGF and bFGF. Conditioned medium from stimulated fibroblasts significantly increased the proliferation of human dermal microvascular endothelial cells and induced a significant increase in the formation of anastomosed networks of human endothelial cell tubules. It is concluded that the ability of 45S5 Bioglass to stimulate the release of angiogenic growth factors and to promote angiogenesis provides a novel alternative approach for stimulating neovascularization of tissue-engineered constructs.

Transfection of thymidine phosphorylase cDNA to human hepatocellular carcinoma cells enhances sensitivity to fluoropyrimidine but augments endothelial cell migration

PURPOSE

To investigate the effects on sensitivity to fluoropyrimidine and endothelial cell (EC) migration by transfection with thymidine phosphorylase (TP) cDNA to a hepatocellular carcinoma (HCC) cell line SMMC-7721.

METHODS

SMMC-7721 was transfected with pcDNA3.1/zeo (+) with human TP cDNA. TP mRNA expression was determined by RT-PCR. Sensitivity to fluoropyrimidine was determined by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide (MTT) assay. Induction of EC migration was detected by Boyden chamber assay.

RESULTS

The construction of pcDNA3.1/zeo(+)-TP was verified by digestion with restriction endonuclease Apa1. When comparison was made between SMMC-7721 cell clone transfected with pcDNA3.1/zeo(+)-TP (S-TP) and control clone transfected with pcDNA3.1/zeo(+) (S-vector), we found that TP mRNA expression level was much higher in S-TP, being 2.09+/-0.16 vs 0.48+/-0.06 in S-vector (P < 0.01), sensitivity to 5'-deoxy-5-fluorouridine (5'-dFUrd, a prodrug of 5-fluorouracil) in S-TP was significantly enhanced compared with that in S-vector (IC(50); 56.81+/-9.85 micromol/l vs 162.25+/-11.03 micromol/l, P < 0.01), and the culture medium of S-TP possessed more potential to induce EC migration than that of S-vector (the number of ECs appearing on the outer surfaces of the membrane was 275+/-29 vs 122+/-35 per field, P < 0.01).

CONCLUSION

Sensitivity to 5'-dFUrd could be enhanced by transfection with TP cDNA for SMMC-7721 cells. However, EC migration was also promoted at the same time. Therefore, transfection with TP alone might have no potential to enhance anti-tumoral effects of fluoropyrimidine in HCC.

Enzymatic transition states: thermodynamics, dynamics and analogue design

Kinetic isotope effects and computational chemistry have defined the transition state structures for several members of the N-ribosyltransferase family. Transition state analogues designed to mimic their cognate transition state structures are among the most powerful enzyme inhibitors. In complexes of N-ribosyltransferases with their transition state analogues, the dynamic nature of the transition state is converted to an ordered, thermodynamic structure closely related to the transition state. This phenomenon is documented by peptide bond H/D exchange, crystallography and computational chemistry. Complexes with substrate, transition state and product analogues reveal reaction coordinate motion and catalytic interactions. Isotope-edited spectroscopic analysis and binding specificity of these complexes provides information about specific enzyme-transition state contacts. In combination with protein dynamic QM/MM models, it is proposed that the transition state is reached by stochastic dynamic excursions of the protein groups near the substrates in the closed conformation. Examples from fully dissociated (D(N) *A(N)), hybrid (D(N)A(N)) and symmetric nucleophilic displacement (A(N)D(N)) transition states are found in the N-ribosyltransferases. The success of transition state analogue inhibitor design based on kinetic isotope effects validates this approach to understanding enzymatic transition states.

Blockage of 2-deoxy-D-ribose-induced angiogenesis with rapamycin counteracts a thymidine phosphorylase-based escape mechanism available for colon cancer under 5-fluorouracil therapy

PURPOSE

Colorectal neoplasms remain a leading cause of cancer-related deaths. A recognized weakness of conventional 5-fluorouracil (5-FU) therapy relates to expression of the intracellular enzyme, thymidine phosphorylase (TP). Although TP promotes 5-FU cytotoxicity, TP-derived 2-deoxy-D-ribose (dRib) counterproductively stimulates tumor angiogenesis. Here, the newly discovered antiangiogenic drug rapamycin was combined with 5-FU to counteract the potential escape mechanism of dRib-induced angiogenesis.

EXPERIMENTAL DESIGN

Orthotopic tumor growth was assessed in rapamycin and 5-FU-treated BALB/c mice with TP-expressing CT-26 colon adenocarcinoma cells. To examine liver metastasis, green-fluorescent protein-transfected CT-26 cells were visualized by fluorescence microscopy after intraportal injection. Cell counting and Ki67 staining were used to determine in vitro and in vivo cell expansion, respectively. In vitro angiogenic effects of dRib were assessed with endothelial cell migration and aortic ring assays. Western blotting detected dRib effects on p70/S6 kinase activation.

RESULTS

Rapamycin treatment of mice bearing orthotopic tumors inhibited tumor growth more than did 5-FU, and mice treated with both drugs typically developed no tumors. In the liver metastasis assay, combination therapy blocked metastatic expansion of solitary tumor cells. Interestingly, complex drug activities were suggested by tumor-cell proliferation being more sensitive to 5-FU than to rapamycin in vitro, but more sensitive to rapamycin in vivo. With regard to angiogenesis, dRib-induced endothelial cell migration and aortic ring formation were completely abrogated by rapamycin, correlating with blockage of dRib-induced p70/S6 kinase activation in endothelial cells.

CONCLUSIONS

Inhibition of dRib-induced angiogenesis with rapamycin counteracts a potential TP-based escape mechanism for colorectal cancer under 5-FU therapy, introducing a novel, clinically feasible, combination treatment option for this common neoplasm.

Gene therapy for chronic myocardial ischemia using platelet-derived endothelial cell growth factor in dogs

Platelet-derived endothelial cell growth factor (PD-ECGF), also known as thymidine phosphorylase (TP), has been reported to possess angiogenic activity and to inhibit apoptosis. This study was performed to determine whether PD-ECGF/TP can be used to ameliorate chronic myocardial ischemia. Myocardial ischemia was created in 40 mongrel dogs by placement of an ameroid constrictor on the proximal left anterior descending coronary artery (LAD). Plasmid vector encoding human PD-ECGF/TP cDNA (pCIhTP group; n = 12), empty vector pCI (pCI group; n = 12), or saline (Saline group; n = 12) was directly injected into the LAD territory 3 wk after ameroid constrictor implantation. Myocardial blood flow was detected using PET at baseline, 3 wk after ameroid constrictor implantation, and 2 wk after therapeutic treatment. At the end of the experiment, the hearts were isolated for biological and histological analysis. In the pCIhTP group, the transfected heart strongly expressed PD-ECGF/TP. The size of the infarct was smaller in the pCIhTP group than in the pCI or Saline group. The number of apoptotic myocardial cells was decreased in the pCIhTP group compared with the control groups based on triple immunohistochemical staining for von Willebrand factor, alpha-actin smooth muscle cells, and single-strand DNA. The level of proapoptotic protein Bax markedly decreased in the pCIhTP group compared with the other groups. Double immunohistochemical staining for von Willebrand factor and alpha-actin smooth muscle cells demonstrated that angiogenesis and arteriogenesis occurred, and paralleled the changes in myocardial blood flow and myocardial function in the pCIhTP group. We conclude that genetic approaches using PD-ECGF/TP to target the myocardium are effective for alleviating chronic myocardial ischemia.

Modulating angiogenesis: the yin and the yang in ginseng

BACKGROUND

Ginseng is a commonly used nutraceutical. Intriguingly, existing literature reports both wound-healing and antitumor effects of ginseng extract through opposing activities on the vascular system. To elucidate this perplexity, we merged a chemical fingerprinting approach with a deconstructional study of the effects of pure molecules from ginseng extract on angiogenesis.

METHODS AND RESULTS

A mass spectrometric compositional analysis of American, Chinese and Korean, and Sanqi ginseng revealed distinct "sterol ginsenoside" fingerprints, especially in the ratio between a triol, Rg1, and a diol, Rb1, the 2 most prevalent constituents. Using a Matrigel implant model and reconstituting the extracts using distinct ratios of the 2 ginsenosides, we demonstrate that the dominance of Rg1 leads to angiogenesis, whereas Rb1 exerts an opposing effect. Rg1 also promoted functional neovascularization into a polymer scaffold in vivo and the proliferation of, chemoinvasion of, and tubulogenesis by endothelial cells in vitro, an effect mediated through the expression of nitric oxide synthase and the phosphatidylinositol-3 kinase-->Akt pathway. In contrast, Rb1 inhibited the earliest step in angiogenesis, the chemoinvasion of endothelial cells.

CONCLUSIONS

The present study explains, for the first time, the ambiguity about the effects of ginseng in vascular pathophysiology based on the existence of opposing active principles in the extract. We also unraveled a speciogeographic variation impinging on the compositional fingerprint that may modulate the final phenotype. This emphasizes the need for regulations standardizing herbal therapy, currently under the Dietary Supplement and Health Education Act. Furthermore, we propose that Rg1 could be a prototype for a novel group of nonpeptide molecules that can induce therapeutic angiogenesis, such as in wound healing.

A dual-color fluorescence imaging-based system for the dissection of antiangiogenic and chemotherapeutic activity of molecules

We have developed a simple yet sensitive dual color fluorescence-based technique for dissecting the tumor-neovascularization relationship and evaluated the susceptibility of each component to therapeutic interventions. Green fluorescent protein (GFP)-expressing melanoma cells were cocultured with endothelial cells on different three-dimensional (3-D) matrices and exposed to multiple growth factors and molecules with established anti-angiogenic or anticancer activities. Cells were fixed and stained with propidium iodide, imaged using a confocal microscope, and stereologically analyzed. Three-dimensionality of the system was tested by depth-coding and pseudocolor 3-D reconstruction in the z-axis. Selective ablation of the tumor cells was affected by the anthracycline antibiotic doxorubicin. Treatment with vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) promoted the neovascular responses on matrigel and collagen-1 matrices. VEGF-induced angiogenesis was inhibited after treatment with combretastatin and thalidomide. In contrast, HGF exerted a protective effect against these anti-angiogenics in a matrigel matrix. However, this effect was lost when the matrix was substituted with collagen, suggesting that the extracellular matrix impinges on cellular function, possibly through an Akt-mediated mechanism. The VEGF-receptor antagonist PTK787 also selectively ablated the VEGF-induced angiogenic effect without inhibiting the HGF-induced response, demonstrating the sensitivity of the system to detect modulation of distinct signal cascades. The current model encompasses the possibility of studying tumor-angiogenesis-matrix interaction on the same platform, expanding the rapid screening of novel molecules in a simulated clinicopathological setting.

Correlation of platelet-derived endothelial cell growth factor/ thymidine phosphorylase and Cox-2 expression to angiogenesis and apoptosis in gastric carcinoma

AIM: To investigate the relationship of the expression of platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) and Cox-2 to angiogenesis and apoptosis in gastric carcinoma.

METHODS: The expression of PD-ECGF and Cox-2 and the microvascular density (MVD) level were examined by immunohistochemical staining, and apoptotic index (AI) was examined by flow cytometry in 67 cases of gastric carcinoma.

RESULTS: There was a close correlation between PD-ECGF expression and several clinicopathological factors including lymph node metastasis (P < 0.05), histology (P < 0.05) and histological type (P < 0.05). The expression of Cox-2 was closely related to lymph node metastasis (P < 0.05); The expression of PD-ECGF or Cox-2 in gastric cancer tissues was positively correlated with MVD (P < 0.01) and negatively correlated with AI (P < 0.01). Combined analysis of PD-ECGF and Cox-2 showed that tumors with positive expression of both factors had a significantly lower AI and a significantly higher MVD than tumors with negative expression of both factors (P < 0.01).

CONCLUSION: Up-regulation of PD-ECGF and Cox-2 may facilitate tumor angiogenesis and inhibit apoptosis in gastric carcinoma, indicating cooperation between PD-ECGF and Cox-2 in gastric cancer, and therefore promote tumor growth and metastasis.

The nucleoside derivative 5'-O-trityl-inosine (KIN59) suppresses thymidine phosphorylase-triggered angiogenesis via a noncompetitive mechanism of action

Thymidine phosphorylase (TPase) catalyzes the reversible phosphorolysis of pyrimidine deoxynucleosides to 2-deoxy-d-ribose-1-phosphate and their respective pyrimidine bases. The enzymatic activity of TPase was found to be essential for its angiogenesis-stimulating properties. All of the previously described TPase inhibitors are either pyrimidine analogues that interact with the nucleoside-binding site of the enzyme or modified purine derivatives that mimic the pyrimidine structure and either compete with thymidine or act as a multisubstrate (competitive) inhibitor. We now describe the inhibitory activity of the purine riboside derivative KIN59 (5'-O-tritylinosine) against human and bacterial recombinant TPase and TPase-induced angiogenesis. In contrast to previously described TPase inhibitors, KIN59 does not compete with the pyrimidine nucleoside or the phosphate-binding site of the enzyme but noncompetitively inhibits TPase when thymidine or phosphate is used as the variable substrate. In addition, KIN59 was far more active than other TPase inhibitors, previously tested by us, against TPase-induced angiogenesis in the chorioallantoic membrane assay. The observed anti-angiogenic effect of KIN59 was not accompanied by inflammation or any visible toxicity. Inosine did not inhibit the enzymatic or angiogenic activity of the enzyme, indicating that the 5'-O-trityl group in KIN59 is essential for the observed effects. In contrast with current concepts, our data indicate that the angiogenic activity of TPase is not solely directed through its functional nucleoside and phosphate-binding sites. Other regulatory (allosteric) site(s) in TPase may play an important role in the mechanism of TPase-triggered angiogenesis stimulation and apoptosis inhibition. Identification of these site(s) is important to obtain a better insight into the molecular role of TPase in the progression of cancer and angiogenic diseases.