Thymidine phosphorylase promotes malignant progression in hepatocellular carcinoma through pentose Warburg effect.

Tumor progression is dependent on metabolic reprogramming. Metastasis and vasculogenic mimicry (VM) are typical characteristics of tumor progression. The relationship among metastasis, VM, and metabolic reprogramming remains unclear. In this study, we identified the novel role of Twist1, a VM regulator, in the transcriptional regulation of thymidine phosphorylase (TP) expression. TP promoted the extracellular metabolism of thymidine into ATP and amino acids through the pentose Warburg effect by coupling the pentose phosphate pathway and glycolysis. Moreover, Twist1 relied on TP-induced metabolic reprogramming to promote hepatocellular carcinoma (HCC) metastasis and VM formation mediated by VE-Cad, VEGFR1, and VEGFR2 in vitro and in vivo. The TP inhibitor tipiracil reduced the effect of TP on promoting HCC VM formation and metastasis. Hence, TP, when transcriptionally activated by Twist1, promotes HCC VM formation and metastasis through the pentose Warburg effect and contributes to tumor progression.

Thymidine phosphorylase promotes metastasis and serves as a marker of poor prognosis in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) ranks as one of the most common and lethal malignancies worldwide. A better understanding of the mechanism responsible for HCC metastasis will be helpful for the treatment of HCC patients. Thymidine phosphorylase (TP), a key enzyme that catalyzes the conversion of thymidine to thymine and deoxyribose-1-phosphate, was demonstrated to promote the invasion and metastasis of HCC in our study. Clinical retrospective analysis revealed that metastatic HCC tumor tissues have higher TP expression, and TP expression was significantly correlated with matrix metalloproteinase (MMP) 2 and 9 expression. Survival analysis revealed that TP expression was negatively correlated with the prognosis of HCC patients. Moreover, in vitro cell experiments confirmed that TP could promote the migration and invasion of HCC cells. In addition, MMP2 and MMP9 were activated by TP overexpression. Overall, this study suggests that TP promotes metastasis and may serve as a marker of poor prognosis in HCC. Thus, TP is a potential target for the treatment of HCC.

Astrocytic TYMP and VEGFA drive blood-brain barrier opening in inflammatory central nervous system lesions.

In inflammatory central nervous system conditions such as multiple sclerosis, breakdown of the blood-brain barrier is a key event in lesion pathogenesis, predisposing to oedema, excitotoxicity, and ingress of plasma proteins and inflammatory cells. Recently, we showed that reactive astrocytes drive blood-brain barrier opening, via production of vascular endothelial growth factor A (VEGFA). Here, we now identify thymidine phosphorylase (TYMP; previously known as endothelial cell growth factor 1, ECGF1) as a second key astrocyte-derived permeability factor, which interacts with VEGFA to induce blood-brain barrier disruption. The two are co-induced NFκB1-dependently in human astrocytes by the cytokine interleukin 1 beta (IL1B), and inactivation of Vegfa in vivo potentiates TYMP induction. In human central nervous system microvascular endothelial cells, VEGFA and the TYMP product 2-deoxy-d-ribose cooperatively repress tight junction proteins, driving permeability. Notably, this response represents part of a wider pattern of endothelial plasticity: 2-deoxy-d-ribose and VEGFA produce transcriptional programs encompassing angiogenic and permeability genes, and together regulate a third unique cohort. Functionally, each promotes proliferation and viability, and they cooperatively drive motility and angiogenesis. Importantly, introduction of either into mouse cortex promotes blood-brain barrier breakdown, and together they induce severe barrier disruption. In the multiple sclerosis model experimental autoimmune encephalitis, TYMP and VEGFA co-localize to reactive astrocytes, and correlate with blood-brain barrier permeability. Critically, blockade of either reduces neurologic deficit, blood-brain barrier disruption and pathology, and inhibiting both in combination enhances tissue preservation. Suggesting importance in human disease, TYMP and VEGFA both localize to reactive astrocytes in multiple sclerosis lesion samples. Collectively, these data identify TYMP as an astrocyte-derived permeability factor, and suggest TYMP and VEGFA together promote blood-brain barrier breakdown.

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-ß 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.

Platelet derived endothelial cell growth factor/thymidine phosphorylase enhanced human IgE production.

BACKGROUND: Angiogenesis is one pathogenesis of allergic airway disease. METHODS: A potent angiogenic factor is platelet-derived endothelial cell growth factor (PD-ECGF), also known as thymidine phosphorylase (TP) in the field of cancer-associated research. Vascular endothelial growth factor (VEGF) is another representative angiogenic factor. Both factors were added to the culture system of human peripheral blood mononuclear cells (PBMC) with IL-4 and anti-CD40 monoclonal antibody (mAb). Total IgE levels in the supernatants and signal transduction of stimulated PBMC were evaluated. RESULTS: Addition of PD-ECGF enhances in vitro IgE production by PBMC in the presence of IL-4 and anti-CD40 mAb, but VEGF does not enhance IgE production. Although PD-ECGF catalyzes the reversible phosphorolysis of thymidine to 2-deoxy-D-ribose-1-phosphate (2DDR), treatment of 2DDR has no effect on IgE production by human PBMC. Both IL-4 and anti-CD40 mAb induce PD-ECGF by human PBMC. Thymidine phosphorylase inhibitor (TPI), 5-chloro-6-[1- (2-iminopyrrolidinyl) methyl] uracil hydrochloride reduce IgE production via blocking of STAT6- phosphorylation. CONCLUSIONS: Taken together, these results suggest TP involvement in the enhancement of IgE production and suggest that TPI is a novel strategy against IgE-related allergic disease.

Platelet-derived endothelial cell growth factor mediates angiogenesis and antiapoptosis in rat aortic endothelial cells.

This study explores the angiogenic and antiapoptotic activities of platelet-derived endothelial cell growth factor (PDECGF) in rat aortic endothelial cells. The effects of PDECGF on rat aortic endothelial cell (RAEC) proliferation, migration, chemotaxis, and tubule formation were investigated in vitro at various concentrations viz., 1, 2, 4, 8, 16, and 32 ng x mL(-1) on endothelial cells. Endothelial cells were induced with hypoxic stress and the antiapoptotic effects of PDECGF were analysed by cell survival assay, fluorescence microscopy, cell viability assay, and flow cytometry. The results demonstrated the angiogenic potential of PDECGF on endothelial cells in a dose-dependent manner. PDECGF at 16 and 32 ng x mL(-1) increased cell proliferation (>80%), induced cell migration (>4 fold), stimulated chemotaxis (>2 fold), and increased tubule formation (>3 fold) compared with the control. Studies on hypoxic stress revealed the antiapoptotic nature of PDECGF on endothelial cells. PDECGF treatment enhanced cell survival by 14%, as well as cell viability by 13%, and decreased the percentage of apoptotic cells by 13% as demonstrated by fluorescence-activated cell sorter studies (FACS). In conclusion, this study demonstrated the angiogenic and antiapoptotic potentials of PDECGF on RAEC.

Comparison of 18F-FDG, 18F-FET and 18F-FLT for differentiation between tumor and inflammation in rats.

INTRODUCTION: The goal of this study was to compare the glucose analog, 2-[18F]fluoro-2-deoxy-d-glucose ([18F]-FDG), the amino acid analog, o-(2-[18F]fluoroethyl)-l-tyrosine ([18F]-FET) and nucleoside analog, 3'-[18F]fluoro-3'-deoxythymidine ([18F]-FLT) with regard to their feasibility for differentiating tumors from inflammation. METHODS: In Fisher rat models bearing both 9L tumor and inflammation, the biodistributions and positron emission tomography (PET) images of [18F]-FDG, [18F]-FET and [18F]-FLT at 60 min post injection were compared. Pretreatment with thymidine phosphorylase before injection of [18F]-FLT was performed. RESULTS: The tumor-to-blood (T/B) and tumor-to-muscle (T/M) ratios of [18F]-FDG were significantly higher than those of [18F]-FET and [18F]-FLT (P<.01); however, the accumulation of [18F]-FDG [1.23+/-0.52 percent injected dose per gram of tissue (%ID/g)] in inflammation was also elevated. T/B and T/M ratios of [18F]-FET (2.3+/-0.5 and 2.2+/-0.5) were higher than those of [18F]-FLT (1.6+/-0.6 and 1.6+/-0.5), and inflammation uptake of those tracers was very low (0.63+/-0.19 and 0.27+/-0.16 %ID/g, respectively). [18F]-FET and [18F]-FLT showed higher selectivity indices (tumor-to-inflammation ratio corrected background) than [18F]-FDG. In PET images, [18F]-FDG was found to be accumulated in both tumor and inflammation, but [18F]-FET and [18F]-FLT selectively localized in tumor. CONCLUSION: Our data confirm the result of previous studies that [18F]-FET and [18F]-FLT are superior to [18F]-FDG in differentiating tumor from inflammation.

Platelet-released growth factors enhance the secretion of hyaluronic acid and induce hepatocyte growth factor production by synovial fibroblasts from arthritic patients.

OBJECTIVES: Autologous platelet-secreted growth factors (GFs) may have therapeutic effects in osteoarthritis (OA) capsular joints via multiple mechanisms. Our aim was to examine the effect of a platelet-derived preparation rich in growth factors (PRGFs) in OA synovial cell biology. METHODS: Synovial cells were isolated from 10 osteoarthritic patients and cultured in serum-free media (basal conditions) and exposed to either a platelet-poor preparation or PRGF for 72 h. Cells activated with interleukin-1beta (IL-1beta) for 48 h were also exposed to PRGF. Changes in several events relevant to joint homeostasis including (i) hyaluronic acid (HA) secretion, (ii) the balance between metalloproteinase-1, -3 and -13 (MMP-1, MMP-3 and MMP-13) and tissue inhibitor-1 (TIMP-1) and (iii) the secretion of transforming growth factor-beta1(TGF-beta1), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF), were all assessed. RESULTS: PRGF significantly enhanced HA secretion compared with platelet-poor preparations, P < 0.05; at the same time release of TIMP-1, MMP-1, MMP-3 and MMP-13 were not affected. An increased HGF production was observed (P < 0.05) but VEGF and TGF-beta1 levels remained unchanged. PRGF significantly enhanced the secretion of HA induced by IL-1beta activation, P < 0.05, but it did not modify the IL-1beta-induced rise in MMP-1, MMP-3 and VEGF. In contrast, PRGF-induced HGF production was abolished by the presence of IL-1beta during PRGF treatment, P < 0.05. CONCLUSIONS: Intra-articular administration of PRGF might be beneficial in restoring HA concentration and switching angiogenesis to a more balanced status but does not halt the effects of IL-1beta on synovial cells.

The antiproliferative effect of sildenafil on pulmonary artery smooth muscle cells is mediated via upregulation of mitogen-activated protein kinase phosphatase-1 and degradation of extracellular signal-regulated kinase 1/2 phosphorylation.

BACKGROUND: Pulmonary hypertension is a group of diseases comprising vascular constriction and by obstructive changes of the pulmonary vasculature. Phosphodiesterase type 5 inhibitors, e.g., sildenafil, can alleviate vascular remodeling in the monocrotaline pulmonary hypertension model in rats, and inhibit the proliferation of pulmonary vascular smooth muscle cells in vitro. We examined the ability of sildenafil to inhibit platelet-derived growth factor (PDGF)-induced proliferation of porcine pulmonary artery smooth muscle cells. METHODS: Pulmonary artery smooth muscle cell proliferation and cell cycle analysis were assessed by MTT assay and fluorescence-activated cell sorting. Western blotting was used to examine protein expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) and phosphorylation level of extracellular signal-regulated kinase (ERK1/2). RESULTS: PDGF increased cell proliferation and the percentage of cells in S phase. These effects were inhibited by pretreatment with sildenafil in a dose-dependent manner. Sildenafil (96 microM) also caused a 67% decrease in PDGF-stimulated ERK1/2 phosphorylation. Sildenafil inhibition of ERK1/2 was accompanied by a rapid induction of MKP-1. Inhibition of the cGMP-dependent kinase I alpha (cGK I alpha) using Rp-8-BrcGMPS (25 microM) blocked sildenafil-induced MKP-1 expression. Either vanadate (12.5 microM), a phosphatase inhibitor, or Rp-8-BrcGMPS abolished the inhibitory effect of sildenafil on PDGF-stimulated phosphorylation of ERK1/2 and restored PDGF-induced cell proliferation. CONCLUSION: This study indicates that sildenafil upregulates MKP-1 expression and promotes degradation of phosphorylation of ERK1/2, which suppresses the proliferation of pulmonary artery smooth muscle cells.

Gliostatin/thymidine phosphorylase-regulated vascular endothelial growth-factor production in human fibroblast-like synoviocytes.

Gliostatin/thymidine phosphorylase (GLS/TP) is known to have angiogenic and arthritogenic activities. The purpose of this study was to elucidate whether GLS/TP is involved in the regulation of the angiogenic cytokine vascular endothelial growth factor (VEGF) in rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLSs) from patients with RA were cultured and stimulated with recombinant human GLS (rHuGLS) and interleukin (IL)-1beta. Immunohistochemistry showed that GLS/TP and VEGF were detectable in the synovial lining cells. In cultured FLSs, both VEGF mRNA and protein levels were markedly increased by rHuIL-1beta treatment. rHuGLS increased VEGF mRNA expression in a dose-dependent manner. We detected high concentrations of VEGF165 protein in culture supernatants from FLSs treated with rHuGLS (300 ng/ml), which were comparable to GLS levels found in synovial fluid of RA patients. These findings indicate that GLS/TP and VEGF have synergistic effects on angiogenesis in rheumatoid synovitis, and that GLS/TP has a role in regulating VEGF.

Platelet-derived endothelial cell growth factor mediates Rho-associated coiled-coil domain kinase messenger RNA expression and promotes cell motility.

BACKGROUND: Platelet-derived endothelial cell growth factor (PD-ECGF), whose expression is increased in several cancers, is an endothelial cell mitogen and has chemotactic activity in vitro and angiogenic activity in vivo. Tumors with high PD-ECGF expression tend to have frequent lymph node metastasis and are associated with poor outcome. METHODS: We screened genes transduced by PD-ECGF transfection to the colon cancer cell line DLD-1 by using a complementary DNA microarray. Cell motility was evaluated by in vitro migration assay. Actin fiber polymerization was visualized by immunofluorescent detection of phalloidin. RESULTS: Rho-associated coiled-coil domain kinase (ROCK1) was found to be significantly overexpressed in PD-ECGF transfectants compared with mock cells. PD-ECGF transfectants showed higher cell motility than mock cells. The parental cell, DLD-1, with recombinant PD-ECGF showed higher cell motility than that without recombinant PD-ECGF, in which motility was blocked by the neutralizing antibody of PD-ECGF or Y-27632, a specific inhibitor of ROCK1. Moreover, the actin fiber polymerization, which is a marker of activation of ROCK1, was higher in PD-ECGF transfectants than in mock cells. CONCLUSIONS: PD-ECGF expression may be associated with cancer cell migration via activation of ROCK1. This may explain one mechanism by which tumors with high expression of PD-ECGF show aggressive behavior.

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

1 Thymidine phosphorylase (TP) is elevated in the plasma of cancer patients, and has been implicated in pathophysiological angiogenesis. However, the downstream signals underlying this implication remain obscure. The purpose of the present study was to examine the effects of TP on the neovascularisation response in vitro and in vivo. 2 Both TP and its catalytic product, 2-deoxy-D-ribose-1-phosphate, and downstream 2-deoxy-D-ribose (2-DDR) promoted endothelial tubulogenesis in vitro, and the regeneration of a wounded monolayer of endothelial cells without exerting any mitogenic effect. In vivo, both TP and 2-DDR promoted the development of functional vasculature into an avascular sponge. A TP inhibitor, 6-amino-5-chlorouracil, was able to partially reverse the effects of TP, but had no effect on the 2-DDR-induced angiogenesis. 3 Enhanced monolayer regeneration was observed with TP-cDNA-transfected bladder carcinoma cells. The transfection of TP-cDNA, however, did not confer any proliferative advantage. The regeneration of TP overexpressing cells was associated with a time-dependent expression of the enzyme haeme-oxygenase (HO-1). 4 The present study demonstrates that both TP and its ribose-sugar metabolites induce angiogenesis by mediating a cohesive interplay between carcinoma and endothelial cells. The induction of HO-1 in TP-transfected cells suggests that it could be a possible downstream signal for the angiogenic effects of TP. Furthermore, reducing sugars have been shown to induce oxidative stress, and ribose could be a possible cause for the upregulation of HO-1, which has been implicated in the release of angiogenic factors. Therefore, we postulate that 2-DDR could be mediating the angiogenic effects of TP possibly through an oxidative stress mechanism and additionally getting integrated in the endothelial metabolic machinery.

Thymidine phosphorylase expressed in macrophages enhances antitumor effect of 5'-deoxy-5-fluorouridine on human colorectal carcinoma cells.

BACKGROUND: Thymidine phosphorylase (dThdPase) is a key enzyme in the activation of the pro-drugs of 5-fluorouracil (5-FU), 5-deoxy-5-fluorouridine (5'-DFUR) and capecitabine. In colorectal carcinoma (CRC), the major cells expressing dThdPase have been shown to be stromal cells, particularly macrophages. MATERIALS AND METHODS: The present study was designed to clarify whether dThdPase expressed in macrophage-like cell lines, THP-1 and U937, and monocyte-rich mono-nuclear cells (MoMNCs) from human peripheral blood can modulate the antitumor effect of 5'-DFUR on CRC cells. RESULTS: dThdPase protein was found in THP-1 and U937 by ELISA, while little or no dThdPase could be detected in the CRC cell lines tested. Incubation of 5'-DFUR with the macrophage-like cells significantly enhanced the antitumor effect of 5'-DFUR in a 5-DFUR sensitivity assay compared with untreated 5'-DFUR. MoMNCs also showed a similar effect. When the media containing 5'-DFUR was treated with either THP-1 or U937 cells, detectable levels of 5-FU could be measured in the treated media. CONCLUSION: These data suggest that macrophages convert 5'-DFUR to 5-FU and release the converted 5-FU, resulting in an enhancement of the antitumor effect of 5'-DFUR.

Thymidine phosphorylase and 2-deoxyribose stimulate human endothelial cell migration by specific activation of the integrins alpha 5 beta 1 and alpha V beta 3.

Thymidine phosphorylase is an angiogenic factor that is frequently overexpressed in solid tumors, in rheumatoid arthritis, and in response to inflammatory cytokines. Our previous studies showed that cells expressing thymidine phosphorylase stimulated endothelial cell migration in vitro. This was a consequence of the intracellular metabolism of thymidine by thymidine phosphorylase and subsequent extracellular release of 2-deoxyribose. The mechanisms by which 2-deoxyribose might mediate thymidine phosphorylase-induced cell migration in vitro, however, are obscure. Here we show that both thymidine phosphorylase and 2-deoxyribose stimulated the formation of focal adhesions and the tyrosine 397 phosphorylation of focal adhesion kinase in human umbilical vein endothelial cells. Although similar actions occurred upon treatment with the angiogenic factor vascular endothelial growth factor (VEGF), thymidine phosphorylase differed from VEGF in that its effect on endothelial cell migration was blocked by antibodies to either integrin alpha 5 beta 1 or alpha v beta 3, whereas VEGF-induced endothelial cell migration was only blocked by the alpha v beta 3 antibody. Further, thymidine phosphorylase and 2-deoxyribose, but not VEGF, increased the association of both focal adhesion kinase and the focal adhesion-associated protein vinculin with integrin alpha 5 beta 1 and, in intact cells, increased the co-localization of focal adhesion kinase with alpha 5 beta 1. Thymidine phosphorylase and 2-deoxyribose-induced focal adhesion kinase phosphorylation was blocked by the antibodies to alpha 5 beta 1 and alpha v beta 3, directly linking the migration and signaling components of thymidine phosphorylase and 2-deoxyribose action. Cell surface expression of alpha 5 beta 1 was also increased by thymidine phosphorylase and 2-deoxyribose. These experiments are the first to demonstrate a direct effect of thymidine phosphorylase and 2-deoxyribose on signaling pathways associated with endothelial cell migration.

Role of platelet-derived endothelial cell growth factor/thymidine phosphorylase in fluoropyrimidine sensitivity.

Platelet-derived endothelial cell growth factor (PD-ECGF)/thymidine phosphorylase (TP) catalyses the reversible phosphorolysis of thymidine to thymine and 2-deoxyribose-1-phosphate and is involved in the metabolism of fluoropyrimidines. It can also activate 5'-deoxyfluorouridine (5'DFUR) and possibly 5-fluorouracil (5FU) and Ftorafur (Ft), but inactivates trifluorothymidine (TFT). We studied the contribution of TP activity to the sensitivity for these fluoropyrimidines by modulating its activity and/or expression level in colon and lung cancer cells using a specific inhibitor of TP (TPI) or by overproduction of TP via stable transfection of human TP. Expression was analysed using competitive template-RT-PCR (CT-RT-PCR), Western blot and an activity assay. TP activity ranged from nondetectable to 70678 pmol h(-1) 10(-6) cells, in Colo320 and a TP overexpressing clone Colo320TP1, respectively. We found a good correlation between TP activity and mRNA expression (r=0.964, P&<0.01) in our cell panel. To determine the role of TP in the sensitivity to 5FU, 5'DFUR, Ft and TFT, cells were cultured with the various fluoropyrimidines with or without TPI and differences in IC(50)'s were established. TPI modified 5'DFUR, increasing the IC(50)'s 2.5- to 1396-fold in WiDR and Colo320TP1, respectively. 5-Fluorouracil could be modified by inhibiting TP but to a lesser extent than 5'DFUR: IC(50)'s increased 1.9- to 14.7-fold for WiDR and Colo320TP1, respectively. There was no effect on TFT or Ft. There appears to be a threshold level of TP activity to influence the 5'DFUR and 5FU sensitivity, which is higher for 5FU. Even high levels of TP overexpression only had a moderate effect on 5FU sensitivity.

combination of vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP) to improve angiogenic gene therapy.

To improve current angiogenic gene therapy with a vascular endothelial growth factor (VEGF)-encoding plasmid (Baumgartner et al. Circulation 1998; 97: 1114-23 [1]; Kusumanto et al. Fifth Annual Meeting of the American Society of Gene Therapy, Boston, 2002, Abstr. 621 [2]), we have generated a combination plasmid, encoding the VEGF gene and the thymidine phosphorylase (TP, also known as platelet-derived endothelial growth factor (PD-ECGF) or gliostatin (GLS)) gene: phVEGF165-TP.MB. Upon transfection in COS-7 cells both gene products were expressed and functional as shown by Western blots, ELISAs and bioassays. Culture supernatants of COS-7 cells transfected with this plasmid were able to induce endothelial proliferation. In an in vitro angiogenesis assay with recombinant proteins, TP was able to increase VEGF-induced tube formation. The phVEGF165-TP.MB plasmid is therefore a promising candidate for in vivo angiogenesis studies.

[Thymidine phosphorylase inhibits apoptosis induced by anticancer agents].

An angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-D-ribose, a degradation product of thymidine generated by TP enzymatic activity, partially prevented hypoxia-induced apoptosis. TP was expressed at higher levels in tumor tissuses compared to the adjacent non-neoplastic tissues in a variety of human carcinomas. High expression of TP is associated with an unfavorable prognosis. To investigate the effect of TP on cisplatin-induced apoptosis, human leukemia Jurkat cells were transfected wild-type or mutant (L148R) TP cDNA. TP inhibits a number of steps in the cisplatin-induced apoptotic pathway, activation of caspase 3, 9 and mitochondrial cytochrome c release. These findings suggest a mechanism by which TP confers the resistance to apoptosis by cisplatin. Moreover, mutant TP that has no enzymatic activity also suppressed cisplatin-induced apoptosis. These findings indicate that TP has cytoprotective functions against cytotoxic agents which are independent of its enzymatic activity.

Angiogenic effect of thymidine phosphorylase on macrophages in glioblastoma multiforme.

OBJECT: Thymidine phosphorylase (TP) and vascular endothelial growth factor (VEGF) are known angiogenic factors; however, there are few reports in which the relationship between these two factors is addressed. The authors compared expression patterns of TP and VEGF and investigated their role in the angiogenesis of glioblastoma multiforme (GBM). METHODS: Surgical specimens from 41 cases of GBM were immunohistochemically stained for TP, VEGF, CD68 (a macrophage marker), and CD31 (an endothelial cell marker). Both TP labeling indices and VEGF immunoreactivity displayed significant correlations with vascular density. Although VEGF was diffusely distributed in the tumor, TP was strongly expressed around blood vessels and in vascular proliferation. Double labeling for TP and CD68 in 10 cases indicated that cells that reacted strongly positive for TP were almost always macrophages, and only small numbers of CD68-negative cells weakly expressed TP. The TP messenger (m)RNA expression was investigated using reverse transcription-polymerase chain reaction in six GBMs. All six specimens expressed TP mRNA. In addition, TP mRNA was detected in two of three groups of cultured GBM cells derived from surgical specimens. Macrophages, the production of which was induced from two volunteers' peripheral blood monocytes by applying macrophage colony-stimulating factor, also expressed TP mRNA. The glioma cell lines U251MG and U87MG, which barely express TP mRNA under normal conditions, expressed TP mRNA in response to interferon-beta stimulation or while in an anoxic condition. CONCLUSIONS: Although it is feasible that GBM cells can express TP depending on their growing conditions, the majority of TP-expressing cells present in GBMs appear to be infiltrating macrophages. Coexistence of VEGF and TP may indicate a synergistic upregulation for angiogenesis because VEGF exerts a chemotactic activity on macrophages that express TP.

Inhibition of the NA(+)/H(+) exchanger reduces rat hepatic stellate cell activity and liver fibrosis: an in vitro and in vivo study.

BACKGROUND & AIMS: The Na(+)/H(+) exchanger is the main intracellular pH (pH(i)) regulator in hepatic stellate cells (HSCs) and plays a key role in regulating proliferation and gene expression. We evaluated the effect of specific inhibition of this exchanger on HSC proliferation and collagen synthesis in vivo and in vitro. METHODS: Rat HSCs were incubated in the presence of platelet-derived growth factor (PDGF), transforming growth factor (TGF)-beta1, iron ascorbate (FeAsc), and ferric nitrilotriacetate solution (FeNTA) with or without the Na(+)/H(+) exchanger inhibitor 5-N-ethyl-N-isopropyl-amiloride (EIPA). pH(i) and Na(+)/H(+) exchanger activity, cell proliferation, and type I collagen accumulation were measured by using the fluorescent dye 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein, by immunohistochemistry for bromodeoxyuridine, and by enzyme-linked immunosorbent assay, respectively. In vivo liver fibrosis was induced by dimethylnitrosamine administration and bile duct ligation (BDL) in rats treated or not treated with amiloride. RESULTS: PDGF, FeAsc, and FeNTA increased Na(+)/H(+) exchange activity and induced HSC proliferation. TGF-beta1 had no effect on the Na(+)/H(+) exchanger and was able, as for FeAsc and FeNTA, to induce type I collagen accumulation. EIPA inhibited all the effects determined by PDGF, FeAsc, and FeNTA and had no effect on TGF-beta1-induced collagen accumulation. In vivo, amiloride reduced HSC proliferation, activation, collagen deposition, and collagen synthesis. CONCLUSIONS: The Na(+)/H(+) exchanger can play a key role in the development of liver fibrosis and in HSC activation in vivo.