Thymidine Phosphorylase Overexpression Research Articles

1,3,4-Oxadiazole: An Emerging Scaffold to Inhibit the Thymidine Phosphorylase as an Anticancer Agent.

Thymidine phosphorylase (TP), also referred to as "platelet-derived endothelial cell growth factor" is crucial to the pyrimidine salvage pathway. TP reversibly transforms thymidine into thymine and 2-deoxy-D-ribose-1-phosphate (dRib-1-P), which further degraded to 2-Deoxy-D-ribose (2DDR), which has both angiogenic and chemotactic activity. In several types of human cancer such as breast and colorectal malignancies, TP is abundantly expressed in response to biological disturbances like hypoxia, acidosis, chemotherapy, and radiation therapy. TP overexpression is highly associated with angiogenic factors such as vascular endothelial growth factor (VEGF), interleukins (ILs), matrix metalloproteases (MMPs), etc., which accelerate tumorigenesis, invasion, metastasis, immune response evasion, and resistant to apoptosis. Hence, TP is recognized as a key target for the development of new anticancer drugs. Heterocycles are the primary structural element of most chemotherapeutics. Even 75% of nitrogen-containing heterocyclic compounds are contributing to the pharmaceutical world. To create the bioactive molecule, medicinal chemists are concentrating on nitrogen-containing heterocyclic compounds such as pyrrole, pyrrolidine, pyridine, imidazole, pyrimidines, pyrazole, indole, quinoline, oxadiazole, benzimidazole, etc. The Oxadiazole motif stands out among all of them due to its enormous significance in medicinal chemistry. The main thrust area of this review is to explore the synthesis, SAR, and the significant role of 1,3,4-oxadiazole derivatives as a TP inhibitor for their chemotherapeutic effects.

Thymidine phosphorylase promotes angiogenesis and tumour growth in intrahepatic cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver cancer, and thymidine phosphorylase (TP) is a regulator of angiogenesis. To investigate the biological activities of TP in ICC, we established human cholangiocarcinoma RBE cell lines overexpressing TP or silencing TP. Overexpression of TP enhanced viability, suppressed apoptosis and increased tube formation in human umbilical vein endothelial cells, while downregulation of TP reversed these effects. Moreover, an orthotopic xenograft mouse model of ICC was built to further explore TP's function in ICC in vivo. Histological analysis using H&E, TUNEL and Ki67 staining showed that TP promoted tumour growth and inhibited cell apoptosis. Immunostaining for CD31 revealed an elevation in microvessel density in the presence of TP. Besides, upregulation of TP increased the expression of vascular endothelial growth factor, basic fibroblast growth factor, interleukin-8 and tumour necrosis factor alpha. In contrast, TP knockdown inhibited tumour growth, suppressed microvessel formation and decreased the expression of angiogenesis-related proteins. Therefore, we suggest that TP promotes angiogenesis and tumour growth in ICC, which can be a potent therapeutic target for ICC treatment.

Thymidine phosphorylase and prostrate cancer cell proliferation inhibitory activities of synthetic 4-hydroxybenzohydrazides: In vitro, kinetic, and in silico studies.

Over-expression of thymidine phosphorylase (TP) plays a key role in many pathological complications, including angiogenesis which leads to cancer cells proliferation. Thus in search of new anticancer agents, a series of 4-hydroxybenzohydrazides (1–29) was synthesized, and evaluated for in vitro thymidine phosphorylase inhibitory activity. Twenty compounds 1–3, 6–14, 16, 19, 22–24, and 27–29 showed potent to weak TP inhibitory activities with IC50 values in the range of 6.8 to 229.5 μM, in comparison to the standards i.e. tipiracil (IC50 = 0.014 ± 0.002 μM) and 7-deazaxanthine (IC50 = 41.0 ± 1.63 μM). Kinetic studies on selected inhibitors 3, 9, 14, 22, 27, and 29 revealed uncompetitive and non-competitive modes of inhibition. Molecular docking studies of these inhibitors indicated that they were able to interact with the amino acid residues present in allosteric site of TP, including Asp391, Arg388, and Leu389. Antiproliferative (cytotoxic) activities of active compounds were also evaluated against mouse fibroblast (3T3) and prostate cancer (PC3) cell lines. Compounds 1, 2, 19, and 22–24 exhibited anti-proliferative activities against PC3 cells with IC50 values between 6.5 to 10.5 μM, while they were largely non-cytotoxic to 3T3 (mouse fibroblast) cells proliferation. Present study thus identifies a new class of dual inhibitors of TP and cancer cell proliferation, which deserves to be further investigated for anti-cancer drug development.

Thymidine Phosphorylase Expression and Microvascular Density Correlation Analysis in Canine Mammary Tumor: Possible Prognostic Factor in Breast Cancer.

Purpose: The thymidine phosphorylase (TP) is a key enzyme involved in the metabolism of pyrimidines. Inhibition or downregulation of this enzyme causes accumulation of metabolites with consequences in DNA replication. TP regulates angiogenesis and chemotactic activity of endothelial cells. Different studies showed the presence of TP upregulation in human cancer but the correlation between TP expression and the microvascular density (MVD) in canine mammary tumors is unknown. The aim of this study was to investigate a possible correlation between the MVD and TP expression in tumor cells of canine mammary tumors of different degree of severity (G1–G3) by immunohistochemical analysis.Methods: Sixty-eight samples of spontaneous mammary neoplasia of 5–12 cm in diameter were collected from purebred and mixed-breed dogs (mean aged = 9.5 ± 7), not subject to chemotherapy treatments in veterinary clinics. Histopathological analysis and immunostaining were performed.Results: Carcinoma simple samples have been classified as 72.06% of tubule-papillary, 20.59% cysto-papillary, and 7.35% tubular carcinomas. Immunostainings revealed a marked cytoplasmic expression of TP in 30.88% of samples, mild in 32.35%, weaker in 22.07%, and negative in 14.70%. The correlation analysis and two-way ANOVA showed a linear correlation between MVD and TP with a coefficient of correlation (r) > 0.5 (p < 0.05) in G2 and G3. No correlation between variables was found in G1.Conclusions: These findings suggest that cytoplasmic TP overexpression is correlated with microvascular density in canine mammary tumors, in severe grade, and it can be a potential prognostic factor in breast cancer.

Antimalarial Drug Pyrimethamine Plays a Dual Role in Antitumor Proliferation and Metastasis through Targeting DHFR and TP.

Pyrimethamine (Pyr), an antimalarial drug that targeting plasmodium dihydrofolate reductase (pDHFR), has been proved to have antitumor activity. However, its direct target on cancer cells remains unclear. Methotrexate (MTX) is a widely used anticancer drug that blocks human dihydrofolate reductase (hDHFR). In this work, we examined the anticancer effects of Pyr in vitro and in vivo Our results showed that hDHFR and pDHFR have similar secondary and three-dimensional structures and that Pyr can inhibit the activity of hDHFR in lung cancer cells. Although Pyr and MTX can inhibit the proliferation of lung cancer cells by targeting DHFR, only Pyr can inhibit the epithelial-mesenchymal transition (EMT), metastasis and invasion of lung cancer cells. These results indicated that hDHFR is not the only target of Pyr. We further found that thymidine phosphorylase (TP), an enzyme that is closely associated with the EMT of cancer cells, is also a target protein of Pyr. The data retrieved from the Cancer Genome Atlas (TCGA) database revealed that TP overexpression is associated with poor prognosis of patients with lung cancer. In conclusion, Pyr plays a dual role in antitumor proliferation and metastasis by targeting DHFR and TP. Pyr may have potential clinical applications for the treatment of lung cancer.

Non-Coding Micro RNAs and Hypoxia-Inducible Factors Are Selenium Targets for Development of a Mechanism-Based Combination Strategy in Clear-Cell Renal Cell Carcinoma-Bench-to-Bedside Therapy.

Durable response, inherent or acquired resistance, and dose-limiting toxicities continue to represent major barriers in the treatment of patients with advanced clear-cell renal cell carcinoma (ccRCC). The majority of ccRCC tumors are characterized by the loss of Von Hippel–Lindau tumor suppressor gene function, a stable expression of hypoxia-inducible factors 1α and 2α (HIFs), an altered expression of tumor-specific oncogenic microRNAs (miRNAs), a clear cytoplasm with dense lipid content, and overexpression of thymidine phosphorylase. The aim of this manuscript was to confirm that the downregulation of specific drug-resistant biomarkers deregulated in tumor cells by a defined dose and schedule of methylselenocysteine (MSC) or seleno-l-methionine (SLM) sensitizes tumor cells to mechanism-based drug combination. The inhibition of HIFs by selenium was necessary for optimal therapeutic benefit. Durable responses were achieved only when MSC was combined with sunitinib (a vascular endothelial growth factor receptor (VEGFR)-targeted biologic), topotecan (a topoisomerase 1 poison and HIF synthesis inhibitor), and S-1 (a 5-fluorouracil prodrug). The documented synergy was selenium dose- and schedule-dependent and associated with enhanced prolyl hydroxylase-dependent HIF degradation, stabilization of tumor vasculature, downregulation of 28 oncogenic miRNAs, as well as the upregulation of 12 tumor suppressor miRNAs. The preclinical results generated provided the rationale for the development of phase 1/2 clinical trials of SLM in sequential combination with axitinib in ccRCC patients refractory to standard therapies.

Demethoxycurcumin sensitizes the response of non-small cell lung cancer to cisplatin through downregulation of TP and ERCC1-related pathways

Excision repair cross-complementary 1 (ERCC1) overexpression in lung cancer cells is strongly correlated with its resistance to platinum-based chemotherapy. Overexpression of thymidine phosphorylase (TP) reverts platinum-induced cancer cell death. Curcumin has been reported to enhance antitumor properties through the suppression of TP and ERCC1 in non-small cell lung carcinoma cells (NSCLC). Nevertheless, whether two other curcuminoids, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) from Curcuma longa demonstrate antitumor activity like that of curcumin remain unknown. MTT assay was conducted to determine the cell cytotoxicity. Western blotting was used to determine the protein expressions. Docking is the virtual screening of a database of compounds and predicting the strongest binders based on various scoring functions. BIOVIA Discovery Studio 4.5 (D.S. 4.5) were used for docking. Firstly, when compared with curcumin and BDMC, DMC exhibited the most potent cytotoxic effect on NSCLC, most importantly, MRC-5, a lung fetal fibroblast, was insensitive to DMC (under 30µM). Secondly, DMC alone significantly inhibited on-target cisplatin (CDDP) resistance protein, ERCC1, via PI3K-Akt-snail pathways, and TP protein expression in A549 cells. Thirdly, DMC treatment markedly increased post-target CDDP resistance pathway including Bax and cytochrome c. DMC significantly decreased Bcl-2 protein expressions. Finally, MTT assay indicated that DMC significantly increased CDDP-induced cytotoxicity and was confirmed with an increased Bax/Bcl-2 ratio, indicating upregulation of caspase-3. We concluded that enhancement of the cytotoxicity to CDDP by coadminstration with DMC was mediated by down-regulation of the expression of TP and ERCC1, regulated by PI3K-Akt-Snail pathway inactivation.

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.

Thymidine phosphorylase and angiogenesis in early stage esophageal squamous cell carcinoma.

The relationship between thymidine phosphorylase (TP) and angiogenesis at the early stage of esophageal squamous cell carcinoma has been unclear. Using 14 samples of normal squamous epithelium, 11 samples of low-grade intraepithelial neoplasia, and 64 samples of superficial esophageal cancer, microvessel density (MVD) was estimated using immunostaining for CD34 and CD105. TP expression was also evaluated in both cancer cells and stromal monocytic cells (SMCs). We then investigated the correlation between MVD and TP expression in both cancer cells and SMCs. On the basis of the above parameters, MVD was significantly higher in cancerous lesions than in normal squamous epithelium. In terms of CD34 and CD105 expression, MVD showed a gradual increase from normal squamous epithelium, to low-grade intraepithelial neoplasia, and then to M1 and M2 cancer, and M3 or deeper cancer. M1 and M2 cancer showed overexpression of TP in both cancer cells and SMCs. There was no significant correlation between TP expression in cancer cells and MVD estimated from CD34 (rS=0.16, P=0.21) or CD105 (rS=0.05, P=0.68) expression. Significant correlations were found between TP expression in SMCs and CD34-related (rS=0.46, P<0.001) and CD105-related (rS=0.34, P<0.01) MVD. In M3 or deeper cancers, there were no significant correlations between TP expression in cancer cells or SMCs and venous invasion, lymphatic invasion, and lymph node metastasis. TP expression is activated in both cancer cells and stromal monocytic cells at the very early stage of ESCC progression. TP expression in SMCs, rather than in cancer cells, is significantly correlated with angiogenesis.

Abstract CT028: First-in-human phase I study of the nucleotide analogue NUC-3373 designed to overcome fluoropyrimidine drug resistance mechanisms

Abstract Background: NUC-3373 is the first nucleotide analogue to bypass the key cancer resistance mechanisms associated with 5-fluorouracil (5-FU) and 5-fluorodeoxyuridine (FUDR) that significantly impede their clinical activity. In EC50 assays, NUC-3373 demonstrated up to 330x greater activity than 5-FU across multiple cancer cell lines and retained its activity in conditions mimicking drug resistance: thymidine kinase inhibition, thymidine phosphorylase over-expression and membrane transporter inhibition. In addition, whilst dihydropyrimidine dehydrogenase (DPD) significantly degraded 5-FU in cell lysates (p = 0.039), levels of NUC-3373 remained unaffected. Importantly, NUC-3373 generated 363x higher intracellular levels of the anti-cancer agent 5-fluorodeoxyuridine monophosphate, the active metabolite of 5-FU and FUDR. In colorectal cancer xenografts, NUC-3373 administered at 30 mg/kg 5-FU equimolar dose, demonstrated significantly greater tumour growth inhibition (47%) than 5-FU (25%). Finally, in formal toxicology studies NUC-3373 was significantly better tolerated than 5-FU, showing low conversion into the metabolite dihydrofluorouracil, dhFU (AUC plasma ratio dhFU:NUC-3373 = 0.03). NUC-3373 warrants clinical evaluation. Study Design: A two-part, Phase I open label, dose escalation and expansion study will be conducted to assess safety, pharmacokinetics and clinical activity of single agent NUC-3373 in participants with advanced solid tumours. A standard 3+3 dose escalation scheme will be used to identify the recommended Phase 2 dose (RP2D) of NUC-3373 comparing, in Part 1, a weekly schedule of administrationon days 1, 8, 15 and 22 of a 28-day cycle; and in Part 2 a fortnightly schedule of administration on days 1 and 15 of a 28-day cycle. Objectives: The primary objective is to establish the RP2D of NUC-3373 administered weekly and fortnightly. The secondary objectives are to assess the safety, pharmacokinetics, pharmacodynamics and anti-tumour activity of the agent. Tertiary objectives are to identify biomarkers that may help select those patients more likely to benefit from NUC-3373 than 5-FU. Major eligibility criteria: Histologically confirmed diagnosis of solid tumour, which is not amenable to, or refractory to standard chemotherapy, or for which no standard chemotherapy exists; measurable/evaluable disease; ECOG score 0-2; adequate bone marrow, liver and renal functions. Patients with a history of allergic reactions attributed to previous 5-FU or capecitabine treatment are excluded. Conclusions: NUC-3373 overcomes key cancer resistance mechanisms associated with 5-FU and a Phase I clinical study has been initiated. Citation Format: Sarah P. Blagden, Magdalena Slusarczyk, Michaela Serpi, Christopher McGuigan, Essam A. Ghazaly. First-in-human phase I study of the nucleotide analogue NUC-3373 designed to overcome fluoropyrimidine drug resistance mechanisms. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT028.

Long-Term Restoration of Thymidine Phosphorylase Function and Nucleoside Homeostasis Using Hematopoietic Gene Therapy in a Murine Model of Mitochondrial Neurogastrointestinal Encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a metabolic disorder caused by mutations in TYMP, encoding thymidine phosphorylase (TP). In MNGIE patients, TP dysfunction produces systemic thymidine and deoxyuridine accumulation, which ultimately impairs mitochondrial DNA replication and results in mitochondrial dysfunction. To date, only allogeneic hematopoietic stem cell transplantation has demonstrated long-term clinical efficacy, but high morbidity and mortality associated with this procedure necessitate the search for safer alternatives. In a previous study, we demonstrated that hematopoietic stem cell gene therapy using a lentiviral vector containing the coding sequence of TYMP restored the biochemical homeostasis in an animal model of MNGIE. In the present follow-up study, we show that ectopic expression of TP in the hematopoietic system restores normal nucleoside levels in plasma, as well as in tissues affected in MNGIE such as small intestine, skeletal muscle, brain, and liver. Mitochondrial dNTP pool imbalances observed in liver of the animal model were also corrected by the treatment. The biochemical effects were maintained at least 20 months even with low levels of chimerism. No alterations in the blood cell counts or other toxic effects were observed in association with the lentiviral transduction or TP overexpression. These results further support the notion that gene therapy is a feasible treatment option for MNGIE.

Thymidine phosphorylase activates NFκB and stimulates the expression of angiogenic and metastatic factors in human cancer cells

Thymidine phosphorylase (TP) promotes angiogenesis and metastasis, and confers resistance to anticancer agents in some cancer cell types. We previously reported that TP stimulates the expression of interleukin (IL)-8 in human KB cancer cells by an unknown mechanism. A mutation in the nuclear factor (NF)κB binding site of the IL-8 promoter suppressed promoter activity in KB/TP cells that overexpress TP. Specifically inhibiting NFκB by using BY11-7082 also suppressed TP-induced IL-8 promoter activity and IL-8 expression. Moreover, TP overexpression led to the activation of NFκB and an upregulation in the expression of its target genes, and increased phosphorylated IKKα/β protein levels, while promoting IκBα degradation as well as p65 phosphorylation and nuclear localization. The activation of NFκB in KB/TP cells was suppressed by the antioxidants N-acetylcysteine and EUK-8. In addition, in gastric cancer tissue samples, the expression of the NFκB-regulated genes, including IL-8, IL-6, and fibronectin-1 was positively correlated with TP expression. These findings indicate that reactive oxygen species mediated NFκB activation by TP increases the expression of genes that promote angiogenesis and metastasis in gastric 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.

Heterogeneous Nuclear Ribonucleoprotein H1/H2-dependent Unsplicing of Thymidine Phosphorylase Results in Anticancer Drug Resistance

Thymidine phosphorylase (TP) catalyzes the conversion of thymidine to thymine and 2-deoxyribose-1-phosphate. The latter plays an important role in induction of angiogenesis. As such, many human malignancies exhibit TP overexpression that correlates with increased microvessel density, formation of aggressive tumors, and dismal prognosis. Because TP is frequently overexpressed in cancer, pro-drugs were developed that utilize TP activity for their bioactivation to cytotoxic drugs. In this respect, TP is indispensable for the pharmacologic activity of the chemotherapeutic drug capecitabine, as it converts its intermediary metabolite 5'-deoxyfluorouridine to 5-fluorouracil. Thus, loss of TP function confers resistance to the prodrug capecitabine, currently used for the treatment of metastatic colorectal cancer and breast cancer. However, drug resistance phenomena may frequently emerge that compromise the pharmacologic activity of capecitabine. Deciphering the molecular mechanisms underlying resistance to TP-activated prodrugs is an important goal toward the overcoming of such drug resistance phenomena. Here, we discovered that lack of TP protein in drug-resistant tumor cells is due to unsplicing of its pre-mRNA. Advanced bioinformatics identified the family of heterogeneous nuclear ribonucleoproteins (hnRNP) H/F as candidate splicing factors potentially responsible for impaired TP splicing. Indeed, whereas parental cells lacked nuclear localization of hnRNPs H1/H2 and F, drug-resistant cells harbored marked levels of these splicing factors. Nuclear RNA immunoprecipitation experiments established a strong binding of hnRNP H1/H2 to TP pre-mRNA, hence implicating them in TP splicing. Moreover, introduction of hnRNP H2 into drug-sensitive parental cells recapitulated aberrant TP splicing and 5'-deoxyfluorouridine resistance. Thus, this is the first study identifying altered function of hnRNP H1/H2 in tumor cells as a novel determinant of aberrant TP splicing thereby resulting in acquired chemoresistance to TP-activated fluoropyrimidine anticancer drugs.

Docetaxel and capecitabine in metastatic androgen independent prostate cancer (AIPC): Phase II trial to detect clinical efficacy of a synergistic combination

4703 Background: Docetaxel plus prednisone is the current therapeutic choice in the management of metastatic AIPC. Capecitabine is an oral prodrug of 5-fluorouracil which is selectively converted intratumorally to 5-flourouracil by thymidine phosphorylase (TP). Differential overexpression of TP is noted in tumors as compared to normal tissue. Docetaxel pretreatment when followed by capecitabine therapy has demonstrated synergy in preclinical studies with xenograft models. The purpose of this phase II trial was to evaluate the efficacy and safety of this combination in metastatic AIPC. Methods: Eligible patients had metastatic AIPC with no prior chemotherapy for metastatic disease. Other requirements included castrate levels of testosterone adequate renal, liver and marrow function and evidence of disease progression either by PSA, new metastatic sites, or progression of measurable disease sites. Docetaxel was administered intravenously on days 1, 8 and 15 of a 28 day cycle at a dose of 36 mg/m2. Capecitabine was administered at a dose of 1250 mg/m2/day in two divided doses orally from days 5 to 18 of each cycle. Results: 11 of 15 patients planned in the first stage have been enrolled to date. Baseline characteristics were, median age 73 years (range 38–78 years).;baseline PSA 131ng/ml (Range 8.9–3716ng/ml); three patients had progressive measurable disease, 5 patients had progression of bony metastases and 3 patients had PSA progression alone. 7 of the 8 evaluable patients demonstrated >50% decline in PSA and both of the measurable disease patients evaluated had a partial remission. 41 cycles of therapy (median 5 cycles) have been administered. Three patients required dose reduction. No grade 4/5 toxicities were noted. Only 1 patient had grade 3 neutropenia. No therapy related hospitalizations or deaths were observed. Conclusions: Preliminary data suggest that the combination of capecitabine and docetaxel is well tolerated and demonstrates promising activity in metastatic AIPC. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Aventis, Roche Aventis

Thymidine Phosphorylase Gene Transfer Inhibits Vascular Smooth Muscle Cell Proliferation by Upregulating Heme Oxygenase-1 and p27 KIP1

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. 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. 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.

Coexpression of cyclooxygenase-2 and thymidine phosphorylase as a prognostic indicator in patients with FIGO stage IIB squamous cell carcinoma of uterine cervix treated with radiotherapy and concurrent chemotherapy

To evaluate the prognostic significance of thymidine phosphorylase (TP) and coexpression of cyclooxygenase-2 (COX-2)/TP, and to investigate the relationship between COX-2 and TP expression in squamous cell carcinoma of the uterine cervix. Cancer specimens from 75 patients with International Federation of Gynecology and Obstetrics Stage IIB squamous cell carcinoma of the uterine cervix who had undergone radiotherapy and concurrent chemotherapy were immunohistochemically stained with COX-2 and TP antibodies and scored. The prognostic significance of their expression status, and the relationship between COX-2 and TP was investigated. TP predominantly stained cytoplasm and the cell membrane of the tumor cells mainly in a diffuse and intense manner. TP was negative (<10% distribution) in 17%, 1+ (10-50%) in 25%, and 2+ (>50%) in 57% of patients. TP overexpression was related to a marginal prognostic significance of a poor 5-year overall survival (p = 0.082, log-rank test) and a high locoregional recurrence rate (p < 0.1, chi-square test). COX-2 and TP coexpression was observed in 24% of patients and was significantly related to poor 5-year disease-free and overall survival rates (p = 0.0083 and p = 0.025, respectively), a high pelvic lymph node involvement rate, a poor response to treatment, and a greater incidence of locoregional recurrence (p < 0.05). By multivariate analyses, only COX-2, TP, and coexpression of COX-2/TP were significant independent prognostic indicators of patient survival. All tumors showed 1+ or 2+ TP expression when COX-2 was positive, and no tumor expressed COX-2 when TP was negative (p = 0.03). In contrast, 77% of tumors expressed 1+ or 2+ TP without the synchronous expression of COX-2. Thymidine phosphorylase expression or COX-2/TP coexpression may be used as a molecular prognostic marker for squamous cell carcinoma of the uterine cervix. TP appears to be an important downstream molecule of COX-2 during angiogenesis and may be a new target for the treatment of uterine cervical cancer.

The role of thymidine phosphorylase, an angiogenic enzyme, in tumor progression

Thymidine phosphorylase (TP), an enzyme involved in pyrimidine metabolism, is identical with an angiogenic factor, platelet-derived endothelial cell growth factor (PD-ECGF). TP is overexpressed in various tumors and plays an important role in angiogenesis, tumor growth, invasion and metastasis. The enzymatic activity of TP is required for the angiogenic effect of TP. A novel, specific TP inhibitor, TPI, inhibits angiogenesis induced by overexpression of TP in KB/TP cells (human KB epidermoid carcinoma cells transfected with TP cDNA), as well as the growth and metastasis of KB/TP cells in vivo. 2-deoxy-D-ribose, the degradation product of thymidine generated by TP activity, has both angiogenic and chemotactic activity. Both 2-deoxy-D-ribose and TP inhibit a hypoxia-induced apoptotic pathway. These findings suggest that 2-deoxy-D-ribose is a downstream mediator of TP function. 2-deoxy-L-ribose, a stereoisomer of 2-deoxy-D-ribose, inhibits the promotion of angiogenesis, tumor growth and metastasis by TP. Although the mechanism of the action of 2-deoxy-D-ribose is still unknown, 2-deoxy-L-ribose may inhibit the physiological activities of 2-deoxy-D-ribose, and consequently those of TP. Inhibition of TP activity and function appears to be a promising approach for the chemotherapy of various tumors.

Thymidine Phosphorylase Over-Expression in Oral Squamous Carcinoma Tissue as a Potential Target of Capecitabine

Advanced oral squamous carcinoma (OSC) is typically treated with 5- Fluorouracil (5-FU) based regimens. Capecitabine (CAP) is a thymidine phosphorylase (TP) activated oral fluoropyrimidine, rationally designed to generate 5-FU preferentially within tumours. The high activity of CAP in intestinal and breast cancer suggests that CAP may have a role in the therapy of OSC. This tumour selectively is achieved through exploitation of the significantly higher activity of TP in tumour compared with healthy tissue. In the present study, the epithelial and macrophages TP expression were significantly higher in OSC than in non-dysplastic oral leukoplakia (NDOLP) (p=0.004, p=0.005; respectively). Because OSC is sensitive to 5-FU, and TP expression is significantly higher in OSC than in NDOLP, TP-activated CAP could be a promising therapy worthy of clinical investigation.

Role of thymidine phosphorylase on invasiveness and metastasis in lung adenocarcinoma.

Thymidine phosphorylase (TP) is expressed at higher levels in a variety of human cancers than in adjacent normal tissue. It is reported that the higher expression is associated with an increase of intratumoral microvessel density and a poor prognosis. We investigated the role of TP in human non small cell lung cancers (NSCLCs). The concentrations of TP in the tumors and the adjacent normal tissue from surgically resected specimens of 54 cases of NSCLCs were measured by using an enzyme-linked immunosorbent assay. Tumor specimens were also examined immunohistochemically. TP concentrations in the tumors were 169 +/- 18 units/mg protein (mean +/- SD), whereas those in normal tissue were 43 +/- 4 units/mg protein (mean +/- SD), consistent with TP staining patterns. There was no correlation between TP expression and microvessel density. Among clinicopathologic factors examined, the concentrations of TP but not TP immunoreactivity correlated with tumor differentiation in lung adenocarcinoma. Although a specific TP inhibitor (TPI) and overexpression of TP did not affect the growth of A549 lung adenocarcinoma cells, Matrigel invasion assay showed that A549 transfected with TP had higher invasive potential than mock transfectant, and such enhanced invasive activity was markedly diminished by treatment with TPI. Furthermore, administration of TPI suppressed lung metastasis of TP-overexpressing A549 cells in nude mice. These results demonstrate that TP may play an important role in tumor differentiation, invasiveness and metastasis in lung adenocarcinoma, and suggest that TP could be a novel target for treatment of TP-overexpressing lung adenocarcinoma.