Targeting platelet-derived endothelial cell growth factor/thymidine phosphorylase for cancer therapy

Multi-cohort validation: A comprehensive exploration of prognostic marker in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common form of RCC. It is characterized by resistance to traditional radiotherapy and chemotherapy, as well as an unfavorable clinical prognosis. Although TYMP is implicated in the advancement of tumor progression, the role of TYMP in ccRCC is still not understood. Heightened TYMP expression was identified in ccRCC through database mining and confirmed in RCC cell lines. Indeed, TYMP knockdown impacted RCC cell proliferation, migration, and invasion in vitro. TYMP showed a positive correlation with clinicopathological parameters (histological grade, pathological stage). Moreover, patients with high TYMP expression were indicative of poor prognosis in TCGA-ccRCC and external cohorts. The results of single-cell analysis showed that the distribution of TYMP was predominantly observed in monocytes and macrophages. Furthermore, there is a significant association between TYMP and immune status. Methylation analysis further elucidated the relationship between TYMP expression and multiple methylation sites. Drug sensitivity analysis unveiled potential pharmaceutical options. Additionally, mutation analyses identified an association between TYMP and the ccRCC driver genes like BAP1 and ROS1. In summary, TYMP may serve as a reliable prognostic indicator for ccRCC.

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.

Role and efficacy of capecitabine in the anthracycline-free regimen in breast cancer patients: a systematic review and meta-analysis

PURPOSE

Capecitabine has extensive utilization in the treatment of diverse solid tumors, and its efficacy has been substantiated. Its oral administration and minimal toxicity in clinical practice render it advantageous. Nevertheless, uncertainty remains regarding whether capecitabine can substitute anthracycline drugs in chemotherapy regimens to achieve a lower risk of anthracycline-induced degradation. Consequently, we conducted a meta-analysis of randomized controlled trials (RCTs) to assess the potential of capecitabine as a replacement for anthracycline drugs in chemotherapy regimens for breast cancer.

METHODS

We systematically searched PubMed, Embase, Web of Science, and the Cochrane Controlled Trials Register (CENTRAL) to retrieve eligible studies published before July 18, 2023. Two independent reviewers extracted relevant data from the included studies using a pre-established data extraction form. The primary endpoints of interest encompassed overall survival (OS) and progression-free survival (PFS) for postoperative adjuvant therapy, as well as pathological complete response (PCR) following neoadjuvant therapy. Adverse events were considered as secondary outcomes. The statistical analysis was performed using Revman 5.4.1.

RESULTS

A total of six studies involving 2348 breast cancer patients were deemed eligible according to the selection criteria. The pooled meta-analysis revealed that there were no statistically significant differences observed in the primary outcomes of overall survival (OS) (HR 1.06, 95% CI 0.88-1.28) and progression-free survival (PFS) (HR 1.10, 95% CI 0.90-1.34) across the four postoperative adjuvant chemotherapy trials, as well as in the two neoadjuvant chemotherapy trials with respect to the primary outcome of pathological complete response (PCR) (OR 1.65, 95% CI 0.93-2.95) when comparing regimens containing anthracycline drugs to those without. In terms of adverse events, the probability of experiencing diarrhea (OR 3.94, P = 0.004) and hand-foot syndrome (OR 10.89, P = 0.004) was significantly higher in the capecitabine group, attributable to the drug characteristics. Conversely, the likelihood of developing neutropenia (OR 0.50, P = 0.03) was higher in the anthracycline group.

CONCLUSIONS

According to the current evidence, there was no statistically significant difference in the primary outcomes when capecitabine was substituted for anthracycline drugs. Thus, capecitabine can be regarded as a feasible alternative in the subset of patients who necessitate the exclusion of anthracyclines.

Distinctive metabolic remodeling in TYMP deficiency beyond mitochondrial dysfunction

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the TYMP gene, which encodes thymidine phosphorylase (TP). As a cytosolic metabolic enzyme, TP defects affect biological processes that are thought to not be limited to the abnormal replication of mitochondrial DNA. This study aimed to elucidate the characteristic metabolic alterations and associated homeostatic regulation caused by TYMP deficiency. The pathogenicity of novel TYMP variants was evaluated in terms of clinical features, genetic analysis, and structural instability. We analyzed plasma samples from three patients with MNGIE; three patients with m.3243A > G mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS); and four healthy controls (HC) using both targeted and untargeted metabolomics techniques. Transcriptomics analysis and bioenergetic studies were performed on skin fibroblasts from participants in these three groups. A TYMP overexpression experiment was conducted to rescue the observed changes. Compared with controls, specific alterations in nucleosides, bile acids, and steroid metabolites were identified in the plasma of MNGIE patients. Comparable mitochondrial dysfunction was present in fibroblasts from patients with TYMP deficiency and in those from patients with the m.3243A > G mutation. Distinctively decreased sterol regulatory element binding protein (SREBP) regulated cholesterol metabolism and fatty acid (FA) biosynthesis as well as reduced FA degradation were revealed in fibroblasts with TYMP deficiency. The restoration of thymidine phosphorylase activity rescued the observed changes in MNGIE fibroblasts. Our findings indicated that more widespread metabolic disturbance may be caused by TYMP deficiency in addition to mitochondrial dysfunction, which expands our knowledge of the biochemical outcome of TYMP deficiency. KEY MESSAGES: Distinct metabolic profiles in patients with TYMP deficiency compared to those with m.3243A > G mutation. TYMP deficiency leads to a global disruption of nucleoside metabolism. Cholesterol and fatty acid metabolism are inhibited in individuals with MNGIE. TYMP is functionally related to SREBP-regulated pathways. Potential metabolite biomarkers that could be valuable clinical tools to improve the diagnosis of MNGIE.

Identifying TYMP as an Immune Prognostic Marker in Clear Cell Renal Cell Carcinoma

BACKGROUND

In clear cell renal cell carcinoma (ccRCC), only some patients can benefit from immunotherapy therapy, and it is urgent to find immune-related molecular markers and targets.

METHODS

Thymidine phosphorylase (TYMP) expression level and predictive value in pan-cancers were analyzed using TIMER, GEPIA2, and The Human Protein Atlas. We obtained ccRCC tissues to verify the differential expression of TYMP and confirmed the biological function in vitro. Subsequently, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) are used to explore the potential mechanism of TYMP. Finally, TIMER was used to analyze the infiltration levels and prognostic value of different immune cells.

RESULTS

TYMP is upregulated in various cancers, including ccRCC, and there is a certain degree of causality between high expression and poor prognosis in ccRCC. It was confirmed that TYMP knockdown could suppress cell aggressiveness, and cause cell death. Differential analysis showed that 55 differential genes were upregulated in the high-expression groups of TYMP. KEGG and GSEA analyses suggested that TYMP was linked to immune cell invasion, fatty acid metabolism, and P53 signaling pathway. Further investigation revealed that the expression level of TYMP linked positively to T-cell follicular helper and Tregs, but negatively with mast cell activation. Finally, a Nomogram was established on the base of expression level of TYMP and the clinical characteristics of ccRCC patients to predict prognosis.

CONCLUSIONS

Patient survival is poor and immune cell infiltration is abnormal when TYMP is highly expressed in ccRCC, suggesting that ccRCC patients could benefit from using TYMP as a molecular diagnostic and therapeutic target.

Role of Cytokines and Chemokines in Angiogenesis in a Tumor Context

Simple Summary

Tumor growth in solid cancers requires adequate nutrient and oxygen supply, provided by blood vessels created by angiogenesis. Numerous studies have demonstrated that this mechanism plays a crucial role in cancer development and appears to be a well-defined hallmark of cancer. This process is carefully regulated, notably by cytokines with pro-angiogenic or anti-angiogenic features. In this review, we will discuss the role of cytokines in the modulation of angiogenesis. In addition, we will summarize the therapeutic approaches based on cytokine modulation and their clinical approval.

Abstract

During carcinogenesis, tumors set various mechanisms to help support their development. Angiogenesis is a crucial process for cancer development as it drives the creation of blood vessels within the tumor. These newly formed blood vessels insure the supply of oxygen and nutrients to the tumor, helping its growth. The main factors that regulate angiogenesis are the five members of the vascular endothelial growth factor (VEGF) family. Angiogenesis is a hallmark of cancer and has been the target of new therapies this past few years. However, angiogenesis is a complex phenomenon with many redundancy pathways that ensure its maintenance. In this review, we will first describe the consecutive steps forming angiogenesis, as well as its classical regulators. We will then discuss how the cytokines and chemokines present in the tumor microenvironment can induce or block angiogenesis. Finally, we will focus on the therapeutic arsenal targeting angiogenesis in cancer and the challenges they have to overcome.

Targeting Thymidine Phosphorylase With Tipiracil Hydrochloride Attenuates Thrombosis Without Increasing Risk of Bleeding in Mice

OBJECTIVE

Current antiplatelet medications increase the risk of bleeding, which leads to a clear clinical need in developing novel mechanism-based antiplatelet drugs. TYMP (Thymidine phosphorylase), a cytoplasm protein that is highly expressed in platelets, facilitates multiple agonist-induced platelet activation, and enhances thrombosis. Tipiracil hydrochloride (TPI), a selective TYMP inhibitor, has been approved by the Food and Drug Administration for clinical use. We tested the hypothesis that TPI is a safe antithrombotic medication. Approach and Results: By coexpression of TYMP and Lyn, GST (glutathione S-transferase) tagged Lyn-SH3 domain or Lyn-SH2 domain, we showed the direct evidence that TYMP binds to Lyn through both SH3 and SH2 domains, and TPI diminished the binding. TYMP deficiency significantly inhibits thrombosis in vivo in both sexes. Pretreatment of platelets with TPI rapidly inhibited collagen- and ADP-induced platelet aggregation. Under either normal or hyperlipidemic conditions, treating wild-type mice with TPI via intraperitoneal injection, intravenous injection, or gavage feeding dramatically inhibited thrombosis without inducing significant bleeding. Even at high doses, TPI has a lower bleeding side effect compared with aspirin and clopidogrel. Intravenous delivery of TPI alone or combined with tissue plasminogen activator dramatically inhibited thrombosis. Dual administration of a very low dose of aspirin and TPI, which had no antithrombotic effects when used alone, significantly inhibited thrombosis without disturbing hemostasis.

CONCLUSIONS

This study demonstrated that inhibition of TYMP, a cytoplasmic protein, attenuated multiple signaling pathways that mediate platelet activation, aggregation, and thrombosis. TPI can be used as a novel antithrombotic medication without the increase in risk of bleeding.

Bevacizumab-enhanced antitumor effect of 5-fluorouracil via upregulation of thymidine phosphorylase through vascular endothelial growth factor A/vascular endothelial growth factor receptor 2-specificity protein 1 pathway

Bevacizumab (Bv) can be used synergistically with fluoropyrimidine-based chemotherapy to treat colorectal cancer. Whether and how it affects the delivery of fluoropyrimidine drugs is unknown. The present study aimed to explore the effect of Bv on the delivery of 5-fluorouracil (5-FU) to tumors and the underlying mechanism from metabolic perspective. Bv enhanced the anti-tumor effects of 5-FU in LoVo colon cancer xenograft mice and increased the 5-FU concentration in tumors without affecting hepatic 5-FU metabolism. Interestingly, Bv remarkably upregulated thymidine phosphorylase (TP) in tumors, which mediated the metabolic activation of 5-FU. Although TP is reported to promote angiogenesis and resistance, the combination of Bv and 5-FU resulted in anti-angiogenesis and vessel normalization in tumors, indicating that the elevated TP mainly contributed to the enhanced response to 5-FU. Bv also induced TP upregulation in LoVo cancer cells. Treatment with vascular endothelial growth factor receptor 2 (VEGFR2) antagonist apatinib and VEGFR2 silencing further confirmed TP upregulation. Bv and apatinib both enhanced the cytotoxicity of 5-FU in LoVo cells, but there was no synergism with adriamycin and paclitaxel. We further demonstrated that the effect of Bv was dependent on VEGFR2 blockade and specificity protein 1 activation via MDM2 inhibition. In summary, Bv enhanced the accumulation of 5-FU in tumors and the cytotoxicity of 5-FU via TP upregulation. We provide data to better understand how Bv synergizes with 5-FU from metabolic perspective, and it may give clues to the superiority of Bv in combination with fluoropyrimidine drugs compared to other chemotherapeutic drugs in colon cancer.

Design, synthesis, in-vitro thymidine phosphorylase inhibition, in-vivo antiangiogenic and in-silico studies of C-6 substituted dihydropyrimidines

Thymidine phosphorylase (TP) is an angiogenic enzyme. It plays an important role in angiogenesis, tumour growth, invasion and metastasis. In current research work, we study the effect of structural modification of dihydropyrimidine-2-ones (DHPM-2-ones) on TP inhibition. A series of eighteen new derivatives of 3,4-dihydropyrimidone-2-one were designed and synthesized through the structural modification at C-6 position. All these new derivatives were then assessed for in-vitro inhibition of thymidine phosphorylase (TP) from E. coli. Oxadiazole derivatives 4a-e exhibited excellent TP-inhibition at low micromolar concentration levels better than standard drug 7-deazaxanthine (7-DX). Among all these compounds, 4b was found to be the most potent with IC₅₀ = 1.09 ± 0.004 μM. Anti-angiogenesis potential of representative compounds were also studied in a chorioallantoic membrane (CAM) assay. Here again, compound 4b was found to be the potent anti-angiogenesis compound in a CAM assay. Docking studies were also performed with Molecular Operating Environment (MOE) to further analyse the mode of inhibition of these compounds. Binding mode analysis of the most active inhibitors showed that these are well accommodated into the binding site of enzyme though stable hydrogen bonding and hydrophobic interactions.

3'-Deoxy-3'-[18F]Fluorothymidine Uptake Is Related to Thymidine Phosphorylase Expression in Various Experimental Tumor Models

PURPOSE

We recently reported that high thymidine phosphorylase (TP) expression is accompanied by low tumor thymidine concentration and high 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT) uptake in four untreated lung cancer xenografts. Here, we investigated whether this relationship also holds true for a broader range of tumor models.

PROCEDURES

Lysates from n = 15 different tumor models originating from n = 6 institutions were tested for TP and thymidylate synthase (TS) expression using western blots. Results were correlated to [18F]FLT accumulation in the tumors as determined by positron emission tomography (PET) measurements in the different institutions and to previously published thymidine concentrations.

RESULTS

Expression of TP correlated positively with [18F]FLT SUVmax (ρ = 0.549, P < 0.05). Furthermore, tumors with high TP levels possessed lower levels of thymidine (ρ = - 0.939, P < 0.001).

CONCLUSIONS

In a broad range of tumors, [18F]FLT uptake as measured by PET is substantially influenced by TP expression and tumor thymidine concentrations. These data strengthen the role of TP as factor confounding [18F]FLT uptake.

Thymidine phosphorylase in cancer aggressiveness and chemoresistance

Thymidine phosphorylase (TP) is a rate-limiting enzyme in thymidine catabolism. TP has several important roles in biological and pharmacological mechanisms; importantly TP acts as an angiogenic factor and one of metabolic enzymes of fluoro-pyrimidine anticancer agents and modifies inflammation. Improving our understanding of the characteristics and functions of TP has led to the development of novel TP-based anticancer therapies. We recently reported that TP-dependent thymidine catabolism contributes to tumour survival in low nutrient conditions and the pathway from thymidine to the glycolysis cascade is affected in the context of physiological and metabolic conditions. In this review, we describe recent advancement in our understanding of TP, with a focus on cancer cell biology and the pharmacology of pyrimidine analogue anticancer agents. This review provides comprehensive understanding of the molecular mechanism of TP function in cancer.

Thymidine phosphorylase: A potential new target for treating cardiovascular disease

We recently found that thymidine phosphorylase (TYMP), also known as platelet-derived endothelial cell growth factor, plays an important role in platelet activation in vitro and thrombosis in vivo by participating in multiple signaling pathways. Platelets are a major source of TYMP. Since platelet-mediated clot formation is a key event in several fatal diseases, such as myocardial infarction, stroke and pulmonary embolism, understanding TYMP in depth may lead to uncovering novel mechanisms in the development of cardiovascular diseases. Targeting TYMP may become a novel therapeutic for cardiovascular disorders. In this review article, we summarize the discovery of TYMP and the potential molecular mechanisms of TYMP involved in the development of various diseases, especially cardiovascular diseases. We also offer insights regarding future studies exploring the role of TYMP in the development of cardiovascular disease as well as in therapy.

Valproic acid potentiates the anticancer activity of capecitabine in vitro and in vivo in breast cancer models via induction of thymidine phosphorylase expression

The prognosis of patients with metastatic breast cancer remains poor, and thus novel therapeutic approaches are needed. Capecitabine, which is commonly used for metastatic breast cancer in different settings, is an inactive prodrug that takes advantage of elevated levels of thymidine phosphorylase (TP), a key enzyme that is required for its conversion to 5-fluororacil, in tumors. We demonstrated that histone deacetylase inhibitors (HDACi), including low anticonvulsant dosage of VPA, induced the dose- and time-dependent up-regulation of TP transcript and protein expression in breast cancer cells, but not in the non-tumorigenic breast MCF-10A cell line. Through the use of siRNA or isoform-specific HDACi, we demonstrated that HDAC3 is the main isoform whose inhibition is involved in the modulation of TP. The combined treatment with capecitabine and HDACi, including valproic acid (VPA), resulted in synergistic/additive antiproliferative and pro-apoptotic effects in breast cancer cells but not in TP-knockout cells, both in vitro and in vivo, highlighting the crucial role of TP in the synergism observed. Overall, this study suggests that the combination of HDACi (e.g., VPA) and capecitabine is an innovative antitumor strategy that warrants further clinical evaluation for the treatment of metastatic breast cancer.

A phase II study of capecitabine plus cisplatin in metastatic triple-negative breast cancer patients pretreated with anthracyclines and taxanes

BACKGROUND

Cisplatin is an effective agent for triple-negative breast cancer (TNBC) and synergistic activity between cisplatin and capecitabine has been demonstrated by in vitro and in vivo studies. This study was designed as a prospective clinical trial to evaluate the efficacy and safety of capecitabine plus cisplatin (XP) regimen in metastatic TNBC patients pretreated with anthracyclines and taxanes.

PATIENTS AND METHODS

Thirty-three patients with metastatic TNBC who had anthracyclines and taxanes as prior therapy were treated with capecitabine 2000 mg/m(2) orally on day 1 through 14 plus cisplatin 75 mg/m(2) intravenously on day 1 of a 21-day cycle, followed by capecitabine maintenance medications after a maximum of 6 cycles. The primary end point was objective response rate (ORR) and the secondary end points included progression-free survival (PFS), overall survival (OS) and toxicity profiles.

RESULTS

A total of 162 cycles was given. ORR was 63.6%. Median PFS was 8.2 (95%CI: 4.8-11.6) months in the entire population and 10.8 (95%CI: 6.5-15.1) months in responding patients. Median OS was 17.8 (95%CI: 14.4-21.2) months in all enrolled patients and 25.8 (95%CI: 14.6-37.0) months in responding patients. Most adverse events were mild and manageable, with neutropenia and nausea/vomiting as the most common toxicities. Grade 3/4 toxicities included leukopenia (10, 30.3%), neutropenia (10, 30.3%), anemia (2, 6.1%), thrombocytopenia (1, 3.0%), nausea/vomiting (3, 9.1%), hand-foot syndrome (HFS; 1, 3.0%), and sensory neuropathy (1, 3.0%).

CONCLUSIONS

Capecitabine plus cisplatin demonstrated an excellent activity and an acceptable safety profile in metastatic TNBC patients pretreated with anthracyclines and taxanes.

Thymidine Phosphorylase in Cancer; Enemy or Friend?

Thymidine phosphorylase (TP) is a nucleoside metabolism enzyme that plays an important role in the pyrimidine pathway.TP catalyzes the conversion of thymidine to thymine and 2-deoxy-α-D-ribose-1-phosphate (dRib-1-P). Although this reaction is reversible, the main metabolic function of TP is catabolic. TP is identical to the angiogenic factor platelet-derived endothelial-cell growth factor (PD-ECGF). TP is overexpressed in several human cancers in response to cellular stressful conditions like hypoxia, acidosis, chemotherapy and radiotherapy. TP has been shown to promote tumor angiogenesis, invasion, metastasis, evasion of the immune-response and resistance to apoptosis. Some of the biological effects of TP are dependent on its enzymatic activity, while others are mediated through cytokines like interleukin 10 (IL-10), basic fibroblast growth factor (bFGF) and tumour necrosis factor α (TNFα). Interestingly, TP also plays a role in cancer treatment through its role in the conversion of the oral fluoropyrimidine capecitabine into its active form 5-FU. TP is a predictive marker for fluoropyrimidine response. Given its various biological functions in cancer progression, TP is a promising target in cancer treatment. Further translational research is required in this area.

Prognosis Relevance of Serum Cytokines in Pancreatic Cancer

The overall survival of patients with pancreatic ductal adenocarcinoma is extremely low. Although gemcitabine is the standard used chemotherapy for this disease, clinical outcomes do not reflect significant improvements, not even when combined with adjuvant treatments. There is an urgent need for prognosis markers to be found. The aim of this study was to analyze the potential value of serum cytokines to find a profile that can predict the clinical outcome in patients with pancreatic cancer and to establish a practical prognosis index that significantly predicts patients' outcomes. We have conducted an extensive analysis of serum prognosis biomarkers using an antibody array comprising 507 human cytokines. Overall survival was estimated using the Kaplan-Meier method. Univariate and multivariate Cox's proportional hazard models were used to analyze prognosis factors. To determine the extent that survival could be predicted based on this index, we used the leave-one-out cross-validation model. The multivariate model showed a better performance and it could represent a novel panel of serum cytokines that correlates to poor prognosis in pancreatic cancer. B7-1/CD80, EG-VEGF/PK1, IL-29, NRG1-beta1/HRG1-beta1, and PD-ECGF expressions portend a poor prognosis for patients with pancreatic cancer and these cytokines could represent novel therapeutic targets for this disease.

Anticancer activity of a thymidine quinoxaline conjugate is modulated by cytosolic thymidine pathways

BACKGROUND

High levels of thymidine kinase 1 (TK1) and thymidine phosphorylase (TYMP) are key molecular targets by thymidine therapeutics in cancer treatment. The dual roles of TYMP as a tumor growth factor and a key activation enzyme of anticancer metabolites resulted in a mixed outcome in cancer patients. In this study, we investigated the roles of TK1 and TYMP on a thymidine quinoxaline conjugate to evaluate an alternative to circumvent the contradictive role of TYMP.

METHODS

TK1 and TYMP levels in multiple liver cell lines were assessed along with the cytotoxicity of the thymidine conjugate. Cellular accumulation of the thymidine conjugate was determined with organelle-specific dyes. The impacts of TK1 and TYMP were evaluated with siRNA/shRNA suppression and pseudoviral overexpression. Immunohistochemical analysis was performed on both normal and tumor tissues. In vivo study was carried out with a subcutaneous liver tumor model.

RESULTS

We found that the thymidine conjugate had varied activities in liver cancer cells with different levels of TK1 and TYMP. The conjugate mainly accumulated at endothelial reticulum and was consistent with cytosolic pathways. TK1 was responsible for the cytotoxicity yet high levels of TYMP counteracted such activities. Levels of TYMP and TK1 in the liver tumor tissues were significantly higher than those of normal liver tissues. Induced TK1 overexpression decreased the selectivity of dT-QX due to the concurring cytotoxicity in normal cells. In contrast, shRNA suppression of TYMP significantly enhanced the selective of the conjugate in vitro and reduced the tumor growth in vivo.

CONCLUSIONS

TK1 was responsible for anticancer activity of dT-QX while levels of TYMP counteracted such an activity. The counteraction by TYMP could be overcome with RNA silencing to significantly enhance the dT-QX selectivity in cancer cells.

Variability of Proliferation and Diffusion in Different Lung Cancer Models as Measured by 3'-Deoxy-3'-¹⁸F-Fluorothymidine PET and Diffusion-Weighted MR Imaging

Molecular imaging allows the noninvasive assessment of cancer progression and response to therapy. The aim of this study was to investigate molecular and cellular determinants of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) PET and diffusion-weighted (DW) MR imaging in lung carcinoma xenografts.

METHODS

Four lung cancer cell lines (A549, HTB56, EBC1, and H1975) were subcutaneously implanted in nude mice, and growth was followed by caliper measurements. Glucose uptake and tumor proliferation were determined by (18)F-FDG and (18)F-FLT PET, respectively. T2-weighted MR imaging was performed, and the apparent diffusion coefficient (ADC) was determined by DW MR imaging as an indicator of cell death. Imaging findings were correlated to histology with markers for tumor proliferation (Ki67, 5-bromo-2'-deoxyuridine [BrdU]) and cell death (caspase-3, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling). The expression of human equilibrative nucleoside transporter 1 (hENT1), thymidine kinase 1 (TK1), thymidylate synthase, and thymidine phosphorylase (TP) were analyzed by Western blot and immunohistochemistry. Thymidine levels were determined by liquid chromatography-mass spectrometry.

RESULTS

Xenografts varied with respect to in vivo growth rates. MR imaging and PET revealed intratumoral heterogeneities, which were confirmed by histology. (18)F-FLT uptake differed significantly between tumor lines, with A549 and H1975 demonstrating the highest radiotracer accumulation (A549, 8.5 ± 3.2; HTB56, 4.4 ± 0.7; EBC1, 4.4 ± 1.2; and H1975, 12.1 ± 3.5 maximal percentage injected dose per milliliter). In contrast, differences in (18)F-FDG uptake were only marginal. No clear relationship between (18)F-FLT accumulation and immunohistochemical markers for tumor proliferation (Ki67, BrdU) as well as hENT1, TK1, or TS expression was detected. However, TP was highly expressed in A549 and H1975 xenografts, which was accompanied by low tumor thymidine concentrations, suggesting that tumor thymidine levels influence (18)F-FLT uptake in the tumor models investigated. MR imaging revealed higher ADC values within proliferative regions of H1975 and A549 tumors than in HTB56 and EBC1. These ADC values were negatively correlated with cell density but not directly related to cell death.

CONCLUSION

A direct relationship of (18)F-FLT with proliferation or ADC with cell death might be complicated by the interplay of multiple processes at the cellular and physiologic levels in untreated tumors. This issue must be considered when using these imaging modalities in preclinical or clinical settings.

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.

Chemokine receptor CXCR4: role in gastrointestinal cancer

Chemokines (CK)s, small proinflammatory chemoattractant cytokines that bind to specific G-protein coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The CXCL12 [stromal cell-derived factor-1 (SDF-1)] binds primarily to CXC receptor 4 (CXCR4; CD184). The binding of CXCL12 to CXCR4 induces intracellular signaling through several divergent pathways initiating signals related to chemotaxis, cell survival and/or proliferation, increase in intracellular calcium, and gene transcription. CXCR4 is expressed on multiple cell types including lymphocytes, hematopoietic stem cells, endothelial and epithelial cells, and cancer cells. One of the most intriguing and perhaps important roles that CKs and the CK receptors have is in regulating metastasis. Here, CK receptors may potentially facilitate tumor dissemination at each of the key steps of metastasis, including adherence of tumor cells to endothelium, extravasation from blood vessels, metastatic colonization, angiogenesis, proliferation, and protection from the host response via activation of key survival pathways such as ERK/MAPK, PI-3K/Akt/mTOR, or Jak/STAT, etc. In addition, it is increasingly recognized that CKs play an important role in facilitating communication between cancer cells and non-neoplatic cells in the tumor microenvironment (TME), including endothelial cells and fibroblasts, promoting the infiltration, activation of neutrophils, and tumor-associated macrophages within the TME. In this review, we mainly focus on the roles of chemokines CXCL12 and its cognate receptors CXCR4 as they pertain to cancer progression. In particular, we summarizes our current understanding regarding the contribution of CXCR4 and SDF-1 to gastrointestinal tumor behavior and its role in local progression, dissemination, and immune evasion of tumor cells. Also, describes recent therapeutic approaches that target these receptors or their ligands.

Research development of the relationship between thymidine phosphorylase expression and colorectal carcinoma

Thymidine phosphorylase (TP) is a key enzyme that contributes to the composition and decomposition of pyrimidine nucleotides. TP seems homologous to platelet-derived endothelial cell growth factor, and its effects on inducing vascularization and anti-apoptosis are closely related to growth and metastasis of colorectal carcinoma. In addition, TP is a key enzyme that catalyzes the transformation from 5-fluorouracil (FU) prodrugs of 5′-deoxy-5-fluorouridine (5′-DFUR) to 5-FU. The activity of TP is closely related to the sensitivity of colorectal carcinoma cells to fluorouracil drugs and targeted therapy. Given the important functions of TP in growth, metastasis, tumor treatment, and prognosis, determining its expression mechanism is significant. This article summarizes the research development of TP expression in colorectal carcinoma, tumor neovascularization, cytotoxicity activation of 5′-DFUR, and colorectal carcinoma therapy.

Vinorelbine and capecitabine in anthracycline- and/or taxane-pretreated metastatic breast cancer: sequential or combinational?

PURPOSE

The difference between combinational and pre-planned sequential therapies using regimens that include non-anthracycline and taxane in the first-line setting remains unclear. The purpose of this study is to explore the interaction between vinorelbine (N) and capecitabine (X) in breast cancer cells and to compare the simultaneous or sequential administration of the two drugs in patients with metastatic breast cancer (MBC) as first-line treatment.

METHODS

First, we explored the effects of vinorelbine on thymidine phosphorylase (TP) and thymidylate synthase (TS) expression in breast cancer cells. Next, we designed a prospective randomized phase II trial of MBC patients comparing the combinational and pre-planned sequential administration of vinorelbine and capecitabine in the first-line metastatic setting. The primary end point was progression-free survival (PFS). The correlation between clinical characteristics and class III β-tubulin expression and patient survival was also explored.

RESULTS

Vinorelbine upregulates TP and downregulates TS in breast cancer cells, thereby further sensitizing tumor cells to capecitabine, which indicated the proper order for sequential therapy should be N → X. Sixty patients were eligible for the phase II trial. No significant difference was observed between the combinational arm and the sequential arm in terms of progression-free survival (PFS), overall response rate (ORR), and overall survival (OS). Only in the subgroup of patients with liver metastases were median PFS and OS significantly prolonged in the combinational arm (8.5 vs. 6.4 months, P = 0.041 and 23.8 vs. 13.9 months, P = 0.028, respectively). No association between class III β-tubulin expression and patient outcome was identified. Grade 3/4 adverse events were more common in the combinational arm.

CONCLUSIONS

Both the NX regimen and pre-planned sequential N → X regimen are acceptable as first-line treatments with comparable efficacies for MBC patients previously treated with anthracyclines and/or taxanes. Sequential monotherapies are recommended as the preferred approach to first-line chemotherapy for most MBC patients in the absence of an imminent visceral crisis and the need for rapid symptom and/or disease control.

Evaluations of biomarkers associated with sensitivity to 5-fluorouracil and taxanes for recurrent/advanced breast cancer patients treated with capecitabine-based first-line chemotherapy

The aim of the present study was to investigate the gene expression of biomarkers associated with the sensitivity to fluoropyrimidine and taxanes in recurrent/advanced breast cancer patients treated with first-line capecitabine chemotherapy. We evaluated the clinicopathological/prognostic significance of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), class III β-tubulin (βIII-tubulin), and stathmin-1 or oncoprotein-18 (STMN1). Formalin-fixed, paraffin-embedded tumor specimens from 42 patients were used for analysis of TS, DPD, TP, βIII-tubulin, and STMN1 expression with a real-time reverse transcription-PCR technique. Patients were classified into the high-expression and low-expression groups according to the median value of the expression level of each biomarker. There was a significantly longer time to progression (TTP) in the high-TP group (P=0.018). The multivariate analysis revealed that the TP expression (hazard ratio for the low-TP group vs. the high-TP group, 2.873; 95% confidence interval, 1.143-7.223; P=0.025) is independent of prognostic factors for TTP. In the subgroup of patients treated with capecitabine plus taxanes as first-line chemotherapy, TTP was significantly longer in the low-βIII-tubulin group (P=0.047). The gene expression of TS, DPD, and STMN1 failed to have any significant impact on the outcome. These results provide further evidence that the TP expression may be a prognostic factor in breast cancer patients treated with capecitabine-based first-line chemotherapy, and βIII-tubulin can be used to predict the outcome of capecitabine in combination with taxanes as first-line chemotherapy. Therefore, these potential biomarkers should be further evaluated.

ADAMTS5 functions as an anti-angiogenic and anti-tumorigenic protein independent of its proteoglycanase activity

ADAMTS5 is a member of the A Disintegrin-like And Metalloproteinase with ThromboSpondin motifs (ADAMTS) family of secreted metalloproteinases with multiple proteoglycan substrates. Although well characterized for its role in cartilage degradation and arthritis, how it influences cancer remains unclear. We have previously shown that the first thrombospondin type 1 repeat (TSR1, the central TSR) but not TSR2 (the C-terminal TSR) of ADAMTS5 is anti-angiogenic in vitro. Coupled with previous reports that ADAMTS5 expression is altered in several human cancers, we hypothesized that this proteoglycanase may play an important role in cancer and angiogenesis. Here, we demonstrated that overexpression of full-length ADAMTS5 suppressed B16 melanoma growth in mice. The reduced tumor growth is correlated with diminished tumor angiogenesis, together with reduced tumor cell proliferation and increased tumor cell apoptosis. Catalytically active ADAMTS5 proteolytic fragment also suppressed angiogenesis in vitro. The catalytic activity of ADAMTS5 is dispensable for its anti-tumorigenic function, as the full-length active site mutant E411A presented similar tumor suppression activity. Domain mapping and mechanistic studies revealed that ADAMTS5 inhibits B16 tumorigenesis through its TSR1 by suppressing tumor angiogenesis, likely by down-regulating pro-angiogenic factors such as vascular endothelial growth factor (VEGF), placenta growth factor (PlGF), and platelet-derived endothelial growth factor (PD-ECGF) in the tumor milieu. This is the first report that ADAMTS5 is an anti-angiogenic and anti-tumorigenic protein independent of its proteoglycanase activity.

Tumor 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) uptake by PET correlates with thymidine kinase 1 expression: static and kinetic analysis of (18)F-FLT PET studies in lung tumors

We report the first, to our knowledge, findings describing the relationships between both static and dynamic analysis parameters of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) PET and the expression of the proliferation marker Ki-67, and the protein expression and enzymatic activity of thymidine kinase-1 (TK1) in surgically resected lung lesions.

METHODS

Static and dynamic analyses (4 rate constants and 2 compartments) of (18)F-FLT PET images were performed in a cohort of 25 prospectively accrued, clinically suspected lung cancer patients before surgical resection (1 lesion was found to be benign after surgery). The maximal and overall averaged expression of Ki-67 and TK1 were determined by semiquantitative analysis of immunohistochemical staining. TK1 enzymatic activity was determined by in vitro assay of extracts prepared from flash-frozen samples of the same tumors.

RESULTS

Static (18)F-FLT uptake (partial-volume-corrected maximum-pixel standardized uptake value from 60- to 90-min summed dynamic data) was significantly correlated with the overall (ρ = 0.57, P = 0.006) and maximal (ρ = 0.69, P < 0.001) immunohistochemical expressions of Ki-67 and TK1 (overall expression: ρ = 0.65, P = 0.001; maximal expression: ρ = 0.68, P < 0.001) but not with TK1 enzymatic activity (ρ = 0.34, P = 0.146). TK1 activity was significantly correlated with TK1 protein expression only when immunohistochemistry was scored for maximal expression (ρ = 0.52, P = 0.029). Dynamic analysis of (18)F-FLT PET revealed correlations between the flux constant (K(FLT)) and both overall (ρ = 0.53, P = 0.014) and maximal (ρ = 0.50, P = 0.020) TK1 protein expression. K(FLT) was also associated with both overall (ρ = 0.59, P = 0.005) and maximal (ρ = 0.63, P = 0.002) Ki-67 expression. We observed no significant correlations between TK1 enzyme activity and K(FLT). In addition, no significant relationships were found between TK1 expression, TK1 activity, or Ki-67 expression and any of the compartmental rate constants.

CONCLUSION

The absence of observable correlations of the imaging parameters with TK1 activity suggests that (18)F-FLT uptake and retention within cells may be complicated by a variety of still undetermined factors in addition to TK1 enzymatic activity.

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.

Thymidylate synthase and thymidine phosphorylase as predictive markers of capecitabine monotherapy in patients with anthracycline- and taxane-pretreated metastatic breast cancer

PURPOSE

The primary purpose of this study was to evaluate the role of thymidylate synthase (TS) and thymidine phosphorylase (TP) as biomarkers to predict clinical outcomes of capecitabine monotherapy in patients with anthracycline- and taxane-pretreated metastatic breast cancer (MBC).

METHODS

Of the patients who were previously treated with anthracycline and taxane regimens, 90 patients who had available tissue block for immunohistochemistry with measurable lesions were included. All patients received capecitabine (2,500 mg/m(2)/day) for 14 days every 3 weeks.

RESULTS

High TS expression was more common among patients with triple-negative (TN) subtype than among patients with other subtypes (33% for hormone receptor+, 8% for HER2+, and 58% for TN, P = 0.023). The median PFS was significantly lower in patients with high TS (6.6 vs. 3.0 months; P = 0.017) and low TP expressions (6.0 vs. 3.3 months; P = 0.013). A high TS and a low TP expressions were identified as unfavorable independent risk factors for PFS to capecitabine monotherapy in multivariate analysis (hazard ratio [HR], 1.7, P = 0.037 for high TS score; HR, 1.8, P = 0.014 for low TP score).

CONCLUSIONS

Our data suggest that high TS and low TP scores correlate with a shorter PFS for capecitabine monotherapy in patients with anthracycline- and taxane-pretreated MBC.

Modulation of Rad51, ERCC1, and thymidine phosphorylase by emodin result in synergistic cytotoxic effect in combination with capecitabine

Thymidine phosphorylase (TP) is the rate-limiting enzyme for the activation of capecitabine (pro-drug of fluorouracil), and as a useful predictor of tumor response to capecitabine-based chemotherapy. Overexpression of Rad51 and ERCC1 induce resistance to chemotherapeutic agents. Emodin, one of the main bioactive anthraquinone derivatives in the roots and rhizomes of numerous plants, possesses potent antitumor effects. Accordingly, we aimed to explore the molecular mechanism of emodin enhances the capecitabine-induced cytotoxicity through controlling Rad51, ERCC1, and TP expression in human non-small cell lung cancer (NSCLC). The results show that capecitabine increases the phosphorylation of MKK1/2-ERK1/2 and protein levels of Rad51 and ERCC1 through enhancing the protein stability. Depletion of endogenous Rad51 or ERCC1 expression by specific small interfering RNA transfection significantly increases capecitabine-induced cell death and growth inhibition. Emodin enhances the capecitabine-induced cytotoxic effects through ERK1/2 inactivation and decreasing the Rad51 and ERCC1 protein levels induced by capecitabine. Enhancement of ERK1/2 signaling by constitutively active MKK1/2 (MKK1/2-CA) results in increasing Rad51 and ERCC1 protein levels and cell viability in NSCLC cell lines treated with emodin and capecitabine. Interestingly, emodin enhances TP mRNA and protein expression in capecitabine treated NSCLC cell lines, and depletion of the TP expression decreases the cytotoxic effects induced by capecitabine and emodin. We conclude that enhancing the cytotoxicity to capecitabine by emodin is mediated by down-regulation the expression of Rad51 and ERCC1 and up-regulation TP expression.

The role of blood platelets in tumor angiogenesis

Coagulation abnormalities occur frequently in cancer patients. It is becoming evident that blood platelets have an important function in this process. However, understanding of the underlying mechanisms is still very modest. In this review, we discuss the role of platelets in tumor angiogenesis and growth and suggest their potential significance in malignancies. Platelets contain various pro-and antiangiogenic molecules, which seem to be endocytosed and sequestered in different populations of α-granules. Furthermore, tumor endothelial cells are phenotypically and functionally different from endothelial cells in healthy tissue, stimulating local platelet adhesion and subsequent activation. As a consequence, platelets are able to secrete their angiogenic and angiostatic content, most likely in a regulated manner. The overall effect of these platelet-endothelium interactions appears to be proangiogenic, stimulating tumor angiogenesis. We favor the view that local adhesion and activation of blood platelets and dysregulation of coagulation represent underestimated pathways in the progression of cancer.

Vorinostat synergises with capecitabine through upregulation of thymidine phosphorylase

Background:

Potentiation of anticancer activity of capecitabine is required to improve its therapeutic index. In colorectal cancer (CRC) cells, we evaluated whether the histone deacetylase-inhibitor vorinostat may induce synergistic antitumour effects in combination with capecitabine by modulating the expression of thymidine phosphorylase (TP), a key enzyme in the conversion of capecitabine to 5-florouracil (5-FU), and thymidylate synthase (TS), the target of 5-FU.

Methods:

Expression of TP and TS was measured by real-time PCR, western blotting and immunohistochemistry. Knockdown of TP was performed by specific small interfering RNA. Antitumour activity of vorinostat was assessed in vitro in combination with the capecitabine active metabolite deoxy-5-fluorouridine (5′-DFUR) according to the Chou and Talay method and by evaluating apoptosis as well as in xenografts-bearing nude mice in combination with capecitabine.

Results:

Vorinostat induced both in vitro and in vivo upregulation of TP as well as downregulation of TS in cancer cells, but not in ex vivo treated peripheral blood lymphocytes. Combined treatment with vorinostat and 5′-DFUR resulted in a synergistic antiproliferative effect and increased apoptotic cell death in vitro. This latter effect was impaired in cells where TP was knocked. In vivo, vorinostat plus capecitabine potently inhibited tumour growth, increased apoptosis and prolonged survival compared with control or single-agent treatments.

Conclusions:

Overall, this study suggests that the combination of vorinostat and capecitabine is an innovative antitumour strategy and warrants further clinical evaluation for the treatment of CRC.

Angiopoietin-2 regulates gene expression in TIE2-expressing monocytes and augments their inherent proangiogenic functions

TIE2-expressing monocytes/macrophages (TEM) are a highly proangiogenic subset of myeloid cells in tumors. Here, we show that circulating human TEMs are already preprogrammed in the circulation to be more angiogenic and express higher levels of such proangiogenic genes as matrix metalloproteinase-9 (MMP-9), VEGFA, COX-2, and WNT5A than TIE2(-) monocytes. Additionally, angiopoietin-2 (ANG-2) markedly enhanced the proangiogenic activity of TEMs and increased their expression of two proangiogenic enzymes: thymidine phosphorylase (TP) and cathepsin B (CTSB). Three "alternatively activated" (or M2-like) macrophage markers were also upregulated by ANG-2 in TEMs: interleukin-10, mannose receptor (MRC1), and CCL17. To investigate the effects of ANG-2 on the phenotype and function of TEMs in tumors, we used a double-transgenic (DT) mouse model in which ANG-2 was specifically overexpressed by endothelial cells. Syngeneic tumors grown in these ANG-2 DT mice were more vascularized and contained greater numbers of TEMs than those in wild-type (WT) mice. In both tumor types, expression of MMP-9 and MRC1 was mainly restricted to tumor TEMs rather than TIE2(-) macrophages. Furthermore, tumor TEMs expressed higher levels of MRC1, TP, and CTSB in ANG-2 DT tumors than WT tumors. Taken together, our data show that although circulating TEMs are innately proangiogenic, exposure to tumor-derived ANG-2 stimulates these cells to exhibit a broader, tumor-promoting phenotype. As such, the ANG-2-TEM axis may represent a new target for antiangiogenic cancer therapies.

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.

Rationally designed pharmacogenomic treatment using concurrent capecitabine and radiotherapy for glioblastoma; gene expression profiles associated with outcome

PURPOSE

Previous preclinical studies suggested that concurrent capecitabine and radiation could be an effective new treatment modality for glioblastoma (GBM). In the current study, we investigate toxicity and response to this regimen and explore associations between gene expression and patient outcome.

EXPERIMENTAL DESIGN

Eighteen newly diagnosed GBM patients received concurrent capecitabine at 625 mg/m2 BID (25% escalation) and irradiation (60 Gy total) for 6 weeks followed by 4 weeks of capecitabine only. Maintenance capecitabine was administered for 14 days every 3 weeks until progression or unacceptable toxicity. Expression analysis of 94 genes involved in capecitabine metabolism and radiation response was done on tissues obtained before therapy. The relationship of gene expression with time-to-progression (TTP) and overall survival (OS) was investigated using univariate Cox proportional hazards regression, semi-supervised principle component analysis, and class prediction modeling.

RESULTS

The maximum tolerated dose of capecitabine was 625 mg/m2 BID. Median patient TTP and OS were 247 and 367 days, respectively. Cox regression identified 24 genes significantly (P<0.025) associated with patient outcome. Semi-supervised principle component analysis identified two patient populations significantly different in both TTP (P=0.005) and OS (P=0.015). Class prediction modeling determined that eight genes (RAD54B, MTOR, DCTD, APEX2, TK1, RRM2, SLC29A1, and ERCC6) could collectively classify patients into outcome subgroups with 100% accuracy and precision.

CONCLUSIONS

Capecitabine and concurrent radiation for newly diagnosed GBM seems to be well tolerated and comparable to temozolomide and radiation. A gene expression profile predictive of patient outcome that may be useful in patient stratification for therapy was also elucidated.

Epstein-Barr virus latent membrane protein 1 induces the chemotherapeutic target, thymidine phosphorylase, via NF-kappaB and p38 MAPK pathways

High thymidine phosphorylase (TP) expression is significantly correlated with poor prognosis in patients with nasopharyngeal carcinoma (NPC). NPC is an Epstein-Barr Virus (EBV)-associated cancer in which the EBV-encoded oncogene product, latent membrane protein 1 (LMP1), is expressed in approximately 60% of tumor tissues. However, no previous study has examined whether LMP1 is involved in up-regulating TP expression in NPC tissues. We herein show that LMP1 expression is correlated with TP expression in tumor cells, as examined by quantitative RT-PCR and immunohistochemical staining. We further show that the CTAR1 and CTAR2 domains of LMP1 mediate TP induction, as demonstrated by quantitative RT-PCR and Western blot analyses using LMP1 deletion and site-specific mutants. Mechanistically, LMP1-mediated TP induction is abolished by inhibitors of NF-kappaB and p38 MAPK, dominant-negative IkappaB and p38, and siRNA-mediated knockdown of p38 MAPK. Clinically, there were significant correlations among the expression levels of TP, activated p65, and phospho-p38 MAPK in NPC biopsy samples. Functionally, LMP1-mediated induction of TP expression enhanced the sensitivity of NPC cells to the chemotherapeutic prodrug, 5'-DFUR. Our results provide new insights into the roles of LMP1-mediated NF-kappaB and p38 MAPK signaling pathways in TP induction, potentially suggesting new therapeutic strategies for the treatment of NPC.

Molecular mechanism underlying the synergistic interaction between trifluorothymidine and the epidermal growth factor receptor inhibitor erlotinib in human colorectal cancer cell lines

The pyrimidine trifluorothymidine (TFT) inhibits thymidylate synthase (TS) and can be incorporated into the DNA. TFT, as part of TAS-102, is clinically evaluated in phase II studies as an oral chemotherapeutic agent. Erlotinib is a tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR) that is often deregulated in colorectal cancer. This study investigated molecular mechanisms underlying the cytotoxic actions of the combination of an EGFR-tyrosine kinase inhibitor with TFT in colorectal cancer cells Caco2, WiDR, Lovo92, and Colo320. Drug interactions were examined by the sulforhodamine B assay and subsequent combination index (CI) analyses, cell cycle effects by FACS analysis of propidium iodide stained cells, Akt, MAPK and EGFR phosphorylation and expression levels by Western blotting and TS activity by the TS in situ assay. All combination schedules were synergistic in wt-EGFR expressing (but with mutated downstream pathways) WiDR and Lovo92 (CI 0.4-0.8) and very synergistic in Caco2 cells (with wt-EGFR and functional downstream pathways; CI 0.1-0.3), but in EGFR-lacking Colo320 cells, no additional activity was found (CI 1.0-1.2). Synergism was mostly related to the induction of cell cycle arrest and an erlotinib-mediated inhibition of the pro-survival signaling through Akt and MAPK that was activated (phosphorylated) by TFT. Erlotinib inhibited TS activity in EGFR-expressing cell lines, probably due to cell cycle arrest in the G(1) phase. TS activity was slightly lower in the combinations, probably due to cell cycle interference. Taken together, the combination of erlotinib with TFT seems to present a potential strategy in the field of molecular therapeutics.

The role of phosphate in the action of thymidine phosphorylase inhibitors: Implications for the catalytic mechanism

The design and synthesis of 5-fluoro-6-[(2-aminoimidazol-1-yl)methyl]uracil (AIFU), a potent inhibitor of thymidine phosphorylase (TP) with K(i)-values of 11nM (ecTP) and 17nM (hTP), are described. Kinetic studies established that the type of inhibition of TP by AIFU is uncompetitive with respect to inorganic phosphate (or arsenate). The results obtained suggest that AIFU and other zwitterionic thymine analog inhibitors of TP act as transition state analogs, mimicking the anionic thymine leaving group, consistent with an S(N)2-type catalytic mechanism, and anchored by their protonated side chains to the enzyme-bound phosphate by electrostatic and H-bonding interactions.

Antiangiogenic and antitumor activity of 6-(2-aminoethyl)amino-5-chlorouracil, a novel small-molecule inhibitor of thymidine phosphorylase, in combination with the vascular endothelial growth factor-trap

PURPOSE

Tumors produce multiple proangiogenic factors, making it unlikely that agents targeting a single angiogenic pathway will be sufficient to treat the spectrum of tumors that occur clinically. Platelet-derived endothelial cell growth factor has angiogenic activity in vitro and in vivo and is overexpressed in most human cancers, where its expression has been correlated with increased microvessel density, more aggressive tumors, and poorer patient prognosis. Platelet-derived endothelial cell growth factor is identical to the enzyme thymidine phosphorylase (TP), and unlike other angiogenic factors, the proangiogenic actions of TP are dependent on its enzyme activity.

EXPERIMENTAL DESIGN

A potent and specific small-molecule inhibitor of the catalytic activity of TP, 6-(2-aminoethyl)amino-5-chlorouracil (AEAC), was tested for antiangiogenic and antitumor activity in human cancer xenografts in vivo.

RESULTS

Oral administration of AEAC caused 40% to 50% reductions in the growth of A549 non-small cell lung cancer and PANC-1 pancreatic cancer xenografts, but it was not active against a second pancreatic tumor, BxPC-3. AEAC reduced the microvessel density in the tumors, providing evidence for an antiangiogenic action. Equal or better activity was seen when the mice were treated with the vascular endothelial growth factor (VEGF)-Trap, a soluble VEGF decoy receptor, and the combination of AEAC and VEGF-Trap produced additive antitumor activity that was significantly greater than the VEGF-Trap alone. In the A549 tumors, the combination produced tumor regressions.

CONCLUSION

These studies show antitumor activity for a drug targeting TP and suggest that inhibitors of TP could be used to augment the clinical efficacy of drugs targeting the VEGF pathway.

Thymidine kinase 1 and thymidine phosphorylase expression in non-small-cell lung carcinoma in relation to angiogenesis and proliferation

The thymidine salvage pathway enzymes thymidine kinase 1 (TK1) and thymidine phosphorylase (TP) compete for thymidine as a substrate and catalyze opposing synthetic and catabolic reactions that have been implicated in the control of proliferation and angiogenesis, respectively. We investigated the relationship between the expression of TK1 and TP as they relate to proliferation (Ki-67 labeling index) and angiogenesis (Chalkley count of CD31-stained blood vessels) in a series of 110 non-small-cell lung cancer (NSCLC) tumors from patients prospectively enrolled in an imaging trial. TK1 and TP exhibited similar patterns of immunohistochemical distribution, in that each was found in both the nucleus and the cytoplasm of tumor cells. Each enzyme exhibited a significant positive correlation between its levels of nuclear and cytoplasmic expression. A significant positive correlation between TK1 expression and the Ki-67 labeling index (r = 0.53, p<0.001) was observed. TP was significantly positively correlated with Chalkley scoring of CD31 staining in high vs low Chalkley scoring samples (mean TP staining of 115.8 vs 79.9 scoring units, p<0.001), respectively. We did not observe a substantial inverse correlation between the TP and TK1 expression levels in the nuclear compartment (r = -0.17, p=0.08). Tumor size was not found to be associated with TK1, TP, Ki-67, or Chalkley score. These findings provide additional evidence for the role of thymidine metabolism in the complex interaction of proliferation and angiogenesis in NSCLC.

Schiff bases of 3-formylchromone as thymidine phosphorylase inhibitors

3-Formylchromone (1), 3-methyl-7-hydroxychromone (2) and Schiff bases of 3-formylchromone 3-19 have been synthesized and their anti-thymidine phosphorylase inhibitory activity was evaluated. Compounds 1-19 showed a varying degree of thymidine phosphorylase inhibition with IC(50) values 19.77+/-3.25 to 480.21+/-2.34 microM. Their activity was compared with the standard 7-deazaxanthine (IC(50)=39.28+/-0.76 microM). Compound 12 showed an excellent thymidine phosphorylase inhibitory activity with an IC(50) value of 19.77+/-3.25 microM, better than the standard. Compound 4 also showed an excellent inhibitory activity (IC(50)=40.29+/-4.56 microM). The parent 3-formylchromone (1) and 3-methyl-7-hydroxychromone (2) were found to be inactive. The structures of the compounds were elucidated by using spectroscopic techniques, including (1)H NMR, EI MS, IR, UV and elemental analysis.