The activity and expression of thymidine phosphorylase in human solid tumours

Can immunotherapy reinforce chemotherapy efficacy? a new perspective on colorectal cancer treatment

As one of the main threats to human life (the fourth most dangerous and prevalent cancer), colorectal cancer affects many people yearly, decreases patients' quality of life, and causes irreparable financial and social damages. In addition, this type of cancer can metastasize and involve the liver in advanced stages. However, current treatments can't completely eradicate this disease. Chemotherapy and subsequent surgery can be mentioned among the current main treatments for this disease. Chemotherapy has many side effects, and regarding the treatment of this type of tumor, chemotherapy can lead to liver damage, such as steatohepatitis, steatosis, and sinus damage. These damages can eventually lead to liver failure and loss of its functions. Therefore, it seems that other treatments can be used in addition to chemotherapy to increase its efficiency and reduce its side effects. Biological therapies and immunotherapy are one of the leading suggestions for combined treatment. Antibodies (immune checkpoint blockers) and cell therapy (DC and CAR-T cells) are among the immune system-based treatments used to treat tumors. Immunotherapy targets various aspects of the tumor that may lead to 1) the recruitment of immune cells, 2) increasing the immunogenicity of tumor cells, and 3) leading to the elimination of inhibitory mechanisms established by the tumor. Therefore, immunotherapy can be used as a complementary treatment along with chemotherapy. This review will discuss different chemotherapy and immunotherapy methods for colorectal cancer. Then we will talk about the studies that have dealt with combined treatment.

An Understanding of Mechanism-Based Approaches for 1,3,4-Oxadiazole Scaffolds as Cytotoxic Agents and Enzyme Inhibitors

The world's health system is plagued by cancer and a worldwide effort is underway to find new drugs to treat cancer. There has been a significant improvement in understanding the pathogenesis of cancer, but it remains one of the leading causes of death. The imperative 1,3,4-oxadiazole scaffold possesses a wide variety of biological activities, particularly for cancer treatment. In the development of novel 1,3,4-oxadiazole-based drugs, structural modifications are important to ensure high cytotoxicity towards malignant cells. These structural modification strategies have shown promising results when combined with outstanding oxadiazole scaffolds, which selectively interact with nucleic acids, enzymes, and globular proteins. A variety of mechanisms, such as the inhibition of growth factors, enzymes, and kinases, contribute to their antiproliferative effects. The activity of different 1,3,4-oxadiazole conjugates were tested on the different cell lines of different types of cancer. It is demonstrated that 1,3,4-oxadiazole hybridization with other anticancer pharmacophores have different mechanisms of action by targeting various enzymes (thymidylate synthase, HDAC, topoisomerase II, telomerase, thymidine phosphorylase) and many of the proteins that contribute to cancer cell proliferation. The focus of this review is to highlight the anticancer potential, molecular docking, and SAR studies of 1,3,4-oxadiazole derivatives by inhibiting specific cancer biological targets, such as inhibiting telomerase activity, HDAC, thymidylate synthase, and the thymidine phosphorylase enzyme. The purpose of this review is to summarize recent developments and discoveries in the field of anticancer drugs using 1,3,4-oxadiazoles.

Loss of thymidine phosphorylase activity disrupts adipocyte differentiation and induces insulin-resistant lipoatrophic diabetes

BACKGROUND

Thymidine phosphorylase (TP), encoded by the TYMP gene, is a cytosolic enzyme essential for the nucleotide salvage pathway. TP catalyzes the phosphorylation of the deoxyribonucleosides, thymidine and 2'-deoxyuridine, to thymine and uracil. Biallelic TYMP variants are responsible for Mitochondrial NeuroGastroIntestinal Encephalomyopathy (MNGIE), an autosomal recessive disorder characterized in most patients by gastrointestinal and neurological symptoms, ultimately leading to death. Studies on the impact of TYMP variants in cellular systems with relevance to the organs affected in MNGIE are still scarce and the role of TP in adipose tissue remains unexplored.

METHODS

Deep phenotyping was performed in three patients from two families carrying homozygous TYMP variants and presenting with lipoatrophic diabetes. The impact of the loss of TP expression was evaluated using a CRISPR-Cas9-mediated TP knockout (KO) strategy in human adipose stem cells (ASC), which can be differentiated into adipocytes in vitro. Protein expression profiles and cellular characteristics were investigated in this KO model.

RESULTS

All patients had TYMP loss-of-function variants and first presented with generalized loss of adipose tissue and insulin-resistant diabetes. CRISPR-Cas9-mediated TP KO in ASC abolished adipocyte differentiation and decreased insulin response, consistent with the patients' phenotype. This KO also induced major oxidative stress, altered mitochondrial functions, and promoted cellular senescence. This translational study identifies a new role of TP by demonstrating its key regulatory functions in adipose tissue.

CONCLUSIONS

The implication of TP variants in atypical forms of monogenic diabetes shows that genetic diagnosis of lipodystrophic syndromes should include TYMP analysis. The fact that TP is crucial for adipocyte differentiation and function through the control of mitochondrial homeostasis highlights the importance of mitochondria in adipose tissue biology.

Capecitabine Regulates HSP90AB1 Expression and Induces Apoptosis via Akt/SMARCC1/AP-1/ROS Axis in T Cells

Transplant oncology is a newly emerging discipline integrating oncology, transplant medicine, and surgery and has brought malignancy treatment into a new era via transplantation. In this context, obtaining a drug with both immunosuppressive and antitumor effects can take into account the dual needs of preventing both transplant rejection and tumor recurrence in liver transplantation patients with malignancies. Capecitabine (CAP), a classic antitumor drug, has been shown to induce reactive oxygen species (ROS) production and apoptosis in tumor cells. Meanwhile, we have demonstrated that CAP can induce ROS production and apoptosis in T cells to exert immunosuppressive effects, but its underlying molecular mechanism is still unclear. In this study, metronomic doses of CAP were administered to normal mice by gavage, and the spleen was selected for quantitative proteomic and phosphoproteomic analysis. The results showed that CAP significantly reduced the expression of HSP90AB1 and SMARCC1 in the spleen. It was subsequently confirmed that CAP also significantly reduced the expression of HSP90AB1 and SMARCC1 and increased ROS and apoptosis levels in T cells. The results of in vitro experiments showed that HSP90AB1 knockdown resulted in a significant decrease in p-Akt, SMARCC1, p-c-Fos, and p-c-Jun expression levels and a significant increase in ROS and apoptosis levels. HSP90AB1 overexpression significantly inhibited CAP-induced T cell apoptosis by increasing the p-Akt, SMARCC1, p-c-Fos, and p-c-Jun expression levels and reducing the ROS level. In conclusion, HSP90AB1 is a key target of CAP-induced T cell apoptosis via Akt/SMARCC1/AP-1/ROS axis, which provides a novel understanding of CAP-induced T cell apoptosis and lays the experimental foundation for further exploring CAP as an immunosuppressant with antitumor effects to optimize the medication regimen for transplantation patients.

Evaluation of Thymidine Phosphorylase Inhibitors in Glioblastoma and Their Capacity for Temozolomide Potentiation

A number of studies have shown high levels of thymidine phosphorylase (TP) expression in glioblastoma (GBM), with trace or undetectable TP levels in normal developed brain tissue. TP catalyzes the reversible phosphorolysis of thymidine to thymine and 2-deoxyribose-1-phosphate, maintaining nucleoside homeostasis for efficient DNA replication and cell division. The TP-mediated catabolism of thymidine is responsible for multiple protumor processes and can support angiogenesis, glycation of proteins, and alternative metabolism. In this study, we examined the effect of TP inhibition in GBM using the known nanomolar TP inhibitors 5-chloro-6-[1-(2'-iminopyrrolidin-1'-yl)methyl]uracil (TPI) and the analogous 6-[(2'-aminoimidazol-1'-yl)methyl]uracils. Although these TP inhibitors did not demonstrate any appreciable cytotoxicity in GBM cell lines as single agents, they did enhance the cytotoxicity of temozolomide (TMZ). This pontetiated action of TMZ by TP inhibition may be due to limiting the availability of thymine for DNA repair and replication. These studies support that TP inhibitors could be used as chemosensitizing agents in GBM to improve the efficacy of TMZ.

Capecitabine in treating patients with advanced, persistent, or recurrent cervical cancer: an active and safe option?

Introduction: Advanced, persistent or recurrent cervical cancer in patients not amenable to curative surgery or radiotherapy predicts a dismal prognosis. Systemic chemotherapy based on paclitaxel/cisplatin ± bevacizumab is the current standard of care. However, once progression occurs, the possibility of alternative treatment options is very limited.Areas covered: The usefulness of capecitabine has been well-established against several cancer types, including head and neck, breast, and colorectal cancer. This review covers current literature evidence on the clinical efficacy and safety of capecitabine in cervical cancer treatment, either as monotherapy or combined with other agents or chemo-radiotherapy.Expert opinion: Recent clinical data, albeit scant, suggested a promising role for capecitabine both as monotherapy in patients with platinum-resistant cervical cancer and in combination with cisplatin in chemotherapy-naïve patients with metastatic or recurrent cervical cancer. In our opinion, capecitabine, especially in combination regimens, could represent a valid treatment option and further research is warranted to better understand its effectiveness in these challenging patients.

Biodistribution and internal radiation dosimetry of a novel probe for thymidine phosphorylase imaging, [123I]IIMU, in healthy volunteers

OBJECTIVE

We evaluated the radiation dosage, biodistribution, human safety, and tolerability of the injection of a single dose of [¹²³I] 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil (IIMU), a new radiotracer targeting thymidine phosphorylase (TP), in healthy volunteers.

METHODS

Potential participants were tested at our hospital to confirm their eligibility. Two healthy male adults passed the screening tests. They were injected with 56 and 111 MBq of [¹²³I]IIMU, respectively. Safety assessments were performed before and at 1, 3, 6, 9, 24, 48 h, and 1-week post-injection. Whole-body emission scans were conducted at 1, 3, 6, 24, and 48 h post-injection. Regions of interest were manually drawn to enclose the entire body at each time point, identifying high-uptake organs to obtain the time-activity curves. Urine and blood samples were collected at 1, 2, 3, 4, 5, 6, 9, 24, and 48 h post-injection. The radiation dose for each organ and the effective doses were estimated using OLINDA/EXM 1.1 software.

RESULTS

No adverse events were observed as of the follow-up visit > 1-week post-injection. In both subjects, the highest uptake of [¹²³I]IIMU occurred in the liver, with peak injected activity (%IA) values of 17.7% and 15.1%, respectively. The second highest uptake was in the thyroid (0.35% and 0.66% IA). The %IA decreased gradually toward the end of the study (48 h) in all organs except the liver and thyroid. By the end of the study, 52.5% and 51.5% of the injected activity of [¹²³I]IIMU had been excreted via the subjects' renal systems. The estimated mean effective doses of [¹²³I]IIMU were 9.19 μSv/MBq and 10.1 μSv/MBq, respectively.

CONCLUSION

In this preliminary study, [¹²³I]IIMU was safely administered to healthy adults, and its potential clinical use in TP imaging was revealed.

Enhanced Anticancer Activity of 5'-DFUR-PCL-MPEG Polymeric Prodrug Micelles Encapsulating Chemotherapeutic Drugs

The compound 5’-deoxy-5-fluorouridine (5’-DFUR) is a prodrug of the anti-tumor drug 5-fluorouracil (5-FU). Thymidine phosphorylase (TP) is an enzyme that can convert 5’-DFUR to its active form 5-FU and the expression of TP is upregulated in various cancer cells. In this study, 5’-DFUR associated with amphiphilic copolymer poly(ε-caprolactone)-methoxy poly(ethylene glycol) (5’-DFUR-PCL-MPEG) was synthesized, characterized, and self-assembled into functional polymeric micelles. To demonstrate that the prodrug 5’-DFUR could convert into cytotoxic 5-fluorouracil (5-FU) by endogenous TP, HT-29 colorectal cancer cells were treated with 5’-DFUR-PCL-MPEG polymeric micelles for various time periods. Chemotherapeutic drugs doxorubicin (DOX) and 7-ethyl-10-hydroxycamptothecin (SN-38) were also encapsulated separately into 5’-DFUR-PCL-MPEG polymeric micelles to create a dual drug-loaded system. HT-29 cells were treated with DOX or SN-38 encapsulated 5’-DFUR-PCL-MPEG polymeric micelles to examine the efficacy of dual drug-loaded micelles. As a result, HT-29 cells treated with 5’-DFUR-PCL-MPEG polymeric micelles showed up to 40% cell death rate after a 72-h treatment. In contrast, HT-29 cells challenged with DOX or SN-38 encapsulated 5’-DFUR-incorporated polymeric micelles showed 36% and 31% in cell viability after a 72-h treatment, respectively.

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 Catabolism as a Metabolic Strategy for Cancer Survival

Thymidine phosphorylase (TP), a rate-limiting enzyme in thymidine catabolism, plays a pivotal role in tumor progression; however, the mechanisms underlying this role are not fully understood. Here, we found that TP-mediated thymidine catabolism could supply the carbon source in the glycolytic pathway and thus contribute to cell survival under conditions of nutrient deprivation. In TP-expressing cells, thymidine was converted to metabolites, including glucose 6-phosphate, lactate, 5-phospho-α-D-ribose 1-diphosphate, and serine, via the glycolytic pathway both in vitro and in vivo. These thymidine-derived metabolites were required for the survival of cells under low-glucose conditions. Furthermore, activation of thymidine catabolism was observed in human gastric cancer. These findings demonstrate that thymidine can serve as a glycolytic pathway substrate in human cancer cells.

Thymidine phosphorylase expression and prognosis in colorectal cancer treated with 5-fluorouracil-based chemotherapy: A meta-analysis

In the past decades, various studies have suggested a possible link between thymidine phosphorylase (TP) level and colorectal cancer (CRC) treated with 5-fluorouracil (5-FU)-based chemotherapy; however, they have arrived at inconsistent results. Therefore, the present meta-analysis aimed to disclose a more comprehensive evaluation of this relationship. PubMed, the Cochrane Library, Ovid MEDLINE, Embase and China National Knowledge Infrastructure were systematically searched for studies that evaluated the prognostic value of TP in CRC. Stata 12.0 software was used to test the heterogeneity and evaluate the overall test performance. A total of 15 studies, including 1,225 patients, were included. The summary estimates of TP for CRC treated with 5-FU-based chemotherapy indicated a moderately positive prognosis with a hazard ratio (HR) of 0.76 (P=0.031) for overall survival and a HR of 0.711 (P=0.022) for relapse-free survival. On the basis of the present meta-analysis, TP could be promising and meaningful in the prognosis of CRC treated with 5-FU-based chemotherapy.

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 exerts complex effects on bone resorption and formation in myeloma

Myelomatous bone disease is characterized by the development of lytic bone lesions and a concomitant reduction in bone formation, leading to chronic bone pain and fractures. To understand the underlying mechanism, we investigated the contribution of myeloma-expressed thymidine phosphorylase (TP) to bone lesions. In osteoblast progenitors, TP up-regulated the methylation of RUNX2 and osterix, leading to decreased bone formation. In osteoclast progenitors, TP up-regulated the methylation of IRF8 and thereby enhanced expression of NFATc1 (nuclear factor of activated T cells, cytoplasmic 1 protein), leading to increased bone resorption. TP reversibly catalyzes thymidine into thymine and 2-deoxy-d-ribose (2DDR). Myeloma-secreted 2DDR bound to integrin αVβ3/α5β1 in the progenitors, activated PI3K (phosphoinositide 3-kinase)/Akt signaling, and increased DNMT3A (DNA methyltransferase 3A) expression, resulting in hypermethylation of RUNX2, osterix, and IRF8 This study elucidates an important mechanism for myeloma-induced bone lesions, suggesting that targeting TP may be a viable approach to healing resorbed bone in patients. Because TP overexpression is common in bone-metastatic tumors, our findings could have additional mechanistic implications.

A novel antimetabolite: TAS-102 for metastatic colorectal cancer

TAS-102 is a new oral anti-tumor drug, composed of a thymidine-based nucleoside analog (trifluridine: FTD) and a thymidine phosphorylase inhibitor (tipiracil hydrochloride: TPI). TAS-102 has been shown to significantly improve overall survival and progression-free survival in patients with refractory metastatic colorectal cancer (mCRC) in placebo-controlled randomized phase II and III trials. The current review summarizes mechanisms of action, pharmacokinetics/dynamics and preclinical and clinical data of TAS-102 in colorectal cancer. TAS-102 is a new salvage-line treatment option for patients with mCRC. TAS-102 is well tolerated and has great potential in future clinical drug combination therapies.

TAS-102: a novel antimetabolite for the 21st century

TAS-102, a novel antimetabolite combination chemotherapy agent, consists of a rediscovered antimetabolite agent, trifluorothymidine (trifluridine) combined with the metabolic inhibitor of thymidine phosphorylase, tipiracil, in a 1:0.5 molar ratio. Mechanism of action studies suggest that this agent works by incorporation into DNA. Both preclinical and clinical studies demonstrate that this agent is noncross-resistant with 5-fluorouracil. Tipiracil may also have antiangiogenic effects through inhibition of thymidine phosphorylase. Recent randomized Phase II and III trials demonstrate clinical activity (improved progression-free survival, time to decrease in performance status, prolonged overall survival) in metastatic colorectal cancer refractory to all standard agents. Monotherapy with TAS-102 has now been approved for this indication in Japan and in the USA.

Therapeutic potential of TAS-102 in the treatment of gastrointestinal malignancies

Fluoropyrimidines form the mainstay in treatment of gastrointestinal malignancies. For decades 5-fluorouracil (5FU), was the major fluoropyrimidine. Currently it is usually given in a combination with leucovorin and oxaliplatin, i.e. FOLFOX, or irinotecan, i.e. FOLFIRI, or all three, i.e. FOLFIRINOX, but gradually it has been replaced by oral fluoropyrimidine prodrug formulations, such as tegafur-uracil and S-1 (both contain ftorafur), and capecitabine (Xeloda®). Novel drugs such as the antivascular endothelial growth factor antibody, bevacizumab, and the anti-epidermal growth factor receptor antibody, cetuximab, are often combined with one of these treatment options. However, when resistance emerged, no alternatives were available. TAS-102, a combination of trifluorothymidine and the thymidine phosphorylase inhibitor TPI in a 1:0.5 ratio, is a novel oral formulation, which is active in 5FU-resistant models, both in vitro and in xenograft models. In addition to inhibition of thymidylate synthase, the major mechanism of action of classical fluoropyrimidines, TAS-102's major mechanism of action is incorporation into DNA, thereby causing DNA damage. TAS-102 also follows an alternative activation pathway via thymidine kinase, and is not a substrate for dihydropyrimidine dehydrogenase. All together this explains the efficacy in 5FU-resistant models. In early clinical studies, the twice-daily schedule (5 days on, 2 days rest) for 2 weeks every 4 weeks, led to a significant disease control rate in various malignancies. This schedule showed consistent activity in two randomized trials on fluoropyrimidine refractory colorectal cancer patients, reflected by an increase of 2-3 months in overall survival in the TAS-102 group compared with placebo. Considering the impressive preclinical potential of various combinations TAS-102 has the promise to become an alternative for 5FU-resistant cancer.

Differential interference of vitamin D analogs PRI-1906, PRI-2191, and PRI-2205 with the renewal of human colon cancer cells refractory to treatment with 5-fluorouracil

This study was aimed to determine whether hypocalcemic analogs of active forms of vitamins D modulate expression of genes related to stem-like phenotype in colon cancer cell lines HT-29 and HCT-116 undergoing renewal after the treatment with 5-fluorouracil (5-FU). Both lines express vitamin D receptor, but differ in differentiation stage and vitamin D sensitivity. Cells that resisted the 5-FU exposure were treated with synthetic analog of 1,25-dihydroxyvitamin D2 (PRI-1906) and analogs of 1,25-dihydroxyvitamin D3 (PRI-2191 and PRI-2205). Proliferative activity was more profoundly affected by vitamin D analogs in HT-29/5-FU than in HCT-116/5-FU cells. In HT-29/5-FU cells, analogs PRI-1906 and PRI-2191 downregulated the expression of genes related to survival, re-growth, and invasiveness during renewal, while PRI-2205 increased expression of genes related to differentiation only. In HCT-116/5-FU cells, PRI-2191 decreased the expression of stemness- and angiogenesis-related genes, whereas PRI-1906 augmented their expression. The effects in HCT-116/5-FU cells were observed at higher concentrations of the analogs than those used for HT-29/5-FU cells. Out of the series of analogs studied, PRI-2191 might be used to counteract the renewal of both moderately and poorly differentiated cancer cells following conventional treatment.

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

Thymidine phosphorylase regulates the expression of CXCL10 in rheumatoid arthritis fibroblast-like synoviocytes

OBJECTIVE

Thymidine phosphorylase (TP) in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) is induced by tumor necrosis factor α (TNFα) and other cytokines that have been reported to be major inflammation mediators in RA. We previously demonstrated that TP plays an important role in angiogenesis and tumor growth, invasion, and metastasis. The aim of this study was to investigate whether the role of TP in the pathogenesis of RA is similar to its role in tumors.

METHODS

In FLS obtained from 2 patients with RA, the expression of TP, interferon-γ (IFNγ)-inducible protein 10 (CXCL10), and other cytokines was measured by quantitative real-time polymerase chain reaction, immunoblotting, and enzyme-linked immunosorbent assays. Microarray analysis was performed using FLS transfected with TYMP complementary DNA and treated with a TP inhibitor.

RESULTS

The expression of TP in FLS was up-regulated by TNFα, interleukin-1β (IL-1β), IL-17, IFNγ, and lipopolysaccharide. Microarray analysis of FLS overexpressing TP identified CXCL10 as a thymidine phosphorylase-related gene. The expression of CXCL10 was induced by TNFα, and this induction was suppressed by TYMP small interfering RNA and TP inhibitor. Furthermore, the combination of TNFα and IFNγ synergistically augmented the expression of TP and CXCL10. TP-induced CXCL10 expression was suppressed by the antioxidant EUK-8. In the synovial tissue of patients with RA, TP levels were significantly correlated with CXCL10 expression.

CONCLUSION

The combination of TNFα and IFNγ strongly induced the expression of thymidine phosphorylase in RA FLS. The induction of thymidine phosphorylase enhanced the expression of CXCL10, which may contribute to the Th1 phenotype and bone destruction observed in RA.

Synthesis and in vitro evaluation of 1,2,4-triazolo[1,5-a][1,3,5]triazine derivatives as thymidine phosphorylase inhibitors

In our lead finding program, a series of 1,2,4-triazolo[1,5-a][1,3,5]triazine derivatives were synthesized, and their in vitro thymidine phosphorylase inhibitory potential was explored. Among the different derivatives, compounds having keto group (C = O) at C7 and thioketo group (C = S) at C5 positions showed varying degrees of TP inhibitory activity comparable with positive control, 7-deazaxanthine (7-DX, 2) (IC50 value = 42.63 μm). Enzyme inhibition kinetics study suggested that compound IVn behaved as a mixed-type inhibitor of the enzyme with respect to thymidine (dThd) as a variable substrate. Compound IVn was also found to inhibit PMA-induced MMP-9 expression in MDA-MB-231 cells at sublethal concentrations. Computational docking study was performed to illustrate the enzyme inhibition kinetics and to explore the ligand-enzyme interactions.

Molecular basis for the regulation of hypoxia-inducible factor-1α levels by 2-deoxy-D-ribose

The angiogenic factor, platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP), stimulates the chemotaxis of endothelial cells and confers resistance to apoptosis induced by hypoxia. 2-Deoxy-D-ribose, a degradation product of thymidine generated by TP enzymatic activity, inhibits the upregulation of hypoxia-inducible factor (HIF) 1α, BNIP3 and caspase-3 induced by hypoxia. In the present study, we investigated the molecular basis for the suppressive effect of 2-deoxy-D-ribose on the upregulation of HIF-1α. 2-Deoxy-D-ribose enhanced the interaction of HIF-1α and the von Hippel-Lindau (VHL) protein under hypoxic conditions. It did not affect the expression of HIF-1α, prolyl hydroxylase (PHD)1/2/3 and VHL mRNA under normoxic or hypoxic conditions, but enhanced the interaction of HIF-1α and PHD2 under hypoxic conditions. 2-Deoxy-D-ribose also increased the amount of hydroxy-HIF-1α in the presence of the proteasome inhibitor MG-132. The expression levels of TP are elevated in many types of malignant solid tumors and, thus, 2-deoxy-D-ribose generated by TP in these tumors may play an important role in tumor progression by preventing hypoxia-induced apoptosis.

Glycation of glutamate cysteine ligase by 2-deoxy-d-ribose and its potential impact on chemoresistance in glioblastoma

The antioxidant glutathione (GSH) plays a critical role in maintaining intracellular redox homeostasis but in tumors the GSH biosynthetic pathway is often dysregulated, contributing to tumor resistance to radiation and chemotherapy. Glutamate-cysteine ligase (GCL) catalyzes the first and rate-limiting reaction in GSH synthesis, and enzyme function is controlled by GSH feedback inhibition or by transcriptional upregulation of the catalytic (GCLC) and modifier (GCLM) subunits. However, it has recently been reported that the activity of GCLC and the formation of GCL can be modified by reactive aldehyde products derived from lipid peroxidation. Due to the susceptibility of GCLC to posttranslational modifications by reactive aldehydes, we examined the potential for 2-deoxy-D-ribose (2dDR) to glycate GCLC and regulate enzyme activity and GCL formation. 2dDR was found to directly modify both GCLC and GCLM in vitro, resulting in a significant inhibition of GCLC and GCL enzyme activity without altering substrate affinity or feedback inhibition. 2dDR-mediated glycation also inhibited GCL subunit heterodimerization and formation of the GCL holoenzyme complex while not causing dissociation of pre-formed holoenzyme. This PTM could be of particular importance in glioblastoma (GBM) where intratumoral necrosis provides an abundance of thymidine, which can be metabolized by thymidine phosphorylase (TP) to form 2dDR. TP is expressed at high levels in human GBM tumors and shRNA knockdown of TP in U87 GBM cells results in a significant increase in cellular GCL enzymatic activity.

Thymidine Phosphorylase Gene Expression in Stage III Colorectal Cancer

BACKGROUND

The thymidine phosphorylase (TP) enzyme has several tumor-promoting functions. The aim of this study was to explore TP gene expression in relation to clinical and histopathological data obtained from patients with stage III colorectal cancer.

METHODS AND RESULTS

TP gene expression was analyzed by real-time quantitative PCR in tumor and mucosa samples from 254 patients. TP gene expression in tumors correlated with lymph node staging, with higher expression relating to a higher number of positive nodes and a worse N-stage. Higher TP expression was also associated with a worse histological tumor grade. Patients with rectal cancer had significantly higher TP expression in mucosa and tumors compared with patients having colon cancer.

CONCLUSION

Higher intratumoral TP expression appears to be related to a worse N stage, and thus, with a worse prognosis. TP gene expression measured in a preoperative biopsy could be of interest in preoperative staging.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Improvement of capecitabine antitumoral activity by melatonin in pancreatic cancer

OBJECTIVE

The purpose of our study was to evaluate the effects of the addition of melatonin and capecitabine on experimental pancreatic cancer.

METHODS

Fifty Syrian hamsters were randomized in 5 groups: group 1: no tumor induction (control group); group 2: tumor induction with BOP [N-nitrosobis(2-oxopropyl) amine]; group 3: tumor induction with BOP and melatonin administration; group 4: tumor induction with BOP and capecitabine administration; and group 5: tumor induction with BOP and administration of combined capecitabine and melatonin therapy. The evaluation of pathological tumor evolution and oxidative stress markers in pancreatic tissue was carried out.

RESULTS

All animals under BOP exposure presented poorly or moderately differentiated pancreatic adenocarcinoma associated with increased lipoperoxide levels and decreased antioxidant activity in pancreatic tissue. Pancreatic cancer was shown in only 66% of the capecitabine-treated group and 33% of melatonin-treated group (P < 0.05), most of them moderately differentiated adenocarcinoma. When capecitabine and melatonin were combined, a well-differentiated pancreatic adenocarcinoma was observed in 10% of animals. The beneficial effect was associated with a decrease in lipoperoxide levels and increased antioxidant activity in pancreatic tissue.

CONCLUSIONS

The combined administration of capecitabine and melatonin provided an improvement in antioxidant status as well as a synergistic antitumoral effect in experimental pancreatic cancer.

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.

The dual role of thymidine phosphorylase in cancer development and chemotherapy

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

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.

Phase II trial of capecitabine and weekly docetaxel for metastatic castrate resistant prostate cancer

PURPOSE

Synergy is observed with the combination of capecitabine and docetaxel due to docetaxel mediated up-regulation of thymidine phosphorylase. A phase II trial was performed with the combination for metastatic, castrate resistant prostate cancer.

MATERIALS AND METHODS

Eligible patients had metastatic, castrate resistant prostate cancer, no prior chemotherapy for metastatic disease and normal organ function. Docetaxel (36 mg/m(2) per week intravenously) on days 1, 8 and 15, and capecitabine (1,250 mg/m(2) per day in 2 divided doses) on days 5 to 18 were administered in 28-day cycles. The response was assessed every 2 cycles. Biomarker correlative studies were performed on blood dihydropyrimidine dehydrogenase, and the thymidine phosphorylase-to-dihydropyrimidine dehydrogenase and thymidine synthase-to-dihydropyrimidine dehydrogenase ratios in available prostate tumor tissue.

RESULTS

A total of 30 patients with a median age of 69 years were enrolled in the study. We noted bone pain in 21 patients (70%), Gleason score 8 or higher in 18 (60%), measurable disease progression in 9, bone scan progression in 18 and prostate specific antigen progression in 22. Grade 3 or 4 neutropenia was seen in 3 patients and grade 3 hand-foot syndrome was found in 2. No treatment related deaths occurred. A prostate specific antigen response of 50% or greater decrease was observed in 22 patients (73%), of whom 9 (30%) had 90% or greater decrease. A partial response was noted in 5 of 9 patients (56%) with measurable disease. Median time to progression was 6.7 months (90% CI 4.2-7.7) and median overall survival was 22.0 months (90% CI 18.4-25.3).

CONCLUSIONS

The combination was well tolerated and it demonstrated favorable response rates with durable remission and survival outcomes.

Substrate specificity of thymidine phosphorylase of E. coli: role of hydroxyl groups

Substrate specificity of E. coli thymidine phosphorylase to pyrimidine nucleoside modified at 5'-, 3'-, and 2'-positions of sugar moiety has been studied. Equilibrium (K(eq)) and kinetics constants of phosphorolysis reaction of nucleosides were measured. The most important hydrogen bonds in enzyme-substrate complex have been determined.

The cytosol activity of thymidine phosphorylase in endometrial cancer

BACKGROUND

Thymidine phosphorylase (TP) is identical with platelet-derived endothelial cell growth factor (PD-ECGF) which promotes angiogenesis. The aim of this study was to evaluate the cytosol activity of TP in tumor samples from patients with endometrial cancer.

METHODS

The activity of TP was measured by the spectrophotometric method in the cytosol of endometrial tumor samples from 43 patients. Moreover, the expression of platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) protein and microvessel density (MD) were examined in the same endometrial tumor samples by immunohistochemical staining. Normal endometrium from 16 women, treated surgically due to nononcological reasons served as a control.A relationship between the cytosol TP activity, PD-ECGF/TP protein expression, MD and clinicopathologic features was investigated.

RESULTS

A significantly higher the cytosol TP activity, PD-ECGF/TP protein expression and MD was stated in malignant tumor samples when compared to the control (samples of normal endometrium). A positive statistically significant correlation between the cytosol enzyme activity and PD-ECGF/TP protein expression and MD was found, but weaker from the remaining ones between PD-ECGF/TP protein expression and MD was observed.Besides no correlation between the cytosol TP activity, PD-ECGF/TP protein expression as well as MD and grading or histopatological type of endometrial cancer was stated.

CONCLUSION

The cytosol TP activity in endometrial cancer is significantly higher than in normal endometrium, with no relation as to the stage and grade of tumors, but correlates with the PD-ECGF/TP protein expression and MD may therefore be associated with favorable prognosis in patients treated with chemo- or radiotherapy after surgery.

Angiogenic factor thymidine phosphorylase increases cancer cell invasion activity in patients with gastric adenocarcinoma

We investigated the biological role of thymidine phosphorylase (TP), an angiogenic factor, in gastric cancer cell migration and invasion and explored a therapeutic approach for high TP-expressing tumors using TP enzymatic inhibitor (TPI) and rapamycin. We established TP cDNA overexpressing gastric cancer cell lines (MKN-45/TP and YCC-3/TP) and did invasion and adhesion assays with Matrigel-coated transwell membranes. The related signal pathway using recombinant human TP (rhTP), deoxy-d-ribose (D-dRib), and signal pathway inhibitors (wortmannin, LY294002, and rapamycin) was investigated. First, AGS and MKN-1 gastric cancer cell lines showed dose-dependent up-regulation of invasiveness through Matrigel following treatment with rhTP or D-dRib. TP-overexpressing cancer cell lines displayed increased migration and invasion activity, which doubled with rhTP and D-dRib treatment. This activity depended on the enzymatic activity of TP, and TP stimulated the adhesion of cancer cells onto Matrigel and induced actin filament remodeling. Finally, we showed that this activity is related to increased phosphatidylinositol 3-kinase activity in TP-overexpressing cells and that combination treatment with rapamycin and TP enzymatic inhibitor produces an additive effect to abrogate TP-induced invasion. Taken together, TP increases the migration and invasion of gastric cancer cells, especially in TP-expressing cells. Therapies targeting TP might diminish the propensity for invasion and metastasis in gastric cancer.

Efficacy of laser capture microdissection plus RT-PCR technique in analyzing gene expression levels in human gastric cancer and colon cancer

Background

Thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase gene expressions are reported to be valid predictive markers for 5-fluorouracil sensitivity to gastrointestinal cancer. For more reliable predictability, their expressions in cancer cells and stromal cells in the cancerous tissue (cancerous stroma) have been separately investigated using laser capture microdissection.

Methods

Thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase mRNA in cancer cells and cancerous stroma from samples of 47 gastric and 43 colon cancers were separately quantified by reverse transcription polymerase chain reaction after laser capture microdissection.

Results

In both gastric and colon cancers, thymidylate synthase and orotate phosphoribosyltransferase mRNA expressions were higher (p < 0.0001, p <0.0001 respectively in gastric cancer and P = 0.0002, p < 0.0001 respectively in colon cancer) and dihydropyrimidine dehydrogenase mRNA expressions were lower in cancer cells than in cancerous stroma (P = 0.0136 in gastric cancer and p < 0.0001 in colon cancer). In contrast, thymidine phosphorylase mRNA was higher in cancer cells than in cancerous stroma in gastric cancer (p < 0.0001) and lower in cancer cells than in cancerous stroma in colon cancer (P = 0.0055).

Conclusion

By using this method, we could estimate gene expressions separately in cancer cells and stromal cells from colon and gastric cancers, in spite of the amount of stromal tissue. Our method is thought to be useful for accurately evaluating intratumoral gene expressions.

Phase II evaluation of capecitabine in refractory nonsquamous cell carcinoma of the cervix: a Gynecologic Oncology Group Study

We conducted a multi-institutional study to assess the activity and toxicity of capecitabine in patients with persistent or recurrent nonsquamous cancer of the cervix. Eligible patients were required to possess adequate renal, hepatic and bone marrow function and a Gynecologic Oncology Group performance status of 0-2. Histologic confirmation of the original primary cancer was mandated. Patients must have received one prior systemic chemotherapeutic regimen for cervical cancer that did not include the chemotherapy that may have been administered in conjunction with prior radiation therapy. The initial dose schedule was 2500 mg/m2 orally daily in two divided doses for 14 consecutive days, followed by a 7-day rest, such that each cycle was 21 days. Responses were assessed using response evaluation criteria in solid tumors. Twenty-one patients were entered into the trial. One patient was declared ineligible for wrong cell type; thus, 20 were evaluable for toxicity. A median of 2.5 cycles was administered (range 1-11). There was one septic death. Grade 4 neutropenia, renal, neurologic, and pulmonary toxicity was seen in 5%, 5%, 5%, and 10% patients, respectively. There were no responses. Nine patients (45%) each had stable disease and nine showed progression. The remaining two cases (10%) did not have subsequent disease assessment and response could not be assessed. Oral capecitabine at the dose and schedule tested has insignificant activity in nonsquamous cervical cancer patients previously treated with chemotherapy.

Pharmacogenetic approach for capecitabine or 5-fluorouracil selection to be combined with oxaliplatin as first-line chemotherapy in advanced colorectal cancer

We studied the role of TS (5'VNTR, 5'SNP and 3'UTR), XRCC1-399, XPD-751, ERCC1-118 and XRCC3-241 genetic polymorphisms in tailoring fluroropyrimidine/oxaliplatin treatment. For this purpose, 110 XELOX (capecitabine/oxaliplatin)- or FUOX (fluorouracil/oxaliplatin)-treated metastatic colorectal cancer patients were selected prospectively for genotyping. In the FUOX group, TS-3'UTR +6bp/+6bp (hazards ratio, HR=2.62, p=0.007) and ERCC1-118C/T or C/C (HR=1.96, p=0.050) genotypes correlated with a shorter progression-free survival (PFS). When analysed jointly, the higher the number of favourable genotypes (FG) the longer the PFS (6.8m, 9.6m and 25.8m for 0, 1 or 2 FG; p=0.005). Disease-control rate was 100% in patients with 2 FG (87% and 38.5% for 1 or 0 FG; p=0.001). In the multivariate analysis, ERCC1-118 (HR=2.12, p=0.0037) and TS-3'UTR (HR=2.68, p=0.006) were strong independent prognostic factors. According to this, patients harbouring TS-3'UTR +6bp/+6bp and ERCC1-118C/T or C/C genotypes may better receive capecitabine instead of 5FU in an oxaliplatin-based first-line treatment.

Thymidine phosphorylase inhibits the expression of proapoptotic protein BNIP3

An angiogenic factor, thymidine phosphorylase (TP), confers resistance to apoptosis induced by hypoxia. We investigated the molecular basis for the suppressive effect of TP on hypoxia-induced apoptosis using Jurkat cells transfected with TP cDNA, Jurkat/TP, and a mock transfectant, Jurkat/CV. TP and 2-deoxy-d-ribose, a degradation product of thymidine generated by TP enzymatic activity, suppressed hypoxia-induced apoptosis. They also inhibited the upregulation of hypoxia-inducible factor (HIF) 1alpha and the proapoptotic factor, BNIP3, and caspase 3 activation induced by hypoxia. Introduction of siRNA against BNIP3 in Jurkat cells decreased the proportion of apoptotic cells under hypoxic condition. These findings suggest that the suppression of BNIP3 expression by TP prevents, at least in part, hypoxia-induced apoptosis. Expression levels of TP are elevated in many malignant solid tumors and thus 2-deoxy-d-ribose generated by TP in these tumors might play an important role in tumor progression by preventing hypoxia-induced apoptosis.

Neoadjuvant docetaxel and capecitabine in patients with high risk prostate cancer

PURPOSE

Docetaxel is the most active cytotoxic agent in hormone refractory prostate cancer. Preclinically docetaxel increases expression of thymidine phosphorylase, an enzyme responsible for activation of capecitabine to 5-fluorouracil resulting in increased antitumor activity. We assessed activity and safety of neoadjuvant docetaxel and capecitabine in patients with high risk prostate cancer.

MATERIALS AND METHODS

Patients with either clinical stage greater than T2, prostate specific antigen 15 ng/ml or more, or Gleason sum 8 or greater received 3 to 6 cycles of docetaxel (36 mg/m2 intravenously on days 1, 8 and 15) and capecitabine (1,250 mg/m2 per day orally divided twice a day on days 5 to 18) every 28 days, followed by local therapy. The primary end point was rate of 50% or greater prostate specific antigen decrease. Correlative studies included qualitative changes in histology, tissue thymidine phosphorylase and survivin expression, and CK18Asp396 (serum apoptosis marker).

RESULTS

A total of 15 patients were treated, of whom 6 (40%) experienced a 50% or greater decrease in prostate specific antigen with infrequent diarrhea or hand-foot syndrome. Eleven patients underwent radical prostatectomy. There were no pathological complete responses and 4 patients demonstrated mild histological changes, including focal necrosis and vacuolated cytoplasm. While there was no discernable pattern of increased thymidine phosphorylase expression, 4 specimens showed decreased survivin expression, suggesting a possible mechanism for chemotherapy induced apoptosis. There was no correlation of prostate specific antigen response and survivin expression, and no increase in serum CK18Asp396.

CONCLUSIONS

Neoadjuvant docetaxel and capecitabine is well tolerated but is not associated with significant pathological and prostate specific antigen responses.

A Randomized, Double-Blind, Phase II Study of Two Doses of Pemetrexed as First-Line Chemotherapy for Advanced Breast Cancer

PURPOSE

Pemetrexed has shown varied response rates in advanced breast cancer. This randomized, double-blind, phase II study was conducted to assess the efficacy and safety of two doses of pemetrexed in a homogeneous population. A secondary objective was to identify molecular biomarkers correlating with response and toxicity.

EXPERIMENTAL DESIGN

Patients with newly diagnosed metastatic breast cancer or locally recurrent breast cancer received 600 mg/m(2) (P600 arm) or 900 mg/m(2) (P900 arm) of pemetrexed on day 1 of a 21-day cycle. All patients received folic acid and vitamin B(12) supplementation.

RESULTS

The P600 (47 patients) and P900 (45 patients) arms had response rates of 17.0% (95% confidence interval, 7.7-30.8%) and 15.6% (95% confidence interval, 6.5-29.5%) with approximately 50% stable disease per arm, median progression-free survival of 4.2 and 4.1 months, and median times to tumor progression of 4.2 and 4.6 months, respectively. Both arms exhibited minimal toxicity (grade 3/4 neutropenia <20%, leukopenia <9%, and other toxicities <5%). Tumor samples from 49 patients were assessed for the expression levels of 12 pemetrexed-related genes. Folylpolyglutamate synthetase and thymidine phosphorylase correlated with efficacy. Best response rates and median time to tumor progression for high versus low thymidine phosphorylase expression were 27.6% versus 6.3% (P = 0.023) and 5.4 versus 1.9 months (P = 0.076), and for folylpolyglutamate synthetase were 37.5% versus 10.0% (P = 0.115) and 8.6 versus 3.0 months (P = 0.019), respectively. gamma-Glutamyl hydrolase expression correlated with grade 3/4 toxicities: 78.6% for high versus 27.3% for low gamma-glutamyl hydrolase (P = 0.024).

CONCLUSION

The two pemetrexed doses yielded similar efficacy and safety profiles. Exploratory biomarker analysis identified efficacy and toxicity correlations and warrants further evaluation.