Thymidine phosphorylase mediates the sensitivity of human colon carcinoma cells to 5-fluorouracil

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 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.

Conditioned media from human macrophages of M1 phenotype attenuate the cytotoxic effect of 5‑fluorouracil on the HT‑29 colon cancer cell line

Resistance of tumor cells to chemotherapy, such as 5-fluorouracil (5-FU), is an obstacle for successful treatment of cancer. As a follow-up of a previous study we have investigated the effect of conditioned media (CM) from macrophages of M1 or M2 phenotypes on 5-FU cytotoxicity on the colon cancer cell lines HT-29 and CACO-2. HT-29 cells, but not CACO-2 cells, having been treated with a combination of M1 CM and 5-FU recovered their cell growth to a much larger extent compared to cells having been treated with 5-FU alone when further cultured for 7 days in fresh media. M1 CM treatment of HT-29, but not CACO-2 cells, induced cell cycle arrest in the G₀/G₁ and G₂/M phases. 5-FU treatment induced accumulation of cells in S-phase in both HT-29 and CACO-2 cells. This accumulation of cells in S-phase was attenuated by combined M1 CM and 5-FU treatment in HT-29 cells, but not in CACO-2 cells. The mRNA expression of cell cycle regulatory proteins and 5-FU metabolic enzymes were analyzed in an attempt to find possible mechanisms for the M1 CM induced attenuation of 5-FU cytotoxicity in HT-29. Thymidylate synthetase (TS) and thymidine phosphorylase (TP) were found to be substantially downregulated and upregulated, respectively, in HT-29 cells treated with M1 CM, making them unlikely as mediators of reduced 5-FU cytotoxicity. Among cell cycle regulating proteins, p21 was induced in HT-29 cells, but not in CACO-2 cells, in response to M1 CM treatment. However, small interfering RNA (siRNA) knockdown of p21 had no effect on the M1 CM induced cell cycle arrest seen in HT-29 and neither did it change the growth recovery after combined treatment of HT-29 cells with M1 CM and 5-FU. In conclusion, treatment of HT-29 cells with M1 CM reduces the cytotoxic effect of 5-FU and this is mediated by a M1 CM induced cell cycle arrest in the G₀/G₁ and G₂/M phases. So far, we lack an explanation why this action is absent in the CACO-2 cells. The current findings may be important for optimization of chemotherapy in colon cancer.

Reconfigurable microfluidic hanging drop network for multi-tissue interaction and analysis

Integration of multiple three-dimensional microtissues into microfluidic networks enables new insights in how different organs or tissues of an organism interact. Here, we present a platform that extends the hanging-drop technology, used for multi-cellular spheroid formation, to multifunctional complex microfluidic networks. Engineered as completely open, 'hanging' microfluidic system at the bottom of a substrate, the platform features high flexibility in microtissue arrangements and interconnections, while fabrication is simple and operation robust. Multiple spheroids of different cell types are formed in parallel on the same platform; the different tissues are then connected in physiological order for multi-tissue experiments through reconfiguration of the fluidic network. Liquid flow is precisely controlled through the hanging drops, which enable nutrient supply, substance dosage and inter-organ metabolic communication. The possibility to perform parallelized microtissue formation on the same chip that is subsequently used for complex multi-tissue experiments renders the developed platform a promising technology for 'body-on-a-chip'-related research.

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 is both a therapeutic and a suicide gene in a murine model of mitochondrial neurogastrointestinal encephalomyopathy

Suicide gene therapy (SGT) is a promising strategy for treating cancer. In this work, we show that thymidine phosphorylase (TP) deficiency, the underlying genetic defect in mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), presents an opportunity to apply SGT using capecitabine, a commonly used prodrug that is converted into 5-fluorouracil by TP. Using an immortalised B-lymphoblastoid cell line from a patient with MNGIE, the tumourigenic EL-4 cell line, lentiviral vectors encoding TP and a double knockout (Tymp(-/-)Upp1(-/-)) murine model, we found that EL-4 cell-derived TP(+) tumours were exquisitely sensitive to capecitabine and generated a significant local bystander effect. In addition, we detected a spontaneous cytolytic immune response in a significant fraction of the animals surviving more than 20 days after termination of the therapy. These data indicate that, in individuals lacking TP expression, TP is a highly specific suicide gene, which can be used to treat tumours that could hypothetically arise in MNGIE patients undergoing gene therapy, as these tumours will likely originate from the gene-modified cells and will be selectively targeted by capecitabine. These observations have important implications for gene therapy for MNGIE.

Association of right-sided tumors with high thymidine phosphorylase gene expression levels and the response to oral uracil and tegafur/leucovorin chemotherapy among patients with colorectal cancer

PURPOSE

To identify useful predictive factors for the response to 5-fluorouracil (5-FU)/leucovorin (LV) and oral uracil and tegafur (UFT)/LV chemotherapy among patients with colorectal cancer, we investigated the association between the gene expression levels of pyrimidine and folate metabolism-related enzymes in colorectal cancer (CRC) tissues and the response to UFT/LV neoadjuvant chemotherapy.

METHODS

The subjects were 76 CRC patients who were scheduled to undergo surgery. UFT (300 mg/m(2)/day) and LV (75 mg/body/day) were administered for 2 weeks before surgery. Biopsy samples were endoscopically obtained before drug administration. The gene expression levels of 14 genes in the biopsy samples were quantitatively evaluated using a real-time polymerase chain reaction (RT-PCR) assay.

RESULTS

Fifteen patients (19.7 %) with marked pathological regression were judged to be responders. Thymidine phosphorylase (TP) gene expression levels among the responders were significantly higher than those among the non-responders. Right-sided tumors with high TP gene expression levels were associated with a significantly higher response rate to UFT/LV chemotherapy than left-sided tumors.

CONCLUSIONS

TP gene expression levels in primary CRC tissues and the primary tumor site may be useful predictors of the efficacy of oral UFT/LV chemotherapy.

Substrate/Product-targeted NMR monitoring of pyrimidine catabolism and its inhibition by a clinical drug

We report the application of one-dimensional triple-resonance NMR to metabolic analysis and thereon-based evaluation of drug activity. Doubly (13)C/(15)N-labeled uracil ([(15)N1,(13)C6]-uracil) was prepared. Its catabolic (degradative) conversion to [(13)C3,(15)N4]-β-alanine and inhibition thereof by gimeracil, a clinical co-drug used with the antitumor agent 5-fluorouracil, in mouse liver lysates were monitored specifically using one-dimensional triple-resonance ((1)H-{(13)C-(15)N}) NMR, but not double-resonance ((1)H-{(13)C}) NMR, in a ratiometric manner. The administration of labeled uracil to a mouse resulted in its non-selective distribution in various organs, with efficient catabolism to labeled β-alanine exclusively in the liver. The co-administration of gimeracil inhibited the catabolic conversion of uracil in the liver. In marked contrast to in vitro results, however, gimeracil had practically no effect on the level of uracil in the liver. The potentiality of triple-resonance NMR in the analysis of in vivo pharmaceutical activity of drugs targeting particular metabolic reactions is discussed.

Epigenetics and chemoresistance in colorectal cancer: an opportunity for treatment tailoring and novel therapeutic strategies

Colorectal cancer is the second leading cause of cancer-related deaths in the world. Despite many therapeutic opportunities, prognosis remains dismal for patients with metastatic disease, and a significant portion of early-stage patients develop recurrence after chemotherapy. Epigenetic gene regulation is a major mechanism of cancer initiation and progression, through the inactivation of several tumor suppressor genes. Emerging evidence indicates that epigenetics may also play a key role in the development of chemoresistance. In the present review, we summarize epigenetic mechanisms triggering resistance to three commonly used agents in colorectal cancer: 5-fluorouracil, irinotecan and oxaliplatin. Those epigenetic biomarkers may help stratify colorectal cancer patients and develop a tailored therapeutic approach. In addition, epigenetic modifications are reversible through specific drugs: histone-deacetylase and DNA-methyl-transferase inhibitors. Preclinical studies suggest that these drugs may reverse chemoresistance in colorectal tumors. In conclusion, an epigenetic approach to colorectal cancer chemoresistance may pave the way to personalized treatment and to innovative therapeutic strategies.

The therapeutic efficacy of S-1 against orthotopically implanted human pleural mesothelioma cells in severe combined immunodeficient mice

Purpose

Malignant pleural mesothelioma (MPM) is a highly lethal neoplasm. S-1 has been developed as a novel oral antineoplastic agent based on the modulation of 5-fluorouracil (5-FU) bioactivity. This study was conducted to investigate the preclinical therapeutic effect of S-1 on MPM.

Methods

We used three human MPM cell lines, Y-MESO-14, NCI-H290 and MSTO-211H. In vitro proliferation of human MPM cells was determined by MTT assay. Human MPM cells were orthotopically implanted into thoracic cavity of SCID mice. Tumor-bearing mice were treated with S-1 or vehicle.

Results

The combination of 5-FU and 5-chloro-2,4-dihydroxypyridine (CDHP) was more effective than 5-FU alone in inhibiting MPM cell proliferation in vitro. This combination was most effective in Y-MESO-14 cells, which co-expressed high protein level of dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP). In vivo data showed that treatment with S-1 significantly reduced thoracic tumors and pleural effusion produced by Y-MESO-14 cells. Moreover, treatment with S-1 prolonged the survival of Y-MESO-14 cell-bearing SCID mice.

Conclusions

We demonstrated that S-1 was effective for inhibiting the proliferation of MPM cells, particularly with both DPD and TP expressions, suggesting that S-1 might be therapeutically effective for control of MPM.

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.

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.

Radiation- and photo-induced activation of 5-fluorouracil prodrugs as a strategy for the selective treatment of solid tumors

5-Fluorouracil (5-FU) is used widely as an anticancer drug to treat solid cancers, such as colon, breast, rectal, and pancreatic cancers, although its clinical application is limited because 5-FU has gastrointestinal and hematological toxicity. Many groups are searching for prodrugs with functions that are tumor selective in their delivery and can be activated to improve the clinical utility of 5-FU as an important cancer chemotherapeutic agent. UV and ionizing radiation can cause chemical reactions in a localized area of the body, and these have been applied in the development of site-specific drug activation and sensitization. In this review, we describe recent progress in the development of novel 5-FU prodrugs that are activated site specifically by UV light and ionizing radiation in the tumor microenvironment. We also discuss the chemical mechanisms underlying this activation.

The cytostatic activity of pyrimidine nucleosides is strongly modulated by Mycoplasma hyorhinis infection: Implications for cancer therapy

Nucleoside analogues are widely used as chemotherapeutic agents in the treatment of cancer. Several cancers are reported to be associated with mycoplasmas (i.e. Mycoplasma hyorhinis), which contain a number of nucleoside-metabolizing enzymes. Pyrimidine nucleoside analogues, such as 5-fluoro-2'-deoxyuridine (FdUrd), 5-trifluorothymidine (TFT) and 5-halogenated 2'-deoxyuridines can be degraded by thymidine phosphorylase (TP) to their inactive bases. We found in M. hyorhinis-infected MCF-7 breast carcinoma cells (MCF-7/HYOR) a mycoplasma-encoded TP that dramatically (20-150-fold) reduces the cytostatic activity of these compounds. The reduction in cytostatic activity could be fully restored in the presence of TPI (5-chloro-6-[1-(2-iminopyrrolidinyl)methyl]uracil hydrochloride), a known inhibitor of human TP. This observation is in agreement with the markedly decreased formation of active metabolite (i.e. FdUMP for FdUrd) or diminished drug incorporation into nucleic acids (i.e. for TFT and 5-bromo-2'-deoxyuridine) in MCF-7/HYOR cells compared with uninfected MCF-7 cells. Antimetabolite formation is fully restored in the presence of TPI. In contrast, 5-fluoro-5'-deoxyuridine (5'DFUR), an intermediate metabolite of capecitabine, was markedly more cytostatic in MCF-7/HYOR cells than in uninfected cells, due to the activation of this prodrug by the mycoplasma-encoded TP. Thus, our data reveal that M. hyorhinis expresses a TP that activates 5'DFUR but inactivates FdUrd, TFT and 5-halogenated 2'-deoxyuridines, and that is highly sensitive to the inhibitory effect of the TP inhibitor TPI. Given the association of M. hyorhinis with several human cancers, our findings suggest that pyrimidine nucleoside-based but not 5FU-based anti-cancer therapy might be more effective when combined with a mycoplasmal TP inhibitor.

Breast tumour angiogenesis

The central importance of tumour neovascularization has been emphasized by clinical trials using antiangiogenic therapy in breast cancer. This review gives a background to breast tumour neovascularization in in situ and invasive breast cancer, outlines the mechanisms by which this is achieved and discusses the influence of the microenvironment, focusing on hypoxia. The regulation of angiogenesis and the antivascular agents that are used in an antiangiogenic dosing schedule, both novel and conventional, are also summarized.

In vitro and in vivo reversal of resistance to 5-fluorouracil in colorectal cancer cells with a novel stealth double-liposomal formulation

Drug resistance is a major cause of treatment failure in cancer chemotherapy, including that with the extensively prescribed antimetabolite, 5-fluorouracil (5-FU). In this study, we tried to reverse 5-FU resistance by using a double-punch strategy: combining 5-FU with a biochemical modulator to improve its tumoural activation and encapsulating both these agents in one same stealth liposome. Experiments carried out in the highly resistant, canonical SW620 human colorectal model showed a up to 80% sensitisation to 5-FU when these cells were treated with our liposomal formulation. Results with this formulation demonstrated 30% higher tumoural drug uptake, better activation with increased active metabolites including critical-5-fluoro-2-deoxyuridine-5-monophosphate, superior inhibition (98%) of tumour thymidylate synthase, and subsequently, higher induction of both early and late apoptosis. Drug monitoring showed that higher and sustained exposure was achieved in rats treated with liposomal formulation. When examined in a xenograft animal model, our dual-agent liposomal formulation caused a 74% reduction in tumour size with a mean doubling in survival time, whereas standard 5-FU failed to exhibit significant antiproliferative activity as well as to increase the lifespan of tumour-bearing mice. Taken collectively, our data suggest that resistance to 5-FU can be overcome through a better control of its intratumoural activation and the use of an encapsulated formulation.

Combined intra-arterial 5-fluorouracil and subcutaneous interferon-alpha therapy for highly advanced hepatocellular carcinoma

Because of the difficulties of low sensitivity for anticancer agents and giving sufficient dose because of poor liver function, chemotherapy may not play a central role for treatment of hepatocellular carcinoma (HCC) patients, especially those with liver cirrhosis. However, chemotherapy must be one of the important possibilities of multimodal treatment for advanced HCC, for which hepatic resection, percutaneous ablation, transcatheter arterial embolization and other general therapies would not be effective or even possible. Also, intra-arterial perfusion chemotherapy is a common therapy for HCC and it is not difficult to maintain; but the effective rate is not sufficient. Recently, the combination therapy of s.c. interferon (IFN)-alpha and intra-arterial 5-fluorouracil (5-FU) showed an outstandingly effective rate for intractable HCC (with portal vein thrombosis). In addition,recent preclinical and clinical studies have revealed that the mechanism of combination therapy may concern direct antitumor effects (through cell-cycle arrest and induction of apoptosis) and indirect actions (through immunocompetent cells and anti-angiogenic effect). For the further advance of HCC treatment and prognosis, this therapy might be a promising treatment modality and is expected to develop. In this review, we summarize recent clinical and preclinical data regarding IFN-alpha and 5-FU combination therapy and discuss the further prospects of this therapy.

Genetic and biochemical modulation of 5-fluorouracil through the overexpression of thymidine kinase: an in-vitro study

The pro-drug 5-fluorouracil (5-FU) exerts its anti-proliferative action after conversion into cytotoxic metabolites. We previously demonstrated that the anti-cancer action of 5-FU could be enhanced by boosting thymidine phosphorylase (TP) activity in cancer cells, the first step of the DNA pathway, that yields the critical anti-thymidylate synthase (TS) fluorodeoxyuridine monophosphate (FdUMP) metabolite. In the present study, we further studied to what extent 5-FU activity could be optimized by overexpressing cancer cell thymidine kinase (TK), the second step of the DNA pathway, for which controversial data have been published so far. Additionally, screening of biochemical modulators likely to contribute to 5-FU activation was also carried out. TK-overexpressing colorectal cells were obtained after designing vectors harboring viral and human cDNA, and performing stable transfection in the human HT29 cell line. Anti-proliferative assays were subsequently performed so as to evaluate change in cell sensitivity to 5-FU, and metabolism monitoring was carried out to follow drug activation and FdUMP formation after cellular uptake. Finally, TS inhibition was assessed as a pharmacological endpoint. Results showed that overexpression of TK led to a marked desensitization of our model. A negative correlation (r = 0.87) was found between the level of TK activity and 5-FU anti-proliferative action - the higher the activity, the lower the sensitivity. Of the various drugs screened as putative modulators, only those involved in TP activity proved to enhance 5-FU efficacy via optimized FdUMP formation. Conversely, genetically increasing TK activity did not modify 5-FU activation pathway nor subsequent TS inhibition in our model. Therefore, our results indicate that TK is not a limiting step in the production of anti-TS FdUMP and that tumor cells overexpressing TK are likely to resist 5-FU-based chemotherapies.

Predictive role of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase expression in colorectal cancer patients receiving adjuvant 5-fluorouracil

OBJECTIVE

The combined assessment of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) gene expressions in metastatic colorectal cancer has been reported to be able to predict the efficacy of fluoropyrimidine-based chemotherapy. In order to evaluate the prognostic role in the adjuvant setting, we investigated the TS, DPD and TP expression in primary tumors of colorectal cancer patients treated with 5-fluorouracil (5-FU).

METHODS

TS, DPD and TP expression levels were determined by immunohistochemistry in paraffin-embedded primary tumor tissues from 62 patients with Dukes' stage B and C colorectal cancers who underwent surgery and received adjuvant systemic chemotherapy with 5-FU. The median follow-up was 90 months (range 17-127).

RESULTS

Dukes' stage C cancer and high TS expression were independent markers of poor prognosis for disease-free survival (DFS; p = 0.0009 and p = 0.007, respectively) and overall survival (OS; p = 0.0005 and p = 0.011, respectively). By multivariate analysis, patients with high DPD expression had significantly shorter DFS (p = 0.007) and OS (p = 0.005) compared to patients with low DPD expression. In the combined analysis of 2 markers, patients with low TS and low DPD had the best outcome in terms of DFS (p = 0.007) and OS (p = 0.03). The analysis of all 3 proteins showed that the patients with low expression of all 3 markers had significantly longer DFS (p = 0.04) and OS (p = 0.01) than patients with a high value of any one of the protein expressions. However, the joint analysis of 3 markers (group with TS-/DPD-/TP-) could not identify a subgroup of patients with a better prognosis compared to the analysis of 2 markers (group with TS-/DPD-). The analysis of Dukes' stage C cancer patients confirmed a significant benefit in terms of DFS and OS (p = 0.001 and p = 0.006, respectively) when all 3 markers had low expression. We also found a positive significant correlation between TS and TP protein expression (p = 0.033).

CONCLUSIONS

This retrospective investigation suggests that the combined assessment of TS and DPD may be useful to evaluate the prognosis of patients with Dukes' B and C colon carcinoma receiving 5-FU adjuvant chemotherapy. The role of TP as a predictor for 5-FU-based therapy needs further investigations.

Development of stealth liposome formulation of 2'-deoxyinosine as 5-fluorouracil modulator: in vitro and in vivo study

PURPOSE

The aims of this study were to develop a stealth, pegylated liposomal formulation of 2'-deoxyinosine (d-Ino), a 5-fluorouracil (5-FU) modulator, to evaluate its efficacy in vitro and in tumor-bearing mice, and to study its pharmacokinetics in rats.

METHOD

After designing a pegylated liposome encapsulating d-Ino (L-d-Ino), we evaluated its efficacy as 5-FU modulator in vitro. Antiproliferative assays, thymidylate synthase (TS) inhibition, and apoptosis studies were carried out to check whether an optimization of 5-FU action was achieved on the 5-FU-resistant SW620 cell line. Animal pharmacokinetic and ex vivo studies were next performed to confirm that L-d-Ino displayed a slower plasma elimination pattern than free d-Ino. Finally, effects on tumor growth of L-d-Ino + 5-FU combination was evaluated in xenografted mice.

RESULTS

We developed a stable, sterile, and homogenous 100-nm population of pegylated liposomes encapsulating 30% of d-Ino. Liposomal d-Ino exhibited a strong potential as 5-FU modulator in vitro by enhancing TS inhibition and subsequent apoptosis induction, while displaying a better pharmacokinetic profile in animals, with a near seven times clearance reduction as compared with the free form. When used in tumor-bearing mice in combination with 5-FU, our results showed next that the association led to 70% of tumor reduction with a doubling median survival time as compared with untreated animals, whereas 5-FU alone was ineffective.

CONCLUSION

Our data show that liposomal d-Ino, through an optimized pharmacokinetic profile, displays a potent effect as fluoropyrimidines modulator, both in vitro and in xenografted mice. Besides, we showed here that it is possible to reverse a resistant phenotype to 5-FU, a major drug extensively described in clinical oncology.

Genetic factors influencing pyrimidine-antagonist chemotherapy

Pyrimidine antagonists, for example, 5-fluorouracil (5-FU), cytarabine (ara-C) and gemcitabine (dFdC), are widely used in chemotherapy regimes for colorectal, breast, head and neck, non-small-cell lung cancer, pancreatic cancer and leukaemias. Extensive metabolism is a prerequisite for conversion of these pyrimidine prodrugs into active compounds. Interindividual variation in the activity of metabolising enzymes can affect the extent of prodrug activation and, as a result, act on the efficacy of chemotherapy treatment. Genetic factors at least partly explain interindividual variation in antitumour efficacy and toxicity of pyrimidine antagonists. In this review, proteins relevant for the efficacy and toxicity of pyrimidine antagonists will be summarised. In addition, the role of germline polymorphisms, tumour-specific somatic mutations and protein expression levels in the metabolic pathways and clinical pharmacology of these drugs are described. Germline polymorphisms of uridine monophosphate kinase (UMPK), orotate phosphoribosyl transferase (OPRT), thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and methylene tetrahydrofolate reductase (MTHFR) and gene expression levels of OPRT, UMPK, TS, DPD, uridine phosphorylase, uridine kinase, thymidine phosphorylase, thymidine kinase, deoxyuridine triphosphate nucleotide hydrolase are discussed in relation to 5-FU efficacy. Cytidine deaminase (CDD) and 5'-nucleotidase (5NT) gene polymorphisms and CDD, 5NT, deoxycytidine kinase and MRP5 gene expression levels and their potential relation to dFdC and ara-C cytotoxicity are reviewed.

Re-evaluation of antitumor effects of combination chemotherapy with interferon-α and 5-fluorouracil for advanced hepatocellular carcinoma

AIM: To evaluate the efficacy of combination chemotherapy with interferon-α (IFN α ) and 5-fluorouracil (5-FU) in patients with advanced hepatocellular carcinoma (HCC).

METHODS: Twenty-eight HCC patients in advanced stage were enrolled in the study. They were treated with IFNα / 5-FU combination chemotherapy. One cycle of therapy lasted for 4 wk. IFNα (3×10⁶ units) was subcutaneously injected thrice weekly on days 1, 3, and 5 for 3 wk, and 5-FU (500 mg/d) was administered via the proper hepatic artery for 5 consecutive days per week for 3 wk. No drugs were administered during the 4^th wk. The effect of combination chemotherapy was evaluated in each patient after every cycle based on the reduction of tumor volume.

RESULTS: After the 1^st cycle of therapy, 16 patients showed a partial response (PR, 57.1%) but none showed a complete response (CR, 0%). At the end of therapy, the number of patients who showed a CR, PR, or no response (NR) was 1, 10, and 17, respectively. The response rate for therapy (CR+PR) was 21.5%. Biochemical tests before therapy were compared between responsive (CR+PR) and non-responsive (NR) patients, but no significant differences were found for any of the parameters examined, indicating that no reasonable predictors could be identified in our analysis.

CONCLUSION: Attempts should be made to discriminate between responders and non-responders by evaluating tumor size after the first cycle of IFNα /5-FU combination chemotherapy. For non-responders, therapy should not proceed to the next cycle, and instead, different combination of anticancer drugs should be explored.

Interferons upregulate thymidine phosphorylase expression via JAK-STAT-dependent transcriptional activation and mRNA stabilization in human glioblastoma cells

Overexpression of the angiogenic enzyme thymidine phosphorylase (TP) in tumor cells and/or infiltrating macrophages correlates with increased microvessel density and poor prognosis in various tumor types including glioma. The present study examined how the TP gene expression is regulated by different types of interferons (IFNs) in human T98G and A172 glioblastoma cells. Both type I (alpha, beta) and type II (gamma) IFNs upregulated TP mRNA and protein expression while inhibiting cell proliferation. IFN-induced TP mRNA accumulation was not inhibited by the protein synthesis inhibitor cycloheximide, but was strongly blocked by the transcription inhibitor actinomycin D, as well as by transcription factor decoy oligodeoxynucleotides containing the putative IFN response element or the gamma-activated sequence in the TP promoter. The Janus kinase (JAK) inhibitor AG-490 blocked both IFN-induced STAT1 (signal transducers and activators of transcription 1) phosphorylation and TP expression. All IFNs increased the stability of TP mRNA as well. In addition, IFN-evoked TP enzyme activity enhanced the cytotoxicity of 5-fluorouracil (5-FU). These findings indicate that TP expression may be upregulated by IFNs via the JAK-STAT signaling pathway and both transcriptional and posttranscriptional mechanisms. Combined treatment with IFN and 5-fluorouracil may be a useful therapeutic strategy for malignant gliomas.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Consensus interferon enhances the anti-proliferative effect of 5-fluorouracil on human hepatoma cells via downregulation of dihydropyrimidine dehydrogenase expression

BACKGROUND/AIMS

The effectiveness of 5-fluorouracil (5-FU) treatment is influenced by the activities of pyrimidine catabolic enzymes. The aim of this study was to investigate whether interferon (IFN)-alpha influences expression of 5-FU catabolic or target-related enzymes in human hepatoma cells.

METHODS

HepG2 cells were treated with 0, 0.15, 1.5, 15, and 150 ng/ml of consensus interferon (C-IFN). Expression of mRNAs encoding dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase, and thymidylate synthase was examined by reverse transcription-polymerase chain reaction before and after C-IFN treatment. To determine the effect of pretreatment with C-IFN on 5-FU+C-IFN combination therapy, we performed WST-1 cell proliferation assays.

RESULTS

A significant reduction in the level of DPD mRNA was observed when HepG2 cells were pretreated with C-IFN (P<0.05). This reduction occurred in a time-dependent manner. Cell proliferation was reduced most significantly when HepG2 cells were treated with 5-FU and C-IFN. Furthermore, when cells were pretreated with C-IFN for 3 days, the anti-proliferative effect of 5-FU+C-IFN combination therapy was augmented significantly (P<0.05).

CONCLUSIONS

C-IFN likely improves the anti-tumor effect of 5-FU via downregulation of DPD enzyme in hepatoma cells. Pretreatment with C-IFN may increase the anti-cancer effect of 5-FU+C-IFN combination therapy.

Customizing chemotherapy for colon cancer: the potential of gene expression profiling

The value of gene expression profiling, or microarray analysis, for the classification and prognosis of multiple forms of cancer is now clearly established. For colon cancer, expression profiling can readily discriminate between normal and tumor tissue, and to some extent between tumors of different histopathological stage and prognosis. While a definitive in vivo study demonstrating the potential of this methodology for predicting response to chemotherapy is presently lacking, the ability of microarrays to distinguish other subtleties of colon cancer phenotype, as well as recent in vitro proof-of-principle experiments utilizing colon cancer cell lines, illustrate the potential of this methodology for predicting the probability of response to specific chemotherapeutic agents. This review discusses some of the recent advances in the use of microarray analysis for understanding and distinguishing colon cancer subtypes, and attempts to identify challenges that need to be overcome in order to achieve the goal of using gene expression profiling for customizing chemotherapy in colon cancer.

Comparative Antitumor Activity of 5-Fluorouracil and 5’-Deoxy-5-Fluorouridine in Combination with Interferon-α in Renal Cell Carcinoma Cell Lines

OBJECTIVES

Although interferon-alpha (IFNalpha) and interleukin-2 are used in the treatment of advanced renal cell carcinoma (RCC), the rate of efficacy is about 15% and not satisfactory. Therefore, a more effective treatment is being investigated. In this study, we examined the combined effects of IFNalpha and 5-fluorouracil (5-FU) as well as 5-deoxy-5-fluorouridine (5'-DFUR), a produrg of 5-FU, in vitro.

MATERIALS AND METHODS

Four RCC cell lines (OCUU1, OCUU3, OCUU4, OCUU5) were established at our laboratory from RCC patients. OS-RC-2, RCC10RGB, TUHR14TKB, TUHR4TKB, A498 and Caki-1 were obtained from a commercial source. The sensitivity of the 10 RCC cell lines to 5-FU and 5'-DFUR was evaluated using MTT assay. The IC50 value for the cytostatics was expressed as the concentration at which growth was inhibited by 50% as compared with the control value. Thymidine phosphorylase (TP), the enzyme that converts 5'-DFUR into 5-FU and 5-FU into FdUMP, was estimated by ELISA.

RESULTS

When the 10 RCC cell lines were divided into the low TP expression group and high TP expression group at 2.0 U/ml protein, TP expression was not enhanced by IFNalpha in all 4 cell lines in the low TP expression group. Antitumor effects were not enhanced by IFNalpha in 3 out of 4 cell lines for 5-FU and in all 4 cell lines for 5'-DFUR. On the other hand, in the high TP expression group, TP expression was enhanced by IFNalpha in 5 out of 6 cell lines, and antitumor effects were enhanced by IFNalpha in 5 out of 6 cell lines for 5-FU and in all 6 cell lines for 5'-DFUR. In addition, there was a significant correlation between TP expression and sensitivity to 5-FU and 5'-DFUR in all RCC cell lines.

CONCLUSIONS

These results suggested that TP may be useful as a predictive factor in combination therapy with IFNalpha and 5-FU or 5'-DFUR, which may be a promising treatment for advanced RCC.

Identification of a novel human uridine phosphorylase

Uridine phosphorylase catalyzes the reversible phosphorylytic cleavage of uridine and deoxyuridine to uracil and ribose- or deoxyribose-1-phosphate. The enzyme has an important role in the metabolism of pyrimidine analogs used in cancer chemotherapy. The cDNA of a novel 317 amino acid human uridine phosphorylase approximately 60% identical to the previously identified human uridine phosphorylase was cloned. The novel enzyme, named uridine phosphorylase-2 (UPase-2), showed broad substrate specificity and accepted uridine, deoxyuridine, and thymidine as well as the two pyrimidine nucleoside analogs 5-fluorouridine and 5-fluoro-2(')-deoxyuridine. The human UPase-2 gene was mapped to chromosome 2q24.1 and the 2.2-kb mRNA was predominantly expressed in kidney. The mouse UPase-2 cDNA was also identified and shown to be predominantly expressed in liver. The identification of a novel uridine phosphorylase with broad substrate specificity is important for studies on both nucleoside metabolism as well as for studies on the pharmacological mechanisms of therapeutic pyrimidine nucleoside analogs.

Penetration of capecitabine and its metabolites into malignant and healthy tissues of patients with advanced breast cancer

Capecitabine is an oral prodrug of 5-fluorouracil (FU). Since FU concentrations achieved in malignant lesions are an important determinant of efficacy, we investigated the intratumoral transcapillary transfer of capecitabine and its metabolites in vivo. A total of 10 patients with skin metastases from breast cancer received a daily dose of 2500 mg m(-2) capecitabine administered orally in two divided doses for 2 weeks. Microdialysis probes were inserted into a cutaneous metastasis and subcutaneous connective tissue to evaluate the interstitial tissue pharmacokinetics of capecitabine and its metabolites 5'-deoxy-5-fluorocytidine (DFCR), 5'-deoxy-5-fluorouridine (DFUR), and FU by capillary electrophoresis. As intended with the prodrug design of capecitabine, FU was present in low concentrations in tumour interstitium (median c(max): 0.26 microg ml(-1)) when compared with capecitabine, DFCR, and DFUR (median c(max): 2.66, 4.22, and 2.13 microg ml(-1), respectively). Capecitabine and its metabolites easily penetrated malignant and healthy tissue and equilibrated within 45 min between plasma and tissue interstitium. Considering tissue exposure at the extracellular level, no significant differences between healthy and malignant tissues were observed. Our data show that absorption and metabolism determined the tissue pharmacokinetics of capecitabine. There was no evidence of drug tolerance, which may be attributed to impaired transcapillary transfer into tissue, even after repeated administration as shown for three patients.

Thymidine phosphorylase and dihydropyrimidine dehydrogenase in renal cell carcinoma: relationship between histological parameters and chemosensitivity to 5-fluorouracil

OBJECTIVES

Thymidine phosphorylase (TdR-Pase) and dihydropyrimidine dehydrogenase (DPD) are thought to be key enzymes in the metabolic pathway of 5-fluorouracil (5-FU). Theoretically, cancer cells which have high TdR-Pase activity and/or low DPD activity should be sensitive to 5-FU. TdR-Pase is also known to have angiogenic activity which helps tumor progression and metastasis. On the other hand, little is known concerning the relationship of DPD activity with clinical malignant potential in renal cell carcinoma (RCC). In this study, we measured both TdR-Pase and DPD activities in surgically obtained RCC tissues and examined the relationship between these enzymatic activities and histological parameters. In addition, the results of in vitro chemosensitivity testing were also analyzed to determine whether TdR-Pase and/or DPD activity in carcinoma cells can predict the efficacy of 5-FU.

METHODS

RCC tissues from 53 patients were obtained. TdR-Pase and DPD activities were measured by ELISA and radioenzyme assay, respectively. Sensitivity to 5-FU was assessed by histoculture drug response assay (HDRA), an in vitro chemosensitivity test, for 20 of the 53 specimens.

RESULTS

Both TdR-Pase and DPD activities of RCC increased with histological grade. There was a significant positive correlation between the TdR-Pase activity and 5-FU sensitivity. In addition, a stronger positive correlation was found between TdR-Pase / DPD ratio and 5-FU sensitivity. DPD exhibited no correlation with 5-FU sensitivity.

CONCLUSIONS

The activity of both enzymes increased with malignant potential of RCC. TdR-Pase appeared to be the enzyme regulating activation of 5-FU in RCC.

Induction of thymidine phosphorylase by interferon and taxanes occurs only in human cancer cells with low thymidine phosphorylase activity

Thymidine phosphorylase (TP) regulates intracellular thymidine metabolism. It has been reported to be a prognostic factor for tumor angiogenesis and to activate some prodrugs of 5-fluorouracil (5-FU) to 5-FU. There is also evidence that TP is induced by interferons (IFNs) and xenobiotics, such as cyclophosphamide and taxanes, in experimental human cancer cells and xenografts. We investigated the induction of TP expression by IFNalpha and Paclitaxel in vitro and in vivo in human tumor cells with low and with high TP activity. TP activity in KB, NUGC-3, and KOC2S cells, which had low TP activity, was increased 2 to 4 fold by IFNalpha, but was still lower than in non-treated SHIN-3 and HRA cells, which have high TP activity. IFNalpha did not promote TP activity in SHIN-3 and HRA cells, but expression of TP mRNA increased 2 to 4 fold in response to IFNalpha in all cells tested. These results suggest that the expression of TP protein would be regulated post-transcriptionally by another factor after IFN-induced amplification of TP mRNA. A single dose of Paclitaxel to nude mice xenografted with KB and KM20C tumors, expressing low TP activity, increased TP activity about 4 to 7 fold compared to non-treated tumors. In contrast, TP expression in MX-1 and H-31 tumors was originally high and did not change by the treatment of Paclitaxel. The activities of uridine phosphorylase in all tumors used showed no changes in response to IFNalpha or Paclitaxel. We determined the level of STAT1alpha, an IFN-inducible transcription factor of the TP gene, and found that it was low in low TP expressing tumor cells and markedly increased to about 4 fold by IFN, almost reaching the level in high TP expressing cells whose STAT1alpha level was unchanged by IFN. When TP activity and STAT1alpha expression in clinically resected colorectal cancers were simultaneously measured, almost all tumors had high expression of both TP and STAT1alpha. In conclusion, our results suggest that IFN and Paclitaxel affect human cancer cells with low TP activity but not those with high TP activity and that the STAT1alpha expression may reflect TP activity, at least in experimental human cancer cells.

The Sp1 transcription factor contributes to the tumor necrosis factor-induced expression of the angiogenic factor thymidine phosphorylase in human colon carcinoma cells

Thymidine phosphorylase (TP; also known as platelet-derived endothelial cell growth factor, PD-ECGF) is an angiogenic factor that is chemotactic for endothelial cells and has been found to induce neovascularization in vivo. TP is frequently overexpressed in human solid tumors, where its expression has been correlated with increased tumor microvessel density, invasion, and metastasis, and shorter patient survival. In this report, TP activity in the WiDr colon carcinoma cell line was found to be induced 100-fold by tumor necrosis factor (TNFalpha), a secretory product of activated macrophages that has indirect angiogenic activities. Increased TP activity was accompanied by increased TP mRNA levels and without an increase in mRNA stability. TNFalpha-induced TP mRNA levels were reduced by mithramycin, a DNA-binding transcription inhibitor specific for GC-rich sequences. Transcriptional regulation by TNFalpha was confirmed by transient transfection of WiDr with upstream TP sequences in a luciferase reporter construct. Deletion analysis of the reporter pinpointed two regions of the TP promoter with regulatory elements for both TNFalpha-inducible and basal expression, and they contained, respectively, three and one consensus binding sites for the Sp1-family of transcription factors. One additional region contributed only to basal TP expression, and it contained three Sp1 sites. TNFalpha-induced TP expression decreased when point mutations were made in three of the four Sp1 sites postulated to contribute to both basal and TNFalpha-inducible expression. Electrophoretic mobility shift assays further demonstrated binding of nuclear Sp1 to these three sites. Sp1-binding activity was also increased in cells treated with TNFalpha. These studies establish a role for Sp1 in the regulation of expression of the angiogenic factor TP in colon cancer WiDr cells.

Thymidine phosphorylase is regulated by tamoxifen in T47D breast cancer cell line

BACKGROUND

Thymidine phosphorylase (TP) has diverse functions within cells, including increasing the sensitivity of cancer cells to cytotoxic drugs including 5-fluorouracil (5-FU) and methotrexate. However, the regulators of TP still remains largely unknown.

METHOD

In this study, we examined whether tamoxifen has specific effects on TP expression in the T47D breast cancer cell line. We studied the TP expression in the T47D cell line before and after tamoxifen treatment using Western blot analysis and ELISA.

RESULTS

We found that TP expression is significantly up-regulated in tamoxifen-treated cells compared with control.

CONCLUSIONS

Our findings suggest that tamoxifen may increase chemotherapy sensitivity through TP up-regulation for treatment regimens including doxifluridine, capecitabine, and/or methotrexate.

A pilot trial of combination cisplatin, 5-fluorouracil and interferon-alpha in the treatment of advanced esophageal carcinoma

BACKGROUND/OBJECTIVES

Based on the synergistic effect between cisplatin and 5-fluorouracil (5-FU), and between 5-FU and interferon-alpha, we conducted a trial to assess the response rate and toxicity of the combination of cisplatin, 5-FU and interferon-alpha in patients with advanced esophageal cancer.

METHODS

Patients with locally advanced or metastatic squamous cell or adenocarcinoma of the esophagus were eligible. No prior chemotherapy or interferon were allowed. Patients received cisplatin 80 mg/m(2) on day 1, 5-FU 750 mg/m(2)/day by continuous intravenous infusion for 5 days, and interferon-alpha 5 x 10(6) units/m(2)/day by subcutaneous injection on days 1-5 of each cycle. Cycles were repeated every 21 days for a total of 6 cycles.

RESULTS

Forty patients were enrolled. Median age was 57.5 years (range 30-70). 33 had squamous carcinoma and 7 adenocarcinoma; 15 were male; the locoregional metastatic ratio was 1:39; median ECOG performance status was 2 (range 1-3). Grade 3-4 toxicities were: leukopenia (9 cases), thrombocytopenia (4), electrolyte imbalance (11), febrile neutropenia (11), vomiting (5), diarrhea (4), and mucositis (11). There were 3 early deaths, most probably related to therapy. Five patients (13%) achieved a complete response and 17 (42%) achieved a partial response, yielding an overall response rate of 55%. Response rates for squamous and adeno histology were 61% and 29%, respectively. Median survival was 6.4 months.

CONCLUSION

The combination of cisplatin, 5-FU and interferon-alpha produces a high response rate in advanced squamous cell esophageal carcinoma, but with considerable toxicity. A modified combination of the above agents is presently being evaluated at our institution.

Prognostic value of thymidine phosphorylase/platelet-derived endothelial cell growth factor in advanced colorectal cancer after surgery: evaluation with a new monoclonal antibody

BACKGROUND

Thymidine phosphorylase (TP) is an essential enzyme for activation of 5-fluorouracil and its derivatives and identical to platelet-derived endothelial cell growth factor. In colorectal cancer (CRC), previous studies evaluating the relationship between TP expression and clinicopathologic features have yielded inconsistent results. These studies used monoclonal antibody 654-1, which stained CRC cells weakly. Now, a new monoclonal antibody, 1C6-203, more sensitive than 654-1, is available.

METHODS

This study included 80 patients whose CRCs were classified into stages II to IV and completely resected surgically in our institute. TP expression in CRC was evaluated by using immunohistochemical staining with 1C6-203. Relationships between TP expression and clinicopathologic variables that might have affected the patients' prognosis were evaluated. Survival curves were calculated with the Kaplan-Meier method, and differences were evaluated with log-rank test. Cox proportional hazards model was used in the univariate and multivariate survival analyses.

RESULTS

TP expression showed a positive correlation with advances in histologic differentiation (P =.025), lymph node metastasis (P =.083), lymphatic invasion (P =.049), venous invasion (P =.042), and cancer stage (P =.002). The patients' survival rates after surgery were higher (P =.0041) in those with negative TP than in those with positive TP. The overall estimated hazard ratio for death in patients with TP expression was 6.24 according to univariate analysis (P =.013). Multivariate analysis showed that TP was a significant prognostic factor adjusted for other clinicopathologic variables.

CONCLUSIONS

With a new highly sensitive monoclonal antibody to TP, the present results indicated that TP expression is associated with CRC progression and invasion and closely correlated with poor prognosis in postoperative CRC patients. Moreover, TP expression is an independent prognostic factor in CRC patients.

Prognostic value of thymidine phosphorylase expression in breast carcinoma

Thymidine phosphorylase (TP), also known as platelet-derived endothelial cell growth factor (PD-ECGF), is an enzyme that catalyzes the reversible dephosphorylation of thymidine, deoxyuridine and their analogs. TP has also angiogenic properties, although the precise mechanism by which it promotes angiogenesis is not known. We examined TP expression using immunohistochemistry (654-1 Mab) in 182 invasive breast carcinomas (67 N0 and 115 N1/2; median follow-up 78 months [range, 3-177]; 51 patients treated with adjuvant systemic cyclophosphamide, methotrexate and 5-fluorouracil [CMF] chemotherapy and 82 with tamoxifen). High TP expression was found in 142 cases (78%) and correlated with lower histologic grade and low p53 expression. No correlation was found between TP expression and vascular density. TP-positive tumors had a significant increase in both disease-free survival (DFS; p = 0.0025) and overall survival (OS; p = 0.0070) in the total cohort of patients and in the subgroups of node-positive patients and patients treated with CMF adjuvant therapy; no significant difference in either DFS or OS was observed in patients without CMF treatment. Our findings suggest that TP has little effect on tumor angiogenesis of breast carcinoma, whereas it could represent an interesting marker that could predict response to CMF chemotherapy.

Structural analyses reveal two distinct families of nucleoside phosphorylases

The reversible phosphorolysis of purine and pyrimidine nucleosides is an important biochemical reaction in the salvage pathway, which provides an alternative to the de novo purine and pyrimidine biosynthetic pathways. Structural studies in our laboratory and by others have revealed that only two folds exist that catalyse the phosphorolysis of all nucleosides, and provide the basis for defining two families of nucleoside phosphorylases. The first family (nucleoside phosphorylase-I) includes enzymes that share a common single-domain subunit, with either a trimeric or a hexameric quaternary structure, and accept a range of both purine and pyrimidine nucleoside substrates. Despite differences in substrate specificity, amino acid sequence and quaternary structure, all members of this family share a characteristic subunit topology. We have also carried out a sequence motif study that identified regions of the common subunit fold that are functionally significant in differentiating the various members of the nucleoside phosphorylase-I family. Although the substrate-binding sites are arranged similarly for all members of the nucleoside phosphorylase-I family, a comparison of the active sites from the known structures of this family indicates significant differences between the trimeric and hexameric family members. Sequence comparisons also suggest structural identity between the nucleoside phosphorylase-I family and both 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase and AMP nucleosidase. Members of the second family of nucleoside phosphorylases (nucleoside phosphorylase-II) share a common two-domain subunit fold and a dimeric quaternary structure, share a significant level of sequence identity (>30%) and are specific for pyrimidine nucleosides. Members of this second family accept both thymidine and uridine substrates in lower organisms, but are specific for thymidine in mammals and other higher organisms. A possible relationship between nucleoside phosphorylase-II and anthranilate phosphoribosyltransferase has been identified through sequence comparisons. Initial studies in our laboratory suggested that members of the nucleoside phosphorylase-II family require significant domain movements in order for catalysis to proceed. A series of recent structures has confirmed our hypothesis and provided details of these conformational changes. Structural studies of the nucleoside phosphorylases have resulted in a wealth of information that begins to address fundamental biological questions, such as how Nature makes use of the intricate relationships between structure and function, and how biological processes have evolved over time. In addition, the therapeutic potential of suppressing the nucleoside phosphorylase activity in either family of enzymes has motivated efforts to design potent inhibitors. Several research groups have synthesized a variety of nucleoside phosphorylase inhibitors that are at various stages of preclinical and clinical evaluation.

Impact of thymidine phosphorylase surexpression on fluoropyrimidine activity and on tumour angiogenesis

Tumoral thymidine phosphorylase (TP) appears to play a dual role by being involved in neoangiogenesis and by activating 5FU prodrugs at the tumoral target site. The aim of the study was to investigate more thoroughly these potential physiological and pharmacological roles of TP. A rat carcinoma cell line (PROb) was transfected with TP/PD-ECGF in order to study the effect of the overexpression of this enzyme (1) on the sensitivity of cells to 5'DFUR and 5FU in vitro and (2) on tumour growth in vivo by using a syngenic tumour model in the BDIX rat (hepatic tumours, sub-cutaneous tumours). Cytotoxic effects of 5'DFUR, and to a lesser extent those of 5FU, were enhanced in TP clones as compared to control cells: there was a highly significant correlation between TP activity and in vitro sensitivity to 5'DFUR (r2= 0.91, P = 0.0002, n = 8) and, to a lesser extent, to 5FU (r2= 0.49, P = 0.053, n = 8). The impact of TP transfection on tumour growth was relatively modest and concerned only the initial stages of tumour expansion. Staining of TP tumours for endothelial (factor VIII) cells was always higher than controls. The staining ratio (TP/controls) tended to be reduced as tumours increased in size. The stability of TP expression was checked both in vitro (TP activity measurement) and in vivo (RT-PCR determinations) and there was no loss of TP expression over time which could be advanced to explain the progressive weakening of the impact of TP overexpression on both tumour growth and neoangiogenesis.

The oral fluorinated pyrimidines

The fluorinated pyrimidines have played a major role in the treatment of many common tumors since 5-fluorouracil (5FU) was first introduced. Studies of the cellular and clinical pharmacology of 5FU have led to an improved understanding of the mechanisms of action of this agent. This knowledge has allowed the optimal and rational development of fluoropyrimidine therapy, with significant therapeutic advances in recent years. Efforts to improve the therapeutic index of 5FU have included alteration of schedule, and the addition of biochemical modulators such as folinic acid. Although protracted continuous infusion of 5FU has led to better response rates and decreased toxicity, the administration of 5FU by protracted infusion is not only costly, but also inconvenient to the patient. Furthermore it is often associated with infectious and thrombotic complications related to the required indwelling intravenous catheter. Protracted oral administration is a rational route for administering 5FU, being preferred by the patient and the pharmaco-economist. The unpredictable and low oral bioavailability of 5FU initially discouraged this form of treatment. This problem has now been overcome by the new generation of oral fluoropyrimidines. Two main strategies have been pursued: 1) The administration of an inactive prodrug of 5FU, which is absorbed intact, and subsequently converted to 5FU. Capecitabine is converted to 5FU by a 3 step enzymatic process. 2) The administration of 5FU with an inhibitor of dihydropyrimidine dehydrogenase (DPD) to minimise the erratic absorption and variable clearance of 5FU: the preparations UFT, S1, and ethinyluracil/5FU contain an oral fluoropyrimidine co-administered orally with inhibitors of this enzyme. The development and characteristics of these agents are discussed.

Predictive and prognostic markers in gastrointestinal cancers

As the roles of specific genes and their functions in cancer etiology and progression become defined, the necessity of looking at multiple genes and their interaction becomes clearer. In gastrointestinal cancer, tumor suppressor and promoter genes, cell cycle control and angiogenic factors, repair genes, and metabolic genes have been examined as they relate to prognosis and therapeutic outcomes. To date, most correlative studies for specific molecular parameters have been done retrospectively. Methodologies, sample sizes, and definitions differ. The following analysis provides a brief review of the current state of knowledge and recent research on the most commonly studied molecular markers, and the newer areas of inquiry attempting to define how to use molecular-genetic features of individual tumors as targets for more effective therapies. Consideration is given to the design of trials employing molecular targets as outcome factors.

Fluoropyrimidine sensitivity of human MCF-7 breast cancer cells stably transfected with human uridine phosphorylase

The relationship between uridine phosphorylase (UP) expression level in cancer cells and the tumour sensitivity to fluoropyrimidines is unclear. In this study, we found that UP overexpression by gene transfer, and the subsequent efficient metabolic activation of 5-fluorouracil (5-FU) by the ribonucleotide pathway, does not increase the fluoropyrimidine sensitivity of MCF-7 human cancer cells.

Molecular markers predictive of response to chemotherapy in gastrointestinal tumors

Gastrointestinal cancers account for a large amount of human tumors. Surgery is the standard treatment for localized gastrointestinal cancer, but in a large number of patients, tumors are unresectable at time of diagnosis and even when resectable, survival is often poor. Current attempts to improve these results include the use of chemotherapy in the adjuvant setting, in the advanced disease, or as neoadjuvant treatment. However, less than half the patients respond to chemotherapeutic treatments, mostly reporting important side-effects. The identification of molecular markers, such as p53, thymidylate synthase, K-ras, and others, may provide an important tool for medical oncologists in defining subsets of patients with gastrointestinal cancers more suitable to benefit from chemotherapy or from experimental therapies. The relationship between the clinical outcome to anticancer drugs and molecular markers in gastrointestinal tumors has been reviewed. Available data are promising, but most of them arise from retrospective and small studies. Well designed, prospective trials are warranted to change the target approach from a general to an individual treatment strategy.

Enhancement of sensitivity to capecitabine in human renal carcinoma cells transfected with thymidine phosphorylase cDNA

The purpose of the present study was to examine directly the role of thymidine phosphorylase (TP) in the sensitivity of renal cell carcinoma (RCC) to a novel fluoropyrimidine carbamate, capecitabine. TP cDNA-transfected RCC are used in these experiments to provide a basis for improved therapeutic benefit in chemoimmunotherapy. Human RCC line KU2 cells were transfected with pcDNA3.1/zeo(+) with or without human TP cDNA by the lipofectin method. We established a clone transfected with pcDNA3.1/zeo(+)/TP (KU2-TP15) and a clone transfected with pcDNA3.1/zeo(+) as a control (KU2-C1). TP expression levels (mean +/- SD) examined by enzyme-linked immunosorbent assay (ELISA) were 1.3 +/- 0.14 U/mg protein in KU2, 1.6 +/- 0.57 U/mg protein in KU2-C1 and 216 +/- 25.6 U/mg protein in KU2-TP15. Immunohistochemical staining of subcutaneous tumors established in Balb/c nu/nu mice showed that KU2-TP15 was strongly positive for TP expression, whereas KU2 and KU2-C1 were negative. Sensitivities in vitro to 5-fluorouracil (5FU), 5'-deoxy-5-fluorouridine (5'DFUR) and capecitabine in KU2-TP15 were significantly enhanced compared with those in KU2 or KU2-C1. A moderate but statistically significant bystander effect was observed in vitro. KU2-TP15 tumors showed significant increase in the in vivo sensitivities to 5'DFUR and capecitabine as compared with the vehicle alone while KU2-C1 tumors did not. The difference in tumor-free rate in mice bearing KU2-TP15 at 2 months after the cessation of treatment was statistically significant between the capecitabine treatment group and the controls, the 5FU treatment group and the 5'DFUR treatment group. The present study clearly provides direct evidence for the role of TP in mediating the sensitivity of RCC to capecitabine.

Thrombospondin-1 and -2 in node-negative breast cancer: correlation with angiogenic factors, p53, cathepsin D, hormone receptors and prognosis

OBJECTIVE

Thrombospondins (TSP(s)) are a multigene family of five secreted glycoproteins involved in the regulation of cell proliferation, adhesion and migration. Two members of the TSP family, namely TSP-1 and TSP-2, are also naturally occurring inhibitors of angiogenesis. The aim of the present study was to determine the prognostic significance of the determination of TSP-1 and -2 and their correlation with the angiogenic peptides vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP), as well as with other biological and clinicopathological features investigated.

METHODS

We evaluated a series of 168 women with node-negative breast cancer with a median follow-up period of 66 months, not treated with adjuvant therapy. The cytosolic levels of TSP-1 and -2 were determined in the primary tumour by a commercially available immunometric assay.

RESULTS

We found that 166 tested tumours had measurable levels of TSP-1 and -2 protein (median value 5.978, range 0.579-31.410 ng/mg of protein). On the basis of Spearman's rank correlation coefficient, a weak inverse association of TSP-1 and -2 with tumour size and cathepsin D was found. Moreover, principal component analysis on ranks evidenced a poor association between TSP-1 and -2, VEGF and TP. The results of the clinical outcome were analysed by both univariate and multivariate [for relapse-free survival (RFS) only]) Cox regression models. TSP-1 and -2 were not significant prognostic factors in univariate analysis for either RFS (p = 0.427) or overall survival (p = 0.069). To investigate the 'angiogenic balance hypothesis', bivariate analyses were performed to investigate the interactions of TSP-1 and -2 with VEGF, TP or p53, but none were included in the selected models. Finally, in multivariate analysis for RFS a baseline model, previously defined in a larger case series and inclusive of VEGF, TP and their interaction was adopted. It was highly significant (p = 0.002, Harrell c statistic value of 0.703); but when TSP-1 and -2 were added, their contribution was negligible (p = 0.731, Harrell c statistic value of 0.705).

CONCLUSIONS

The results of this study suggest that TSP-1 and -2 do not provide additional prognostic contribution to the joint effects of VEGF and TP. In the series of node-negative breast cancer patients investigated, determination of the angiogenic peptides VEGF and TP gave significant prognostic information. On the contrary, TSP-1 and -2, potential naturally occurring negative regulators of angiogenesis, lacked prognostic value.

Induction of thymidine phosphorylase as a pharmacodynamic end-point in patients with advanced carcinoma treated with 5-fluorouracil, folinic acid and interferon alpha

Thymidine phosphorylase (TP) is an essential enzyme for the biochemical activation of 5-fluorouracil (5-FU). Interferon upregulates TP in vivo, although the dose and schedule of interferon for optimal biomodulation of 5-FU is not known. In this study, TP activity was measured in peripheral blood lymphocytes (PBLs) from patients with advanced carcinoma receiving treatment with 5-FU and folinic acid. Cohorts of patients were treated with interferon alpha (IFNalpha), immediately prior to 5-FU/folinic acid, at doses of 3 MIU m(-2), 9 MIU m(-2) and 18 MIUm(-2). IFNalpha was administered on day 0 cycle two, day-1 and day 0 cycle three and day-2, day-1 and day 0 cycle four. A fourth cohort was treated with IFNalpha 9 MIU m(-2) three times per week from cycle 2 onwards. Twenty-one patients were entered into the study with 19 evaluable for response. Six patients (32%) had stable disease and 13 (68%) progressive disease. There were no grade-IV toxicities. TP activity was detected in PBLs from all patients with wide interpatient variability in constitutive TP activity prior to chemotherapy, and in response to IFNalpha. 5-FU/folinic acid alone did not induce TP activity but a single dose of IFNalpha led to upregulation of TP within 2 h of administration with a further increase by 24 h (signed rank test, P = 0.006). TP activity remained elevated for at least 13 days (signed rank test, P= 0.02). There were no significant differences in TP activity between schedules or with additional doses of IFNalpha. A single dose of IFNalpha as low as 3 MIU m(-2) can cause sustained elevation of PBL TP activity in vivo indicating that biochemical markers are important pharmacodynamic endpoints for developing optimal schedules of IFNalpha for biomodulation of 5-FU.