Role of thymidine phosphorylase and dihydropyrimidine dehydrogenase in tumour progression and sensitivity to doxifluridine in gastric cancer patients

The Impact of the Expression Level of Intratumoral Dihydropyrimidine Dehydrogenase on Chemotherapy Sensitivity and Survival of Patients in Gastric Cancer: A Meta-Analysis

The potential impact that the intratumoral expression level of dihydropyrimidine dehydrogenase (DPD) has on chemotherapy sensitivity and long-term survival for gastric cancer (GC) patients remains controversial; therefore, this study seeks to clarify this issue. Our meta-analysis was performed using Review Manager (RevMan) 5.3 software. In vitro drug sensitivity tests, correlation coefficients between sensitivity to 5-fluorouracil (5-FU), and expression levels of intratumoral DPD were used as effective indexes to analyse. Overall survival (OS) and progression-free survival (PFS) were used as endpoints for patient outcome, and hazard ratios (HRs) and 95% confidence intervals (CIs) were noted as measures of effect. There were 15 eligible studies including 1805 patients for the final analysis. The analysis revealed a statistically significant difference between the expression level of intratumoral DPD activity, DPD mRNA levels, and sensitivity to 5-FU in GC patients, with high expression levels of intratumoral DPD resulting in low sensitivity to 5-FU. However, no matter what therapeutic regimens were used, there was no significant difference for patient outcomes between high and low DPD expression groups, either in OS or in PFS. In conclusion, high levels of intratumoral DPD expression have a negative impact on sensitivity to 5-FU in GC patients, but no prognostic value for long-term survival was uncovered.

Superior antitumor activity of trastuzumab combined with capecitabine plus oxaliplatin in a human epidermal growth factor receptor 2-positive human gastric cancer xenograft model

In the treatment of human epidermal growth factor receptor 2 (HER2)-positive advanced gastric or gastroesophageal junction cancer, it has been reported that the combination of trastuzumab with capecitabine plus cisplatin, or with 5-fluorouracil (5-FU) plus cisplatin, significantly increased overall survival compared with chemotherapy alone (ToGA trial). In addition, adjuvant therapy with capecitabine plus oxaliplatin (XELOX) improved the survival of patients who received curative D2 gastrectomy (CLASSIC trial). However, the efficacy of the combination of trastuzumab with XELOX for patients with HER2-positive gastric cancer remains unknown. The aim of this study, was to investigate the efficacy of the combination of trastuzumab with XELOX in a HER2-positive human gastric cancer xenograft model. Combination treatment with these three agents (trastuzumab 20 mg/kg, capecitabine 359 mg/kg and oxaliplatin 10 mg/kg), was found to exhibit a significantly stronger antitumor activity in NCI-N87 xenografts compared with either trastuzumab or XELOX alone. In this model, treatment with trastuzumab alone or trastuzumab plus oxaliplatin enhanced the expression of thymidine phosphorylase (TP), a key enzyme in the generation of 5-FU from capecitabine in tumor tissues. In in vitro experiments, trastuzumab induced TP mRNA expression in NCI-N87 cells. In addition, NCI-N87 cells co-cultured with the natural killer (NK) cell line CD16(158V)/NK-92 exhibited increased expression of TP mRNA. When NCI-N87 cells were cultured with CD16(158V)/NK-92 cells in the presence of trastuzumab, the mRNA expression of cytokines reported to have the ability to induce TP was upregulated in tumor cells. Furthermore, a medium conditioned by CD16(158V)/NK-92 cells also upregulated the expression of TP mRNA in NCI-N87 cells. These results suggest that trastuzumab promotes TP expression, either by acting directly on NCI-N87 cells, or indirectly via a mechanism that includes trastuzumab-mediated interactions between NK and NCI-N87 cells. Therefore, the combination of trastuzumab with XELOX may be a potent therapy for HER2-positive gastric cancer.

Predictive markers of capecitabine sensitivity identified from the expression profile of pyrimidine nucleoside-metabolizing enzymes

Molecular markers predicting sensitivity to anticancer drugs are important and useful not only for selecting potential responders but also for developing new combinations. In the present study, we analyzed the difference in the sensitivity of xenograft models to capecitabine (Xeloda®), 5'-deoxy-5-fluorouridine (5'-DFUR, doxifluridine, Furtulon®) and 5-FU by comparing the mRNA levels of 12 pyrimidine nucleoside-metabolizing enzymes. Amounts of mRNA in the tumor tissues of 80 xenograft models were determined by real-time RT-PCR and mutual correlations were examined. A clustering analysis revealed that the 12 enzymes were divided into two groups; one group consisted of 8 enzymes, including orotate phosphoribosyl transferase (OPRT), TMP kinase (TMPK) and UMP kinase (UMPK), and was related to the de novo synthesis pathway for nucleotides, with mRNA expression levels showing significant mutual correlation. In the other group, 4 enzymes, including thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD), were involved in the salvage/degradation pathway of the nucleotides, and the mRNA levels of this group were dispersed more widely than that of the de novo group. Antitumor activity was assessed in 24 xenograft models for each drug. The antitumor activity of capecitabine and 5'-DFUR correlated significantly with the mRNA levels of TP and with the TP/DPD ratio, whereas the activity of 5-FU correlated significantly with OPRT, TMPK, UMPK and CD. In a stepwise regression analysis, TP and DPD were found to be independent predictive factors of sensitivity to capecitabine and 5'-DFUR, and UMPK was predictive of sensitivity to 5-FU. These results indicate that the predictive factors for sensitivity to capecitabine and 5'-DFUR in xenograft models may be different from those for 5-FU, suggesting that these drugs may have different responders in clinical usage.

The effect of chemotherapy or radiotherapy on thymidine phosphorylase and dihydropyrimidine dehydrogenase expression in cancer of the uterine cervix

OBJECTIVE

Levels of 5-FU metabolic or related enzymes, particularly thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD), have been investigated in various cancer types, including uterine cervical cancer. Intratumoral TP levels have been reported to increase in response to several chemotherapeutic agents or irradiation in both xenografts and clinical studies. In cervical cancer, however, only a few studies about changes in TP and DPD expression associated with cancer treatment have been published. We evaluated the effect of chemotherapy and/or irradiation on TP and DPD expression in cervical squamous cell carcinoma.

STUDY DESIGN

Of 27 patients in this study, 12 patients underwent neoadjuvant chemotherapy consisting of nedaplatin, ifosfamide, and/or peplomycin followed by radical surgery, and 15 patients underwent radiotherapy (n=8) or chemoradiotherapy with nedaplatin (n=7) as initial treatment. Tumor specimens were obtained from biopsies acquired before treatment and after administration of chemotherapy (2 weeks after the first and second cycles), and after irradiation with 10 Gy, 20 Gy, and 30 Gy. These specimens were used to measure TP and DPD levels by ELISA.

RESULTS

In the 12 patients who received neoadjuvant chemotherapy, intratumoral TP and DPD levels did not change. In contrast, in the 15 patients who underwent radiotherapy or chemoradiotherapy with nedaplatin, TP or DPD expression appeared to be slightly increased or decreased, respectively, after irradiation with 20 Gy, and consequently the TP/DPD ratio was significantly higher after irradiation with 20 Gy than before irradiation.

CONCLUSIONS

These results suggest a clinical advantage of chemoradiotherapy with capecitabine or doxyfluridine over radiotherapy alone via the elevation of the TP/DPD ratio in cervical squamous cell carcinoma. However, no advantage of combination chemotherapy with these 5-FU derivatives was demonstrated. Therefore, further evaluation with a larger number of patients or with other chemotherapeutic agents is required to confirm these observations.

Predicting the response to chemotherapy in gastric adenocarcinoma: who benefits from neoadjuvant chemotherapy?

Despite a decline in the overall incidence, gastric adenocarcinoma remains the second most common cause of cancer death worldwide and thus a significant global health problem. Even in early-stage locoregional confined disease the 5-year survival rarely exceeds 25-35 %. Randomized trials have demonstrated a benefit from neoadjuvant and perioperative chemotherapy. However the optimal approach in individual patients is not clear and remains controversial. A consistent finding is that patients who have a histopathological response to neoadjuvant therapy are more likely to receive a survival benefit. These clinical data provide a strong argument for the urgent development of methods to predict histopathological response to neoadjuvant therapies for gastric adenocarcinomas. Published data demonstrate that clinico-pathological features (tumour histology and location), imaging through metabolic response by FDG-PET and tissue/molecular biomarkers may all have a predictive value for neoadjuvant therapies. However it is still uncertain from published data whether or not they will be useful for clinical decision making in individual patients. Existing candidate biomarkers need to be properly qualified and validated and novel biomarkers are required and an optimal approach should involve the combination and integration of clinical, imaging, pathological and molecular biomarkers.

5-Fluorouracil pharmacogenomics: still rocking after all these years?

The 5-fluorouracil (5-FU) metabolic pathway is mainly dependent on the activity of several intracellular enzymes. Among them, four in particular; thymidylate synthase, methylenetetrahydrofolate reductase, dihydropyrimidine dehydrogenase and thymidine phosphorylase are considered the key points in determining sensitivity or resistance to this drug. These enzymes are needed to metabolize the drug in its active form (thymidylate phosphorylase) or to drop the concentration of the active drug in the cell (dihydropyrimidine dehydrogenase) or both (thymidylate synthase and methylenetetrahydrofolate reductase). Several different studies have tried to investigate the relationship between the presence of mutations in these enzymes and a reduced/improved activity of treatment based on 5-FU or its derivatives. In this article, we will focus on the often contradictory results of these studies.

Relationship between gene expression of 5-fluorouracil metabolic enzymes and 5-fluorouracil sensitivity in primary cancer cells isolated from malignant ascites

This study was designed to investigate the predictive role of 5-FU metabolic enzymes in malignant ascites. Forty-three malignant ascites were collected and primary cancer cells were isolated. Gene expression was detected by quantitative RT-PCR. We found that DPD mRNA was higher in patients with pancreatic cancers than those with gastric cancers, colon cancers, and liver cancers. Significant correlations were found between expression of DPD and TP, and between TS and OPRT. mRNA levels of TS and OPRT correlated significantly with the chemosensitivity of 5-FU. Assessing gene expression would be useful in predicting 5-FU sensitivity for patients with malignant ascites.

Prognostication of pancreatic adenocarcinoma by expression of thymidine phosphorylase/dihydropyrimidine dehydrogenase ratio and its correlation with survival

BACKGROUND

Dihydropyrimidine dehydrogenase (DPD) is the first rate limiting enzyme that catabolizes 5-fluorouracil. Thymidine phosphorylase (TP) catalyzes the last step that converts capecitabine into 5-fluorouracil. The TP/DPD ratio has suggested a positive correlation with the efficacy of capecitabine in human xenograft models. This is the first human study that analyzes the association of TP/DPD ratio with overall survival and disease-free survival in cases of locally advanced pancreatic cancer (LAPC).

METHODS

A total of 35 patients with newly diagnosed LAPC received 50.4 Gy radiotherapy with capecitabine 1,600 mg/m(2) followed by capecitabine 2,000 mg/m(2) x 14 days every 3 weeks till progression. Tumor specimens were procured with endoscopic ultrasound-guided fine-needle aspiration before and after week 2 of starting capecitabine radiotherapy to evaluate TP and DPD mRNA levels by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The paired t-tests showed no relationship between mRNA TP or DPD levels or TP/DPD ratio and disease-free survival. The log-rank test revealed that the lower TP/DPD ratio was statistically significantly associated with a higher overall survival with an average of 304 days in the lower TP/DPD ratio group and 172 days in the higher TP/DPD group (a difference of 132 days).

CONCLUSIONS

We found a survival benefit of approximately 4 months in our study correlating with lower TP/DPD ratio and this is quite significant in a disease whose > 5-year survival is < 5%. The TP/DPD ratio may be used as an independent marker for prognostication for LAPC and it may help in determining the chemotherapy duration, choices and possibly toxicities as well. Larger studies are needed to study the relation ship between TP/DPD ratio with these efficacy parameters.

Novel prophylactic effect of doxifluridine in superficial bladder cancer

OBJECTIVES

The prophylactic effect of 5'-deoxy-5-fluorouridine (5'-DFUR) has not been fully studied in superficial bladder cancer. The aims of this work were to investigate the prophylactic effects of 5'-DFUR in terms of tumor recurrence after transurethral resection of bladder tumor (TURBT) and to study whether thymidine phosphorylase (TdRPase) immunostaining predicts tumor recurrence.

MATERIAL AND METHODS

A total of 112 patients with pTa or pT1 bladder cancer were eligible for the analysis and were allocated to either an adjuvant group (TURBT+5'-DFUR; n = 47; initial 23 months) or a control group (TURBT alone; n = 65, final 23 months). Tumor specimens were studied immunohistochemically using anti-TdRPase antibody.

RESULTS

Tumor recurrence was observed in 54 of the patients (48%) after a median follow-up period of 26.8 months. No significant clinico-pathologic bias was observed between the two groups. Although patients in the adjuvant group had a significantly higher recurrence-free survival rate than those in the control group when considering 78 patients with pathological T1 tumors (p = 0.0272) and 65 patients who did not recur within 12 months (p = 0.001), overall there was no significant difference between the two groups. Multivariate analysis revealed that 5'-DFUR administration was the strongest predictor of late tumor recurrence, which was defined as development of recurrence 12 months after TURBT (hazard ratio 5.744; 95% CI 1.495-30.45; p = 0.0094). Immunostaining did not predict prophylactic effects of 5'-DFUR. Mild, reversible toxicity was found in 9/58 (15.5%) of the cases evaluated.

CONCLUSIONS

Oral administration of 5'-DFUR after TURBT did not prevent tumor recurrence in the overall cohort, although this novel drug may have a prophylactic effect in patients belonging to several subgroups.

Toward molecularly selected chemotherapy for advanced gastric cancer: state of the art and future perspectives

In the last few years therapeutic options for gastric cancer patients have slowly, but constantly expanded following the introduction of both new chemotherapy agents and innovative indications for treatment. Along with the medical therapy also our knowledge of the molecular mechanisms underlying this disease has progressively improved. However although the available treatment options have undoubtedly increased no clear definitive indications can be made for a standard chemotherapy regimen and we are still unable to accurately select the appropriate treatment for the appropriate patient. Many molecular determinants of response/toxicity to chemotherapy agents have been identified, but only few of them seem to possess the necessary potential for a subsequent application in the clinical practice. Some of these factors have also been indicated as a therapeutic target for a novel class of anti-cancer compounds. This systematic review will analyse available data about these factors with the aim to constitute a starting point for future research.

Phase II study of capecitabine with concomitant radiotherapy for patients with locally advanced pancreatic cancer: up-regulation of thymidine phosphorylase

PURPOSE

The objectives of this phase II study were to evaluate the effect of radiation (XRT) on thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), and tumor necrosis factor-alpha (TNF-alpha) and the efficacy of capecitabine-XRT in patients with locally advanced pancreatic cancer.

PATIENTS AND METHODS

Twenty patients received 50.4 Gy XRT with capecitabine 1,600 mg/m(2) on Monday through Friday for 6 weeks determined from our phase I study (Saif MW, Eloubeidi MA, Russo S, et al. J Clin Oncol. 2005;23:8679-8687). After capecitabine-XRT, stable and responding patients received capecitabine 2,000 mg/m(2) for 14 days every 3 weeks till progression. Restaging was performed every 9 weeks. Tumor specimens were procured with endoscopic ultrasound-fine needle aspiration before and at week 2 after capecitabine-XRT was started to evaluate the effect of XRT on TP, DPD, and TNF-alpha mRNA levels, determined by reverse transcriptase-polymerase chain reaction.

RESULTS

Among 20 patients, 4 (20%) had a partial response and 13 (65%) had stable disease. Two patients underwent surgical resection (10%). The 6-month survival rate was 84%, and the 1-year survival was 58%. Grade > or =3 toxicities included nausea/vomiting (5%), thrombosis (5%), hyperbilirubinemia (5%), and grade 3 gastrointestinal bleeding (5%). TP was elevated during week 2 when compared with the pre-XRT TP (P = 0.01). However, no such effect of XRT was found either on DPD (P = 0.22) or on TNF-alpha (P = 0.6). No correlation between TP and TNF-alpha was noticed. Also, no association between TP/DPD ratio and efficacy of capecitabine was identified.

CONCLUSIONS

This phase II study further confirms our phase I results and suggests that capecitabine-XRT is an effective, tolerable, and convenient alternative to an infusional 5-fluorouracil regimen for patients with pancreatic cancer. Although results support the use of capecitabine-XRT and TP was up-regulated, there appears to be additional genes associated with the response to capecitabine.

Role of thymidine phosphorylase and orotate phosphoribosyltransferase mRNA expression and its ratio to dihydropyrimidine dehydrogenase in the prognosis and clinicopathological features of patients with pancreatic cancer

BACKGROUND

Thymidine phosphorylase (TP), orotate phosphoribosyltransferase (OPRT), and dihydropyrimidine dehydrogenase (DPD) are important enzymes related to the metabolism of 5-fluorouracil and its derivatives. In this study, we analyzed the expression of these enzymes and evaluated the association between the expression of these enzymes and clinicopathological features and prognosis in patients with pancreatic cancer.

METHODS

TP, OPRT, and DPD mRNA expressions were detected using a real-time reverse transcriptional-polymerase chain reaction method or by immunohistochemistry, using surgical specimens obtained from 25 patients with pancreatic cancer.

RESULTS

TP mRNA expression was lower in cases with an alpha infiltration growth pattern than in cases with other infiltration growth patterns (P < 0.05). OPRT mRNA expression was higher in poorly differentiated-type cases than in differentiated type cases (P < 0.05). TP-, OPRT-, and DPD-positive stainings were found in 15 of 24 cases (63%), 10 of 19 cases (53%), and 14 of 21 cases (67%), respectively. There were significant correlations or trends between the mRNA and protein expressions of TP, OPRT, and DPD. Patients with a low TP/DPD ratio survived significantly longer than those with a high ratio (P < 0.05). Multivariate analysis demonstrated a significantly poorer outcome in patients with a high TP/DPD ratio compared with in patients with a low ratio (P < 0.05).

CONCLUSION

The TP/DPD ratio might be useful as a prognostic factor in patients with pancreatic cancer.

The prognostic significance of thymidylate synthase and dihydropyrimidine dehydrogenase in colorectal cancer of 303 patients adjuvantly treated with 5-fluorouracil

Cytotoxic effect of 5-fluorouracil 5-FU is mediated through inhibition of thymidylate synthase (TS), and 5-FU is catabolised by dihydropyrimidine dehydrogenase (DPD). Efficacy of 5-FU may therefore depend on the TS and DPD activity of colorectal cancer. Archival tumour specimens from 303 consecutive patients were analysed for the expression of TS and DPD using immunohistochemistry. All patients were completely resected for colorectal cancer stages II-III and have subsequently received adjuvant treatment with 5-FU. In a multivariate analysis adjusting for the impact of bowel obstruction and vascular tumour invasion, diffuse TS pattern was significantly associated with increased risk of recurrence (hazard ratio (HR) = 1.9; 95% confidence interval (CI): 1.1-3.2; p = 0.02), but without significant association to death (HR = 1.6; 95% CI: 0.9-2.8; p = 0.08). High TS intensity was not significantly associated with lower risk of recurrence (HR = 0.6; 95% CI: 0.3-1.1; p = 0.07) or death (HR = 0.6; 95% CI: 0.3-1.2; p = 0.2). High DPD intensity was significantly associated with increased risk of recurrence (HR = 1.5; 95% CI: 1.1-2.3; p = 0.03) and death (HR = 1.6; 95% CI: 1.1-2.5; p = 0.02). Patients with a combination of low TS and high DPD intensity were at significantly increased risk of both recurrence (HR = 2.1; 95% CI: 1.0-4.2; p = 0.04) and death (HR = 2.0; 95% CI: 1.0-4.0; p = 0.05). No relationship between tolerability and toxicity of 5-FU and TS and DPD expression was found. It is concluded that characterizing colorectal carcinomas by TS and DPD expression may disclose subsets of patients with significantly greater risk of disease recurrence and early death. This may be utilized in the selection of patients for treatment approaches and for decision on follow-up programs.

Prediction of clinical outcome of fluoropyrimidine-based chemotherapy for gastric cancer patients, in terms of the 5-fluorouracil metabolic pathway

Fluoropyrimidines are widely used in chemotherapy regimens for metastatic gastric cancer. Interindividual variation in the enzyme activity of the 5-fluorouracil (FU) metabolic pathway can affect the extent of 5-FU metabolism and affect the efficacy of 5-FU based chemotherapy. In this review, the role of the genetic factors affecting the therapeutic efficacy of fluoropyrimidines is discussed, with a special emphasis on enzymes involved in the 5-FU metabolic pathway. The gene expressions of thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase are discussed in relation to the efficacy of fluoropyrimidine treatment for metastatic gastric cancer. These candidate genes, along with others yet to be identified, could allow accurate prediction of the clinical outcome in patients receiving fluoropyrimidine-based chemotherapy in the future. Well-designed and large prospective studies, which include relevant pharmacogenetic parameters, are needed to confirm the values required to predict clinical outcome.

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Simple combinations of 5-FU pathway genes predict the outcome of metastatic gastric cancer patients treated by S-1

We evaluated the expression of 5-FU pathway genes in prechemotherapeutic fresh frozen samples obtained from primary tumors to predict response and survival of 59 metastatic gastric cancer patients treated with S-1 monotherapy as first line treatment. Five 5-FU pathway genes, including thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase (OPRT), thymidine phosphorylase (TP) and uridine phosphorylase (UP), were analyzed by the quantitative real-time reverse transcriptional PCR method. Median values of each gene were selected for cut-off values separating high and low gene expressions. In univariate analyses, low TS, high OPRT and low TP were significantly associated with a tumor shrinkage and a long survival, whereas DPD and UP gene expressions did not correlate with response and survival. Multivariate analyses revealed that independent variables were OPRT and TS for response and TS and TP for survival. When OPRT and TS were combined, a significantly increased accuracy rate of 91.5% was seen for response. Similarly, an increased hazard ratio of 10.29 was observed for survival in patients possessing low TS and low TP, compared with those with high TS or high TP. The simple combinations of 2 genes, OPRT and TS for response and TS and TP for survival, may allow identification of gastric cancer patients who will benefit from S-1 chemotherapy.

Thymidylate synthase and dihydropyrimidine dehydrogenase are related to histological effects of 5-fluorouracil and cisplatin neoadjuvant chemotherapy for primary gastric cancer patients

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and vascular endothelial growth factor (VEGF) are associated with the effect of 5-fluorouracil (5-FU) based adjuvant chemotherapy. However, very few studies have investigated the relationship between these factors and 5-FU neoadjuvant chemotherapy for primary gastric cancer patients. In this study, we studied the correlation between these markers and the histological chemotherapeutic effect in advanced gastric cancer with neoadjuvant chemotherapy.

METHODS

Sixty-two primary advanced gastric cancer patients were recruited into the study. One cycle of continuous infusion of 5-FU (300 mg/m2/day, 14 days) plus drip infusion of cisplatin (15 mg/m2/day, Day one and Day two) was performed as neoadjuvant chemotherapy. Histological chemotherapeutic responses of the resected specimens were classified into responders and nonresponders. TS, DPD, VEGF expressions both before and after neoadjuvant chemotherapy were examined immunohistochemically.

RESULTS

There was an association between the TS-low group and the responders (p < 0.05); the DPD-low group and the responders in both biopsy and surgical specimens (p < 0.01). A combination of the low-TS and low-DPD group was further associated with responders (p < 0.01). The immunoexpressions of biopsied and surgical specimens were significantly associated with each other.

CONCLUSION

Neoadjuvant chemotherapy for primary gastric cancer with one cycle of 5-FU and cisplatin was associated with histological findings in patients with low baseline TS and DPD. This dual determination may predict for efficacy of neoadjuvant treatment with these drugs.

Capecitabine therapy for refractory metastatic thyroid carcinoma: a case series

OBJECTIVE

There are few effective therapies for metastatic medullary (MTC) or radioiodine-resistant follicular thyroid carcinomas (FTC). We report a single institution's experience with capecitabine, a thymidylate synthase (TS) inhibitor, in the treatment of MTC and FTC.

DESIGN

We retrospectively analyzed five cases of metastatic thyroid carcinoma, three MTCs and two radioiodine-resistant FTCs, treated with capecitabine alone or in combination with other chemotherapeutics. Patients were selected for treatment based on low tumor TS immunohistochemical staining (< or =5%). Staining for thymidylate phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) was also performed. Therapeutic response was assessed by imaging studies and serum tumor markers: calcitonin and carcinoembryonic antigen (MTC), and thyroglobulin (FTC).

MAIN OUTCOME

Two of three patients with MTC had stable disease or disease regression on capecitabine. One of these patients had a 90% reduction in calcitonin and stabilization by imaging that lasted 4 years. Both patients with FTC initially had stable disease on capecitabine. One patient, who was treated with capecitabine in combination first with doxorubicin and then etoposide, had an initial decrease in tumor burden, followed by stable disease for 2.8 years. The second patient had stable disease, but capecitabine was discontinued after 11 months because of hand/foot syndrome.

CONCLUSIONS

This series demonstrates promising results for the use of capecitabine in treatment of MTC and radioiodine-resistant FTC, for which there is a limited repertoire of therapeutic agents. Larger studies are needed to confirm these findings and to establish the role of fluoropyramidine metabolism markers in predicting response.

Phase I study of capecitabine with concomitant radiotherapy for patients with locally advanced pancreatic cancer: expression analysis of genes related to outcome

PURPOSE

To establish the feasibility of capecitabine with concurrent radiotherapy (XRT) in patients with locally advanced (LA) pancreatic cancer and evaluate the effect of XRT on thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), and tumor necrosis factor-alpha (TNF-alpha).

PATIENTS AND METHODS

Fifteen patients with LA pancreatic cancer received three-dimensional conformal XRT to a dose of 50.4 Gy with capecitabine at escalating doses from 600 to 1,250 mg/m2 bid (Monday through Friday). Following chemo-XRT, stable and responding patients were treated with capecitabine 2,000 mg/m2 orally bid for 14 days every 21 days. Tumor specimens were procured with endoscopic ultrasound-guided fine-needle aspiration 1 week before and 2 weeks after chemo-XRT to evaluate TP, DPD, and TNF-alpha mRNA levels.

RESULTS

Dose-limiting grade 3 diarrhea was observed in two of six patients treated at a capecitabine dose of 1,000 mg/m2 with XRT. Three patients (20%) achieved partial response. Mean percent difference in TP pre- and post-XRT was 119.2% (P = .1934). There was no significant differences in mean TNF-alpha, or DPD levels pre- and post-XRT (P = .1934 and .4922, respectively). TP and TNF-alpha levels were not significantly correlated both at pre- and post-XRT (P = .670 and P < .154, respectively). Median value of TP:DPD ratios at baseline was 2.65 (range, 0.36 to 11.08). No association between TP:DPD ratio and efficacy of capecitabine or severity of toxicities was identified.

CONCLUSION

The recommended dose for phase II evaluation is capecitabine 800 mg/m2 bid (Monday through Friday) with concurrent XRT. This approach offers an easy alternative to intravenous fluorouracil as a radiosensitizer in these patients. Role of TP and TP:DPD ratio warrants further investigation in a larger clinical trial.

Expression of thymidylate synthase, dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyl transferase in prostate cancer

The enzymes thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyl transferase (OPRT) are involved in the metabolism of the anticancer drug 5-fluorouracil. No reports have examined the expression of these enzymes in prostate cancer (CaP). A total of 25 previously untreated, hormone-sensitive CaP tissue samples and 11 benign prostatic hyperplasia (BPH) specimens were examined. Tissue of CaP and BPH tissue samples were obtained from formalin-fixed, paraffin-embedded sections by laser-captured microdissection, and then RNA was extracted. mRNA expression of TS, DPD, TP, and OPRT was analyzed by quantitative reverse transcriptase-polymerase chain reaction. TS and OPRT expression levels were significantly higher in CaP samples than in BPH. DPD expression level in poorly differentiated CaP was significantly lower than that in CaP with more favorable--well or moderately differentiated--histopathology.

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.

Development of a stereological method to measure levels of fluoropyrimidine metabolizing enzymes in tumor sections using laser scanning cytometry

BACKGROUND

The enzymes thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) influence the activities of fluoropyrimidine anticancer drugs. The sensitivity of cancer cells to capecitabine, which is an oral, tumor-selective pre-prodrug of 5-fluorouracil may correlate better to the TP/DPD ratio than to levels of either enzyme alone. Our goal was to develop a quantitative immunofluorescent method for estimating the levels of TP, DPD, and their ratio in archival tumor sections.

METHODS

Mouse anti-TP and rat anti-DPD monoclonal antibodies were used for parallel indirect immunofluorescent staining. The fluorescence was measured using a laser scanning cytometer (LSC; CompuCyte, Cambridge, MA) in single cells and in sections prepared from cell lines and a human tumor. The phantom contouring feature of the LSC provided a stereologic approach for collecting the fluorescence intensity data from sections.

RESULTS

The relative fluorescence intensities measured in single cells or in sections of the cell lines, using single or double labeling, were similar, supporting the suitability of phantom contouring and two-color staining. Sections of the T-24 and ZR-75-1 cell lines placed on the same slide as the tumor section were used as internal standards for fluorescence measurements. The TP/DPD ratios measured in three cell lines correlated well with the cytotoxicity of 5'-deoxy-5-fluorouridine measured in vitro, indicating that the measurements are related to the biological activity of the drug.

CONCLUSIONS

Plotting the data as contour maps of the topologic distribution of fluorescence intensities in tumor sections allows subsequent histopathologic examination, which may reveal features of the tumors leading to high or low ratios of these enzymes. In addition, this method can be used for any drug target/metabolic system where the key components are known and suitable antibodies are available.

Combined GADD45A and thymidine phosphorylase expression levels predict response and survival of neoadjuvant-treated gastric cancer patients

PURPOSE

We evaluated the expression of seven therapy-related genes to predict the clinical outcome of advanced gastric cancer patients treated with a neoadjuvant chemotherapeutic protocol.

EXPERIMENTAL DESIGN

Pretherapeutic, formalin-fixed, and paraffin-embedded biopsies of 61 patients, who received a 5-fluorouracil (5-FU)- and cisplatin-based chemotherapy were studied. The expressions of the 5-FU-related genes TS, DPD, and TP and of the cisplatin-related genes ERCC1, ERCC4, KU80, and GADD45A were analyzed by quantitative real-time PCR. The expression levels of single genes and of various combinations were tested for an association with response and overall survival.

RESULTS

High DPD levels were more frequently found in nonresponding patients and were associated with worse survival. GADD45A and TP levels showed weak associations with response, but GADD45A expression correlated with survival. There was no association with response for TS expression, but tumors with a high TS level were associated with worse survival. The combination of GADD45A and TP revealed the strongest predictive effect. High expression values of TP and/or GADD45A were exclusively found in nonresponding patients (P = 0.002) and were associated with a significantly poorer survival (P = 0.04).

CONCLUSIONS

Combined gene expression levels of TP and GADD45A represent a new variable to predict the clinical outcome after neoadjuvant chemotherapy in gastric cancer. The association of DPD expression with response and survival underlines a predominant role of DPD to predict 5-FU sensitivity. The association of TS expression levels with survival but not with response suggests an importance of this gene for tumor progression.

Thymidine phosphorylase (platelet-derived endothelial-cell growth factor) in cancer biology and treatment

Thymidine phosphorylase (TP) is often induced in the tumour microenvironment by physiological and chemical stress. Its induction protects cells from apoptosis and helps cell survival by stimulating nucleoside metabolism and angiogenesis. Chemotherapy often upregulates TP, which acts in cell rescue; this result indicates that TP is a crucial therapeutic target. Clinical trials for metastatic diseases have shown that TP-targeting chemotherapy with fluorouracil derivatives greatly improves the effectiveness of conventional chemotherapy for not only response but also prognosis. This new idea, the improvement of TP-inducible therapy with TP-targeting therapy, should be further investigated for early disease states, and inhibitors of TP warrant extensive investigation.

Thymidylate synthase and dihydropyrimidine dehydrogenase gene expression in relation to differentiation of gastric cancer

Thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) are important enzymes of DNA de novo synthesis and the salvage pathway in cancer cells, respectively. Intratumoral TS and DPD gene expressions were evaluated to determine the correlation between the expression of the 2 genes in both normal stromal tissues and tissues with different degrees of malignant differentiation in primary gastric cancer. The study population consisted of 78 consecutive patients with advanced gastric cancer who underwent surgical treatment. Laser-captured microdissection of malignant or normal stromal tissues was performed in formalin-fixed, paraffin-embedded specimens. After extraction of RNA, TS and DPD gene expressions were measured by the real-time reverse transcriptional PCR method. Apart from degree of differentiation, TS and DPD in malignant tissue showed no correlation with clinicopathologic factors. TS in malignant tissue was higher in differentiated type cases than undifferentiated type cases (p < 0.01). However, DPD in malignant tissue of undifferentiated type cases was statistically higher than that of differentiated type cases (p < 0.05). In normal stromal tissue, neither TS nor DPD had any correlation with clinicopathologic factors. TS in malignant tissue was statistically higher than in normal stromal tissue in both differentiated and undifferentiated types (p < 0.0001). DPD in differentiated type malignant tissue was statistically lower than in normal stromal tissue (p < 0.001), but no difference was seen in undifferentiated type cases. TS and DPD gene expressions in primary gastric cancer differ according to degree of differentiation and between malignant and normal stromal tissue.

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

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

The ratio of thymidine phosphorylase to dihydropyrimidine dehydrogenase in tumour tissues of patients with metastatic gastric cancer is predictive of the clinical response to 5'-deoxy-5-fluorouridine

The aim of this work was to determine whether intratumour contents of thymidine phosphorylase (TP), which converts 5'-deoxy-5-fluorouridine (5'-DFUR) to 5-fluorouracil, and dihydropyrimidine dehydrogenase (DPD), which degrades 5-fluorouracil to inactive molecules, could be useful in predicting the response of patients with metastatic gastric cancer to chemotherapy using 5'-DFUR. Endoscopic biopsy specimens for the measurement of TP and DPD were obtained from the primary lesions before the start of combination chemotherapy, in which 5'-DFUR, cisplatin and mitomycin C were administered. TP and DPD were measured by enzyme-linked immunosorbent assays after the objective responses to chemotherapy had been confirmed. Twenty five patients were enrolled in this study and data for 22 patients in whom responses were confirmed were analysed. The median levels (ranges) of TP and DPD were 80 (4.9-360) and 44 (15-82) U/mg protein, respectively. The median value (range) of TP to DPD ratios was 1.9 (0.25-5.1). Eight patients with a complete or partial response to chemotherapy had significantly higher TP to DPD ratios than did the remaining patients with stable or progressive disease (P = 0.014). When a cut-off level of TP to DPD ratio was defined as the median value, the high-ratio group (n = 11) showed a significantly higher response rate (64% vs. 9.1%, P = 0.024) than the low-ratio group (n = 11). Overall survival of the high-ratio group was significantly longer than that of the low-ratio group (the median survival time; 300 days vs. 183 days, P = 0.047). The efficacy of 5'-DFUR could be optimised by preselecting patients with high TP/ DPD ratios in their tumour tissues, and this would be applicable to the treatment with capecitabine.

Dihydropyrimidine dehydrogenase and the efficacy and toxicity of 5-fluorouracil

The identification of genetic factors associated with either responsiveness or resistance to 5-fluorouracil (5-FU) chemotherapy, as well as genetic factors predisposing patients to the development of severe 5-FU-associated toxicity, is increasingly being recognised as an important field of study. Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (5-FU). Although the role of tumoral levels as a prognostic factor for clinical responsiviness has not been firmly established, there is ample evidence that a deficiency of DPD is associated with severe toxicity after the administration of 5-FU. Patients with a partial DPD deficiency have an increased risk of developing grade IV neutropenia. In addition, the onset of toxicity occurred twice as fast compared with patients with a normal DPD activity. To date, 39 different mutations and polymorphisms have been identified in DPYD. The IVS14+1G>A mutation proved to be the most common one and was detected in 24-28% of all patients suffering from severe 5-FU toxicity. Thus, a deficiency of DPD appears to be an important pharmacogenetic syndrome.

Both gene expression for orotate phosphoribosyltransferase and its ratio to dihydropyrimidine dehydrogenase influence outcome following fluoropyrimidine-based chemotherapy for metastatic colorectal cancer

Activation of 5-fluorouracil into its nucleotides requires phosphorylation by three pathways involving orotate phosphoribosyl-transferase (OPRT), uridine phosphorylase (UP), or thymidine phosphorylase (TP). In this study, we investigated the association between gene expressions of these three enzymes and antitumour effect. Gene expressions in primary colorectal tumours were analysed by a real-time reverse transcriptional-polymerase chain reaction method in 37 patients receiving oral treatment of tegafur-uracil and leucovorin for metastatic diseases. The median values of OPRT mRNA expressions were 1.39 and 0.85 for responding tumours and nonresponding tumours, respectively, showing a statistically significant difference (P=0.0008). Responding tumours had statistically lower expressions of TP mRNA than nonresponding tumours (P=0.006). However, there was no difference in UP mRNA expression between responding and nonresponding tumours. Patients with high OPRT (>/=1.0) gene expression survived longer than those with low OPRT (<1.0) expression. Dihydropyrimidine dehydrogenase (DPD) gene expressions were measured. Responding tumours had a statistically higher OPRT/DPD ratio than the nonresponding ones (P=0.003). When the median value of the OPRT/DPD ratio was selected as the cutoff value, patients with a high OPRT/DPD ratio survived statistically longer than those with a low ratio (P=0.0014). In conclusion, both the expression of OPRT gene and the OPRT/DPD ratio might be useful as predictive parameters for the efficacy of fluoropyrimidine-based chemotherapy for metastatic colorectal cancer.

Dihydropyrimidine dehydrogenase in normal and malignant endometrium: relationship with cell proliferation and thymidine phosphorylase

Dihydropyrimidine dehydrogenase (DPD) is a pyrimidine salvage enzyme responsible for degradation of thymine, which is produced from thymidine by thymidine phosphorylase (TP). Our purpose was to determine the relationship between DPD, cell proliferation and TP expression in human endometrium. We examined DPD gene expression using reverse transcription-polymerase chain reaction, DPD protein levels using enzyme-linked immunosorbent assay, and DPD protein localization using immunohistochemistry in 58 normal endometria and 28 endometrial cancers. DPD gene expression was then related to the proliferating cell nuclear antigen index and to TP gene expression. DPD gene expression, which was correlated with DPD protein level, was relatively stable throughout various menstrual phases but was significantly elevated in postmenopausal status. It was significantly lower in endometrial cancer than in normal endometrium. Localization analysis revealed that DPD protein was located primarily in epithelial cells, but was also present in stromal cells. DPD gene expression correlated inversely with the PCNA index. TP gene expression pattern contrasted with that of DPD in postmenopausal and malignant endometrium. A high ratio of TP to DPD gene expression was significantly more frequent in endometrial cancer than in normal endometrium in any menstrual phase. DPD may act cooperatively with TP to affect cell function by maintaining the pyrimidine nucleotide pool balance in normal and malignant endometrium.

Augmentation of the antitumor activity of capecitabine by a tumor selective dihydropyrimidine dehydrogenase inhibitor, RO0094889

Capecitabine is an orally available fluoropyrimidine and is finally converted to 5-FU selectively in tumor tissues. In our study, we examined whether the antitumor activity of capecitabine is directly affected by a modulation of dihydropyrimidine dehydrogenase (DPD). The modulations were carried out by the overexpression of DPD in tumor cells and by tumor selective DPD inhibition. The DPD-overexpressing cells were obtained by transfection of human DPD cDNA into HCT116 human colorectal cancer cells. The HCT116 cells bearing DPD cDNA expressed about 13 times higher DPD activities than the parental HCT116 cells, and they became significantly less susceptible to capecitabine than the parental cells when transplanted into nude mice. Administration of RO0094889 that is converted to a DPD inhibitor 5-vinyluracil selectively in tumor tissues restored the antitumor activity of capecitabine against the tumor of the HCT116 cells carrying DPD cDNA and various tumors expressing DPD. As compared to 5-ethynyluracil or 5-vinyluracil, which inhibited DPD not only in tumor tissues but also in other non-cancerous tissues, the effective dose range of RO0094889 in augmenting the efficacy of capecitabine was much broader. These results indicate that the antitumor activity of capecitabine is directly affected by DPD activities in tumor tissues and therefore, the combination of capecitabine and a tumor selective DPD inhibitor, RO0094889, will be beneficial to patients who have tumors with high levels of DPD.

Prediction of sensitivity to fluoropyrimidines by metabolic and target enzyme activities in gastric cancer

BACKGROUND

This study was designed to investigate the role of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), and thymidine phosphorylase (TP) in tumor progression and sensitivity to 5-fluorouracil (5-FU).

METHODS

A total of 275 tumor samples from 275 patients with gastric cancer were utilized in this study. TS activity was determined in 130 samples by 5-fluorodeoxyuridine monophosphate binding assay. DPD activity was measured in 140 samples by radioenzymatic assay, and TP protein level was determined in 157 samples by an enzyme-linked immunosorbent assay (ELISA) system. These parameters were compared with several clinicopathologic factors and sensitivity to 5-FU determined by in-vitro ATP assay. The antitumor activities of 5-FU, uracil plus tegafur (UFT), and 1M tegafur--0.4 M 5-chloro-2,4-dihydroxypyridine--1 M potassium oxonate (S-1 [TS-1]) were also compared, using three human gastric cancer xenografts in nude mice.

RESULTS

There was no correlation between either TS or TP and sensitivity to 5-FU. However, a weak inverse correlation was found between DPD activity and sensitivity to 5-FU. High DPD activity in tumor resulted in poor prognosis, especially in patients who received 5-FU-based adjuvant chemotherapy. Although TP was significantly correlated with depth of tumor invasion and with lymphatic and venous invasions, TP alone had no impact on survival. On the other hand, TS, as well as peritoneal, hepatic, and lymph node metastases, was selected as an independent prognostic factor in gastric cancer. In the animal model, there was no significant difference in antitumor activities among the drugs in a tumor with low DPD activity. However, S-1 showed superior antitumor activity to 5-FU or UFT in tumors with high DPD activity.

CONCLUSION

DPD is considered to be a most important predictive factor of 5-FU sensitivity. The use of DPD inhibitory fluoropyrimidines is strongly recommended for tumors with high DPD activity.