Circadian rhythms in CYP2A5 expression underlie the time-dependent effect of tegafur on breast cancer.

The chemotherapeutic agent tegafur, a prodrug that prolongs the half-life of fluorouracil (5-FU), exerts antitumor effects against various cancers. Since tegafur is metabolized to 5-FU by CYP2A6 in the liver, the expression of CYP2A6 determines the effect of tegafur. Here, we report that the expression rhythm of Cyp2a5, a homolog of human CYP2A6, in female mice causes dosing time-dependent differences in tegafur metabolism. In the livers of female mice, CYP2A5 expression showed a circadian rhythm, peaking during the dark period. This rhythm is regulated by RORA, a core clock component, and abrogation of the CYP2A5 activity abolished the time-dependent difference in the rate of tegafur metabolism in female mice. Furthermore, administration of tegafur to mice transplanted with 4T1 breast cancer cells during the dark period suppressed increases in tumor size compared to female mice treated during the light period. Our findings reveal a novel relationship between 5-FU prodrugs and circadian clock machinery, potentially influencing antitumor effects, and contributing to the development of time-aware chemotherapy regimens for breast cancer.

Effect of (-)-epicatechin-3-gallate and (-)-epigallocatechin-3-gallate on the binding of tegafur to human serum albumin as determined by spectroscopy, isothermal titration calorimetry, and molecular docking.

Green tea has attracted great interest as a cancer prevention agent. Interactions of tea polyphenols with serum albumin may influence the efficacy of drugs. The interactions of (-)-epigallocatechin-3-gallate (EGCG), (-)-epicatechin-3-gallate (ECG), and tegafur (TF) alone or in combination with human serum albumin (HSA) at pH 7.4 and different temperatures were investigated by spectroscopic methods, isothermal titration calorimetry (ITC), and molecular docking. The binding affinities to HSA were ranked in the order of EGCG > ECG > TF, and the interactions were spontaneous and exothermic. Ternary system studies showed that the presence of one component hindered the binding of another component to HSA. The secondary structures of HSA were slightly altered in the presence of the ligands. Site marking experiments and molecular docking showed that EGCG and ECG mainly bound to subdomain IIA and ΙΙΙA while TF bound to subdomain ΙΙA and ΙB. Results indicated that the existence of ECG and EGCG would influence the binding of TF to HSA and can increase the free concentration of TF. Obtained results would provide beneficial information about possible interference upon simultaneous co-administration of the tea components and drugs. Communicated by Ramaswamy H. Sarma.

Metronomic S-1 dosing and thymidylate synthase silencing have synergistic antitumor efficacy in a colorectal cancer xenograft model.

Metronomic chemotherapy is currently considered an emerging therapeutic option in clinical oncology. S-1, an oral formulation of Tegafur (TF), a prodrug of 5-fluorouracil (5-FU), is designed to improve the antitumor activity of 5-FU in tandem with reducing its toxicity. Clinically, metronomic S-1 dosing has been approved for the standard first- and second-line treatment of metastatic or advanced stage of colorectal (CRC). However, expression of intratumor thymidylate synthase (TS), a significant gene in cellular proliferation, is associated with poor outcome to 5-FU-based chemotherapeutic regimens. In this study, therefore, we examined the effect of a combination of TS silencing by an RNA interfering molecule, chemically synthesized short hairpin RNA against TS (shTS), and 5-FU on the growth of human colorectal cancer cell (DLD-1) both in vitro and in vivo. The combined treatment of both shTS with 5-FU substantially inhibited cell proliferation in vitro. For in vivo treatments, the combined treatment of metronomic S-1 dosing with intravenously injected polyethylene glycol (PEG)-coated shTS-lipoplex significantly suppressed tumor growth, compared to a single treatment of either S-1 or PEG-coated shTS-lipoplex. In addition, the combined treatment increased the proportion of apoptotic cells in the DLD-1 tumor tissue. Our results suggest that metronomic S-1 dosing combined with TS silencing might represent an emerging therapeutic strategy for the treatment of patients with advanced CRC.

Phase II trial of S-1 plus leucovorin in patients with advanced gastric cancer and clinical prediction by S-1 pharmacogenetic pathway.

BACKGROUND: The first one-arm phase II trial aimed to evaluate and predict efficacy and safety of S-1 plus oral leucovorin (S-1/LV) as first-line chemotherapy for patients with advanced gastric cancer (AGC), using S-1 pharmacogenetic pathway approach. PATIENTS AND METHODS: A total of 39 patients orally took S-1 at conventional dose and LV simultaneously at a dose of 25 mg twice daily for a week, within a 2-week cycle. The primary endpoint was overall response rate (ORR), while the secondary endpoints were progression-free survival (PFS), time to failure (TTF), overall survival (OS), disease control rate (DCR), and adverse events (AEs). Peripheral blood was sampled prospectively for baseline expression of dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase (OPRT), thymidine phosphorylase (TP), and thymidylate synthase (TS), CYP2A6 gene polymorphisms, and 5-FU pharmacokinetics. RESULTS: The ORR and DCR were 41.0 and 76.9%. The median PFS, TTF, and OS were 4.13, 3.70, and 11.40 months. Grade 3-4 AEs occurred in only 13 patients, and grade 4 AEs occurred in only 1 of them. High OPRT/TS and peritoneal metastasis (vs. liver metastasis) independently predicted responding. High OPRT/DPD independently predicted grade 3-4 AEs. High AUC0-24h of 5-FU and metastatic/recurrent sites ≤2 (vs. >3) independently predicted prolonged PFS. Low baseline plasmic DPD independently predicted prolonged OS. CONCLUSIONS: Two-week, oral S-1/LV regimen demonstrated promising efficacy and safety as first-line chemotherapy for AGC. CLINICALTRIALS. GOV IDENTIFIER: NCT02090153.

The Effect of 5-Aminolevulinic Acid on Cytochrome P450-Mediated Prodrug Activation.

Of late, numerous prodrugs are widely used for therapy. The hemeprotein cytochrome P450 (CYP) catalyzes the activation of prodrugs to form active metabolites. Therefore, the activation of CYP function might allow the use of lower doses of prodrugs and decrease toxicity. We hypothesized that the addition of 5-aminolevulinic acid (ALA), a precursor in the porphyrin biosynthetic pathway, enhances the synthesis of heme, leading to the up-regulation of CYP activity. To test this hypothesis, we treated a human gastric cancer cell line with ALA and determined the effect on CYP-dependent prodrug activation. For this purpose, we focused on the anticancer prodrug tegafur, which is converted to its active metabolite 5-fluorouracil (5-FU) mainly by CYP2A6. We show here that ALA increased CYP2A6-dependent tegafur activation, suggesting that ALA elevated CYP activity and potentiated the activation of the prodrug.

Species variation in the enantioselective metabolism of tegafur to 5-fluorouracil among rats, dogs and monkeys.

OBJECTIVES: Tegafur (FT), a pro-drug of 5-fluorouracil (5-FU), is a racemate consisting of two enantiomers, R and S-FT. The aim of this study was to clarify interspecies variation in the enantioselective metabolism of FT. METHODS: Plasma concentrations of FT enantiomers were determined in rats, dogs and monkeys following intravenous and oral dosing of the racemate (5 mg/kg). In addition, the enzymatic conversion of FT enantiomers to 5-FU was assayed using hepatic preparations. KEY FINDINGS: Metabolic clearance of R-FT was higher than that of S-FT in rats and monkeys, but S-FT was the preferential substrate for dogs. An inhibition study revealed that cytochrome P450 is primarily responsible for the enantioselective metabolism of FT in rats and dogs. In contrast, in monkeys, thymidine phosphorylase was a determinant of the enantioselectivity in FT metabolism. Although oral bioavailability was not enantioselective, in-vitro and in-vivo kinetic studies suggested that the enantioselectivity in the hepatic intrinsic clearance of FT directly influences the body clearance in all animal species examined. CONCLUSIONS: The interspecies variations were observed in the enantioselective pharmacokinetics of FT, and the in-vivo enantioselectivity could be extrapolated from the in-vitro metabolic activities.

Effect of CYP2A6 genetic polymorphism on the metabolic conversion of tegafur to 5-fluorouracil and its enantioselectivity.

Tegafur (FT), a prodrug of 5-fluorouracil, is a chiral molecule, a racemate of R- and S-isomers, and CYP2A6 plays an important role in the enantioselective metabolism of FT in human liver microsomes (R-FT >> S-FT). This study examined the enantioselective metabolism of FT by microsomes prepared from Sf9 cells expressing wild-type CYP2A6 and its variants (CYP2A6*7, *8, *10, and *11) that are highly prevalent in the Asian population. We also investigated the metabolism of coumarin and nicotine, both CYP2A6 probe drugs, in these variants. Enzyme kinetic analyses showed that CYP2A6.7 (I471T) and CYP2A6.10 (I471T and R485L) had markedly lower Vmax values for both enantiomers than wild-type enzyme (CYP2A6.1) and other variant enzymes, whereas Km values were higher in most of the variant enzymes for both enantiomers than CYP2A6.1. The ratios of Vmax and Km values for R-FT to corresponding values for S-FT (R/S ratio) were similar among enzymes, indicating little difference in enantioselectivity among the wild-type and variant enzymes. Similarly, both CYP2A6.7 and CYP2A6.10 had markedly lower Vmax values for coumarin 7-hydroxylase and nicotine C-oxidase activities than CYP2A6.1 and other variant enzymes, whereas Km values were higher in most of the variant enzymes for both activities than CYP2A6.1. In conclusion, the amino acid substitutions in CYP2A6 variants generally resulted in lower affinity for substrates, while Vmax values were selectively reduced in CYP2A6.7 and CYP2A6.10. Consistent R/S ratios among CYP2A6.1 and variant enzymes indicated that the amino acid substitutions had little effect on enantioselectivity in the metabolism of FT.

[Predicting drug efficacy-fluorinated pyrimidines (fluorouracil, S-1 and capecitabine)].

The elucidation in recent years of intracellular signaling mechanisms related to cancer cell growth has been accompanied by increases in both drug development and biomarker research. While treatment strategies using biomarkers have been established and put to clinical use for various types of cancers and medications, most are limited to drugs targeting specific molecules, and none have been established for traditional cytotoxic drugs. For fluoropyrimidines, the standard drugs used in chemotherapy for gastrointestinal cancer, biomarker research has been conducted on targets such as thymidylate synthase(TS), dihydropyrimidine dehydrogenase(DPD), and thymidine phosphorylase(TP). The results of research on these targets have recently been reported, albeit retrospectively, in a number of additional studies and large-scale clinical trials. While some studies suggested that there is future potential for these targets, in general, it appears that there are insufficient data for their clinical application as biomarkers at present. Given the advances made toward the realization of personalized medicine, the discovery of biomarkers for fluoropyrimidines is of great importance and warrants further study.

Formation pathways of gamma-butyrolactone from the furan ring of tegafur during its conversion to 5-fluorouracil.

Tegafur (FT) is a 5-fluorouracil (5-FU) prodrug that has been clinically used for various cancer chemotherapies. The following metabolites of FT were identified in patients: 5-FU, fluoro-beta-alanine, and gamma-butyrolactone (GBL) and its acidic form, gamma-hydroxybutyrate (GHB). GBL/GHB, which is probably generated from the furan ring of FT, inhibits tumor cell angiogenesis, contributing to the antitumor effect of FT-based therapies. In the present study, we identified the metabolites formed from the furan ring of FT by CYP2A6 and thymidine phosphorylase (TPase) using 2,4-dinitrophenylhydrazine derivatization procedures and clarified the metabolic pathway of FT to GBL/GHB. Succinaldehyde (SA) and 4-hydroxybutanal (4-OH-BTL) were produced as the metabolites because of the cleavage of the furan ring of FT during its conversion to 5-FU in cDNA-expressed CYP2A6 and purified TPase, respectively; however, GBL/GHB was hardly detected in cDNA-expressed CYP2A6 and purified TPase. GBL/GHB was formed after human hepatic microsomes or cDNA-expressed CYP2A6 mixed with cytosol were incubated with FT. Furthermore, 4-OH-BTL was converted to GBL/GHB in the microsomes and cytosol. These results suggest that GBL/GHB is generated from FT through the formation of SA and 4-OH-BTL but not directly from FT. Furthermore, the amount of 5-FU and GBL/GHB formed in the hepatic S9 was markedly decreased in the presence of a CYP2A6 inhibitor, suggesting that GBL/GHB may be mainly generated through the CYP2A6-mediated formation of SA.

A review of analytical methods for the determination of 5-fluorouracil in biological matrices.

5-Fluorouracil (5-FU) is a cytostatic agent that has been widely used in the treatment of various solid tumours for more than 20 years, and is still considered to be among the most active antineoplastic agents in advanced colorectal cancer and malignancies of the head and neck. A large number of non-chromatographic and chromatographic methods for the quantitation of 5-FU, related prodrugs and their metabolites in biological matrices have been developed in the last 30 years to support preclinical and clinical studies. However, 5-FU monitoring has not been widely used, at least not in the USA, and certainly not outside the clinical research setting, given the absence of simple, fast and inexpensive testing methods for 5-FU monitoring. Recent developments with testing based on liquid chromatography-tandem mass spectrometry and a nanoparticle antibody-based immunoassay may facilitate routine monitoring of 5-FU in daily clinical practice. In this review the advantages and disadvantages of the bioanalytical methods developed and used for 5-FU, its metabolites and related prodrugs are discussed.

A micro cell culture analog (microCCA) with 3-D hydrogel culture of multiple cell lines to assess metabolism-dependent cytotoxicity of anti-cancer drugs.

A microfluidic device with 3-D hydrogel cell cultures has been developed to test the cytotoxicity of anti-cancer drugs while reproducing multi-organ interactions. In this device, a micro cell culture analog (microCCA), cells embedded in 3-D hydrogels are cultured in separate chambers representing the liver, tumor, and marrow, which are connected by channels mimicking blood flow. While the microfluidic network provides a platform for mimicking the pharmacokinetic and pharmacodynamic profiles of a drug in humans, the 3-D hydrogel provides a more physiologically realistic environment to mimic the tissue than monolayer culture. Colon cancer cells (HCT-116) and hepatoma cells (HepG2/C3A) were encapsulated in Matrigel and cultured in the tumor and the liver chamber in a microCCA, respectively. Myeloblasts (Kasumi-1) were encapsulated in alginate in the marrow chamber; a stiffer hydrogel was necessary to prevent cell migration out of the matrix. The cytotoxic effect of Tegafur, an oral prodrug of 5-fluorouracil (5-FU), on each cell line was tested using the microCCA with cell-embedded hydrogel. The comparison of experimental results using a 96-well microtiter plate and a microCCA demonstrated that the microCCA was able to reproduce the metabolism of Tegafur to 5-FU in the liver and consequent death of cells by 5-FU, while the cultures in a 96-well microtiter plate were unable to do so. The microCCA utilizing 3-D hydrogel cell cultures has potential as a platform for pharmacokinetic-based drug screening in a more physiologically realistic environment.

S-1: a promising new oral fluoropyrimidine derivative.

S-1 is an oral fluoropyrimidine that is designed to improve the antitumor activity of 5-fluorouracil (5-FU) concomitantly with an intent to reduce its toxicity. S-1 consists of tegafur, a prodrug of 5-FU combined with two 5-FU biochemical modulators:5-chloro-2,4-dihydroxypyridine (gimeracil or CDHP), a competitive inhibitor of dihydropyrimidine dehydrogenase and oteracil potassium which inhibits phosphorylation of 5-FU in the gastrointestinal tract decreasing serious gastrointestinal toxicities,including nausea, vomiting, stomatitis and diarrhea. Being an oral agent, S-1 offers convenience of administration and prevents complications of central venous access such as infection, thrombosis and bleeding. S-1 has shown efficacy in both gastrointestinal as well non-gastrointestinal malignancies. The authors review the current literature and provide their expert opinion on the incorporation of S-1 in the treatment of solid malignancies [corrected].

UFT and its metabolite gamma-butyrolactone (GBL) inhibit angiogenesis induced by vascular endothelial growth factor in advanced cervical carcinoma.

OBJECTIVE: The aim of this study was to evaluate the potential role of UFT and its metabolite gamma-butyrolactone (GBL) for inhibition of angiogenesis induced by vascular endothelial growth factor (VEGF) in advanced cervical carcinoma by the determination of serum GBL and VEGF, and by immunohistochemical staining to assess VEGF protein expression, before and after UFT therapy. METHODS: The subjects were 35 patients with an advanced cervical carcinoma and five healthy volunteers between 2002 and 2003 at Hiroshima University Hospital, under informed consent. The patients received two courses of oral fluoropyrimidine (UFT) therapy at a dose of 600 mg/day for 5 and 2 days off treatment. Serum GBL and VEGF was measured before and after UFT therapy by the gas chromatography mass spectrometry and ELISA-kit in 22 patients and five healthy volunteers, respectively. Immunohistochemical detection of VEGF protein was done in 35 cervical cancers. Results The mean serum GBL level before and after UFT therapy was 21.9 +/- 2.3 and 79.3 +/- 6.2 ng/ml, respectively, and it was significantly increased after UFT administration (P < 0.0001). The mean serum VEGF level before and after UFT therapy was 95.3 +/- 28.1 and 67.5 +/- 11.2 pg/ml, respectively, and it was decreased by UFT administration. In 20 out of 33 (66.6%) patients who were detected with VEGF protein, VEGF protein expression was decreased by UFT therapy. The Delta GBL value (GBL after UFT--GBL before UFT therapy) showed a significant inverse correlation with Delta VEGF value (VEGF after therapy--VEGF before therapy) (r2 = 0.940). CONCLUSIONS: Our findings suggest that UFT and its metabolite GBL inhibit angiogenesis induced by VEGF to have an antitumor effect on cervical cancer.

Pharmacokinetics of gamma-hydroxybutylic acid (GHB) and gamma-butyrolactone (GBL), the anti-angiogenic metabolites of oral fluoropyrimidine UFT, in patients with gastric cancer.

Gamma-hydroxybutylic acid (GHB) and gamma-butyrolactone (GBL), the metabolites of UFT, which is an oral fluoropyrimidine, have been reported to inhibit angiogenesis with IC50 values of 25.8 ng/ml. The pharmacokinetics of GHB and GBL were examined after the administration of UFT in patients with gastric cancer. The patients received 200 mg of UFT orally twice a day. Peripheral blood samples were collected at 0, 0.5, 1, 2 and 4 hr after the time of dosing on day 5. The baseline and endogenous GBL concentrations in plasma were 20.2 +/- 7.5 ng/ml for patients and 16.8 +/- 4.0 ng/ml for volunteers (P = 0.221). The values of C(max) for tegafur, uracil, 5-FU and GBL were 14.7 +/- 5.2 and 4.0 +/- 2.8 microg/ml, 191.2 +/- 115.3 and 147.5 +/- 57.3 ng/ml, respectively, and the values of Tmax were 1.0 +/- 0.6, 1.1 +/- 0.6, 0.9 +/- 0.6 and 1.2 +/- 0. 6 hr, respectively. The concentration of GBL was much higher than its IC50 value for angiogenesis. GBL is thus suggested to contribute to the anticancer effects of UFT in addition to that of 5-FU, which is continuously metabolized from UFT.

Tegafur and 5-fluorouracil pelvic tissue concentrations in rectal cancer patients receiving preoperative chemoradiation.

BACKGROUND AND PURPOSE: To investigate the presence of 5-Fluorouracil (5-FU) in pelvic tissue after oral administration of tegafur. To measure tegafur and 5-FU concentrations in normal rectal mucosa, perirectal fat and residual tumor in rectal cancer patients receiving preoperative chemoradiation. To correlate drug concentrations with cancer downstaging effects. PATIENTS AND METHODS: Three tissue samples taken from 16 surgical specimens after recto-sigmoid resection were analyzed. Tegafur and 5-FU concentrations were measured using high-performance liquid chromatography. 16 patients with locally advanced rectal cancer were treated with preoperative pelvic irradiation (45-50 Gy) sensitized with oral tegafur (400 mg for every 8 hours daily). Seven patients received a precharge dose of tegafur (400 mg oral every 8 hours) 24 hours before surgery. RESULTS: In 8 of the 9 patients who did not receive a precharge dose, detectable levels of tegafur were observed in fat tissue, normal mucosa and tumor, but detectable 5-FU levels were only observed in one patient. Mean concentrations (ranges) for tegafur in fat, normal mucosa and tumor in patients without the precharge dose were 72.19 (12.1-205.6), 179.53 (11.30-727.7) and 252.35 (27.9-874.6) ng/g, respectively; mean concentrations for 5-FU in the same samples were 0.95, 1.92 and 2.68 ng/g (1 patient), respectively. In patients receiving a tegafur precharge, both tegafur and 5-FU were present in all tissue samples with the exception of 2 fat samples, in which drug concentrations were undetectable. 5-FU levels were higher in tumor than other sites, with a median value of 68.24 ng/g (range 3.8-283.05 ng/g). Tegafur levels were also higher in tumor samples than other sites (mean 3446.53 ng/g, range 1044.5-7847.0 ng/g), except in 2 patients who had higher levels of tegafur in normal mucosa. CONCLUSIONS: Tegafur and 5-FU are not always present in pelvic tissues 5 to 6 weeks after oral administration of tegafur. Both drugs were present in the tissues analyzed, in relevant concentrations, 24 hours after oral administration of tegafur. The data obtained suggest a tendency (not significant) toward a correlation between levels of 5-FU present in the residual tumor and cancer downstaging.

Characterization of novel CYP2A6 polymorphic alleles (CYP2A6*18 and CYP2A6*19) that affect enzymatic activity.

Genetic polymorphisms of CYP2A6 gene are known as a causal factor of the interindividual differences in nicotine metabolism. We found three novel CYP2A6 alleles. The CYP2A6(*)18A allele has a single nucleotide polymorphism (SNP) of A5668T (A1175T, Y392F) in exon 8. The CYP2A6(*)18B allele has synonymous SNPs of G51A (G51A), T5684C (T1191C), and T5702C (T1209C) in addition to A5668T (A1175T, Y392F). The CYP2A6(*)19 allele has the SNPs of A5668T (A1175T, Y392F), T6354C (intron 8), and T6558C (T1412C, I471T) as well as the conversion with the CYP2A7 sequence in the 3'-untranslated region, in which the latter two changes correspond to CYP2A6(*)7. Ethnic differences in the frequencies of these alleles were observed between whites, African-Americans, Japanese, and Koreans. Wild or variant CYP2A6 (CYP2A6(*)18, CYP2A6(*)19, and CYP2A6(*)7) were expressed in Escherichia coli. For coumarin 7-hydroxylation and 5-fluorouracil formation from tegafur, the K(m) values were increased, and V(max) values were decreased in CYP2A6.18 compared with those in CYP2A6.1, resulting in decreased clearance to 50 and 35% of that of the wild type, respectively. The K(m) and V(max) values for nicotine C-oxidation were both increased, resulting in no change of clearance. In CYP2A6.19, the effects on the coumarin 7-hydroxylation and 5-fluorouracil formation (increased K(m) and decreased V(max)) were prominent, resulting in decreased clearance to 8% of those of the wild type. For nicotine C-oxidation, the K(m) and V(max) values were both decreased, resulting in decreased clearance to 30% of that of the wild type. The changes of the kinetics in CYP2A6.19 were similar to those in CYP2A6.7. In vivo nicotine metabolism was evaluated in whites (n = 56) and Koreans (n = 40). Although the CYP2A6(*)18 and CYP2A6(*)19 alleles were found only heterozygously, a subject with CYP2A6(*)7/CYP2A6(*)19 showed a lower cotinine/nicotine ratio of the plasma concentration compared with homozygotes of the CYP2A6(*)1A, supporting the in vitro results that the CYP2A6(*)19 allele leads to decreased enzymatic activity.

Thymidylate synthase expression and prognosis of patients with gastrointestinal cancers receiving adjuvant chemotherapy: a review.

BACKGROUND AND AIMS: Many studies have been published that report an association between thymidylate synthase (TS) and response to fluoropyrimidine-based chemotherapy and the overall outcome of patients with gastrointestinal cancer. The results have given rise to the possibility that, by determination of TS levels, the physician may decide if the patient has a potential benefit from fluoropyrimidine-based treatment, similar to measurements of oestrogen receptors in breast cancer. The purpose of this review is to summarize critically the reports on TS measurement in gastrointestinal cancer, focusing on the adjuvant fluoropyrimidine treatment situation. METHODS: We reviewed more than 20 studies that reported the association of TS with the clinical outcome in patients with gastrointestinal cancer who had undergone complete resection of the primary tumour only or were receiving additional adjuvant chemotherapy. RESULTS: Patients with metastasized disease who expressed high TS levels display a low probability of responding to fluoropyrimidine-based treatment and have a poorer survival rate. Patients with high TS levels who undergo complete surgical resection of the primary tumour also have a poorer prognosis than those with tumours with low TS expression. In contrast to advanced disease and to surgery alone, patients with high TS levels appear to benefit, especially, from adjuvant fluoropyrimidine-based chemotherapy after complete primary tumour resection, while patients with low TS levels do not. CONCLUSION: Patients with gastrointestinal cancers that express high TS levels have a poor prognosis with regard to fluoropyrimidine-based palliative chemotherapy or complete primary tumour resection. In contrast, patients with high TS levels might benefit from adjuvant fluoropyrimidine-based treatment after primary tumour resection. However, additional prospective studies are mandatory to define the precise role of TS in adjuvant therapy.