Randomized clinical trial of oral and intravenous versus intravenous antibiotic prophylaxis for laparoscopic colorectal resection.

BACKGROUND: The use of oral prophylactic antibiotics for the prevention of surgical-site infection (SSI) in patients undergoing laparoscopic surgery for colorectal cancer is controversial. The aim of this RCT was to evaluate whether intravenous perioperative antibiotics are inferior to combined preoperative oral and perioperative intravenous antibiotics in this setting. METHODS: Patients undergoing elective laparoscopic colorectal resection in a single cancer centre were assigned randomly to combined preoperative oral antibiotics (metronidazole and kanamycin) and perioperative intravenous antibiotics (cefmetazole) (oral/IV group) or to perioperative intravenous antibiotics (cefmetazole) alone (IV-only group). Patients were stratified for the analyses based on type of operation (colonic surgery, anterior resection or abdominoperineal resection), preoperative use of mechanical bowel preparation, preoperative chemoradiotherapy and the presence of diabetes mellitus. The primary endpoint was the overall rate of SSI. Secondary endpoints were the rates of incisional site infection, organ/space infection, anastomotic leakage, intra-abdominal abscess, adverse events and postoperative complications. RESULTS: Of 540 patients offered participation in the trial in 2013-2014, 515 agreed to take part and were randomized. Some 256 patients in the IV-only group and 255 in the oral/IV group completed the treatment per protocol. The overall rate of SSI was 7·8 per cent (20 of 256) in the IV-only group and 7·8 per cent (20 of 255) in the oral/IV group, confirming that perioperative administration of intravenous antibiotics alone was not inferior to the combined regimen (P = 0·017). There were no differences in rates of incisional site infection (5·5 versus 5·9 per cent respectively), organ/space infection (2·3 versus 2·0 per cent) or other secondary endpoints between the two groups. CONCLUSION: Intravenous perioperative antimicrobial prophylaxis alone is not inferior to combined preoperative oral and intravenous perioperative prophylaxis with regard to SSI in patients with colorectal cancer undergoing elective laparoscopic resection. Registration number: UMIN000019339 ( http://www.umin.ac.jp/ctr/).

Suppression of intestinal tumors by targeting the mitotic spindle of intestinal stem cells.

Human colorectal cancer is often initiated by the aberrant activation of Wnt signaling, notably following adenomatous polyposis coli (Apc) inactivation. Recent studies identified adult intestinal stem cells (ISCs) and demonstrated their role as the cells of origin for intestinal tumors. However, the early consequences of aberrant Wnt signaling activation remain to be fully elucidated. Here, using organoid cultures established from conditional knockout mice and in vitro gene ablation, we show that Apc inactivation led to aberrant ISC proliferation and the expansion of the crypt domain. This system was used to evaluate the potential of a cancer-related spindle protein, Tacc3, as a target of cancer therapy, as its disruption led to the suppression of tumor formation in an animal model of intestinal tumors. We found that Tacc3 is required for the proper mitosis of Apc-deficient ISCs, and its disruption significantly attenuated the expansion of the crypt domain. In vivo analysis of corresponding mutant mice demonstrated that Tacc3 disruption led to a significant decrease in tumor number and prolonged survival. These observations demonstrated that Tacc3 is a potential chemotherapeutic target for intestinal tumors by perturbing the aberrant cell proliferation of Apc-deficient ISCs and provides an opportunity for the development of novel cancer prevention and treatment.

Cancer emerging from the recurrence of sessile serrated adenoma/polyp resected endoscopically 5 years ago.

Since the serrated neoplastic pathway has been regarded as an important pathway of colorectal carcinogenesis, few reports have been published on clinical cases of cancer derived from sessile serrated adenoma/polyp, especially on recurrence after resected sessile serrated adenoma/polyp. An elderly woman underwent endoscopic mucosal resection of a flat elevated lesion, 30 mm in diameter, in the ascending colon; the histopathological diagnosis at that time was a hyperplastic polyp, now known as sessile serrated adenoma/polyp. Five years later, cancer due to the malignant transformation of the sessile serrated adenoma/polyp was detected at the same site. The endoscopic diagnosis was a deep invasive carcinoma with a remnant sessile serrated adenoma/polyp component. The carcinoma was surgically removed, and the pathological diagnosis was an adenocarcinoma with sessile serrated adenoma/polyp, which invaded the muscularis propria. The surgically removed lesion did not have a B-RAF mutation in either the sessile serrated adenoma/polyp or the carcinoma; moreover, the initial endoscopically resected lesion also did not have a B-RAF mutation. Immunohistochemistry confirmed negative MLH1 protein expression in only the cancer cells. Lynch syndrome was not detected on genomic examination. The lesion was considered to be a cancer derived from sessile serrated adenoma/polyp recurrence after endoscopic resection, because both the surgically and endoscopically resected lesions were detected at the same location and had similar pathological characteristics, with a serrated structure and low-grade atypia. Furthermore, both lesions had a rare diagnosis of a sessile serrated adenoma/polyp without B-RAF mutation. This report highlights the need for the follow-up colonoscopy after endoscopic resection and rethinking our resection procedures to improve treatment.

Laparoscopic salvage lateral pelvic lymph node dissection for locally recurrent rectal cancer.

AIM: The lateral pelvic lymph nodes are one of the major sites and sources of local recurrence (LR) after surgery for rectal cancer. Salvage lateral pelvic lymph node dissection (LPLD) is potentially curative, but the value of laparoscopic surgery in such cases is unknown. Our aim was to report the technical details of laparoscopic salvage LPLD for LR at these nodes after rectal cancer surgery. METHOD: The study was based on nine patients who underwent laparoscopic salvage LPLD for LR at the lateral pelvic lymph nodes after surgery for rectal cancer. The safety and feasibility of this procedure were determined. RESULTS: The median operation time was 381 min and the median estimated blood loss was 130 ml. There were no conversions. Adjacent structures removed en bloc were the pelvic plexus in four patients, the internal iliac artery in seven patients and the seminal vesicle in one patient. The median number of metastatic lymph nodes was 1 (range 1-11). CONCLUSION: Our novel technique of laparoscopic salvage LPLD for LR at the lateral pelvic lymph nodes is safe and feasible.

Male sexual function after laparoscopic total mesorectal excision.

AIM: The aim of this prospective study was to clarify the frequency of male sexual dysfunction after laparoscopic total mesorectal excision (LTME) and to examine the relationship between pelvic autonomic nerve (PAN) preservation status and functional outcomes. METHOD: Candidates for LTME were included in this study. PAN preservation status after LTME was examined in detail by video review. Patients completed a functional questionnaire (the International Index of Erectile Function) before and 3, 6 and 12 months after the operation. RESULTS: Twenty-six patients who underwent LTME were assessable. Detailed video reviews identified inadvertent PAN damage during surgery. PAN injury was observed in 11 cases (41%), including eight cases (32%) of inadvertent PAN damage (incomplete preservation group). There was a trend toward increasing inadvertent PAN injury rate in patients with high body mass index and large tumours. The results from all patients who underwent LTME showed no deterioration in total International Index of Erectile Function or its domain scores 12 months after surgery. In the incomplete preservation group, these scores temporarily decreased (3 and 6 months after surgery), but such deterioration was not observed in the complete preservation group. Most of the 12 patients with potentially active erectile function before the operation recovered this function, and only one patient (7%) with PAN injury was still judged as inactive 12 months after surgery. CONCLUSION: The proportion of patients with sexual dysfunction after LTME is low. With the enhanced visibility of the laparoscope, inadvertent PAN injury was detected in a significant number of cases and associated with transient deterioration of sexual function.

Identification of AFAP1L1 as a prognostic marker for spindle cell sarcomas.

Spindle cell sarcomas consist of tumors with different biological features, of which distant metastasis is the most ominous sign for a poor prognosis. However, metastasis is difficult to predict on the basis of current histopathological analyses. We have identified actin filament-associated protein 1-like 1 (AFAP1L1) as a candidate for a metastasis-predicting marker from the gene expression profiles of 65 spindle cell sarcomas. A multivariate analysis determined that AFAP1L1 was an independent factor for predicting the occurrence of distant metastasis (P=0.0001), which was further confirmed in another set of 41 tumors by a quantitative mRNA expression analysis. Immunohistochemical staining using paraffin-embedded tumor tissues revealed that the metastasis-free rate was significantly better in tumors negative for AFAP1L1 (P=0.0093 by log-rank test). Knocking down the AFAP1L1 gene in sarcoma cells resulted in inhibition of the cell invasion, and forced expression of AFAP1L1 in immortalized human mesenchymal stem cells induced anchorage-independent growth and increased cell invasiveness with high activity levels of matrix metallopeptidase. Furthermore, tumor growth in vivo was accelerated in AFAP1L1-transduced sarcoma cell lines. These results suggest that AFAP1L1 has a role in the progression of spindle cell sarcomas and is a prognostic biomarker.

Activation of the non-canonical Dvl-Rac1-JNK pathway by Frizzled homologue 10 in human synovial sarcoma.

We previously reported that Frizzled homologue 10 (FZD10), a member of the Wnt signal receptor family, was highly and specifically upregulated in synovial sarcoma and played critical roles in its cell survival and growth. We here report a possible molecular mechanism of the FZD10 signaling in synovial sarcoma cells. We found a significant enhancement of phosphorylation of the Dishevelled (Dvl)2/Dvl3 complex as well as activation of the Rac1-JNK cascade in synovial sarcoma cells in which FZD10 was overexpressed. Activation of the FZD10-Dvls-Rac1 pathway induced lamellipodia formation and enhanced anchorage-independent cell growth cells. FZD10 overexpression also caused the destruction of the actin cytoskeleton structure, probably through the downregulation of the RhoA activity. Our results have strongly implied that FZD10 transactivation causes the activation of the non-canonical Dvl-Rac1-JNK pathway and plays critical roles in the development/progression of synovial sarcomas.

Safety, tolerability, and pharmacokinetics of TAS-108 in normal healthy post-menopausal female subjects: a phase I study on single oral dose.

OBJECTIVES: The present study was conducted to evaluate the safety, tolerability, and pharmacokinetics of TAS-108 after ascending single oral doses and to analyse preliminarily the effect of food on the pharmacokinetics of TAS-108 in normal healthy post-menopausal female subjects. METHODS: Twelve healthy subjects participated in an open-label, ascending single-dose, alternating group, safety, tolerance, and pharmacokinetic study of TAS-108 administered orally to two groups of the subjects, one given alternating doses of 10, 40, 120 mg (group A) and the other of 20, 80, 160 mg (group B), in the fasting state. In addition, six subjects (group A) were administered an additional dose at 120 mg TAS-108 after food consumption. Plasma and urine samples for measurement of TAS-108 were analysed by validated analytical procedures using a liquid chromatographic method with tandem mass spectrometric detection (LC/MS/MS). RESULTS: There was no dose-dependent increase in any adverse events (AEs), and there were no serious AEs or deaths. TAS-108 was readily absorbed following oral administration of the 80-, 120- and 160-mg doses. Plasma TAS-108 levels steadily declined, generally in a mono-exponential manner, with overall mean t(1/2) values ranging from 3.04 to 4.43 h in the fasting groups. Administration of TAS-108 after a high-fat meal markedly increased the bioavailability of the drug. The mean C(max) and AUC(0--t) values increased after a high-fat breakfast by 182 and 191% compared with the fasting value respectively. CONCLUSIONS: In this escalating dose study of TAS-108, the drug was well tolerated by the participants. The maximum and systemic exposure to TAS-108 tended to increase with increasing dose and its bioavailability markedly increased after high-fat food intake.

Novel surgical repair with bilateral gluteus muscle patching for intractable rectovaginal fistula.

We created a novel surgical repair for intractable rectovaginal fistula and treated four patients who had previously undergone unsuccessful surgery. An X-shaped skin incision was made on the perineum, and then the rectum was carefully divided from the vagina. Defects of both the rectum and the vagina were closed with vertical mattress sutures. The external sphincter muscle also was approximated. The gluteus muscle was identified through another skin incision to the buttock, and cut at the attachment to the femur. Bilateral gluteus muscles were approximated at the midline of the perineum so that the vagina was sufficiently separated from the rectum. Established anorectal angle was 92.5 degrees (SD=6.4 degrees ). Mean resting pressure was 101.3 cm H2O (SD=13.1). All patients retained complete anal function without soiling. The unusual problem of erosion of the posterior vaginal wall with fistulation in a sexually active woman justifies greater efforts, and this surgical technique offers good prospects in this small group of patients.

Plasma concentrations of 5-fluorouracil and F-beta-alanine following oral administration of S-1, a dihydropyrimidine dehydrogenase inhibitory fluoropyrimidine, as compared with protracted venous infusion of 5-fluorouracil.

The pharmacokinetics and pharmacodynamics of oral S-1, a dihydropyrimidine dehydrogenase (DPD) inhibitory fluoropyrimidine, were compared with those of protracted venous infusion (PVI) of 5-fluorouracil (5-FU). In all, 10 patients with gastric cancer received PVI of 5-FU at a dose of 250 mg m(-2) day(-1) for 5 days. After a washout period of 9 days, the patients received two divided doses daily for 28 days. S-1 was administered orally at about 0900 and 1900 hours. The daily dose of S-1 in terms of tegafur was 80 mg day(-1) in patients with a body surface area (BSA) of <1.25 m(2), 100 mg day(-1) in those with a BSA of >or=1.25 m(2) to <1.5 m(2), and 120 mg day(-1) in those with a BSA of >or=1.5 m(2). Plasma concentrations of 5-FU and F-beta-alanine (FBAL) were measured for pharmacokinetic analysis, and the plasma uracil concentration was monitored as a surrogate marker of DPD inhibition (pharmacodynamic analysis) in the same patients on days 1-5 of PVI of 5-FU and on days 1-5 of oral S-1. The area under the curve (AUC(0-10 h)) of 5-FU on day 5 was 728+/-113 ng h ml(-1) for PVI of 5-FU and 1364+/-374 ng h ml(-1) for S-1. The median 5-FU PVI : S-1 ratio of the AUC(0-10 h) of 5-FU was 1.9. The AUC(0-10 h) of FBAL on day 5 of PVI of 5-FU was 9465+/-3225 ng h ml(-1), AUC(0-10 h), as compared with 1725+/-605 ng h ml(-1) on day 5 of S-1 treatment. The AUC(0-10 h) of uracil on day 5 was 252+/-60 ng h ml(-1) with PVI of 5-FU and 12 582+/-3060 ng h ml(-1) with S-1. The AUC(0-10 h) of FBAL was markedly lower and plasma uracil concentrations were significantly higher for S-1 than for PVI of 5-FU, clearly demonstrating the effect of DPD inhibition.

Effects of 5-fluorouracil on the drug-metabolizing enzymes of the small intestine and the consequent drug interaction with nifedipine in rats.

5-Fluorouracil (5-FU) is a widely used antineoplastic agent. 5-FU therapy often causes gastrointestinal toxicity, which is suppressed by concomitant administration of potassium oxonate (Oxo). Here, we investigated the effect of 5-FU on the small-intestinal drug-metabolizing enzymes, which play important roles in the first-pass metabolism of drugs, in rats, by enzyme measurements and immunoblot analyses. During repeated administration of a combination of 1-(2-tetrahydrofuryl)-5-fluorouracil, an oral 5-FU-derivative drug, and 5-chloro-2,4-dihydroxypyridine (FCD), an inhibitor of 5-FU degradation, the activities of 7-ethoxyresorufin-O-deethylase, testosterone 6beta-hydroxylase, 4-methylumbelliferone UDP-glucuronyltransferase, and 1-chloro-2,4-dinitrobenzene glutathione S-transferase decreased significantly on day 4, and the activity of NADPH-cytochrome P450 (CYP) reductase decreased significantly on day 7. These effects were found to be attributable to a reduction in the enzyme protein contents in the small-intestinal mucosa. The enzymatic alterations significantly increased the plasma concentrations of orally administered nifedipine, which was prevented by concomitant administration of Oxo with FCD. However, consecutive administration of FCD for 4 days did not cause any alterations in the activity of the hepatic CYP isozyme-supported testosterone hydroxylase. These results suggest that continuous exposure to 5-FU leads to a decrease in the activities of drug-metabolizing enzymes in the intestinal mucosa by decreasing their enzyme protein contents, and increases the plasma concentrations of orally administered nifedipine, and that the sensitivity of these enzymes to the drug is greater than that of the enzymes of the liver. These effects were prevented by concomitant administration of Oxo.

Involvement of microsomal cytochrome P450 and cytosolic thymidine phosphorylase in 5-fluorouracil formation from tegafur in human liver.

Recently, we have reported that tegafur, an anticancer agent, is biotransformed into active drug 5-fluorouracil (5-FU) by cytochromes P450 1A2, 2A6, and 2C8 in human liver microsomes (T. Komatsu et al., Drug Metab. Dispos, 28: 1457-1463, 2000). Because the conversion of tegafur into 5-FU has also been reported to be catalyzed by cytosolic thymidine phosphorylase (dThdPase), the involvement of human liver microsomes and cytosol and individual differences in 5-FU formation from tegafur were investigated. In 14 human samples, the mean rates of 5-FU formation in liver microsomes were 5-fold and 2-fold higher than those in liver cytosol at substrate concentrations of 100 microM and 1 mM tegafur, respectively. In the presence of 5-chloro-2,4-dihydroxypyridine, a dihydropyrimidine dehydrogenase inhibitor, the rates of 5-FU formation by the combination of liver microsomes and cytosol showed 5- and 3-fold interindividual differences at 100 microM and 1 mM tegafur, respectively. Kinetic analysis of human liver cytosolic 5-FU formation indicated an apparent higher Km value (16 +/- 4 mM) than that of liver microsomes (1.8 +/- 0.3 mM) with similar Vmax values. Human liver cytosolic 5-FU formation was confirmed to be catalyzed by dThdPase with correlation and chemical inhibition studies. These results suggested that 5-FU formation from tegafur in human liver was mainly catalyzed by microsomal P450 at low concentrations of tegafur, but the contribution of cytosolic 5-FU formation by dThdPase would be important at high concentrations.

Reversal of LRP-associated drug resistance in colon carcinoma SW-620 cells.

Resistance to multiple drugs is mediated by lung resistance-related protein (LRP) as well as P-glycoprotein (P-gp) and multidrug resistance protein (MRP). The levels of expression of LRP mRNA and LRP in a human colon carcinoma cell line, SW-620, were increased by the differentiation-inducing agent, sodium butyrate (NaB). Treatment of SW-620 cells with NaB for 2 weeks conferred resistance to adriamycin (ADM) and VP-16. The resistance was almost completely reversed by PAK-104P, a pyridine analog, but not by cepharanthine. ADM accumulated mainly in the nuclei of SW-620 cells not treated with NaB and in the cytoplasm of SW-620 cells treated with NaB. When the NaB-treated SW-620 cells were incubated with ADM in the presence of PAK-104P, the accumulation of ADM in nuclei was substantially increased. Isolated nuclei from untreated cells accumulated more ADM than nuclei from NaB-treated cells. Efflux of ADM from the nuclei isolated from NaB-treated cells was enhanced. PAK-104P and an antibody against LRP increased the accumulation of ADM in the isolated nuclei from NaB-treated cells, and inhibited the enhanced efflux of ADM from the nuclei. These findings suggest that at least in part, PAK-104P reverses LRP-mediated drug resistance by inhibiting the efflux of ADM from nuclei. PAK-104P may be useful for reversing MDR in tumors that overexpress LRP.

Bioactivation of tegafur to 5-fluorouracil is catalyzed by cytochrome P-450 2A6 in human liver microsomes in vitro.

Tegafur is a prodrug of 5-fluorouracil (5-FU) consisting of a new class of oral chemotherapeutic agents, tegafur/uracil and S-1, which are classified as dihydropyrimidine dehydrogenase inhibitory fluoropyrimidines. It is bioactivated to 5-FU via 5'-hydroxylation mediated by cytochrome P-450 (CYP). However, which isoform(s) of CYP is responsible for the bioactivation process of tegafur remains unclear. The purpose of the present study was to identify the human CYP isoform(s) involved in the metabolic activation of tegafur using human liver microsomes and cDNA-expressed human CYPs. The formation of 5-FU from tegafur in human liver microsomes showed biphase kinetics with Km and Vmax values for the high-affinity component of 0.43 +/- 0.05 mM and 4.02 +/- 1.70 nmol/mg/min (mean +/- SD, n = 4), respectively. In the correlation study using a panel of 10 human liver microsomes, the formation of 5-FU from tegafur showed a significant correlation (r = 0.98; P < 0.001) with coumarin 7-hydroxylation, a marker activity of CYP2A6. In addition, a specific substrate of CYP2A6 and anti-CYP2A6 antibody inhibited the formation of 5-FU by 90% in human liver microsomes. Moreover, cDNA-expressed CYP2A6 showed the highest activity for the formation of 5-FU among 10 cDNA-expressed CYPs, with a Km value similar to that found for the high-affinity component in human liver microsomes. These findings clearly suggest that CYP2A6 is a principal enzyme responsible for the bioactivation process of tegafur in human liver microsomes. However, to what extent the bioactivation of tegafur by CYP2A6 accounts for the formation of 5-FU in vivo remains unclear, because the formation of 5-FU from tegafur is also catalyzed by the soluble fraction of a 100,000 x g supernatant and also derived from spontaneous degradation of tegafur.

Tissue distribution and biotransformation of potassium oxonate after oral administration of a novel antitumor agent (drug combination of tegafur, 5-chloro-2,4-dihydroxypyridine, and potassium oxonate) to rats.

S-1, a new oral 5-fluorouracil (5-FU)-derivative antitumor agent, is composed of tegafur, 5-chloro-2,4-dihydropyridine, and potassium oxonate (Oxo). Oxo, which inhibits the phosphorylation of 5-FU, is added to reduce the gastrointestinal (GI) toxicity of the agent. In this study, we investigated the tissue distribution and the metabolic fate of Oxo in rats after oral administration of S-1. Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU, but little distributed to other tissues, including tumorous ones in which 5-FU was observed after oral administration of S-1. Plasma concentration-time profiles of Oxo and its metabolites after i.v. and oral administration of S-1 revealed that Oxo was mainly converted to cyanuric acid in the GI tract. Furthermore, the analysis of drug-related radioactivity in GI contents and in vitro studies suggested that Oxo was converted to cyanuric acid by two routes, the first being direct conversion by the gut flora in the cecum, and the second, conversion by xanthine oxidase or perhaps by aldehyde oxidase after degradation to 5-azauracil (5-AZU) by the gastric acid. These results indicate that, although a part of the administered Oxo was degraded in the GI tract, Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU and that little was distributed to other tissues, including tumors. We conclude that this is the reason why Oxo suppresses the GI toxicity of 5-FU without affecting its antitumor activity.

[Multiple exostoses].

Multiple exostoses is a hereditary disease characterized by multiple osteocartilagenous tumors, of which the histological structures are similar to those of normal epiphyses. Genetic linkage has identified three different loci for this disease: EXT1 on 8q, EXT2 on 11p, and EXT3 on 19p. The EXT1 and EXT2 genes were recently isolated and mutation analyses have been performed in a number of patients with different ethnic backgrounds. The data indicate that mutations of these genes occurred in broad regions of each gene, and the loss-of-function mutations were predominant, although there were some missense mutations that may create functionally defective protein. Tumor cells were shown to be homozygous for the mutant allele, which is consistent with the concept of these genes as tumor suppressor genes. Recent progress for the functional analyses has disclosed that these genes encode the protein with glycosyltransferase activity and regulate the diffusion of Hedgehog protein, which is the key molecule for the skeletal development. Further analyses of these genes may provide us with the knowledge for the development of epiphyses, and may open the new research field for the regeneration of epiphyses.

[Comparison of pharmacokinetics of 5-FU and alpha-fluoro-beta-alanine, a metabolite of 5-FU, in plasma after administration of UFT, tegafur, 5-FU or doxifluridine to rats].

Toxic effects (neurotoxicity and cardiotoxicity) of 5-FU and its derivatives have been reported by many investigators. These toxicities are considered to be caused by the inhibition of the TCA cycle by alpha-fluoro-beta-alanine (FBAL), a metabolite of 5-FU, and later metabolites. In this study, we focused on FBAL as an index of the above toxicities. We compared the concentrations of 5-FU and FBAL in plasma after administration of UFT, tegafur (FT), 5-FU or doxifluridine (5'-DFUR) to rats (75 mumol/kg) in order to evaluate which compound has the better balance of efficacy and toxicity. UFT exhibited the lowest FBAL concentration in plasma followed by FT, 5'-DFUR and 5-FU. The ratio of FBAL to 5-FU in Cmax and AUC after dosing of UFT was the lowest among these four test compounds. These data indicate that the lowest ratio of FBAL to 5-FU resulted from the inhibitory effect of uracil, a component of UFT, on the metabolism of 5-FU. In conclusion, the present results suggest that UFT has a better balance of efficacy and toxicity than FT, 5-FU and 5'-DFUR.

Reduction of 5-fluorouracil (5-FU) gastrointestinal (GI) toxicity resulting from the protection of thymidylate synthase (TS) in GI tissue by repeated simultaneous administration of potassium oxonate (Oxo) in rats.

PURPOSE: An important cytotoxic effect of 5-fluorouracil (5-FU) is the inactivation of thymidylate synthase (TS) (EC 2.1.1.45) activity by the formation of a ternary complex consisting of covalently bound 5-fluorodeoxyuridine 5'-monophosphate (FdUMP), TS and 5,10-methylenetetrahydrofolate (CH2FH4). The gastrointestinal (GI) toxicity of 5-FU is also caused by its phosphorylation in the GI tract. Potassium oxonate (O(XO)) competitively inhibits pyrimidine phosphoribosyltransferase (EC 2.4.2.10), which converts 5-FU to 5-fluorouridine 5'-monophosphate (FUMP) in vitro. In this study the benefits of combining Oxo and tegafur (FT), which is a masked compound of 5-FU, in reducing the GI toxicity of 5-FU and in protecting the activity of TS in the normal GI tissues were evaluated. METHODS: We administered orally a preparation of 1 M FT and 0.4 M 5-chloro-2,4-dihydroxypyridine (CDHP) with or without 1 M O(XO) (called S-1 and FT + CDHP, respectively) or vehicle only (control) to rats for ten consecutive days and compared the toxicity, the histopathological findings and the free TS activity in the GI tissues of the treated rats. RESULTS: During the experimental periods, the signs of toxicity, such as a decrease in body weight, diarrhea and death, were only observed in the rats treated with FT + CDHP. The histopathological findings in the ileum and colon samples from rats treated consecutively with S-1 on day 1, day 4, day 7 and day 10 were less frequent and more mild than in the samples from rats treated with FT + CDHP. Furthermore, the free TS activities in the ileum samples of rats given S-1 and FT + CDHP were significantly decreased compared with the activity in samples from the control rats throughout the experimental periods. The free TS activities in GI tissues of rats treated with S-1 were higher than the TS activities in tissues from rats treated with FT + CDHP daily from day 4 to day 10, although activities in S-1-treated rat were decreased to almost same low levels as in FT + CDHP-treated rats on day 1. CONCLUSIONS: Our results suggest that repeated simultaneous administration of Oxo and FT can effectively protect the activity of TS by decreasing FdUMP via FUMP from 5-FU in GI tissue, and may lead to a reduction in GI toxicity.