Tissue distribution of [18F]-5-fluorouracil in mice: effects of route of administration, strain, tumour and dose

Tubular dysfunction impairs renal excretion of pseudouridine in diabetic kidney disease

Plasma nucleosides-pseudouridine (PU) and N2N2-dimethyl guanosine (DMG) predict the progression of type 2 diabetic kidney disease (DKD) to end-stage renal disease, but the mechanisms underlying this relationship are not well understood. We used a well-characterized model of type 2 diabetes (db/db mice) and control nondiabetic mice (db/m mice) to characterize the production and excretion of PU and DMG levels using liquid chromatography-mass spectrometry. The fractional excretion of PU and DMG was decreased in db/db mice compared with control mice at 24 wk before any changes to renal function. We then examined the dynamic changes in nucleoside metabolism using in vivo metabolic flux analysis with the injection of labeled nucleoside precursors. Metabolic flux analysis revealed significant decreases in the ratio of urine-to-plasma labeling of PU and DMG in db/db mice compared with db/m mice, indicating significant tubular dysfunction in diabetic kidney disease. We observed that the gene and protein expression of the renal tubular transporters involved with nucleoside transport in diabetic kidneys in mice and humans was reduced. In conclusion, this study strongly suggests that tubular handling of nucleosides is altered in early DKD, in part explaining the association of PU and DMG with human DKD progression observed in previous studies.NEW & NOTEWORTHY Tubular dysfunction explains the association between the nucleosides pseudouridine and N2N2-dimethyl guanosine and diabetic kidney disease.

Targeting Colorectal Cancer with Conjugates of a Glucose Transporter Inhibitor and 5-Fluorouracil

Overexpression of glucose transporters (GLUTs) in colorectal cancer cells is associated with 5-fluorouracil (1, 5-FU) resistance and poor clinical outcomes. We designed and synthesized a novel GLUT-targeting drug conjugate, triggered by glutathione in the tumor microenvironment, that releases 5-FU and GLUTs inhibitor (phlorizin (2) and phloretin (3)). Using an orthotopic colorectal cancer mice model, we showed that the conjugate exhibited better antitumor efficacy than 5-FU, with much lower exposure of 5-FU during treatment and without significant side effects. Our study establishes a GLUT-targeting theranostic incorporating a disulfide linker between the targeting module and cytotoxic payload as a potential antitumor therapy.

Patient Derived Models to Study Head and Neck Cancer Radiation Response

Patient-derived model systems are important tools for studying novel anti-cancer therapies. Patient-derived xenografts (PDXs) have gained favor over the last 10 years as newer mouse strains have improved the success rate of establishing PDXs from patient biopsies. PDXs can be engrafted from head and neck cancer (HNC) samples across a wide range of cancer stages, retain the genetic features of their human source, and can be treated with both chemotherapy and radiation, allowing for clinically relevant studies. Not only do PDXs allow for the study of patient tissues in an in vivo model, they can also provide a renewable source of cancer cells for organoid cultures. Herein, we review the uses of HNC patient-derived models for radiation research, including approaches to establishing both orthotopic and heterotopic PDXs, approaches and potential pitfalls to delivering chemotherapy and radiation to these animal models, biological advantages and limitations, and alternatives to animal studies that still use patient-derived tissues.

Fabrication and Use of Poly(d,l-lactide-co-glycolide)-Based Formulations Designed for Modified Release of 5-Fluorouracil

5-fluorouracil (5-FU) is a chemotherapeutic agent that has been used for the treatment of a variety of malignancies since its initial introduction to the clinic in 1957. Owing to its short biological half-life, multiple dosings are generally required to maintain effective 5-FU plasma concentrations throughout the therapeutic period. Clinical studies have shown that continuous 5-FU administration is generally superior to bolus injection as exhibited by lower toxicities and increased therapeutic efficacy. Optimal therapeutic efficacy, however, is often compromised by the limiting therapeutic index. Whilst oral formulations are also used, these suffer from the drawbacks of variable bioavailability and first-pass metabolism. As a result, sustained release formulations of 5-FU have been investigated in an effort to mimic the kinetics of continuous infusion particularly for situations where local delivery is considered appropriate. The biocompatible, biodegradable, and highly tunable synthetic polymer, poly(d,l-lactide-co-glycolide) (PLGA), is widely used as a vector for sustained drug delivery, however, issues such as insufficient loading and inappropriate burst release kinetics have dogged progress into the clinic for small hydrophilic drugs such as 5-FU. This review provides introductory information about the mechanism of action, pharmacokinetic and physicochemical properties, and clinical use of 5-FU that have contributed to the development of PLGA-based 5-FU release platforms. In addition, this review provides information on fabrication methods used for a range of 5-FU-loaded PLGA formulations and discusses factors affecting the release kinetics of 5-FU as well as the in vitro and in vivo antitumor or antiproliferative efficacy of these platforms.

Multicomponent 5-fluorouracil loaded PAMAM stabilized-silver nanocomposites synergistically induce apoptosis in human cancer cells

Herein, we report the development of a poly(amidoamine) (PAMAM) dendrimer based multicomponent therapeutic agent forin vitrocancer therapy applications.

Selenium nanoparticles as a carrier of 5-fluorouracil to achieve anticancer synergism

A simple method for preparing 5-fluorouracil surface-functionalized selenium nanoparticles (5FU-SeNPs) with enhanced anticancer activity has been demonstrated in the present study. Spherical SeNPs were capped with 5FU through formation of Se-O and Se-N bonds and physical adsorption, leading to the stable structure of the conjugates. 5FU surface decoration significantly enhanced the cellular uptake of SeNPs through endocytosis. A panel of five human cancer cell lines was shown to be susceptible to 5FU-SeNPs, with IC(50) values ranging from 6.2 to 14.4 μM. Despite this potency, 5FU-SeNP possesses great selectivity between cancer and normal cells. Induction of apoptosis in A375 human melanoma cells by 5FU-SeNPs was evidenced by accumulation of sub-G1 cell population, DNA fragmentation, and nuclear condensation. The contribution of the intrinsic apoptotic pathway to the cell apoptosis was confirmed by activation of caspase-9 and depletion of mitochondrial membrane potential. Pretreatment of cells with a general caspase inhibitor z-VAD-fmk significantly prevented 5FU-SeNP-induced apoptosis, indicating that 5FU-SeNP induced caspase-dependent apoptosis in A375 cells. Furthermore, 5FU-SeNP-induced apoptosis was found dependent on ROS generation. Our results suggest that the strategy to use SeNPs as a carrier of 5FU could be a highly efficient way to achieve anticancer synergism. 5FU-SeNPs may be a candidate for further evaluation as a chemopreventive and chemotherapeutic agent for human cancers, especially melanoma.

X-ray structure of Salmonella typhimurium uridine phosphorylase complexed with 5-fluorouracil and molecular modelling of the complex of 5-fluorouracil with uridine phosphorylase from Vibrio cholerae

Uridine phosphorylase (UPh), which is a key enzyme in the reutilization pathway of pyrimidine nucleoside metabolism, is a validated target for the treatment of infectious diseases and cancer. A detailed analysis of the interactions of UPh with the therapeutic ligand 5-fluorouracil (5-FUra) is important for the rational design of pharmacological inhibitors of these enzymes in prokaryotes and eukaryotes. Expanding on the preliminary analysis of the spatial organization of the active centre of UPh from the pathogenic bacterium Salmonella typhimurium (StUPh) in complex with 5-FUra [Lashkov et al. (2009), Acta Cryst. F65, 601-603], the X-ray structure of the StUPh-5-FUra complex was analysed at atomic resolution and an in silico model of the complex formed by the drug with UPh from Vibrio cholerae (VchUPh) was generated. These results should be considered in the design of selective inhibitors of UPhs from various species.

5-Fluorouracil catabolism to 5-fluoro-5,6-dihydrouracil is reduced by acute liver impairment in mice

This study investigated the effect of acute liver damage on the inactivation of 5-fluorouracil (5-FU) to its main catabolite 5-fluoro-5,6-dihydrouracil (5-FUH2) in mice. Plasma pharmacokinetics of 5-FU and 5-FUH2 in mice receiving 5-FU (10, 30, and 90 mg/kg) were compared to those in mice pretreated with carbon tetrachloride and receiving the same 5-FU doses. Carbon tetrachloride-induced hepatic damage was histopathologically examined under light microscopy and serum transaminases and dihydropyrimidine dehydrogenase activities were also measured. Liver histopathology and elevated aminotransferase activity levels confirmed the presence of liver damage. 5-FU C(max) and AUC both increased up to 71% in mice with liver damage. This was reflected by decreased 5-FUH2 production, since 5-FUH2 C(max) and AUC levels decreased up to 47% and 61%, respectively. Metabolic ratios between 5-FUH2 and 5-FU AUCs were considerably decreased as well, further suggesting that liver damage caused a reduction in 5-FU catabolism. DPD activity was not altered in damaged livers. The present results indicate that 5-FU disposition in mice could be profoundly altered in the presence of severe liver impairment, potentially leading to enhanced anabolic activation of 5-FU. This effect seems to be ascribed to a reduction of viable hepatocytes, rather than to an inactivation of DPD activity.

Assessment of the biodistribution and metabolism of 5-fluorouracil as monitored by 18F PET and 19F MRI: a comparative animal study

The effective clinical use of the anticancer drug 5-fluorouracil (5-FU) requires the non-invasive assessment of its transport and metabolism, particularly in the tumor and the liver, where the drug is catabolized to alpha-fluoro-beta-alanine (FBAL). In this study, the potentials and limitations of dynamic 18F PET and metabolic 19F MRI examinations for noninvasive 5-FU monitoring were investigated in ACI and Buffalo rats with transplanted MH3924A and TC5123 Morris hepatomas, respectively. Selective 5-[19F]FU and [19F]FBAL MR images were acquired 5 and 70 min after 5-FU injection using a CHESS MRI sequence. After administration of 5-[18F]FU, the kinetics of the regional 5-[18F]FU uptake were measured by dynamic PET scanning over 120 min. To allow a comparison between PET and MRI data, standardized uptake values (SUV) were computed at the same points in time. The TC5123 hepatoma showed a significantly (p < 0.002) higher mean SUV at 5 and 70 min post-5-FU injection than the MH3924A cell lines, whereas there were no significant differences between the mean SUV measured in the liver of both animal populations. In contrast to the PET data, no significant differences in the mean 5-[19F]FU and [19F]FBAL MR signal values in the tumor of both models were observed. The MR images, however, yielded the additional information that 5-FU is converted to FBAL only in the liver and not in the hepatomas.

18F-radiopharmacokinetics of [18F]-5-fluorouracil in a mouse bearing two colon tumors with a different 5-fluorouracil sensitivity: a study for a correlation with oncological results

The tissue distribution and biodynamics of 18F-labelled 5-fluorouracil (FU) are described and studied for correlation with its in vivo antitumor activity. The in vivo model consisted of Balb/c mice bearing a FU sensitive (Colon 26-10 carcinoma) tumor in the left and a less responsive (Colon 26 carcinoma) tumor in the right abdominal side of the animal. Distribution and efflux of 18F-label from tumor, blood, and other tissues were determined by obduction at 0.5, 1, 2, 4, and 6 h postintravenous injection. For a comparison, the 18F-labeled 5-fluoro-6-hydroxy and cis-5-fluoro-6-ethoxy uracil adducts were studied in the same in vivo model. For 18F-FU it was found that the 18F-label tumor kinetics rapidly fell into a biphasic mode: a relatively short 18F beta phase (18F t1/2 beta 21 +/- 3 min), linked with the total body metabolic capacity and clearance of the animal, and a longer 18F gamma phase, linked with the intrinsic intratumoral FU metabolism (Colon 26-10: 18F t1/2 gamma 10.3 h; Colon 26: 18F t1/2 gamma 5.6 h). It is proposed that the observed faster 18F efflux of the less responsive Colon 26 corresponds to an enhanced breakdown of 5-fluoronucleotides to 5-fluoronucleosides and subsequent elimination from the tumor cells. It is concluded that on PET scanning, measurement of the dynamic 18F t1/2 gamma and 18F t1/2 beta parameter is of prime importance for an insight in the in vivo tumor biology of a patient.

Prolonged retention of high concentrations of 5-fluorouracil in human and murine tumors as compared with plasma

Concentrations of 5-fluorouracil (5-FU) and its active metabolite 5-fluoro-2'-deoxy-5'-monophosphate (FdUMP) were measured in biopsy specimens of tumor tissue, normal mucosa, metastatic liver nodules, and normal liver tissue obtained from 39 patients and in two murine colon tumors (colon 26 and colon 38) after a single injection of 5FU at a therapeutic dose (500 mg/m2 and 100 mg/kg, respectively). These data were compared with plasma concentrations. Peak plasma concentrations (300-500 microM) of 5FU were comparable in human and murine plasma. The half-life of plasma elimination (during the period from 15 to 120 min) in both mouse and man ranged from 10 to 20 min, whereas at between 2 and 8 h, plasma concentrations varied from 0.1 to 1 microM, the half-life being about 100 min. In both species, 5FU could be measured in plasma at concentrations ranging from 0.01 to 1 microM for several days after 5FU treatment. 5FU concentrations in tissue samples obtained from 14 patients were measured during the time range of 1-6 h, those in samples taken from 7 patients, during the interval of 19-27 h; and those in samples obtained from 18 patients, within the interval of 40-48 h after injection. 5FU tumor concentrations varied between 0.78-21.6, 0.44-6.1, and 0.17-10.8 mumol/kg wet wt., respectively. Some of the 48-h samples were obtained from patients who had received leucovorin plus 5FU; coadministration of leucovorin did not alter 5FU tissue concentrations. At between 4 and 48 h, the tissue concentration/plasma concentration ratio was at least 10. 5FU concentrations in murine tumors were measured for up to 10 days after 5FU administration, with plateau 5FU tumor concentrations being about 50 mumol/kg wet wt. in colon 38 and about 200 mumol/kg wet wt. in colon 26 at 2 h after treatment; after 4 days, values of 0.5 and 4.8 mumol/kg, respectively, were obtained and after 10 days, respective concentrations of 0.1 and 0.07 mumol/kg were detected. The FdUMP concentrations measured in colon 26 and colon 38 tumors were 214 and 46 pmol/g, respectively, at 2 h after 5FU administration, and these values subsequently decreased to about 15 pmol/g in both tumors. In human tumors the initial FdUMP concentration ranged from 10 to 1000 pmol/g; at later time points the level of FdUMP was just above the detection limit of the assay. In liver metastases, high 5FU concentrations seemed to be related to high levels of FdUMP, which was likely of importance for the antitumor effect.(ABSTRACT TRUNCATED AT 400 WORDS)