Induction by 5-fluorouracil of a major phase difference in the circadian profiles of DNA synthesis between the Ehrlich ascites carcinoma and five normal organs

Reactive Oxygen Species Induced p53 Activation: DNA Damage, Redox Signaling, or Both?

Significance: The p53 tumor suppressor has been dubbed the "guardian of genome" because of its various roles in the response to DNA damage such as DNA damage repair, cell cycle arrest, senescence, and apoptosis, all of which are in place to prevent mutations from being passed on down the lineage. Recent Advances: Reactive oxygen species (ROS), for instance hydrogen peroxide derived from mitochondrial respiration, have long been regarded mainly as a major source of cellular damage to DNA and other macromolecules. Critical Issues: More recently, ROS have been shown to also play important physiological roles as second messengers in so-called redox signaling. It is, therefore, not clear whether the observed activation of p53 by ROS is mediated through the DNA damage response, redox signaling, or both. In this review, we will discuss the similarities and differences between p53 activation in response to DNA damage and redox signaling in terms of upstream signaling and downstream transcriptional program activation. Future Directions: Understanding whether and how DNA damage and redox signaling-dependent p53 activation can be dissected could be useful to develop anti-cancer therapeutic p53-reactivation strategies that do not depend on the induction of DNA damage and the resulting additional mutational load.

In vitro and in vivo evaluation of macromolecular prodrug GC-FUA based nanoparticle for hepatocellular carcinoma chemotherapy

A novel type of macromolecular prodrug delivery system is reported in this research. The N-galactosylated-chitosan-5-fluorouracil acetic acid conjugate (GC-FUA) based nanoparticle delivery system was evaluated in vitro and in vivo. Biocompatibility of GC-FUA-NPs was screened by BSA adsorption test and hemolysis activity examination in vitro. Cytotoxicity and cellular uptake study in HepG2 and A549 cells demonstrated that compared to free 5-Fu, the GC-FUA-NPs play great function in killing cancer cells for the cell endocytosis mediated by asialoglycoprotein receptor (ASGPR), which overexpresses on the cell surface. Pharmacokinetics study further illustrated that the drug-loaded nanoparticles has a much longer half-time than free 5-Fu in blood circulation in Sprague-Dawley (SD) rats. Tissue distribution was investigated in Kunming mice, and the result showed that the GC-FUA-NPs have a long circulation effect. The obtained data suggested that GC-FUA-NP is a very promising drug delivery system for efficient treatment of hepatocellular carcinoma.

Nanoformulations for therapy of pancreatic and liver cancers

Pancreatic and liver cancers often have poor prognoses. Clinically, pancreatic and liver cancer requires early diagnosis, and surgery is often associated with tumor recurrence. Currently, chemotherapies are limited in their ability to accurately target the tumors, and are associated with significant toxicity in patients. Targeting of chemotherapy can be improved by encapsulation in nanocarriers. A variety of preclinical studies indicate relatively superior therapeutic outcomes compared with drug alone therapy. Targeted nanoparticle imaging agents may also additionally facilitate better diagnosis and improve patient outcomes. This review discusses the nanoformulations that are under investigation (mainly preclinical studies, but also with some current clinical trial examples) against pancreatic and liver cancers, understands the challenges and provides future perspectives.

5-Fluorouracil nanoparticles inhibit hepatocellular carcinoma via activation of the p53 pathway in the orthotopic transplant mouse model

Biodegradable polymer nanoparticle drug delivery systems provide targeted drug delivery, improved pharmacokinetic and biodistribution, enhanced drug stability and fewer side effects. These drug delivery systems are widely used for delivering cytotoxic agents. In the present study, we synthesized GC/5-FU nanoparticles by combining galactosylated chitosan (GC) material with 5-FU, and tested its effect on liver cancer in vitro and in vivo. The in vitro anti-cancer effects of this sustained release system were both dose- and time-dependent, and demonstrated higher cytotoxicity against hepatic cancer cells than against other cell types. The distribution of GC/5-FU in vivo revealed the greatest accumulation in hepatic cancer tissues. GC/5-FU significantly inhibited tumor growth in an orthotropic liver cancer mouse model, resulting in a significant reduction in tumor weight and increased survival time in comparison to 5-FU alone. Flow cytometry and TUNEL assays in hepatic cancer cells showed that GC/5-FU was associated with higher rates of G0-G1 arrest and apoptosis than 5-FU. Analysis of apoptosis pathways indicated that GC/5-FU upregulates p53 expression at both protein and mRNA levels. This in turn lowers Bcl-2/Bax expression resulting in mitochondrial release of cytochrome C into the cytosol with subsequent caspase-3 activation. Upregulation of caspase-3 expression decreased poly ADP-ribose polymerase 1 (PARP-1) at mRNA and protein levels, further promoting apoptosis. These findings indicate that sustained release of GC/5-FU nanoparticles are more effective at targeting hepatic cancer cells than 5-FU monotherapy in the mouse orthotropic liver cancer mouse model.

Enhanced absorption of 3-O-methyl glucose following gastrointestinal injury induced by repeated oral administration of 5-FU in mice

The absorption of nutrients is mainly mediated by specific carriers and generally retarded following gastrointestinal injury. The aim of this study was to assess the effect of repeated oral administration of 5-fluorouracil (5-FU) on the intestinal absorption of glucose by using 3-O-methyl-D-glucose (3-OMG), a glucose analogue that is not metabolized, as a probe. Repeated administration of 5-FU (60 mg/kg/day for 3 days) readily induced intestinal mucosal injury assessed by visual observation and loss of intestinal wet weight. At the same time, the carrier-dependent absorption clearance of 3-OMG was increased 1.8-fold, while the carrier-independent absorption assessed by L-glucose transport was not affected. Phloretin, a glucose transporter 2 (GLUT2) inhibitor, completely abolished the absorption of 3-OMG in both control and 5-FU-treated mice, indicating the specific effect on the carrier-dependent process. Protein and mRNA expressions of GLUT2 were significantly higher in 5-FU-treated mice compared to the control mice. Sodium (Na(+)) glucose co-transporter 1 (SGLT1) expressions were also moderately elevated in 5-FU-treated mice. Concomitantly, the uptake of D-glucose into both isolated brush border and basolateral membrane vesicles was significantly increased. These results indicate that repeated oral administration of 5-FU did not hamper, but unexpectedly induced, SGLT1 and GLUT2 expression to enhance glucose absorption.

Circadian rhythms and cancer chemotherapy

Experimental and clinical pertinent data regarding circadian rhythmicities are reviewed in (1) target tissues, i.e., healthy tissues (actively proliferating or not) and tumor tissues, (2) pharmacology of anticancer agents, (3) toxicity and tolerance of these agents and (4) antitumor activity of cancer chemotherapy. The basic concepts of chronotolerance and/or of chronoefficacy have brought new hopes for further amelioration in the management of cancer patients. Quite recent published Phase II and III clinical trials have demonstrated that new improvements on the therapeutic index have been achieved through ambulatory chronotherapy for various solid tumors.

DNA synthetic activity in tumor-bearing mice

The rate of DNA synthesis in normal tissues exhibits circadian rhythmicity. However, there have been conflicting reports of the effects of tumor burden on the circadian rhythm of DNA synthesis in non-cancer tissues. We have developed a mouse colon cancer (MC-26) that exhibits different growth under different photoperiods. The purpose of this study was to analyze DNA synthetic activity in tissues removed from tumor-bearing and tumor-free mice maintained under two different photoperiods. Two groups each of approximately 80 male Balb/c mice were acclimated to one of two light-dark cycles, 12L:12D or 6L:18D. Half of each group were injected with 5.0 x 10(4) MC-26 cells. Twenty-two days later, all mice were killed in subgroups at 4-6 hr intervals over one 24-hr period. Colons and tumors were removed for measurement of DNA synthesis. Results were analyzed by means of one-way analysis of variance (ANOVA) in order to determine whether DNA synthesis varied significantly within groups over the 24-hr period. The DNA synthetic activity, as measured by uptake of tritiated thymidine, exhibited significant temporal variation in the colons of control (tumor-free) mice under both the 12L:12D and 6L:18D photoperiods. The colons of tumor-bearing mice failed to exhibit a fluctuation under a 12L:12D photoperiod but did show a significant 24-hr rhythm under the 6L:18D photoperiod. The subcutaneously growing cancers did not exhibit a circadian variation in DNA synthetic activity under either photoperiod. Both photoperiod and the presence of cancer appear to affect the DNA synthetic activity observed in mice bearing the MC-26 colon cancer.

Biological time and the effects of hydroxyurea on DNA synthetic activity of bone marrow and tumor cells in mice bearing the Ehrlich ascites carcinoma

The objective of this experiment was to attempt to induce, with hydroxyurea (HU), significant quantitative differences in the level of DNA-synthetic activity (DNA-SA) between a neoplastic cell population (the Ehrlich ascites carcinoma or EAC) and bone marrow in the same animal. Mice bearing a 5-day-old EAC were standardized to and kept on an LD 12:12 cycle (light 0600-1800 hr). They were treated with 500 mg/kg HU at 0500 hr (23 hr after lights on, or HALO) or at 1700 hr (11 HALO). DNA-SA was determined by liquid scintillation counting of 3H-thymidine incorporation into chemically isolated DNA. DNA-SA in bone marrow and EAC cells was monitored over the next 60 hr with subgroups of ten mice each killed every 3 hr beginning 3 hr after treatment with HU. The circadian system of the host influenced the response of the bone marrow to HU; i.e., the response to HU administered at 0500 hr was different both qualitatively and quantitatively from that for HU given at 1700 hr. Comparisons of DNA-SA in bone marrow and EAC from the same animal revealed time points after treatment with HU when DNA-SA in the EAC was high, but DNA-SA in bone marrow was low. These differences in the level of DNA-SA between a tumor cell population and bone marrow should be of therapeutic value; i.e., executor doses of anti-DNA-SA drugs such as cytosine arabinoside could be given at that point in time after treatment with HU when DNA-SA in the tumor was high, but DNA-SA in the bone marrow was low.