Evaluation of the porphyrinogenic risk of antineoplastics

The use of antineoplastics is common in cancer therapy, and some of them have been associated with the development of porphyria in patients with cancer. However, knowledge of their effects on the haeme metabolic pathway is at present scarce and unclear. So, the present study evaluates the porphyrinogenic ability of nine antineoplastics (both alkylating and non-alkylating). These were tested either alone or in conjunction with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (latent porphyria model) in chick embryos and in mice. The results obtained suggest that the use of cyclophosphamide, azathioprine, 5-fluorouracil, busulphan, procarbazine and hexamethylmelamine be avoided in the treatment of porphyric patients. On the other hand, dacarbazine, chlorambucil and melphalan are non-porphyrinogenic. We also provide evidence showing that neither the presence of the mustard group in the structure of the antineoplastic nor alterations in ferrochelatase or protoporphyrinogen oxidase activities are responsible for the porphyrinogenic ability of cyclophosphamide.

Myelosuppression in the pig (Sus scrofa): uteroferrin reduces the myelosuppressive effects of 5-fluorouracil in young pigs

The present study investigated the ability of uteroferrin to modulate the myelosuppressive effects of 5-fluorouracil (5-FU) in young pigs (Sus scrofa). Pigs (28-35 days of age; n = 6 per treatment) were infused with equal amounts of 5-FU on days 0 and 1 of the experimental period (37.5 mg/kg cumulative dose). Uteroferrin (100 micrograms/kg in 0.9% NaCl) or control (equivalent volume of 0.9% NaCl) was administered to pigs as intramuscular injections twice daily (08:00 and 20:00 hr) on days 1 through 21. Peripheral blood cell number, composition and progenitor cells were determined over 28 days. Treatment of pigs with 5-FU resulted in a rapid dose-dependent (P < 0.05) leukocytopenia. Concurrent treatment of pigs with uteroferrin reduced (P < 0.05) the rate of 5-FU-induced leukocytopenia (44 vs 77 +/- 7% decline from baseline on day 3) and enhanced (P < 0.05), the recovery from 5-FU on days 10 and 12 postinfusion. The positive effect of uteroferrin on leukocytes resulted primarily from a protection and/or enhanced recovery of neutrophils and monocytes. In addition, uteroferrin attenuated (P < 0.05) the suppression of red blood cell numbers after 5-FU administration (6.9 vs 6.1 +/- 0.2 x 10(6) cells/microliter on day 3), an affect reflected in increased hematocrit and hemoglobin concentrations. The effects of uteroferrin appeared to result from enhancement of the proliferation and/or differentiation of primitive pluripotent stem cells resistant to 5-FU, as concurrent treatment of pigs with uteroferrin resulted in a protection and/or enhanced recovery (P < 0.05) of CFU-GEMM, CFU-GM and BFU-E progenitor cells in the peripheral blood. These results are the first to demonstrate that uteroferrin can reduce the myelosuppressive effects of 5-FU in the pig and suggest that uteroferrin has hematopoietic growth factor activity in vivo.

Modulation by conagenin of inflammatory mediator productions in mice given 5-fluorouracil

The effect of conagenin (CNG) on the production of the inflammatory mediators induced by 5-fluorouracil (5-Fu) in mice was investigated. We found that the production of interleukin (IL)-1 alpha and prostaglandin E2(PGE2) in whole spleen cell cultures from mice given a sublethal dose of 5-Fu was induced in the week after treatment, and subsequently the production of IL-4 and IL-IO was induced. The administration of 5-Fu and CNG suppressed the production of IL-1 alpha and PGE2, and induced the production of IL-4 and IL-10 earlier than 5-Fu alone did. In cultures of cells from Peyer's patches, IL-1 alpha production was suppressed by CNG administration. The effect of CNG was also demonstrated in vitro. CNG at 0.001 to 1.0 microgram/ml suppressed IL-1 alpha and PGE2 production in cultures of adherent peritoneal exudate cells (PEC) and cells from Peyer's patches of mice given 5-Fu. IL-10 production in cultures of non-adherent splenic cells was enhanced by CNG. These results indicate that CNG modulates inflammatory responses induced by 5-Fu through production of anti-inflammatory cytokines such as IL-4 and IL-10.

Fourteen-day oral combination dose toxicity study of CGS 16949 A (aromatase inhibitor) with 5-fluorouracil or tamoxifen in rats

CGS 16949A, an aromatase inhibitor, was administered orally to female rats at doses of 1 and 10 mg/kg/day alone and in combination with tamoxifen (0.5 or 5 mg/kg/day) or 5-fluorouracil (20 mg/kg/day) for 14 days. CGS 16949A and tamoxifen combination: Increased food intake and body weight noted after CGS 16949A treatment were also observed following combination treatment, though to a lesser degree. Most of the clinical pathological features noted following combination treatment were similar to those induced by single compound treatment. Gross pathological and histopathological changes ascribed to the antiestrogenic action of CGS 16949A, such as increased ovarian weight, decreased uterine weight, cystic follicles and atrophied uterus and vaginal epithelium, were alleviated by combination treatment, and were comparable in severity to those caused by tamoxifen alone. No severe toxic changes were induced by combination treatment. CGS 16949A and 5-fluorouracil combination: Increased body weight noted after CGS 16949A treatment was also observed following combination treatment, though to a lesser degree. Most of the changes caused by single compound treatment, including the aforementioned effects of CGS 16949A on the genital organs, were also noted following combination treatment. There was no evidence of enhancement of the effects by combination treatment.

Intestinal anaerobic bacteria hydrolyse sorivudine, producing the high blood concentration of 5-(E)-(2-bromovinyl)uracil that increases the level and toxicity of 5-fluorouracil

Sorivudine, 1-beta-D-arabinofuranosyl-5-(E)-(2-bromovinyl)uracil, is a potent antiviral agent against varicella-zoster virus and herpes simplex virus type 1. However, sorivudine should not be used in combination with anticancer drugs such as 5-fluorouracil (5-FU) because (E)-5-(2-bromovinyl)uracil (BVU), a metabolite of sorivudine, inhibits the degradation of 5-FU, resulting in its accumulation in the blood and marked enhancement of the toxicity of 5-FU. Since phosphorolytic enzymes generate BVU from sorivudine, we investigated the distribution of the enzyme activity in rats. High activity was found in the cecal and large intestinal contents, while very low or no detectable activity in the liver, kidney, stomach, cecum, large intestine, and the stomach and small intestinal contents. These results suggest that intestinal microflora play an important role in BVU production. Therefore, we measured the phosphorylase activity in cell-free extracts from 23 aerobes, 16 anaerobes and a fungus. Bacteroides species B. vulgatus, B. thetaiotaomicron, B. fragilis, B. uniformis and B. eggerthii, dominant members of intestinal microflora, had high activity to convert sorivudine to BVU. To elucidate the contribution of intestinal microflora to BVU production in vivo, we administered sorivudine to rats treated with several antibiotics and measured the BVU concentration in the serum of rats. When sorivudine was given to rats treated with ampicillin or a mixture of bacitracin, neomycin and streptomycin, which decreased the numbers of viable aerobes and anaerobes, only a small amount of BVU was found in the serum. BVU concentration in the serum of rats treated with metronidazole to decrease the number of intestinal anaerobes was also very low. In contrast, BVU concentration in the serum of rats treated with kanamycin, which was used to decrease the number of aerobes selectively, was higher than that of non-treated rats. These results also suggest that BVU is produced by intestinal anaerobic bacteria especially Bacteroides species in vivo.

Determinants of cytotoxicity with prolonged exposure to fluorouracil in human colon cancer cells

To explore the determinants of cytotoxicity during prolonged exposure to pharmacologically relevant concentrations of 5-fluorouracil (FUra), we studied the effects of FUra at concentrations ranging from 0.1 to 1 microM in HCT 116 and HT 29 colon cancer cells grown in the presence of physiologic levels of leucovorin. A 5- and 7-day exposure to 1 microM FUra reduced cell growth to 46% and 20% of control in HT 29 cells and to 74% and 38% of control in HCT 116 cells. Concurrent exposure to thymidine (10 or 20 microM) or uridine (1 mM) provided partial protection against FUra toxicity in HT 29 cells, but did not protect HCT 116 cells. After a 24-h exposure to 1 microM [3H]FUra, free 5-fluoro-2'-deoxyuridine-5' -monophosphate (FdUMP) and FUDP. + FUTP levels were 0.7 and 144 pmol/10(6) cells in HT 29 cells, respectively, and 3.9 and 178 pmol/10(6) cells in HCT 116 cells. FdUMP and FUDP + FUTP pools increased by 5.7- and 2.0-fold in HT 29 cells and by 1.7- and 3.3-fold in HCT 116 cells over the next 48 h, but did not accumulate thereafter. After a 24-h exposure to 1 microM [3H]FUra, FUra-RNA levels were 158 and 280 fmol/microgram in HT 29 and HCT 116 cells, respectively; FUra-RNA levels increased over time, and reached 700 and 1156 fmol/microgram at day 5. Concurrent exposure to 1 mM uridine for 72 h did not diminish [3H]FUra-RNA incorporation. Upon removal of [3H]FUra following a 24-h exposure, FUra-RNA levels remained relatively stable with 57-78% retained at 120 h. A low level of [3H]FUra-DNA incorporation was detected in HT 29 cells. Thymidylate synthase (TS) catalytic activity in control cells was 2-fold higher in HCT 116 cells compared to HT 29 cells (47 vs. 23 pmol/min/mg). Total TS content increased 1.5- to 3-fold over control in both cell lines during FUra exposure, and ternary complex formation was evident for up to 96 h-dTTP pools were not depleted in FUra-treated cells, suggesting that residual TS catalytic activity was sufficient to maintain dTTP pools relative to demand. Surprisingly, the partial inhibition of TS was accompanied by a striking accumulation of immunoreactive "dUMP" pools in both lines; dUTP pools also increased 2-to 3-fold. In summary, the gradual and stable accumulation of FUra in RNA noted in both lines may account for the thymidine-insensitive component of FUra toxicity. Because dTTP pools were not appreciably diminished, the interference with nascent DNA chain elongation and induction of single-strand breaks in newly synthesized DNA in both cell lines may be due to misincorporation of deoxyuridine nucleotides.

Phase II study of 5-fluorouracil and leucovorin in recurrent primary brain tumor

Thirty patients with recurrent primary brain tumors were treated with a combination of 5-fluorouracil and leucovorin. There were three responses seen. Toxicity consisted of stomatitis, diarrhea, and hematological suppression. 5-fluorouracil and leucovorin would appear to be minimally effective in recurrent brain tumors.

In vitro chemosensitivity of human pancreatic cancer cell lines

CONCLUSION

These results show that eight pancreatic cancer cell lines are broadly sensitive to CDDP, and that chemotherapy for pancreatic cancer may improve the prognosis by more effective drug delivery to cancer cells.

BACKGROUND

Chemotherapy for pancreatic cancer does not satisfactorily improve prognosis. The efficacy of chemotherapy depends on choosing sensitive anticancer drugs.

METHODS

The in vitro chemosensitivity of eight human pancreatic cancer cell lines was investigated. Growth inhibition was measured by 3H-thymidine incorporation assays for doxorubicin hydrochloride (ADM), mitomycin C (MMC), cisplatin (CDDP), and etoposide (VP-16), and by Alamar Blue assay for (AB assay) 5-fluorouracil (5-FU). The cells were exposed to ADM, MMC, CDDP, and VP-16 for 2 h, and 5-FU for 72 h. From the dose-response curves, the 50% growth inhibition (IC50) level for each drug was estimated.

RESULTS

The IC50 after 2 h of exposure of each of the eight kinds of cell lines to each anticancer drug ranged from 0.12-8.2 micrograms/mL for ADM, 0.066-25 micrograms/mL for MMC, 0.57-7 micrograms/mL for CDDP, 0.68-300 micrograms/mL for VP-16. IC50 after 72 h of exposure to 5-FU ranged from 1.8-23 micrograms/mL.

[A study of 5-fluorouracil on bovine trabecular meshwork cells in vitro]

OBJECTIVE

To determine whether the clinical use of 5-fluorouracil (5-FU) may have any toxic effects on trabecular meshwork cells.

METHODS

Bovine trabecular meshwork (BTM) cells were cultured in vitro. The effects of 5-FU on BTM cells concerning cellular morphology, ultrastructure, vitality and phagocytosis were observed.

RESULT

The safe dosage of 5-FU on BTM cell was 1 x 10-6g.ml-1.

CONCLUSION

Based on the pharmacokinetic data in the rabbit anterior chamber, it is suggested that the 5-FU dosage of conventional use cause no injury to human trabecular meshwork cells.

[Immunotoxic effects of a new antineoplastic agent S-1 in mice--comparison with S-1, UFT and 5-FU]

The immunotoxicity of S-1, which is a new antineoplastic agent, was investigated in BALB/c mice. S-1 contains tegafur (FT), CDHP, and potassium oxonate (Oxo) in a molecular ratio of 1:0.4:1. 5-fluorouracil (5-FU) and UFT were used as reference drugs. S-1 and reference drugs were administered by oral gavage for 7 days. The high dose employed in this study was determined as the maximally tolerated dose of a 9-day repeated-dose study in sarcoma 180-bearing mice. Decreased body weight was observed in mice treated with 5-FU and UFT but not in those treated with S-1. A significant decrease in thymus and spleen weight was observed in S-1-, UFT- and 5-FU-treated mice, and the degree was same for the three drugs. Though the number of white blood cells decreased dose-dependently for the three drugs, S-1 had the weakest effect. The number of red blood cells also decreased, but the effect was not dose-dependent, and its magnitude was the same for the 3 drugs. S-1 induced a dose-dependent decrease in the IgM antibody PFC response to sheep erythrocytes. The delayed type hypersensitivity response used a footpad reaction method was significantly suppressed at the highest dose of S-1. 5-FU and UFT suppressed humoral and cell-mediated immunity in almost the same manner as S-1. The degree of suppressive effects was greater on the humoral immune response than on the cell-mediated immune response. The number of CFU-GM colonies was significantly decreased in the highest dose group of each drug and in a lower group as well in S-1-treated mice. This finding might reflect the fact that S-1 induced continuous high levels of 5-FU in the blood. Under these experimental conditions, S-1 induced immunosuppressive effects in BALB/c mice, and the degree of suppression was almost same as that induced by 5-FU and UFT.

Pharmacological effects of 5-fluorouracil microspheres on peritoneal carcinomatosis in animals

A new delivery formulation (5FU-MS) of 5-fluorouracil (5FU), 5FU incorporated in microspheres composed of poly(glycolide-co-lactide) matrix, has been developed for the treatment of peritoneal carcinomatosis, and is designed to slowly release the incorporated 5FU for 3 weeks. Intraperitoneal 5FU-MS distributed higher concentrations of 5FU to the intraperitoneal tissues, such as the omentum and the mesentery, for a longer period with lower blood plasma concentrations than did the aqueous 5FU solution in rats. In experiments using mice, the lethal toxicity, determined by the probit method, in 5FU-MS was reduced to less than half that in aqueous 5FU solution. We evaluated the therapeutic effects on peritoneal carcinomatosis induced by the intraperitoneal inoculation of B-16 PC melanoma cells. The therapeutic effects of 5FU-MS were enhanced when compared with both the equivalent doses and same toxicity doses of the aqueous 5FU solution.

Constitutive expression of Mpl ligand transcripts during thrombocytopenia or thrombocytosis

Mpl ligand (thrombopoietin [TPO]) is the physiological regulator of platelet production. In mice, mRNA encoding the Mpl ligand (Mpl-L) is predominantly found by Northern blot analysis in the liver and kidney. To investigate the mode of regulation of the Mpl-L gene, we have developed several experimental models of severe thrombocytopenia differing in their kinetics and an opposite model of chronic thrombocytosis. Northern analysis performed at various times after induction of a thrombocytopenic state demonstrates that, whatever the number of circulating platelets, no change in Mpl-L mRNA level occurs in liver and kidney. By ribonuclease protection assays, we analyzed the ratios between mRNAs coding for the wild-type Mpl-L form and various splice variants encoding inactive or nonsecreted Mpl-L proteins. No modification in levels of these various isoforms was detected confirming the data of a previous report. Because the highest level of Mpl-L bioactivity in sera was observed only in mice with drastically reduced numbers of both platelets and megakaryocytes, these results further suggest that not only platelets, but also megakaryocytes, must be involved in the regulation of the level of circulating Mpl-L. In addition, we show that no downregulation of wild-type Mpl-L mRNA and no change in the ratio of Mpl-L mRNA isoforms were detected in mice in which a chronic thrombocytosis was induced. Together, these different models extend and further confirm that the regulation of Mpl-L does not occur at a transcriptional level or by a modulation in the ratios of Mpl-L mRNA isoforms.

Hematopoiesis in mice lacking the entire granulocyte-macrophage colony-stimulating factor/interleukin-3/interleukin-5 functions

Interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-5 are major hematopoietic cytokines produced by activated T cells and exhibit similar biologic activities by signaling through a common receptor subunit (beta c). Mice lacking beta c show a pulmonary alveolar proteinosis-like disease and reduced numbers of peripheral eosinophils, which are explained by the lack of GM-CSF and IL-5 function, respectively. However, beta c-deficient hematopoietic cells do respond to IL-3 normally, probably through an additional beta subunit of the IL-3 receptor (beta IL3) that is present in the mouse. Thus, almost normal hematopoiesis in beta c-deficient mice may be caused by functional redundancy between IL-3 and GM-CSF. To clarify the role of the entire IL-3/GM-CSF/IL-5 system in hematopoiesis in vivo, we crossed the beta c mutant mice with mice deficient for IL-3 ligand to generate mice lacking the entire IL-3/GM-CSF/IL-5 functions. The double-mutant mice were apparently normal and fertile. The severity of the lung pathology in the beta c/IL-3 double-mutant mice showed normal hemodynamic parameters except for reduced numbers of eosinophils and the lack of eosinophilic response to parasites, which were also found in beta c mutant mice. The immune response of the beta c/IL-3 double-mutant mice to Listeria mono-cytogenes was normal, as was hematopoietic recovery after administration of the cytotoxic drug, 5-fluorouracil. Although it has been believed that IL-3/GM-CSF/IL-5 produced by activated T cells play a major role in expansion of hematopoietic cells in emergency, our results indicate that the entire function of IL-3/GM-CSF/IL-5 is dispensable for hematopoiesis in emergency as well as in the steady state. Thus, there must be an alternative mechanism to produce blood cells in both situations.

Enhancing the effect of anticancer drugs against the colorectal cancer cell line with electroporation

Electroporation was applied in vitro and in vivo in the treatment of human colorectal cancer cell lines to study whether it can enhance the effect of bleomycin (BLM), 5-fluorouracil (5-FU) and cis-platinum (CDDP). We used LS174T and Colo320 cells derived from human colon cancer as target cells in this study. When the LS174T cells were used as target cells, the IC50 of BLM decreased to 10(-3) times, while that of 5-FU decreased to only about one fifth with the application of electric current. In the case of the Colo320 cells, the IC50 of BLM and 5-FU were about one hundredth and a half, respectively. The effect of CDDP was not enhanced with electric current. In vivo experiments were also performed using LS174T cells transplanted subcutaneously (s.c.) into nude mice. By treatment with intravenously (i.v.) administered BLM and simultaneous application of the electric current, tumors were markedly decreased in size after three weeks.

New formulation of 5-fluorouracil in microspheres reduces toxicity in mice

A new dosage formulation of 5-fluorouracil incorporated in microspheres (5-FU-MS) was developed for the treatment of peritoneal carcinomatosis. We studied the acute toxicity and side effects of i.p. 5-FU-MS in mice. The 50% lethal dose value for 5-FU-MS was 535.4 mg/kg of 5-FU, which was 2.22 times that of the aqueous 5-FU solution. Deaths occurred 12-17 days after the administration of 5-FU-MS, but within 11 days after the administration of aqueous 5-FU. Thus, lethal toxicity appeared later with 5-FU-MS than with aqueous 5-FU. There were no differences in pathologic findings on autopsy between mice given the two dosage formulations.

Molecular basis of the human dihydropyrimidine dehydrogenase deficiency and 5-fluorouracil toxicity

Dihydropyrimidine dehydrogenase (DPD) deficiency constitutes an inborn error in pyrimidine metabolism associated with thymine-uraciluria in pediatric patients and an increased risk of toxicity in cancer patients receiving 5-fluorouracil (5-FU) treatment. The molecular basis for DPD deficiency in a British family having a cancer patient that exhibited grade IV toxicity 10 d after 5-FU treatment was analyzed. A 165-bp deletion spanning a complete exon of the DPYD gene was found in some members of the pedigree having low DPD catalytic activity. Direct sequencing of lymphocyte DNA from these subjects revealed the presence of a G to A point mutation at the 5'-splicing site consensus sequence (GT to AT) that leads to skipping of the entire exon preceding the mutation during pre-RNA transcription and processing. A PCR-based diagnostic method was developed to determine that the mutation is found in Caucasian and Asian populations. This mutation was also detected in a Dutch patient with thymine-uraciluria and completely lacking DPD activity. A genotyping test for the G to A splicing point mutation could be useful in predicting cancer patients prone to toxicity upon administration of potentially toxic 5-FU and for genetic screening of heterozygous carriers and homozygous deficient subjects.

Comparison of chemically induced DNA breakage in cellular and subcellular systems using the comet assay

The alkaline comet assay, employing a single cell gel electrophoresis, is a rapid, simple and sensitive technique for visualizing and measuring DNA damage leading to strand breakage in individual mammalian cells. In this report, we describe a modified version of this assay which we used to assess DNA damage as a result of treating lysed cells with genotoxic and antimetabolic agents. By means of this modified assay, DNA is no longer held under the regulation of any metabolic pathway or membrane barrier. Using 3 direct-acting agents, hydrogen peroxide, N-methyl-N-nitrosourea, and bleomycin, we were able to induce increased DNA migration by both the standard and modified comet assays. In contrast, with 4-nitroquinoline 1-oxide, 5-fluorouracil, and methotrexate, which require cellular enzymatic activity to induce DNA damage, we succeeded in inducing increased DNA migration using the standard comet assay conditions only. In some cases, the modified comet assay might be helpful in analyzing chemical and biological characteristics of genotoxic agents when performed in combination with the standard comet assay.

Effects of a nonapeptide thymic hormone on intestinal intraepithelial lymphocytes in mice following administration of 5-fluorouracil

A significant fraction of murine small intestinal intraepithelial lymphocytes (i-IELs) mature in local sites outside the thymus. However, there is evidence suggesting that extrathymic differentiation of i-IELs is still influenced by the thymus or thymus-derived factors. Facteur thymique serique (FTS), a nonapeptide thymic hormone, is involved in several aspects of intra- and extrathymic T cell differentiation in vivo. In this study, we investigated the effects of FTS on the kinetics of i-IELs in mice following a single administration of 5-fluorouracil (5-FU). FTS treatment significantly accelerated the recovery in cell number of i-IELs after administration of 5-FU. Flow cytometric analysis revealed that this accelerated recovery was mainly due to a rapid increase in CD8 alpha alpha+ i-IELs. Similar findings were also evident in adult thymectomized (ATX) mice, indicating that FTS treatment caused a rapid recovery of CD8 alpha alpha+ i-IELs following 5-FU administration in the absence of a functional thymus. Furthermore, expression levels of the mRNAs for interleukin-2, interferon-gamma, and transforming growth factor beta 1 in the i-IELs were augmented by FTS treatment. Notably, FTS treatment protected mice from 5-FU-induced lethal toxicity, accompanied with an inhibition of the translocation of Enterobacteriaceae. These results suggest that FTS has an important function in the extrathymic maturation and activation of i-IELs in the small intestine following 5-FU administration, which may contribute at least partly to the protection against 5-FU-induced lethal toxicity.

Metabolites of 5-fluorouracil, alpha-fluoro-beta-alanine and fluoroacetic acid, directly injure myelinated fibers in tissue culture

The neurotoxicity of two 5-fluorouracil (5-FU) derivatives, tegafur (FT) and carmofur (HCFU), which selectively induce leukoencephalopathy involving the cerebral white matter in humans and vacuolation of myelinated fibers in dogs and cats, was examined in vitro. The common metabolites of these drugs, alpha-fluoro-beta-alanine (FBAL) and fluoroacetic acid (FA), were added to the medium of cultured murine cerebellar myelinated fibers. On day 1 of exposure to 7 microM FBAL and FA, which corresponds to their blood concentrations 2 h after oral administration of 10 mg.kg-1 HCFU to dogs that induced central nervous system vacuolation after 30 days, partial splits of the myelinic intraperiod line were observed by electron microscopy. On days 4-7, phase contrast microscopy revealed spindle-shaped swelling and granulation of myelin and electron microscopy demonstrated prominent dissociation of the myelinic intraperiod line with monolocular and multilocular vacuolation. More severe changes, such as myelin loss, were found in cultures exposed to a higher concentration (70 microM) of FBAL and FA, but no remarkable neuronal, astrocytic or oligodendrocytic changes occurred. Quantitative evaluation of myelin injury by electron microscopy revealed significant toxicity of FBAL and FA, at concentrations of 7 and 70 microM, on day 4. However, groups treated with 0.7 microM FBAL and FA, 5-FU (7 microM) and controls exposed to beta-alanine and acetic acid concentrations of 0.7, 7 and 70 microM showed no marked injury. We concluded that these anticancer drug metabolites injure myelin fibers directly, resulting in vacuolation due to myelin splitting and destruction.

Drug retention following intravesical delivery of fluorouracil therapeutic adhesive in C3H mouse bladder

We have developed a fibrinogen-based, sustained-retention drug delivery system, therapeutic adhesive (TA), for application to resected tumor beds to reduce local tumor recurrences. In this study we evaluated the feasibility, safety and retention of the TA formulated with 5-fluorouracil (5-FU TA) after intravesical administration in a mouse bladder model. Radiolabeled [14C]5-FU TA or [14C]5-FU solution was delivered intravesically to C3H/He female mice. After drug administration, retention of 14C in the bladder was quantified by storage-phosphor autoradiography. A 2.6-fold increase in retention was observed with 5-FU TA when compared with 5-FU solution. The AUC(2 min-5 h) for 5-FU TA was 685 nmol h/mm2 compared with 260 nmol h/mm3 for 5-FU solution. No signs of toxicity in the bladder tissue or treatment-associated adverse effects were observed in the mice.

Combined effect of 5-fluorouracil and recombinant tumor necrosis factor against human gastric carcinoma cell lines

This study was performed to investigate the direct effects of recombinant human tumor necrosis factor (rH-TNF) and recombinant human interleukin-2 (rH-IL-2), either alone or in combination, on the cytotoxicity of 5-FU measured by MTT assay against human gastric adenocarcinoma cell lines (MKN-28 and MKN-45), and also to determine the optimal schedule for their combination. The antitumor activity of rH-TNF was enhanced more than 42% by 10(2) U/ml of rH-IL-2. The enhancing effects of rH-TNF and rH-IL-2 on the cytotoxicity of 5-FU were evaluated in terms of Modification Index(MI), the MI value at 10 U/ml rH-TNF was 1.6; the MI at the same concentration of rH-TNF in the presence of 10(2) U/ml of rH-IL-2 was 2.1. These results demonstrated that the antitumor effect of 5-FU was enhanced 1.6 times by 10 U/ml of rH-TNF and further enhanced by the combined use of rH-TNF and rH-IL-2. The combined effect of equal concentrations of 5-FU and rH-TNF was superior or equivalent to that of 5-FU or rH-TNF alone. The sequence of 5-FU followed by rH-TNF and rH-IL-2 showed a higher inhibitory effect than the reverse sequence. This sequence combination seems worthy of further consideration for the treatment of gastric cancer.

In vitro chemosensitivity testing of human tumours by collagen gel droplet culture and image analysis

It is necessary to develop an in vitro test to overcome the problems often associated with in vitro chemosensitivity tests on individual human tumours. We have developed a collagen gel droplet culture technique that allows for a three-dimensional in vitro growth and drug response assay for human solid tumour cells. Important features of chemosensitivity testing by the collagen gel droplet culture technique include the maintenance of high cloning efficiencies resulting in the need for fewer tumour cells, sufficient suppression of the in vitro proliferation of contaminating non-malignant cells by serum-free medium, and the application of the image analysis system which automatically discriminates between cancer cell colonies and fibroblasts. We described in vitro-in vivo correlations for drug response using 7 human lung cancer xenografts grown in the collagen gel droplet culture and as xenografts in nude mice. Results demonstrated significant correlations with the in vitro drug concentration at 1/10 of the peak plasma concentrations (1/10 Cmax) with the correlation coefficient 0.84 for all four drugs tested. We have cultured 206 tumours thus far obtaining 86% of evaluability for drug response. The drug response data of the fresh lung cancers were similar to not only to data for lung cancer lines but the reported clinical pattern. These results suggested that the collagen gel droplet culture at 1/10 Cmax may have potential in predicting clinical drug responses.

Effect of stereotactic implantation of biodegradable 5-fluorouracil-loaded microspheres in healthy and C6 glioma-bearing rats

OBJECTIVE

Poly(lactic acid-co-glycolic acid) (PLAGA) microspheres are promising systems for interstitial chemotherapy of brain tumors. They can be readily implanted by stereotaxy and are biocompatible with the brain, in which they are totally biodegraded within 2 months. 5-Fluorouracil (5-FU) was selected for encapsulation, because this hydrophilic and antimetabolic drug is not directly neurotoxic and does not readily cross the blood-brain barrier. Also, its anticancer activity may be improved by sustained administration. Furthermore, it is a potent radiosensitizer.

METHODS

To study their fate and toxicity, two types of 5-FU-loaded PLAGA microspheres were implanted in healthy rats by stereotaxy. One type presented a fast in vitro release profile (FR), and the second exhibited a slow in vitro release pattern (SR) (100% of the encapsulated 5-FU is released within 72 hours and 18 days, respectively). Periodically, rats were killed for microscopic examination. The efficacy of these microspheres on rat glioma was then evaluated. Seven days after stereotactic implantation of C6 malignant glioma cells in the brain, the rats were treated by intratumoral injection of 5-FU solution, blank microspheres, or 5-FU-loaded microspheres (FR and SR types). The mortality of these treated groups was compared by the log-rank test with that of an untreated group.

RESULTS

After implantation of two types of 5-FU-loaded PLAGA microspheres, no sign of clinical or histological toxicity was observed. Entrapped 5-FU crystals were observed until Days 12 and 20 postimplantation within FR and SR microspheres, respectively, which suggests a longer releasing period in vivo than in vitro. In the therapeutic evaluation, only intratumoral implantation of SR-type 5-FU-loaded microspheres significantly decreased the mortality (P = 0.017).

CONCLUSION

5-FU-loaded PLAGA microspheres were implanted in rat brains without evident toxicity. Histological examination suggested a longer sustained delivery period in vivo than in vitro. Intratumoral implantation of SR-type 5-FU-loaded microspheres decreased the mortality of C6 tumor-bearing rats. This effect can be related to the local and the sustained delivery of the drug, because 5-FU administered systemically is ineffective against brain tumors.

Protection of the small intestinal clonogenic stem cells from radiation-induced damage by pretreatment with interleukin 11 also increases murine survival time

The effect of administering recombinant human interleukin 11 in conjunction with cytotoxic insults to the gastrointestinal tract has been studied using the crypt microcolony assay for stem cell function and whole-animal survival time studies. The cytotoxic regimens include single doses of gamma rays; single doses of 5-fluorouracil (5-FU) and multiple doses of 5-FU spaced 6 h apart. Interleukin 11 (IL-11) (100 micrograms/kg) delivered over a period of time prior to cytotoxic exposure afforded protection to the clonogenic cells in the crypts as seen with the microcolony assay and prolonged the animal survival time following radiation exposure. Continuing this dose of IL-11 after cytotoxic exposure afforded little additional protection. Three doses of 5-FU 6 h apart generated crypt survival curves similar to those obtained after a single dose of gamma rays. IL-11 given prior to two doses of 5-FU effectively abolished the cytotoxic effect of the second dose of 5-FU; i.e., 2.5-3.0 times more crypts survived if IL-11 was administered when the higher 5-FU doses are considered. IL-11 given before a dose of 12 Gy of gamma rays prolonged the survival time of animals by three to four days. This confirms earlier studies demonstrating that protecting clonogenic cells in the crypt survival assay can result in beneficial effects on whole-animal survival times.