Liver Of Tumor-bearing Animals Research Articles

Effects induced by a 50 HZ electromagnetic field and doxorubicin on Walker-256 carcinosarcoma growth and hepatic redox state in rats

ABSTRACT We compare the effects of an extremely low-frequency electromagnetic field (EMF) with the chemotherapeutic agent doxorubicin (DOX) on tumor growth and the hepatic redox state in Walker-256 carcinosarcoma-bearing rats. Animals were divided into five groups with one control (no tumor) and four tumor-bearing groups: no treatment, DOX, DOX combined with EMF and EMF. While DOX and DOX + EMF provided greater inhibition of tumor growth, treatment with EMF alone resulted in some level of antitumor effect (p < .05). Superoxide dismutase, catalase activity and glutathione content were significantly decreased in the liver of tumor-bearing animals as compared with the control group (p < .05). The decreases in antioxidant defenses accompanied histological findings of suspected liver damage. However, hepatic levels of thiobarbituric acid reactive substances, an indicator of lipid peroxidation, were three times lower in EMF and DOX + EMF groups than in no treatment and DOX (p < .05). EMF and DOX + EMF showed significantly lower activity of serum ALT than DOX alone (p < .05). These results indicate that EMF treatment can inhibit tumor growth, causing less pronounced oxidative stress damage to the liver. Therefore, EMF can be used as a therapeutic strategy to influence the hepatic redox state and combat cancer with reduced side-effects.

Antioxidants selenomethionine and D-pantethine decrease the negative side effects of doxorubicin in NL/Ly lymphoma-bearing mice.

AimTo investigate the potential tissue-protective effects of antioxidants selenomethionine and D-pantethine applied together with doxorubicin (Dx) on NK/Ly lymphoma-bearing mice. The impact of this chemotherapy scheme on animal survival, blood cell profile, hepatotoxicity, glutathione level, and activity of glutathione-converting enzymes in the liver was compared with the action of Dx applied alone.MethodsThe hematological profile of animals was studied by the analysis of blood smears under light microscopy. Hepatotoxicity of studied drugs was evaluated measuring the activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) enzymes, De Ritis ratio, and coenzyme A fractions by McDougal assay. Glutathione level in animal tissues was measured with Ellman reagent, and the activity of glutathione reductase, transferase, and peroxidase was measured using standard biochemical assays.ResultsD-pantethine (500 mg/kg) and, to a lower extent, selenomethionine (600 µg/kg) partially reduced the negative side effects (leukocytopenia and erythropenia) of Dx (5 mg/kg) in NK/Ly lymphoma bearing animals on the 14th day of their treatment. This increased animal survival time from 47-48 to 60+ days and improved the quality of their life. This ability of D-pantethine and selenomethionine was realized via hepatoprotective and immunomodulating activities. D-pantethine also restored the levels of acid-soluble and free CoA in the liver of tumor-bearing animals, while selenomethionine caused the recovery of glutathione peroxidase levels in the liver, which was significantly diminished under Dx treatment. Both compounds decreased glutathione level in the liver, which was considerably induced by Dx.ConclusionsAntioxidants selenomethionine and D-pantethine partially reversed the negative side effects of Dx in NK/Ly lymphoma-bearing mice and significantly increased the therapeutic efficiency of this drug in tumor treatment.

A factor responsible for the metabolic deviations in liver of tumor-bearing animals.

A factor responsible for the metabolic deviations in liver of tumor-bearing animals.

Extrahepatic Cancer Suppresses Nuclear Receptor–Regulated Drug Metabolism

To determine the mechanisms by which tumors situated in extrahepatic sites can cause profound changes in hepatic drug clearance, contributing to altered drug response and chemotherapy resistance. We studied in wild-type or transgenic CYP3A4 reporter mice implanted with the murine Engelbreth-Holm-Swarm sarcoma changes in nuclear receptor and hepatic transcription factor expression and/or function, particularly related to CYP3A gene regulation. Repression of hepatic CYP3A induction was dramatic and associated with reduced levels of C/EBPβ isoforms, impaired pregnane X receptor, and constitutive androstane receptor function. Unexpectedly, extrahepatic tumors strongly reduced nuclear accumulation of retinoid X receptor alpha (RXRα) in hepatocytes, providing a potential explanation for impaired function of nuclear receptors that rely on RXRα dimerization. Profiling revealed 38 nuclear receptors were expressed in liver with 14 showing between 1.5- and four-fold reduction in expression in livers of tumor-bearing animals, including Car, Trβ, Lxrβ, Pparα, Errα/β, Reverbα/β, and Shp. Altered Pparα and γ induction of target genes provided additional evidence of perturbed hepatic metabolic control elicited by extrahepatic tumors. Extrahepatic malignancy can affect hepatic drug metabolism by nuclear receptor relocalization and decreased receptor expression and function. These findings could aid the design of intervention strategies to normalize drug clearance and metabolic pathways in cancer patients at risk of chemotherapy-induced toxicity or cancer cachexia.

Studies on tryptophan peroxidase in the liver of tumor-bearing animals.

Studies on tryptophan peroxidase in the liver of tumor-bearing animals.

Ferritin content of the liver of tumor-bearing animals.

Ferritin content of the liver of tumor-bearing animals.

Modulation of xenobiotic-metabolizing enzymes and redox status during chemoprevention of hamster buccal carcinogenesis by bovine lactoferrin

Chemoprevention by dietary constituents has emerged as a novel approach to control oral cancer incidence. We therefore evaluated the chemopreventive efficacy of bovine milk lactoferrin (bLF) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into four groups. The right buccal pouches of animals in groups 1 and 2 were painted with 0.5% DMBA three times a week for 14 wk. Animals in group 2, received in addition, basal diet containing 0.2% bLF. Group 3 animals were given 0.2% bLF alone. Group 4 animals served as control. The status of carcinogen-metabolizing enzymes, the extent of lipid peroxidation and glutathione-dependent antioxidants in the buccal pouch and liver as well as bone marrow micronuclei incidence were used as biomarkers. All the hamsters painted with DMBA alone for 14 wk, developed HBP carcinomas that showed diminished lipid peroxidation and increased activities of carcinogen-metabolizing enzymes and antioxidants with enhanced bone marrow micronuclei. In the liver of tumor bearing animals, the increase in phase I enzymes and lipid peroxidation was accompanied by reduced activities of antioxidant and phase II detoxification enzymes. Administration of bLF decreased the incidence of DMBA-induced micronuclei and HBP carcinomas by decreasing phase I enzymes, modulating lipid peroxidation and enhancing antioxidant and phase II enzyme activities. The chemopreventive effects of bLF is mediated by reducing DMBA-induced genotoxicity and modulating carcinogen-metabolizing enzymes and oxidant-antioxidant profile in the target organ as well as in the liver.

Effect of cisplatin and cobalt chloride on antioxidant enzymes in the livers of Lewis lung carcinoma-bearing mice: protective role of heme oxygenase

Changes in the activities of antioxidant enzymes superoxide dismutase, catalase (CAT), glutathione peroxidase and heme oxygenase (HO) and changes in lipid peroxidation and reduced glutathione (GSH) levels were measured in the livers of control and Lewis lung carcinoma (LLC)-bearing mice 24 h after a single injection of cisplatin or CoCl(2). Treatment with cisplatin induced the same degree of lipid peroxidation and GSH depletion as did CoCl(2) but the antioxidant enzymes were differently involved in cisplatin- and cobalt-induced oxidative stress responses. In cobalt-treated mice the activities of these enzymes were either inhibited or not changed significantly and only the HO activity was increased (5-fold) as a main protective enzyme. In cisplatin-treated animals the antioxidant enzymes were activated but the enhancement of HO and CAT was greater in LLC-inoculated mice. It is suggested that these two enzymes represent the protective response against cisplatin toxicity in the livers of tumor-bearing animals.

Lycopene, an antioxidant carotenoid modulates glutathione-dependent hepatic biotransformation enzymes during experimental gastric carcinogenesis

Abstract We investigated the effects of lycopene on hepatic oxidant-antioxidant status during N-methyl-N′-nitro-N-nitrosoguanidine and saturated sodium chloride (S-NaCl)-induced gastric carcinogenesis. The extent of lipid peroxidation and the levels of reduced glutathione (GSH) and activities of the GSH-dependent enzymes glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were used to monitor the peroxidative balance. Enhanced lipid peroxidation in the livers of tumor-bearing animals was accompanied by significant decreases in the activities of GSH, GPx, GST and GR. Administration of lycopene significantly lowered the levels of lipid peroxides and enhanced GSH levels and activities of GSH-dependent enzymes. Our results suggest that lycopene blocks experimental gastric carcinogenesis by upregulating GSH-dependent hepatic detoxification systems thereby protecting against carcinogen-induced oxidative damage.

Hepatic Glutaminase Gene Expression in the Tumor-Bearing Rat

Previous studies have documented an increase in hepatic plasma membrane glutamine transport in the tumor-bearing rat, but the effects of tumor burden on hepatic glutaminase expression have not been carefully studied. The purpose of this study was to examine the effects of tumor burden and food intake on hepatic glutaminase expression. Rats were implanted with syngeneic methylcholanthrene-induced fibrosarcoma tumor tissue; control rats were sham operated and pair-fed every 24 hr. Northern blotting was used to assay the effect of tumor burden and fasting on hepatic glutaminase mRNA levels, using beta-actin mRNA as a control. Hepatic glutaminase mRNA levels in livers of pair-fed controls were found to be 4-fold greater than levels in livers of tumor-bearing animals. Examination of food intake patterns in these animals indicated that pair-fed controls ate their allotted chow quickly while tumor-bearing rats ate small amounts throughout each 24 hr period. This observation suggested that the differences in glutaminase mRNA levels may be due to a period of fasting by pair-fed animals which was not experienced by the tumor-bearing group. Hepatic glutaminase mRNA levels rapidly increased in normal rats during acute fasting to levels 5.5-fold greater than fed animals. Glucose feeding and insulin injection rapidly reversed the effect of fasting on hepatic glutaminase mRNA levels in normal rats. Tumor-bearing rats also exhibited upregulation of hepatic glutaminase mRNA levels in response to fasting. (1) Tumor burden itself does not alter hepatic glutaminase expression, at least at the pre-translational level. Instead, differences in hepatic glutaminase mRNA content are due to differences in food intake patterns. (2) Hepatic glutaminase mRNA levels are rapidly upregulated in response to fasting, an effect which appears to be linked to a decrease in plasma insulin concentrations. Because tumor-bearing rats eat regularly over a 24 hr period (albeit in small increments), thereby maintaining the plasma insulin concentration, hepatic glutaminase mRNA may not rise as it does in pair-fed controls whose daily chow intake is complete within hours of food allocation. (3) This study indicates that differences in the timing of food intake between tumor-bearing rats and pair-fed controls can alter the expression of genes that are influenced by nutrient availability. These differences should be taken into account when designing studies which involve pair-feeding to control nutrient intake.

Increased liver chemiluminescence in tumor-bearing mice

Spontaneous mouse liver chemiluminescence (109 +/- 6 cps/cm2) was increased in the early phase after tumor implantation in a distant position with respect to the liver. A 39% increased liver chemiluminescence was observed after 5 days of the injection of Ehrlich ascites tumor cells into the peritoneal cavity, and a 64% and a 46% increased liver chemiluminescence were measured after 8 and 14 days of the implantation of a fibrosarcoma and of an adenocarcinoma, respectively, in the leg. At the time of maximal stimulation of in vivo liver chemiluminescence by the distant tumors, cytosolic superoxide dismutase, catalase, and glutathione peroxidase activities were decreased by 18%, 38%, and 26% in the liver of mice bearing Ehrlich ascites tumors. The same three enzymatic activities were decreased by 21%, 19%, and 54% respectively, in the liver of fibrosarcoma-bearing mice. Total liver glutathione was decreased by 18% to 22% in the tumor-bearing animals. Hydroperoxide-initiated chemiluminescence was increased in the homogenates (105% and 45%) and mitochondria (64% and 34%) from the liver of mice bearing Ehrlich ascites tumors and fibrosarcomas, respectively, at the time of maximal in situ liver chemiluminescence. The hydroperoxide-initiated chemiluminescence of liver microsomes was decreased by 46% to 36% in the tumor-bearing animals at the same time. It is concluded that the liver of tumor-bearing animals is subjected, during the early phase after tumor implantation, to an oxidative stress with increased steady-state levels of peroxyl radicals, which are essentially responsible for the increased photoemission observed in vivo.

Pharmacokinetics of nitrosoureas: levels of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in organs of normal and Walker 256/B carcinoma bearing rats after i.v. bolus.

The disappearance of 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) from plasma, liver, kidney, lung, brain, spleen, tumor tissue and epididymal adipose tissue of Walker 256/B carcinoma-bearing rats and healthy animals was measured by differential pulse polarography after i.v. bolus of the drug. Only BCNU, not its decomposition products, was detected by the polarographic assay. Levels of BCNU in liver of tumor-bearing animals were significantly lower (about 10 times) than those on healthy rats. A bi-exponential fit was used to calculate the kinetics of BCNU in plasma, kidney, lung and brain, but no difference could be found between healthy and Walker tumor-bearing rats. BCNU disappeared faster from adipose tissue of tumor-bearing animals than from normals.

Effect of Morris 7777 hepatoma on microsomal glucose-6-phosphatase latent activity.

The change in the activity of several hepatic enzymes during hepatocarcinogenesis suggests a pattern of dedifferentiation. This category of enzymes includes glucose-6-phosphatase and gamma-glutamyltranspeptidase (GGT). A detailed kinetic analysis of microsomal glucose-6-phosphatase activity revealed that both the translocase and phosphohydrolase activities were markedly reduced in Morris 7777 hepatoma transplanted in male Buffalo rats. In addition, the activity of the translocase component increased 2.4-fold, while the phosphohydrolase activity decreased 1.6-fold in the liver of tumor-bearing animals. GGT activity in the host liver was not effected by the presence of the tumor. These results suggest differences in the effect of Morris 7777 hepatoma on: the phosphohydrolase and translocase activities of microsomal glucose-6-phosphatase and the sensitivity of glucose-6-phosphatase and GGT activities in the host liver.

Biochemical basis for impaired drug metabolism in tumor-bearing rats: Evidence for altered regulation of hepatic microsomal hemeprotein synthesis

The pharmacologie effects of many drugs are enhanced in animals bearing tumors. This apparently stems from a decrease in the microsomal metabolism of these compounds in liver cells, owing to a decrease in either the activities of certain enzymes or in the content of cytochrome P-450 in microsomes, or both. Since impaired drug metabolism may have a direct bearing on the outcome of chemotherapy, a study of the biochemical basis for this alteration was begun. In female Sprague-Dawley rats bearing Walker 256 solid tumors i.m., pentobarbital metabolism was impaired as judged from prolonged sleeping-times. This effect was accompanied by a decrease in the microsomal content of cytochrome P-450. Analysis of hepatic microsomes by sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed that a microsomal protein of ~53,000 daltons was diminished in livers of tumor-bearing animals, when compared to normal controls, as determined by staining with Coomassie Blue. When rats were injected with [3H]leucine, although the dpm/100 μg of microsomal protein were the same for both normal and tumor-bearing rats, ~40% less 3H was associated with the microsomal proteins in the cytochrome P-450 region (~43,000 to ~58,000 daltons) of tumor-bearing animals than with those of normal controls. This was attributed to a decrease in the rate of synthesis of these, but not of other, microsomal proteins. Either staining of microsomal proteins with 3,3',5,5'-tetramethyl-benzidine, or labelling of them with δ-[14C]aminolevulinic acid, revealed that the overall content of microsomal hemeproteins of tumor-bearing rats was reduced considerably, when compared to normal controls (~70% as judged by the incorporation of 14C). These observations prompted investigations of the apparent rate-limiting synthetic and degradative enzymes of heme. We found that in the livers of 7-day tumor-bearing rats, the activity of δ-aminolevulinic acid synthetase was only 16% of control activity; conversely, the activity of hepatic microsomal heme oxygenase in the tumor-bearing rats was nearly eight-times greater than that of the normal animals. Together, these data indicate that perturbations in heme- and hemeprotein-synthesis cause the reduced content of cytochrome P-450 seen in tumor-bearing rats, and they provide a partial explanation for diminished drug metabolism by hepatic microsomes in the presence of a growing, transplantable, non-hepatic tumor.

Induction of mouse mammary tumor virus RNA in mammary tumors of BALB/c mice treated with urethane, X-irradiation, and hormones

The involvement of mouse mammary tumor virus (MTV) in the development of mammary tumors of nonviral etiology in BALB/c mice was studied by measuring the levels of MTV RNA, MTV DNA, and MTV proteins in spontaneously arising and hormonally, chemically, and/or physically induced mammary tumors of BALB/c females. The following results were obtained. (i) Spontaneous mammary tumors contained very low levels of MTV RNA; 4 X 10(-6)% of the the cytoplasmic RNA was MTV RNA. No MTV proteins could be demonstrated by using sensitive radioimmunoassays for MTV proteins p27 and gp52. (ii) Mammary tumors induced by treatments with urethane or X-irradiation alone contained higher levels of MTV RNA; these tumors contained 3- and 19-fold more MTV RNA, respectively, compared with spontaneous mammary tumors. (iii) Mammary tumors induced by combined treatment with urethane and X-irradiation expressed high levels of MTV RNA in the mammary tumors; a 1,724-fold increase in MTV RNA content compared with spontaneous mammary tumors was observed. However, very low levels of MTV proteins gp52 and p27 were detected, suggesting some kind of impairment at the translation of the MTV RNA. MTV RNA was also induced by this treatment in mammary glands and spleens, but not in the livers of tumor-bearing animals. (iv) Balb/c females continuously exposed to prolactin contained high levels of MTV RNA and MTV proteins in stimulated mammary glands and in the hormonally induced mammary tumors. These findings suggest that MTV is not responsible for the maintenance and probably also not for the development of all murine mammary cancers.

Studies on informational RNAs and ribonucleoproteins of normal rat liver, Zajdela hepatoma and liver of hepatoma-bearing rats

Abstract DNA-like RNA (D-RNA) species, both as constituents of RNP particles and protein-free molecules, isolated from normal rat liver, Zajdela ascites hepatoma and liver of tumor-bearing animals were compared with respect to their sedimentation and chromatographic behaviour. A selective labelling of D-RNA was carried out under actinomycin D-induced block of rRNA synthesis. No detectable differences in nuclear D-RNAs of the tissues compared could be observed whereas cytoplasmic D-RNAs of hepatoma and liver of tumor-bearing rats appear to be much more heterogeneous as compared to those of normal liver. The kinetics of the labelled D-RNAs appearing in the cytoplasm in case of malignant cells also differs from that characteristic of normal liver cells. The comparative analysis of cytoplasmic RNP complexes in the sucrose density and CsCl isopycnic band centrifugation revealed a shift in the ratio of polyribosome-bound and free complexes in favour of the latter in the tumor and liver of tumor-bearing rat as compared with normal liver. The data presented are interpreted to indicate a certain impairment in the selective nucleus-to-cytoplasm transport of RNA in tumor cells, the cells of tumor-bearing animal occupying in this respect an intermediate position between normal and tumor tissues.

Experimental Hepatomas: Dehydrogenation of Reduced Pyridine Nucleotides by the D-T Diaphorase

SummaryMajor differences were observed in the dehydrogenation of reduced pyridine nucleotides when experimental transplantable hepatomas were compared with livers of control animals and livers of tumor-bearing animals. The enzymatic activity of the D-T diaphorase was increased almost fivefold in the hepatomas. The same increase in enzymatic activity was observed in one slowly growing and one rapidly growing Morris hepatoma. The possible functional significance of these findings is discussed.

Properties of the genome in experimental hepatomas: Variations in the composition of chromatin

The chromosomal proteins of two rapidly growing and poorly differentiated Morris hepatomas were compared with those of liver from normal and tumor bearing animals. While the total quantity of histone associated with DNA in all tumor and liver chromatin preparations studied were similar, tumor chromatin contained an increased quantity of nonhistone chromosomal proteins. Variations in specific classes of histones and nonhistone chromosomal proteins associated with the genome of the two tumors, host liver and liver of tumor bearing animals were observed.

Dietary control of stearyl CoA and alkylacylglycerophosphorylethanolamine desaturases in tumor

The responses of stearyl CoA desaturase and alkylacylglycerophosphorylethanolamine desaturase were compared in Fischer R-3259 tumors of rats maintained on normal and fat-free diets. The stearyl CoA desaturase activity significantly increased in control livers, host livers, and tumors in rats maintained on the fat-free diet over that in the same tissues from animals maintained on laboratory chow; however, no increase of alkylacylglycerophosphorylethanolamine desaturase was observed in tumors of rats maintained on the fat-free diet. These findings suggest that the two desaturase systems are not identical and that they are controlled by different components of the microsomal electron transport system. Stearyl CoA desaturase activity was lower in the livers of tumor-bearing animals than in those of control animals. This finding supports the concept of others that indicates host livers tend to acquire the enzymic composition of immature livers.

Effect of hydrocortisone on the synthesis of DNA and histones and the acetylation of histones in regenerating liver

Abstract Pretreatment of rats with pharmacological doses of hydrocortisone for 1 to 5 days prior to partial hepatectomy strongly inhibited the rise in liver DNA synthesis which normally reaches a peak 24 hr after partial hepatectomy. However, 2 to 4 days after partial hepatectomy there was a partial recovery of DNA synthesis in the treated animals. The degree of inhibition of histone synthesis was considerably less than that of DNA, and only the synthesis of the slightly lysine-rich histones was closely coupled in time and relative magnitude with DNA synthesis. Synthesis of the lysine-rich and arginine-rich histone fractions was much less inhibited, and the rates of synthesis of these fractions increased prior to the delayed rise in DNA synthesis. The early increase in acetylation of the arginine-rich histone fractions after partial hepatectomy was not significantly affected by pretreatment with hydrocortisone. On the other hand, pretreatment with hydrocortisone strongly inhibited the late (24 hr) rise in acetylation of histone fraction f2a2. Hydrocortisone did not inhibit DNA synthesis in a transplanted hepatoma, but it did inhibit DNA synthesis in the livers of tumor-bearing animals.