Alterations in glycoproteins and lipids in azaserine-induced acinar cell carcinoma of rat pancreas

Glycoproteins and lipids of rat pancreatic acinar cell carcinomas maintained in nude mice and in cell culture, were analyzed. The tumor contained significantly elevated levels of glycoproteins when compared with their normal counterparts. SDS-PAGE of tumor glycoproteins revealed that there were increased amounts of small molecular weight glycoproteins and the tumor also contained a 51,000 dalton glycoprotein which was not detected in the pancreas, liver or the sera of the control animals. The tumor in nude mice and cancer cells in culture had decreased lecithins and triglycerides, and increased amounts of free fatty acids, and both free and esterified cholesterols. The results indicate that altered glycoprotein and lipid compositions represent some of the characteristic features of the acinar cell carcinoma.     

Response of the Syrian golden hamster to a nitrosourea amino acid carcinogen

Syrian golden hamsters were treated with N delta-(N-methyl-N-nitrosocarbamoyl)-L-ornithine (MNCO), a nitrosourea amino acid, which has induced a high incidence of breast, kidney and skin neoplasms and a low incidence of pancreatic carcinoma in rats. MNCO induced a few breast and skin carcinomas, and a high incidence of foci of atypical acinar cells and of focal ductular abnormalities in the exocrine pancreas. The latter were similar to lesions observed in rats treated with MNCO. MNCO was less toxic and less effective as a carcinogen in hamster than in the rat.     

The importance of short term exposure of C3H 10T12 cells to polycyclic hydrocarbons: Evidence for hydrocarbon-mediated anticarcinogenic activity

Since it has been shown that transformation frequencies (TF) of cultured mammalian cells exposed to polycyclic aromatic hydrocarbons (PAH) reach a maximum with increasing PAH concentration and then decline, we have examined TF in C3H $\text{10T}\text{1}\text{2}$ CL8 ($\text{10T}\text{1}\text{2}$) cells as a function of an additional parameter of treatment, length of exposure. A 15-min exposure to either benzo[a]pyrene (BP) or 3-methylcholanthrene (3-MC), at concentrations ranging from 0.3 to 10 μg/ml, was sufficient to induce transformation suggesting that, in $\text{10T}\text{1}\text{2}$ cells, non-induced enzymes of the cytochrome P-450 system are involved in the metabolic activation of PAH. At lower BP concentrations (0.3–1.25 μg/ml), TF generally increased with exposure time; at higher BP concentrations (2.5–10 μg/ml) maximal TF were achieved with 3 h of exposure. For 3-MC, maximal TF occurred at 0.5–1 h with a concentration of 10 μg/ml and at 1–6 h with lower concentrations. Moreover, low TF were obtained after 12-h and 24-h exposures to 10 μg/ml BP or 3-MC. These results show that TF depend on both the length of exposure and concentration of PAH. Since both BP and 3-MC are extensively metabolized to polyoxygenated derivatives and conjugates, we suggest that certain metabolites may be anticarcinogenic or antipromoting agents. The identities of such metabolites are yet to be determined.     

Lack of metabolism of 2,6-dimethyldinitrosopiperazine by microsomes and postmicrosomal supernatant prepared from the rat esophagus and non-glandular stomach

Microsomes and postmicrosomal supernatant were prepared from the esophagus and non-grandular stomach of rats. Using these fractions, we could not demonstrate in vitro metabolism of 2,6-dimethyldinitrosopiperazine (DMDNP), a potent esophageal and non-grandular stomach carcinogen in rats. The esophageal and non-grandular stomach fractions did metabolize N-nitrosopyrrolidine (NPYR) to a small extent, and liver microsomes and postmicrosomal supernatant metabolized both nitrosamines to a similar extent. Therefore, we advise caution in the interpretation of metabolic studies using ‘target’ and ‘non-target’ organs as indicative of activation of compounds to proximate carcinogens.     

Factors influencing the activity of dimethylnitrosamine demethylase in hamster, rat and chicken liver microsomes

In vitro metabolism of dimethylnitrosamine (DMN) by liver microsomal fractions of hamster, rat and chicken revealed that the three species under certain assay conditions, were capable of metabolizing DMN at different rates (hamster greater than rat greater than chicken). The magnitude of the demethylase activity was found to be dependent on the nature of the buffer, the concentration of cytochrome P-450 (P-450) and the concentration of the substrate DMN. Enzyme activity was higher in Hepes buffer than in the phosphate buffer. Concentrations of phosphate higher than 20 mM inhibited the activity of the rat and chicken enzymes. This effect of phosphate was not a consequence of increase in ionic strength since KCl over a wide range of concentration failed to inhibit the activity.     

Inhibition of proliferation of cultured cells by polyamine and cysteine interaction

Both L-cysteine and spermidine oxidation inhibited the proliferation of cultured cells when these reagents were added in low concentrations. Higher concentrations (above 1 mM) of cysteine were not cytotoxic. Furthermore, high concentrations of L-cysteine partially protected against spermidine oxidation toxicity. D-cysteine on its own behaved exactly the same as an equimolar concentration of L-cysteine, but instead of protecting against the effects of spermidine oxidation, the inhibition was enhanced. A possible mechanism for the interaction is discussed.     

Volatilization of mutagens from beef during cooking

The process of cooking beef substances which are mutagenic in the Ames Salmonella/microsome bioassay [1,2]. In this study, the formation and disposition of basic mutagens produced by cooking beef at different temperatures were examined. Mutagenic activity increased exponentially with cooking temperature between 137 degrees C and 252 degrees C. However, the amount of mutagenic activity remaining in the meat was only 1--7% of that which was volatilized into the air. The ingested dose of mutagens may therefore be significantly influenced by factors which restrict the dissipation of mutagens from the container, as well as by cooking temperature. Inhalation of airborne mutagens from cooking, as an alternative route of exposure, should be investigated when considered in light of some epidemiological data showing an excess of lung and bladder cancer among cooks and kitchen workers.     

Decreased beta-adrenergic responsiveness in mouse epidermal papillomas during tumor promotion with phorbol myristate acetate

The response to the beta-adrenergic agonist (-)-isoproterenol in mouse epidermis and in papillomas arising during tumor promotion with phorbol myristate acetate was determined by measurement of cyclic AMP levels after in vivo administration of (-)-isoproterenol. Papillomas exhibited less than half the hormonal responsiveness found in epidermis from control groups or from papilloma-bearing animals. No difference in the incorporation of labelled (-)-isoproterenol into epidermal or papilloma tissue was seen.     

Determination of serum galactosyltransferase levels in ovarian cancer patients for the evaluation of the effectiveness of therapeutic programs

The activity of galactosyltransferase using endogenous acceptor(s), (GT-En) in the sera of ovarian cancer patients was significantly higher than age and blood-group matched controls. GT-En, and galactosyltransferase activity using an exogenous acceptor (GT-Ex), were assayed in the sera of 30 patients undergoing treatment for ovarian epithelial cancer, at the start of chemotherapy, and after a suitable interval. The direction of the alterations in levels of both these enzymes correctly reflected the clinical response to chemotherapy in most of these patients. The assay of GT-En and GT-Ex in the serum may ge useful for the evaluation of the effectiveness of therapeutic programs in these patients.     

Association of a 97 kilodalton glycoprotein with human ovarian carcinoma

The association of a 97 kilodalton glycoprotein (97k-GP) with human ovarian epithelial tumors is reported. The 97k-GP has been found to be present in elevated levels in all the 8 serous cystadenocarcinoma specimens tested. This glycoprotein is present in small amounts in endometrial tumors and either absent or present in trace amounts in control ovaries. Subcellular localization of this glycoprotein indicates that it is a component of plasma membrane.     

Gamma glutamyl transpeptidase activity in rat urothelium treated with bladder carcinogens

Gamma glutamyl transpeptidase (GGT) activity during urothelial carcinogenesis was examined histochemically in rats treated with N-methyl-N-nitrosourea (MNU) or N-butyl-N-(4-hydroxybutyl)nitrosamine (BHBN). GGT-positive cells developed with a high frequency in foci of nodulopapillary hyperplasia and carcinoma. GGT-positive cells, both individually and in nests, were also frequent in foci of simple hyperplasia and interlesion normal urothelium of carcinogen-treated bladders. The results suggest that development of GGT-positive cells in interlesion normal urothelium is specific to carcinogen treatment.     

Binding of [14C]azaserine to DNA and protein in the rat and hamster

The binding of [¹⁴C]azaserine or its metabolites to DNA and protein in the organs of rats and hamsters was determined at various times after treatment with [¹⁴C]azaserine. The specific activity of ¹⁴C labelling of DNA and protein was determined. Rat liver DNA and protein were most extensively labelled at 90 min post-injection, but by 24 h the specific activity decreased to the levels found in pancreas and kidney. Thymus contained negligible amounts of radioactivity at all time-points. DNA and protein from hamster pancreas contained more label than did DNA and protein from rat pancreas. The results suggest that factors other than DNA binding play a role in determining the species and organ specificity of azaserine.     

Antitumor effect of a combination of 6-methylthioinosine and amphotericin B on mouse leukemia L1210

Antileukemic activity of 5 kinds of sulfur-containing purine ribonucleosides were examined in the presence and absence of amphotericin B against L1210 in mice. Among these compounds, 6-methylthioinosine was potentiated by amphotericin B. 6-Methylthioinosine in combination with amphotericin B produced a 75% increase in the lifespans, which was greater than the increase in lifespans by 6-methylthioinosine (38%) or amphotericin B alone (2%).Antitumor effects of other sulfur-containing ribonucleosides, such as 6-thiocyanatoguanine, 6-thiocyanatopurine, 6-thiocyanatoinosine, and 6-methylthiopurine, were not augmented by amphotericin B.     

Metabolism and biliary excretion of trimetrexate by the isolated perfused rat liver

The metabolism and biliary excretion of trimetrexate (TMTX), a lipid soluble antifolate, were examined using a recirculating isolated perfused rat liver system. Elimination of TMTX into perfusate was biphasic and dose-independent, with distribution and elimination half-lives of 2 and 13 min. Two metabolites, M1 and M2, both known to inhibit dihydrofolate reductase activity, were present in perfusate only in small concentrations. However, of the total TMTX dose, approximately 50% was excreted in bile as M1, and 20% as M2. Up to 75% of the total dose was accounted for as TMTX, M1, or M2 in perfusate and bile.     

In utero effects of 1,2-dimethyl hydrazine on adenosine and guanosine 3',5'-cyclic monophosphate content in rat fetal intestine

Sperm positive 12-14-day pregnant Holtzman rats were exposed to a single subcutaneous injection (20 mg/kg body wt) of 1,2-dimethylhydrazine (DMH). Two days post-exposure, the fetal intestinal tissues were examined for their content and metabolic activities for cyclic 3',5'-adenosine monophosphate (cAMP) and cyclic 3',5'-guanosine monophosphate (cGMP). The in utero exposure to the carcinogen resulted in lowering the intracellular content of cAMP and increasing cGMP. The decreased levels of cAMP may be accounted for the finding of a corresponding increase in its breakdown by its phosphodiesterases; however, associated with the increase in cGMP was correspondingly an increase in its phosphodiesterases, suggesting the activities for synthesis of this cyclic nucleotide may be the major factor for its elevated concentration. These observations indicate that DMH may cross the placental barrier and can effect the intracellular cyclic nucleotide concentrations in the fetal tissues as well as acting as a colorectal carcinogen in the adult rat. The changes in the cyclic nucleotide levels were toward the direction expected for an increased cell proliferation; consequently, further investigations are suggested to determine whether a hyperproliferative state is induced by the DMH in the already rapidly dividing fetal intestinal tissue.     

Rapid lipid peroxidation in the nuclear fraction of rat liver induced by a diet deficient in choline and methionine

A diet deficient in choline and methionine, known to produce hepatocellular carcinoma in the absence of any added chemical carcinogen, induced lipid peroxidation in the nuclear fraction of the liver when fed to male Fischer 344 rats. This lipid peroxidation was detected within 1 day of feeding the diet by the appearance of diene conjugates and increased progressively up to 3 days. It was prevented completely by the addition of choline chloride to the diet. The close proximity of DNA may make it a possible target for attack by free radicals.     

Combined effect of the extracts from Croton tiglium,Euphorbia lathyris or Euphorbia tirucalli and n-butyrate on Epstein-Barr virus expression in human lymphoblastoid P3HR-1 and Raji cells

The combined usage of n-butyrate and 12-O-tetradecanoylphorbol-13-acetate (TPA) or the oily extracts from Croton tiglium, Euphorbia lathyris or Euphorbia tirucalli exerted a marked effect on induction of Epstein-Barr virus (EBV)-associated early (EA) and viral capsid (VCA) antigens in EBV genome-carrying human lymphoblastoid cell lines. In producer P3HR-1 cells, the enhancing effect of the 2 components was additive both for EA and VCA, while in non-producer Raji cells, a synergistic increase of EA was observed. The possible implication of these findings relating to the cause of EBV-associated diseases is discussed.     

Effect of selenium on azoxymethane-induced intestinal cancer in rats fed high fat diet

The effects of selenium supplementation on azoxymethane-induced intestinal cancer were studied in male Sprague-Dawley rats given 8 weekly injections of azoxymethane (8 mg/kg body wt), and fed a 30% beef fat diet. Selenium-supplemented groups received 8 ppm H₂SeO₃ in drinking water. Blood selenium levels of supplemented rats increased rapidly the first 9 weeks of the experiment, followed by a plateau significantly higher than that for non-selenium controls. There was a significant increase in liver and intestinal selenium levels in supplemented groups.The average number of intestinal tumors was 6.5 in the control group, and 3.1 in the selenium-supplemented group. There was a significant reduction in tumor incidence in the proximal half of the colon of selenium-treated rats. There was also increased concentration of tissue selenium in the proximal half of the colon of these rats.