Tumors of female offspring of mice exposed prenatally to diethylstilbestrol

Strain CD-1 female mice exposed prenatally to diethylstilbestrol (DES) (CAS: 56-53-1; alpha,alpha'-diethyl-4,4'-stilbenediol) were mated to unexposed males. Female offspring of these matings were raised to the stage of terminal illness. They were never exposed to DES and so have been referred to as "DES-lineage mice." Ten uterine adenocarcinomas and 5 ovarian cystadenocarcinomas were found in 40 DES-lineage mice. These findings were significantly different from the absence of such tumors in 24 "vehicle-lineage" mice whose mothers had received injections only of oil and alcohol. The types of tumors that commonly occur spontaneously in the CD-1 strain appeared with comparable frequency in the 2 groups of mice. The DES-lineage mice did not show the increased frequency of adenomyosis and squamous metaplasia of the uterus, nor the reduced frequency of corpora lutea seen in mice exposed prenatally to DES.     

Prolonged survival of female AKR mice fed diets supplemented with methionine and choline

Female mice of the AKR/J (AK) strain were fed a control diet (Purina Rodent Laboratory Chow) or a lipotrope-supplemented diet (Purina Rodent Chow plus 2% D,L-methionine and 1% choline chloride) beginning at 1 day after weaning. Food consumption and weight gain were found to be the same in both groups of animals. Mice of this inbred strain spontaneously develop thymic lymphoma, with close to 100% mortality expected by 12-13 months of age. Two separate experiments were carried out with 50 mice per group in one, and 40 mice per group in the other. The slopes of the survival curves for the animals in the control group and supplemented group of mice diverged after the animals reached 6.5 months of age. In both experiments, 20% of the mice receiving supplemented diet were still alive at 1 year, while 3% in one experiment and 8% in the other experiment survived in the control groups. Each experiment was terminated when the animals reached 13 months of age. At that time the survival rate of the controls was 2 and 4%, and survival in the groups of mice receiving supplemented diet was 14 and 18%. Necropsy revealed that the animals in both groups had advanced malignant lymphoma. Our results demonstrate that intake of a chow diet that is supplemented with moderate quantities of methionine and choline results in enhanced survival of spontaneously leukemic AK mice, in comparison with animals of this strain fed the same diet without supplements of choline and methionine.     

Inhibition of DMBA-induced mammary tumorigenesis by caloric restriction in rats fed high-fat diets

Most previous studies on the inhibiting effect of caloric restriction during promotion of DMBA-induced mammary carcinogenesis have used low to moderate levels of dietary fat, i.e., about 4 to 14% by weight. The current study was designed to test whether a moderate degree of caloric restriction, 25%, would inhibit tumor growth in rats fed the equivalent of 20% dietary fat which approximates human consumption in affluent countries. Rats were fed diets ad libitum that contained 5, 15 or 20% corn oil. Groups of rats were pair-fed to the last 2 groups, but subjected to a 25% caloric restriction. These groups were fed 20 or 26.7% corn oil so that absolute fat intake in the paired groups was identical. Significant inhibition of tumor incidence, tumor weight, tumor burden, body fat deposition, and fasting serum insulin were observed in the 2 calorically restricted groups. We conclude that moderate caloric restriction is significantly more effective in inhibiting tumor growth than is the promoting effect of diets high in fat. Total body weight, body fat and serum insulin concentrations may be better correlates of risk of developing mammary tumors than is dietary fat.     

Altered tRNA methylation in rats and mice fed lipotrope-deficient diets

A diet that is deficient in methionine, choline, folic acidand vitamin B₁₂ has been found to induce alterations rapidlyin liver tRNA methylation in male Fischer rats. In vitro assaysindicated that activity of N2-guanine tRNA methyltransferaseII (NMG2) was increased to 150% of controls levels in 1 weekand 300% of control levels after 2 weeks or longer on this diet.Incompletely methylated tRNA was isolated from livers of thesesame animals, indicating that there was impairment of methylationin vivo. The effects on liver tRNA methylation of this methyl-deficientdiet were thus seen to mimic those of the liver carcinogen,ethionine, which also causes production of hypomethylated tRNAand increased activity of NMG2. The effect of the same dieton liver tRNA methyltransferase activity of C57BL/6J and C3H/HeJinbred mice were also studied. Intake of the lipotrope-deficientdiet Induced elevation in activity of liver N2-guanine tRNAmethyltransferase II activity in C57BL/6J mice, similar to thatseen in rats. In contrast, the methyl-deficient diet had verylittle effect on the same enzyme activity in C3H/HeJ animals.     

Histopathology of neoplastic and nonneoplastic hepatic lesions in mice fed diets containing tetrachlorvinphos.

Tetrachlorvinphos was fed at 8,000 or 16,000 ppm in diets to male and female (C57BL/6N X C3H/HeN)F1 mice for 80 weeks. Surviving mice were killed at 92 weeks, and all mice were completely necropsied. A high incidence of unusual nonneoplastic hepatic lesions in treated mice was present and characterized by pericellular fibrosis, hepatocyte nuclear pleomorphism, and intrasinusoidal foci of macrophages with intracytoplasmic crystalline structures. From 84 to 94% of the treated male mice and from 21 to 23% of the treated females had hepatocellular neoplasms. Only 17% of the control males and 7% of the control females had liver tumors. The induced tumors were frequently multiple in the liver, whereas the tumors in the controls were usually singular. The morphology of 241 liver tumors in 110 treated mice was different from that of tumors in controls. Liver tumors in control mice were generally composed of small basophillic hepatocytes. In treated mice, tumors were hepatocellular carcinomas composed of solid sheets of large basophilic or eosinophilic hepatocytes. Foci of prominent trabecular formation were seen in 51 tumors. Fifteen tumors were composed of small basophilic hepatocytes with oval cells interposed among them. Foci of capillary formation were noted in 3 of these tumors. In addition, 7 more typical hemangiosarcomas forming sinusoids and with thrombosis were observed.     

Prevention of murine sarcoma virus oncogenesis in offspring of immunized female mice

BALB/c mice born to and nursed by females immunized against MSV-M showed a reduced tumour incidence and a high tumour regression rate following MSV-M injection at 7-14 days of age. Females immunized long before mating could also confer protection to their offspring whereas females immunized after parturition could not. A reduced number of tumours was observed in 3 out of 14 MSV-M injected litters whose mothers had been previously exposed to the virus while nursing infected offspring. Sera from suckling mice born to and nursed by immunized mothers contained MSV-M neutralizing antibody as shown by an in vitro focus reduction assay. Cell-free extracts from mice which developed leukaemia after MSV-M inoculation were tested for oncogenic activity in 1-week old mice. Out of 6 extracts, 4 induced typical MSV-M tumours and 2 caused leukaemias.     

Different weekly changes in immune response in virus-transformed cell-injected mice fed two different diets

Changes in tumor development and in certain immune responses were investigated at 7-weekly intervals after subcutaneous injection of 5 X 10(5) herpes simplex virus Type 2-transformed cells (H238 cells) into male BALB/c mice fed 2 different diets. One diet contained 11% casein and 5% fat while the other had 11% supplemented wheat gluten and 30% fat. Weanling mice (140/group) were fed one or the other of the diets for 12 weeks before injection and subsequent testing of 15 injected and 5 non-injected mice from each diet group each week. In mice fed the low-fat diet containing casein both tumor incidence and tumor volume were significantly lower (P less than or equal to 0.05) than in the group fed the 30% fat diet containing supplemented wheat protein. The casein-fed mice also had less splenomegaly and a higher proportion of mature lymphocytes in the spleen during tumor growth. The proliferative capability of the spleen cells after phytohemagglutinin stimulation was enhanced 2 weeks after H238 cell injection only in the casein-fed mice.     

Inhibition of initiator-promoter-induced skin tumorigenesis in female SENCAR mice fed a vitamin A-deficient diet and reappearance of tumors in mice fed a diet adequate in retinoid or beta-carotene

Retinoids have chemopreventive activity for epithelial tumors in a variety of systems, including the two-stage tumorigenesis system of mouse skin in which only the promotion stage is inhibited. We asked whether dietary vitamin A deficiency could affect the skin tumorigenic response, prior to major changes in body weight or general health of the animals. Two regimens were tested to induce vitamin A deficiency. SENCAR mice were either (a) fed a vitamin A-deficient diet from 4 or 9 weeks of age or (b) their mothers were fed the diet from the time of birth of the experimental animals which were then weaned on the same diet. The latter regimen produced typical symptoms of vitamin A deficiency in the offspring by Weeks 12-14 and all the mice died by Week 19; the former regimen permitted sufficient accumulation of retinol and its esters to sustain life for up to 45 and 75 weeks, respectively, in the majority of mice. For our experiments, vitamin A depletion was produced by placing the mothers on the deficient diet at birth of the experimental animals. A single topical dose of 20 micrograms of 7,12-dimethylbenz(a)anthracene (DMBA) was used as the initiator at 3 weeks of age and 1 to 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate (TPA) once weekly as the tumor promoter for 10 weeks (from Week 4 through 13 of the experiment). Fifty-five % of mice (n = 40) on Purina laboratory chow (mean body weight, 31.4 g) developed skin tumors (2.58 per mouse) at 12 weeks, versus 2.5% (0.05 papillomas per mouse) of mice (n = 40) kept on the purified vitamin A-deficient diet (mean body weight, 30.3 g), a 98% decrease in tumor/mouse. Retinoic acid (RA) (1-3 micrograms/g diet) supplementation after Week 12 caused a rapid tumorigenic response in 95% of the mice by week 22. This tumor response occurred to a reduced extent in the absence of continued TPA treatment up to Week 13. Even though tumor incidence increased within 1 week of RA and 95% of the mice showed the tumorigenic response, the number of tumors per mouse was about 50% of that observed in mice maintained on standard Purina diet. This was confirmed in an experiment in which the mice were maintained for life either on Purina or on the RA (3 micrograms/g) containing purified diet, the latter being the control group for the effect of vitamin A deficiency on skin tumorigenesis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Hepatic DNA methylation and liver tumor formation in male C3H mice fed methionine- and choline-deficient diets

The effects of the chronic administration of methyl-deficient, amino acid-defined diets on liver tumor formation were examined in male weanling C3H/HeN mice previously treated with a single ip injection of 0 or 150 mg diethylnitrosamine/kg body weight [(DENA) CAS: 55-18-5]. Five diets were used: diet 1, adequate; diet 2, devoid of both methionine and choline; diet 3, devoid of methionine only; diet 4, devoid of choline only; and diet 5, devoid of methionine, choline, folic acid, and vitamin B12. Equimolar homocystine replaced methionine in all methionine-devoid diets. All diets were administered for 1 year. No hepatocellular carcinomas and only 3 liver adenomas were seen among the 129 animals at risk in the 5 groups that had received no DENA. Among the DENA-treated groups fed diets 1-4, the incidence of hepatocellular carcinomas in the mice at risk averaged 40%, with no significant differences noted among groups. A relatively low incidence of liver carcinomas (10%) was seen among DENA-treated mice subsequently fed diet 5; it could be ascribed to the enhanced mortality seen in these animals due to the dietary deficiencies. Lung tumors were seen in 44% of the DENA-treated mice surviving more than 35 experimental weeks and in only 2.5% of the corresponding DENA-untreated animals. Feeding diet 2, deficient in methionine and choline, to male C3H mice for 5-20 weeks decreased the hepatic ratio of S-adenosylmethionine (CAS: 29908-3-0) to S-adenosylhomocysteine (979-92-0) relative to that observed in mice fed the adequate diet 1. The 5-methyldeoxycytidine [(5-MC) CAS: 838-07-3] contents of liver DNA in animals fed diet 2 for 5, 10, and 20 weeks, however, were not significantly different from the corresponding levels in diet 1-fed mice. The results indicate that a methionine- and choline-deficient dietary regimen that lowers the 5-MC levels in DNA and enhances liver tumor formation in male F344 rats does not do so in male C3H mice.     

Hepatocarcinogenesis in rats fed methyl-deficient, amino acid-defined diets

The ability of methyl-deficient, amino acid-defined diets toproduce liver tumors was studied in rats treated both with andwithout initiating doses of diethylnitrosamine (DENA). Male,weanling F344 rats were fed a complete, amino acid-defined dietfor one week. They were then injected once i.p. with one of3 doses of DENA (20, 70 or 200 mg/kg body weight) and fed thecomplete diet for an additional week. Thirty animals from eachdose group were then maintained for 76 weeks on the completediet (Diet 1) or one of 4 methyl-deficient diets: Diet 2, devoidof methionine and choline; Diet 3, devoid of methionine only;Diet 4, devoid of choline only and Diet 5, devoid of methionine,choline, folic acid and vitamin B₁₂. In Diets 2, 3 and 5 methioninewas replaced by equimolar amounts of its metabolic precursorDL-homocystine. Control rats were injected i.p. with the salinevehicle and maintained for the 76-week period on Diets 1 and2. Forty percent of the rats fed Diet 2, but receiving no DENA,developed hepato-cellular carcinomas or cholangiomas. A 90–100%incidence of hepatocellular carcinomas was seen in all groupsinitiated with DENA and fed Diet 2. No malignant liver tumorsdeveloped in Diet 1 rats that had received 0 or 20 mg/kg DENA;however, hepatocellular carcinomas were noted in one-half ofsuch animals receiving the 70 and 200 mg/kg doses. Liver metastasesgrew in the lungs of 60% of the tumor-bearing rats fed Diet2; none were seen in the Diet 1-fed rats. The singly deficientDiets 3 and 4 enhanced liver tumor formation to DENA-initiatedrats to a significantly lesser extent than did Diet 2. All DENA-initiatedrats fed the severely deficient Diet 5, died within 23 experimentalweeks with livers containing hepatocytes of atypical appearanceand, particularly at the 2 higher dosages, a cirrhotic pseudo-nodulararchitecture. No hepatocellular carcinomas or cholangiomas wereobserved in Diet 5-fed rats. None of the diets tested appearedto enhance tumor formation in extra-hepatic tissues. In fact,significant decreases were noted in the formation of spontaneoustesticular interstitial cell tumors in Diet 2-fed rats and ofpancreatic acinar tumors in rats fed Diets 2 and 3. Diet 2,devoid of both methionine and choline, also induced metaplasiaof pancreatic acinar cells to hepatocyte-like cells and wasasociated with moderate to severe hyperplasia of the transitionalepithelium lining the renal pelvis. Finally, DENA initiationgave weak but significant dose-dependent increases in the incidencesof kidney parenchymal tumors and lung bronchioalveolar celltumors that could not be directly correlated with the extentof methyl deprivation. The results indicate that dietary methyldeficiency markedly promotes liver carcinogenesis and exhibitscomplete carcinogenic activity in this organ in the rat.     

Effects of high-fat diets rich in either omega-3 or omega-6 fatty acids on UVB-induced skin carcinogenesis in SKH-1 mice

Our previous studies reported that caffeine or voluntary exercise decreased skin tumor multiplicity, in part, by decreasing fat levels in the dermis. These data suggest that tissue fat may play an important role in regulating ultraviolet light (UV) B-induced skin tumor development. In the present study, we explored the effects of high-fat diets rich in either omega-3 or omega-6 fatty acids on UVB-induced skin carcinogenesis. SKH-1 mice were irradiated with 30 mJ/cm(2) of UVB once a day, two times per week for 39 weeks. During UVB treatment, one group of mice was given a high-fat fish oil (HFFO) diet rich in omega-3 fatty acids and the other group of mice was given a high-fat mixed-lipids (HFMLs) diet rich in omega-6 fatty acids. The results showed that, compared with HFML diet, HFFO treatment (i) increased latency for the development of UVB-induced skin tumors; (ii) decreased the formation of papilloma, keratoacanthoma and carcinoma by 64, 52 and 46%, respectively and (iii) decreased the size of papilloma, keratoacanthoma and carcinoma by 98, 80 and 83%, respectively. Mechanistic studies with antibody array revealed that compared with HFML diet, administration of HFFO to the mice significantly decreased the UVB-induced increases in the levels of TIMP-1, LIX and sTNF R1 as well as other several proinflammatory cytokines and stimulated the UVB-induced apoptosis in the epidermis. Our results indicate that omega-3 fatty acids in HFFO diet have beneficial effects against UVB-induced skin carcinogenesis, and these effects may be associated with an inhibition on UVB-induced inflammatory response.     

Inhibition of lymphocyte function in rats fed higher-fat diets.

Concanavalin A-induced blastogenesis of spleen lymphocytes was significantly inhibited when lymphocytes from rats on a high-polyunsaturated-fat diet were compared to lymphocytes from rats on a low-fat diet. Responsiveness was dependent on source of serum since lymphocytes from rats fed a low-fat diet were suppressed in serum from rats fed a high-polyunsaturated-fat diet. Alternatively, lymphocytes from rats on a high-polyunsaturated-fat diet were more responsive in serum from low-fat-fed rats compared to their response in autologous serum. One of the inhibiting factors in serum was the lipoprotein fraction; however, rats on a high-polyunsaturated-fat diet probably had additional inhibitors in their serum. While tumor incidence was highest in rats with the least responsive lymphocytes was highest in rats with the least responsive lymphocytes and lowest in rats with the most responsive lymphocytes, the significance of the observation is not known.     

Chemoprevention of intestinal polyps in ApcMin/+ mice fed with western or balanced diets by drinking annurca apple polyphenol extract

The Western diet (WD) is associated with a higher incidence of colorectal cancer (CRC) than the Mediterranean diet. Polyphenols extracted from Annurca apple showed chemopreventive properties in CRC cells. A multifactorial, four-arm study by using wild-type (wt) and Apc(Min/+) mice was carried out to evaluate the effect on polyp number and growth of APE treatment (60 μmol/L) ad libitum in drinking water combined with a WD or a balanced diet (BD) for 12 weeks. Compared with APE treatment, we found a significant drop in body weight (P < 0.0001), severe rectal bleeding (P = 0.0076), presence of extraintestinal tumors, and poorer activity status (P = 0.0034) in water-drinking Apc(Min/+) mice, more remarkably in the WD arm. In the BD and WD groups, APE reduced polyp number (35% and 42%, respectively, P < 0.001) and growth (60% and 52%, respectively, P < 0.0001) in both colon and small intestine. Increased antioxidant activity was found in wt animals fed both diets and in Apc(Min/+) mice fed WD and drinking APE. Reduced lipid peroxidation was found in Apc(Min/+) mice drinking APE fed both diets and in wt mice fed WD. In normal mucosa, mice drinking water had lower global levels of DNA methylation than mice drinking APE. APE treatment is highly effective in reducing polyps in Apc(Min/+) mice and supports the concept that a mixture of phytochemicals, as they are naturally present in foods, represent a plausible chemopreventive agent for CRC, particularly in populations at high risk for colorectal neoplasia.     

Promoting effects of high-fat corn oil and high-fat mixed lipid diets on 7,12-dimethylbenz[a]anthracene-induced mammary tumorigenesis in F344 rats

Epidemiological studies and laboratory animal model assays suggest that a high intake of dietary fat promotes mammary carcinogenesis as well as colon tumorigenesis. Fat intake in the United States traditionally includes high amounts (30% of total caloric intake) of saturated fatty acids (SFAs) compared to polyunsaturated fatty acids (PUFAs). A recent study suggested that a high-fat mixed-lipid diet (HFML), which simulates the mixed-lipid and high SFAs composition of the average American diet, strongly promotes rat colon carcinogenesis, even when compared to another high-fat diet containing PUFA-rich corn oil. On the other hand, some reports suggest that a high-fat diet rich in n-6 PUFAs promotes mammary carcinogenesis more strongly than a high-fat diet rich in SFAs. Therefore, the present study was designed to compare the effects of HFML, high-fat corn oil diet (HFCO) that is rich in n-6 PUFAs, and a low-fat corn oil diet (LFCO) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis in female F344 rats. At 7 weeks of age, female F344 rats intended for carcinogen treatment received a gavage of DMBA at a dose level of 65 mg/kg of body weight. Beginning 1 week after carcinogen treatment, groups of rats were then maintained on experimental diets containing LFCO, HFCO or HFML. All rats were evaluated weekly by palpation of mammary tumors and sacrificed 20 weeks after the DMBA treatment. Palpable tumors of mammary glands were detected at the 8, 11, and 19 weeks in the HFCO, HFML and LFCO groups, respectively. Histopathological observation revealed that the incidence and number of mammary tumors in the HFCO group were significantly higher than in the LFCO group. Rats on the HFML diet tended towards a higher incidence and number of mammary tumors compared with the LFCO group, although the correlation was not statistically significant. These results suggest that, for this animal model, both the HFCO and HFML diets promote DMBA-induced mammary carcinogenesis when compared to the LFCO diet, and that the HFCO diet is more tumor-promotional than the HFML diet.