Effects of NSAIDs on NNK-induced pulmonary and gastric tumorigenesis in A/J mice.

Non-steroidal anti-inflammatory drugs (NS-AIDs) are among the most widely prescribed drugs. In this study, we compared the efficacies of four NSAIDs to inhibit lung tumorigenesis in A/J mice. The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), was given in drinking water between week 0 and week +7. Groups of 25 mice were fed sulindac (123 mg/kg diet), ibuprofen (263 mg/kg), piroxicam (25 mg/kg) or naproxen (230 mg/kg) in AIN-76A diet from week -2 to the end of the bioassay (week +23). Sulindac was the most effective inhibitor and reduced lung tumor multiplicity by 51%. Ibuprofen and piroxicam reduced lung multiplicity by 38% and 30%, respectively. Naproxen demonstrated no inhibitory capacity. Forestomach tumor multiplicity and incidence were both reduced by sulindac and ibuprofen. Sulindac administered from week -2 to week +7 was less effective (28% inhibition) than when given throughout the bioassay. Sulindac induced more intestinal adhesions than any other NSAID and was directly related to the cumulative dose of sulindac. These results show that chemoprevention of lung tumorigenesis by NSAIDs is not limited to sulindac although it is the most effective.     

A Cyp2a polymorphism predicts susceptibility to NNK-induced lung tumorigenesis in mice

Lung tumors from smokers as well as lung tumors from mice exposed to tobacco carcinogens such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), often carry mutations in K-ras, which activates downstream-signaling pathways such as PI3K/AKT/mTOR pathway. Mice with genetic deletion of one of three isoforms of AKT were used to investigate the role of AKT in mutant K-ras-induced lung tumorigenesis in mice. Although deletion of Akt1 or Akt2 decreased NNK-induced lung tumor formation by 90%, deletion of Akt2 failed to decrease lung tumorigenesis in two other mouse models driven by mutant K-ras. Genetic mapping showed that Akt2 was tightly linked to the cytochrome P450 Cyp2a locus on chromosome 7. Consequently, targeted deletion of Akt2 created linkage to a strain-specific Cyp2a5 polymorphism that decreased activation of NNK in vitro. Mice with this Cyp2a5 polymorphism had decreased NNK-induced DNA adduct formation in vivo and decreased NNK-induced lung tumorigenesis. These studies support human epidemiological studies linking CYP2A polymorphisms with lung cancer risk in humans and highlight the need to confirm phenotypes of genetically engineered mice in multiple mouse strains.     

Lack of modifying potential of 8-methoxypsoralen in the promotion or progression stages of lung carcinogenesis in A/J female mice

Pretreatment with 8-methoxypsoralen (8-MOP), a potent human CYP2A6 inhibitor, strongly suppresses lung tumorigenesis by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in female A/J mice. Since it has been reported that CYP2A protein is highly expressed in NNK-induced lung adenomas and adenocarcinomas, potential anticancer properties of 8-MOP in female A/J mice were examined subsequent to initiation. The agent was administered at 100 ppm levels in the diet during the promotion phase (experimental weeks 1-16) and progression phase (experimental weeks 16-32) and mice were sacrificed for histopathological examination of lung tumor development at 16 and 32 weeks after the initiation of NNK treatment (2 mg/0.1 ml saline/mouse, i.p.), respectively. Chemopreventive effects of 8-MOP were not observed in either experiment. In addition, no modifying effects on hepatic mRNA levels for CYP2A5, considered to be the mouse ortholog of human CYP2A6, were evident. On immunohistochemical analysis, the CYP2A protein was found to be overexpressed in all lung adenomas and adenocarcinomas, with or without 8-MOP. It can be concluded from the present data that 8-MOP at 100 ppm in the diet does not prevent mouse lung carcinogenesis when administered in the post-initiation phase.     

Post-initiation chemopreventive effects of dietary bovine lactoferrin on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in female A/J mice

We investigated the effects of bovine LF (bLF) on different phases of NNK-induced lung tumorigenesis in A/J mice. Mice were orally administered 0.02, 0.2 and 2% bLF during the initiation phase, and 2% bLF during the whole tumorigenesis phase or post-initiation phase. Administered bLF during the post-initiation phase showed significant reduction of macroscopical lung nodules, and immunohistochemically decreased expression levels of cell proliferation marker and increased expression levels of apoptosis marker in lung proliferative lesions. bLF might inhibit NNK-induced mouse lung tumorigenesis, only when given limited to the post-initiation phase, through modification of cell proliferation and/or apoptosis.     

Effects of alkyl chain length on the inhibition of NNK-induced lung neoplasia in A/J mice by arylalkyl isothiocyanates

Six homologous arylalkyl isothiocyanates were evaluated fortheir abilities to inhibit pulmonary adenomas induced by thetobacco-specific nitrosamine 4-(methylnitrosamino)-l-(3-pyridyl)-1-butanone(NNK) in A/J mice. Four consecutive daily doses (5 µmol/mouse)of phenyl isothiocyanate (PITC), benzyl isothiocyanate (BITC),phenethyl isothiocyanate (PETTC), 3-phenylpropyl isothiocyanate(PPITC), 4-phenylbutyl isothiocyanate (PBITC), 4-oxo-4-(3-pyridyl)-butylisothiocyanate (OPBITC) and corn ofl were administered to miceby gavage. Two hours following the final dosing, mice were administeredsaline or 10 µmol of NNK in saline i.p. Pulmonary adenomaswere counted at 16 weeks after NNK administration. The miceadministered only corn oil prior to NNK developed an averagemultiplicity of 9.2 tumors/ mouse. Pretreatment with PITC, BITCand OPBITC had no significant effects on NNK-induced lung neoplasia.However, PEITC pretreatment resulted in a 64% reduction of lungtumor multiplicity, but did not affect the percentage of micethat developed tumors. Both PPITC and PBITC decreased tumormultiplicity by 96% and the percentage of tumor-bearing animalsby >60%. These results, in conjunction with our previouswork, demonstrate a general trend of increasing inhibition ofNNK-induced lung neoplasia by arylalkyl isothiocyanates withincreasing alkyl chain length. This study also demonstratesthe remarkable inhibitory activities of PPITC and PBITC, twoisothiocyanates that had not previously been tested as chemopreventiveagents.     

Chemopreventive efficacies of aspirin and sulindac against lung tumorigenesis in A/J mice

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed drugs. In this study, we demonstrated the efficacy of aspirin to inhibit lung tumorigenesis in A/J mice. Lung tumors (9.9 tumors/mouse) were induced by the tobacco-specific nitrosamine, 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), administered in drinking water between week 0 and week +7. Groups of mice were fed sulindac (123 mg/kg diet), acetylsalicylic acid (ASA; 294 mg/kg), non- buffered Aspirin (294 mg/kg) or buffered Aspirin (294 mg/kg) in AIN-76A diet from week -2 to the end of the bioassay (week +23). These doses are comparable to the maximal doses recommended for humans. ASA and non- buffered Aspirin were the most effective inhibitors and reduced lung multiplicities by 60 and 62%, respectively. Sulindac inhibited lung tumor multiplicity by 52%. Inhibition by buffered Aspirin was not statistically significant. We evaluated the efficacies of NSAIDs to inhibit NNK activation by h1A2 v2 cells expressing human P-450 1A2. Salicylates, at doses of 500 microM and 1 mM, had no effect on NNK activation. Sulindac and its sulfide and sulfone metabolites (1 mM) inhibited NNK metabolism by 90, 92 and 65%, respectively. We observed a 76% inhibition with SKF 525A, a P-450 inhibitor. Taken together, these results indicate that salicylates and sulindac could be equally effective as chemopreventive agents, but they could differ in their mode of action.      

Dietary selenium fails to influence cigarette smoke-induced lung tumorigenesis in A/J mice

The goal of the study was to determine if dietary selenium inhibited the induction of lung tumorigenesis by cigarette smoke in A/J mice. Purified diets containing 0.15, 0.5, or 2.0 mg/kg selenium in the form of sodium selenite were fed to female A/J mice. Half of the mice in each dietary group were exposed to cigarette smoke 6 h/day, 5 days/week for five months followed by a four month recovery period in ambient air, while the other half were used as controls. After the recovery period, the mice were euthanized, and their lungs were removed for further analysis. Mice exposed to smoke had a higher tumor incidence and a higher tumor multiplicity, whereas dietary Se did not affect either the tumor incidence or tumor multiplicity. An increase in dietary selenium led to increased levels of selenium in the lung as well as GPx protein levels, but dietary Se did not affect lung SOD protein levels. In conclusion, these data confirm the carcinogenic activity of cigarette smoke in mice but show that dietary Se provided as sodium selenite does not affect smoke-induced carcinogenesis in this model.     

Pretreatment with 8-methoxypsoralen, a potent human CYP2A6 inhibitor, strongly inhibits lung tumorigenesis induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in female A/J mice

Human CYP2A6 has been recognized as being involved in the mutagenic activation of promutagens such as the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Methoxsalen (8-methoxypsoralen) was reported to inhibit CYP2A6. In the present study, the inhibitory effects of methoxsalen on NNK-induced lung tumorigenesis in female A/J mice were examined. Female A/J mice were treated with methoxsalen at doses of 50 or 12.5 mg/kg body weight, given by stomach tube, daily for 3 days. One h after the final treatment, NNK was injected i.p. at a dose of 2 mg/mouse. The experiments were terminated 16 weeks after the first methoxsalen treatment, and lung adenomas were analyzed. Pretreatment of methoxsalen significantly reduced tumor incidence from 93.8% to 16.7% (50 mg/kg) and 20.0% (12.5 mg/kg), and tumor multiplicity from 5.97 to 0.23 (50 mg/kg) and 0.25 (12.5 mg/kg) tumors/mouse. These results clearly demonstrated that methoxsalen, a potent human CYP2A6 inhibitor, is a strong chemopreventive agent against NNK-induction of lung tumorigenesis.     

(-)-Epigallocatechin gallate can prevent cisplatin-induced lung tumorigenesis in A/J mice

Risks of secondary lung cancer in patients with non-small cell lung cancer and small cell lung cancer are estimated to be 1-2% and 2-10% per patient per year, respectively. Cisplatin is widely used in the treatment of lung cancer and is also known as a carcinogen in experimental animals. In this study, the effect of (-)-epigallocatechin gallate (EGCG) on cisplatin-induced lung tumors in A/J mice was investigated. Female A/J mice (4 weeks old) were divided into four groups: group 1, control without treatment; group 2, EGCG treatment (1 mg/ml in tap water); group 3, weekly cisplatin treatment (1.62 mg/kg body wt, i.p.) for 10 weeks; group 4, cisplatin plus EGCG treatment (EGCG was started 2 weeks before cisplatin treatment). Four groups of mice were killed at week 30 after treatment. Tumor incidence was 26.3% (5/19) in group 1, 30% (6/20) in group 2, 100% (19/19) in group 3 and 94.4% (17/18) in group 4. Tumor multiplicity (the number of tumors per mouse, mean +/- SD) was 0.4 +/- 0.8 in group 1, 0.4 +/- 0.8 in group 2, 5.1 +/- 2.1 in group 3 and 2.8 +/- 2.3 in group 4. Tumor multiplicity was significantly reduced by adding EGCG to cisplatin-treated mice (P < 0.01). Furthermore, EGCG significantly reduced cisplatin-induced weight loss from 24.7-26.3% (cisplatin treatment) to 10.8-11.6% (cisplatin plus EGCG treatment) (P < 0.01). These findings suggest that EGCG can inhibit cisplatin-induced weight loss and lung tumorigenesis in A/J mice.     

Ezetimibe reverses the inhibitory effects of dietary cholesterol on mammary tumorigenesis in rats

There are concerns regarding increased cancer incidence in patients treated with ezetimibe, an inhibitor of the absorption of dietary cholesterol. Here we tested the hypothesis that ezetimibe will accelerate mammary tumorigenesis in rats. The drug was administered at a dose of 1 ppm in an AIN‐93G diet that contained 0.3% cholesterol. This experimental diet and control diets that contained either no additions or cholesterol or ezetimibe only, were fed to groups of 30 Sprague‐Dawley rats 3 days after they were treated with 50 mg/kg methylnitrosourea (MNU). All rats were euthanized 22 weeks after MNU administration. Tumor multiplicity was significantly smaller in rats fed cholesterol than those fed no cholesterol (1.84 ± 0.42 vs. 3.86 ± 0.86 respectively, P < 0.05), but was significantly greater in the cholesterol/ezetimibe group than the group fed only cholesterol (3.48 ± 0.59 vs. 1.84 ± 0.42 respectively, P < 0.04). The average weight of tumors/rat was also significantly larger in the cholesterol/ezetimibe group than those fed cholesterol alone (5.67 ± 1.15 vs. 2.56 ± 0.71 respectively, P < 0.04). As expected, ezetimibe prevented the cholesterol raising effect of the dietary cholesterol. These results show that ezetimibe reverses the inhibitory effect of dietary cholesterol on the development of rat mammary tumors.     

Efficacy of deguelin and silibinin on benzo(a)pyrene-induced lung tumorigenesis in A/J mice

We evaluated deguelin and silibinin in A/J mice treated with the tobacco-specific carcinogen benzo(a)pyrene (BP) for their ability to inhibit pulmonary adenoma formation and growth. Animals were treated with either deguelin (5.0 or 10.0 mg/kg body weight, by gavage) or silibinin at doses of 0.05% and 0.1% in the diet, approximately 10 days before a single intraperitoneal dose of BP. We found that oral administration of deguelin reduced tumor multiplicity by 56% and tumor load by 78%, whereas silibinin treatment at doses of 0.05% and 0.1% in the diet did not show any significant efficacy on either tumor multiplicity or tumor load. The result indicates that deguelin significantly inhibits pulmonary adenoma formation and growth in A/J mice. Finding new and effective agents that can prevent lung cancer is urgently needed because cancer of the lungs remains the principal cause of cancer deaths in the United States and because effective chemoprevention of this cancer type remains elusive. Thus, deguelin appears to be a promising new preventive agent for lung cancer and may be considered for further studies in other animal models and in clinical trials.     

Dietary D-glucarate effects on the biomarkers of inflammation during early post-initiation stages of benzo[a]pyrene-induced lung tumorigenesis in A/J mice

Previous studies showed that dietary calcium D-glucarate (CG) inhibited benzo[a]pyrene (B[a]P)-induced A/J mouse lung tumorigenesis, suppressing cell proliferation and chronic inflammation and inducing apoptosis during late post-initiation stages. The present study aimed to investigate changes in the homeostasis of cytokines in blood serum, as well as alterations in biomarkers of inflammation and apoptosis in lung tissue caused by dietary CG during early post-initiation stages of B[a]P-induced lung tumorigenesis. Two doses of 3 mg of B[a]P were given intragastrically to A/J mice 2 weeks apart. CG administration in the AIN-93G diet (2 and 4%, w/w) commenced at 2 weeks following the second dose of B[a]P. The levels of interleukin (IL)-6, IL-10 and tumor necrosis factor α (TNFα) in blood serum were investigated by FCAP array analysis. Two weeks after the second dose of B[a]P, approximately 8- and 28-fold increases of TNFα and IL-6, respectively, occurred in the blood serum and an approximately 16% decrease of IL-10 levels compared to the untreated control group was noted. At 4 weeks after the second dose of B[a]P and after 2 weeks of CG administration in the diet, the 2 and 4% CG diets significantly reduced the levels of IL-6 and TNFα (by 70 and 33%, respectively). In a dose-related manner, the diets also increased the level of anti-inflammatory cytokine IL-10 compared to the B[a]P group. At 6 weeks after the second dose of B[a]P, the cytokine levels in the serum continued to show a decrease in the CG-treated groups. These events are accompanied by an increased level of cleaved caspase-9 product with a molecular weight of 37 kDa. In conclusion, dietary D-glucarate decreases the level of proinflammatory cytokines, increases the level of the anti-inflammatory cytokine IL-10 during early post-initiation stages of B[a]P-induced lung tumorigenesis in A/J mice and affects apoptotic induction.     

Studies of chemopreventive effects of budenoside on benzo[a]pyrene- induced neoplasia of the lung of female A/J mice

The objective of the present investigation was to determine conditions under which the synthetic glucocorticoid, budenoside, will inhibit benzo[a]pyrene (BaP)-induced pulmonary carcinogenesis when administered in the post-initiation period. For this purpose, female A/J mice were employed. The animals were given three administrations of 2 mg of BaP by oral intubation during a 1-week period. Budenoside was fed in the diet subsequent to the last dose of BaP. Using this format, two experiments were carried out to determine the effects of varying the time of administration of budenoside on the magnitude of the inhibition obtained. In both experiments, one group of mice was fed budenoside (1.5 mg/kg of diet) from 1 week after the last dose of BaP until the termination of the experiment, 15 weeks later. The reduction of pulmonary tumor formation under these conditions was 89% in the first experiment and 78% in the second (average 84%). In the first experiment the effects of feeding budenoside only during weeks 1-5 after BaP administration was studied. Under these conditions, inhibition of pulmonary tumor formation was 35%. In the second experiment, the effects of postponing the start of feeding budenoside was determined. In mice in which the budenoside feeding was delayed until 5 weeks after the last dose of BaP and then continued for the duration of the protocol, a 67% inhibition of tumor formation was found. The data obtained indicate that budenoside will produce inhibition of pulmonary adenoma formation when fed either early or late in the post-initiation stage of carcinogenesis, and that feeding throughout the entire post- initiation period gives maximum inhibition.      

Studies of chemopreventive effects of myo-inositol on benzo(a)pyrene-induced neoplasia of the lung and forestomach of female A/J mice

There is a continuing effort at identifying chemopreventiveagents that might be useful in preventing cancer of the lung.In the present study, the effects of myo-inositol and dexamethasoneon benzo[a]pyrene (B[a]P)-induced pulmonary adenoma formationin female A/J mice was investigated. A diet containing 3% myo-inositolfed beginning 1 week after B[a]P administration reduced thenumber of pulmonary adenomas by 40% but did not prevent forestomachtumors, which also occur in this experimental model. Under thesame conditions, dexamethasone, 0.5µg/g diet, inhibitedpulmonary adenoma formation by 57% and also inhibited forestomachtumor formation to a similar extent. Feeding a diet containingboth myo-inositol and dexamethasone resulted in an additiveeffect on the inhibition of pulmonary adenoma formation. Thecombination of myo-inositol plus dexamethasone produced almostidentical inhibition of forestomach tumor formation to thatof dexamethasone alone. The results of the present study arepreliminary, but may provide a basis for future investigationinto strategies for chemoprevention of pulmonary neoplasia.     

Chemoprevention of tobacco smoke-induced lung tumors in A/J strain mice with dietary myo-inositol and dexamethasone.

Male A/J strain mice were fed AIN-76A diet supplemented with myo-inositol/dexamethasone (10 g and 0.5 mg/kg diet) or acetylsalicylic acid (300 mg/kg) and exposed for 5 months to a mixture of sidestream and mainstream cigarette smoke at a concentration of 132 mg total suspended particulates/m3. After tobacco smoke exposure, they were allowed to recover for another 4 months in filtered air. In the animals fed AIN-75A diet alone or acetylsalicylic acid, the average number of tumors/lung was 2.1, whereas in the animals given the myo-inositol/dexamethasone diet, the average lung tumor multiplicity was 1.0 (P < 0.05). In animals exposed to filtered air, lung tumor multiplicities were 0.6 for animals fed AIN-76A or myo-inositol/dexamethasone and 1.2 for animals fed acetylsalicylic acid. It was concluded that the combination of myo-inositol and dexamethasone constitutes an effective chemopreventive regimen against tobacco smoke-induced lung tumorigenesis.     

Effect of dietary green tea extract and aerosolized difluoromethylornithine during lung tumor progression in A/J strain mice

Chemoprevention strategies to prevent the development of lung cancer in at-risk individuals are a key component in disease management. In addition to being highly effective, an ideal chemopreventive agent will require low toxicity as patients are likely to require treatment for several years before their risk of cancer is lowered to background levels. In principle, a combination of safe agents that work through distinct mechanisms will improve efficacy while simultaneously maintaining a favorable safety profile. Here, we describe the use of the decaffeinated green tea extract Polyphenon E (Poly E) (1% in diet) and aerosolized difluoromethylornithine (DFMO) (20 mg/kg/day, 5 days/week) in a mouse lung cancer chemoprevention study using a progression protocol. Female A/J mice were injected with benzo[a]pyrene (B[a]P) at 8 weeks of age and precancerous lesions allowed to form over a period of 21 weeks before chemoprevention treatment for an additional 25 weeks. Poly E treatment did not significantly inhibit average tumor multiplicity but reduced per animal tumor load. Analysis of tumor pathology revealed a specific inhibition of carcinomas, with the largest carcinomas significantly decreased in Poly E-treated animals. Aerosolized DFMO did not have a significant effect on lung tumor progression. Magnetic resonance imaging of B[a]P-induced lung tumors confirmed the presence of a subset of large, rapidly growing tumors in untreated mice. Our results suggest a potential role for green tea extracts in preventing the progression of large, aggressive lung adenocarcinomas.     

Protection against N-nitrosodiethylamine and benzo[a]pyrene-induced forestomach and lung tumorigenesis in A/J mice by green tea

In recent years we and others have shown the cancer chemopreventiveeffects of green tea in several animal tumor models. In thisstudy we assessed the cancer chemopreventive effects of waterextract of green tea (WEGT) and the polyphenolic fraction (GTP)isolated from WEGT against N-nitrosodiethylamine (DEN)- andbenzo[a]pyrene (BP)-induced forestomach and lung tumorigenesisin A/J mice. The protective effects, both in forestomach andlungs, were evident by a decrease in number of tumors and thepercentage of mice with tumors when WEGT and GTP were fed toanimals during initiation, post-initiation and entire periodof tumorigenesis protocols. Oral feeding of 0.2% GTP in drinkingwater to mice afforded 68–82 and 39–66% protectionagainst DEN- and BP-induced forestomach tumorigenesis respectively.In case of pulmonary tumor multiplicity caused by DEN and BP,the protective effects of GTP were between 38–43 and 25–46%respectively. Similarly, oral feeding of 2.5% WEGT to mice alsoafforded 80–85 and 61–71% protection against DEN-and BP-induced forestomach tumorigenesis respectively. In caseof lung tumorigenesis, the protective effects of WEGT were 43–62and 25–51% respectively. Histological studies of forestomachtumors showed significantly lower squamous cell carcinoma countsin GTP- and WEGT-fed groups of mice compared to carcinogen alonetreated control group of mice. When pulmonary tumors were examinedhistologically, no adenocarcinomas were observed in GTP-andWEGT-fed groups of mice compared to 20% mice with adenocarcinomasin carcinogen alone treated control group. Oral feeding of GTPand WEGT in drinking water also showed significant enhancementin the activities of glutathione S-transferase and NADP(H):quinone reductase in liver, small bowel, stomach and lung. Theresults of this study suggest that green tea possesses chemopreventiveeffects against carcinogen-induced tumorigenesis in internalbody organs, and that the mechanism of such effects may involvethe enhancement of phase II and anti-oxidant enzyme systems.     

Tobacco smoke-induced lung tumorigenesis in mutant A/J mice with alterations in K-ras, p53, or Ink4a/Arf

A/J mice with genetic alterations in K-ras, p53, or Ink4a/Arf were employed to investigate whether mice carrying these germline mutations would be susceptible to tobacco smoke-induced lung tumorigenesis. Transgenic mice of both genders and their wild-type littermates were exposed to environmental cigarette smoke for 6 months, followed by recovery in air for 5 months. A significant increase of lung tumor multiplicity was observed in K-ras, p53, or Ink4a/Arf mutant mice when compared with wild-type mice. Furthermore, an additive effect was observed between the mice with a mutant p53 transgene and an Ink4A/Arf deletion during tobacco smoke-induced lung tumorigenesis. Sequence analysis of the K-ras gene indicated that the mutations had occurred at either codon 12/13 or 61 in both spontaneously occurring (air control) and tobacco smoke-induced lung tumors. K-ras mutations were found in 62% of the tumors from air-control animals and 83% in those exposed to tobacco smoke. The mutation spectrum found in tumors from mice exposed to tobacco smoke is somewhat similar to that in tumors from air-control mice. In addition, we identified three novel mutations at codon 12: GGT (Gly) --> TTT (Phe), ATT (Ile), and CTT (Leu). These findings provide evidence that K-ras, p53, and Ink4a/Arf mutations play a role in tobacco smoke-related lung carcinogenesis. The similarity of the mutation spectra in the K-ras oncogene observed in tobacco smoke-induced tumors, as compared to spontaneous tumors, suggests that tobacco smoke enhances lung tumorigenesis primarily through promoting spontaneously occurring K-ras mutations.     

Inhibitory effects of propolis granular A P C on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in A/J mice

We examined the effect of propolis granular A. P. C on lung tumorigenesis in female A/J mice. Lung tumors were induced by the tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) administered in drinking water for 7 weeks in mice maintained on an AIN-76A semi-synthetic diet. Propolis granular A. P. C (100 mg/kg body wt.) was administered orally daily for 6 days/week from 1 week before NNK administration and throughout the experiment. Sixteen weeks after the NNK treatment, the mice were killed and the number of surface lung tumors was measured. The number of lung tumors in mice treated with NNK alone for 7 weeks (9.4 mg/mouse) was significantly more than in that observed in control mice. Propolis granular A. P. C significantly decreased the number of lung tumors induced by NNK. These results indicate that propolis granular A. P. C is effective in suppressing NNK-induced lung tumorigenesis in mice.     

Dose-response effects of dietary fiber on NMU-induced mammary tumorigenesis, estrogen levels and estrogen excretion in female rats

The publisher wishes to apologise for the inclusion of a duplicateTable IX, and for the omission of Table VIII on page 50 of theabove mentioned paper. The correct Table is shown below. Thetitle of Table V was also incorrect and should have read serumestrogen concentrations^a,b