Achaete-scute complex homolog-1 promotes DNA repair in the lung carcinogenesis through matrix metalloproteinase-7 and O(6)-methylguanine-DNA methyltransferase

Lung cancer is the leading cause of cancer-related deaths in the world. Achaete-scute complex homolog-1 (Ascl1) is a member of the basic helix-loop-helix (bHLH) transcription factor family that has multiple functions in the normal and neoplastic lung such as the regulation of neuroendocrine differentiation, prevention of apoptosis and promotion of tumor-initiating cells. We now show that Ascl1 directly regulates matrix metalloproteinase-7 (MMP-7) and O(6)-methylguanine-DNA methyltransferase (MGMT). Loss- and gain-of-function experiments in human bronchial epithelial and lung carcinoma cell lines revealed that Ascl1, MMP-7 and MGMT are able to protect cells from the tobacco-specific nitrosamine NNK-induced DNA damage and the alkylating agent cisplatin-induced apoptosis. We also examined the role of Ascl1 in NNK-induced lung tumorigenesis in vivo. Using transgenic mice which constitutively expressed human Ascl1 in airway lining cells, we found that there was a delay in lung tumorigenesis. We conclude that Ascl1 potentially enhances DNA repair through activation of MMP-7 and MGMT which may impact lung carcinogenesis and chemoresistance. The study has uncovered a novel and unexpected function of Ascl1 which will contribute to better understanding of lung carcinogenesis and the broad implications of transcription factors in tobacco-related carcinogenesis.

Ingestion of proteoglycan fraction from shark cartilage increases serum inhibitory activity against matrix metalloproteinase-9 and suppresses development of N-nitrosobis(2-oxopropyl)amine-induced pancreatic duct carcinogenesis in hamster

A water extract of shark cartilage was fractionated into acidic and basic fractions by preparative isoelectric focusing on the basis of the amphoteric nature of samples. The acidic fraction was further fractionated into ethanol-soluble and -precipitate fractions. After the carcinogenesis treatment using N-nitrosobis(2-oxopropyl)amine, hamsters received a diet containing each fraction or purified chondroichin sulfate to give 0.4% (w/w) for 50 days. Only administration of the acidic ethanol-precipitate-fraction-containing diet significantly increased serum inhibitory activity against matrix metalloproteinase (MMP)-9 and reduced the number of adenocarcinomas in the pancreatic duct. The active fraction predominantly consisted of chondroichin sulfate-containing proteoglycan. However, the purified chondroichin sulfate had no significant activity. These results suggest that the protein moiety of the proteoglycan might be involved in the increase of serum inhibitory activity against MMP-9 and suppression of pancreatic carcinogenesis in hamster.

Enhanced inhibition of lung adenocarcinoma by combinatorial treatment with indole-3-carbinol and silibinin in A/J mice

In earlier studies, we demonstrated the efficacy of indole-3-carbinol (I3C) against lung adenocarcinoma in A/J mice. However, these effects were accompanied by reductions in body weight gain. We therefore assessed if combinations of low doses of I3C with silibinin could inhibit lung tumorigenesis without causing undesirable side effects. In in vitro assays with A549 and H460 lung cancer cells, exposure of the cells to a mixture of low concentrations of I3C (50 μM) plus silibinin (50 μM) for 72 h caused inhibition of cell growth and extracellular signal-regulated kinase (ERK) and Akt activation and induction of apoptosis, whereas the individual agents did not have any effect. In mice pretreated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and given I3C (10 μmol/g diet) plus silibinin (7 μmol/g diet), multiplicities of tumors on the surface of the lung and adenocarcinoma were reduced by 60 and 95%, respectively. The individual effects of I3C and silibinin were relatively weaker: 43 and 36% reductions, respectively, in the multiplicity of tumors on the surface of the lung and 83 and 50% reductions, respectively, in the number of adenocarcinoma. Also, the expression of phospho-Akt, phospho-ERK and cyclin D1 and poly (ADP-ribose) polymerase cleavage were strongly modulated by I3C plus silibinin than by I3C or silibinin alone, suggesting that the chemopreventive activities of the mixture could be mediated, at least partly, via modulation of the level of these proteins. Taken together, our findings showed that mixtures of I3C and silibinin are more potent than the individual compounds for the chemoprevention of lung cancer in A/J mice.

Metformin prevents tobacco carcinogen--induced lung tumorigenesis

Activation of the mammalian target of rapamycin (mTOR) pathway is an important and early event in tobacco carcinogen-induced lung tumorigenesis, and therapies that target mTOR could be effective in the prevention or treatment of lung cancer. The biguanide metformin, which is widely prescribed for the treatment of type II diabetes, might be a good candidate for lung cancer chemoprevention because it activates AMP-activated protein kinase (AMPK), which can inhibit the mTOR pathway. To test this, A/J mice were treated with oral metformin after exposure to the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Metformin reduced lung tumor burden by up to 53% at steady-state plasma concentrations that are achievable in humans. mTOR was inhibited in lung tumors but only modestly. To test whether intraperitoneal administration of metformin might improve mTOR inhibition, we injected mice and assessed biomarkers in liver and lung tissues. Plasma levels of metformin were significantly higher after injection than oral administration. In liver tissue, metformin activated AMPK and inhibited mTOR. In lung tissue, metformin did not activate AMPK but inhibited phosphorylation of insulin-like growth factor-I receptor/insulin receptor (IGF-1R/IR), Akt, extracellular signal-regulated kinase (ERK), and mTOR. This suggested that metformin indirectly inhibited mTOR in lung tissue by decreasing activation of insulin-like growth factor-I receptor/insulin receptor and Akt upstream of mTOR. Based on these data, we repeated the NNK-induced lung tumorigenesis study using intraperitoneal administration of metformin. Metformin decreased tumor burden by 72%, which correlated with decreased cellular proliferation and marked inhibition of mTOR in tumors. These studies show that metformin prevents tobacco carcinogen-induced lung tumorigenesis and support clinical testing of metformin as a chemopreventive agent.

Acceleration of N-nitrosation reactions by electrophiles

Selected mechanisms by which electrophiles can facilitate N-nitrosamine formation are reviewed. Special attention is given to a recently discovered reaction in which nitrogen in its lowest (ammonia) oxidation state is efficiently converted to N-nitroso compounds by oxidation in the presence of secondary amines; an electrophilic transition metal centre (E+) makes this reaction possible by initially N-coordinating the ammonia (E+ + NH3----E-NH3+). Other mechanisms considered include: the conversion of nitrite under nonacidic conditions via nitro complexes to nitrosatively active transition metal nitrosyl intermediates (E+ + NO(2-)----E-NO(2-)----E-NO2+); catalysis of N-nitrosamine formation in nitrite-amine mixtures by electrophilic carbon centres that initiate the reaction by attack on the amine (E+ + R2NH----E-NR2); and coordination of nitrite by carbon electrophiles to form activated O-bound species (E+ + ONO(-)----E-O-NO) capable of performing the required N-nitrosation. The findings suggest that acceleration of N-nitrosamine-forming reactions by electrophiles may be a critical factor to consider in attempting to rationalize, predict and control the distribution of carcinogenic N-nitroso compounds in vivo and in the environment.

Bronchogenic and alveologenic tumors in mice induced by N-nitrosopiperidine

The aim of this study was to explore the histogenesis and carcinogenesis of pulmonary cancer induced by N-nitrosopiperidine (NPIP) in mice. NPIP is a form of N-nitrosamine found in tobacco smoke, which has been shown to be a genotoxic chemical as well as a mutagenic compound for inducing chromosome aberrations and severe clastogenicity. In this study, 80 BALB/C strain mice were injected with 0.2 mmol/kg NPIP intraperitoneally for 8 weeks, and experiments were conducted for a further 16 weeks. For the control group, 40 mice were injected with an equal volume of 0.9% NaCl. Pulmonary tissues and tumors in the NPIP-treated group were examined by light microscopy and transmission electron microscopy and compared with the control group at 4-week intervals. The mRNA levels of p53 (mutant), bcl-2, c-myc, ras, and subunits of telomerase - telomerase reverse transcriptase (TERT) and an RNA component, TR - were assayed by mPCR or RT-PCR. Twenty-two mice in the experimental group were found to develop pulmonary tumors, but none in the control group. All tumors found in the experimental group originated from alveolar type II epithelial cells. In addition, 6 of the 22 mice also developed tumors of bronchogenic origin. The expression of p53, bcl-2, c-myc, ras, and the subunits of telomerase were found to increase in all pulmonary tissues and tumors formed thereafter upon NPIP treatment. In summary, NPIP-induced mouse lung tumors exhibited morphological changes during carcinogenesis, which may be the consequence of overexpression of some genes associated with the development of carcinoma and changes in subunits of telomerase. This mouse model of lung tumor formation may be a useful tool to delineate the histogenesis and carcinogenesis of human pulmonary cancer.

Mutations of LKB1 gene in pancreatic ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters

To evaluate an involvement of LKB1 gene alteration during pancreatic carcinogenesis, mutations in the LKB1 gene in hamster pancreatic duct adenocarcinomas (PDAs) induced by N-nitrosobis(2-oxopropyl)amine (BOP) were investigated. Female Syrian golden hamsters received 30 mg/kg of BOP followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine then L-methionine and a further administration of 20 mg/kg BOP. A total of 10 PDAs obtained 10 weeks after beginning the experiment were examined for mutations using reverse transcription (RT)-polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) analysis. Mutations were detected in 3 out of the 10 PDAs (30.0%). Sequence analysis revealed the identity of these mutations to be a CCC to CCT (Pro to Pro) transition at codon 221, a CCG to CAG (Pro to Gln) transversion at codon 324 and a GAC to GGC (Asp to Gly) transition at codon 343. The LKB1 gene may be involved in the development of PDAs induced by BOP in hamsters.

Effects of curcumin on N-bis(2-hydroxypropyl) nitrosamine (DHPN)-induced lung and liver tumorigenesis in BALB/c mice in vivo

Curcumin (diferuloylmethane), a phenolic compound from the plant Curcuma longa (Linn.) has been shown to exhibit antitumor activity and apoptosis in many human cancer cell lines including that of lung and liver cancer. In this study, curcumin was evaluated in BALB/c mice for its ability to inhibit pulmonary and liver adenoma formation and growth after they were orally treated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Animals were treated with DHPN in water for approximately 14 days before multiple doses of curcumin were given intraperitoneally. It was found that 200 microM curcumin reduced lung and liver tumor multiplicity by 37% (p<0.05) and 30% (p<0.05) respectively. The results indicated that curcumin significantly inhibited pulmonary and liver adenoma formation and growth in BALB/c mice. The precise mechanism by which curcumin inhibits lung and liver tumorigenesis remains to be elucidated. Thus, curcumin appears to be a promising new chemotherapeutic and preventive agent for lung and liver cancer induced by DHPN.

Cytokinesis-blocked micronucleus cytome assay biomarkers identify lung cancer cases amongst smokers

The multi-endpoint cytokinesis-blocked micronucleus assay is used for assessing chromosome aberrations. We have recently reported that this assay is extremely sensitive to genetic damage caused by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and that the binucleated cells with micronuclei, nucleoplasmic bridges, and nuclear buds in lymphocytes (chromosome damage endpoints measured by the assay) are strong predictors of lung cancer risk. In the current study, we refined our analysis to include toxicity endpoints (micronuclei in mononucleated cells, apoptosis, necrosis, and nuclear division index) to investigate the benefit of including these variables on improving the predictive value of the assay. Baseline and NNK-induced micronuclei in mononucleated cells were significantly higher in patients (n = 139) than controls (n = 130; P < 0.001). Baseline apoptosis was higher among cases; however, the controls showed a significant higher fold increase in NNK-induced apoptosis compared with baseline (P < 0.001). Principal components analysis was used to derive a summary measure for all endpoints and calculate the positive predictive value (PPV) and negative predictive value (NPV) for disease status. First principal component for NNK-induced chromosome damage endpoints (binucleated cells with micronuclei, nucleoplasmic bridges, and nuclear buds) had an area under the curve = 97.9 (95% confidence interval, 95.9-99.0), PPV = 94.8, and NPV = 92.6. The discriminatory power improved when micronuclei in mononucleated cells were included: area under the curve = 99.1 (95% confidence interval, 97.9-100.0), PPV = 98.7 and NPV = 95.6. The simplicity, rapidity, and sensitivity of the assay together with potential for automation make it a valuable tool for screening and prioritizing potential cases for intensive screening.

Hypermethylation of the Dal-1 gene in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

DAL-1 (differentially expressed in adenocarcinoma of the lung) is an actin-binding protein that has been shown to suppress growth in lung cancer cells. Recently, inactivation of the gene encoding DAL-1 due to hypermethylation has been found in several human malignancies, including lung cancers. To assess the involvement of the Dal-1 gene in rat lung carcinogenesis, we investigated the expression of Dal1 and its methylation status in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). Six-week old male Wistar rats (n = 11) were given 2,000 ppm BHP in their drinking water for 12 wk and maintained without further treatment until they were sacrificed at 25 wk. Total RNA was extracted from 11 lung adenocarcinomas, one from each BHP treated rat, and Dal-1 gene expression was analyzed using real-time quantitative reverse transcription-polymerase chain reaction. Dal-1 expression was significantly reduced in the lung adenocarcinomas compared with three normal lung tissues (P < 0.05). For methylation analysis, bisulfite sequencing was performed using normal lung tissue and tissue from 4 tumors, all of which showed reduced expression of Dal-1. The 5' upstream region was highly methylated in all four adenocarcinomas, whereas this region was unmethylated in normal lung tissue. These results suggest that aberrant methylation of the Dal-1 gene might be involved in the development of lung adenocarcinomas induced in rats by BHP.

Determination of the role of target tissue metabolism in lung carcinogenesis using conditional cytochrome P450 reductase-null mice

Critical to mechanisms of chemical carcinogenesis and the design of chemopreventive strategies is whether procarcinogen bioactivation in an extrahepatic target tissue (e.g., the lung) is essential for tumor formation. This study aims to develop a mouse model capable of revealing the role of pulmonary microsomal cytochrome P450 (P450)-mediated metabolic activation in xenobiotic-induced lung cancer. A novel triple transgenic mouse model, with the NADPH-P450 reductase (Cpr) gene deleted in a lung-specific and doxycycline-inducible fashion (lung-Cpr-null), was generated. CPR, the obligate electron donor for microsomal P450 enzymes, is essential for the bioactivation of many procarcinogens. The lung-Cpr-null mouse was studied to resolve whether pulmonary P450 plays a major role in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung cancer by producing carcinogenic metabolites in the target tissue. A liver-Cpr-null mouse was also studied to test whether hepatic P450 contributes predominantly to systemic clearance of NNK, thereby decreasing NNK-induced lung cancer. The numbers of NNK-induced lung tumors were reduced in the lung-Cpr-null mice but were increased in the liver-Cpr-null mice, relative to wild-type control mice. Decreased lung tumor multiplicity in the lung-Cpr-null mice correlated with reduced lung O6-methylguanine adduct levels, without decreases in NNK bioavailability, consistent with decreased NNK bioactivation in the lung. Moreover, lung tumors in lung-Cpr-null mice were positive for CPR expression, indicating that the tumors did not originate from Cpr-null cells. Thus, we have confirmed the essential role of pulmonary P450-mediated metabolic activation in NNK-induced lung cancer, and our mouse models should be applicable to studies on other procarcinogens that require P450-mediated metabolic activation.

Nongenomic beta estrogen receptors enhance beta1 adrenergic signaling induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in human small airway epithelial cells

Women are at higher risk for the development of lung adenocarcinoma than men; however, the mechanisms responsible for this are poorly understood. In lung adenocarcinoma cells, the estrogen receptor beta (ERbeta) is the predominating form. We found that 17beta-estradiol enhanced proliferation of the putative cells of origin of lung adenocarcinoma, small airway epithelial cells (HPLD1), in response to the nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Reverse-phase protein microarrays combined with Western blotting revealed that NNK induced phosphorylation of ERbeta, an effect that involved stimulation of the adrenergic receptors beta1 (beta1AR). In transiently transfected cells, beta1AR coprecipitated with ERbeta, which increased with NNK treatment. ERbeta enhanced NNK-induced cyclic AMP accumulation as well as Galphai-mediated mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) 1/2 activation. Coexpression of beta1AR and ERbeta activated NNK-mediated ERK1/2 cooperatively. ERbeta gene knockdown, as well as coexpression of the dominant negative Ras and Raf, reduced stimulation of ERK1/2 by NNK. Whereas NNK phosphorylated Akt at Thr(308) and Ser(473), ERbeta had no effect on this activity. Luciferase reporter assays showed that, in response to NNK, ERbeta stimulated transcription of serum responsive element (SRE) but had a very small effect on the activity of estrogen responsive element (ERE). Together, the phosphorylation of ERbeta, the dependence on Galphai proteins, the activation of ERK1/2, and the preferential targeting of SRE over the classic ERE pathway support a role for nongenomic ERbeta in the development of smoking-associated lung cancer. This novel cooperation between beta1AR and ERbeta signaling may contribute to the prominence of lung adenocarcinoma in women.

Involvement of mutation-based inhibition of beta-catenin phosphorylation at Ser33 in the malignant progression of lung (pre)neoplastic lesions induced by N-nitrosobis(2-hydroxypropyl)amine in male Fischer 344 rats

In this study we investigated the Ser33 phosphorylation status of beta-catenin protein in relation to genomic mutations in lung (pre)neoplastic lesions induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in male Fischer 344 rats. Six-week-old animals received 2000 ppm of BHP in the drinking water for 8 weeks and were sacrificed 12 weeks thereafter. Histopathologically, 69 of 75 rats demonstrated multiple lung (pre)neoplastic lesions, classified into 27 slight and 33 advanced hyperplasias (preneoplasms) and 61 neoplasms, including adenomas, adenocarcinomas, and adenosquamous carcinomas. Nucleotide mutation analysis of the beta-catenin gene detected a total of 33 mutations in 12 assessed lung (pre)neoplastic lesions. The mutations tended to accumulate in positions near the phosphorylation region of the gene, between codons 33 and 45. Immunohistochemical analysis showed beta-catenin protein expression to be increased and its localization changed from the cell membrane to the cytoplasm and finally the nuclei with advancing malignancy of the lung lesions. In contrast, the expression of phosphorlyated beta-catenin protein at Ser33 was weakened in lung (pre)neoplastic lesions compared to normal lung tissues. These results suggest that BHP-induced mutation of the beta-catenin gene results in amino acid conversions in its product protein, which in turn lead to inhibition of phosphorylation of the protein and escape from protein degradation. These phenomena might contribute to the malignant progression of the lung (pre)neoplastic lesions, which start from the relatively early stage in lung carcinogenesis.

Suppression of N-nitrosobis(2-oxopropyl)amine-induced pancreatic carcinogenesis in hamsters by pioglitazone, a ligand of peroxisome proliferator-activated receptor γ

Fat intake and obesity are positively correlated with pancreatic cancer in humans. N-nitrosobis(2-oxopropyl)amine (BOP) induces pancreatic ductal adenocarcinomas limited to Syrian golden hamsters, other rodents not being susceptible. In the present study, we found markedly high levels of serum triglycerides (TGs) and total cholesterol (TC) in Syrian golden hamsters, but not C57BL/6 mice, ICR mice, F344 rats and Wistar rats. Consistent with this, lipoprotein lipase (LPL) activities in the liver were lower in hamsters compared with mice and rats. To examine effects of pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, on LPL expression, serum lipid levels and pancreatic cancer development, 6-week-old female Syrian golden hamsters were subcutaneously injected with BOP (10 mg/kg body wt) four times in a week and thereafter fed a diet containing 800 p.p.m. pioglitazone for 22 weeks. The treatment elevated LPL mRNA expression in the liver and significantly improved hyperlipidemia with serum levels of TG and TC being decreased to 62 and 71%, respectively, of the control values. Concurrently, the incidence and multiplicity of pancreatic ductal adenocarcinomas were significantly decreased by pioglitazone in comparison with the controls (38 versus 80%, P < 0.01 and 0.55 +/- 0.15 versus 1.37 +/- 0.22, P < 0.01, respectively). The suppression rates were greater in invasive adenocarcinomas than non-invasive ones. The incidence of cholangiocellular carcinomas was also reduced. Thus, suppression of pancreatic adenocarcinoma development by pioglitazone is possibly associated with improvement in the serum lipid profile, and hyperlipidemia could be an enhancing factor for development of pancreatic cancer in hamsters.

Apo-10'-lycopenoic acid inhibits lung cancer cell growth in vitro, and suppresses lung tumorigenesis in the A/J mouse model in vivo

High intake of lycopene has been associated with a lower risk of a variety of cancers including lung cancer. We recently showed that lycopene can be converted to apo-10'-lycopenoids [Hu et al. (2006). J. Biol. Chem., 281, 19327-19338] in mammalian tissues both in vitro and in vivo, raising the question of whether apo-10'-lycopenoids have biological activities against lung carcinogenesis. In the present study, we report that apo-10'-lycopenoic acid inhibited the growth of NHBE normal human bronchial epithelial cells, BEAS-2B-immortalized normal bronchial epithelial cells and A549 non-small cell lung cancer cells. This inhibitory effect of apo-10'-lycopenoic acid was associated with decreased cyclin E, inhibition of cell cycle progression from G(1) to S phase and increased cell cycle regulators p21 and p27 protein levels. In addition, apo-10'-lycopenoic acid transactivated the retinoic acid receptor beta (RARbeta) promoter and induced the expression of RARbeta. We further examined the effect of apo-10'-lycopenoic acid treatment on 4-(N-methyl-N-nitrosamino)-1-(3-pyridal)-1-butanone (NNK)-induced lung tumorigenesis in the A/J mouse model. We found that the lung tumor multiplicity was decreased dose dependently from an average of 16 tumors per mouse in the NNK injection alone group, to an average of 10, 7 and 5 tumors per mouse in groups injected with NNK and supplemented with 10, 40 and 120 mg/kg diet of apo-10'-lycopenoic acid, respectively. These observations demonstrate that apo-10'-lycopenoic acid is a biological active metabolite of lycopene and suggest that apo-10'-lycopenoic acid is a potential chemopreventive agent against lung tumorigenesis.

4-(Methylnitrosamino)-I-(3-Pyridyl)-1-Butanone Enhances the Expression of Apolipoprotein A-I and Clara Cell 17-kDa Protein in the Lung Proteomes of Rats Fed a Corn Oil Diet but not a Fish Oil Diet

The nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the most potent lung carcinogens in rodents. Several epidemiologic studies indicated that the development of lung cancer in smokers is influenced by the type and amount of dietary polyunsaturated fatty acids. A high corn oil diet has been shown to increase lung tumor volume and to decrease tumor latency in rats treated with NNK. In this study, we investigated the effects of dietary polyunsaturated fatty acids in the form of corn oil or fish oil on lung proteomes in F344 rats treated with or without NNK. The fish oil diet contained 17% fish oil and 3% corn oil, and the corn oil diet contained 20% corn oil. Rats were sacrificed after 3 months, and lungs were excised. Whole lung tissue proteins were separated by two-dimensional liquid chromatography, and differentially expressed proteins were identified by trypsin digestion and tandem mass spectrometry. Apolipoprotein A-I and Clara cell 17-kDa protein were overexpressed in the lungs of rats fed corn oil diet, compared with fish oil diet. NNK further enhanced their expression in rats fed corn oil diet; this effect was not observed in animals fed fish oil diet. The results suggest that the elevated levels of apolipoprotein A-I and Clara cell 17-kDa protein may be involved in the development of NNK-induced lung cancer in rats fed a high corn oil diet. Therefore, we propose that both proteins may serve as potential biomarkers in future molecular epidemiologic and clinical chemoprevention intervention studies.

Duodenal Reflux Leads to Down Regulation of DNA Mismatch Repair Pathway in an Animal Model of Esophageal Cancer

BACKGROUND

Gastroduodenal reflux is implicated in esophageal carcinogenesis. This effect is mediated by reactive oxygen species. We hypothesized that this is mediated by DNA mismatch lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG), which is repaired by the Mut Y homologue (MYH). We tested the effect of reflux, either alone or in combination with the human dietary mutagen methyl-n-amyl nitrosamine (MNAN), on DNA damage in adenocarcinoma and squamous cell cancer of the esophagus in a rat model.

METHODS

Reflux was promoted in male Sprague-Dawley rats by duodenoesophageal anastomosis (8 weeks) without gastric bypass. MNAN treatment (25 mg/kg per week intraperitoneally for four doses) commenced at 10 weeks age. Ten animals served as controls. Quantification of 8-oxoG was performed by using immunohistochemistry, and MYH was analyzed by Western blot. Apoptosis was assessed by terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling (TUNEL), cytochrome C, and caspase.

RESULTS

Tumors (adenocarcinoma) developed in 15 (50%) of 30 animals with reflux alone; this increased to 26 (86.6%) of 30 when reflux was combined with MNAN treatment, with tumor histology consistent with adenosquamous and squamous cell cancer. DNA damage, as reflected by positive 8-oxoG staining in reflux groups, was significantly increased compared with control (p < 0.01), and this was maximal in tissues with malignant transformation. Protein levels of the DNA repair enzyme MYH were significantly less in tissues subjected to reflux compared with controls (p < 0.05). TUNEL, cytochrome C, and caspase positivity confirmed increased apoptosis in cancer lesions.

CONCLUSIONS

Gastroduodenal reflux leads to increased DNA damage and downregulation of the DNA mismatch repair pathway. This pathway has an important role in esophageal carcinogenesis in rats.

Selective decrease in the DNA base excision repair pathway in squamous cell cancer of the esophagus

OBJECTIVES

Oxidative damage can lead to a highly mutagenic 8-oxoguanine lesion, which mispairs with adenosine residues, leading to G:C-->T:A transversions. In mammalian cells 8-oxoguanine glycosylase initiates the DNA base excision repair pathway to repair the 8-oxoguanine lesion. To date, there is no information regarding oxidative DNA damage and repair pathways in esophageal cancer. Therefore we designed the current study to demonstrate the DNA damage and repair pathways in esophageal cancer by expression of 8-oxoguanine glycosylase in reflux-induced and mutagen (methyl-n-amyl nitrosamine)-induced DNA damage and apoptosis in esophageal tumors.

METHODS

Gastroduodenal reflux was surgically created in male Sprague Dawley rats (n = 120). Half of the animals received methyl-n-amyl nitrosamine. Animals not undergoing operations served as control animals (n = 10). The experiment concluded 30 weeks postoperatively. Immunohistochemistry for 8-oxoguanine and 8-oxoguanine glycosylase was assessed by 2 independent observers. Protein expression was assessed by using the Western blot method.

RESULTS

There was significantly more DNA damage in both adenocarcinoma (n = 15) and squamous cell carcinoma (n = 19), as exemplified by positive 8-oxoguanine expression compared with that seen in control animals (P < .05). 8-Oxoguanine glycosylase was several folds upregulated in adenocarcinoma (P < .05), but there was significantly decreased expression in squamous cell carcinoma (P < .01). The apoptosis was assessed as caspase-dependent and caspase-independent pathways, and both were active and correlated well with 8-oxoguanine expression.

CONCLUSION

These results demonstrate the selective decrease in the DNA base excision repair pathway in combined reflux and methyl-n-amyl nitrosamine-induced squamous cell cancer of the esophagus.

Hepatic progenitor cells, stem cells, and AFP expression in models of liver injury

Adult hepatocytes and liver-cell progenitors play a role in restoring liver tissue after injury. For the study of progenitor cells in liver repair, experimental models included (a) surgical removal of liver tissue by partial hepatectomy; (b) acute injury by carbontetrachloride; (c) acute injury by d-galactosamine (GalN) and N-nitrosomorpholine (NNM); and (d) chemical hepatocarcinogenesis by feeding NNM in low and high doses. Serological and immunohistological detection of alpha-fetoprotein gene expression served to follow pathways of cellular differentiation. Stem cells were not required in models of surgical removal of parenchyma and in carbon tetrachloride intoxication of adult hepatocytes. In contrast, regeneration of liver occurred through biliary epithelial cells in injuries induced by GalN and NNM. These biliary epithelial cells, collectively called oval cells, are most probably derived from the canals of Hering. Proliferating bile duct cells reached a level of differentiation with reactivation of foetal genes and significant alpha-1-fetoprotein (AFP) synthesis signalling a certain degree of retrodifferentiation with potential stemness. Due to the same embryonic origin of bile ducts and hepatocytes, biliary epithelium and its proliferating progeny (oval cells) have a defined role in liver regeneration as a transit and amplification compartment. In their early proliferation stage, oval cells were heavily engaged in DNA synthesis ([3H]thymidine labelling). Pulse-chase experiments during experimental hepatocarcinogenesis exhibited their development into hepatocytes with high risk for transformation and leading to foci of altered hepatocytes. Hepatocellular carcinomas may arise either from proliferating/differentiating oval cells or from adult hepatocytes; both cell types have stem-like properties. AFP-positive and AFP-negative carcinomas occurred in the same liver. They may represent random clonal origin. The heterogeneity of phenotypic marker (AFP) correlated with a process of retrodifferentiation.

Translesion synthesis across O6-alkylguanine DNA adducts by recombinant human DNA polymerases

Previous studies have shown that replicative bacterial and viral DNA polymerases are able to bypass the mutagenic lesions O(6)-methyl and -benzyl (Bz) G. Recombinant human polymerase (pol) delta also copied past these two lesions but was totally blocked by O(6)-[4-oxo-4-(3-pyridyl)butyl] (Pob)G, an important mutagenic lesion formed following metabolic activation of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. The human translesion pols iota and kappa produced mainly only 1-base incorporation opposite O(6)-MeG and O(6)-BzG and had very low activity in copying O(6)-PobG. Human pol eta copied past all three adducts. Steady-state kinetic analysis showed similar efficiencies of insertion opposite the O(6)-alkylG adducts for dCTP and dTTP with pol eta and kappa; pol iota showed a strong preference for dTTP. pol eta, iota, and kappa showed pre-steady-state kinetic bursts for dCTP incorporation opposite G and O(6)-MeG but little, if any, for O(6)-BzG or O(6)-PobG. Analysis of the pol eta O(6)-PobG products indicated that the insertion of G was opposite the base (C) 5' of the adduct, but this product was not extended. Mass spectrometry analysis of all of the pol eta primer extension products indicated multiple components, mainly with C or T inserted opposite O(6)-alkylG but with no deletions in the cases of O(6)-MeG and O(6)-PobG. With pol eta and O(6)-BzG, products were also obtained with -1 and -2 deletions and also with A inserted (opposite O(6)-BzG). The results with pol eta may be relevant to some mutations previously reported with O(6)-alkylG adducts in mammalian cells.

Protective effects of isothiocyanates towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay

The aim of this study was to investigate the protective effect of isothiocyanates towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay. None of the isothiocyanates (ITCs) concentrations tested in the presence or absence of formamidopyrimidine-DNA glycosylase (Fpg) caused DNA damage per se. Combined treatments of HepG2 cells with phenethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC) or indol-3-carbinol (I3C) and N-nitrosopyrrolidine (NPYR) or N-nitrosodimethylamine (NDMA) reduced the genotoxic effects of the N-nitrosamines in a dose-dependent manner. The protective effect of the three ITCs tested was higher towards NPYR-induced oxidative DNA damage than against NDMA. The greatest protective effect towards NPYR-induced oxidative DNA damage was shown by I3C (1 microM, 79%) and by PEITC (1 microM, 67%) and I3C (1 microM, 61%) towards NDMA (in presence of Fpg enzyme). However, in absence of Fpg enzyme, AITC (1 microM, 72%) exerted the most drastic reduction towards NPYR-induced oxidative DNA damage, and PEITC (1 microM, 55%) towards NDMA. Our results indicate that ITCs protect human-derived cells against the DNA damaging effect of NPYR and NDMA, two carcinogenic compounds that occur in the environment.

Cytokinesis-blocked micronucleus assay as a novel biomarker for lung cancer risk

In this case-control study, we modified the cytokinesis-block micronucleus (CBMN) assay, an established biomarker for genomic instability, to evaluate susceptibility to the nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by measuring the frequency of NNK-induced chromosomal damage endpoints (micronuclei, nucleoplasmic bridges, and nuclear buds) per 1,000 binucleated lymphocytes. Spontaneous and NNK-induced chromosomal damage were significantly higher in lung cancer patients compared with controls. Forty-seven percent of cases (versus 12% of controls) had >or=4 spontaneous micronuclei, 66% of cases (and no controls) had >or=4 spontaneous nucleoplasmic bridges, and 25% of cases (versus 5% of controls) had >or=1 spontaneous nuclear bud (P < 0.001). Similarly, 40% of cases (versus 6% of the controls) had >or=5 NNK-induced micronuclei, 89% of cases (and no controls) had >or=6 induced nucleoplasmic bridges, and 23% of cases (versus 2% of controls) had >or=2 induced nuclear buds (P < 0.001). When analyzed on a continuous scale, spontaneous micronuclei, nucleoplasmic bridges, and nuclear buds were associated with 2-, 29-, and 6-fold increases in cancer risk, respectively. Similarly, NNK-induced risks were 2.3-, 45.5-, and 10-fold, respectively. We evaluated the use of CBMN assay to predict cancer risk based on the numbers of micronuclei, nucleoplasmic bridges, and nuclear buds defined by percentile cut points in controls. Probabilities of being a cancer patient were 96%, 98%, and 100% when using the 95th percentiles of spontaneous and NNK-induced micronuclei, nucleoplasmic bridges, and nuclear buds, respectively. Our study indicates that the CBMN assay is extremely sensitive to NNK-induced genetic damage and may serve as a strong predictor of lung cancer risk.

Early manifestations of NNK-induced lung cancer: role of lung immunity in tumor susceptibility

A strong correlation exists between smoking and lung cancer; however, susceptibility to lung cancer among smokers is not uniform. Similarly, mice show differential susceptibility to the tobacco carcinogen nitrosamine 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which produces lung tumors in A/J but not in C3H mice. Host immunity may play a role in the susceptibility to cancer, and cigarette smoke/nicotine suppresses the immune system through activation of nicotinic acetylcholine receptors (nAChRs). Mammalian lungs express alpha7-nAChRs, and NNK is a high-affinity agonist for alpha7-nAChRs. To examine whether NNK differentially modulates lung immunity in susceptible and resistant mouse strains, A/J and C3H mice were treated with NNK and/or immunized with sheep red blood cells. Lung tissues and RNA of treated and untreated animals were analyzed by immunohistochemistry and RT-PCR for alpha7-nAChR and COX-2 expression. Spleen- and the lung-associated lymph node cells from control and immunized animals were assessed for immunologic responses, including anti-sheep red blood cell antibody plaque-forming cells, concanavalin A-induced T-cell proliferation, and the anti-CD3/CD28 antibody-induced rise in intracellular calcium. NNK strongly suppressed these responses in A/J but not in C3H mice. Similar NNK-induced immunologic changes were seen in another pair of carcinogen-sensitive (NGP) and relatively carcinogen-resistant (B10.A) mouse strains. Moreover, NNK stimulates a significantly higher expression of COX-2 and alpha7-nAChRs in A/J than in C3H lungs. These results suggest that the susceptibility to chemical carcinogenesis among various mouse strains might be influenced by their immunologic response to the carcinogen.

Bile-reflux into the pancreatic ducts is associated with the development of intraductal papillary carcinoma in hamsters

BACKGROUND

Reflux of pancreatic juice into the biliary tract is a well-known risk factor for the development of biliary carcinoma. In this study, we investigated the significance of bile-reflux into the pancreatic ducts in pancreatic carcinogenesis, especially in the development of carcinoma in the main pancreatic duct in hamsters.

MATERIALS AND METHODS

Syrian hamsters were subjected to three different surgical procedures: cholecystoduodenostomy with dissection of the extrahepatic bile duct on the distal end of the common duct (Model A); cholecystoduodenostomy along with a dissection of the common bile duct (Model B); or simple laparotomy (Model C). The animals then received weekly subcutaneous injections of N-nitrosobis(2-oxopropyl)amine (BOP), for 9 weeks, and were killed for pathological investigation at 16 weeks after the initial BOP administration.

RESULTS

Pancreas carcinomas developed in 95, 88, and 90% of the Model A hamsters (n = 22), B (n = 24), and C (n = 21), respectively. The induced pancreatic tumors were histologically classified into four types: papillary; tubular; cystic adenocarcinoma; or intraductal carcinoma of the main pancreatic duct consisting of intraductal papillary carcinoma (IPC) and intraductal tubular carcinoma (ITC). The number and the incidence of IPCs induced in Model A hamsters were 24 lesions and 77% and were statistically higher than those in Model B (7 lesions and 29%) and C hamsters (7 lesions and 33%) (P < 0.01). Bile-reflux into the pancreatic ducts was clearly demonstrated in only hamsters of Model A by means of Indocyanine green injection via the portal vein. Proliferative cell nuclear antigen labeling indices of the epithelial cells in the main pancreatic duct in hamsters, with no BOP treatment, were 3.8, 0.8, and 1.1% in Models A (n = 10), B (n = 10), and C (n = 10), respectively, and the difference was statistically significant (P < 0.01).

CONCLUSIONS

Our findings suggest that bile-reflux into the pancreatic ducts is a significant factor predisposing to the development of IPC of the pancreas through an acceleration of epithelial cell kinetics of the main pancreatic duct.

Alterations in the Smad4 gene in hamster pancreatic duct adenocarcinomas and established cell lines

Alterations of the Smad4 gene, identified as a mediator of the transforming growth factor-beta pathway, were investigated in hamster pancreatic duct adenocarcinomas (PDAs) and established cell lines. Female Syrian golden hamsters received 70 mg/kg of N-nitrosobis(2-oxopropyl)amine (BOP) followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine then L-methionine and a further administration of 20 mg/kg BOP. A total of 12 PDAs obtained 10 weeks after beginning the experiment and three cell lines established from subcutaneously transplantable PDAs in syngeneic hamsters were examined for mutations using reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis. A mutation was detected in only one PDA (1/12, 8.3%) in the form of an ACC to ATC (Thr to IIe) transition at codon 73; none were detected in the three cell lines. No reduced or increased expression of the Smad4 gene was detected in any case using real-time quantitative RT-PCR. These results suggest that the Smad4 gene might play a role in limited fraction of BOP-induced pancreatic duct carcinogenesis in hamsters.

Proteomics: Recent Applications and New Technologies

Interest in proteomics as a tool for drug development and a myriad of other applications continues to expand at a rapid rate. Proteomic analyses have recently been conducted on tissues, biofluids, subcellular components and enzymatic pathways as well as various disease and toxicological states, in both animal models and man. In addition, several recent studies have attempted to integrate proteomics data with genomics and/or metabonomics data in a systems biology approach. The translation of proteomic technology and bioinformatics tools to clinical samples, such as in the areas of disease and toxicity biomarkers, represents one of the major opportunities and challenges facing this field. An ongoing challenge in proteomics continues to be the analysis of the serum proteome due to the vast number and complexity of proteins estimated to be present in this biofluid. Aside from the removal of the most abundant proteins, a number of interesting approaches have recently been suggested that may help reduce the overall complexity of serum analysis. In keeping with the increasing interest in applications of proteomics, the tools available for proteomic analyses continue to improve and expand. For example, enhanced tools (such as software and labeling procedures) continue to be developed for the analysis of 2D gels and protein quantification. In addition, activity-based probes are now being used to tag, enrich and isolate distinct sets of proteins based on enzymatic activity. One of the most active areas of development involves microarrays. Antibody-based microarrays have recently been released as commercial products while numerous additional capture agents (e.g. aptamers) and many additional types of microarrays are being explored.

Nitric Oxide–Donating Aspirin Prevents Pancreatic Cancer in a Hamster Tumor Model

To evaluate the chemopreventive effect of nitric oxide-donating aspirin (NO-ASA), an ASA bearing a NO-releasing moiety, against pancreatic cancer, we studied six groups of female Syrian golden hamsters: groups 1 to 3 (n = 12 each) were given saline and groups 4 to 6 (n = 17) the carcinogen N-nitrosobis(2-oxopropyl)amine (BOP) s.c. in five weekly injections (the first, 70 mg/kg, and the remaining, 20 mg/kg each). Control and BOP-treated hamsters were fed a NO-ASA 3,000 ppm or conventional ASA 3,000 ppm or control diet for 19 weeks. Groups 1 to 3 had no tumors. Compared with the BOP/vehicle group, NO-ASA reduced the incidence (88.9%, P < 0.003) and multiplicity (94%, P < 0.05) of pancreatic cancer; ASA had no statistically significant effect. NO-ASA arrested the transition from PanIN2 to PanIN3 and carcinoma. The proliferation (proliferating cell nuclear antigen) / apoptosis (terminal deoxyribonucleotide transferase-mediated nick-end labeling) ratio of ductal cells increased with the histologic severity of the ductal lesion; NO-ASA suppressed it significantly during all stages except PanIN1A. p21(WAF1/CIP1), undetectable in normal cells, was progressively induced in neoplastic cells and suppressed by NO-ASA up to PanIN3. Nuclear factor-kappaB activation, absent in normal tissue, increased progressively (17-fold in cancer); NO-ASA suppressed it throughout and significantly in PanIN1B and PanIN2. Cyclooxygenase-2 expression, absent during early stages, was induced 6-fold in carcinoma and suppressed by NO-ASA in PanIN3 and carcinoma. Conventional ASA had no effect on these molecular markers. Thus, NO-ASA profoundly prevented pancreatic cancer and modulated multiple molecular targets in this model system; conventional ASA had no such effects. NO-ASA merits further evaluation as a chemopreventive agent against pancreatic cancer.

Bcl2 suppresses DNA repair by enhancing c-Myc transcriptional activity

Bcl2 and c-Myc are two major oncogenic proteins that can functionally promote DNA damage, genetic instability, and tumorigenesis. However, the mechanism(s) remains unclear. Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the most potent carcinogen contained in cigarette smoke that induces cellular DNA damage. Here we found that Bcl2 potently suppresses the repair of NNK-induced abasic sites of DNA lesions in association with increased c-Myc transcriptional activity. The Bcl2 BH4 domain (amino acids 6-31) was found to bind directly to c-Myc MBII domain (amino acids 106-143), and this interaction is required for Bcl2 to enhance c-Myc transcriptional activity and inhibit DNA repair. In addition to mitochondria, Bcl2 is also expressed in the nucleus, where it co-localizes with c-Myc. Expression of nuclear-targeted Bcl2 enhances c-Myc transcriptional activity with suppression of DNA repair but fails to prolong cell survival. Depletion of c-Myc expression from cells overexpressing Bcl2 significantly accelerates the repair of NNK-induced DNA damage, indicating that c-Myc may be essential for the Bcl2 effect on DNA repair. It is known that apurinic/apyrimidinic endonuclease (APE1) plays a crucial role in the repair of abasic sites of DNA lesions. That overexpression of Bcl2 results in up-regulation of c-Myc and down-regulation of APE1 suggests APE1 may function as the downstream target of Bcl2/c-Myc in the DNA repair machinery. Thus, Bcl2, in addition to its survival function, may also suppress DNA repair in a novel mechanism involving c-Myc and APE1, which may lead to an accumulation of DNA damage in living cells, genetic instability, and tumorigenesis.

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.

FDG-PET in the detection of early pancreatic cancer in a BOP hamster model

BACKGROUND

The prognosis of pancreatic cancer (PC) is highly dependent on the stage of the disease, and early recognition improves survival. Positron emission tomography (PET) using (18)F-fluoro-2-deoxyglucose ([(18)F]FDG) has been established as an important clinical tool for PC diagnosis, but it is not known whether FDG-PET detects premalignant stages of PC. We speculate that [(18)F]FDG uptake precedes the onset of PC in a hamster model. We used the N-nitrosobis(2-oxopropyl)amine (BOP) model, as these animals consistently develop PC within 20 weeks after first injection.

METHODS

Male Syrian hamsters were injected once a week with 10 mg BOP/kg body weight for 10 consecutive weeks. Terminal autopsy took place in groups of five hamsters from 4 weeks until 28 weeks after first BOP injection. After an 8-h fast, hamsters were injected with [(18)F]FDG and sacrificed 1 h after [(18)F]FDG injection. The pancreata were histopathologically examined, and the [(18)F]FDG uptake was determined and expressed as percentage of the injected dose per gram tissue (%ID/g).

RESULTS

Seven of 55 hamsters developed macroscopic signs of tumor. Histopathological examination revealed PC in 13 hamsters. [(18)F]FDG uptake increased gradually with time and was significantly higher in the group with PC compared to the group without PC.

CONCLUSION

[(18)F]FDG accumulates preferentially in PC, and pancreata exposed to BOP showed a gradual increase in [(18)F]FDG accumulation.

Influence of different dietary fat intake on liver metastasis and hepatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

OBJECTIVES

Effects of polyunsaturated fatty acids (PUFA) on carcinogenesis are discussed controversially. Thus, tumor growth seems to be influenced by type and composition of fat dietary; however, the pathomechanism is still unknown. Therefore, we investigated the impact of different PUFAs on liver metastasis and hepatic lipid peroxidation in a solid model of ductal pancreatic cancer in Syrian hamsters.

METHODS

90 male hamsters were randomized into 6 groups (n = 15). Accordingly groups 2, 4 and 6 received 10 mg N-nitrosobis-2-oxopropylamine (BOP)/kg body weight weekly by subcutaneous injection for 12 weeks in order to induce ductal pancreatic cancer, while groups 1, 3 and 5 were treated with 0.5 ml 0.9% sodium chloride. All hamsters received a standard fat diet (SFD) rich in n-6 PUFA for 16 weeks (2.9% fat). Afterwards, groups 1 and 2 had free access to SFD, while groups 3 and 4 were given a diet enriched with n-3, n-6 and n-9 PUFA (SMOF) and groups 5 and 6 were fed a diet high in n-3 PUFA (FISH-OIL). After 32 weeks all hamsters were sacrificed in order to determine incidence of pancreatic carcinoma and liver metastasis. Furthermore hepatic activities of glutathionperoxidase (GSH-Px) and superoxiddismutase (SOD) as well as levels of lipidperoxidation were analyzed intra- and extrametastatically.

RESULTS

The incidence of liver metastasis was decreased in the FISH-OIL tumor group compared to the SFD and SMOF groups. However, GSH-Px activity was not influenced by different diets. Extrametastatic hepatic SOD activity did not differ between all groups, while intrametastatic hepatic SOD activity in the SFD-BOP group was increased. In the FISH-OIL-BOP and the SMOF-BOP group intrametastatic SOD activity was lower than in non-metastatic hepatic tissue. Furthermore levels of hepatic lipid peroxidation were decreased in the tumor groups treated with fish oil and SMOF compared to the SFD group. Comparing intra- and extrametastatic TBARS concentration there was no difference in the SFD-BOP and the SMOF-BOP groups, while in the FISH-OIL-BOP group intrametastatic TBARS concentration was increased.

CONCLUSION

Conclusively, fish oil reduced the incidence of liver metastasis in experimental ductal pancreatic cancer. Maybe this effect is caused by an increase of intrametastatic hepatic lipid peroxidation.

Chemopreventive Effects of Deguelin, a Novel Akt Inhibitor, on Tobacco-Induced Lung Tumorigenesis

Tobacco carcinogens induce Akt activation and lung carcinogenesis. We previously demonstrated that deguelin, a natural plant product, specifically inhibits the proliferation of premalignant and malignant human bronchial epithelial cells by blocking Akt activation. To evaluate the ability of deguelin to block tobacco carcinogen-induced lung tumorigenesis, we evaluated the in vivo effects of deguelin on Akt activation and lung tumorigenesis in transgenic mice in which Akt expression was induced by tamoxifen and in 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK)/benzo(a)pyrene (BaP)-treated A/J mice. Deguelin suppressed Akt activation in vivo, as measured by immunohistochemistry and immunoblotting, and statistically significantly reduced NNK/BaP-induced lung tumor multiplicity, volume, and load in A/J mice, as monitored by microcomputed tomography image analysis, with no detectable toxicity. These results indicate that deguelin warrants consideration as a chemopreventive agent for early-stage lung carcinogenesis in a clinical lung cancer chemoprevention trial.

Angiotensin II type 2 receptor gene deficiency attenuates susceptibility to tobacco-specific nitrosamine-induced lung tumorigenesis: involvement of transforming growth factor-beta-dependent cell growth attenuation

To clarify an involvement of angiotensin II signaling in lung neoplasia, we have examined the effect of angiotensin II receptor deficiency on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis. Male angiotensin II type 2 receptor (AT2)-null mice with an SWR/J genetic background and control wild-type mice were treated with NNK (100 mg/kg, i.p.) or saline vehicle. NNK treatment caused the development of lung tumors in all wild-type control mice (100 % tumor prevalence), but only 85% of AT2-null mice developed tumors. The tumor multiplicity in AT2-null mice (1.9 +/- 0.3) was significantly smaller than that in wild-type mice (4.1 +/- 0.9). Primary cultured lung fibroblasts prepared from both AT2-null and wild-type mice markedly increased the colony counts of A549 lung cancer cells in soft agar, but a consistently higher colony count was observed with the wild-type fibroblasts (fold increase in colony number, 5.6 +/- 0.5) than with the AT2-null fibroblasts (3.5 +/- 0.8). The underlying mechanism by which angiotensin II regulates cancer cell growth is due to the regulation of active transforming growth factor-beta (TGF-beta) production. Although the total level of TGF-beta was significantly stimulated when A549 cells were cocultured with either type of fibroblasts, the level of active TGF-beta in the conditioned medium was consistently higher with AT2-null fibroblasts than with wild-type fibroblasts. These results imply that the AT2 receptor negatively regulates the level of active TGF-beta and thus increases NNK-induced lung tumorigenesis. The AT2 receptor function in lung stromal fibroblasts may be a potential modulator of tumor susceptibility in chemical carcinogen-induced lung tumorigenesis.

Lung cancer susceptibility in Fhit-deficient mice is increased by Vhl haploinsufficiency

The FHIT gene plays important roles in cancer development, including lung cancers, in which the Fhit protein is frequently lost. To determine if Fhit-deficient mice exhibit increased susceptibility to carcinogen-induced lung cancer, mice were treated with the pulmonary carcinogen 4-methylnitrosamino-1-3-pyridyl-1-butanone. Wild-type and Fhit-deficient animals did not exhibit significantly different frequencies of lung lesions, but Fhit-/- mice showed significantly increased average tumor volume (1.62 mm3) and multiplicity in tumor-bearing mice, compared with wild-type mice (0.70 mm3). Tumors of Fhit-/- mice were all carcinomas, whereas Fhit+/+ mice did not develop carcinomas. To determine if Fhit absence, in combination with deficiency of an additional 3p tumor suppressor, would affect the frequency of tumor induction, we examined the spontaneous and dimethylnitrosamine-induced tumor phenotype of Fhit-/-Vhl+/- mice. Whereas no spontaneous lung tumors were observed in Fhit-/- or Vhl+/- mice, 44% of Fhit-/-Vhl+/- mice developed adenocarcinomas by 2 years of age. Dimethylnitrosamine (6 mg/kg body weight) induced lung tumors (adenomas and carcinomas) in 100% of Fhit-/-Vhl+/- mice and adenomas in 40% of Fhit-/- mice by 20 months of age. Thus, double deficiency in murine homologues of 3p suppressor genes, including haploinsufficiency of Vhl, predisposes to spontaneous and induced lung cancers, showing that Fhit-deficient mice will be useful, in combination with other 3p tumor suppressors, in recapitulating a pattern of lung cancer development similar to the human pattern; such double- or triple-deficient mice will be excellent lung cancer prevention and therapy models.

A polymorphism in the 5'-flanking region of the CYP2E1 gene and elevated lung adenocarcinoma risk in a Japanese population

Cytochrome P450 2E1 (CYP2E1) catalyzes the metabolic activation of the procarcinogen, N-nitrosodimethylamine, and cytotoxic carbon tetrachloride compounds. A tandem repeat polymorphism in the 5'-flanking region of the CYP2E1 gene was investigated in non-small cell lung carcinoma (NSCLC) patients to clarify the relationship between CYP2E1 gene polymorphism and lung cancer susceptibility. Blood samples were taken from 236 healthy control subjects (192 males and 44 females) and 111 patients (78 males and 33 females) who underwent surgery for NSCLC in Japan. DNA was isolated from these samples and the 5'-flanking region of the CYP2E1 gene was amplified by polymerase chain reaction and examined for tandem repeat polymorphisms using DNA fragment analysis. Sequence analysis confirmed the presence of three alleles, A2, A3, and A4 (361, 367, and 457 bp, respectively), with four genotypes observed in the lung cancer group and five genotypes in the control group. There was a statistically significant difference in genotype distribution between the lung adenocarcinoma and control group (P=0.0088, A4/A4 vs. non-A4/A4). In the lung adenocarcinoma group, the univariate risk estimates for the A4/A4 subgroup compared to the most common subgroup (A2/A2) was 4.300 (95% confidence interval = 1.358-13.618, P=0.0131). We conclude that the A4/A4 genotype of the 5'-flanking region of CYP2E1 was significantly more frequent in lung adenocarcinoma cases than in healthy controls and, therefore, may be involved in the development of lung adenocarcinoma.

Phenethyl Isothiocyanate and Sulforaphane and their N-Acetylcysteine Conjugates Inhibit Malignant Progression of Lung Adenomas Induced by Tobacco Carcinogens in A/J Mice

We have shown previously that naturally occurring isothiocyanates derived from cruciferous vegetables and their N-acetylcysteine conjugates inhibit lung adenoma formation induced by tobacco carcinogens in A/J mice at the post-initiation stage. The tumor-inhibitory activity by these compounds is linked with activation of activator protein and induction of apoptosis in lung tissues, suggesting that these compounds may also inhibit the development of adenomas to adenocarcinomas in lung. In this study, the chemopreventive activity of phenethyl isothiocyanate and sulforaphane and their N-acetylcysteine conjugates during progression of lung adenomas to malignant tumors was investigated in A/J mice. Mice were divided into 14 groups and treated with a mixture of 3 micromol benzo(a)pyrene [B(a)P] and 3 micromol 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) given by gavage once weekly for 8 weeks. Twenty weeks after the beginning of carcinogen administration, a total of 20 mice in the treatment groups were sacrificed with an average yield of 7.3 +/- 4.5 lung adenomas per mouse. The remaining mice in each group were fed diets containing phenethyl isothiocyanate (3 and 1.5 mmol/kg diet), sulforaphane (3 and 1.5 mmol/kg diet), phenethyl isothiocyanate-N-acetylcysteine (8 and 4 mmol/kg diet), sulforaphane-N-acetylcysteine (8 and 4 mmol/kg diet) during weeks 21 to 42. Four mice in each of the high-dose treatment groups were sacrificed during weeks 28 and 36 and the bioassay was terminated during week 42; lung tissues were harvested for histopathologic examination of tumors and for cell proliferation (proliferating cell nuclear antigen) and apoptosis (caspase-3) assays using immunohistochemical staining. At termination, the incidence of adenocarcinoma in the 3 mmol/kg diet phenethyl isothiocyanate group and 8 mmol/kg diet phenethyl isothiocyanate-N-acetylcysteine group was reduced to 19% and 13%, respectively, compared with 42% in the carcinogen-treated control group. At the lower doses, phenethyl isothiocyanate and its N-acetylcysteine conjugate also inhibited the incidences of lung adenocarcinoma, however, the decreases were not statistically significant. The lung tumor incidences in groups treated with sulforaphane-N-acetylcysteine in the diet were also significantly reduced to 11% or 16%. Furthermore, the malignant lung tumor multiplicity was significantly reduced from 1.0 tumor/mouse in the carcinogen-treated control group to 0.3 in the sulforaphane low-dose group, 0.3 and 0.4 in the two sulforaphane-N-acetylcysteine groups, and 0.4 in the phenethyl isothiocyanate high-dose group. The malignant tumor multiplicities in other treatment groups were also reduced (0.5-0.8 tumors/mouse), but not significantly. Unlike lung adenocarcinomas, both incidences and multiplicities of lung adenomas were not much affected by treatment with isothiocyanates or their conjugates. Immunohistochemical examination of the lung tumors from all time points indicated that significant reduction in proliferating cell nuclear antigen and induction of apoptosis (terminal nucleotidyl transferase-mediated nick end labeling and caspase-3) were observed in the isothiocyanate and isothiocyanate-N-acetylcysteine-treated groups that showed inhibition of the development of lung adenocarcinomas. The results of the study provide a basis for future evaluation of the potential of phenethyl isothiocyanate and sulforaphane and their conjugates as chemopreventive agents in smokers and ex-smokers with early lung lesions.

Cocarcinogenic Effects of Islet Hormones and N-Nitrosomorpholine in Hepatocarcinogenesis after Intrahepatic Transplantation of Pancreatic Islets in Streptozotocin-Diabetic Rats

In contrast to high local insulin levels obtained after low-number transplantation (n = 350) of islets of Langerhans into the livers of diabetic rats, low insulin levels after high-number transplantation (n = 1,000) do not suffice to induce hepatocarcinogenesis. Herein, we investigated the possible cocarcinogenic potential of high and, in particular, low insulin levels, combining this in vivo model with a chemical model of hepatocarcinogenesis after administration of N-nitrosomorpholine (NNM). In three main experiments, different schemes of single or continuous NNM administration were combined with different transplantation procedures in diabetic or nondiabetic animals, i.e., low-number and high-number islet transplantation, transplantation of polystyrene particles, and sham transplantation. Animals were sacrificed between 3 and 53 weeks after transplantation procedures. Evidence for the cocarcinogenic effects of NNM and insulin was provided in each main experiment. NNM treatment after low-number islet transplantation resulted in an increase in the number of preneoplastic hepatocellular foci, and a significant increase in the number and an earlier appearance of hepatocellular adenomas and carcinomas compared with controls. Most intriguing was the increase in preneoplastic foci after combined NNM treatment and high-number islet transplantation, proving that insulin, even in lower doses, has at least cocarcinogenic effects on the downstream hepatocytes and thus promotes an otherwise initiated hepatocarcinogenic process. Conclusively, intrahepatic transplantation of pancreatic islets acts as a strong cocarcinogenic factor together with NNM in streptozotocin-diabetic rats.

5-Lipoxygenase, a Marker for Early Pancreatic Intraepithelial Neoplastic Lesions

Pancreatic cancer has an abysmal prognosis because of late diagnosis. Therefore, it is important to identify risk factors if we are to be able to prevent and detect this cancer in an early, noninvasive stage. Pancreatic intraepithelial neoplasias (PanIN) are the precursor lesions which could be an ideal target for chemoprevention. This study shows up-regulation of 5-lipoxygenase (5-LOX) in all grades of human PanINs and early lesions of pancreatic cancer in two different animal models (EL-Kras mice and N-nitrosobis(2-oxopropyl)amine-treated hamsters) by immunohistochemistry. The results were consistent in all tissues examined, including seven chronic pancreatitis patients, four pancreatic cancer patients, one multiorgan donor, nine EL-Kras mice, and three N-nitrosobis(2-oxopropyl)amine-treated hamsters, all with PanINs. Overexpression of 5-LOX in NIH3T3 cells resulted in greater sensitivity of these cells to the growth inhibitory effects of the 5-LOX inhibitor Rev5901. These findings provide evidence that 5-LOX plays a key role in the development of pancreatic cancer. Furthermore, the lipoxygenase pathway may be a target for the prevention of this devastating disease.

Reduced expressions of Foxp1 and Rassf1a genes in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

To clarify the involvement of the Foxp1 and Rassf1a genes in lung carcinogenesis, we investigated their expressions in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats. Six week old male Wistar rats were given 2000 ppm BHP in their drinking water for 12 weeks and maintained without further treatment until they were sacrificed at 25 weeks. A total of 10 lung adenocarcinomas were obtained, along with the total RNA from each for assessment of expression by reverse transcription (RT)-polymerase chain reaction (PCR). The reduced expressions of the Foxp1 and Rassf1a genes were observed in some of the lung adenocarcinomas. These analyses were also confirmed by real-time quantitative RT-PCR. These results suggest that reduced expressions of Foxp1 and Rassf1a genes may play a role in the development of lung adenocarcinomas induced by BHP in rats.

Effects of the antioxidative vitamins A, C and E on liver metastasis and intrametastatic lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

BACKGROUND/AIMS

Antioxidative vitamins are known to inhibit metastasis. Therefore we evaluated the impact of vitamins A (retinol), C (ascorbic acid) and E (alpha-tocopherol) on liver metastasis in a model of ductal pancreatic adenocarcinoma in hamster.

METHODS

One hundred and twenty male Syrian hamsters were randomized into 8 groups (Gr.) (n = 15). Gr. 1-4 were given 0.5 ml normal saline subcutaneously (s.c.) weekly, whereas Gr. 5-8 received 10 mg N-nitrosobis(2-oxopropyl)amine (BOP)/kg body weight s.c. for 3 months for tumor induction. In the 13th week Gr. 2 and 6 were administered retinol, Gr. 3 and 7 received ascorbic acid and Gr. 4 and 8 were given alpha-tocopherol orally. No treatment was performed in Gr. 1 and 5. After 24 weeks animals were sacrificed, pancreas and liver were histologically determined. Activities of glutathione-peroxidase (GSH-Px), superoxide dismutase (SOD) and concentration of thiobarbituric-acid-reactive substances (TBARS) were analyzed in hepatic tissue.

RESULTS

Retinol and alpha-tocopherol decreased the incidence of liver metastases (44.4 vs. 86.7%, p < 0.05). The number and size of liver metastases were significantly reduced by retinol. Activities of GSH-Px and SOD were increased and concentration of TBARS was decreased in NML and LiMe by all vitamins.

CONCLUSION

Obviously, antioxidative vitamins prevent oxidative stress in hepatocytes. This may be one mechanism decreasing liver metastasis in pancreatic cancer in the present trial.

Pancreatic hepatocellular tumor

BACKGROUND

Hepatocellular differentiation of pancreatic cells has been observed under certain conditions in several species, including humans. Their cell of origin and biology has remained controversial. Generally, these lesions have been considered a degenerative process. The present study describes a neoplastic hepatocellular lesion in Syrian hamsters.

METHODS AND RESULTS

Syrian hamsters were treated with a high dose of pancreatic carcinogen, N-nitrosobis(2-oxopropyl)amine. The lesion was confined within a single islet and expressed albumin and HSA (hepatocyte-specific antigen). The pleomorphic tumor cells exhibited numerous mitotic figures and were intermingled with insulin and glucagon cells. The hamster had multicentric premalignant and malignant ductal-type lesions, most of which appeared to arise from within the islets. This is the first demonstration of pancreatic hepatoma.

CONCLUSION

Pancreatic islet cells appear to have the potential to transdifferentiate into neoplastic hepatocytes.

Lack of prepubertal administration of ethinyl estradiol on susceptibility to multiple organ carcinogenesis in rats exposed to 7,12-dimethylbenz[a]anthracene and N-bis(2-hydroxypropyl)nitrosamine during adolescence

Estrogen exposure during the adult period is widely known to promote tumor development in the female genital system, as well as in the mammary gland in experimental animals, but its carcinogenic potential with exposure at the prepubertal stage, for 6 weeks after birth, is not completely understood. In the present study, we therefore evaluated the modifying effects of prepubertal ethinyl estradiol (EE) treatment on susceptibility to multiple organ carcinogenesis with subsequent carcinogen exposure in F344 rats. Dams during the lactation period and their weaned offspring until postnatal-week 6 were fed diet containing 0, 0.2 or 1.0 ppm EE. The offsprings were then administered 7,12-dimethylbenz[a]anthracene (DMBA, 50mg/kg body weight) by gavage for mammary tumor induction in week 7 and given free access to drinking water containing N-bis (2-hydroxypropyl)nitrosamine (DHPN, 0.2%) for wide spectrum tumor induction in organs such as the thyroid, liver, lung and kidney from weeks 6-14. Male and female offspring were euthanized at weeks 27 and 36, respectively, for histopathological examination. While the incidence and multiplicity of mammary tumors showed a tendency for increase in females of the 0.2 and 1.0 ppm EE groups, this was without statistical significance. Furthermore, prepubertal EE exposure did not affect tumor induction in the thyroid, liver, lung, kidney, esophagus, ovary and lymphoid tissue in either sex. The present results thus indicate a lack of influence of estrogen early in life on carcinogenic susceptibility, although the possible impact on mammary carcinogenesis requires further examination.

β-Carotene interaction with NNK in the AJ-mouse model: Effects on cell proliferation, tumor formation and retinoic acid responsive genes

We studied the influence of beta-carotene on the tobacco smoke carcinogen 4-(N-Methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumor development in the A/J-mouse model. The normally low beta-carotene absorption was facilitated with a diet enriched in fat and bile salt, resulting in plasma and lung tissue levels similar to humans. beta-Carotene enhanced NNK-induced early bronchial cell proliferation, however, this effect was not predictive for later tumor development. Tumor multiplicity was not significantly affected by beta-carotene, neither in carcinogen-initiated nor in uninitiated mice, and regardless of dose and time point of supplementation during tumor development. RARbeta isoform and CYP26 gene expression levels analyzed by quantitative RT-PCR were weakly, but significantly, inversely correlated and showed evidence for altered retinoid signaling and catabolism in the lungs of NNK-initiated, beta-carotene supplemented mice. However, this interaction did not translate into enhanced tumor multiplicity. These results indicate that impaired retinoid signaling is not likely a key factor in lung tumorigenesis in this mouse model.

Nicotine 5'-oxidation and methyl oxidation by P450 2A enzymes

In smokers, the primary pathway of nicotine metabolism is P450 2A6-catalyzed 5'-oxidation. The nicotine Delta(5'(1'))-iminium ion product of this reaction is further metabolized to cotinine by aldehyde oxidase. Previous investigators have reported kinetic parameters for cotinine formation using human liver cytosol as a source of aldehyde oxidase. Using [5-(3)H]nicotine and radioflow high-performance liquid chromatography analysis, we determined kinetic parameters for nicotine 5'-oxidation by P450 2A6 and the closely related human extrahepatic P450 2A13 as well as the rodent P450s 2A3, 2A4, and 2A5. The formation of both cotinine and nicotine Delta(5'(1'))-iminium ion was monitored. The K(m) and V(max) values for P450 2A6 were 144 +/- 15 muM and 1.30 +/- 0.05 pmol/min/pmol, respectively. Previously reported K(m) values for cotinine formation by P450 2A6 in the presence of cytosol were much lower, ranging from 11 to 45 muM. P450 2A13 was a somewhat better catalyst of nicotine Delta(5'(1'))-iminium formation, with 2-fold lower K(m) and 2-fold higher V(max) values than P450 2A6. The rat P450 2A3 and the mouse P450 2A5, which are 85 and 84% identical to P450 2A6, were much more efficient catalysts of nicotine 5'-oxidation. P450 2A4 was not an efficient catalyst of nicotine metabolism. Whereas 5'-oxidation was the major pathway of nicotine metabolism for all five P450 2A enzymes, these enzymes also catalyzed methyl oxidation. Nornicotine, the product of this reaction was detected as 5 to 15% of the total nicotine metabolites. Nornicotine is the amine precursor to the esophageal carcinogen N'-nitrosonornicotine. Therefore, methyl oxidation of nicotine by P450 2A6 or P450 2A13 followed by nitrosation of nornicotine are possible endogenous pathways of N'-nitrosonornicotine formation.