Showing papers in "Carcinogenesis in 2004"
TL;DR: It is demonstrated that adult stem cells maintain expression of Oct4, consistent with the stem cell hypothesis of carcinogenesis, and a few cells found in the basal layer of human skin epidermis are expressed.
Abstract: The Oct3/4 gene, a POU family transcription factor, has been noted as being specifically expressed in embryonic stem cells and in tumor cells but not in cells of differentiated tissues. With the ability to isolate adult human stem cells it became possible to test for the expression of Oct3/4 gene in adult stem cells and to test the stem cell theory of carcinogenesis. Using antibodies and PCR primers we tested human breast, liver, pancreas, kidney, mesenchyme and gastric stem cells, the cancer cell lines HeLa and MCF-7 and human, dog and rat tumors for Oct4 expression. The results indicate that adult human stem cells, immortalized non-tumorigenic cells and tumor cells and cell lines, but not differentiated cells, express Oct4. Oct4 is expressed in a few cells found in the basal layer of human skin epidermis. The data demonstrate that adult stem cells maintain expression of Oct4, consistent with the stem cell hypothesis of carcinogenesis.
613 citations
TL;DR: The following review will summarize the strengths and weaknesses of available in vivo models of metastasis including transplantable syngeneic mouse and human-mouse xenografts, genetically engineered mice and naturally occurring cancers of companion animals (pet dogs and cats).
Abstract: Metastasis, the spread of a tumor from its primary site to other parts of the body, continues to be the most significant problem in the field of cancer. Patients who present with metastatic disease or those who develop metastases after successful management of the primary tumor carry a universally grave prognosis. To improve treatment outcomes for these patients a broader understanding of the biology of metastases is necessary. The biological complexity that characterizes metastasis requires complex experimental systems for its study. To a large extent the modeling of this biological complexity is only possible using animal models. The following review will summarize the strengths and weaknesses of available in vivo models of metastasis including transplantable syngeneic mouse and human-mouse xenografts, genetically engineered mice and naturally occurring cancers of companion animals (pet dogs and cats). No single metastasis model is sufficient to answer all questions. As such, the selection of the optimal model(s) for each biological or translational question is necessary.
430 citations
TL;DR: Curcumin affects arachidonic acid metabolism by blocking the phosphorylation of cPLA(2), decreasing the expression of COX-2 and inhibiting the catalytic activities of 5-LOX, which may contribute to the anti-inflammatory and anticarcinogenic actions of curcumin and its analogs.
Abstract: Aberrant arachidonic acid metabolism is involved in the inflammatory and carcinogenic processes. In this study, we investigated the effects of curcumin, a naturally occurring chemopreventive agent, and related beta-diketone derivatives on the release of arachidonic acid and its metabolites in the murine macrophage RAW264.7 cells and in HT-29 human colon cancer cells. We also examined their effects on the catalytic activities and protein levels of related enzymes: cytosolic phospholipase A(2) (cPLA(2)), cyclooxygenases (COX) as well as 5-lipoxygenase (5-LOX). At 10 micro M, dibenzoylmethane (DBM), trimethoxydibenzoylmethane (TDM), tetrahydrocurcumin (THC) and curcumin effectively inhibited the release of arachidonic acid and its metabolites in lipopolysaccharide (LPS)-stimulated RAW cells and A23187-stimulated HT-29 cells. Inhibition of phosphorylation of cPLA(2), the activation process of this enzyme, rather than direct inhibition of cPLA(2) activity appears to be involved in the effect of curcumin. All the curcuminoids (10 micro M) potently inhibited the formation of prostaglandin E(2) (PGE(2)) in LPS-stimulated RAW cells. Curcumin (20 micro M) significantly inhibited LPS-induced COX-2 expression; this effect, rather than the catalytic inhibition of COX, may contribute to the decreased PGE(2) formation. Without LPS-stimulation, however, curcumin increased the COX-2 level in the macrophage cells. Studies with isolated ovine COX-1 and COX-2 enzymes showed that the curcuminoids had significantly higher inhibitory effects on the peroxidase activity of COX-1 than that of COX-2. Curcumin and THC potently inhibited the activity of human recombinant 5-LOX, showing estimated IC(50) values of 0.7 and 3 micro M, respectively. The results suggest that curcumin affects arachidonic acid metabolism by blocking the phosphorylation of cPLA(2), decreasing the expression of COX-2 and inhibiting the catalytic activities of 5-LOX. These activities may contribute to the anti-inflammatory and anticarcinogenic actions of curcumin and its analogs.
424 citations
TL;DR: It is found that co-cultivation of tumour cells with macrophages leads to enhanced invasiveness of the malignant cells due to TNF-alpha dependent MMP induction in the macrophage.
Abstract: Apart from the neoplastic cells, malignant tumours consist of the extracellular matrix (ECM) and normal cells, in particular tumour-associated macrophages (TAM). To understand the mechanisms by which TAM can influence tumour cell invasion we co-cultured the human breast cancer cell lines MCF-7, SK-BR-3 and the benign mammary epithelial cell line hTERT-HME1 with macrophages. Co-incubation enhanced invasiveness of the tumour cells, while hTERT-HME1 remained non-invasive. Addition of the broad-spectrum matrix metalloprotease (MMP)-inhibitor FN 439, neutralizing MMP-9 or tumour necrosis factor-alpha (TNF-alpha) antibodies reduced invasiveness to basal levels. As shown by zymography, all cell lines produced low amounts of MMP-2, -3, -7 and -9 under control conditions. Basal MMP production by macrophages was significantly higher. Upon co-incubation, supernatant levels of MMPs -2, -3, -7 and -9 increased significantly, paralleled by an increase of MMP-2 activation. MMP-2 and -9 induction could be blocked by TNF-alpha antibodies. Co-culture of macrophages and hTERT-HME1 did not lead to MMP induction. In the co-cultures, mRNAs for MMPs and TNF-alpha were significantly up-regulated in macrophages, while the mRNA concentrations in the tumour cells remained unchanged. In summary, we have found that co-cultivation of tumour cells with macrophages leads to enhanced invasiveness of the malignant cells due to TNF-alpha dependent MMP induction in the macrophages.
382 citations
TL;DR: Novel treatments designed to exploit the knowledge of apoptotic mechanisms are under development to promote apoptosis of cancer cells and limit concurrent death of normal cells.
Abstract: Our somatic cells are born by mitosis and almost all will die by apoptosis, a physiological process of cellular suicide. Cancers can occur when this balance is disturbed, either by an increase in cell proliferation or a decrease in cell death. The goal of cancer therapy is to promote the death of cancer cells without causing too much damage to normal cells. Our knowledge of the mechanisms of apoptosis has enhanced our understanding of how some cancers originate and progress. It has also revealed that existing cancer therapies can work in two ways, by induction of apoptosis as well as by direct toxicity. In some cases resistance to apoptosis may explain why cancer therapies fail. Novel treatments designed to exploit our knowledge of apoptotic mechanisms are under development to promote apoptosis of cancer cells and limit concurrent death of normal cells.
354 citations
TL;DR: Long-term exposure of mice to arsenic in the drinking water can induce aberrant gene expression, global DNA hypomethylation, and the hypometHylation of the ER-alpha gene promoter, all of which could potentially contribute to arsenic hepatocarcinogenesis.
Abstract: Inorganic arsenic is a human carcinogen that can target the liver, but its carcinogenic mechanisms are still unknown. Global DNA hypomethylation occurs during arsenic-induced malignant transformation in rodent liver cells. DNA hypomethylation can increase gene expression, particularly when occurring in the promoter region CpG sites, and may be a non-genotoxic mechanism of carcinogenesis. Thus, in the present study liver samples of male mice exposed to 0 (control) or 45 p.p.m. arsenic (as NaAsO(2)) in the drinking water for 48 weeks were analyzed for gene expression and DNA methylation. Chronic arsenic exposure caused hepatic steatosis, a lesion also linked to consumption of methyl-deficient diets. Microarray analysis of liver samples showed arsenic induced aberrant gene expression including steroid-related genes, cytokines, apoptosis-related genes and cell cycle-related genes. In particular, the expression of the estrogen receptor-alpha (ER-alpha), and cyclin D1 genes were markedly increased. RT-PCR and immunohistochemistry confirmed arsenic-induced increases in hepatic ER-alpha and cyclin D1 transcription and translation products, respectively. Arsenic induced hepatic global DNA hypomethylation, as evidenced by 5-methylcytosine content of DNA and by the methyl acceptance assay. Arsenic also markedly reduced the methylation within the ER-alpha gene promoter region, as assessed by methylation-specific PCR, and this reduction was statistically significant in 8 of 13 CpG sites within the promoter region. Overall, in controls 28.3% of the ER-alpha promoter region CpG sites were methylated, but only 2.9% were methylated after chronic arsenic exposure. Thus, long-term exposure of mice to arsenic in the drinking water can induce aberrant gene expression, global DNA hypomethylation, and the hypomethylation of the ER-alpha gene promoter, all of which could potentially contribute to arsenic hepatocarcinogenesis.
278 citations
TL;DR: Data suggest that AKT activation is a frequent and early event in lung tumorigenesis, which may enhance risk of progression to malignancy and represent a potentially important target for chemoprevention in individuals at high risk of NSCLC.
Abstract: AKT is frequently activated in various cancers, but its involvement in lung tumor development and progression is not well established. We examined AKT activity by immunohistochemistry in 110 non-small cell lung carcinomas (NSCLCs) using tissue microarrays. AKT activation was observed in 56 (51%) tumors. To further validate activation of the AKT pathway in this series, we examined the phosphorylation status of the mammalian target of rapamycin (mTOR) and forkhead (FKHR), two downstream targets of AKT. Positive staining for phospho-mTOR and phospho-FKHR were detected in 74% and 68% of tumors, respectively, and was significantly associated with activation of AKT. Tumors positive for phosphorylated (active) AKT were present with a similar frequency in low stage (I/II) and high stage (III/IV) tumors, raising the possibility that AKT activation occurs early in tumor progression. We therefore examined AKT activity in 25 bronchial epithelial lesions from 12 patients at high risk of lung cancer. Metaplastic/dysplastic areas showed AKT activity, whereas normal and hyperplastic bronchial epithelia exhibited little or no activity. Since some bronchial epithelial lesions may develop into invasive cancers, we examined the effect of AKT on invasiveness of lung cancer cells, using an in vitro cell invasion assay. Transfection of NSCLC cells with wild-type AKT increased invasiveness in response to hepatocyte growth factor, whereas transfection with dominant negative AKT abrogated this effect. Collectively, these data suggest that AKT activation is a frequent and early event in lung tumorigenesis, which may enhance risk of progression to malignancy. Thus, AKT represents a potentially important target for chemoprevention in individuals at high risk of NSCLC.
273 citations
TL;DR: Results indicate that pre-S1/S2 mutant HBsAg, which make up GGHs, induce oxidative DNA damage and mutations in hepatocytes in the late stages of HBV infection.
Abstract: Ground glass hepatocytes (GGHs) are the historic hallmarks for the hepatocytes in the late and non-replicative stages of hepatitis B virus (HBV) infection. We have identified type I and type II GGHs that contain two mutant types of large HBV surface antigens (HBsAg) with deletions over the pre-S1 and pre-S2 regions, respectively. These pre-S mutant HBVsAg accumulate in endoplasmic reticulum (ER), resulting in strong ER stress. Type II GGHs often appear in hepatic nodules in the late phases of HBV infection and proliferate in clusters, suggesting that these mutant pre-S1/S2 HBsAg may be involved in HBV-related hepatocarcinogenesis, associated with ER stress. In this study, we investigated the potential genomic instability imposed by pre-S mutant HBsAg. Based on the analysis of comet assays, we found that the pre-S1 and pre-S2 mutant HBsAg caused oxidative stress and DNA damage. The DNA repair gene ogg1 was greatly induced by over-expression of pre-S mutant HBsAg. Induction of the DNA repair gene ogg1 was also detected in the pre-S2 HBsAg transgenic mice, as well as the type II GGHs from patients with hepatocellular carcinoma, strongly suggesting that the pre-S mutant HBsAg contributes to the oxidative DNA damage to hepatocytes. In addition, the mutation rates in the X-linked hprt gene were enhanced in mouse hepatoma ML1-4a cells, which constitutively expressed the pre-S1/S2 HBsAg. These results indicate that pre-S1/S2 mutant HBsAg, which make up GGHs, induce oxidative DNA damage and mutations in hepatocytes in the late stages of HBV infection.
272 citations
TL;DR: Evidence is provided that these n-3 PUFAs are able to inhibit VEGF expression in colon cancer cells and suggest that one possible mechanism involved may be the negative regulation of the COX-2/PGE(2) pathway.
Abstract: n-3 Polyunsaturated fatty acids (PUFAs) inhibit the development of microvessels in mammary tumors growing in mice. Human colorectal tumors produce vascular endothelial growth factor (VEGF) whose expression is up-regulated in tumor cells by both cyclooxygenase-2 (COX-2) and PGE(2) and directly correlated to neoangiogenesis and clinical outcome. The goal of this study was to examine the capability of n-3 PUFAs to regulate VEGF expression in HT-29 human colorectal cells in vitro and in vivo. Constitutive VEGF expression was augmented in cultured HT-29 cells by serum starvation and the effects of eicosapentaenoic (EPA) or docosahexaenoic acid (DHA) on VEGF, COX-2, phosphorylated extracellular signal-regulated kinase (ERK)-1 and -2 and hypoxia-inducible-factor 1-alpha (HIF-1alpha) expression and PGE(2) levels were assessed. Tumor growth, VEGF, COX and PGE(2) analysis were carried out in tumors derived from HT-29 cells transplanted in nude mice fed with either EPA or DHA. Both EPA and DHA reduced VEGF and COX-2 expression and PGE(2) levels in HT-29 cells cultured in vitro. Moreover, they inhibited ERK-1 and -2 phosphorylation and HIF-1alpha protein over-expression, critical steps in the PGE(2)-induced signaling pathway leading to the augmented expression of VEGF in colon cancer cells. EPA always showed higher efficacy than DHA in vitro. Both fatty acids decreased the growth of the tumors obtained by inoculating HT-29 cells in nude mice, microvessel formation and the levels of VEGF, COX-2 and PGE(2) in tumors. The data provide evidence that these n-3 PUFAs are able to inhibit VEGF expression in colon cancer cells and suggest that one possible mechanism involved may be the negative regulation of the COX-2/PGE(2) pathway. Their potential clinical application as anti-angiogenic compounds in colon cancer therapy is proposed.
260 citations
TL;DR: Evidence for cellular and molecular responses triggered by DADS that could be linked to its effect on histone acetylation and play a role in its protective properties on colon carcinogenesis is provided.
Abstract: Diallyl disulfide (DADS) is a naturally occurring organosulfur compound, from garlic, which exerts pleiotropic biological effects. In rodents, DADS inhibits colon chemically induced carcinogenesis. DADS anti-promoting effect may partly result from its ability to inhibit tumoral cell proliferation in vivo and in vitro. As far as DADS may modulate the expression of a subset of genes, we investigated DADS effect on histone acetylation, in two human colon tumor cell lines. Our study demonstrates that in Caco-2 and HT-29 cells treated for 6 h, 200 microM DADS increases histone H3 acetylation (x2 and x1.4, respectively). In Caco-2 cells, we also observed histone H4 hyperacetylation, preferentially at the lysine residues 12 and 16. We explored the effects of DADS and one of its metabolites, allyl mercaptan (AM), on histone deacetylase (HDAC) activity: using nuclear extracts of Caco-2 cells, 200 microM DADS decreased HDAC activity by 29% and AM at the same concentration was more efficient (92% inhibition). We also observed that DADS induced an increase in p21(waf1/cip1) expression, at mRNA and protein levels, in both cell lines. This effect was associated with an accumulation of cells in the G2 phase of the cell cycle. Our results suggest that in Caco-2 and HT-29 cells, DADS could inhibit cell proliferation through the inhibition of HDAC activity, histone hyperacetylation and increase in p21(waf1/cip1) expression. The present study provides evidence for cellular and molecular responses triggered by DADS that could be linked to its effect on histone acetylation and play a role in its protective properties on colon carcinogenesis.
240 citations
TL;DR: The mechanism that make catechins cytotoxic in certain tumor cells is due to their ability to produce H(2)O( 2) and that the resulting increase in H-O-2 levels triggers Fe(II)-dependent formation of highly toxic hydroxyl radical, which in turn induces apoptotic cell death.
Abstract: Although (-)-epigallocatechin gallate (EGCG) has been reported to induce apoptosis in a variety of tumor cells, detailed mechanisms remain to be explored. In the present study, we investigated the antitumor mechanism of EGCG by using human T-cell acute lymphoblastic leukemia Jurkat cells. We focused on the involvement of reactive oxygen species, as we found previously that EGCG caused apoptotic cell death in osteoclastic cells due mainly to promotion of the reduction of Fe(III) to Fe(II) to trigger Fenton reaction, which affords hydroxyl radical from hydrogen peroxide [H(2)O(2) + Fe(II) --> (*)OH + OH(-) + Fe(III)]. EGCG (12.5-50 micro M) decreased the viability of Jurkat cells and caused concomitant increase in cellular caspase-3 activity. Catalase and the Fe(II)-chelating reagent o-phenanthroline suppressed the EGCG effects, indicating involvements of both H(2)O(2) and Fe(II) in the mechanism. Unexpectedly, epicatechin gallate (ECG), which has Fe(III)-reducing potency comparable with EGCG, failed to decrease the viability of Jurkat cells, while epigallocatechin (EGC), which has low capacity to reduce Fe(III), showed cytotoxic effects similar to EGCG. These results suggest that, unlike in osteoclastic cells, a mechanism other than Fe(III) reduction plays a role in catechin-mediated Jurkat cell death. We found that EGCG causes an elevation of H(2)O(2) levels in Jurkat cell culture, in cell-free culture medium and sodium phosphate buffer. Catechins with a higher ability to produce H(2)O(2) were more cytotoxic to Jurkat cells. Hydrogen peroxide itself exerted Fe(II)-dependent cytotoxicity. Amongst tumor and normal cell lines tested, cells exhibiting lower H(2)O(2)-eliminating activity were more sensitive to EGCG. From these findings, we propose the mechanism that make catechins cytotoxic in certain tumor cells is due to their ability to produce H(2)O(2) and that the resulting increase in H(2)O(2) levels triggers Fe(II)-dependent formation of highly toxic hydroxyl radical, which in turn induces apoptotic cell death.
TL;DR: Lung cancer risk is only moderately increased by single DNA repair gene variants investigated but it is considerably enhanced by specific combinations of variant alleles, especially in patients with SCC.
Abstract: Several polymorphisms in DNA repair genes have been reported to be associated with lung cancer risk including XPA (-4G/A), XPD (Lys751Gln and Asp312Asn), XRCC1 (Arg399Gln), APE1 (Asp148Glu) and XRCC3 (Thr241Met). As there is little information on the combined effects of these variants, polymorphisms were analyzed in a case-control study including 463 lung cancer cases [among them 204 adenocarcinoma and 212 squamous cell carcinoma (SCC)] and 460 tumor-free hospital controls. Odds ratios (OR) adjusted for age, gender, smoking and occupational exposure were calculated for the variants alone and combinations thereof. For homozygous individuals carrying the Glu variant of APE1, a protective effect was found (OR = 0.77, CI = 0.51-1.16). Individuals homozygous for the variants XPA (-4A) (OR = 1.53, CI = 0.94-2.5), XPD 751Gln (OR = 1.39, CI = 0.90-2.14) or XRCC3 241Met (OR = 1.29, CI = 0.85-1.98) showed a slightly higher risk for lung cancer overall. In the subgroup of adenocarcinoma cases, adjusted ORs were increased for individuals homozygous for XPA (-4A) (OR = 1.62, CI = 0.91-2.88) and XRCC3 241Met (OR = 1.65; CI = 0.99-2.75). When analyzing the combined effects of variant alleles, 54 patients and controls were identified that were homozygous for two or three of the potential risk alleles [i.e. the variants in nucleotide excision repair, XPA (-4A) and XPD 751Gln, and in homologous recombination, XRCC3-241Met]. ORs were significantly increased when all patients (OR = 2.37; CI = 1.26-4.48), patients with SCC (OR = 2.83; CI = 1.17-6.85) and with adenocarcinoma (OR = 3.05; CI = 1.49-6.23) were analyzed. Combinations of polymorphisms in genes involved in the same repair pathway (XPA + XPD or XRCC1 + APE1) affected lung cancer risk only in patients with SCC. These results indicate that lung cancer risk is only moderately increased by single DNA repair gene variants investigated but it is considerably enhanced by specific combinations of variant alleles. Analyses of additional DNA repair gene interactions in larger population-based studies are warranted for identification of high-risk subjects.
TL;DR: This high-resolution analysis of DNA copy number alterations in colorectal cancer by array-based CGH allowed for the identification of many small, previously uncharacterized, genomic regions, such as on chromosomes 8 and 20.
Abstract: Array-based comparative genomic hybridization (CGH) allows for the simultaneous examination of thousands of genomic loci at 1-2 Mb resolution Copy number alterations detected by array-based CGH can aid in the identification and localization of cancer causing genes Here we report the results of array-based CGH in a set of 125 primary colorectal tumors hybridized onto an array consisting of 2463 bacterial artificial chromosome clones On average, 173% of the entire genome was altered in our samples (85 +/- 67% gained and 88 +/- 73% lost) Losses involving 8p, 17p, 18p or 18q occurred in 37, 46, 49 and 60% of cases, respectively Gains involving 8q or 20q were observed 42 and 65% of the time, respectively A transition from loss to gain occurred on chromosome 8 between 41 and 48 Mb, with 25% of cases demonstrating a gain of 8p11 (45-53 Mb) Chromosome 8 also contained four distinct loci demonstrating high-level amplifications, centering at 449, 60, 927 and 1447 Mb On 20q multiple high-level amplifications were observed, centering at 323, 378, 454, 547, 594 and 65 Mb Few differences in DNA copy number alterations were associated with tumor stage, location, age and sex of the patient Microsatellite stable and unstable (MSI-H) tumors differed significantly with respect to the frequency of alterations (20 versus 5%, respectively, P < 001) Interestingly, MSI-H tumors were also observed to have DNA copy number alterations, most commonly involving 8q This high-resolution analysis of DNA copy number alterations in colorectal cancer by array-based CGH allowed for the identification of many small, previously uncharacterized, genomic regions, such as on chromosomes 8 and 20 Array-based CGH was also able to identify DNA copy number changes in MSI-H tumors
TL;DR: The results show a relationship between the pro-inflammatory potential of S.bovis proteins and their pro-carcinogenic properties, confirming the linkage between inflammation and colon carcinogenesis and support the hypothesis that colonic bacteria can contribute to cancer development particularly in chronic infection/inflammation diseases.
Abstract: Several studies reported linkage between bacterial infections and carcinogenesis. Streptococcus bovis was traditionally considered as a lower grade pathogen frequently involved in bacteremia and endocarditis. This bacterium became important in human health as it was shown that 25-80% of patients who presented a S.bovis bacteremia had also a colorectal tumor. Moreover, in previous experiments, we demonstrated that S.bovis or S.bovis wall extracted antigens (WEA) were able to promote carcinogenesis in rats. The aim of the present study was: (i) to identify the S.bovis proteins responsible for in vitro pro-inflammatory properties; (ii) to purify them; (iii) to examine their ability to stimulate in vitro IL-8 and COX-2 expression by human colon cancer cells; and (iv) to assess in vivo their pro-carcinogenic potential in a rat model of colon carcinogenesis. The purified S300 fraction, as determined by proteomic analysis, contained 72 protein spots in two-dimensional gel electrophoresis representing 12 different proteins able to trigger human epithelial colonic Caco-2 cells and rat colonic mucosa to release CXC chemokines (human IL-8 or rat CINC/GRO) and prostaglandins E 2 , correlated with an in vitro over-expression of COX-2. Moreover, these proteins were highly effective in the promotion of pre-neoplastic lesions in azoxymethane-treated rats. In the presence of these proteins, Caco-2 cells exhibited enhanced phosphorylation of the three classes of MAP kinases. Our results show a relationship between the pro-inflammatory potential of S.bovis proteins and their pro-carcinogenic properties, confirming the linkage between inflammation and colon carcinogenesis. These data support the hypothesis that colonic bacteria can contribute to cancer development particularly in chronic infection/ inflammation diseases where bacterial components may interfere with cell function.
TL;DR: The results suggest that the CYP2A6 is one of the principal determinants affecting not only smoking behavior but also susceptibility to tobacco-related lung cancer.
Abstract: We reported previously that subjects homozygous for the cytochrome P450 2A6 (CYP2A6) (*)4 have a lower risk of lung cancer. The purpose of this study was to clarify whether or not the alterations of smoking behavior and risk for lung cancer could be found in subjects possessing novel CYP2A6 variants discovered recently. An epidemiological study was performed with 1094 cases and 611 controls in male Japanese smokers. It was found that the amounts of daily cigarette consumption in subjects who harbored CYP2A6(*)4/(*)7, (*)4/(*)10, (*)7/(*)7, (*)7/(*)9 and (*)4/(*)4 genotypes were significantly less than those in subjects carrying the (*)1/(*)1 genotype (P < 0.01). Even after adjustment with cigarette consumption, the adjusted odds ratios (ORs) for lung cancer were significantly lower in subjects who harbored CYP2A6(*)1/(*)4, (*)1/(*)7, (*)1/(*)9, (*)1/(*)10, (*)4/(*)4, (*)4/(*)7, (*)4/(*)9, (*)7/(*)7 and (*)7/(*)9 genotypes than those who possessed the (*)1/(*)1 genotype (P < 0.05). When participants were classified into four groups according to the CYP2A6 genotypes, group 1 ((*)1/(*)1), group 2 (heterozygotes for the (*)1 and a variant allele), group 3 (heterozygotes and homozygotes for variant alleles except for (*)4/(*)4) and group 4 ((*)4/(*)4), lung cancer risk was found to be less in subjects with the variant of CYP2A6 alleles [group 2, OR of 0.59 [95% confidence interval (CI), 0.44-0.79]; group 3, OR of 0.52 (95% CI, 0.37-0.72); group 4, OR of 0.30 (95% CI, 0.16-0.57)]. The reduced risk for lung cancer was seen more clearly in heavy smokers than in light smokers. Additional stratification analysis showed that the ORs for squamous cell carcinoma (OR of 0.07) and small cell carcinoma (OR of 0.10) were lower than that of adenocarcinoma (OR of 0.39) in group 4. These results suggest that the CYP2A6 is one of the principal determinants affecting not only smoking behavior but also susceptibility to tobacco-related lung cancer.
TL;DR: The data show for the first time that JNK, but not p38 or ERK signalling, plays an important role in curcumin-mediated apoptosis in human colon cancer cells that may underlie its chemopreventive effects.
Abstract: Curcumin, the major pigment of the dietary spice turmeric has the potential for chemoprevention by promotion of apoptosis. Mitogen-activated protein kinase (MAPK) and NF-kappa B (NFkappaB) signalling cascades are thought to regulate apoptosis and cell survival. While curcumin inhibits NFkappaB, its effects upon the MAPK pathways are unclear. This study investigates curcumin effects upon MAPK signalling and apoptosis in HCT116 cells. Here we report that curcumin time- and dose-dependent induction of apoptosis were accompanied by sustained phosphorylation and activation of c-jun N-terminal kinase (JNK) and p38 MAPK as well as inhibition of constitutive NFkappaB transcriptional activity. Curcumin treatment also induced JNK-dependent sustained phosphorylation of c-jun and stimulation of AP-1 transcriptional activity. Curcumin-mediated c-jun phosphorylation and apoptosis were reduced by treatment with the JNK-specific inhibitor SP600125. Conversely, the p38-specific inhibitor SB203580 had no effect upon curcumin-induced apoptosis. Curcumin treatment had no effect on the activity of extracellular signal-regulated protein kinase (ERK). Taken together, our data show for the first time that JNK, but not p38 or ERK signalling, plays an important role in curcumin-mediated apoptosis in human colon cancer cells that may underlie its chemopreventive effects.
TL;DR: The different effects exerted by DP as compared with CY suggest that the presence of the three hydroxyl groups on the beta ring in the molecular structure of DP may be important for its greater biological activity.
Abstract: To investigate the mechanistic basis for the biological properties of anthocyanins, two aglycone anthocyanins [delphinidin (DY) and cyanidin (CY)] were used to examine their effects on cell cycle progression and on induction of apoptosis in human cancer cells (uterine carcinoma and colon adenocarcinoma cells) and in normal human fibroblasts. These compounds differ in the number and position of hydroxyl groups on the beta ring in the molecular structure. Cellular uptake of anthocyanins was confirmed by HPLC analysis and no metabolites were detected. The clonogenic assay showed that CY induces a dose-dependent growth inhibitory effect only in fibroblasts. This effect was confirmed by flow cytometric analysis, showing a significant reduction of cells in S phase. In contrast, DP inhibited cell growth in normal and tumour cell lines. This event is accompanied in fibroblasts by an accumulation of cells in the S phase suggesting a block in the transition from S to G2 phase. On the other hand, in tumour cell lines we observed a reduction of cells in G1 phase, paralleled by the appearance of a fraction of cells with a hypodiploid DNA content, thus demonstrating an apoptotic effect by DP. The occurrence of apoptosis induced by DP was confirmed by morphological and biochemical features, including nuclear condensation and fragmentation, annexin V staining, DNA laddering and poly(ADP-ribose) polymerase-1-proteolysis. Furthermore, the mitochondrial membrane potential of apoptotic cells after treatment with DP was significantly lost. The different effects exerted by DP as compared with CY suggest that the presence of the three hydroxyl groups on the beta ring in the molecular structure of DP may be important for its greater biological activity.
TL;DR: It is suggested that individual susceptibility of bladder cancer may be modulated by MPO and MnSOD polymorphisms, and that the combination of genetic factors involved in oxidative stress response with environmental carcinogens may play an important role in bladder carcinogenesis.
Abstract: Tobacco smoking and occupational exposure are major risk factors of bladder cancer via exposure to polycyclic aromatic hydrocarbons (PAHs) and aromatic amines, which lead to oxidative stress and DNA damage. Several enzymes, which play key roles in oxidative stress are polymorphic in humans. Myeloperoxidase (MPO) produces a strong oxidant for microbicidal activity, and activates carcinogens in tobacco smoke. Catechol-O-methyltransferase (COMT) catalyzes the methylation of endo- and xenobiotics and prevents redox cycling. NAD(P)H:quinone oxidoreductase (NQO1) catalyzes the two-electron reduction of quinoid compounds, which also protects cells from redox cycling. Manganese superoxide dismutase (MnSOD) protects cells from free radical injury. To test the hypothesis that the risk of bladder cancer can be influenced by polymorphisms in the genes that modulate oxidative stress, in particular by interacting with environmental carcinogens, we conducted a hospital-based case-control study among men in Brescia, Northern Italy. We recruited and interviewed 201 incident cases and 214 controls from 1997 to 2000. Occupational exposures to PAHs and aromatic amines were coded blindly by occupational physicians. Unconditional multivariate logistic regression was applied to model the association between genetic polymorphisms and bladder cancer risk and the effect of modifications of smoking and occupational exposures were evaluated. MPO G-463A homozygous variant was associated with a reduced risk of bladder cancer with an OR of 0.31 (95% CI = 0.12-0.80). MnSOD Val/Val genotype increased the risk of bladder cancer with OR of 1.91 (95% CI = 1.20-3.04), and there was a combined effect with smoking (OR = 7.20, 95% CI = 3.23-16.1) and PAH (OR = 3.02, 95% CI = 1.35-6.74). We did not observe an effect of COMT Val108Met polymorphism. These findings suggest that individual susceptibility of bladder cancer may be modulated by MPO and MnSOD polymorphisms, and that the combination of genetic factors involved in oxidative stress response with environmental carcinogens may play an important role in bladder carcinogenesis.
TL;DR: Although the most ancient member of the p53 family, p63 is the most recently discovered and the least is known about this family member, and over-expression of select p63 splice variants is observed in many squamous carcinomas suggesting that p63 may act as an oncogene.
Abstract: Discovery of the p53 homologs p63 and p73 has brought new excitement to the p53 field. Identification of homologous genes coding for several proteins with similar and antagonistic properties towards p53 has been both intriguing and perplexing. A multitude of properties have been attributed to these new homologs and this review will focus on the biochemical and biological aspects of one family member, p63. Although the most ancient member of the p53 family, p63 is the most recently discovered and the least is known about this family member. Unlike p53, whose protein expression is not readily detectable in epithelial cells unless they are exposed to various stress conditions, p63 is expressed in select epithelial cells at high levels under normal conditions, p63 is highly expressed in embryonic ectoderm and in the nuclei of basal regenerative cells of many epithelial tissues in the adult including skin, breast myoepithelium, oral epithelium, prostate and urothelia. In contrast to the tumor suppressive function of p53, over-expression of select p63 splice variants is observed in many squamous carcinomas suggesting that p63 may act as an oncogene. Undoubtedly, the biochemical and biological activities attributed to p63 over the next several years will be diverse and regulation of the p63 gene and its several protein products complex. The use of various model systems and the study of human disease should continue to lead to rapid advances in our understanding of the role of p63 in development, epithelial cell maintenance and tumorigenesis.
TL;DR: Comparison of the suppressive effect on tumor growth of alpha-eleostearic acid with those of the CLA isomers confirmed that alpha-ESA had a stronger antitumor effect than CLA in cultured cell lines, and added alpha-tocopherol, an antioxidant, suppressed oxidative stress and apoptosis, suggesting that these effects were associated with lipid peroxidation.
Abstract: We have previously shown that conjugated linolenic acids (CLnA) prepared by alkaline isomerization have a stronger antitumor effect than conjugated linoleic acids (CLA). In this study we have compared the suppressive effect on tumor growth of alpha-eleostearic acid (alpha-ESA, 9Z11E13E-18:3) with those of the CLA isomers 9Z11E-CLA and 10E12Z-CLA, using nude mice into which DLD-1 human colon cancer cells were transplanted. The results showed that alpha-ESA, which is a CLnA that can be prepared from natural sources in bulk, had a stronger antitumor effect than CLA. DNA fragmentation was enhanced and lipid peroxidation was increased in tumor tissues of the alpha-ESA-fed mice, which suggested that alpha-ESA induced apoptosis via lipid peroxidation. Furthermore, treatment of DLD-1 cells with alpha-ESA, 9Z11E-CLA and 10E12Z-CLA confirmed that alpha-ESA had a stronger antitumor effect than CLA in cultured cell lines. The induction of apoptosis by alpha-ESA was consistent with enhanced DNA fragmentation, increased caspase activity and increased expression of caspase mRNA following alpha-ESA treatment. Addition of alpha-tocopherol, an antioxidant, suppressed oxidative stress and apoptosis, suggesting that these effects were associated with lipid peroxidation.
TL;DR: More frequent O.viverrini infection can induce the expression of iNOS not only in inflammatory cells but also in the epithelium of bile ducts and subsequently cause nitrosative and oxidative damage to nucleic acids, which may participate in the initiation and/or promotion steps of cholangiocarcinoma development.
Abstract: Chronic inflammation induced by repeated infection with Opisthorchis viverrini has been postulated to be a risk factor for cholangiocarcinoma. To clarify the mechanism of carcinogenesis induced by repeated O.viverrini infection, we investigated the timecourse of 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation, inducible nitric oxide synthase (iNOS) expression, nitric oxide production and pathological features in hamsters with two (2-IF) or three (3-IF) O.viverrini infections. Inflammatory cell infiltration triggered by repeated infection (3-IF > 2-IF > 1-IF) was earlier than by single infection (1-IF). HPLC coupled with an electrochemical detector revealed that 8-oxodG level in the liver was the highest on day 3 in 3-IF and day 7 in 2-IF, earlier than that on day 21 in 1-IF. Notably, a double immunofluorescence study revealed that formation of 8-nitroguanine and 8-oxodG appeared to increase in the epithelium of bile ducts in the order 3-IF > 2-IF > 1-IF after the decrease in inflammatory cells. This may be explained by the fact that repeated infection increased iNOS expression in the epithelium of bile ducts in the order 3-IF > 2-IF > 1-IF on day 90. Proliferating cell nuclear antigen accumulated in the epithelium of bile ducts on day 90 after repeated O.viverrini infection, supporting the hypothesis that cell proliferation was promoted by inflammation-mediated DNA damage. In conclusion, more frequent O.viverrini infection can induce the expression of iNOS not only in inflammatory cells but also in the epithelium of bile ducts and subsequently cause nitrosative and oxidative damage to nucleic acids, which may participate in the initiation and/or promotion steps of cholangiocarcinoma development.
TL;DR: It is suggested that for postmenopausal women with estrogen-dependent breast cancer, the consumption of foods containing soy flour is more advisable than consuming isoflavones in more purified forms.
Abstract: Soy-based products consumed in Asian countries are minimally processed whereas in the USA many of the soy foods and soy ingredients are highly processed. Soy foods contain complex mixtures of bioactive compounds, which may interact with one another. The objective of this study was to evaluate the ability of various soy products containing genistin, the glycoside form of genistein, to affect growth of MCF-7 cells transplanted into ovariectomized athymic mice. Products investigated included soy flour, two crude extracts of soy (soy molasses and Novasoy(R)), a mixture of isoflavones and genistin in pure form. Each of the soy flour-processed products was added to the diet to provide equivalent amounts of genistein aglycone equivalents (750 p.p.m.). Tumors in the negative control animals regressed throughout the study while the tumors in the soy flour-fed animals remained basically the same size (neither grew nor regressed). In animals consuming soy molasses, Novasoy(R), mixed isoflavones or genistin alone, tumor growth was stimulated when compared with animals consuming a control diet devoid of soy. These same dietary treatments resulted in increased cellular proliferation. Changes in mRNA expression of gene targets (estrogen responsiveness, cell cycle progression, apoptosis and aromatase activity) in tumors induced by the different diets were evaluated. The relative expression of pS2, progesterone receptor and cyclin D1 was increased in animals consuming the Novasoy(R), mixed isoflavones and genistin. Bcl2 mRNA expression was low in most of the dietary treatment groups compared with positive (estradiol implant) controls. Aromatase expression was not affected in any of the treatment groups. The degree of soy flour processing affects the estrogenicity of products containing a constant amount of genistein. Collectively, these findings suggest that for postmenopausal women with estrogen-dependent breast cancer, the consumption of foods containing soy flour is more advisable than consuming isoflavones in more purified forms.
TL;DR: This study reports that BITC significantly inhibits growth of human pancreatic cancer BxPC-3 cells in a concentration-dependent manner with an IC(50) of approximately 8 micro M, a concentration that can be generated through dietary intake of cruciferous vegetables.
Abstract: Benzyl isothiocyanate (BITC), a cruciferous vegetablederived compound, has been shown to inhibit chemically induced cancer in animal models. Moreover, epidemiological studies have provided compelling evidence to suggest that cruciferous vegetables may be protective against cancer risk. Here, we report that BITC significantly inhibits growth of human pancreatic cancer BxPC-3 cells in a concentration-dependent manner with an IC50 of ~8 mM, a concentration that can be generated through dietary intake of cruciferous vegetables. Treatment of BxPC-3 cells with growth suppressive concentrations of BITC resulted in G2/ M phase cell cycle arrest that was associated with a marked decline in protein levels of G2/M regulatory proteins including cyclin-dependent kinase 1 (Cdk1), cyclin B1 and cell division cycle 25B (Cdc25B). Further, BITC-mediated growth inhibition of BxPC-3 cells correlated with apoptosis induction that was characterized by an increase in Bax/ Bcl-2 ratio, cleavage of procaspase-3 and poly(ADP-ribose)polymerase (PARP), and an increase in cytoplasmic histone-associated DNA fragmentation. Interestingly, BITC treatment caused inhibition of nuclear factor kB (NF-kB) activation, which is constitutively activated in human pancreatic cancer. Western blotting revealed concentration-dependent decrease in NF-kB/Rel-p65 protein level in BxPC-3 cells upon exposure to BITC. An increase in protein level of inhibitory subunit k B( I kBa) in association with reduced serine-32 phosphorylation was also observed in BITC-treated BxPC-3 cells. Consistent with these findings, BITC treatment caused a decrease in nuclear translocation of NF-kB as reflected by reduced DNA-binding capacity of NF-kB. Furthermore, the protein level of cyclin D1, a transcriptional target of NF-kB, was reduced significantly in BITC-treated BxPC-3 cells. To the best of our knowledge, this study is the first published report to implicate suppression of NF-kB activation as a potential mechanism for anti-proliferative activity of BITC against human pancreatic cancer cells.
TL;DR: It is found that green tea components induce apoptosis via a TGF-beta superfamily protein, NAG-1 (Non-steroidal anti-inflammatory drug Activated Gene), and that ECG is the strongest Nag-1 inducer among the tested catechins and that treatment of HCT-116 cells results in an increasing G(1) sub-population, and cleavage of poly (ADP-ribose) polymerase (PARP), consistent with apoptosis
Abstract: There is persuasive epidemiological and experimental evidence that dietary polyphenolic plant-derived compounds have anticancer activity. Many laboratories, including ours, have reported such an effect in cancers of the gastrointestinal tract, lung, skin, prostate and breast. The catechins are a group of polyphenols found in green tea, which is one of the most commonly consumed beverages in the world. While the preponderance of the data strongly indicates significant antitumorigenic benefits from the green tea catechins, the potential molecular mechanisms involved remain obscure. We found that green tea components induce apoptosis via a TGF-beta superfamily protein, NAG-1 (Non-steroidal anti-inflammatory drug Activated Gene). In this report, we show that ECG is the strongest NAG-1 inducer among the tested catechins and that treatment of HCT-116 cells results in an increasing G(1) sub-population, and cleavage of poly (ADP-ribose) polymerase (PARP), consistent with apoptosis. In contrast, other catechins do not significantly induce NAG-1 expression, PARP cleavage or morphological changes at up to a 50-microM concentration. Furthermore, we provide evidence that ECG induces the ATF3 transcription factor, followed by NAG-1 induction at the transcriptional level in a p53-independent manner. The data generated by this study will help elucidate mechanisms of action for components in green tea and this information may lead to the design of more effective anticancer agents and informed clinical trials.
TL;DR: CYP1A1- and CYP1B1-catalyzed catechol estrogen formation might play a key role in TCDD-induced oxidative damage, and resveratrol can act as a potential chemopreventive against dioxin-induced human mammary carcinogenesis by blocking the metabolic formation of the catechols estrogens and scavenging the ROS generated during their redox cycling.
Abstract: Resveratrol (3,5,4'-trihydroxystilbene), a naturally occurring phytoalexin present in grapes and other foods, has been reported to possess chemopreventive effects as revealed by its striking inhibition of diverse cellular events associated with tumor initiation, promotion and progression In our present study, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), when treated with the cultured human mammary epithelial (MCF-10A) cells, induced the expression of cytochrome P450 1A1 (CYP1A1) and 1B1 (CYP1B1) that are responsible for the oxidation of 17beta-estradiol to produce catechol estrogens Resveratrol strongly inhibited the TCDD-induced aryl hydrocarbon receptor (AhR) DNA binding activity, the expression of CYP1A1 and CYP1B1 and their catalytic activities in MCF-10A cells It also reduced the formation of 2-hydroxyestradiol and 4-hydroxyestradiol from 17beta-estradiol by recombinant human CYP1A1 and CYP1B1, respectively Furthermore, resveratrol significantly attenuated the intracellular reactive oxygen species (ROS) formation and oxidative DNA damage as well as the cytotoxicity induced by the catechol estrogens Our data suggest that CYP1A1- and CYP1B1-catalyzed catechol estrogen formation might play a key role in TCDD-induced oxidative damage, and resveratrol can act as a potential chemopreventive against dioxin-induced human mammary carcinogenesis by blocking the metabolic formation of the catechol estrogens and scavenging the ROS generated during their redox cycling
TL;DR: It is suggested that sodium butyrate may be an effective sensitizer of TRAIL-induced apoptosis and may be related to the inhibition of deacetylases leading to hyperacetylation of chromatin components such as histones and non-histone proteins.
Abstract: Sodium butyrate, a short-chain fatty acid naturally present in the human colon, is able to induce cell cycle arrest, differentiation and apoptosis in various cancer cells. Sodium butyrate is most probably related to the inhibition of deacetylases leading to hyperacetylation of chromatin components such as histones and non-histone proteins and to alterations in gene expression. In this study, we demonstrate for the first time that sodium butyrate selectively up-regulated DR5 but had no effect on the expression of the other TNF-alpha-related apoptosis-inducing ligand (TRAIL) receptor, DR4. Sodium butyrate-induced expression of DR5 involves the putative Sp1 site within the DR5 promoter region. Using a combination of the electrophoretic mobility shift assay and the luciferase reporter assay, we found that a specific Sp1 site (located at -195 bp relative to the transcription start site) is required for sodium butyrate-mediated activation of the DR5 promoter. When HCT116 cells were incubated with sodium butyrate and TRAIL, enhanced TRAIL-mediated apoptosis was observed. The enhanced apoptosis was measured by fluorescent activated cell sorting analysis, DNA fragmentation, poly (ADP-ribose) polymerase cleavage, down-regulation of XIAP and caspase activity. Taken together, the present studies suggest that sodium butyrate may be an effective sensitizer of TRAIL-induced apoptosis.
TL;DR: The anti-proliferative effects on PC-3 of CLA mixture and their constituent isomers are not equivalent, due to the different pathways involved for individual isomers, while c9,t11 CLA isomer affects arachidonic acid metabolism.
Abstract: The aims of this study were to examine the anti-proliferative effects of different concentrations of a commercial preparation of conjugated linoleic acids (CLA) mixture of isomers [cis-9, trans-11 CLA (c9,t11 CLA): trans-10, cis-12 CLA (50:50)] and their constituent isomers on PC-3, a human prostatic carcinoma cell line, and to study their effects on gene expression (mRNA and protein levels) of different enzymes and oncoproteins involved in oncogenesis and progression of prostate cancer. This includes pathways for arachidonic acid metabolism [cyclooxygenase 1 (COX-1), 2 (COX-2) and 5-lipoxygenase (5-LOX)], apoptosis (bcl-2) and cell cycle control (p21 WAF/Cιp1 ). Our results indicate a significant decrease in PC-3 proliferation elicited by CLA, although with high variability between isomers. The trans-10, cis-12 CLA was the most effective isomer (55% inhibition). This isomer was also able to decrease bcl-2 gene expression and to increase p21 WAF1/Cip1 mRNA levels (60% increase at highest concentration). In contrast, cis-9, trans-11 had no effect on these proteins but had a clear effect on 5-LOX expression and to a lesser degree on COX-2 protein level isomers. In conclusion, the anti-proliferative effects on PC-3 of CLA mixture and their constituent isomers are not equivalent, due to the different pathways involved for individual isomers. Trans-10, cis-12 seems to work preferentially through modulation of apoptosis and cell cycle control, while c9,t11 CLA isomer affects arachidonic acid metabolism.
TL;DR: It is shown that RAGE is strongly reduced at the mRNA and even more so at the protein level in non-small cell lung carcinomas compared with normal lung tissues, and down-regulation of RAGE correlates with higher tumour (TNM) stages but does not depend on the histological subtypes, squamous Cell lung carcinoma and adenocarcinoma.
Abstract: The receptor for advanced glycation end-products (RAGE) is a transmembrane receptor of the immunoglobulin superfamily. Several ligands binding to RAGE have been identified, including amphoterin. Experimental studies have given rise to the discussion that RAGE and its interaction with amphoterin contribute to tumour growth and metastasis. However, none of the studies considered a differential transcription profile in cancer that might change the interpretation of the study results when comparing RAGE in tumours with histologically normal tissues. Here we show that RAGE is strongly reduced at the mRNA and even more so at the protein level in non-small cell lung carcinomas compared with normal lung tissues. Down-regulation of RAGE correlates with higher tumour (TNM) stages but does not depend on the histological subtypes, squamous cell lung carcinoma and adenocarcinoma. Subsequent overexpression of full-length human RAGE in lung cancer cells (NCI-H358) showed diminished tumour growth under some conditions. While proliferation of RAGE-expressing cells was less than that of cells expressing the cytoplasmic domain deletion mutant DeltacytoRAGE or mock-transfected NCI-H358 in monolayer cultures, RAGE cells also formed smaller tumours in spheroid cultures and in vivo in athymic mice compared with DeltacytoRAGE cells. Moreover, we observed a more epithelial growth of RAGE-expressing, but also of DeltacytoRAGE-expressing, cells on collagen layers, whereas mock NCI-H358 cells kept their tumour morphology. This observation was supported by immunofluorescence analyses demonstrating that RAGE preferentially localizes at intercellular contact sites, independent of expression of the cytoplasmic domain. Thus, down-regulation of RAGE may be considered as a critical step in tissue reorganization and the formation of lung tumours.
TL;DR: In this article, the association between single nucleotide polymorphisms (SNPs) in four genes (AKR1C3-Gln5His, NQO1-Pro187Ser, MnSOD-Val16Ala and OGG1-Ser326Cys) that play a role in the generation, prevention or repair of oxidative damage and lung cancer risk was examined.
Abstract: Lung cancer rates among men and particularly among women, almost all of whom are non-smokers, in Xuan Wei County, China are among the highest in China and have been causally associated with exposure to indoor smoky coal emissions that contain very high levels of polycyclic aromatic hydrocarbons (PAHs). As such, this population provides a unique opportunity to study the pathogenesis of PAH-induced lung cancer that is not substantially influenced by the large number of other carcinogenic constituents of tobacco smoke. Aldo-keto reductases (AKRs) activate PAH dihydrodiols to yield their corresponding reactive and redox-active o-quinones, which can then generate reactive oxygen species that cause oxidative DNA damage. We therefore examined the association between single nucleotide polymorphisms (SNPs) in four genes (AKR1C3-Gln5His, NQO1-Pro187Ser, MnSOD-Val16Ala and OGG1-Ser326Cys) that play a role in the generation, prevention or repair of oxidative damage and lung cancer risk in a population-based, case-control study of 119 cases and 113 controls in Xuan Wei, China. The AKR1C3-Gln/Gln genotype was associated with a 1.84-fold [95% confidence interval (CI) = 0.98-3.45] increased risk and the combined OGG1-Cys/Cys and Ser/Cys genotypes were associated with a 1.93-fold (95% CI = 1.12-3.34) increased risk of lung cancer. Subgroup analysis revealed that the effects were particularly elevated among women who had relatively high cumulative exposure to smoky coal. SNPs in MnSOD and NQO1 were not associated with lung cancer risk. These results suggest that SNPs in the oxidative stress related-genes AKR1C3 and OGG1 may play a role in the pathogenesis of lung cancer in this population, particularly among heavily exposed women. However, due to the small sample size, additional studies are needed to evaluate these associations within Xuan Wei and other populations with substantial exposure to PAHs.
TL;DR: The results of this study suggest that Ang-(1-7) inhibits lung cancer cell growth through the activation of an angiotensin peptide receptor and may represent a novel chemotherapeutic and chemopreventive treatment for lung cancer.
Abstract: Angiotensin-(1-7) [Ang-(1-7)] is an endogenous peptide hormone of the renin-angiotensin system with vasodilator and anti-proliferative properties. Human adenocarcinoma SK-LU-1 and A549 cells as well as non-small lung cancer SK-MES-1 cells were treated with serum in the presence and absence of Ang-(1-7), to determine whether Ang-(1-7) inhibits the growth of lung cancer cells. Ang-(1-7) caused a significant reduction in serum-stimulated growth in all three lung cancer cell lines. Treatment with Ang-(1-7) resulted in both a dose- and time-dependent reduction in serum-stimulated DNA synthesis in all three cell lines, with IC(50)'s in the sub-nanomolar range. The Ang-(1-7) receptor antagonist [D-Ala(7)]-Ang-(1-7) blocked the attenuation of the serum-stimulated DNA synthesis of SK-LU-1 cells by Ang-(1-7), while neither AT(1) nor AT(2) angiotensin receptor subtype antagonists prevented the response to the heptapeptide. MAS mRNA and protein, a receptor for Ang-(1-7), was detected in the three lung cancer cell lines, suggesting that the anti-proliferative effect of Ang-(1-7) in the cancer cells may be mediated by the non-AT(1), non-AT(2), AT((1-7)) receptor MAS. Other angiotensin peptides [Ang I, Ang II, Ang-(2-8), Ang-(3-8) and Ang-(3-7)] did not attenuate mitogen-stimulated DNA synthesis of SK-LU-1 cells, demonstrating that Ang-(1-7) selectively inhibits SK-LU-1 cancer cell growth. Pre-treatment of SK-LU-1 cells with 10 nM Ang-(1-7) reduced serum-stimulated phosphorylation of extracellular signal-regulated kinase (ERK)1 and ERK2, indicating that the anti-proliferative effects may occur, at least in part, through inhibition of the ERK signal transduction pathway. The results of this study suggest that Ang-(1-7) inhibits lung cancer cell growth through the activation of an angiotensin peptide receptor and may represent a novel chemotherapeutic and chemopreventive treatment for lung cancer.