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ABSTRACT: 8-Hydroxy-2'-deoxyguanosine (8-OH-dG) is 1 of the most abundant oxidative products of cellular DNA. Accumulation of impaired 8-OH-dG could lead to increased genomic instability that in turn could lead to a more malignant phenotypic behavior of tumors. Therefore, the effects of 8-OH-dG on survival in 99 resected nonsmall-cell lung cancer (NSCLC) patients was evaluated.
The enzyme-linked immunosorbent assay was applied to measure the levels of 8-OH-dG in tumor DNA. The median levels of 8-OH-dG were 6.5 pmol/microg for all study subjects.
Patients with low levels of 8-OH-dG had significantly longer survival times compared with those with high levels of 8-OH-dG (log-rank test: P < .001). In Cox regression analysis, patients with high levels of 8-OH-dG had an over 3-fold increased hazard of death. In addition, a statistically significant correlation between levels of 8-OH-dG and age was noted (rho = 0.206, P = .048). Furthermore, we observed a genotype-phenotype modification between hOGG1 gene polymorphism (Ser326Cys) and levels of 8-OH-dG.
The results demonstrated that levels of 8-OH-dG could predict survival in resected NSCLC patients. It is postulated that an intact base excision repair mechanism may reduce the accumulation of oxidative DNA damage that is thought to contribute to the tumor's malignant potential and therefore the risk of death.
Cancer 02/2007; 109(3):574-80. · 4.77 Impact Factor
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ABSTRACT: Apurinic/apyrimidinic (AP or abasic) sites are common DNA lesions that arise from spontaneous depurination or by base excision repair (BER) of modified bases. Accumulation of impaired AP sites could lead to increased genomic instability that in turn could lead to a more malignant phenotypic behavior of tumors. We, therefore, evaluated the effects of AP sites on survival in resected non-small cell lung cancer (NSCLC) patients. Resected tumor specimens from 99 patients with NSCLC who underwent surgical resection were collected. The enzyme-linked immunosorbent assay was applied to measure the levels of AP sites in tumor DNA. The median number of AP sites per 10(5) nucleotides was 12.4 for all the study subjects. Patients with low levels of AP site had significantly longer survival time compared with ones with medium or high levels of AP site (log-rank test: P=0.015). In Cox regression analysis, patients with medium or high levels of AP sites had over twofold increased hazard of death. In addition, we found a statistically significant correlation between levels of AP sites and age (rho=0.560, P<0.001). The results of this study demonstrated that levels of AP sites could predict survival in resected NSCLC patients. We postulate that an intact BER mechanism may reduce the accumulation of oxidative DNA damage that are thought to contribute to the tumor's malignant potential and therefore the risk of death.
Cancer Letters 02/2007; 246(1-2):47-53. · 4.24 Impact Factor
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ABSTRACT: TP53 mutations are common in lung cancers of smokers, with high prevalence of G:C-to-T:A transversions generally interpreted as mutagen fingerprints of tobacco smoke. In this study, TP53 (exons 5-9) and KRAS (codon 12) were analyzed in primary lung tumors of never (n = 40), former (n = 27), and current smokers (n = 64; mainly heavy smokers). Expression of p53, cyclooxygenase-2 (Cox-2), and nitrotyrosine (N-Tyr), a marker of protein damage by nitric oxide, were analyzed by immunohistochemistry. TP53 mutations were detected in 47.5% never, 55.6% former, and 77.4% current smokers. The relative risk for mutation increased with tobacco consumption (P(linear trend) < 0.0001). G:C-to-T:A transversions (P = 0.06, current versus never smokers) and A:T-to-G:C transitions (P = 0.03, former versus never smokers) were consistently associated with smoking. In contrast, G:C-to-A:T transitions were associated with never smoking (P = 0.02). About half of mutations in current smokers fell within a particular domain of p53 protein, suggesting a common structural effect. KRAS mutations, detected in 20 of 131 (15.3%) cases, were rare in squamous cell carcinoma compared with adenocarcinoma [relative risk (RR), 0.2; 95% confidence interval (95% CI), 0.07-1] and were more frequent in former smokers than in other categories. No significant differences in Cox-2 expression were found between ever and never smokers. However, high levels of N-Tyr were more common in never than ever smokers (RR, 10; 95% CI, 1.6-50). These results support the notion that lung tumorigenesis proceeds through different molecular mechanisms according to smoking status. In never smokers, accumulation of N-Tyr suggests an etiology involving severe inflammation.
Cancer Research 07/2005; 65(12):5076-83. · 7.86 Impact Factor
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ABSTRACT: Renal cell carcinoma (RCC) accounts for 3% of adult deaths from cancer. The risk factors for its development are still under intense investigation. Although tobacco smoke is a risk factor, the data are inconsistent and the extent of the increased risk is unclear. Estimates from 19 case-control and 5 cohort studies were used. The case-control reports included 8,032 cases and 13,800 controls; the cohort estimates were based on 1,457,754 participants with 1,326 cases of RCC. The relative risk (RR) for RCC for ever smokers as compared to lifetime never smokers was 1.38 (95% confidence interval [CI] = 1.27-1.50). The RR for male smokers was 1.54 (95% CI = 1.42-1.68) and for female smokers was 1.22 (95% CI = 1.09-1.36). For men and women there was a strong dose-dependent increase in risk. Ever smoker men who had smoked 1-9, 10-20 or 21 or more cigarettes/day had a RR of 1.60 (95% CI = 1.21-2.12), 1.83 (95% CI = 1.30-2.57), or 2.03 (95% CI = 1.51-2.74), respectively. For women, the relative risks were 0.98 (95% CI = 0.71-1.35), 1.38 (95% CI = 0.90-2.11), or 1.58 (95% CI = 1.14-2.20), respectively. The advantages of smoking cessation were confirmed by a reduction in RR for those who had quit smoking for >10 years as compared to those who had quit for 1-10 years. Inhaled tobacco smoke is clearly implicated in the etiology of RCC, with a strong dose-dependent increase in risk associated with numbers of cigarettes smoked per day and a substantial reduction in risk for long-term former smokers.
International Journal of Cancer 03/2005; 114(1):101-8. · 5.44 Impact Factor
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ABSTRACT: Tumor-induced angiogenic responses lead to complex phenotypic changes in vascular endothelial cells, which must coordinate the expression of both proteases and protease inhibitors prior to the proliferation and invasion of surrounding stroma. Matrix metalloproteinase 2 (MMP2), which degrades Type IV collagen, is produced as proMMP2. proMMP2 is activated in part through its interactions with membrane Type 1 MMP (MT1-MMP) and tissue inhibitor of matrix metalloproteinase 2 (TIMP2). In this study, we demonstrate that platelet-activating factor (PAF) is a potent inducer of human umbilical vein endothelial cell (HUVEC) migration and invasion, which is attenuated by PAF receptor antagonists, and that PAF receptor antagonists inhibit the migration and invasion of HUVEC mediated by medium conditioned by a prostatic carcinoma cell line. We confirm that PAF receptor antagonists inhibit proliferation of HUVEC grown in rich growth medium. We show that PAF increases mRNA levels for MT1-MMP and TIMP2, followed by increased temporal conversion of latent proMMP2 to MMP2. Finally, we demonstrate that the ratio of MT1-MMP to TIMP2 in membrane preparations from PAF-stimulated HUVEC is 1.6:1, approximating the hypothesized ideal ratio of 2:1 necessary for the conversion of proMMP2 to MMP2. Our data support the involvement of PAF in vascular endothelial cell migration and invasion.
The FASEB Journal 04/2004; 18(3):568-70. · 5.71 Impact Factor
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ABSTRACT: Platelet-activating factor (PAF), a phospholipid second messenger, has diverse physiological functions, including responses in differentiated endothelial cells to external stimuli. We used human umbilical vein endothelial cells (HUVECs) as a model system. We show that PAF activated pertussis toxin-insensitive G alpha(q) protein upon binding to its seven transmembrane receptor. Elevated cAMP levels were observed via activation of adenylate cyclase, which activated protein kinase A (PKA) and was attenuated by a PAF receptor antagonist, blocking downstream activity. Phosphorylation of Src by PAF required G alpha(q) protein and adenylate cyclase activation; there was an absolute requirement of PKA for PAF-induced Src phosphorylation. Immediate (1 min) PAF-induced STAT-3 phosphorylation required the activation of G alpha(q) protein, adenylate cyclase, and PKA, and was independent of these intermediates at delayed (30 min) and prolonged (60 min) PAF exposure. PAF activated PLC beta 3 through its G alpha(q) protein-coupled receptor, whereas activation of phospholipase C gamma 1 (PLC gamma 1) by PAF was independent of G proteins but required the involvement of Src at prolonged PAF exposure (60 min). We demonstrate for the first time in vascular endothelial cells: (i) the involvement of signaling intermediates in the PAF-PAF receptor system in the induction of TIMP2 and MT1-MMP expression, resulting in the coordinated proteolytic activation of MMP2, and (ii) a receptor-mediated signal transduction cascade for the tyrosine phosphorylation of FAK by PAF. PAF exposure induced binding of p130(Cas), Src, SHC, and paxillin to FAK. Clearly, PAF-mediated signaling in differentiated endothelial cells is critical to endothelial cell functions, including cell migration and proteolytic activation of MMP2.
Journal of Biological Chemistry 02/2004; 279(5):3497-508. · 4.77 Impact Factor
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ABSTRACT: Elevated mortality rates of lung cancer in the Mississippi River corridor in Louisiana have been clearly documented for the past half-century and rank among the highest in the nation. A population-based case-control study of lung cancer termed Lower Mississippi River Interagency Cancer Study was conducted in southern Louisiana. Lung tumor specimens were collected, isolated by laser capture microdissection, subjected to PCR to amplify KRAS, and sequenced to confirm mutation status and specificity. Of the 116 lung tumors analyzed to date, 32 (27.6%) contained mutations in either codon 12 or 13 of KRAS. This frequency is comparable to that reported in the literature; however, the mutation spectrum was strikingly different. Of the 32 mutations observed, 21 (65.6%) resulted in the inappropriate insertion of cysteine, 6 (18.8%) resulted in the insertion of serine, 3 (9.4%) resulted in the insertion of valine, and 1 (3.1%) each resulted in the insertion of aspartate and alanine. These data indicate that an abnormally high proportion of cysteine (P = 0.010) and serine (P = 0.002) mutations was observed in our sample group versus lung cancers reported in the literature. KRAS mutations were more common in African Americans with an odds ratio of 2.4 (P = 0.048), as were serine mutations, although the latter did not reach statistical significance (odds ratio, 2.6; P = 0.373). No association was found between the observed mutation spectrum and known lung cancer risk factors.
Cancer Epidemiology Biomarkers & Prevention 12/2002; 11(11):1405-12. · 4.12 Impact Factor
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ABSTRACT: Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with multiple pathological and physiological effects. We have shown that basic fibroblast growth factor (bFGF) supplementation induces rapid proliferation of human umbilical vein endothelial cells (HUVEC), which is reduced upon removal of bFGF or by bFGF immunoneutralization. The PAF receptor antagonist LAU-8080 inhibited bFGF-stimulated HUVEC proliferation, indicating the involvement of PAF in the bFGF-mediated signaling of HUVEC. Although FGF receptor phosphorylation was not affected by LAU-8080, the bFGF-mediated prolonged phosphorylation, and activation of Erk-1 and -2 were attenuated. Phosphorylation of STAT-3 was observed in the presence of PAF or bFGF, which was attenuated by PAFR antagonists. PAF-induced STAT-3 phosphorylation observed in HUVEC pretreated with either Src inhibitor PP1 or JAK-2 inhibitor AG-490 indicated (i) immediate (1 min) phosphorylation of STAT-3 is dependent on Src, (ii) JAK-2-dependent STAT-3 phosphorylation occurs after the delayed (30 min) PAF exposure, and (iii) prolonged (60 min) STAT-3 phosphorylation may be either through Src and/or JAK-2. Attenuation of the STAT-3 phosphorylation by the PAFR antagonists indicated signaling through the PAF receptor. Taken together, these findings suggest the production of PAF is important for bFGF-mediated signaling and that a dual kinase mechanism is involved in the PAF-mediated signal transduction cascade.
Journal of Biological Chemistry 07/2002; 277(24):21237-45. · 4.77 Impact Factor
