Characterization of a bifunctional and endolytic alginate lyase from Microbulbifer sp. ALW1 and its application in alginate oligosaccharides production from Laminaria japonica.

The diverse biological activities of alginate oligosaccharides attracted extensive exploration of alginate lyases with various substrate specificity and enzymatic properties. In this study, an alginate lyase from Microbulbifer sp. ALW1, namely AlgL7, was phylogenetically classified into the polysaccharide lyase family 7 (PL7). The conserved amino acid residues Tyr606 and His499 in AlgL7 were predicted to act as the general acid/base catalysts. The enzyme was enzymatically characterized after heterologous expression and purification in E. coli. AlgL7 displayed optimal activity at 40 °C and pH 7.0. It had good stability at temperature below 35 °C and within a pH range of 5.0-10.0. AlgL7 exhibited good stability against the reducing reagent ß-ME and the surfactants of Tween-20 and Triton X-100. The degradation profiles of alginate indicated AlgL7 was a bifunctional endolytic alginate lyase generating alginate oligosaccharides with the degrees of polymerization 2-4. The degradation products of sodium alginate exhibited stronger antioxidant activities than the untreated polysaccharide. In addition, AlgL7 could directly digest Laminaria japonica to produce alginate oligosaccharides. These characteristics of AlgL7 offer a great potential of its application in high-value utilization of brown algae resources.

[Analysis of sensitivity and specificity of sputum cytology screening for lung cancer with different positive criteria].

OBJECTIVE: To discuss the effect of different positive criteria on the sensitivity and specificity of sputum cytology screening for lung cancer among Yunnan tin miners. METHODS: 9223 Yunnan tin miners who received at least one annual sputum cytology screening for lung cancer during the period between 1992 and 1999 were recruited in the study. At time of enrollment, all participants were aged over 40 years old, had at least 10 years of employment as an underground miner and(or) smelter, and had not been diagnosed with malignancy. In our study, a true positive was categorized as having at least one prior positive sputum screening and a diagnosis of lung cancer, while a true negative, by our definition, signified negative sputum examinations and no diagnosis of lung cancer during the follow up time. Based on different positive criteria, sensitivity and specificity of sputum cytology were computed and receiver operating characteristic (ROC) curve analysis was conducted. Z statistic was used to test the differences of the area under ROC based on Hanley and McNeil method. RESULTS: By the end of following up on December 31, 2001, a total 500 lung cancer cases were diagnosed among 9223 participants: most were squamous cell carcinoma (55.8% (222/398)) and central lung cancers (68.5% (316/461)). 150 lung cancer cases had a previous positive sputum screening result. When positive criteria were taken as grave atypical metaplasia, moderate atypical metaplasia and slight atypical metaplasia, the corresponding sensitivities were 30.0% (150/500), 36.4% (182/500), 53.0% (265/500) respectively; while the corresponding specificities were 98.9% (8628/8723), 95.1% (8611/8723), 77.9% (7033/8723) respectively. The areas under ROC curve according to different positive criterias were 0.645 (95%CI: 0.635 - 0.654), 0.657 (95%CI: 0.668 - 0.667), 0.655 (95%CI: 0.645 - 0.664) respectively. There were no significant differences found in the comparisons between grave and moderate atypical metaplasia, grave and slight atypical metaplasia, moderate and slight atypical metaplasia(Z statistics were 0.780, 0.645, 0.209 respectively, all P values > 0.05). CONCLUSION: While the standard of positive criteria for diagnosis of lung cancer decreased, the sensitivity of sputum cytology screening increased and the specificity decreased. Since there were no significant differences of accuracy for different positive criteria.

[An epidemiological study of the neoplasm mortality in Gejiu residents from 1996 to 2005].

OBJECTIVE: To assessment the trend of the mortality of the neoplasm among the residents in Gejiu city of Yunnan province and to provide scientific evidences for the neoplasm prevention. METHODS: Data of mortality of the neoplasm from 1996 to 2005 was collected and analyzed through a retrospective survey. RESULTS: The mortality was going up in the recent epidemiological surveys. The increase trend was showed on the mortality from 1996 to 2005. The mortality was 53.25 per 100,000 of 1996 increased to 70.58 per 100,000 in 2005. The mortality in female was 23.76 per 100,000 in 1996 increased to 50.57 per 100,000 of 2005. CONCLUSION: The neoplasm is still a leading disease in Gejiu city. The main cancer was lung cancer in the neoplasms. The mortality of the neoplasma in the town residents was higher than the countryside. It is necessary to enhance neoplasm prevention.

[Retrospective analysis of screening results of lung cancer cases among occupational population at high risk of lung cancer].

BACKGROUND: Lung cancer has become the leading cause of the cancer death in China. Population-based lung cancer screening is still in controversy. The objective of this study is to analyze the effect of annual chest radiography and sputum cytological screening conducted in high lung cancer risk population who were exposed to work related carcinogens. METHODS: A retrospective analysis was conducted to evaluate the screening results of the lung cancer cases diagnosed from 1992 to 2001 in the miners of Yunnan tin mine. RESULTS: A total of 9317 miners had been screened annually from 1992 to 1999. A total of 46 779 chest radiography and 45 672 sputum cytological examinations had been conducted, and 793 cohort subjects had at least one positive result. The annual positive detection rate ranged from 1214.1/100 000 to 3482.7/100 000. By December 31, 2001, 433 lung cancer cases had been confirmed, 371 cases out of them had cytological/pathological evidence, and 55.0% were squamous cell carcinoma followed by adenocarcinoma and small cell carcinoma. Stage I or II accounted for 24%. 62.1% of the cases had at least one positive screening result, while 165 cases were detected by chest radiography alone, 56 were detected by sputum cytology, and 48 were detected by both screening modalities. 64.2% of X-ray detected cases were squamous/adenous carcinomas and 75.0% of cytological detected cases were squamous carcinoma. 80.8% of early stage cases had at least one previous positive finding from screening. CONCLUSIONS: Annual lung cancer screening with combination of chest radiography and sputum cytology play some extent role in early detection of lung cancer in high risk population. The results may provide some primary data for lung cancer screening in special population who are at high risk of lung cancer in China.

Modification of association between prior lung disease and lung cancer by inhaled arsenic: A prospective occupational-based cohort study in Yunnan, China.

Arsenic and prior lung diseases have been shown to increase lung cancer risk; however, little is known about their joint effects. The aim of our study was to analyze the joint effects of inhaled arsenic and prior lung diseases on lung cancer risk within a occupational cohort. The interactions of prior lung diseases and inhaled arsenic were analyzed based on multiplicative and additive scales in the Cox proportional hazards model. Compared with low arsenic exposure and no history of asthma, the hazard ratios (HRs) of high arsenic exposure with asthma, high arsenic exposure without asthma and low arsenic exposure with asthma were 2.61 (95% CI: 1.71-4.00), 2.60 (95% CI: 1.93-3.51) and 2.49 (95% CI: 1.53-4.06), respectively. Based on the multiplicative scale in the Cox proportional hazards model, the HR of the interaction of asthma and arsenic on lung cancer risk was 0.45 (95% CI: 0.25-0.80). Based on the additive scale, the relative excess risk due to interaction between asthma and arsenic was -1.41 (95% CI: -2.81 to -0.02). Our study provides strong evidence that arsenic exposure is associated with lung cancer risk. A significant negative interaction between asthma and arsenic on lung cancer risk is observed.

Gene-environment interactions between the codon 194 polymorphism of XRCC1 and antioxidants influence lung cancer risk.

X-ray repair cross complementing group 1 (XRCC1) is a DNA repair gene whose polymorphisms appear to influence the risk of lung cancer. We explored the influence of antioxidants on the association between the codon 194 arganine to tryptophan substitution polymorphism of XRCC1 and lung cancer risk. In a case-control study nested within a cohort of tin miners the cases were those diagnosed with lung cancer over 6 years of follow-up (n = 108). Two controls, matched on age and sex, were selected for each case by incidence density sampling. Individuals with the variant Arg194Trp allele seemed to be at lower risk for lung cancer (odds ratio (OR): 0.7, 95% confidence interval (95%CL): 0.4-1.2). Furthermore, high serum alpha-tocopherol (OR: 0.4, 95%CL: 0.2-0.9) and retinol (OR: 0.4, 95%CL: 0.2-0.9) levels were associated with significantly reduced risk of lung cancer among individuals with the Arg194Trp variant allele, but not among individuals with the wild-type genotype. In addition, the Arg194Trp variant reduced the risk of lung cancer associated with increased serum carotenoids compared to those with the homozygous wild-type allele. Our results show that Arg194Trp XRCC1 variant modifies the association between serum antioxidants and lung cancer risk.

Effects of fat-soluble extracts from vegetable powder and beta-carotene on proliferation and apoptosis of lung cancer cell YTMLC-90.

OBJECTIVE: The aim of this investigation was to study the effects of fat-soluble extracts from vegetable powder (FEFVP) and beta-carotene on the proliferation and apoptosis of cultured YTMLC-90 lung cancer cells. METHODS: The lung cancer cells were continuously exposed to a broad range of concentration of FEFVP and beta-carotene. The proliferation was evaluated in MTT test. The induction of apoptosis was evaluated by morphological change, DNA fragmentation analysis, and DNA content analysis combined with flow cytometric analysis. RESULTS: Both FEFVP and beta-carotene were found to inhibit cell proliferation and to induce morphologic changes consistent with apoptosis in YTMLC-90 cancer cells, including cellular shrinkage, chromatin condensation and nuclear fragmentation. DNA agarose gel electrophoresis showed DNA fragmentation 'ladder'. Flow cytometric analysis revealed decreased DNA content and the presence of a sub-G1 apoptotic peak. CONCLUSION: These findings are consistent with the induction of apoptosis. Moreover, the effects of FEFVP are stronger than those of beta-carotene. FEFVP inhibits the growth of YTMLC-90 probably via the induction of apoptosis cancer cells.

[Nested case-control study on riboflavin levels in blood and urine and the risk of lung cancer].

The present study is designed to explore the relationship between the riboflavin levels in blood and urine and the risk of lung cancer among miners in Yunnan Tin Corporation(YTC) by means of nested case-control design. Cases were patients with lung cancer newly diagnosed from 1992 to 1995. For each case, 2 controls were randomly matched with occupational exposure history, age, the time of collecting blood or urine samples. The indexes for evaluating the riboflavin nutritional status were erythrocyte glutathione reductase activation coefficient (EGR-AC) and the ratio of riboflavin and creatinine in urine. When analyzed as either the continuous or the rank variables, the odds ratios(ORs) used to estimate the relative risk of lung cancer have no statistical significance(P > 0.05) after adjusting the confusing factors. No association of riboflavin indexes in blood and urine with the lung cancer risk among YTC miners were observed in the present study.

[Establishment of cohort to study lung cancer in Yunnan tin miners].

BACKGROUND: To establish a cohort for the study of risk factors of lung cancer, and to support the study of early biomarkers and prevention of lung cancer. METHODS: Designed a special population-based prospectively dynamic cohort among radon- and arsenic-exposed tin miners aged 40 or more years old with at least 10 years of occupational exposure in Yunnan Province, P.R.China. The mass screenings with sputum cytology and chest X-ray were conducted annually. The baseline information was collected for assessing demographic characteristics and risk factors. The multiple sputum specimens, chest radiographs and numerous biologic specimens have been collected and stored. RESULTS: From 1992-1999, 9143 miners have been enrolled and 460 new cases of lung cancer have been found. There had 47655 person-time chest radiographs and 46625 person-time sputum cytology among the cohort in 8 years. The relative risks of age-adjusted exposure to chronic bronchitis, silicosis, and tobacco were 1.73, 1.46, and 1.32 respectively. CONCLUSIONS: A cohort of unique occupationally-exposed tin miners with an extensive biologic specimen repository and data bank has been successfully established. Although occupational exposures are the predominant risk factors among the high risk miners, lung cancer risk is also associated with chronic obstructive lung disease (chronic bronchitis and silicosis) and a number of measures of exposure to tobacco smoke, including early age of first use, duration, and cumulative exposure.

[A cohort study on risk factors of lung cancer in Yunnan tin miners].

BACKGROUND: Smoking is a major cause of lung cancer. Studies of lung cancer among miners have shown that occupational exposure also played an important role. The aim of this study is to investigate radon, cigarette use and other risk factors of lung cancer in Yunnan tin miners and to provide a scientific basis for the prevention and control of occupational lung cancer. METHODS: A prospective cohort study was conducted among Yunnan tin miners, the associations between potential risk factors for lung cancer were analyzed by multivariate Cox regression model. Effects of age at first radon exposure and radon exposure rate on lung cancer risk were analyzed. The relationship between cumulative working level month and lung cancer was analyzed according to smoking status. The joint effect of tobacco use and cumulative radon exposure was analyzed based on additive and multiplicative models. RESULTS: Increased risk of lung cancer was associated with age at enrollment, tobacco use, prior bronchitis, and cumulative arsenic and radon exposure, while higher education level was associated with decreased lung cancer risk. An inverse effect of radon exposure rate was observed. There was no significant association between lung cancer risk and first radon exposure age. There was a significant additive interaction between tobacco use and radon exposure on lung cancer risk. CONCLUSIONS: Several risk factors may contribute to the high incidence of lung cancer in Yunnan tin miners. Further studies are warranted to evaluate joint effect of different risk factors.

Prior lung disease and lung cancer risk in an occupational-based cohort in Yunnan, China.

We used the data from a prospective cohort study among tin miners in Yunnan, China to investigate whether prior lung disease is a risk factor for lung cancer. Information on prior lung disease was obtained from baseline questionnaires. The Cox proportional hazards model was used to examine the relationship between prior lung disease and lung cancer risk. From 1992 to 2001, a total of 502 lung cancer cases were confirmed among 9295 cohort participants. Prior chronic bronchitis was associated with an increase in lung cancer risk with an adjusted HR of 1.50 (95% CI: 1.24-1.81). There was an increased risk of developing squamous cell carcinoma in the setting of prior chronic bronchitis and small cell carcinoma in association with asthma with an adjusted HRs of 1.57 (95% CI: 1.19-2.09) and 2.56 (95% CI: 1.38-4.75), respectively. This prospective study provides further evidence that prior chronic bronchitis correlates with increased lung cancer risk, especially for squamous cell carcinoma. Asthma is associated with increased risk of small cell lung carcinoma.

Association between sputum atypia and lung cancer risk in an occupational cohort in Yunnan, China.

BACKGROUND: Individuals with cytologic atypia in sputum may be at high risk for the development of lung cancer. METHODS: A prospective cohort study was conducted among occupational tin miners in Yunnan, China, based on an annual lung cancer screening program. Sputum samples were collected prospectively at baseline and the following seven annual screenings. The associations between risk factors and sputum cytology were analyzed by univariate and multivariate logistic regression. A proportional hazard model was used to analyze the association between the baseline sputum results and the incidence of lung cancer. The effect of consecutive sputum cytology on the increase of lung cancer risk was analyzed by logistic regression. RESULTS: Sputum cytologic atypia was associated with age, smoking, occupational radon and arsenic exposure, and asthma. Sputum cytologic atypia was an independent risk factor for lung cancer with an adjusted hazard ratio (HR) of 3.82 (95% confidence interval [CI], 2.82 to 5.18) in comparing normal to moderate or worse atypia. Compared to the lung cancer risk associated with normal sputum, the risk was significantly higher according to the degree of atypia for squamous carcinomas, small cell lung cancer and central lung cancer, with adjusted HRs of 5.70 (95% CI, 3.78 to 8.59), 3.32 (95% CI, 1.31 to 8.45), and 4.93 (95% CI, 3.51 to 6.92), respectively. CONCLUSIONS: Sputum atypia is associated with an increased risk of lung cancer. Sputum cytologic examination combined with other screening examinations may play an important role in the early detection of lung cancer or in the selection of the optimal target population for more intensive lung cancer screening among this occupational cohort or similar population.