Dennis P.H. Hsieh

Liquid chromatography/tandem mass spectrometric method for the simultaneous determination of tobacco-specific nitrosamine NNK and its five metabolites

A sensitive and robust high-performance liquid chromatography-electrospray ionization tandem mass spectrometry method to analyze 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its five metabolites in one passage was developed and validated. The method achieved excellent reproducibility and accuracy. Linearity was observed for all six compounds (R(2)=0.999) with detection limits (S/N> or =3) ranging from 0.2 to 2.4 pg on column and 0.01-0.12 ng ml(-1) in samples injected. Average intra-day and inter-day variations (% R.S.D.) were 1.2 and 3.5%, respectively. A sample preparation method involving C8 and C18 solid phase extraction provided satisfactory recovery of the analytes in mouse urine. Each NNK metabolite was identified by its chromatographic retention time and specific fragmentation pattern. Since the carcinogenicity of NNK is related to its metabolism, the method described in this report should facilitate toxicological investigations into the carcinogenesis due to NNK exposure in the environment.

Polycyclic aromatic hydrocarbons in cigarette sidestream smoke particulates from a Taiwanese brand and their carcinogenic relevance

Polycyclic aromatic hydrocarbons (PAHs) adsorbed on cigarette sidestream smoke particulates (CSSPs) have been regarded as important contributors to lung carcinogenesis in never smokers. However, limited information is available on PAH levels in cigarette sidestream smoke. Here we determine the concentrations of 22 PAHs, including 16 US EPA priority PAHs, in CSSPs generated from a high market-share domestic brand in Taiwan. Five of the 22 PAHs are undetectable. The remaining 17 PAHs constitute about 0.022% of the total mass of CSSPs. Near one fifth of the PAH mass come from IARC group 1 and group 2 carcinogens. Carcinogenic potency is equivalent to 144 ng benzo[a]pyrene per cigarette converted according to potency equivalency factors (PEFs). The CSSP condensate could activate AhR activity and induce AhR target gene expression. High concentrations of CSSPs also exhibited AhR-independent cytotoxicity. However, mixing the 17 PAHs as the composition in the CSSP condensate could not reconstitute either capacity. Since AhR activation and cytotoxicity are important mechanisms underlying carcinogenic potency, the results suggest that other component compounds play a more active role in carcinogenesis. The approach of individual PAH profiling plus PEF conversion commonly used in risk assessment is likely to underestimate the risk caused by environmental cigarette smoke exposure.

ERα phenotype, estrogen level, and benzo[a]pyrene exposure modulate tumor growth and metabolism of lung adenocarcinoma cells.

Women have a higher risk of lung adenocarcinoma than men, suggesting that estrogen pathway may be involved in the pathogenesis of this cancer. This study was designed to determine whether ERα expression, estrogen levels, and endocrine disruptor exposure would influence tumor growth of lung adenocarcinoma cells using a xenograft model in which human lung adenocarcinoma cells with and without transgenic ERα expression were transplanted into female nude mice. Results showed that estrogen promoted tumor growth of ERα(+) lung adenocarcinoma cells but inhibited that of ERα(-) lung adenocarcinoma cells. Endocrine disruptor benzo[a]pyrene stimulated ERα(-) tumor growth dose dependently. Either of ovariectomy and ERα expression abolished the tumor growth-promoting effect of benzo[a]pyrene. The high CYP1B1/CYP1A1 and low COMT/CYP1B1 expression ratios detected in ERα(+) tumors suggested an accumulation of 4-hydroxyestradiol metabolite under high body estrogen, whereas comparable CYP1A1 and CYP1B1 expression plus estrogen-inducible COMT expression might favor the formation of 2-methoxyestradiol in ERα(-) tumors. Inhibition of estrogen on ERα(-) tumor growth might be partly attributable to the anti-proliferative action of 2-methoxyestradiol. Benzo[a]pyrene increased expression of CYP1B1 over CYP1A1 and suppressed estrogen-induced COMT up-regulation in ERα(-) tumor cells, probably switching estrogen metabolism to 4-hydroxyestradiol formation and removing the inhibition of 2-methoxyestradiol on ERα(-) tumors. ERα inhibited AhR from up-regulating CYP1 in response to benzo[a]pyrene exposure, but it increased angiogenic VEGF-A expression with body estrogen levels. Estrogen might increase ERα(+) lung adenocarcinoma growth by up-regulating cancer-related ERα target gene expression.

Correlation between the Urine Profile of 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone Metabolites and N7-Methylguanine in Urothelial Carcinoma Patients

A major carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), is present in cigarette smoke and its metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), is used as an exposure biomarker for environmental tobacco smoke (ETS). This metabolite (NNAL) can be either detoxified into glucuronidated NNAL (NNAL-Gluc) or activated into an unstable reactive metabolite that methylates DNA along with formation of 4-hydroxy-4-(3-pyridyl)-butyric acid [hydroxy acid (HA)]. Therefore, the carcinogenic risk associated with ETS exposure is greatly modulated by individual variations in metabolic activation and detoxification capabilities. In this study, we defined the urinary HA/total NNAL [HA/total NNAL] ratio as the activation index and NNAL-Gluc/free NNAL [(total NNAL-free NNAL)/free NNAL] ratio as the detoxification index of NNK. The major methylated DNA adduct N7-methylguanine (N7-MeG), considered as the carcinogenic biomarker for cigarette smoking, was excreted in urine. The objective of this study was to investigate the effects of these metabolic indexes of NNK on N7-MeG urinary excretion in a population of urothelial carcinoma patients. Urinary levels of total NNAL (free NNAL plus NNAL-Gluc), free NNAL, HA, and N7-MeG were positively correlated with smoking. Furthermore, activation index and detoxification index correlated positively and negatively with N7-MeG levels, respectively. Our results suggest that these metabolic indices may represent the phenotype of individual metabolism capability and modulate the carcinogenic risk of ETS exposure. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3390–5)

A GIS-Aided Assessment of the Health Hazards of Cadmium in Farm Soils in Central Taiwan

A geostatistical method was developed to examine the correlation, or lack of it, between the levels of cadmium (Cd) detected in farm soils and those detected in the human specimens collected from residents around the contaminated areas in Changhua County where cadmium contamination of staple rice has been documented. We used the Taiwan EPA environment data in 2002 and human data which were generated by the National Health Research Institutes during 2003–2005. Kriging interpolation methods were used to determine soil Cd concentrations. A Zonal statistical function was performed to assess the individual exposure. Soil Cd levels and tissue Cd levels in residents were analyzed for contamination hotspots and other areas to determine correlation between the two variables. Three Cd contamination hotspots were identified, in which no correlation was found between soil Cd levels and tissue Cd levels in residents. Our results demonstrate how GIS spatial modeling technique can be used to estimate distribution of pollutants in an area using a limited number of data points. Results indicated no association between the soil contamination and the exposure of residents to Cd, suggesting that both the soils and the residents are receptors of Cd as a pollutant from as yet unidentified sources.

Spatial interpolation of cadmium contamination of agricultural soils in Changhua County, Taiwan

A robust spatial model to interpolate topsoil cadmium concentrations monitored by Taiwan EPA was constructed for assessment of health risks posed by this contamination in Changhua County, Taiwan. kriging methods, using a Geographic Information Systems (GIS), were used to estimate the range and severity of topsoil contamination. Optimised Kriging models and geostatistical analyses revealed that much of the farm topsoil in the catchment area was polluted above the levels established for human health. Cadmium hotspots (10-600 mg/kg) are identified in a highly populated region in the County.