The aromatic hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates many of the biological and toxicological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related chemicals. Here we developed a novel method to detect the presence of AhR ligands using Exonuclease Protection Mediated PCR bioassay (EPM-PCR). This assay measures the ability of a chemical to activate AhR DNA binding in vitro. In the presence of AhR ligand, an expected length PCR product was observed on electrophoresis, but no signal was detected in the absence of ligand. Real-time quantitative PCR was performed to quantifyDNA bound to ligand:AhR complex. We obtained a standard curve with TCDD concentration to bound DNA copies in the range of 0.01pM-10nM of TCDD. Minimal detection limit of the assay was below 0.01pM TCDD, and the whole detection time was less than 5h. In comparison to the chemical-activated luciferase gene expression (CALUX) bioassay, EPM-PCR bioassay is more sensitive and easier to perform. These results suggest that this assay is useful for detection and quantification of TCDD and related AhR ligands in a cell-free system without the use of radioactivity.

Polymorphisms of the nucleotide excision repair gene XPD are candidates for influencing cancer susceptibility. To determine the effect of XPD genetic polymorphisms on the risk of esophageal squamous cell carcinoma (ESCC) and its interaction with carcinogen exposure, XPD polymorphisms at codon 312 (Asp→Asn) and codon 751 (Lys→Gln) were determined in 135 ESCC patients and 152 normal controls. Polymorphism at codon 312 made no contribution to genetic risk for ESCC. Our results showed that there was a significant difference between frequencies for XPD 751 Gln/Gln genotype in ESCC patients (8.9%) and normal cases (1.3%), and that Gln/Gln genotype was associated with an increased risk of ESCC (odds ratio [OR]=6.71; 95% confidence interval [CI]: 1.90-23.73). The results of the logistic regression model showed that XPD 751 Gln/Gln genotype and drinking were candidates for influencing the risk of ESCC. Among smokers, the risk of ESCC in XPD 751 Gln/Gln genotype increased 8-fold than that XPD 751 Lys/Lys genotype (OR=8.42, 95% CI: 1.02-69.58). The results indicated that XPD 751 Gln/Gln genotype may be contributing factors in the risk of ESCC and may modify risk attributable to environmental exposures.

Background: The purpose of the present paper was to study the expression of cyclooxygenase-2 (COX-2) in normal squamous epithelium, squamous dysplasia and squamous cell carcinoma (SCC) of the esophagus, to elucidate the role of COX-2 in esophageal carcinogenesis, and to evaluate the in vitro effect and mechanism of a COX-2 inhibitor, NS-398, in inducing growth inhibition and apoptosis of human esophageal cancer cells. Methods: Biopsy specimens of esophageal dysplasia (n=21), and surgical resections of SCC (n=37) were compared with normal esophagus (n=37) and analyzed by RT-PCR. Human esophageal cells were used for the study. Anti-proliferative effect was measured by MTT, apoptosis was determined by DNA fragmentation assay. Results: Marked COX-2 expression was shown in SCC and esophageal squamous dysplasia, and no marked COX-2 expression was observed in the normal squamous epithelium, respectively. NS-398 could inhibit esophageal cells growth in a dose-dependent manner, induce apoptosis, and elevate caspase-3 activity in vitro. Conclusions: This study provides evidence that COX-2 is upregulated in the majority of cases of squamous dysplasia and SCC of esophagus, and that NS-398 can inhibit growth and induce apoptosis via activating caspase-3 activity in vitro. These results suggest that selective inhibitors of COX-2 may be an effective preventive and therapeutic option for esophageal carcinoma.

To investigate the effect of X-ray repair cross complementing 1 (XRCC1) genetic polymorphisms on esophageal cancer risk, we determined XRCC1 polymorphisms at codon 194 (Arg→Trp) and codon 399 (Arg→Gln) in 135 patients with esophageal squamous cell carcinoma (ESCC) and 152 normal controls from hospitals. Although polymorphism at codon 194 was not associated with risk for ESCC, we found that the frequency of XRCC1 399 Gln/Gln genotype in ESCC patients (14.1%) was significantly higher than that in normal controls (3.3%), and that XRCC1 399 Gln/Gln genotype was associated with an increased risk of ESCC (odds ratio (OR)=5.15, 95% confidence interval (CI): 2.42-0.93). In addition, we found that the risk for smoker increased 4.2-fold than non-smokers in the 399 Gln/Gln genotype (OR=4.20, 95% CI: 2.37-7.44). These results suggest that XRCC1 399 Gln/Gln genotype may contribute to the risk of ESCC and modify risk associated with smoking.

Cyclooxygenase-2 (cox-2) overexpression has been observed in several types of human cancers and has been implicated in carcinogenesis. To elucidate the role of cox-2 in esophageal carcinogenesis, we evaluated the expression of cox-2 in normal squamous epithelium squamous epithelial dysplasia