Aspirin inhibits the proliferation of tobacco-related esophageal squamous carcinomas cell lines through cyclooxygenase 2 pathway:

Protein kinase D1 mRNA level may predict cancer-specific survival in heavy smokers with esophageal squamous cell cancers

Protein kinase D1 (PRKD1) is a kinase that regulates various pathways, which involve in cell proliferation, apoptosis, cell adhesion and invasion. Although PRKD1 expression has been observed in many cancers, its role in esophageal squamous cell cancer (ESCC) has not been well reported. As its dysregulation in cancers is organ specific, we sought to investigate the potential role of PRKD1 in the progression of ESCC. Samples were collected from 178 patients with completely resected ESCCs at Sun Yat-sen University Cancer Center, including 47 pairs of tumorous and non-tumorous tissues. PRKD1 mRNA expression was investigated by quantitative real-time polymerase chain reaction. Receiver operating characteristic (ROC) curve analysis was used to search for a feasible cut-off point of PRKD1 mRNA levels for predicting cancer-specific survival. Kaplan-Meier and multivariate Cox regression analysis were used to assess the prognostic value of PRKD1 mRNA level in ESCC patients. In result, upregulation of PRKD1 mRNA was detected in 55.3% (26/47) of ESCC tissues compared with paired non-tumorous ones (P = 0.011). ROC analysis indicated 3.28 as a cut-off point, and thus 72 and 106 tumors with low and high PRKD1 mRNA expression were categorized. High-PRKD1 mRNA expression in tumors appeared with more frequency in heavy smokers (P = 0.002) and patients with advanced pathological T category (P = 0.034). Kaplan-Meier analysis indicated that patients with low-PRKD1 mRNA had a longer cancer-specific survival than the ones with high-PRKD1 level (P = 0.044). Multivariate analysis showed that tumorous PRKD1 mRNA expression was an independent prognostic factor (hazard ratio: 1.538, 95% confidence interval: 1.018-2.323, P = 0.041) in resected ESCC. Subgroup analysis revealed that the discernibility of PRKD1 mRNA level on ESCC outcomes was only pronounced in heavy smokers (P = 0.002), but not in non-heavy smokers (P = 0.870). PRKD1 might play a potential oncogenic role in ESCC. It might be an independent biomarker to predict prognosis in heavy smokers with ESCC.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone induces retinoic acid receptor β hypermethylation through DNA methyltransferase 1 accumulation in esophageal squamous epithelial cells

Overexpression of DNA methyltransferase 1 (DNMT1) has been detected in many cancers. Tobacco exposure is known to induce genetic and epigenetic changes in the pathogenesis of malignancy. 4-(Methylnitrosamino)- 1-(3-pyridyl)-1-butanone (NNK) is an important carcinogen present in tobacco smoke; however the detailed molecular mechanism of how NNK induces esophageal carcinogenesis is still unclear. We found that DNMT1 was overexpressed in ESCC tissues compared with paired non-cancerous tissues, the overexpression being correlated with smoking status and low expression of RARβ. The latter could be upregulated by NNK treatment in Het-1A cells, and the increased DNMT1 expression level reflected promoter hypermethylation and downregulation of retinoic acid receptor β (RARβ). RNA interference mediated knockdown of DNMT1 resulted in promoter demethylation and upregulation of RARβ in KYSE30 and TE-1 cells. 3-(4,5-Dimethyl-thiazol-2yl)- 2,5-diphenyltetrazolium bromide (MTT) and flow cytometric analysis demonstrated that NNK treatment in Het- 1A cells could enhance cell proliferation and inhibit cell apoptosis in a dose-dependent manner. In conclusion, DNMT1 overexpression is correlated with smoking status and low expression of RARβ in esophageal SCC patients. NNK could induce RARβ promoter hypermethylation through upregulation of DNMT1 in esophageal squamous epithelial cells, finally leading to enhancement of cell proliferation and inhibition of apoptosis.

Promoter methylation regulates cigarette smoke-stimulated cyclooxygenase-2 expression in esophageal squamous cell carcinoma

OBJECTIVE

Cigarette smoke extracts (CSE) could promote esophageal squamous cell carcinoma (ESCC) through upregulation of cyclooxygenase-2 (COX-2) expression. Promoter methylation mediates the transcriptional modulation of the COX-2 gene. The aim of the study was to explore whether COX-2 promoter methylation regulated COX-2 expression and functional activity in ESCC exposed to CSE.

METHODS

The methylation status of COX-2 promoter in two human ESCC cell lines, EC109 and TE-1, was examined using bisulfite sequencing analysis. COX-2 mRNA and protein expression were detected by reverse-transcription polymerase chain reaction and Western blot. Prostaglandin E₂ (PGE₂) was examined by enzyme linked immunosorbent assay (ELISA).

RESULTS

The promoter was hypermethylated in TE-1 which had a low level of COX-2 expression and was hypomethylated in EC109 with a relatively high level of COX-2 expression. Stimulation by cigarette smoke ethanol extract (EE) resulted in increased COX-2 expression in EC109, but not in TE-1. Treatment with 5-aza-2'-deoxycytidine (5-aza-DC) demethylated the promoter and upregulated COX-2 expression as well as PGE(2) production in TE-1, especially followed by EE stimulation. No significant effect was observed in EC109.

CONCLUSION

These findings suggest that promoter methylation may be one of the mechanisms regulating COX-2 expression in ESCC in response to stimulation of CSE.

Effects of DNA methyltransferase 1 inhibition on esophageal squamous cell carcinoma

To explore the role of DNA methyltransferase 1 (DNMT1) in esophageal squamous cell carcinoma (ESCC) and the potential of DNMT1-targeted small interfering RNA as ESCC therapy, we examined expression changes of DNMT1 in ESCC and investigated the effect of DNMT1 knockdown by RNA interference in a human ESCC cell line, KYSE30. DNMT1 messenger RNA was over-expressed in seven out of 12 ESCC samples, and the percentage of cells expressing DNMT1 was significantly higher in ESCC tissues compared with paired non-cancerous tissues. DNMT1 protein levels correlated with lymph node metastasis, but exhibited no correlation with sex, age, tumor site, or tumor differentiation. Knockdown of DNMT1 in KYSE30 cells using RNA interference resulted in a reduction of promoter methylation and re-expression of methyl-guanine methyl-transferase and retinoic acid receptors beta, inhibition of cell proliferation/viability and induction of cell apoptosis. These results indicate that DNMT1 over-expression is involved in ESCC and correlated with lymph node metastasis. Knockdown of DNMT1 led to promoter demethylation and re-expression of several tumor suppressor genes thereby inhibiting cell proliferation/viability and inducing cell apoptosis.

Dual inhibition of 5-LOX and COX-2 suppresses esophageal squamous cell carcinoma

COX-2 and 5-LOX are up-regulated in ESCC. This study aims to determine the efficacy of COX-2 inhibitor, 5-LOX inhibitor and their combination on ESCC. Nimesulide can suppress cell growth and promote apoptosis, accompanied with a decrease of PGE(2) production. AA861 has the similar effect with a down-regulation of LTB(4). In animal experiment, the tumor volumes in drug-treated groups were significantly smaller with the lowest rates of Ki-67 positive cells. In conclusion, either COX-2 inhibitor or 5-LOX inhibitor can suppress ESCC. Dual inhibition of COX-2 and 5-LOX pathway may present a superior anticancer efficacy to either inhibition of COX-2 or 5-LOX alone.

Cyclooxygenase-2 Gly587Arg variant is associated with differential enzymatic activity and risk of esophageal squamous-cell carcinoma

Functional SNPs in the COX-2 promoter region have been associated with susceptibility to esophageal squamous-cell carcinoma (ESCC). In this study, we investigated SNPs in the COX-2 coding region and their impact on risk of ESCC. The coding region of COX-2 in DNAs from 30 Han Chinese individuals was sequenced to identify SNPs. Different coding region variants identified were cloned and expressed in MCE-7 cells for the measurement of COX-2 enzymatic activity. Genotypes were determined by PCR-RFLP in 1026 patients with ESCC and 1270 controls and odds ratios (ORs) and 95% confidence intervals (CI) were computed by logistic regression model. A SNP at exon 10 (1759G>A, rs3218625) was identified, which causes (587)Gly to (587)Arg amino acid substitution. Enzymatic assays using different recombinant COX-2 variants showed that COX-2-(587)Arg had significantly higher activity towards arachidonic acid than COX-2-(587)Gly (13.8 +/- 3.2 U/mg vs. 11.2 +/- 2.4 U/mg; P = 0.012). Case-control analysis showed that 10.2% of ESCC patients carried the 1759A allele whereas only 5.4% of controls had this allele (P < 0.0001). No homozygous 1759AA genotype was presented in controls albeit two patients carrying this genotype. Multivariate logistic regression analysis revealed that subjects with at least one 1759A allele had increased risk for the development of ESCC (OR, 1.91; 95% CI, 1.39-2.62) compared with those with the 1759GG genotype. These results extend our previous findings and indicate that inherited variant in arachidonic acid-metabolizing enzyme, which results in heightened enzymatic activity, may confer susceptibility to ESCC.

Esophageal cancer: epidemiology, pathogenesis and prevention

Esophageal cancer is highly aggressive and is a common cancer both worldwide and in the US. In the past two decades, the incidence and mortality of esophageal cancer in the US have both increased, where as the incidence and mortality of other cancers have decreased. Although esophageal squamous cell carcinoma and esophageal adenocarcinoma differ in their histology and epidemiologic distribution, some of their risk factors (e.g. dietary deficiencies and tobacco) and underlying mechanisms of carcinogenesis are the same. Intensive research into risk factors combined with the ability to identify precursor lesions (e.g.squamous dysplasia in esophageal squamous cell carcinoma and Barrett's esophagus in esophageal adenocarcinoma) has paved the way for studies of chemoprevention for esophageal cancer, some of which have shown promising results.