| Objective: Esophageal cancer is one of the most dangerous cancers in the world. Southern region in Hebei Province of China, is high incidence area of esophageal cancer, and the incidence of squamous cell carcinoma of esophagus has been reported to be the highest in the world at 199/100,000 population per year. Although surgical resection and adjuvant chemo-radiotherapy provide excellent palliation of the neoplasm, the 5-year survival rate is less than 30%. Therefore, early identification and new strategies for treatment of esophageal cancer are urgently needed. One possible approach is to use non-steroidal anti-inflammatory drugs (NSAIDs) because recent epidemiological and experimental studies have demonstrated the therapeutic potential of NSAIDs such as aspirin and NS-398 in the chemoprevention of esophageal cancer. But the anti-cancer mechanism of NSAIDs is not fully elucidated. The effects of NSAIDs are thought to be mediated mainly through the inhibition of cyclooxysegenases (COXs) and prostaglandins (PGs). There are two distinct isoforms of COXs, COX-1 and COX-2.COX-1, which is constitutively expressed in most cells, is responsible for various physiological functions. On the other hand, COX-2 mRNA and protein, which is normally undetectable in most tissues, is frequently over-expressed in tumors, including esophageal cancer, and is related to cell proliferation and apoptosis. COX-2 and COX-2-drived PGs play an important role in the regulation of proliferation and apoptosis in many tumor cells. Therefore, the anti-cancer effect of NSAIDs is likely to be attributed to the inhibition of COX-2 activity/expression and COX-2-drived PGs. Several reports have suggested that COX-2 gene promoters contain a regulatory DNA sequence to which nuclear factor-κB (NF-κB) binds, and COX-2 expression is regulated by NF-κB in several cell lines. It was reported that NF-κB, an inducible transcription factor, had constitutively activity in many cancer cells, and played an important role in cell transformation, proliferation, apoptosis, and tumor development. No studies have reported that whether NF-κB activity is constitutively expressed in esophageal cancer, and whether the anti- esophageal cancer mechanism of NSAIDs is mediated though inhibiting NF-κB activity. In this study, to elucidate the possible anti-esophageal cancer mechanism of NSAIDs, we used human esophageal cancer TE13 cells, which is a poorly differentiated squamous cell carcinoma cell line, to investigate the effects of two NSAIDs, a nonselective COX-2 inhibitor aspirin and a selective COX-2 inhibitor NS-398, on NF-κBactivation, COX-2 expression, PGs synthesis, cells proliferation and apoptosis. Methods: Human esophageal cancer TE13 cells were cultured in vitro, and then treated with aspirin or NS-398 at different concentrations or at a concentration for different time. Cell proliferation was assessed by MTT assay. Cell apoptosis was detected by transmission electron microscope and cell flow cytometry (FCM). Levels of 6-keto-PGF1α were determined by radioimmunoassay (RIA) kit. COX-2 mRNA or protein expression were detected by reverse transcription polymerase chain reaction (RT-PCR) or Western blot analysis. IκB protein level in cytoplasm and NF-κB activity were determined with Western blot analysis and electrophoretic mobility shift assay (EMSA), separately. COX-2 mRNA and protein expression, IκB protein level in cytoplasm, were semi-quantitatively analyzed by Gel-Pro Analyzer software. Data were presented as (s and analyzed with ANOVA and least significant difference (LSD) using SPSS statistical program. A level of P<0.05 was considered statistically significant.Results:1 The effects of NSAIDs on proliferation and apoptosis in esophageal cancer TE13 cells 1.1 aspirin and NS-398 inhibit proliferation MTT assay showed incubation with aspirin or NS-398 for 72 h resulted in a dose-dependent growth inhibition inTE13 cells. The percentage of proliferation in control cells was regarded as 100%. Compared to c...
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