JAM3基因甲基化是食管鳞状细胞癌潜在的分子标志物

目的研究JAM3基因启动子区在食管癌中的甲基化情况及其表达调控机制,探讨JAM3基因启动子区异常甲基化作为食管鳞状细胞癌的潜在诊断标志物和治疗靶标。方法应用半定量RT-PCR、甲基化特异性PCR等技术对7个食管癌细胞系(KYSE140、KYSE150、KYSE410、KYSE450、COLO680N、KYSE520和TE13)、5例正常食管黏膜组织和83例原发性食管鳞状细胞癌组织进行分析。结果JAM3 mRNA在KYSE520、KYSE140、KYSE450细胞中高表达,这些细胞的JAM3基因启动子区呈非甲基化状态。JAM3 mRNA在KYSE410、COLO680N、TE13、KYSE150细胞中表达缺失,且其基因启动子区在这些细胞中呈完全甲基化。经过5-Aza-dc处理后,JAM3基因在KYSE410、COLO680N、TE13、KYSE150细胞中恢复表达。这些结果表明,JAM3在食管癌细胞中的表达受启动子区甲基化的调控。JAM3基因启动子区在5例正常食管黏膜组织中呈非甲基化状态(0/5),而在原发性食管鳞状细胞癌中其甲基化率为50.6%(42/83),且JAM3甲基化与肿瘤的位置相关(P<0.05)。结论JAM3在食管鳞状细胞癌中频繁发生甲基化,JAM3基因的表达受启动子区甲基化的调控,JAM3基因是潜在的食管癌诊断标志物和治疗靶标。     

Expression of ECRG4, a novel esophageal cancer－related gene,downregulated by CpG island hypermethylation in human esophageal squamous cell carcinoma

AIM: To study the mechanisms responsible for inactivation of a novel esophageal cancer related gene 4 (ECRG4) in esophageal squamous cell carcinoma (ESCC). METHODS: A pair of primers was designed to amplify a 220 bp fragment, which contains 16 CpG sites in the core promoter region of the ECRG 4 gene. PCR products of bisulfite-modified CpG islands were analyzed by denaturing high-performance liquid chromatography (DHPLC), which were confirmed by DNA sequencing. The methylation status of ECRG 4 promoter in 20 cases of esophageal cancer and the adjacent normal tissues, 5 human tumor cell lines (esophageal cancer cell line-NEC, EC109, EC9706; gastric cancer cell line- GLC; human embryo kidney cell line-Hek293) and 2 normal esophagus tissues were detected. The expression level of the ECRG 4 gene in these samples was examined by RT-PCR. RESULTS: The expression level of ECRG 4 gene was varied. Of 20 esophageal cancer tissues, nine were unexpressed, six were lowly expressed and five were highly expressed compared with the adjacent tissues and the 2 normal esophageal epithelia. In addition, 4 out of the 5 human cell lines were also unexpressed. A high frequency of methylation was revealed in 12 (8 unexpressed and 4 lowly expressed) of the 15 (80 %) downregulated cancer tissues and 3 of the 4 unexpressed cell lines. No methylation peak was observed in the two highly expressed normal esophageal epithelia and the methylation frequency was low (3/20) among the 20 cases in the highly expressed adjacent tissues. The methylation status of the samples was consistent with the result of DNA sequencing. CONCLUSION: These results indicate that the inactivation of ECRG 4 gene by hypermethylation is a frequent molecular event in ESCC and may be involved in the carcinogenesis of this cancer.     

Downregulation of retinoic acid receptor-β2expression is linked to aberrant methylation in esophageal squamous cell carcinoma cell lines

AIM: To study the role of hypermethylation in the loss ofretinoic acid receptorβ2(RARβ2) in esophageal squamous cell carcinoma (ESCC).METHODS: The role of hypermethylation in RAR,β2 gene silencing in 6 ESCC cell lines was determined by methylationspecific PCR (MSP), and its methylation status was compared with RARβ2 mRNA expression by RT-PCR. The MSP results were confirmed by bisulfite sequencing of RARβ2promoter regions. RESULTS: Methylation was detected in 4 of the 6 cell lines, and the expression of RARβ2was markedly downregulated in 3 of the 4 methylated cell lines. The expression of RARβ2was restored in one RARβ2-downregulated cell line with the partial demethylation of promoter region of RARβ after 5aza-2'-deoxycytidine (5-aza-dc) treatment.CONCLUSION: The methylation of the 5' region may play an important role in the downregulation of RARβ2 in someESCC cell lines, suggesting that multiple mechanisms contribute to the loss of RARβ2expression in ESCC cell lines. This study may have clinical applications for treatment and prevention of ESCC.     

Downregulation of retinoic acid receptor-β2expression is linked to aberrant methylation in esophageal squamous cell carcinoma cell lines

AIM:To study the role of hypermethylation in the loss of retinoic acid receptor β2(RARβ2) in esophageal squamous cell carcinoma (ESCC).METHODS:The role of hypermethylation in RARβ2 gene silencing in 6 ESCC cell lines was determined by methylation-specific PCR (MSP),and its methylation status was compared with RARβ2 mRNA expression by RT-PCR.The MSP results were confirmed by bisulfite sequencing of RARβ2promoter regions.RESULTS:Methylation was detected in 4 of the 6 cell lines,and the expression of RARβ2 was markedly downregulated in 3 of the 4 methylated cell lines. The expression of RARβ2 was restored in one RARβ2-downregulated cell line with the partial demethylation of promoter region of RARβ2 after 5-aza-2′-deoxycytidine (5-aza-dc) treatment.CONCLUSION:The methylation of the 5′ region may play an important role in the downregulation of RARβ2 in some ESCC cell lines, suggesting that multiple mechanisms contribute to the loss of RARβ2expression in ESCC cell lines.This study may have clinical applications for treatment and prevention of ESCC.     

Association of mu‐opioid receptor expression with lymph node metastasis in esophageal squamous cell carcinoma

The mu‐opioid receptor (MOR), a membrane‐bound G protein‐coupled receptor, is the main target for opioids in the nervous system. MOR1 has been found in several types of cancer cells and reported to be involved in tumor progression and metastasis. However, the expression and clinical significance of MOR1 in esophageal squamous cell carcinoma (ESCC) remain unclear. In our study, the expression of MOR1 was confirmed in ESCC cell lines (KYSE180, KYSE150, and EC109) by Western blot. MOR1 was also detected on tissue microarrays of ESCC samples in 239 cases using immunohistochemical staining. We found that MOR1 was mainly located in the cytoplasm and occasionally occurred in the membrane or nucleus of ESCC cells. Moreover, results indicated that MOR1 expression in the cytoplasm was associated with lymph node metastasis (R = 0.164, P = 0.008, Kendall's tau‐b‐test). No more associations were found between MOR1 expression status and other clinical parameters. However, no statistical significant differences were found between MOR1 expression in the cytoplasm, nucleus/membrane, and the overall survival of ESCC patients (P = 0.848; P = 0.167; P = 0.428, respectively, log‐rank test). Our results suggest that the cytoplasmic MOR1 may be a high‐risk factor for lymph node metastasis of ESCC patients. We also hypothesize that MOR1 agonists used in ESCC patients should be prudent, and opioid receptor antagonists may be novel therapeutic drugs for ESCC patients.     

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.     

Trop-2表达下调对食管鳞癌EC9706细胞增殖和细胞迁移的影响

目的:研究肿瘤相关钙信号传导蛋白2(tumorassociated calcium signal transducer-2,Trop-2)表达下调对食管鳞癌EC9706细胞增殖和细胞迁移的影响,并探讨其可能的分子机制.方法:将Trop-2 siRNA和对照siRNA转染食管鳞癌EC9706细胞,利用实时荧光定量PCR和...     

Novel poly (ADP‐ribose) polymerase inhibitor,AZD2281, enhances radiosensitivity of both normoxic and hypoxic esophageal squamous cancer cells

Radiotherapy plays an important role in the treatment of esophageal squamous cell carcinoma (ESCC). However, the outcome of radiotherapy in ESCC remains unsatisfactory because esophageal squamous cancer cells, particularly those under hypoxic condition, exhibit radioresistance. The aim of this study was to determine whether or not AZD2281, a potent poly (ADP‐ribose) polymerase (PARP) inhibitor, could enhance the radiation sensitivity of two ESCC cell lines, namely ECA109 and TE13. The radiosensitizing effect of AZD2281 was evaluated on the basis of cell death, clonogenic survival and tumor xenograft progression. AZD2281 alone was slightly toxic to ESCC cell lines. Apoptosis was increased and clonogenic survival was decreased in both cell lines when AZD2281 was combined with ionizing radiation (IR) under normoxic condition. AZD2281 enhanced IR‐induced apoptosis to a more significant level under chronic hypoxic condition (0.2% O₂, 48 hour) than under normoxic condition. AZD2281 also slightly enhanced clonogenic cell death under chronic hypoxic condition compared with that under normoxic condition. This result could be associated with increased radiation‐induced DNA double‐strand breaks (DSB), decreased DSB repair and increased apoptosis of ESCC cells. Furthermore, homologous recombination (HR) protein Rad51 expression and focus formation were decreased in ESCC cells exposed to moderate chronic hypoxic condition (0.2% O₂, 48 hour); this result indicated that chronic hypoxic ESCC cells were HR deficient, possibly causing contextual synthetic lethality with PARP inhibitor in radiation sensitization. AZD2281 was also a radiation sensitizer in ESCC tumor xenograft models. Hence, in vitro and in vivo findings provide evidence that AZD2281 potently sensitizes ESCC cells to X‐ray irradiation. The selective cell killing of HR‐defective hypoxic cells contributes to radiosensitization by PARP inhibitor in ESCC cells under hypoxic condition.     

5-Aza-CdR对人食管癌细胞株中T-cadherin基因表达和细胞增殖的影响

背景：T-cadherin在肿瘤的发生中可能扮演肿瘤抑制基因的角色．在食管癌等多种肿瘤中的表达明显下降。目的：探讨去甲基化制剂5-氮杂-2’-脱氧胞苷（5-Aza-CdR）对人食管癌细胞株EC109中T—cadherin基因表达和细胞增殖的影响。方法：常规培养人食管癌细胞株EC109．并分为5μmol／L5-Aza-CdR组和对照组。以甲基化特异性PCR（MSP）法检测T-cadherin基因启动子区甲基化状态．RT-PCR和蛋白质印迹法分别检测T-cadherinmRNA和蛋白表达,MTr法检测EC109细胞增殖。结果：对照组EC109细胞中T-cadhefin基因启动子区呈异常甲基化状态．5-Aza-CdR干预可逆转甲基化状态。与对照组相比,5-Aza-CdR组T-cadherin基因mRNA和蛋白表达均显著增高（P〈0．01）．细胞增殖明显受到抑制。结论：去甲基化制剂5-Aza-CdR通过逆转食管癌细胞中T-cadherin基因启动子区甲基化状态来增强其表达．并抑制肿瘤细胞增殖．