Molecular analysis of APC promoter methylation and protein expression in colorectal cancer metastasis

APC (adenomatous polyposis coli) promoter methylation has been linked to the early development of colorectal cancers. However, the role of APC methylation and its effect on protein expression in colon cancer metastasis is largely unknown. In this study, we investigated APC promoter methylation by Methylight analysis and analysed the APC protein levels by immunohistochemistry and western blot analysis in 24 liver metastasis and 39 primary colorectal cancers. Promoter methylation of the APC gene was found to be a frequent event in liver metastasis (10/24) and significantly more frequent compared with primary colorectal cancer (7/39, P = 0.047). APC methylation was not found in 14 matched normal colon tissues. APC protein was detected in the cytoplasm of primary and metastatic cancer cells and non-tumorous colon epithelium. By western blot analysis, APC protein levels were found to be decreased in primary tumour tissues compared with the normal colon mucosa. In contrast, APC protein levels were not decreased in the cancer cells that had metastasized to the liver. APC protein levels were independent of the presence of APC promoter methylation or gene mutations. In summary, APC promoter methylation is a frequent epigenetic alteration in colorectal cancer metastasis. However, we observed no significant association between APC promoter methylation or gene mutation and APC protein expression in colorectal metastasis. Therefore, metastatic cancer cells seem to harbour a heterogenous genetic and epigenetic background, in which cancer cells may exhibit APC promoter methylation that is independent of APC expression.     

Analysis of the beta-catenin/T cell factor signaling pathway in 36 gastrointestinal and liver cancer cells.

We investigated the frequency and mechanism of beta-catenin/T cell factor (Tcf) signaling activation in a panel of 36 human gastrointestinal and liver cancer cell lines. Reporter assay and electrophoretic mobility shift assay revealed that the beta-catenin/Tcf signaling was upregulated in 12 of 12 (100%) colorectal, 5 of 8 (68%) gastric, 2 of 7 (29%) hepatic, and none of 9 pancreatic cancer cell lines. The activation of the pathway was mainly due to the mutation of adenomatous polyposis coli (APC) or beta-catenin, and Tcf-4 was highly expressed in these cell lines with upregulated signaling. Nuclear beta-catenin was observed not only in the signaling-activated cell lines, but also in 14 of 25 (56%) primary gastric cancers, 15 of 20 (75%) colon cancers, 5 of 19 (26%) hepatocellular carcinomas, and none of 13 pancreatic cancers. The presence of signaling-upregulated gastric cancer cell lines with intact APC and beta-catenin suggests the involvement of other mechanisms than mutations of APC or beta-catenin.     

beta-catenin expression in primary and metastatic colorectal carcinoma.

beta-catenin plays a fundamental role in the regulation of the E-cadherin-catenin cell adhesion complex. It also functions in growth signalling events, independently of the cadherin-catenin complex, and these signalling pathways are disturbed in colorectal cancer. Mutations in either the APC or beta-catenin genes in colorectal cancer cells result in up-regulation of protein expression and subsequent cytoplasmic and nuclear distribution of beta-catenin. In this study, we examined beta-catenin expression in 47 primary colorectal tumors and the corresponding liver metastases. Immunohistochemical studies demonstrated loss of membranous beta-catenin expression in 26% of primary tumors and 60% of liver metastases and a concomitant increase in cytoplasmic and nuclear staining. Widespread nuclear expression of beta-catenin was found in 64% of primary tumors and 21% of liver metastases. No associations were found between any form of beta-catenin expression and either tumor stage or tumor grade. Cellular distribution of beta-catenin was also examined by detergent extraction and Western blot analysis in 16 primary tumors and 23 liver metastases. This analysis showed that most tumors demonstrated reduced beta-catenin in the cytoskeletal fraction and increased beta-catenin in the cytosolic fraction. Furthermore, 3 liver metastases were found to contain a truncated beta-catenin protein of approximately M(r) 80,000. Immunoprecipitation studies showed that the truncated beta-catenin proteins only bound weakly to E-cadherin and beta-catenin compared with non-truncated beta-catenin. These results demonstrate gross alterations in the cellular distribution of beta-catenin in primary colorectal cancers with metastatic potential, as well as in the metastatic tumors. These changes may be the consequence of APC or beta-catenin gene mutations, or possibly result from a post-translational modification of the E-cadherin-catenin complex.     

Hypermethylation of the TPEF/HPP1 gene in primary and metastatic colorectal cancers

The role of promoter methylation in the process of cancer cell metastasis has, however, not yet been studied. Recently, methylation of the TPEF (transmembrane protein containing epidermal growth factor and follistatin domain) gene was reported in human colon, gastric, and bladder cancer cells. Using the Methylight assay, TPEF/HPP1 gene methylation was assessed in primary colorectal cancers (n = 47), matched normal colon mucosa, as well as in the liver metastasis of 24 patients with colorectal cancer, and compared to the methylation status of the TIMP-3, APC, DAPK, caveolin-2, and p16 genes. TPEF was frequently methylated in primary colorectal cancers (36 of 47) compared to the normal colon mucosa (1 of 21) (P < .0001), and TPEF mRNA expression in colon cancer cell lines was restored after treatment with 5-aza-2'-deoxycytidine. The p16 and APC genes were also frequently methylated in primary colorectal cancers (P < .02) compared to the normal colon mucosa. Interestingly, promoter methylation was significantly more frequent in proximal, nonrectal cancers (P < .05). Furthermore, a high degree of methylation of the TPEF gene was also observed in liver metastasis (19 of 24). In summary, we observed frequent TPEF methylation in primary colorectal cancers and liver metastases, indicating that epigenetic alterations are not only present in the early phases of carcinogenesis, but are also common in metastatic lesions. The high frequency of TPEF methylation in this series of colorectal cancers underscores the importance of epigenetic changes as targets for the development of molecular tests for cancer diagnosis.     

胃癌中连接蛋白32和43的表达及细胞间隙连接通讯功能的研究

目的探讨细胞间隙连接蛋白(Cx)表达及细胞间隙连接通讯(GJIC)功能状况与胃癌发生、发展的关系。方法采用免疫组化和间接免疫荧光法分别检测胃癌组织和不同分化程度的胃癌细胞系中Cx32和Cx43的表达;应用Western blot法检测Cx43在胃癌组织、癌旁组织及不同分化胃癌细胞系中的表达;应用划痕染料示踪技术检测不同细胞系中细胞GJIC功能。结果在正常胃组织中,Cx32和Cx43的阳性表达率均为100.0%,在胃癌组织中Cx32和Cx43的阳性表达率分别为49.5%(55/111)和39.6%(44/111)。Cx32的表达与组织类型、分化程度、远处转移及临床分期有关(P<0.05),而与侵袭程度、年龄无关(P>0.05);Cx43的表达与组织类型、分化程度、远处转移、侵袭程度及临床分期有关(P<0.05),而与年龄无关。Cx32和Cx43在转化的人胃黏膜细胞系GES-1中的阳性表达率均为100.0%;在胃高分化腺癌细胞系N87中的阳性表达率分别为49.0%和55.0%;在胃低分化腺癌细胞系BGG-823中均无表达。GES-1细胞具有强GJIC功能,N87和BGC-823细胞均无GJIC功能。Cx43在胃癌组织中的表达量明显低于癌旁正常组织,在GES-1和N87细胞中的表达水平依次递减,在BGC-823细胞中几乎无表达。结论Cx32和Cx43表达下降与胃癌的发生、发展有关。     

Mutational analysis of the beta-catenin gene in gastric carcinomas.

Previous studies reported that mutation of the adenomatous polyposis coli (APC) gene was not observed in the majority of gastric cancers. To evaluate the role of the APC/beta-catenin/Tcf pathway, we analyzed mutations in the beta-catenin gene and the accumulation of beta-catenin protein in gastric carcinomas. An interstitial deletion spanning exon 3 of the beta-catenin gene was observed in 1 of 13 gastric cancer cell lines. No missense mutation was found in these 13 cell lines. Nuclear and/or cytoplasmic localization of beta-catenin was observed in 16 of 70 primary gastric carcinomas by immunohistochemistry, while we found no mutations in exon 3 in 35 carcinoma tissues available for PCR amplification. Our findings suggest that somatic mutations of the beta-catenin gene are rare in human gastric carcinomas and that accumulation of normal beta-catenin protein in a subset of gastric cancers may be due to other mechanisms of its activation.     

Altered expression of beta-catenin in renal cell cancer and transitional cell cancer with the absence of beta-catenin gene mutations.

Loss of normal beta-catenin expression and the beta-catenin gene mutations have been shown to contribute to the malignant character of various cancers. Using PCR-single-strand conformation polymorphism and DNA direct sequencing, we examined the presence of genetic alterations within the third exon of beta-catenin, which are frequently observed in other tumors, in transitional cell cancer (TCC) and renal cell cancer (RCC) cell lines, and in tumor specimens. The degrees of expression and intracellular distribution of beta-catenin were detected by immunohistochemical staining in 77 primary and 12 metastatic RCCs and in 81 primary TCCs. Western blot analysis was also applied to confirm the degree of beta-catenin expression in the cell lines and some tumor samples. We failed to reveal any genetic alterations, at least in the third exon of the beta-catenin gene, in RCC and TCC. Reduced membranous immunoreactivity of beta-catenin was observed in portions of RCC (15.5%) and TCC (24.7%) and was correlated with advanced stages and nodal involvement in RCC and with advanced stages and multiple tumors in TCC. Within the power limitations of this small study, beta-catenin abnormal expression was not correlated with recurrence or survival in either RCC or TCC. Interstitial deletions and mutations in the third exon of beta-catenin do not play a significant role in RCC or TCC tumorigenesis. Down-regulation of normal beta-catenin expression might contribute to the malignant character of RCC and TCC and result in tumor progression. However, this event is not an independent prognostic factor for recurrence or tumor specific survival.     

下调热休克蛋白 27 表达对胃癌细胞侵袭转移能力的影响

目的：下调胃癌细胞HSP27的表达水平,观察胃癌细胞侵袭转移能力的变化.方法：利用Western blot方法选取HSP27高表达的胃癌细胞系,采用siRNA技术下调HSP27的表达,通过Transwell小室和划痕实验观察细胞系侵袭转移能力的变化.结果：Western blot实验结果显示,BGC823细胞和MKN28细胞中HSP27的呈高表达状态.转染HSP27-siRNA后,BGC823细胞和MKN28细胞中HSP27在蛋白水平和mRNA水平表达量均有显著地下降,验证转染成功.Transwell小室和划痕实验发现,转染HSP27-siRNA后BGC823和MKN28细胞的侵袭转移能力显著低于阴性对照组.结论：HSP27与胃癌细胞的侵袭转移能力密切相关,抑制HSP27的表达能够使胃癌细胞的侵袭转移能力明显下降.     

Correlation of Wnt-2 expression and beta-catenin intracellular accumulation in Chinese gastric cancers: relevance with tumour dissemination

Wnt/beta-catenin signalling pathway is integrally associated with human tumour development and progression. Aberrant beta-catenin intracellular distribution has been found in gastric cancer, but the pattern of Wnt expression in stepwise gastrocarcinogenesis and its potential influence in beta-catenin distribution are still lesser known. By the methods of frozen tissue array-based immunohistochemistry, Western blot analysis and RT-PCR, a paralleled study was conducted to check Wnt2 expression and beta-catenin intracellular distribution in two major subtypes of gastric cancers (intestinal gastric cancer, i-GC and diffuse gastric cancer, d-GC) and their premalignant (intestinal metaplasia, IM and chronic gastritis, CG) and noncancerous counterparts. According to the results obtained and the clinical data collected, correlation of Wnt2 expression with beta-catenin translocalisation and their links with tumour dissemination were elucidated. The results demonstrated (1) that Wnt2 expression and cytoplasmic/nuclear beta-catenin accumulations appeared in most gastric cancers irrespective to their morphological phenotypes, (2) that over-expressed Wnt and nuclear translocalisation of beta-catenin were found in 68 and 58% of i-GCs and in 47 and 47% of d-GCs in a closely related pattern (P<0.01) and (3) that co-existence of Wnt2 up-regulation/beta-catenin nuclear translocalisation were positively associated with lymph node metastasis (P<0.05) as well as T-stage. These data indicate that Wnt/beta-catenin signalling pathway is activated in most of gastric cancers, which may play pivotal roles either in gastric cancer formation or in tumour invasion and dissemination.     

MEMO1共结合IGF-IR介导胃癌细胞侵袭转移

目的:探讨MEMO1（mediator of ErbB2-driven cell motility 1）调控IGF-IR（insulin-like growth factor-I receptor）介导胃癌侵袭转移的分子机制,为临床治疗提供潜在靶点。方法:选取五种不同分化程度胃癌细胞系（MKN-7、NCI-N87、MGC-803、BGC-823、MKN-74）,Western blot检测MEMO1、IGF-IR和E-cad表达差异;Transwell比较五种胃癌细胞系迁移能力;选取MEMO1/IGF-IR高表达细胞系MGC-803,瞬时敲除MEMO1或IGF-IR基因,Western blot检测EMT标志物表达差异;IP实验检测MEMO1与IGF-IR间相互作用;TCGA数据库分析胃癌组织MEMO1和IGF-IR mRNA表达水平与患者预后的关系。结果:基础状态下五种胃癌细胞IGF-IR与MEMO1的表达呈显著正相关,并且两种蛋白的表达强度与胃癌细胞EMT相关;五种胃癌细胞迁移能力MKN-7相似文献   

Runx3 suppresses gastric cancer metastasis through inactivation of MMP9 by upregulation of TIMP-1

Recent studies have suggested that loss of RUNX3 expression is involved with gastric tumor metastasis. However, the precise mechanism of RUNX3-mediated suppression of tumor metastasis remains elusive. We aimed to clarify the effect of RUNX3 on tumor metastasis in gastric cancer cell lines and tumors. Immunohistochemistry revealed that RUNX3 was significantly decreased in metastatic gastric cancer. Gelatin zymography and Western blot showed that instead of regulating matrix metalloproteinase 9 (MMP9) expression, RUNX3 expression inhibited MMP9 enzyme activity, and this was consistent with the upregulation of tissue inhibitor of metalloproteinases 1 (TIMP1) by RUNX3. TIMP1 siRNA treatment impaired RUNX3-mediated suppression of gastric cancer cell invasion. Reporter assays demonstrated regulation of TIMP-1 by RUNX3. Two RUNX3 binding sites were identified in the TIMP-1 promoter and direct interaction of RUNX3 with the TIMP-1 promoter was confirmed in vitro and in vivo. These findings provide evidence for RUNX3-mediated suppression of gastric cancer invasion and metastasis and define a novel molecular mechanism that for the metastasis-inhibiting activity of RUNX3. These data may be applied in the development of RUNX3 for gastric cancer metastasis diagnostics and therapeutics.     

UHRF1在胃癌侵袭和转移中的作用及其机制

目的 探讨甲基化调节因子UHRF1在胃癌转移过程中的作用及其调控机制。方法 RT-PCR和Western blot检测胃癌高低转移细胞系中UHRF1的表达,应用UHRF1的siRNA和质粒改变UHRF1的表达,Transwell及体内转移实验检测胃癌转移能力的变化。甲基化特异性PCR和Western blot检测UHRF1表达改变后p16^INK4A和RB1的甲基化状态及蛋白表达。结果 UHRF1在高转移潜能的胃癌细胞系GC9811-P中的表达显著高于低转移潜能的细胞系GC9811。下调UHRF1的表达抑制胃癌细胞的体外和体内转移能力,同时减弱p16^INK4A甲基化,增加p16^INK4A蛋白表达。上调UHRF1的表达可见相反结果。结论 UHRF1可能通过调控p16^INK4A和RB1的甲基化促进胃癌细胞的侵袭和转移,其有望成为胃癌转移预警和治疗的新靶点。     

5-氮胞苷对EBV阳性胃癌细胞系特异性去甲基作用的体外实验探讨

探讨去甲基化试剂5-氮胞苷对EBV阳性胃癌细胞系的特异性去甲基作用。方法：用逆转录-聚合酶链式反应（RT-PCR）和PCR-southern检测不同剂量5-氮胞苷处理前后EBV启动子的活性,并用Westernblot检测EBV相关基因的表达。结果：5-氮胞苷处理后EBV阳性胃癌细胞系中被甲基化失活的C启动子重新活化,并表达LMP1（潜伏性膜蛋白1）,且呈剂量依赖性。结论：5-氮胞苷可能对EBV阳性胃癌的特异性治疗有帮助。     

原肌球蛋白4在胃癌细胞迁移、侵袭和转移中的作用

目的:探索原肌球蛋白4（Tropomyosin4,TPM4）在胃癌细胞的迁移、侵袭和转移中的作用。方法:利用Real-time PCR、Western Blot及免疫荧光,检测原肌球蛋白4在不同胃癌细胞系及正常胃上皮细胞中的表达情况;利用免疫组化,检测原肌球蛋白4在胃癌组织及癌旁正常组织中的表达情况;利用慢病毒技术,在GC9811-P细胞中,分别转染LV-TPM4、shRNA-TPM4及对照空载体;通过Transwell和体内实验,检测胃癌细胞迁移、侵袭和转移。结果:Real-time PCR、Western Blot及免疫组化结果显示,原肌球蛋白4在胃癌细胞系及胃癌组织中的表达降低;上调原肌球蛋白4的表达后,抑制胃癌细胞的迁移、侵袭和转移;下调原肌球蛋白4的表达后,促进胃癌细胞的迁移、侵袭和转移（P<0.05）。结论:原肌球蛋白4抑制胃癌细胞的迁移、侵袭和转移。