Recent progress in the study of methylated tumor suppressor genes in gastric cancer

Gastric cancer is one of the most common malignancies and a leading cause of cancer mortality worldwide.The pathogenesis mechanisms of gastric cancer are still not fully clear.Inactivation of tumor suppressor genes and activation of oncogenes caused by genetic and epigenetic alterations are known to play significant roles in carcinogenesis.Accumulating evidence has shown that epigenetic silencing of the tumor suppressor genes,particularly caused by hypermethylation of CpG islands in promoters,is critical to carcinogenesis and metastasis.Here,we review the recent progress in the study of methylations of tumor suppressor genes involved in the pathogenesis of gastric cancer.We also briefly describe the mechanisms that induce tumor suppressor gene methylation and the status of translating these molecular mechanisms into clinical applications.

MicroRNA-320a suppresses tumor progression by targeting PBX3 in gastric cancer and is downregulated by DNA methylation

BACKGROUND Ectopic expression of miRNAs promotes tumor development and progression.miRNA(miR)-320a is downregulated in many cancers,including gastric cancer(GC).However,the mechanism underlying its downregulation and the role of miR-320a in GC are unknown.AIM To determine expression and biological functions of miR-320a in GC and investigate the underlying molecular mechanisms.METHODS Quantitative real-time polymerase chain reaction(PCR)was used to determine expression of miR-320a in GC cell lines and tissues.TargetScanHuman7.1,miRDB,and microRNA.org were used to predict the possible targets of miR-320a,and a dual luciferase assay was used to confirm the findings.Western blotting was used to detect the protein levels of pre-B-cell leukemia homeobox 3(PBX3)in GC cells and tissue samples.Cell Counting Kit-8 proliferation,Transwell,wound healing,and apoptosis assays were performed to analyze the biological functions of miR-320a in GC cells.Methylation-specific PCR was used to analyze the methylation level of the miR-320a promoter CpG islands.5-Aza-2’-deoxycytidine(5-Aza-CdR)and trichostatin A(TSA)were used to treat GC cells.RESULTS miR-320a expression was lower in GC cell lines and tissues than in the normal gastric mucosa cell line GES-1 and matched adjacent normal tissues.miR-320a overexpression suppressed GC cell proliferation,invasion and migration,and induced apoptosis.PBX3 was a target of miR-320a in GC.The methylation level of the miR-320a promoter CpG islands was elevated and this was partly reversed by 5-Aza-CdR and TSA.CONCLUSION miR-320a acts as a tumor suppressor and inhibits malignant behavior of GC cells,partly by targeting PBX3.DNA methylation is an important mechanism associated with low expression of miR-320a.

Aberrant methylation of secreted protein acidic and rich in cysteine gene and its significance in gastric cancer

BACKGROUND Aberrant methylation in DNA regulatory regions could downregulate tumor suppressor genes without changing the sequences.However,our knowledge of secreted protein acidic and rich in cysteine(SPARC)and its aberrant methylation in gastric cancer(GC)is still inadequate.In the present research,we performed fundamental research to clarify the precise function of methylation on SPARC and its significance in GC.AIM To investigate promoter methylation and the effects of the SPARC gene in GC cells and tissues and to evaluate its clinical significance.METHODS Plasmids that overexpressed the SPARC gene were transfected into human GC BGC-823 cells;non-transfected cells were used as a control group(NC group).Quantitative real-time polymerase chain reaction and western blotting(WB)were then used to detect the expression of SPARC.Methylation-specific polymerase chain reaction was executed to analyze the gene promoter methylation status.Cell viability was measured by the cell counting kit-8 assay.The migration and invasion ability of cells were detected by scratch assays and transwell chamber assays,respectively.Cell cycle events and apoptosis were observed with a flow cytometer.RESULTS The expression of SPARC mRNA in GC tissues and cells was significantly lower and showed differing degrees of hypermethylation,respectively,than that in normal adjacent tissues and control cells.Treatment with 5-Aza-2’-deoxycytidine(5-Aza-Cdr)was able to restore the expression of SPARC and reverse promoter hypermethylation.Overexpression of the SPARC gene significantly inhibited proliferation,migration,and invasion of GC cells,while also causing cell cycle arrest and apoptosis;the NC group exhibited the opposite effects.CONCLUSION This study demonstrated that SPARC could function as a tumor suppressor and might be silenced by promoter hypermethylation.Furthermore,in GC cells,SPARC inhibited migration,invasion,and proliferation,caused cell cycle arrest at the G0/G1 phase,and promoted apoptosis.

Silence of HIN-1 expression through methylation of its gene promoter in gastric cancer

AIM: To clarify the role of high in normal-1 (HIN-1) gene promoter methylation during gastric cancer development. METHODS: Gastric cancer cell lines and tissue specimens were analyzed for expression of HIN-1 mRNA and protein using the semi-quantitative reverse transcription polymerase chain reaction and immunohistochemistry. The methylation of the HIN-1 gene promoter was detected in gastric carcinoma cells and tissues using methylation-specific polymerase chain reaction. The 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium cell viability assay and flow cytometry were used to assess the changes in behaviors of gastric cancer cells with or without 5-aza-2’-deoxycytidine treatment. RESULTS: HIN-1 was not expressed in 4 of 5 gastric cancer cell lines. The demethylation reagent 5-aza-2’-deoxycytidine was able to induce or upregulate HIN-1 expression in gastric cancer cell lines, which is associated with reduction of tumor cell viability. Furthermore, methylation of the HIN-1 gene promoter was shown in 57.8% (26/45) of the primary gastric cancer and 42.1% (17/38) of adjacent tissue samples, but was not shown in normal gastric mucosa (0/10). From the clinicopathological data of the patients, methylation of the HIN-1 gene promoter was found to be associated with tumor differentiation (P = 0.000). CONCLUSION: High methylation of HIN-1 gene promoter results in silence of HIN-1 expression in gastric cancer. 5-aza-2’-deoxycytidine reverses HIN-1 methylation and reduces viability of gastric cancer cells.

The False Paradigm of RUNX3 Function as Tumor Suppressor in Gastric Cancer

Gastric cancer (GC) is a major cause of cancer mortality. GC studies that aim to identify relevant oncogenes and tumor suppressor genes (TSGs) are essential for devising effective new therapies. A decade ago, RUNX3, a gene that resides on human chromosome 1p36.1, was claimed to be a major TSG in GC. Since then, hundreds of studies involving thousands of GC patients have attempted to verify and extend the RUNX3 TSG paradigm. However, RUNX3 is not recognized as TSG and not listed in the “Cancer Gene Census” website. To be a TSG that protects normal cells against malignancy, the gene must be expressed in the normal tissue from which the cancer arose and its loss or inactivation should contribute to cancer development. This review summarizes compelling body of evidence challenging the RUNX3-TSG paradigm. Studies show unequivocally that RUNX3 is not expressed in normal gastric epithelium and that it fails to fulfill all other premises of a TSG. RUNX3 mutations and 1p36 deletions are not frequent in GC and RUNX3 is not associated with familial GC or with increased risk of GC. Accordingly, Runx3-/- mice do not develop tumors. RUNX3 promoter methylation, which has been reported to be a frequent event in GC, is not relevant to its alleged TSG function, since the gene is already silent in normal gastric epithelium. In sharp contrast, overexpression of RUNX3 was found in several types of human cancers, including GC, and the 1p36.1 region is amplified in B-cell lymphoma. Thus, it is possible that RUNX3 actually promotes cancer development rather than being a TSG. The true targets for GC therapy are discussed below. Those are genes frequently lost or amplified in GC and are well known for their tumor suppressive or oncogenic activity, respectively.

Epigenetics: An emerging player in gastric cancer

Cancers,like other diseases,arise from gene mutations and/or altered gene expression,which eventually cause dysregulation of numerous proteins and noncoding RNAs.Changes in gene expression,i.e.,upregulation of oncogenes and/or downregulation of tumor suppressor genes,can be generated not only by genetic and environmental factors but also by epigenetic factors,which are inheritable but nongenetic modifications of cellular chromosome components.Identification of the factors that contribute to individual cancers is a prerequisite to a full understanding of cancer mechanisms and the development of customized cancer therapies.The search for genetic and environmental factors has a long history in cancer research,but epigenetic factors only recently began to be associated with cancer formation,progression,and metastasis.Epigenetic alterations of chromatin include DNA methylation and histone modifications,which can affect gene-expression profiles.Recent studies have revealed diverse mechanisms by which chromatin modifiers,including writers,erasers and readers of the aforementioned modifications,contribute to the formation and progression of cancer.Furthermore,functional RNAs,such as microRNAs and long noncoding RNAs,have also been identified as key players in these processes.This review highlights recent findings concerning the epigenetic alterations associated with cancers,especially gastric cancer.

Role of the Wnt/β-catenin pathway in gastric cancer: An indepth literature review

Gastric cancer remains one of the most common cancers worldwide and one of the leading cause for cancerrelated deaths. Gastric adenocarcinoma is a multifactorial disease that is genetically, cytologically and architecturally more heterogeneous than other gastrointestinal carcinomas.The aberrant activation of the Wnt/β-catenin signaling pathway is involved in the development and progression of a significant proportion of gastric cancer cases. This review focuses on the participation of the Wnt/b-catenin pathway in gastric cancer by offering an analysis of the relevant literature published in this field. Indeed, it is discussed the role of key factors in Wnt/β-catenin signaling and their downstream effectors regulating processes involved in tumor initiation, tumor growth, metastasis and resistance to therapy. Available data indicate that constitutive Wnt signalling resulting from Helicobacter pylori infection and inactivation of Wnt inhibitors(mainly by inactivating mutations and promoter hypermethylation) play an important role in gastric cancer. Moreover, a number of recent studies confirmed CTNNB1 and APC as driver genes in gastric cancer. The identification of specific membrane, intracellular, and extracellular components of the Wnt pathway has revealed potential targets for gastric cancer therapy. High-throughput "omics" approaches will help in the search for Wnt pathway antagonist in the near future.

Aberrant DNA methylation in cervical carcinogenesis

Persistent infection wit h high-risk types of human papillomavirus(HPV) is known to cause cervical cancer;however,additional genetic and epigenetic alterations are required for progression from precancerous disease to invasive cancer.DNA methylation is an early and frequent molecular alteration in cervical carcinogenesis.In this review,we summarize DNA methylation within the HPV genome and human genome and identify its clinical implications.Methylation of the HPV long control region(LCR) and L1 gene is common during cervical carcinogenesis and increases with the severity of the cervical neoplasm.The L1 gene of HPV16 and HPV18 is consistently hypermethylated in invasive cervical cancers and can potentially be used as a clinical marker of cancer progression.Moreover,promoters of tumor suppressor genes(TSGs) involved in many cellular pathways are methylated in cervical precursors and invasive cancers.Some are associated with squamous cell carcinomas,and others are associated with adenocarcinomas.Identification of methylated TSGs in Pap smear could be an adjuvant test in cervical cancer screening for triage of women with high-risk HPV,atypical squamous cells of undetermined significance,or low grade squamous intraepithelial lesion(LSIL).However,consistent panels must be validated for this approach to be translated to the clinic.Furthermore,reversion of methylated TSGs using demethylating drugs may be an alternative anticancer treatment,but demethylating drugs without toxic carcinogenic and mutagenic properties must be identified and validated.

Aberrant promoter CpG methylation and its translational applications in breast cancer

Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations.Recent studies revealed that abnormal gene expression induced by epigenetic changes,including aberrant promoter methylation and histone modification,plays a critical role in human breast carcinogenesis.Silencing of tumor suppressor genes(TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression,thus directly contributing to breast tumorigenesis.Usually,aberrant promoter methylation of TSGs,which can be reversed by pharmacological reagents,occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer.In this review,we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast cancer.

Frequent loss of heterozygosity at 8p22 chromosomal region in diffuse type of gastric cancer

AIM: To study the loss of heterozygosity (LOH) at 8p21-23 locus in diffuse gastric cancer.METHODS: To evaluate the involvement of this region in gastric cancer, we used eight microsatellite markers covering two Mb of mentioned region, to perform a high-resolution analysis of allele loss in 42 cases of late diffuse gastric adenocarcinoma.RESULTS: Six of these STS makers: D8S1149, D8S1645, D8S1643, D8S1508, D8S1591, and D8S1145 showed 36%, 28%, 37%, 41%, 44% and 53% LOH, respectively.CONCLUSION: A critical region of loss, close to the NAT2 locus and relatively far from FEZ1 gene currently postulated as tumor suppressor gene in this region.

Down-Regulation of GKN1 in Gastric Cancer Is Not Associated with the RUNX3 Expression

Gastrokine 1 (GKN1) is a gastric mucosal protein highly expressed and secreted in normal individuals but during Helicobacter pylori infection or in gastric carcinogenesis it is strongly down-regulated or totally absent. In gastric cancer, the GKN1 gene is silenced through an epigenetic mechanism most likely mediated by a transcription factor that promotes on GKN1 promoter the activity of the enzymes SUV39H1 and HDACs. Because RUNX3 is a potential candidate in the regulation of molecular carcinogenesis process of stomach cancers, we tried to assess if RUNX3 could be involved in GKN1 down-regulation in GC. 17 paired of non-tumoral and tumoral surgical specimens from patients with gastric cancer were analyzed for GKN1 and RUNX3 by Western blotting and chromatin immunoprecipitation (Chip) assays. The overall results indicated that RUNX3 expression was not associated with the down-regulation of GKN1. The expression levels of RUNX3 in non-tumoral and tumoral samples suggest that RUNX3 does not act as a tumor suppressor but that it might play a complex oncogenic role in gastric cancer cells.

Hypermethylation of tumor suppressor and tumor-related genes in neoplastic and non-neoplastic gastric epithelia

A number of tumor suppressor and tumor-related genes exhibit promoter hypermethylation with resultant gene silencing in human cancers.The frequencies of methylation differ among genes and genomic regions within CpG islands in different tissue types.Hypermethylation initially occurs at the edge of CpG islands and spreads to the transcription start site before ultimately shutting down gene expression.When the degree of methylation was quantitatively evaluated in neoplastic and non-neoplastic gastric epithelia using DNA microarray analysis,highlevel methylation around the transcription start site appeared to be a tumor-specific phenomenon,although multiple tumor suppressor genes became increasingly methylated with patient age in non-neoplastic gastric epithelia.Quantitative analysis of DNA methylation is a promising method for both cancer diagnosis and risk assessment.

Oncogenic induction of cellular high CpG methylation by Epstein-Barr Barr virus in malignant epithelial cells

Epstein-Barr virus(EBV)is a well-known human herpesvirus associated with virtually all nasopharyngeal carcinoma(NPC)and^10%of gastric cancer(GC)worldwide.Increasing evidence shows that acquired genetic and epigenetic alterations lead to the initiation and progression of NPC and GC.However,even deep whole exome sequencing studies showed a relatively low frequency of gene mutations in NPC and EBV-associated GC(EBVa GC),suggesting a predominant role of epigenetic abnormities,especially promoter Cp G methylation,in the pathogenesis of NPC and EBVa GC.High frequencies of promoter methylation of tumor suppressor genes(TSGs)have been frequently reported in NPC and EBVa GC,with several EBV-induced methylated TSGs identified.Further characterization of the epigenomes(genome-wide Cp G methylation profile—methylome)of NPC and EBVa GC shows that these EBV-associated tumors display a unique high Cp G methylation epigenotype with more extensive gene methylation accumulation,indicating that EBV acts as a direct epigenetic driver for these cancers.Mechanistically,oncogenic modulation of cellular Cp G methylation machinery,such as DNA methyltransferases(DNMTs),by EBV-encoded viral proteins accounts for the EBV-induced high Cp G methylation epigenotype in NPC and EBVa GC.Thus,uncovering the EBV-associated unique epigenotype of NPC and EBVa GC would provide new insight into the molecular pathogenesis of these unique EBVassociated tumors and further help to develop pharmacologic strategies targeting cellular methylation machinery in these malignancies.

HYPERMETHYLATION OF p14^(ARF) PROMOTER REGION AND EXPRESION OF p14^(ARF) GENE PRODUCT IN NON-SMALL CELL LUNG CANCER

Objective： This study was designed to investigate promoter methylation status and protein expression of p14^ARF gene in non-small cell lung cancer, and value the role of p14^ARF promoter methylation in carcinogenesis of non-small cell lung cancer. Methods： Promoter methylation status and protein expression of p14^ARF gene in 40 cases of non-small cell lung cancer were analyzed by methylation specific polymerase china reaction （MSP）, restriction enzyme-related polymerase chain reaction （RE-PCR） and immunohistochemistry （IHC）. Results： The positive rates of p14^ARF promoter methylation in tumor tissues and normal tissues adjacent to cancer were 17.5% （7/40） and 2.5% （1/40） respectively. There were statistically significant differences between them, P〈0.05. The results of RE-PCR were consistent with that of MSP. The expression rate of p14^ARF protein in tumor tissues was significantly lower than that in normal tissues adjacent to cancer, p〈0.01. Promoter methylation status and protein expression of p14^ARF gene in non-small cell lung cancer showed significantly an inverse correlation （r=-0.56, P〈0.01）, and both of them did not relate statistically with the clinicopathologic characteristics of patients such as histological classification, clinical stage, differentiation grade and lymph node involvement. Conclusion： Promoter methylation is a crucial mechanism of inactivation of p14^ARF gene. Promoter methylation of p14^ARF gene might he involved in carcinogenesis of non-small cell lung cancer, and is an early event in development process of non-small cell lung cancer. It might be used as a new target in gene treatments in the future.

Is metastatic pancreatic cancer an untargetable malignancy?

Metastatic pancreatic cancer(MPC) is one of the most aggressive malignancies, known to be chemo-resistant and have been recently considered resistant to some targeted therapies(TT). Erlotinib combined to gemcitabine is the only targeted therapy that showed an overall survival benefit in MPC. New targets and therapeutic approaches, based on new-TT, are actually being evaluated in MPC going from immunotherapy, epigenetics, tumor suppressor gene and oncogenes to stromal matrix regulators. We aim in this paper to present the major causes rendering MPC an untargetable malignancy and to focus on the new therapeutic modalities based on TT in MPC.

血浆Septin 9基因甲基化状态和水平在胃癌患者诊断和预后评估中的应用价值

背景与目的:胃癌是中国常见的恶性肿瘤之一,胃癌诊疗过程中仍缺乏高特异性、高灵敏度的生物标志物。甲基化的Septin9基因(methylated Septin9 gene,mSEPT9)在胃癌患者癌组织中特征性增高。本文旨在探讨胃癌患者血浆mSEPT9的表达及临床意义。方法:纳入2020年4月—11月在复旦大学附属中山医院检验科检测血浆mSEPT9(PCR荧光探针法)的221例诊断为胃癌的患者以及34例无疾病证据受检者,并应用ΔΔCt法对mSEPT9水平进行相对定量。收集相关临床资料,包括临床病理学资料(患者基本信息和病理学检查结果)和血清蛋白标志物[癌胚抗原(carcinoembryonic antigen,CEA)、糖类抗原(carbohydrate antigen,CA)12-5、CA19-9和CA72-4]并采用配对t检验、χ2检验和受试者工作特征(receiver operating characteristic,ROC)曲线进行分析。结果:mSEPT9在胃癌未治疗人群中的阳性率为35%(28/80),曲线下面积(area under curve,AUC)为0.8153,灵敏度为35%,特异度为100%。脉管内见癌栓、侵及浆膜层或周围组织和存在淋巴结转移的胃癌患者术前mSEPT9阳性率较高(46.87%vs 12.50%,45.16%vs 14.29%,75.00%vs 40.00%),差异均有统计学意义(P<0.05)。治疗后疾病进展(progressive disease,PD)患者mSEPT9阳性率高于治疗后部分缓解(partial response,PR)和稳定(stable disease,SD)患者(68.75%vs 17.74%),差异有统计学意义(P<0.05)。患者疾病进展前和疾病进展时mSEPT9ΔΔCt差异均有统计学意义(P<0.05)。结论:血浆mSEPT9基因检测在胃癌诊断中的灵敏度和特异性较传统血清蛋白标志物(CEA、CA12-5、CA19-9和CA72-4)更优。该标志物能提供严重程度相关信息,且在PD患者中阳性率较高。SEPT9状态和相对定量结果在预测术后病理学分期和治疗反应中具有潜在临床意义。

抑癌基因VHL与RNASET2甲基化协同microRNA调控卵巢癌细胞耐药逆转

目的 研究卵巢癌耐药细胞中抑癌基因甲基化和miRNA的关系以及对耐药逆转的影响。方法 基于基因表达公共数据库(GEO)筛选2个卵巢癌多药耐药相关数据集(GSE176218 Public on May 16,2022;GSE198077 Public on Apr 20,2022)鉴定抑癌基因。再通过甲基化位点分析,miRNA预测和GeneMANIA互作网络分析进行抑癌基因甲基化与miRNA的关系探讨。MTT和RT-PCR检测DNA甲基化抑制剂和(或)miRNA抑制剂作用下抑癌基因对耐药的影响。结果 卵巢癌耐药细胞中VHL和RNASET2表达下调,且与患者预后相关。VHL和RNASET2受到DNA甲基化调控。hsa-miR-635靶向RNASET2,hsa-miR-106b靶向VHL。VHL、RNASET2甲基化和miRNA协同调控。VHL与RNASET2重新表达通过PI3K/AKT信号通路逆转耐药。结论DNA甲基化和miRNA协同调控抑癌基因RNASET2和VHL的表达,并逆转卵巢癌细胞的多药耐药。

抑癌基因甲基化在肾细胞癌研究中的新进展

抑癌基因启动子高度甲基化被认为是除突变和缺失以外的抑癌基因功能失活的关键机制,在肿瘤的发生和发展中起重要作用,已成为目前肿瘤病因学基础研究的热点。肾细胞癌是泌尿系统最常见的恶性肿瘤之一,近年来也有许多文献报道了肾细胞癌中抑癌基因的异常甲基化情况。肾细胞癌临床发病隐匿,出现症状时多为晚期,肾细胞癌相关基因异常甲基化检测有望为肾癌的早期无创诊断提供新的途径。针对肾癌对放、化疗效果均不敏感的特点,改变DNA甲基转移酶活性和抑癌基因甲基化状况可作为肾细胞癌辅助治疗的一种新思路。本文对抑癌基因甲基化与肾细胞癌关系的研究进展作一综述,介绍DNA甲基化在肿瘤发生过程中的作用及机理;总结近7年来肾细胞癌中抑癌基因甲基化的研究情况和肾细胞癌独特的甲基化谱,并着重介绍了新近报道的HOXB13,HAI2/SPINT2,CDH1,CTNNG/JUP四个基因启动子异常甲基化与肾细胞癌的关系;阐述DNA甲基化研究对肾细胞癌的临床意义。

胃癌中新抑癌基因WTX启动子区域甲基化水平的检测(英文)

目的探讨抑癌基因WTX启动子区域甲基化水平及其在胃癌中的作用。方法运用MassARRAY定量分析系统分析20例胃癌及配对正常组织和3种胃癌细胞株(MGC803、SCG7901和BGC823)中WTX基因启动子区域甲基化水平。应用5-杂氮-2'-脱氧胞苷(5-aza-dC)对胃癌细胞BGC823进行去甲基化处理,分析其对WTX基因启动子区域甲基化水平的影响。结果在胃癌及其配对正常组织和胃癌细胞株中,WTX基因启动子区域甲基化水平普遍较低,并且3组之间无统计学差异。用5-aza-dC处理后并不能改变胃癌细胞株中WTX基因启动子区域的甲基化水平。结论胃癌中基本不存在WTX基因启动子区域高甲基化状态。

人胃癌细胞肿瘤相关基因的表达与甲基化调控

目的:旨在阐明胃癌的发生中多种抑癌基因和癌基因的甲基化情况,以期为进一步深入探索通过改变抑癌基因的甲基化而为胃癌治疗提供新方法. 方法:培养人胃癌细胞株MKN-45和HGC-27两种细胞,在MTT确定去甲基化制剂5-氮脱氧胞苷(5-aza- 2’-deoxycytidine,5-aza-dC)浓度和时间对细胞生长活力没有影响后,分别以2,5,和10μmol/L,浓度分别干预24和72 h,然后提取其DNA和RNA,用RT-PCR的方法检测p16INK4A,p21WAF1,p53,c-Ha-ras和c- myc等多种基因的表达情况;同时以流式细胞仪分析药物干预后的MKN-45和HGC-27的细胞周期变化; DNA分析则通过亚硫酸氢盐修饰和测序和甲基化特异性PCR(MSP)的方法检测p16INK4A基因及c-myc启动子区甲基化的情况. 结果:我们所采用的5-aza-dC的浓度和时间对细胞的生长无显著性影响.5-aza-dC干预前,MKN-45和HGC-27两种胃癌细胞系中均有p16INK4A表达,5-aza- dC干预后在MKN-45和HGC-27两种胃癌细胞系中p16INK4A的表达增强,且不同的胃癌细胞株表达增强最明显时的时间与浓度不同.-p53,p21WAF1,c-myc,c-Ha-ras 等多种基因在干预前后均有表达,且在干预前后无明显变化.在5-aza-dC干预后,HGC-27细胞周期阻滞在G1期,而MKN-45细胞的周期无明显改变.p16INK4A启动子区存在甲基化使得该基因的表达减少,在去甲基化试剂处理后使其表达增强. 结论:人胃癌细胞系MKN-45和HGC-27中,p16INK4A 启动子甲基化是其在表达减弱的主要原因,其去甲基化程度取决于5-aza-dC干预的时间和浓度.