Overexpression and mutations of tumor suppressor gene p53 in hepatocellular carcinoma

AIMS To examine the prevalance of p53 mutations in hepatocellular carcinoma (HCC) from Chongqing area and the relationship between the p53 mutations and clinicopathological features of HCC,as well as the risk factors. METHODS The overexpression and point mutations of tumor suppressor gene p53 in 38 cases of HCC were detected by a sensitive antigen retrieval fluid (ARF) immunohistochemical method and polymerase chain re- action(PCR)-restriction fragment length polymorphism (RFLP),and single strand conformation polymorphism (SSCP)-silver staining analysis. RESULTS The results showed that 16 of 38 HCCs had positive p53 protein (42.1%),7 HCCs had p53 mutation at 249 (18.4 % ) and 2 HCCS had point muta- tion within exon 7 other than 249. Among 9 cases of HCC with mutations,8 cases demonstrated positive p53 protein,its coincidental rate was 88.9%. The overexpression and mutations of p53 were significantly related to the differentiation and metastasis of HCCs. The frequency of p53 mutations was consistent with high prevalence of HBV and a moderate aflatoxin B1 (AFB1) exposure in our area. CONCLUSIONS The results suggest that AFB1 acts synergistically with HBV in the generation of p53 mutations. Furthermore,dietary exposure to AFB1 may mainly contribute to the tumor specific mutation at codon 249,while HBV may account for other scattered mutations in HCC.

p53 gene mutations in primary gastric cancer

AIMS p53 gene is one of the focuses in the study of tu- mour suppressor genes.So far,there is still controversy about the relationship between p53 alterations and clinicolpathological parameters of gastic cancers such as macroscopic classifica- tion,stage,degree of differentiation,depth of tumour invasion and lymphonod metastasis.Tamura has reported that p53 gene mutations mainly occur in the aneuploid tumours.But in China, nothing is reported in this field of study.Our aim is to analyze the relationship between p53 gene mutations and these param- eters including DNA ploidy in Chinese primary gasrtic cancers. METHODS Mutations of the p53 gene in exon5-8 were examined in 20 cases of primary gasric cancer by PCR-SSCP (Polymerase-chain-reaction-single-strand-conforma- tion-polymorphism)analysis. RESULTS Mutations were detected in 8(40%)cases:2 cases in exon5-6,2 cases in exon7,4 cases in exon8.These mutations were detected from stage 0 to stage Ⅲ No significant association was found between p53 gene mutations and the clinicopathological parameters such as macroscopic classifico- tion,degree of histological differentiation,depth of tumour in- vasion and lymphonod metastasis.In addition,66.7%(6 of 9) of aneuploid tumours had p53 mutations and only 18.2%(2 of 11)of diploid tumours had mutations. CONCLUSIONS These results suggest that p53 gene muta- tions are related to DNA ploidy alterations and that p53 gene is one of the important turnout suppressor genes in human gastric cancer.

Codon 249 mutations of p53 gene in non-neoplastic liver tissues

AIM To study the significance of p53 gene in hepatocarcinogenesis through analyzing codon 249 mutations of p53 gene in non neoplastic liver tissues. METHODS Codon 249 mutation was detected using single stranded conformational polymorphism analysis and allele specific PCR in liver tissues from 10 cases of chronic hepatitis, 5 cases of cirrhosis and 20 cases of HCCs. RESULTS The detection rate of codon 249 mutation in chronic hepatitis, cirrhosis and pericancerous tissues was 70% (7/10), 100% (5/5) and 70% (14/20), respectively by AS PCR. These mutations could not be detected by SSCP analysis. The detection rates were 65% (13/20) and 45% (9/20) in cancerous tissues by AS PCR and SSCP analysis. CONCLUSION Codon 249 mutations of p53 gene were very popular in non neoplastic liver tissues though the number of those mutant cells was only in subsection. Those mutations in cancerous tissues might take place in the stage before the formation of tumor.

Infrequent p53 gene mutation and expression of the cardia adenocarcinomas from a high-incidence area of Southwest China

INTRODUCTIONAdenocarcinomas of the cardia are the lesionsarising from the proximal stomach or within 3 cm ofthe gastroesophageal junction.These cancerstended to be advanced at the time of presentation,usually with poor prognosis.In recent decade,the incidence of adenocarcinoma of gastric eardiaand esophagus are increasing steadily,while therehas been a decrease in the proportion of the cancersarising from the distal stomach.The

Codon 249 mutations of p53 gene in development of hepatocellular carcinoma

AIM To investigate the mechanisms of codon 249 mutation of p53 gene in the formation of hepatocellular carcinoma (HCC). METHODS Codon 249 mutation accompanied by loss of heterozygosity (LOH) and its effect on translation and transcription were studied using SSCP, IHC and RT PCR/slot hybridization. RESULTS Codon 249 mutations were detected in 32 9%, LOH detected in 68 4% among the HCC patients. Mutations of condon 249 were accompanied by LOH in 90%. The positive rates of p53 protein and mRNA were 91 3% and 95 7%, in mutational group, both were significantly higher than those in the non mutational group (91 3% vs 19 1% and 95 7% vs 40 4%, respectively, both P <0 01). The translation of p53 gene was strongly related to its transcription by correlation analysis ( r =0 8208). CONCLUSIONS LOH might play an important role in hepatocarcinogenesis of codon 249 mutation, which could increase both transcription and translation of p53 gene. The increased expression of p53 protein mainly depend on the increased transcription of p53 gene.

Sequencing of p53 mutation in established human hepatocellular carcinoma cell line of HHC4 and HHC15 in nude mice

AIM To set up cell lines of human hepatocellular carcinoma in nude mice for the research of cell biology and gene therapy. METHODS Xenotransplantation of human hepatoma into nude mice was carried out and the growth rate, histopathology and immunology of the nude mice were studied. The DNA from xenografts were analyzed by HBV gene and PCR amplification of a fragment of p 53 gene exon 7, which were identified by dot blot hybridization, restriction fragments length polymorphism and DNA sequencing. RESULTS hHCC4 and hHCC415 cell lines could be successively transplanted in nude mice and the population doubling time was 7 and 5 days respectively. These strains retained the original characteristics of histopathology, secreting AFP and heteroploid karyotypes in human hepatocellular carcinoma. The fragment of HBV gene was detected in the genomic DNA of both hHCC4 and hHCC15, however only hHCC4 secreted HBsAg. The mutation at 250 code (C→A) and 249 code (G→T) were detected respectively in the genomic DNA of hHCC4 and hHCC15. CONCLUSION The two cell lines are useful material for studying cell biology and gene therapy in human hepatocellular carcinoma and provide molecular biological trace of the relationship between high mortality of hepatoma and AFB1 severe pollution of the daily common foods in this district.

Genetic aberration in primary hepatocellular carcinoma:correlation between p53 gene mutation and loss-of-heterozygosity on chromosome 16q21-q23 and 9p21-p23

To elucidate the molecular pathology underlying the development of hepatocellular carcinoma (HCC), we used 41 highly polymorphic microsatellite markers to examine 55 HCC and corresponding non-tumor liver tissues on chromosome 9, 16 and 17. Loss-of-heterozygosity (LOH) is observed with high frequency on chromosomal region 17p13 (36/55, 65%), 9p21-p23 (28/55, 51%), 16q21-q23 (27/55, 49%) in tumors. Meanwhile, microsatellite instability is rarely found in these microsatellite loci. Direct sequencing was performed to detect the tentative mutation of tumor suppressor genes in these regions: p53, MTS1/p16, and CDH1/E-cadherin. Within exon 5-9 of p53 gene, 14 out of 55 HCC specimens (24%) have somatic mutations, and nucleotide deletion of this gene is reported in HCC for the first time. Mutation in MTS1/pl6 is found only in one tumor case. We do not find mutations in CDH1/E-cadherin. Furthermore, a statistically significant correlation is present between p53 gene mutation and loss of chromosome region 16q21q23 and 9p21-p23, which indicates that synergism between p53 inactivation and deletion of 16q21-q23 and 9p21-p23 may play a role in the pathogenesis of HCC. Genetic aberration in hepatocellular

Correlation of p53 gene mutation and expression of P53 protein in cholangiocarcinoma

AIM： To characterize the tumor suppressor gene P53 mutations and study the correlation of P53 gene mutation and the expression of P53 protein in cholangiocarcinoma. METHODS： A total of 36 unselected, frozen samples of cholangiocarcinoma were collected, p53 gene status（exon 5-8） and P53 protein were examined by automated sequencing and immunohistochemical staining, combined with the clinical parameters of patients. RESULTS： P53 gene mutations were found in 22 of 36 （61.1%） patients. Nineteen of 36 （52.8%） patients were positive for P53 protein expression. There were significant differences in extent of differentiation and invasion between the positive and negative expression of P53 protein. However, there were no significant differences in pathologic parameters between the mutations and non-mutations. CONCLUSION： The alterations of the P53 gene evaluated by DNA sequence analysis is relatively accurate. Expression of P53 protein could not act as an independent index to estimate the prognosis of cholangiocarcinoma.

Analysis of N-ras gene mutation and p53 gene expression in human hepatocellular carcinomas

IM To study the relationship between Nras gene mutation and p53 gene expression in the carcinogenesis and the development of human hepatocellular carcinomas (HCC).METHODS The Nras gene mutation and the p53 gene expression were analyzed in 29 cases of HCC by polymerase chain reactionsingle strand conformation polymorphism (PCRSSCP) and immunohistochemistry.RESULTS Thirteen cases of HCCs were p53 positive (448%), which showed a rather high percentage of p53 gene mutation in Guangxi. The aberrations at Nras codon 2-37 were found in 7931% of HCCs and 8077% of adjacent nontumorous liver tissues. More than 2 point mutations of Nras gene were observed in 22 cases (7586%). Twelve cases (4137%) of HCCs showed both Nras gene mutation and p53 gene expression.CONCLUSIONS Nras gene and p53 gene may be involved in the carcinogenesis and the development of HCC. That 38% of HCCs with Nras gene mutation did not express p53 protein indicates that some other genes or factors may participate in the carcinogenesis and the development of HCC.

苯丙氨酸羟化酶基因c.158G>A(p.Arg53His)突变患儿随访及突变位点功能评估

目的:评价苯丙氨酸羟化酶(PAH)基因c.158G>A(p.Arg53His)突变的临床意义。方法:持续监测2例携带PAH基因p.Arg53His突变的疑似高苯丙氨酸血症患儿血液中苯丙氨酸(Phe)浓度,分析患儿的临床生化特征,应用T-Coffee系统分析PAH蛋白的跨种属保守性,应用Swiss-Model对正常结构及变异结构的PAH进行蛋白质三维结构建模及比对分析突变所致蛋白质空间结构的改变。检索现有数据库及文献统计p.Arg53His突变的人群携带率,应用等位基因表型值(APV)与基因型表型值(GPV)预测系统对该突变相关表型进行预测。结果:2例新生儿在PAH基因上分别检出两个突变:c.611A>G(p.Tyr204Cys)、c.158G>A(p.Arg53His)和c.1238G>C(p.Arg413Pro)、c.158G>A(p.Arg53His)。2例新生儿能耐受正常饮食,在随访期间血Phe水平在正常范围内。例2的母亲为p.Arg53His纯合突变,长期未进行低蛋白质、低Phe饮食干预,血Phe浓度、Phe/酪氨酸比值均在正常范围。突变的氨基酸在13个不同物种间并非高度保守。三维结构建模结果显示,p.Arg53His突变使得PAH第53位和第49位氨基酸之间的氢键由2个减少为1个,降低了二聚体的稳定性。p.Arg53His在高苯丙氨酸血症患者中的等位基因频率为0.01508,在健康人群中的等位基因频率为0.001621,其中东亚人群中的携带率最高,为0.01373。APV与GPV系统预测结果显示,该突变与轻度高苯丙氨酸血症型别相关。结论:PAH基因p.Arg53His突变与不同突变组合为复合杂合状态可引起临床表型差异。p.Arg53His突变引起体内酶活性的降低不足以出现苯丙酮尿症临床症状,分类为“可能良性”。

The point mutation of p53 gene exon7 in hepatocellular carcinoma from Anhui Province,a non HCC prevalent area in China

AIM: In hepatocellular carcinoma (HCC) prevalent areas of China, the point mutation of p53 exon7 is highly correlated with Hepatitis B virus(HBV) infection and aflatoxin B intake. While in non-HCC-prevalent areas of China, these factors are not so important in the etiology of HCC. Therefore, the point mutation of p53 exon7 may also be different than that in HCC-prevalent areas of China. The aim of this study is to investigate the status and carcinogenic role of the point mutation of p53 gene exon7 in hepatocellular carcinoma from Anhui Province, a non-HCC-prevalent area in China. METHODS: PCR PCR-SSCP and PCR-RFLP were applied to analyze the homozygous deletion and point mutation of p53 exon7 in HCC samples from Anhui, which were confirmed by DNA sequencing and Genbank comparison. RESULTS: In the 38 samples of hepatocellular carcinoma, no homozygous deletion of p53 exon7 was detected and point mutations of p53 exon7 were found in 4 cases, which were found to be heterozygous mutation of codon 249 with a mutation rate of 10.53%(4/38). The third base mutation(G-T) of p53 codon 249 was found by DNA sequencing and Genbank comparison. CONCLUSION: The incidence of point mutation of p53 codon 249 is lower in hepatocellular carcinoma and the heterozygous mutation of p53 exon7 found in these patients only indicate that they have genetic susceptibility to HCC. p53 codon 249 is a hotspot of p53 exon7 point mutation, suggesting that the point mutation of p53 exon 7 may not play a major role in the carcinogenesis of HCC in Anhui Province, a non-HCC-prevalent area in China.

p53 mutation regulates PKD genes and results in co-occurrence of PKD and tumorigenesis

Objective: Polycystic kidney disease(PKD) is the major cause of kidney failure and mortality in humans. It has always been suspected that the development of cystic kidney disease shares features with tumorigenesis, although the evidence is unclear.Methods: We crossed p53 mutant mice(p53N236S, p53S) with Werner syndrome mice and analyzed the pathological phenotypes.The RNA-seq, ss GSEA analysis, and real-time PCR were performed to dissect the gene signatures involved in the development of disease phenotypes.Results: We found enlarged kidneys with fluid-filled cysts in offspring mice with a genotype of G3mTerc^(-/-)WRN^(-/-)p53^(S/S)(G3TM).Pathology analysis confirmed the occurrence of PKD, and it was highly correlated with the incidence of tumorigenesis. RNA-seq data revealed the gene signatures involved in PKD development, and demonstrated that PKD and tumorigenesis shared common pathways, including complement pathways, lipid metabolism, mitochondria energy homeostasis and others. Interestingly, this G3TM PKD and the classical PKD1/2 deficient PKD shared common pathways, possibly because the mutant p53S could regulate the expression levels of PKD1/2, Pkhd1, and Hnf1b.Conclusions: We established a dual mouse model for PKD and tumorigenesis derived from abnormal cellular proliferation and telomere dysfunction. The innovative point of our study is to report PKD occurring in conjunction with tumorigenesis. The gene signatures revealed might shed new light on the pathogenesis of PKD, and provide new molecular biomarkers for clinical diagnosis and prognosis.

Specific intronic p53 mutation in esophageal squamous cell carcinoma in Southern Thailand

AIM:To investigate p53 mutations in esophageal cancer in a high-risk population,and correlate them with smoking,alcohol consumption and betel chewing.METHODS:One hundred and sixty-five tumor samples of esophageal squamous cell carcinoma(ESCC) obtained from a university hospital in Songkhla province,Southern Thailand were investigated for p53 mutations in exons 5-8,using polymerase chain reaction-single strand conformation polymorphism analysis,followed by direct sequencing.A polymerase chain reactionrestriction fragment length polymorphism(RFLP) assay was additionally used to confirm possible germline mutation in intron 6.A history of risk habits was obtained by interviews.The association between risk habits and mutation frequency was evaluated using the χ 2 test.RESULTS:The studied specimens were from 139 male and 26 female patients with ESCC,treated at Songklanagarind Hospital.Most of the patients were smokers(86.7%) and alcohol consumers(72.73%),and 38.3% were betel chewers.Forty-three mutations of the p53 gene were detected in 25.5%(42/165) of tumor samples.Mutations were most commonly found in exon 5(25.6%) and exon 8(25.6%).Mutations in the hot-spot codon 248 were found in four cases(9.3% of all mutations).G:C→C:G(30.23%),G:C→A:T(27.90%) and G:C →T:A(16.28%) were the prevalent spectra of mutations.Unexpectedly,among 10 intronic mutations,eight cases harbored a similar mutation:G→C substitution in intron 6(nucleotide 12759,GenBank NC_000017).These were additionally confirmed by the RFLP technique.Similar mutations were also detected in their matched blood samples using RFLP and direct sequencing,which suggested germline mutations.There was no significant correlation between risk habits and p53 mutation frequency.CONCLUSION:A proportion of Thai ESCC patients harbored specific intronic p53 mutations,which might be germline mutations.Further studies are needed to explore this novel finding.

Screen p53 mutations in hepatocellular carcinoma by FASAY:A novel splicing mutation

Objective： To establish a routine procedure for the detection of p53 mutations in hepatocellular carcinoma （HCC） surgical resections using the FASAY （functional analysis of separated alleles of p53 on yeast） procedure. Methods： p53 status was analyzed by FASAY and cDNA sequencing in 50 cases of HCC. After the extraction of RNA from the frozen tumor and corresponding normal tissues, reverse transcription RT-PCR was carried out using these samples. The assay can detect mutations of p53 mRNA between codons 67 and 347 by the DNA-binding activity of the protein and reveal them as red colonies. Results： Of the 50 specimens, 29 （58%） were positive （mutan0 by FASAY. Sequencing analysis confirmed that all 29 FASAY positive tumors harbored mutations, and that no mutations were detectable in any FASAY negative tumors. In 29 p53 mutations, 22 mutations were point missense mutation, 5 were deletions and 2 were splicing mutations. A novel splice mutation on splice donor of intron 6 was reported, which could produce two different mRNAs, respectively using the nearest upstream and downstream recessive splice donor sites. Conclusion： FASAY is a sensitive method for detecting the various types of p53 mutations in HCC, suggesting that the yeast functional assay for the detection of p53 mutations may be essential for elucidating their clinical significance.

DETECTION OF POINT MUTATION OF p53 GENE BY SILVER STAINING PCR-SSCP IN PARAFFIN-EMBEDDED MALIGNANT FIBROUS HISTIOCYTOMA

Silver staining PCR-SSCP method was used to detect point mutation of p53 gene in paraffin-embedded malignant fibrous histiocytoma (MFH) tissues. The abnormal shifting of the single-stranded DNA (ssDNA) was identified in 9 out of 16 cases (56.3%). The positive figure of SSCP was 1, 4, 4, 3 in exon 5, 6, 7, 8, respectively. The mutant of p53 protein was detected by microwave oven treatment and ABC immunohistochemistry. Positive nuclear staining was observed in 10 cases (62.5%). The positive coincidence rate was 90.0% between SSCP and p53 protein expression. The mutation of p53 gene was not correlated with the subtypes of MFH. Our results indicate that detection of point mutations with silver staining PCR-SSCP is convenient, rapid and reliable in the screening of point mutation of genes.

DETECTION OF p53 GENE MUTATION OF BRONCHOSCOPIC SAMPLIES IN THE PATIENTS SUSPECTED TO LUNG CANCER

Objective: To determine the feasibility of detecting p53 gene mutations for early diagnosis of lung cancer using the samples from bronchoscopic examination. Methods: Point mutations of the exon 5-8 of p53 gene were detected in 85 bronchoscopic samples of 35 patients suspected to be lung cancer using silver staining PCR-SSCP. Results: p53 gene mutations were founded in 10 of 35 patients(28.6%). The incidence of p53 gene mutations (14.9%) was obviously higher than the cytological positive incidence(2.9%) in samples of sputum, bronchoalveolar lavage and brush, especially for the sputum(27.7%). In the bronchoscopic biopsy specimens, the incidence of p53 gene mutations (12.5%) was lower than that of pathologic positive result (50.0%). However, in view of all the bronchoscopic samples, there was no statistically difference between cytopathologic positive results (11.8%) and the incidence of p53 gene mutations (14.1%). Although the p53 mutations were most common in the samples from the patients bronchoscopically manifested as neoplasm compared with other manifestations, there was no statistical difference. It is valuable to notice that 3 patients with p53 gene mutation merely presented as bronchial inflammation in bronchoscope. Conclusion: Results indicated that the value of detecting p53 gene mutation for the diagnosis of lung cancer using the bronchoscopic samples was more superior to cytological examination and detection of p53 gene mutations in post-bronchoscopic sputum was easy and effective, may be used as a valuable method for early diagnosis of lung cancer.

THE SIGNIFICANCE OF P53 GENE MUTATIONS AND EXPRESSIONS IN HUMAN COLORECTAL TUMORS

Using a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) approach we analyzed 18 human colorectal adenocarcinomas for mutations in exons 5,6,7,8 of p53 gene. At the same time,p53 gene product expression was studied immunohistochemically in these 18 case in frozen sections. The expression of p53 protein was also immunohistochemically studied in formalin-fixed paraffin embeded spccimens of 76 colorectal adenocarcinomas and 112colorectal polyps. Eigbt out of 18 cases (44%) showed a variant band indicative of a mutation in exons 5-6 of p53gene 7 out of 8 cascs (88%) with p53 gene mutations were positivelystanined for P53. There was no significant correlation between p53. expression and clinicopathological manifestations and prognosis. but the strongest staining was cncountered in those cases with well differentiated and early stage adenocarcinomas,while weaker staining was encountered in Poorly differentiated and mucoid adenotarcinomas. p53expression was not observed in proliferative polyps and adenomas with low grade dysplasia. The frequency of p53expression reached 88% (p<0.001) when adenoma showed malignant change. Aiuong three types of adenomas, p53 expression was most frequent in villous type (P<0.05). The frequencies of p53 expression in adenoma, adenoma with malignant change and adenocarcinoma were 4%, 88% and 51% respectively.These indicate that genetic changes of p53 gene play an important role in the transformation from benign adeuoma to adenocarcinoma. p53 immunohistochcmistry can be used as a surrogate marker for p53 gene mutation for early discovery of colorectal adenocarcinomas.

P53 GENE MUTATIONS IN NON-SMALL CELL LUNG CANCER DETECTED BY POLYMERASE CHAIN REACTION SINGLE-STRAND CONFORMATION POLYMORPHISM ANALYSIS

Mutations of the p53 tumor suppressor gene are the most frequent genetic alterations detected in human lung cancer. To assess the pathogenic significance of p53 gene alterations in Chinese non small cell lung cancer(NSCLC),74 paired samples of primary lung cancer and normal lung tissue far away from the cancer were analyzed for mutations of the p53 gene(exons 5 8) using exon specific PCR, single strand conformation polymorphism (PCR SSCP). p53 mutations were observed in 55 4%(41/74) of the samples. No linkages were detected between the incidence of p53 mutations and histological type, lymph node metastasis,age or sex. Significant association between p53 mutations and degree of differentiation in adenocarcinomas, not in squamous cell carcinomas, was observed. The frequency of p53 mutations in smokers(65 3%) was higher than in nonsmokers(33 3%) and reached statistical significance.We also found p53 mutations in 6/7 samples which had tissue invasion and distant metastasis.These results suggest that smoking could be an important factor in lung carcinogenesis,p53 mutation is a worse prognosis indicator in adenocarcinomas and related to high aggressive behavior of human lung cancer.

DETECTION OF p53 GENE MUTATION IN PLASMA OF PATIENTS WITH GASTRIC CANCER

Objective: To investigated p53 gene mutation in plasma of gastric cancer patients. Methods: DNA extracted from plasma and matched tumor and tumor-adjacent non-cancerous tissues of 96 gastric cancer patients, and DNA from 20 healthy volunteers were studied. Exon 5, 6, 7, and 8 of p53 were amplified by Polymerase Chain Reaction (PCR). The mutation status was analyzed by denaturing high-performance liquid chromatography (DHPLC), followed by direct sequencing of cases with aberrant chromatographic patterns. Results: Heterozygous mutations of p53 gene were detected in 19.9% (19/96) of primary tumor tissues and 5.2% (5/96) of corresponding plasma. All p53 gene mutations detected in plasma DNA consisted with mutations in the matched primary tumor samples. Neither the tumor-adjacent gastric mucosa tissues nor control plasma from healthy volunteers showed p53 gene mutation. No correlation was found between p53 mutation status and clinicopathological features of gastric cancer patients. Conclusion: p53 gene mutation in plasma can be detected in tissues and plasma of gastric cancer patients, which could be applied in screening and surveillance of this disease.

Study of mutations of p53, APC and K-ras genes in 47 cases of intestinalmetaplasia of gastric mucosa

Objective:To study the role of the mutations of p53, APC and K-ras genes in 47 cases of 3 types of intestinal metaplasia (IM) of gastric mucosa. Methods:In 47 cases of IM, exons 5- 8 of p53 and exons 15 of APC were examined with PCR-SSCP and codon 12 of K-ras with PCR-RFLP to detect the existence of any mutations of these structures. Results:Muta- tions of p53, APC and K-ras were found in 29.8% (14/47),6.4% (3/47) and 6.4% (3/47) respectively in our series of patients who consisted of 33 with types I and II and 14 with type III of IM. The mutation rate of p53 was far higher in patients with type III IM (57.1%,8/14) than in those with types I and II IM(18.2%,6/33)(P <0.05). Though the mutation rate of APC and K-ras was also higher in the patients with type III IM than in those with types I and II IM, it was of no statistical significance (P >0.05). In one case of type III IM, mutation of both p53 and K-ras was found. Conclusion: The molecular changes of 3 types of IM are different. The mutation of p53 may be closely related to carcinogenesis in cases of type III IM and it serve as a sign for the early diagnosis of gastric carcinoma.