卵巢癌中k-ras 基因点突变及p53蛋白表达

目的 探讨k—ras基因点突变和p53蛋白表达在卵巢癌发生中的作用及致癌机制。方法 采用显微切割技术、半巢式PCR—RFLP技术和免疫组化染色检测55例卵巢癌及其交界性病变中的k—ras基因点突变和p53蛋白表达。结果 k-ras基因点突变率在黏液性腺癌(61．9％)明显高于浆液性腺癌(14．2％),在黏液性交界性腺瘤(61．5％)明显高于浆液性交界性腺瘤(12．5％)。p53蛋白表达率在浆液性腺癌(80％)明显高于黏液性腺癌(52％),并随组织学分级而增高。结论 黏液性腺癌主要通过腺瘤-交界性腺瘤-腺癌途径致癌,k—ms基因点突变是黏液性腺癌的早期事件,黏液性交界性腺瘤是黏液性腺癌的癌前病变。浆液性腺癌主要通过生发上皮直接恶性转化形成,p53蛋白表达在浆液性腺癌的发生中起重要作用,是浆液性腺癌的晚期事件。     

p73基因在卵巢上皮性肿瘤中的表达及甲基化研究

目的 探讨卵巢上皮性肿瘤中p73蛋白的表达和基因启动子的甲基化情况,并观察其与临床病理学特征的关系.方法 制备包括68例卵巢癌、37例卵巢交界性肿瘤和21例卵巢良性肿瘤的组织芯片,用免疫组织化学EnVision法检测上述组织中p73蛋白表达情况,用亚硫酸氧盐修饰后测序法检测13例新鲜卵巢癌组织及5例新鲜卵巢交界性肿瘤组织的p73基因启动子甲基化情况.结果 92.6％ (63/68)的卵巢癌表达p73,p73蛋白总体表达率均值为32％(p73表达率指p73阳性细胞数所占的百分比),其中浆液性癌( 26/26)的表达率均值为40％,高于其他组织类型的癌(P=0.006).按照卵巢癌发病模式区分,Ⅱ型卵巢癌p73表达率均值(40％)高于Ⅰ型卵巢癌(24％),P=0.010.卵巢癌中p73的表达与临床分期及组织学分级无相关性(均P＞0.05).卵巢交界性肿瘤组(30/37)和良性肿瘤组(12/21)p73的总体表达率均值分别为16％和15％,该两组肿瘤中浆液性肿瘤表达率均值均高于黏液性肿瘤(P-0.003,P=0.026).卵巢癌组的p73阳性表达率均值明显高于交界性肿瘤组和良性肿瘤组(均P ＜0.05),交界性肿瘤组与良性肿瘤组比较差异无统计学意义(P＞0.05).浆液性肿瘤( 49/53)中,卵巢癌组(26/26) p73阳性表达率均值明显高于交界性肿瘤组(12/14)和良性肿瘤组(11/13;P =0.024和P=0.002),而卵巢交界性肿瘤组和良性肿瘤组比较差异无统计学意义(P=0.428).黏液性肿瘤(15/27)中,卵巢癌组(6/7)p73阳性表达率均值高于良性肿瘤组( 1/8;p=0.032),而卵巢癌组与卵巢交界性肿瘤组(8/12)、交界性肿瘤组与良性肿瘤组比较,差异均无统计学意义(P=0.234和P=0.201).p73启动子的甲基化结果显示,13例卵巢癌有8例发生甲基化,但每例样本甲基化频率有所不同,总体甲基化频率均值为8.0％.5例交界性肿瘤有2例发生甲基化,总体甲基化频率均值为9.0％,两组比较差异无统计学意义(P＞0.05).卵巢癌组p73甲基化额率与组织类型、发病模式、组织学分级及临床分期均无相关性(均P＞0.05).结论 卵巢上皮性肿瘤多数表达p73,卵巢癌p73的表达率均值明显高于交界性肿瘤和良性肿瘤,浆液性肿瘤高于其他组织类型;p73蛋白表达率与p73基因甲基化程度不存在简单线性相关关系.     

HDAC1和HDAC6蛋白过表达在卵巢浆液性癌中的临床病理学意义

目的探讨组蛋白去乙酰化酶(histone deacetylase,HDAC)1和6蛋白表达检测在卵巢浆液性癌中的临床病理学意义。方法选取147例卵巢病变的存档蜡块标本,其中包括39例卵巢浆液性囊腺瘤26例卵巢浆液性交界性囊腺瘤和82例卵巢浆液性囊腺癌。应用免疫组化EnVision法检测HDAC1和HDAC6基因蛋白在上述卵巢病变组织中的表达水平,并分析其蛋白检测的临床病理学意义。结果 HDAC1和HDAC6蛋白分别为胞核和胞质染色,HDAC1蛋白强阳性表达率在卵巢浆液性囊腺瘤、交界性浆液性肿瘤和浆液性囊腺癌中分别为7.7%(3/39)、65.4%(17/26)和80.5%(66/82);HDAC6蛋白的强阳性表达在39例卵巢浆液性囊腺瘤中完全阴性,而在交界性浆液性肿瘤中为34.6%(9/26)、在浆液性囊腺癌中则高达86.6%(71/86),差异均具有统计学意义。结论 HDAC1和HDAC6蛋白在卵巢癌发生发展过程中起重要作用,对于卵巢浆液性癌的诊断具有重要的辅助意义,有望成为卵巢癌治疗的新靶点。     

子宫颈癌FHIT基因表达与杂合性丢失

目的　探讨抑癌基因FHIT基因在子宫颈癌发生中的作用及其失活的可能机制。方法　选取FHIT基因内 2个微卫星位点D3S130 0和D3S12 34,对 5 6例经显微切割分离肿瘤组织的原发性子宫颈癌进行杂合性丢失 (LOH)分析 ,同时采用免疫组化方法 (S P法 )检测FHIT的表达情况。结果　D3S130 0和D3S12 34的LOH发生率分别为 36 2 % (17/ 4 7)、32 7% (16 /4 9) ,5 2 % (2 9/ 5 6 )的子宫颈癌组织至少在一个位点存在LOH。 5 7 1%的子宫颈癌FHIT表达减弱或缺失 ,其中 71 9%存在FHIT基因LOH ,FHIT低表达与FHIT基因LOH之间有相关性 (P <0 0 1)。子宫颈鳞癌组织的LOH发生率及FHIT低表达率均高于腺癌 (6 4 3%vs 14 3% ,6 9 0 %vs 2 1 4 % ,P <0 0 5 )。子宫颈鳞癌LOH发生率及FHIT低表达与组织学分级、FI GO分期均不相关 (P >0 0 5 )。结论　FHIT基因可能在子宫颈鳞癌发生中起重要作用 ,杂合性丢失可能是FHIT基因失活的重要机制     

Numb蛋白在卵巢浆液性肿瘤中的表达及临床意义

目的检测Numb蛋白在卵巢浆液性肿瘤组织中的表达及其临床意义。方法用免疫组织化方法检测Numb蛋白在卵巢浆液性囊腺癌、交界性浆液性囊腺瘤、浆液性囊腺瘤及正常卵巢组织中的表达情况,并与患者的临床病理资料进行分析。结果Numb蛋白在卵巢浆液性囊腺癌中表达阳性率明显低于卵巢正常组织和卵巢浆液性囊腺瘤及交界性浆液性囊腺瘤的阳性率(P0.01),但与肿瘤分化程度、临床病理分期、淋巴结转移及年龄均无明显相关性(P0.05)。结论Numb蛋白在卵巢浆液性囊腺癌中低表达,可能参与浆液性囊腺癌的发生过程。     

应用荧光原位杂交技术检测卵巢浆液性囊腺癌中ZNF217基因拷贝数

目的探讨锌指蛋白217（zinc finger protein 217，ZNF217）基因在卵巢浆液性囊腺癌中20号染色体基因拷贝数改变情况及其临床意义。方法应用荧光原位杂交技术及LSI ZNF217探针对2种卵巢癌细胞株SKOV3、HO-8910和23例卵巢浆液性囊腺癌、10例浆液性囊腺瘤及7份正常卵巢组织进行检测。结果两种卵巢癌细胞株及12例卵巢癌出现ZNF217基因扩增，浆液性囊腺瘤有1例发生了基因的扩增，其余的及正常卵巢组织未出现基因扩增，卵巢癌与卵巢浆液性囊腺瘤、正常卵巢细胞相比较，ZNF217基因拷贝数改变差异有统计学意义（P〈0．05），而低分化的卵巢癌比高分化发生ZNF217基因扩增的几率明显增高（P〈0．05），Ⅲ～Ⅳ期比Ⅰ期的卵巢癌ZNF217基因拷贝数明显增多（P〈0．05）。结论ZNF217基因很可能是卵巢癌发生的促进因子之一，并与卵巢癌分化及预后不良有关。     

卵巢浆液性肿瘤中IQGAP1与E-cadherin表达的检测

目的探讨上皮性钙黏素(E-cadherin)与具有IQ结构域的人Ras GTP激活蛋白相关蛋白1(IQGAP1)在卵巢浆液性肿瘤中的表达及其临床意义。方法分别用免疫组织化学SP法和Western blot法检测20例卵巢浆液性囊腺癌、10例卵巢交界性浆液性囊腺瘤、10例卵巢浆液性囊腺瘤以及10例正常卵巢组织中E-cadherin和IQGAP1的蛋白表达。结果 E-cadherin蛋白在浆液性囊腺瘤中表达最高,明显高于正常卵巢组织和浆液性囊腺癌组织(P0.05),其均值高于交界性囊腺癌,无统计学意义。IQGAP1在卵巢浆液性囊腺癌中表达较正常卵巢组织、良性及交界性肿瘤组织均增高(P0.05);免疫组织化学染色证实IQGAP1在浆液性囊腺癌中以胞膜表达为主,而在良性肿瘤中以胞质表达为主。结论 E-cadherin和IQGAP1在卵巢浆液性瘤高表达,可联合用于卵巢浆液性肿瘤的免疫组化诊断。     

卵巢浆液性交界性肿瘤中clusterin的表达

目的探讨凋亡抑制因子clusterin在卵巢浆液性肿瘤中发生、发展的作用及其与bcl-2、Ki-67表达的关系。方法免疫组化sP法检测clusterin、bcl-2、Ki-67在20例卵巢浆液性囊腺瘤,28例浆液性交界性肿瘤,26例浆液性囊腺癌标本中的表达。结果clusterin在囊腺瘤、交界性肿瘤、囊腺癌中的阳性率分别为40％,67．9％,96．2％。囊腺癌中的clusterin与Ki-67的表达水平均明显高于囊腺瘤（P〈0．05）和SBOT（P〈0．05）。交界性肿瘤中有腹水的患者clusterin阳性率要明显高于无腹水者（P=0．0390）,Ki-67在有腹膜种植的患者阳性率要明显高于无腹膜种植者（P=0．0473）。且两者的表达成正相关。结论clusterin基因可能通过抑制凋亡在卵巢浆液性肿瘤的发生发展中起重要作用。clusterin与Ki-67结合起来分析可能作为鉴别SBOT与浆液性癌的辅助指标。     

ataxin-3在卵巢浆液性肿瘤中的表达及其临床意义

目的检测ataxin-3在卵巢浆液性肿瘤中的表达及临床意义。方法采用免疫组化SP法检测ataxin-3在各组卵巢浆液性肿瘤中表达情况。结果ataxin-3在卵巢低级别浆液性囊腺癌中表达水平明显高于卵巢浆液性囊腺瘤、交界性浆液性囊腺瘤、高级别浆液性囊腺癌中的表达水平,但后三者之间无明显差异(P0.05),ataxin-3表达与卵巢浆液性囊腺癌的分化程度呈负相关,与其它临床病理因素均不存在相关性(P0.05)。结论ataxin-3可能参与卵巢低级别浆液性囊腺癌的发生机制,可能成为其早期诊断指标和治疗靶点。     

WHO卵巢肿瘤的组织学分类

表面上皮间质肿瘤 (surfaceepithelial stromaltumours)　浆液性肿瘤　　恶性　　　腺癌　　　　　　　　　　　　　　　 84 4 1/3　　　表面乳头状腺癌 84 6 1/3　　　腺癌纤维瘤 (恶性腺纤维瘤 ) 90 14 /3　　交界性 84 4 2 /1　　　乳头状囊性肿瘤 84 6 2 /1　　　表面乳头状肿瘤 86 4 3/1　　　腺纤维瘤和囊腺纤维瘤 90 14 /1　　良性　　　囊腺瘤 84 4 1/0　　　乳头状囊腺瘤 84 6 0 /0　　　表面乳头状瘤 84 6 1/0　　　腺纤维瘤和囊腺纤维瘤 90 14 /0　黏液性肿瘤　　恶性　　　腺癌 84 80 /3　　　腺癌纤维瘤 (恶性腺纤维瘤 ) 90 15…     

Aberrant hypermethylation of RASSF1A promoter in ovarian borderline tumors and carcinomas

The newly identified 3p21.3 tumor suppressor gene RASSF1A is inactivated by hypermethylation in variable solid tumors, including those of the lung, breast, prostate, kidney, and ovary. The purpose of this study was to evaluate the methylation status of RASSF1A in various types and stages of ovarian epithelial tumors. We analyzed the DNA methylation status of ovarian tumors using methylation-specific polymerase chain reaction in 54 frozen ovarian tumor tissues and in 97 cases of archival ovarian serous epithelial tumors using a microdissection procedure. Hypermethylation statuses were examined vs clinicopathologic findings. RASSF1A promoter methylation rates in the various types of fresh ovarian tissues were as follows: serous cystadenoma (1/5), serous tumor of borderline malignancy (2/7), serous adenocarcinoma (4/10), mucinous cystadenoma (0/5), mucinous tumor of borderline malignancy (2/7), mucinous adenocarcinoma (3/6), transitional-cell carcinoma (1/3), clear-cell carcinoma (3/3), and malignant müllerian mixed tumor (3/3). In archived serous tumor tissues, RASSF1A promoter hypermethylation was detected in serous cystadenoma (1/6, 16.6%), serous tumor of borderline malignancy (20/41, 48.8%), and in serous adenocarcinoma (25/50, 50%). The status of RASSF1A hypermethylation in borderline tumors was found to correlate statistically with the presence of microinvasion (p=0.002), peritoneal implant (p<0.001), and bilaterality (p=0.019). The RASSF1A promoter hypermethylation was frequently found in borderline tumors and carcinomas, suggesting that RASSF1A promoter hypermethylation may be a useful molecular marker for the early detection of ovarian tumors.     

Loss of heterozygosity at chromosome segment Xq25-26.1 in advanced human ovarian carcinomas

To determine whether a tumor suppressor gene of importance to epithelial ovarian cancer resides on the X chromosome, we examined loss of heterozygosity (LOH) in 123 epithelial ovarian cancer cases. In 54 such cases, we examined LOH at 26 loci on the human X chromosome. In eight cases, we examined LOH in 14 loci and in 61 cases we examined LOH in 13 loci. Matched DNA samples from tumors and corresponding normal tissues were analyzed by polymerase chain reaction (PCR) amplification of microsatellite markers. Frequent losses were found in epithelial carcinomas at the Xq25-26.1 region, including DXS1206(34.5% loss in informative cases), DXS1047(27.7%), HPRT(24.1%), and DXS1062 (33.3%). The minimum overlapping region of LOH was approximately 5 megabases (Mb), flanked by DXS1206(Xq25) and HPRT(Xq26.1). The methylation status of the remaining allele of the androgen receptor gene in the tumors exhibiting LOH at the Xq25-26.1 region suggested that the loss was exclusively in the inactive X chromosome. We next determined whether a significant relationship exists between Xq LOH and other parameters, including histologic grade and/or clinical stage of the tumors and LOH at TP53. The Xq LOH had a significant association with grade 2 to 3 tumors at stages II to IV. Sixteen of 18 cases that showed Xq LOH revealed LOH at the TP53 locus, and 45% of tumors exhibiting LOH at TP53 showed Xq LOH. These results suggest that there may be a tumor suppressor gene or genes which escape inactivation of the X chromosome at Xq25-26.1, and that the loss of the gene(s) at Xq25-26.1 is frequently accompanied by loss of the TP53 or loss of another gene on chromosome 17. These losses may contribute to the progression from a well-differentiated to a more poorly differentiated state or to metastatic aggressiveness. Genes Chromosomes Cancer 20:234–242, 1997. Published 1997 Wiley-Liss, Inc.     

Expression of BRCA1 protein in benign, borderline, and malignant epithelial ovarian neoplasms and its relationship to methylation and allelic loss of the BRCA1 gene

BRCA1 is a putative tumour suppressor gene responsible for a hereditary ovarian cancer syndrome. To clarify the possible involvement of BRCA1 in the development of sporadic ovarian neoplasms, this study analysed the immunohistochemical expression of BRCA1 protein in normal ovarian surface epithelium and 119 epithelial ovarian tumours (19 benign, 24 borderline, and 76 malignant tumours). Loss of heterozygosity (LOH) of BRCA1 was examined using three microsatellite markers to analyse the relationship between BRCA1 expression and alterations of the BRCA1 gene. Methylation of the BRCA1 promoter was also analysed by methylation-specific PCR. In ovarian carcinomas showing heterogeneous expression of BRCA1 protein in the same tumour, LOH and methylation status were analysed using microdissection techniques. Finally, the relationship of BRCA1 expression or its genetic alteration to clinicopathological parameters and patient survival was analysed. Ovarian surface epithelial cells expressed BRCA1 protein. Decreased expression of BRCA1 was found in 16% of benign tumours, 38% of borderline tumours, and 72% of carcinomas. LOH of BRCA1 was demonstrated in no benign tumours, 15% of borderline tumours, and 66% of carcinomas. Methylation of BRCA1 was not detected in benign or borderline tumours, but was present in 31% of carcinomas. Reduced expression of BRCA1 correlated with the presence of gene methylation. The frequency of BRCA1 methylation and LOH was higher in serous carcinomas than in other types. In one of the three serous carcinomas that showed heterogeneous expression of BRCA1, BRCA1-positive borderline-like tumour cells were LOH-positive and methylation-negative, whereas adjacent BRCA1-negative carcinoma cells were LOH-positive and methylation-positive. The prognosis of carcinoma patients did not correlate with BRCA1 expression or genetic status. These findings suggest that reduced expression of BRCA1 protein along with genetic and epigenetic changes of the BRCA1 gene play an important role in the development of sporadic ovarian carcinomas, particularly those of serous histology.     

Incidence of loss of heterozygosity at p53 and BRCA1 loci in serous surface carcinoma

Serous surface carcinoma (SSC) is a neoplasm histologically indistinguishable from typical serous carcinomas that arise from the ovary but has a distinct clinical presentation. It is characterized by widespread peritoneal dissemination at presentation, but the ovaries are grossly normal in size and shape. If the carcinoma involves the ovaries microscopically, the tumor is confined to the surface or is minimally invasive. The recognition of this entity is important, because in some studies it appears to have a poorer prognosis than stage-matched serous cancers of the ovary. Loss of heterozygosity (LOH) of the p53 (17p) and BRCA1 (17q) tumor suppressor genes has been frequently identified in sporadic ovarian carcinomas. Although 17p LOH is correlated with common p53 gene mutations, inactivating mutations of the BRCA1 gene are uncommon in sporadic ovarian cases. In contrast, germline BRCA1 mutations are responsible for some hereditary forms of ovarian cancer, where it has been suggested that germline BRCA1 mutations confer a more favorable prognosis. In this study, 12 sporadic SSC were assessed for the presence of allelic deletions on the p53 and BRCA1 gene loci. DNA from both tumor and normal cells was obtained for LOH studies using tissue microdissection. Polymerase chain reaction (PCR) amplification was performed with the polymorphic DNA markers TP53 (17p13.1/p53 gene) and D17S579 (17q/BRCA1 gene). LOH in the p53 and BRCA1 loci was detected in 62.5% and 66.6% of the cases, respectively. In 50% of tumors informative for both markers, it is possible that an entire chromosome may be lost. In conclusion, we have shown that LOH of the p53 and BRCA1 loci is a frequent event in sporadic SSC, similar to what has been described in the usual form of serous ovarian carcinoma. Mutational analysis will be necessary to determine the exact role of these genes in this group of tumors.     

Loss of heterozygosity in P53, BRCA1, and estrogen receptor genes and correlation to expression of p53 protein in ovarian epithelial tumors of different cell types and biological behavior

Loss of heterozygosity (LOH) of tumor suppressor genes (TSGs) in ovarian epithelial tumors of differing cell types and biological behavior has not been thoroughly investigated. Moreover, there have been conflicting reports correlating LOH of the p53 gene to overexpression of p53 protein. This study evaluated 34 formalin-fixed, paraffin-embedded ovarian epithelial tumors for LOH by polymerase chain reaction (PCR) for the following microsatellite markers: TP53(17p13.1/p53 gene), D17S579(17q/BRCA1 gene), and ESR (6q24-27/estrogen receptor gene). LOH of the TP53 marker was detected in 4 (44%) of 9 informative serous cystadenocarcinomas (SCa) but in 0 of 4 informative clear cell carcinomas (CCa) and 0 of 5 informative serous tumors of low malignant potential (SLMP). LOH of the BRCA1 marker was detected in 5 (83%) of 6 informative SCa, but in 1 (13%) of 8 informative CCa and 1 (14%) of 7 informative SLMP. LOH of the ESR marker was detected in 4 (50%) of 8 informative SCa, but in 0 of 4 informative CCa and 1 (16%) of 6 informative SLMP. p53 protein overexpression was present in 8 of 12 SCa but did not correlate to TP53 LOH. LOH for TP53, D17S579/ BRCA1, and ESR is common in ovarian SCa, and is observed in primary tumors as well as metastases. In contrast, these genetic alterations are less common in CCa and in the biologically less aggressive SLMP tumors. These data suggest different mechanisms of oncogenesis in ovarian epithelial tumors of different cell types and biological behavior.     

Association of allelic loss at the FHIT locus and p53 alterations with tumour kinetics and chromosomal instability in non-small cell lung carcinomas (NSCLCs)

The FHIT gene, located at the FRA3B fragile site of chromosome 3p14.2, encodes a 16.8 kD homologue of the yeast enzyme diadenosine tetraphosphate (Ap(4)A) hydrolase. Frequent allelic losses at this region in various malignancies, including non-small cell lung carcinomas (NSCLCs), imply that FHIT may represent a tumour suppressor gene (TSG). Increasing evidence suggests that multiple TSG impairment has a synergistic effect on tumour growth. The present study of 67 NSCLCs investigated the allelic imbalance (AIm) within the FHIT locus and its relationship with p53 abnormalities, kinetic parameters [proliferative activity or proliferation index (PI) and apoptotic index (AI)], and ploidy status of the carcinomas. Allelic imbalance at FHIT was observed in 35 out of 55 informative (heterozygous: H) cases (64%). Similar frequencies of loss of heterozygosity (LOH) were noticed among squamous cell lung carcinomas and adenocarcinomas. The high percentage of AIm in stage I tumours (71%) is indicative of its relatively early involvement in NSCL carcinogenesis. No association was found between LOH at FHIT, kinetic parameters, and ploidy status of the tumours. Concurrent loss at FHIT and p53 overexpression [FHIT(LOH)/p53(P)] was the most frequent pattern and was observed in 39% of the informative cases. The latter pattern was not associated with smoking, supporting the hypothesis that in patients with a history of tobacco exposure, FHIT allelic loss may not be a consequence of p53 checkpoint defects, but the outcome of tobacco-induced mutagenesis. Statistically significant differences in the presence of FHIT(LOH)/p53(P) and FHIT(LOH)/p53(N) patterns were noted at the proliferative and apoptotic level, whereas ploidy was similar amongst all groups, implying that wild-type (wt) p53 may play a safeguard role against altered FHIT function. However, the possibility of a masking effect from wt p53 cannot be excluded, since the FHIT(LOH)/p53(P) profile demonstrated a higher growth index (GI=PI/AI mean value ratio) than FHIT(H)/p53(P) (32 vs. 8), although this was not significant. Further studies are needed in order to elucidate the role of FHIT and its relationships with other cell-cycle regulatory molecules involved in NSCL carcinogenesis.     

Genetic alterations in gastric cancers from British patients

Twenty-six gastric carcinoma and matching normal tissue DNAs, which had previously been analyzed for alterations of the APC (adenomatous polyposis coli) and MCC (mutated in colorectal cancer) genes were further investigated for the following genetic alterations: mutation and loss of heterozygosity (LOH) of the p53 gene, replication error (RER) and LOH at 12 microsatellite repeat loci, and mutation of the hMSH2 gene. In addition, 9 of the 26 gastric carcinomas were analyzed for genetic alterations using comparative genomic hybridization (CGH). Somatic mutations of the p53 gene were found to be frequent being detected in 31% of gastric carcinomas while LOH at the p53 locus was observed in 37.5% of informative cases. Loss of wild type p53 allele was detected in the majority (7 of 8) tumors found to be harboring a mutation. In the hMSH2 gene, an intronic 4 base pair insertion at 31 base pairs upstream of the beginning of exon 13 was detected in both tumor and normal tissue from one gastric carcinoma case. RER was detected in 11.5% of gastric carcinomas, at one or more microsatellite repeat loci. Of the 12 microsatellite repeat loci analyzed LOH was most frequently observed at D22S351 (30% informative cases) suggesting that a tumor suppressor gene on 22q may be important in gastric carcinogenesis. In support of this, CGH analysis carried out on 9 of the gastric carcinomas identified loss of chromosome 22 in 5 of these tumors.