hMLH1 and hMSH2 expression correlates with allelic imbalance on chromosome 3p in non-small cell lung carcinomas

DNA mismatch repair genes have been implicated in the pathogenesis and predisposition of certain malignancies through a mutator phenotype. In this study, we investigated, in 150 non-small cell lung carcinomas, the expression levels of hMLH1 and hMSH2 proteins in relation to loss of heterozygosity on chromosomes 3p and 2p, the mutational status of these genes' promoters and the hot spot exons. We have demonstrated that 88 of 150 (58.6%) tumor specimens had reduced expression levels of the hMLH1 protein, whereas 85 of 147 (57.8%) specimens had reduced expression levels of the hMSH2 protein. Reduced expression levels of both proteins were observed in 51 of 150 (34%) specimens. In adenocarcinomas, the reduction of hMSH2 expression was more frequently observed than that of hMLH1 (P<0.003), whereas in squamous cell carcinoma of the lung hMLH1 expression was more frequently reduced than hMSH2 (P<0.006). Reduced expression of hMLH1correlated with allelic imbalance on loci D3S1289 (P<0.0002) and D2S391 (P<0.05). It is of note that an inverse correlation was found between hMSH2 reduced expression and loss of heterozygosity at locus D3S1300 (P = 0.016). In addition, hMLH1 reduced expression was more frequently associated with heavy smokers, assessed by daily tobacco uptake (P = 0.018) and total smoking exposure (pack-years; P<0.05). In addition, a correlation between hMLH1 reduced expression and nodal metastasis in squamous cell carcinoma of the lung was observed (P = 0.015). No mutations were identified in the promoters or exons examined in these two genes. These findings indicate that hMLH1 and hMSH2 gene inactivation is a common event in the development of non-small cell lung carcinoma and allelic loss seems to be a major genetic event involved in hMLH1 silencing. In addition, we propose that a putative negative regulator of hMSH2 gene may be located at the locus 3p14.     

Allelic imbalance at the DNA mismatch repair loci,hMSH2, hMLH1, hPMS1, hPMS2 and hMSH3, in squamous cell carcinoma of the head and neck

BACKGROUND: Squamous cell carcinoma of the head and neck (SCCHN) is one of the 10 most frequently occurring cancers in the world. Defective mismatch repair, as exhibited by the phenomenon of microsatellite instability, has been observed in SCCHN although no reports of mismatch repair gene mutations or altered protein expression have been published. In a variety of microsatellite instability (MSI) positive cancers where mutations in the mismatch repair (MMR) genes were not observed, allelic imbalance at the loci of the MMR genes was prevalent. OBJECTIVE: To investigate whether allelic imbalance at the MMR genetic loci contributes to the development of SCCHN. MATERIALS AND METHODS: 35 matched normal/tumour SCCHN pairs were studied using 29 microsatellite markers located within and adjacent to six known DNA mismatch repair genes. In addition, mutational analysis and protein expression of hMSH2 and hMLH1 were investigated. RESULTS AND CONCLUSIONS: We demonstrated that 36 and 17% of the analysed SCCHN specimens exhibited allele imbalance at the hMLH1 and hMSH3 genetic loci, respectively. Allelic instability at these two loci was found to be correlated with the MSI status of the SCCHN tumours. Allelic instability was found to be uncommon at the other MMR gene loci analysed. One mutation was found in hMSH2 and none in hMLH1 in this series of tumours. 23 of 24 (96%) of the examined SCCHN tumours showed reduced expression of either hMSH2 or hMCH1 genes. Allelic instability in the MMR genes, hMLH1 and hMSH3, is proposed to be involved in the aetiology of SCCHN tumours.     

Allelic losses and DNA methylation at DNA mismatch repair loci in sporadic colorectal cancer

Normal and tumor DNA samples of 35 patients with sporadic colorectal carcinoma were analyzed for microsatellite alterations at 12 markers linked to mismatch repair loci: hMLH1, hMSH2, hMSH3, hMSH6, hPMS1 and hPMS2. Remarkably, no correlation was observed between the replication error phenotype (RER+) and allelic losses at these loci. Hemizygous deletions, seen in 6/35 (17%) informative cases at hMLH1, 4/27 (15%) at hMSH2/hMSH6 and 6/34 (18%) at hMSH3, were rarely found in RER+ tumors. Since mismatch repair protein components act in molecular complexes of defined stoichiometry we propose that hemizygous deletion of the corresponding loci may be involved in colorectal tumorigenesis through defects in cellular functions other than replication error correction. The analysis of the methylation status of the promoter region of hMLH1 revealed that methylation might be an important mechanism of this locus inactivation in RER+ sporadic colorectal cancer.      

Frequent loss of heterozygosity at the DNA mismatch-repair loci hMLH1 and hMSH3 in sporadic breast cancer

To study the involvement of DNA mismatch-repair genes in sporadic breast cancer, matched normal and tumoral DNA samples of 22 patients were analysed for genetic instability and loss of heterozygosity (LOH) with 42 microsatellites at or linked to hMLH1 (3p21), hMSH2 (2p16), hMSH3 (5q11-q13), hMSH6 (2p16), hPMS1 (2q32) and hPMS2 (7p22) loci. Chromosomal regions 3p21 and 5q11-q13 were found hemizygously deleted in 46% and 23% of patients respectively. Half of the patients deleted at hMLH1 were also deleted at hMSH3. The shortest regions of overlapping (SRO) deletions were delimited by markers D3S1298 and D3S1266 at 3p21 and by D5S647 and D5S418 at 5q11-q13. Currently, the genes hMLH1 (3p21) and hMSH3 (5q11-q13) are the only known candidates located within these regions. The consequence of these allelic losses is still unclear because none of the breast cancers examined displayed microsatellite instability, a hallmark of mismatch-repair defect during replication error correction. We suggest that hMLH1 and hMSH3 could be involved in breast tumorigenesis through cellular functions other than replication error correction.     

DNA mismatch repair genes hMLH1, hMSH2, and hMSH6 are not inactivated in bronchioloalveolar carcinomas of the lung.

BACKGROUND: Defective DNA mismatch repair (MMR) appears to be rare in nonsmall cell carcinomas of the lung. Defective DNA MMR results from genetic or epigenetic alterations that inactivate the DNA MMR genes hMLH1 or hMSH2, and rarely hMSH6. The loss of normal DNA MMR is thought to promote tumorigenesis by accelerating the accumulation of mutations in oncogenes and tumor suppressor genes. Inactivation of hMLH1, hMSH2, and hMSH6 is observed as a loss of expression of these proteins by immunohistochemistry. Bronchioloalveolar carcinoma is a subtype of adenocarcinoma with distinctive clinical and pathologic features. MATERIALS AND METHODS. An immunohistochemical study was performed on paraffin embedded sections of 33 bronchioloalveolar carcinomas (20 nonmucinous and 13 mucinous) for hmlh1, hmsh2, and hmsh6 proteins. RESULTS All the tumors showed normal expression of hmlh1, hmsh2, and hmsh6. CONCLUSIONS: These findings suggest that defective DNA MMR due to inactivation of hMLH1, hMSH2, or hMSH6 does not play a significant role in the pathogenesis of bronchioloalveolar carcinomas.     

Roles of mismatch repair proteins hMSH2 and hMLH1 in the development of sporadic breast cancer

Defects in mismatch repair (MMR) genes, particularly the hMSH2 and hMLH1 genes, are associated with a variety of cancers including sporadic breast cancer. However, whether or not patient clinical background, e.g. age, progesterone receptor (PR), estrogen receptor (ER), tumor progression and stage, chemotherapy history, and menopausal status, influences MMR status is not understood. To address these issues, 83 archival breast cancer specimens were examined for expression of hMSH2 and hMLH1 by immunohistochemistry and the relationship between MMR protein expression and patient clinical background was analyzed. We detected lack of or reduced expression of hMSH2 and hMLH1 in 23 (27.7%) and 26 cases (31.3%), respectively, and hypermethylation of the hMLH1 promoter accounted for the majority of the cases with reduced expression of hMLH1. Statistical analysis revealed that (i) reduced expression of hMLH1 and hMSH2 seemed to confer advantage for the progression of breast tumors to more advanced stages; (ii) attenuated expression of hMLH1 correlated with history of chemotherapy, but not with age, menopause, or the status of PR and ER; (iii) hypermethylation of the hMLH1 promoter was linked with clinical stage and lymphatic metastasis. These analyses indicate that defective expression of MMR genes is closely associated with the development of sporadic breast cancer.     

ＤＮＡ错配修复基因ｈＭＬＨ１与肿瘤及化疗耐药相关性的研究进展

ＤＮＡ是生命活动最重要的遗传物质。ＤＮＡ复制产生的误差（碱基错配）是一种重要的损伤。若ＤＮＡ损伤得不到修复,将会导致基因的突变,其中一部分突变有利于物种的进化,而另一部分将导致细胞恶化和死亡。ＤＮＡ错配修复系统（ｍｉｓｍａｔｃｈｒｅｐａｉｒｓｙｓｔｅｍ,ＭＭＲ）是人体细胞中存在的一种能识别并修复ＤＮＡ碱基错配的安全保障系统。到目前为止,已从人体细胞中共分离克隆到９种ＭＭＲ基因。ｈＭＬＨ１基因是一系列ＤＮＡ错配修复基因中最重要的一种,也是ＭＭＲ系统的重要成分,其甲基化可导致ＭＭＲ缺陷。近年来的研究发现,ｈＭＬＨ１的失活与肿瘤发生发展有关,并可能因此导致肿瘤对某些抗肿瘤药物耐药。     

错配修复基因hMLH1和hMSH2在散发性大肠癌中的表达及其意义

目的 探讨错配修复基因hMLH1和hMSH2在散发性大肠癌(SCC)组织中的表达及其临床意义.方法 采用免疫组化Max Vision二步法对63例SCC标本中的癌组织、距癌灶3 cm以外的癌旁组织、距癌灶10 cm以外的正常组织中hMLH1和hMSH2蛋白的表达进行检测.结果 hMLH1蛋白在63例正常大肠组织、癌旁组织和SCC组织中的阳性表达率分别为95.2%、85.7%和81.0%,hMLH1蛋白在SCC组织中的阳性表达率明显低于正常大肠组织(P＜0.05).hMSH2蛋白在63例正常大肠组织、癌旁组织和SCC组织中的阳性表达率分别为76.2%、66.7%和52.4%,hMSH2蛋白在SCC组织中的阳性表达率明显低于正常大肠组织(P＜0.01).hMLH1蛋白在＜60岁的SCC患者组织中的阳性表达率(100%)明显高于≥60岁的SCC患者组织(75.0%,P＜0.05),在有淋巴结转移的SCC组织中的阳性表达率(50.0%)明显低于无淋巴结转移的SCC组织(93.3%,P＜0.05).hMSH2蛋白在＜60岁的SCC患者组织中的阳性表达率(80.0%)明显高于≥60岁的SCC患者组织(43.8%,P＜0.05),在癌组织浸润至肠壁浆膜层SCC组织中的阳性表达率(61.5%)明显高于浸润至黏膜下层和肌层的SCC组织(37.5%,P＜0.05).SCC组织中hMLH1和hMSH2蛋白的表达呈正相关关系(r=0.254,P＜0.01).结论 hMLH1和hMSH2蛋白在SCC组织中的表达均有一定的缺失,并且与患者的年龄、淋巴结转移和癌组织浸润的范围有关.hMLH1和hMSH2基因可以作为临床预测和判断SCC发生和发展有用的实验室指标.     

Association between DNA mismatch repair gene polymorphisms and platinum-based chemotherapy toxicity in non-small cell lung cancer patients

Background: Chemotherapy toxicity is a serious problem from which non-small cell lung cancer (NSCLC) patientssuffer. The mismatch repair (MMR) system is associated with platinum-based chemotherapy toxicity in NSCLC patients.In this study, we aimed to investigate the relationship between genetic polymorphisms in the MMR pathway andplatinum-based chemotherapy toxicity in NSCLC patients.Methods: A total of 220 Chinese lung cancer patients who received at least two cycles of platinum-based chemotherapywere recruited for this study. Toxicity was evaluated in each patient after two cycles of chemotherapy. A totalof 44 single nucleotide polymorphisms were selected to investigate their associations with platinum-based chemotherapytoxicity.Results: MutS homolog 2 (MSH2) rs6544991 [odds ratio (OR) 2.98, 95% confidence interval (CI) 1.20–7.40, P = 0.019]was associated with gastrointestinal toxicity in the dominant model; MSH3 rs6151627 (OR 2.38, 95% CI 1.23–4.60,P = 0.010), rs6151670 (OR 2.05, 95% CI 1.07–3.93, P = 0.031), and rs7709909 (OR 2.38, 95% CI 1.23–4.64, P = 0.010)were associated with hematologic toxicity in the dominant model. Additionally, MSH5 rs805304 was significantly associatedwith overall toxicity (OR 2.21, 95% CI 1.19–4.09, P = 0.012), and MSH5 rs707939 was significantly associated withboth overall toxicity (OR 0.42, 95% CI 0.23–0.76, P = 0.004) and gastrointestinal toxicity (OR 0.44, 95% CI 0.20–0.96,P = 0.038) in the dominant model.Conclusion: Genetic polymorphisms in the MMR pathway are potential clinical markers for predicting chemotherapytoxicity in NSCLC patients.     

Genetic and epigenetic modification of mismatch repair genes hMSH2 and hMLH1 in sporadic breast cancer with microsatellite instability

Breast cancer is the most common cancer in women, but its pathogenesis is still unclear. Microsatellite instability (MSI) has been identified in breast cancer cells, suggesting an association with mismatch repair defects. To test this hypothesis, we investigated MSI, protein expression of hMSH2 and hMLH1, as well as genetic and epigenetic modifications of these two genes in 32 sporadic breast tumors. MSI was identified in 15 cases. Immunohistochemistry analysis revealed that all MSI cases but one had lower than normal expression of hMSH2 (nine cases), hMLH1 (12 cases), or both (seven cases). In tumors with MSI, both genetic and epigenetic modifications of these mismatch repair genes were also identified. Eight cases harbored mutations or polymorphisms in hMSH2 and hMLH1, and 10 exhibited hypermethylation in the promoter region of hMLH1. These results suggest that both genetic and epigenetic alterations of hMSH2 and especially of hMLH1 contribute to genomic instability and tumorigenesis in sporadic breast cancer.     

Immunohistochemical analysis of expression and allelotype of mismatch repair genes (hMLH1 and hMSH2) in bladder cancer

Mutation of human homologues of DNA mismatch repair (MMR) genes in tumours has been shown to be associated with the phenomenon of microsatellite instability (MSI). Several studies have reported the occurrence of MSI in bladder cancer, but evidence of involvement of MMR genes in the pathogenesis of this cancer is still unclear. We therefore utilized quantitative immunohistochemical (IHC) image analysis and PCR-based allelotype analysis to determine hMLH1 and hMSH2 genes alteration in a cohort of Egyptian bladder cancer samples. IHC analysis of 24 TCC and 12 SCC revealed marked- intra and intertumour heterogeneity in the levels of expression of the two MMR proteins. One TCC lost MLH1 expression and one lost MSH2, (1/24, 4%), and one SCC lost MSH2 (1/12, 8%). A large proportion of analysed tumours revealed a percentage positivity of less than 50% for MLH1 and MSH2 expression (44% and 69%, respectively). Complete loss of heterozygosity in three dinucleotide repeats lying within, or in close proximity to, hMLH1 and hMSH2 was rare (2/57, (4%) for MLH1; and 1/55, (2%) for MSH2), however allelic imbalance was detected in 11/57 (hMLH1) and 10/55 (hMSH2) at any of the informative microsatellite loci. These alterations in structure and expression of DNA MMR genes suggest their possible involvement in the tumorigenesis and/or progression of bladder cancer.     

DNA alterations at proto-oncogene loci and their clinical significance in operable non-small cell lung cancer

DNA from tumor samples of 54 patients with operable non-small cell lung cancer (NSCLC) was analyzed to determine whether proto-oncogene alterations could be correlated with the clinical behavior of lung cancer. Among seven proto-oncogenes tested, changes in the copy number of Ha-ras, c-myc and c-raf-1 were found in only seven tumors. Most of them were epidermoid carcinomas without lymph node involvement (N0). In spite of a localized disease with complete surgical resection, six of these patients relapsed within a mean disease-free interval (DFI) of only 6.5 months. There is a significant correlation between DNA alterations at proto-oncogene loci and clinical relapse within 12 months of surgical resection (P less than 0.025).     

Microsatellite instability and protein expression of the DNA mismatch repair gene, hMLH1, of lung cancer in chromate-exposed workers

Our previous studies of lung cancer in chromate-exposed workers (chromate lung cancer) have revealed that the frequency of replication error (RER) in chromate lung cancer is very high. We examined whether the RER phenotype of chromate lung cancer is due to an abnormality of DNA mismatch repair protein. We investigated the expression of a DNA mismatch repair gene, hMLH1, and hMSH2 proteins using immunohistochemistry and microsatellite instability (MSI) in 35 chromate lung cancers and 26 nonchromate lung cancers. Lung cancer without MSI or with MSI at one locus was defined as "RER(-)," lung cancer with MSI at two loci was defined as "RER(+)," and lung cancer with MSI at three or more loci was defined as "RER(++)." The repression rate of hMLH1 and hMSH2 proteins in chromate lung cancer was significantly more than that of nonchromate lung cancer (hMLH1: 56% vs. 20%, P = 0.006, hMSH2: 74% vs. 23%, P < 0.0001). In chromate lung cancer, the repression rate for hMLH1 was 43% in RER(-), 40% in RER(+), and 90% in the RER(++) group. The repression rate of hMLH1 protein in the RER(++) group was significantly higher than that in the RER(-) and RER(+) groups (P = 0.039). The inactivation of hMLH1 expression strongly correlated with the microsatellite high instability phenotype in chromate lung cancer. The genetic instability of chromate lung cancer is due to the repression of hMLH1 protein.     

Role of the hMLH1 DNA mismatch repair protein in fluoropyrimidine-mediated cell death and cell cycle responses.

DNA mismatch repair (MMR) is an efficient system for the detection and repair of mismatched and unpaired bases in DNA. Deficiencies in MMR are commonly found in both hereditary and sporadic colorectal cancers, as well as in cancers of other tissues. Because fluorinated thymidine analogues (which through their actions might generate lesions recognizable by MMR) are widely used in the treatment of colorectal cancer, we investigated the role of MMR in cellular responses to 5-fluorouracil and 5-fluoro-2'-deoxyuridine (FdUrd). Human MLH1(-) and MMR-deficient HCT116 colon cancer cells were 18-fold more resistant to 7.5 microM 5-fluorouracil (continuous treatment) and 17-fold more resistant to 7.5 microM FdUrd in clonogenic survival assays compared with genetically matched, MLH1(+) and MMR-proficient HCT116 3-6 cells. Likewise, murine MLH1(-) and MMR-deficient CT-5 cells were 3-fold more resistant to a 2-h pulse of 10 microM FdUrd than their MLH1(+) and MMR-proficient ME-10 counterparts. Decreased cytotoxicity in MMR-deficient cells after treatment with various methylating agents and other base analogues has been well reported and is believed to reflect a tolerance to DNA damage. Synchronized HCT116 3-6 cells treated with a low dose of FdUrd had a 2-fold greater G(2) cell cycle arrest compared with MMR-deficient HCT116 cells, and asynchronous ME-10 cells demonstrated a 4-fold greater G(2) arrest after FdUrd treatment compared with CT-5 cells. Enhanced G(2) arrest in MMR-proficient cells in response to other agents has been reported and is believed to allow time for DNA repair. G(2) cell cycle arrest as determined by propidium iodide staining was not a result of mitotic arrest, but rather a true G(2) arrest, as indicated by elevated cyclin B1 levels and a lack of staining with mitotic protein monoclonal antibody 2. Additionally, p53 and GADD45 levels were induced in FdUrd-treated HCT116 3-6 cells. DNA double-strand break (DSB) formation was 2-fold higher in MMR-proficient HCT116 3-6 cells after FdUrd treatment, as determined by pulsed-field gel electrophoresis. The formation of DSBs was not the result of enhanced apoptosis in MMR-proficient cells. FdUrd-mediated cytotoxicity was caused by DNA-directed and not RNA-directed effects, because administration of excess thymidine (and not uridine) prevented cytotoxicity, cell cycle arrest, and DSB formation. hMLH1-dependent responses to fluoropyrimidine treatment, which may involve the action of p53 and the formation of DSBs, clearly have clinical relevance for the use of this class of drugs in the treatment of tumors with MMR deficiencies.     

人非小细胞肺癌中FHIT等位基因缺失和突变的研究

目的　探讨FHIT等位基因缺失、突变在肺癌发生、发展中的作用。方法　应用PCR SSCP和DNA序列分析方法对 3 5例人非小细胞肺癌和 4个肺癌细胞株中FHIT基因的 4个外显子 (外显子 3、4、5、8)和微卫星D3S13 0 0、D3S13 12、D3S13 13进行研究 ,并以远癌肺组织和 10例肺良性病变组织做对照。结果　在 3 5例肺癌中 ,2 2例肺癌发生了一个或两个以上的FHIT等位基因缺失 ,缺失率为 62 .86% ( 2 2 /3 5 )。在鳞癌中 ,FHIT等位基因缺失率 ( 88.2 4% ,15 /17)明显高于腺癌 ( 3 8.89% ,7/18) (P <0 .0 1) ;在吸烟患者中 ( 76.19% ,16/2 1)亦明显高于不吸烟患者 ( 4 2 .86% ,6/14 ) (P <0 .0 5 )。而FHIT等位基因缺失与肺癌的细胞分化程度、P TNM分期、原发肿瘤大小、部位、患者性别、年龄及有无转移均无明显关系 (P >0 .0 5 )。Lewis肺癌、A5 49细胞株亦有FHIT基因部分缺失。 4例肺癌组织具有微卫星灶D3S13 12点突变 ,经DNA序列分析显示均为D3S13 12微卫星灶基因的 87位点密码子发生了CT点突变。结论　FHIT基因异常主要以等位基因的缺失为主 ,而点突变发生率较低。FHIT等位基因缺失主要发生在肺鳞癌和吸烟患者中 ,且FHIT基因可能为烟草致肺癌的靶基因 ,其等位基因缺失可能是肺癌的早期分子事件。     

hMLH1基因启动子甲基化与非小细胞肺癌细胞顺铂耐药方面的研究

背景与目的：hMLH1启动子甲基化是肺癌发生、发展的因素之一,但与肺癌细胞耐药方面的研究尚未见报道,本研究旨在探讨是否能通过去甲基化作用恢复hMLH1基因表达从而逆转A549/DDP细胞对顺铂的耐药。方法：RT-PCR检测A549及A549/DDP细胞的hMLH1表达情况,及5-氮杂-2＇-脱氧胞苷（5-Aza-2＇-eoxycytidine,5-Aza-CdR）干预A549/DDP细胞后hMLH1表达情况;MSP检测A549、A549/DDP细胞及5-Aza-CdR干预A549/DDP细胞后hMLH1甲基化状态。MTT试验、Hoechst33258染色、流式细胞仪（FCM）分别观察5-Aza-CdR干预前后顺铂对A549/DDP细胞抑制率、凋亡的形态学变化和凋亡指数。结果：hMLH1mRNA在A549中的表达高于A549/DDP细胞;A549细胞hMLH1为非甲基化状态,A549/DDP细胞为部分甲基化状态,经5-Aza-CdR去甲基作用后hMLH1呈非甲基化状态;A549组、A549/DDP组、经10μmol/L5-Aza-CdR干预后的A549/DDP组经顺铂作用后的IC50值分别为（4.7&#177;0.7）、（30.1&#177;1.8）和（6.9&#177;0.6）μmol/L;5-Aza-CdR干预后的A549/DDP细胞经顺铂作用后,比单用顺铂抑制A549/DDP细胞的凋亡形态学改变明显,凋亡小体以及核固缩现象增多。结论：hMLH1甲基化可能参与了A549/DDP细胞的顺铂耐药过程;5-Aza-CdR能抑制hMLH1甲基化,恢复hMLH1表达,并能增强顺铂对A549/DDP细胞增殖抑制和凋亡。     

错配修复基因hMSH2和hMLH1在结直肠癌组织中的表达及临床意义

  目的   评价hMLH1和hMSH2蛋白在结直肠癌中的表达及意义。   方法   选取2009年1月至2011年12月经病理学确诊的结肠癌手术切除标本72例, 所有患者在术前均未接受过放疗或化疗, 内镜活检取正常肠黏膜上皮25例。免疫组织化学检测hMLH1和hMSH2蛋白表达情况。   结果   结直肠癌组织中hMSH2缺失率为88.9% (64/72), 高于正常肠组织中hMSH2蛋白缺失率28.0% (7/25)。hMSH2蛋白缺失率随T分期增加而增加, 但差异无统计学意义(χ2=37.622, P < 0.001);hMSH2蛋白缺失率与N分期相关, 有淋巴结转移者的hMSH2蛋白缺失40例, 缺失率达97.6% (40/41), 无淋巴结转移患者的hMSH2蛋白缺失率为77.4% (24/31, χ2=7.251, P=0.007)。而hMLH1蛋白缺失率为90.3% (65/72), 高于正常组肠组织中hMLH1蛋白缺失率为32.0% (8/25, χ2=33.847, P < 0.001), 但与肿瘤部位、分期、分化程度均无关。   结论   在结直肠癌组织中存在错配修复基因hMSH2和hMLH1蛋白缺失, 且表达缺失与肿瘤分期有关。通过免疫组织化学方法检测hMLH1和hMSH2蛋白表达可以简便、准确地发现错配修复基因的突变, 从而对其后期的治疗和预后判断有参考价值。