Alterations of transforming growth factor beta receptor II, insulin growth factor receptor II genes in microsatellite unstable prostate carcinomas

DNA from 45 primary prostate tumors and corresponding normal tissues were analyzed to detect whether the alterations of transforming growth factor beta receptor II (TGFbetaRII) and insulin growth factor receptor II (IGFRII) are associated with microsatellite instability (MSI). We identified that 25 tumors were microsatellite unstable (55%). The remaining 20 tumors are found to be microsatellite stable. Loss of heterozygosity (LOH) was also tested at various loci. Results indicate that in case of TGFbetaRII, the rate of frame-shift mutation depends on the number of polyadenine [poly(A)] tracts. Twelve percent of the tumors had frame-shift alteration at BAT-RII locus which has 10 poly(A) repeats. Twenty percent of the tumors had frame-shift at BAT-25 locus which has 25 poly(A) repeats. In addition, IGFRII gene was examined for the presence of mutation in the repetitive sequences. Seven of the 25 tumors showed deletion of a G within eight poly(G) repeats. Besides these changes there were two tumors which showed a novel insertion of A within this poly(G) repeat making a change in 9 samples (R4, 36%). On the other hand, 4 tumors showed changes within the 5CT repeats. In addition, 3 tumors showed another novel insertion of C within the CT repeats.     

Mutational analysis of transforming growth factor-beta receptor type II and Smad3 tumor suppressor genes in prolactinomas

The presence of transforming growth factor-beta receptor type II and Smad3 gene abnormality was examined in human prolactinomas by single-strand conformation polymorphism screening for gene abnormality and band shift in tumor tissue and peripheral blood samples obtained from 14 patients treated for prolactinoma. Direct sequencing of exon 4 of the transforming growth factor-beta receptor type II gene, which showed a band shift by single-strand conformation polymorphism, disclosed a single nucleotide polymorphism (rs2228048) (alleles A/G; average allele frequency, G:0.817, A:0.183) and not an active mutation. Seven of the 14 cases showed base substitution (G → A) of the single nucleotide polymorphism. Two of these 7 cases showed base substitution (G → A) in the blood sample in accordance with neoplastic transformation. Direct sequencing of exon 2 of the Smad3 gene, which showed band shift by single-strand conformation polymorphism, disclosed single nucleotide polymorphism (rs1065080) (alleles C/T; average allele frequency, C:0.947, T:0.053) and no active mutation. Four of the 14 cases showed base substitution (C → T) of the single nucleotide polymorphism. Blood samples were available for 2 of these 4 cases, and 1 of these 2 cases showed base substitution (C → T) in accordance with neoplastic transformation. Estimation of the drug sensitivity of pituitary adenoma based on analysis of peripheral blood cells needs special care.     

Absence of mutations in the transforming growth factor-beta type II receptor in sporadic lung cancers with microsatellite instability and rare H-ras1 alleles

The transforming growth factor-beta type II receptor (RII) is commonly mutated in colon and gastric cancers with microsatellite instability (MI). We utilized our series of lung cancers with MI and rare alleles of the H-ras1 gene to determine the association between MI and RII mutations and searched the entire RII coding region in 33 lung cancers with MI by polymerase chain reaction-single-strand conformation polymorphism analysis. We found no mutations, and these data support other recent evidence that RII mutations rarely occur except in colon and gastric tumors with MI.      

Microsatellite instability, Epstein-Barr virus, mutation of type II transforming growth factor beta receptor and BAX in gastric carcinomas in Hong Kong Chinese

Microsatellite instability (MI), the phenotypic manifestation of mismatch repair failure, is found in a proportion of gastric carcinomas. Little is known of the links between MI and Epstein-Barr virus (EBV) status and clinicopathological elements. Examination of genes mutated through the MI mechanism could also be expected to reveal important information on the carcinogenic pathway. Seventy-nine gastric carcinomas (61 EBV negative, 18 EBV positive) from local Hong Kong Chinese population, an intermediate-incidence area, were examined. Eight microsatellite loci, inclusive of the A10 tract of type II transforming growth factor beta receptor (TbetaR-II), were used to evaluate the MI status. MI in the BAX and insulin-like growth factor II receptor (IGF-IIR) genes were also examined. High-level MI (>40% unstable loci) was detected in ten cases (12.7%) and low-level MI (1-40% unstable loci) in three (3.8%). High-level MI was detected in two EBV-associated cases (11%) and the incidence was similar for the EBV-negative cases (13%). The high-level MIs were significantly associated with intestinal-type tumours (P = 0.03) and a more prominent lymphoid infiltrate (P = 0.04). Similar associations were noted in the EBV-positive carcinomas. The high-level MIs were more commonly located in the antrum, whereas the EBV-associated carcinomas were mostly located in body. Thirteen cardia cases were negative for both high-level MI and EBV. All patients aged below 55 were MI negative (P = 0.049). Of the high-level MIs, 80% had mutation in TbetaR-II, 40% in BAX and 0% in IGF-IIR. Of low-level MIs, 33% also had TbetaR-II mutation. These mutations were absent in the MI-negative cases. Of three lymphoepithelioma-like carcinomas, two cases were EBV positive and MI negative, one case was EBV negative but with high-level MI. In conclusion, high-level MIs were present regardless of the EBV status, and were found in a particular clinicopathological subset of gastric carcinoma patient. Inactivation of important growth regulatory genes observed in these carcinomas confirms the importance of MI in carcinogenesis.     

Frequent frameshift mutations of RIZ in sporadic gastrointestinal and endometrial carcinomas with microsatellite instability

Many lines of evidence suggest that the retinoblastoma protein interacting zinc finger gene RIZ is a strong candidate for the tumor suppressor locus on 1p36, a region commonly deleted in many human cancers with chromosomal instability. In addition, a role for RIZ in tumors of the microsatellite instability pathway is suggested by frequent frameshift mutations in hereditary non-polyposis colorectal carcinomas. Here we studied RIZ mutations in sporadic cancers with microsatellite instability. Frameshift mutations in the two coding polyadenosine tracks of RIZ were found in 19 (48%) of 40 gastric carcinomas, 6 (33%) of 18 endometrial carcinomas, 14 (26%) of 51 of colorectal carcinomas, and 7 (54%) of 13 cell lines. Eleven tumor tissues showed biallelic inactivation of RIZ. In contrast, no frameshift mutations were found in 70 microsatellite stable tumors. These results suggest an important role for RIZ in sporadic cancers with microsatellite instability.     

Microsatellite instability and expression of mismatch repair genes in sporadic endometrial cancer coexisting with colorectal or breast cancer

The molecular background of sporadic endometrial cancer coexisting with colorectal or breast cancer is not clear. We investigated microsatellite instability (MSI) and status of mismatch repair (MMR) gene product, MLH1, MSH2 and MSH6, in 63 sporadic endometrial cancers coexisting with colorectal or breast cancer. Sixteen sporadic endometrial cancers with colorectal cancers (EC), 26 sporadic endometrial cancers with breast cancer (EB) and 21 endometrial cancers without a coexisting cancer (control) were analyzed. EC had the highest frequency of MSI among the 3 groups (EC, 69%; EB, 23%; and control, 43%). Incidence of low-frequency MSI was significantly higher in EC (38%). Among endometrial cancer cases diagnosed before age 50, all high-frequency MSI (MSI-H) cases belonged to EC. Interestingly, incidence of MSI-H was significantly higher in tamoxifen-non-treated cases (75%) than that of treated cases (14%). These results suggest that alterations in MMR genes appear to be involved in carcinogenesis of EC but seem to be uncommon in those of EB. Presence of MSI in sporadic endometrial cancer may be a useful marker to predict the risk of colorectal cancer.     

Mutational analysis of the transforming growth factor beta receptor type I gene in primary non-small cell lung cancer

Transforming growth factor-β receptor-dependent signals are critical for cell growth and differentiation and are often disrupted during tumorigenesis. The entire coding region of TGFβRI and flanking intron sequences from 53 primary non-small cell lung cancer (NSCLC) tissues were examined for alterations using SSCP and direct sequencing. No somatic point mutations other than two silent mutations and a polymorphism were found in the TGFβRI gene. The two silent mutations located at codon 344 (AAT to AAC) and codon 406 (TTA to CTA), respectively, and the polymorphism was at the 24th base of intron 7 (G to A). To investigate whether the presence of this polymorphism is associated with NSCLC, we determined its allele distribution in all the 53 carcinomas and 89 normal controls. Interestingly, we found that the subjects with homozygous genotype A/A displayed more than 3-fold increased risk of developing NSCLC than the common wild genotype G/G. As the first report, the present study showed that TGFβRI gene is not a frequent site of spontaneous mutational inactivation while the detected polymorphism is frequent in the pathogenesis of NSCLC.     

Mutational analysis of the transforming growth factor beta receptor type II gene in hereditary nonpolyposis colorectal cancer and early-onset colorectal cancer patients.

Somatic mutations in the transforming growth factor beta receptor type II (TGF-beta RII) gene have been observed in various human cancers showing microsatellite instability. Most of the mutations observed were additions or deletions of the mononucleotide repeat sequence present in TGF-beta RII coding region, suggesting that the TGF-beta RII may be a target gene of genomic instability in tumorigenesis. Recently, we reported germ-line frameshift mutations in the mononucleotide repeat sequence of the hMSH6 gene, which is believed to be one of the target genes of genomic instability in tumorigenesis, suggesting the possibility of germ-line mutation in mononucleotide repeat sequences. Moreover, one case of germ-line mutation in the TGF-beta RII gene was identified in a hereditary nonpolyposis colorectal cancer (HNPCC) kindred, indicating the involvement of TGF-beta RII inactivation in tumorigenesis of HNPCC. However, germ-line mutation analysis of all of the coding sequences and the mononucleotide repeat sequence of the TGF-beta RII in HNPCC patients has not yet been fully elucidated. Therefore, to further investigate the presence of germ-line mutations, we screened all of the coding region sequences and mononucleotide repeat sequence of TGF-beta RII from 35 HNPCC, 44 suspected HNPCC, and 45 sporadic early-onset colorectal cancer patients. However, no pathogenic mutations other than silent mutations, introgenic mutation, and polymorphisms were identified. Two silent mutations at codons 309 (ACG to ACA) and 340 (CAT to CAC) in the kinase domain located in exon 4 were detected. A 1-bp cytidine deletion was observed 6 bases from the 3' end of intron. Two polymorphisms were identified at codon 389 (AAC to AAT) and at the fourth-to-last base in intron 3. The polymorphism at codon 389 was more frequent in HNPCC (20%; 7 of 35) and suspected HNPCC patients (18%; 8 of 44) than in nonmalignant control group (10%; 5 of 50). Moreover, the frequency was significantly higher in early-onset colorectal cancer patients (31%; 14 of 45). This is the first report of a different frequency of polymorphism in HNPCC, suspected HNPCC, early-onset colorectal cancer patients, and healthy normal individuals. This result suggests that: (a) germ-line mutation of the TGF-beta RII gene may be a rare event during tumorigenesis in HNPCC and sporadic early-onset colorectal cancer; (b) the mononucleotide repeat sequence of the TGF-beta RII gene is an apparent target of genomic instability but not of germ-line mutation; and (c) the polymorphism of codon 389 (AAC to AAT) is frequent, especially in early-onset colorectal cancer patients, in which it is more frequent than in control group.     

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.     

Detection of Frameshift Mutations of the Transforming Growth Factor β Receptor Ⅱ in Gastric Cancers with Microsatellite Instability

OBJECTIVE To study the relationship among microsatellite instability （MSI）, frameshift mutations （FM） of the transforming growth factor β receptor Ⅱ （TGF β R Ⅱ）, methylation state of the hMLH1 promoter and hMLH1 protein expression level in gastric cancers, and to explore their relationship to gastric carcinogenesis. METHODS DNA was isolated from 101 gastric specimens and 5 microsatellite loci were detected. PCR, electrophoresis on denatured polyacrylamide gels and silver staining were performed to detect the MSI. The FMs of TGFβR Ⅱ were also screened with the same method. HMLH1 methylation was analyzed by methylation specific PCR （MSP） and sequencing. HMLH1 protein expression was detected using immunohistochemistry. RESULTS The incidence of MSIs was 53.7% and 0% in the cancers and normal tissues, respectively, with the frequency of MSIs being significantly higher in the gastric cancers compared to the normal gastric tissues （P〈0.05）. The frequency of hMLH1 methylation was 41.5%（17/41） in the gastric cancers and 0%（0/60） in the normal group. Decreased hMLH1 expression was observed in 94.1%（16/17） of cases exhibiting methylation. FMs of TGFβR Ⅱ were identified in 5 （62.5%） of the 8 samples with MSIH. In contrast, FMs were not found in MSI-L or microsatellite stable （MSS） cases. CONCLUSION MSIs and FMs of TGFβR Ⅱ may play an important role in gastric carcinogenesis. HMLH1 methylation is an important modification of the DNA which results in inactivation of hMLH1 and mismatch repair defects which lead to MSls and FMs of TGFβR Ⅱ.     

Mutations of the transforming growth factor β type II receptor gene and microsatellite instability in gastric cancer

Forty-three sporadic gastric cancers were analyzed with regard to whether mutations of simple repeated sequences in the transforming growth factor β type II receptor (TβR-II) gene are associated with microsatellite instability (MSI) and gastric carcinogenesis. In 12 of the 43 cancers (28%), MSI was observed at least at 1 of the 2 microsatellite loci. Frameshift mutations of the TβR-II gene, all of which were 1 base deletion of 10 adenine repeats, were detected in 3 of 6 cancers, with MSI at 2 loci. However, mutations were not detected in 6 cancers, with MSI only at 1 locus and 31 cancers without MSI. Moreover, micro-analysis in these cases revealed that the mutant-type alleles of TβR-II were invariably common in different areas within the tumor, in contrast to the markedly variable alleles of microsatellite loci. Our results suggest that frameshift mutation of the TβR-II gene may be a critical event associated with MSI and may contribute to carcinogenesis of the stomach. One of the possible mechanisms of escape from growth control by TGFβ during gastric carcinogenesis could involve frameshift mutations of the TβR-II gene caused by DNA replication errors. © 1996 Wiley-Liss, Inc.     

Damage to the transforming growth factor TGF-beta type II receptor gene and microsatellite instability in carcinoma cells of the gastrointestinal tract

In order to compare the frequency of damage to the transforming growth factor TGF-beta receptor type II gene (RII gene) and microsatellite instability (MIN) in oncogenesis of sporadic and hereditary cancer of gastrointestinal tract (GIT), 4 groups of carcinomas were analyzed. They included sporadic gastric (GC), family gastric (FGC), sporadic colorectal (CC) and hereditary nonpolyposis colorectal (HNPCC) carcinomas having appropriate clinical and pathological characteristics. Each group consisted of two types of carcinomas, one of them showing MIN. The RII gene damage occurred in 89% of GC (8 cases out of 9), 86% of CC (6 out of 7), 71% of FGC (5 out of 7), 50% of HNPCC (3 out of 6) for carcinomas coupled with MIN, whereas only in 6% (1 out of 18) of GC and 5% (1 out of 22) of CC for carcinomas without MIN. No damage to RII gene was found in the cases of hereditary carcinomas which did not show MIN though the number of cases analyzed was not sufficient for final conclusions (3 cases of FGC and 3 HNPCC). The data revealed a correlation between the MIN phenotype and mutations in RII gene both for sporadic (p < 0.001) and for hereditary (p < 0.02) cases. For all 4 groups the frequency of RII gene damage was found for early and advanced carcinomas. This suggests that the deficiency of TGF-beta receptor complex in both sporadic and hereditary carcinomas of GIT is revealed at early stages of tumor development and consequently may be responsible for tumor progression. The correlation between RII gene damages and MIN in GIT carcinoma cells suggests that genetic change predetermined the neoplasia of colorectal and gastric epithelium and partially overlapped for both sporadic and hereditary cases.     

Loss of HLA class I and mismatch repair protein expression in sporadic endometrioid endometrial carcinomas

Tumor cells can escape from cytotoxic T-cell responses by downregulation of human leukocyte antigen (HLA) class I molecules expressed at the cell surface which has been associated with a deficient mismatch repair (MMR) system in colorectal carcinomas. Our study investigated the association between expression of MMR proteins and HLA class I in sporadic endometrioid endometrial carcinomas (EC). In a consecutively selected cohort of 486 EC patients, MMR proteins (MLH1, MSH2 and MSH6) and HLA class I (HLA-A, -B, -C or β(2) m) were investigated by immunohistochemistry. Expression levels of MMR proteins and HLA class I were compared between low-grade and high-grade ECs. HLA class I expression was compared between tumors with loss (negative immunostaining of ≥1 MMR protein) and expression of MMR proteins. Associations between previously determined numbers of intratumoral CD8(+) T-lymphocytes and expression of MMR proteins and HLA class I and the influence on survival was determined. ECs with loss of MMR protein expression (33.5%) more frequently have loss of HLA-B/C (37.3%), compared to ECs with MMR protein expression (25.5%, p = 0.007). Patients with loss of MMR proteins have a worse disease-specific survival compared to patients with expression (p = 0.039). CD8(+) T-lymphocytes have a positive influence on disease-free and disease-specific survival in the total EC cohort but not in patients with loss of MMR protein expression. In conclusion, our results indicate that loss of MMR protein expression is related to selective downregulation of HLA class I which contributes to immune escape in EC with an abnormal MMR system.     

Clinical and molecular characterisation of hereditary and sporadic metastatic colorectal cancers harbouring microsatellite instability/DNA mismatch repair deficiency

BackgroundPatients treated with chemotherapy for microsatellite unstable (MSI) and/or mismatch repair deficient (dMMR) cancer metastatic colorectal cancer (mCRC) exhibit poor prognosis. We aimed to evaluate the relevance of distinguishing sporadic from Lynch syndrome (LS)-like mCRCs.Patients and methodsMSI/dMMR mCRC patients were retrospectively identified in six French hospitals. Tumour samples were screened for MSI, dMMR, RAS/RAF mutations and MLH1 methylation. Sporadic cases were molecularly defined as those displaying MLH1/PMS2 loss of expression with BRAFV600E and/or MLH1 hypermethylation and no MMR germline mutation.ResultsAmong 129 MSI/dMMR mCRC patients, 81 (63%) were LS-like and 48 (37%) had sporadic tumours; 22% of MLH1/PMS2-negative mCRCs would have been misclassified using an algorithm based on local medical records (age, Amsterdam II criteria, BRAF and MMR statuses when locally tested), compared to a systematical assessment of MMR, BRAF and MLH1 methylation statuses. In univariate analysis, parameters associated with better overall survival were age (P < 0.0001), metastatic resection (P = 0.001) and LS-like mCRC (P = 0.01), but not BRAFV600E. In multivariate analysis, age (hazard ratio (HR) = 3.19, P = 0.01) and metastatic resection (HR = 4.2, P = 0.001) were associated with overall survival, but not LS. LS-like patients were associated with more frequent liver involvement, metastatic resection and better disease-free survival after metastasectomy (HR = 0.28, P = 0.01). Median progression-free survival of first-line chemotherapy was similar between the two groups (4.2 and 4.2 months; P = 0.44).ConclusionsLS-like and sporadic MSI/dMMR mCRCs display distinct natural histories. MMR, BRAF mutation and MLH1 methylation testing should be mandatory to differentiate LS-like and sporadic MSI/dMMR mCRC, to determine in particular whether immune checkpoint inhibitors efficacy differs in these two populations.     

Gene mutation of transforming growth factor beta1 type II receptor in hepatocellular carcinoma.

Alteration of transforming growth factor beta1 (TGF-beta1) type II receptor (RII) appears to cause unresponsiveness to TGF-beta1 in tumorigenic cells. Defect in the mononucleotide repeat sequence, i.e., poly A region of TGF-beta1RII gene has been reported to be related to replication error-positive cancer cells. We examined if there is any TGF-beta1RII mutation in a coding microsatellite in hepatocellular carcinoma (HCC). Genomic DNAs were extracted from formalin-fixed, paraffin-embedded liver tissues obtained at surgery or autopsy in 3 normal individuals and 96 patients with hepatitis C virus-induced chronic liver disease; 3 with chronic hepatitis, 20 with liver cirrhosis and 73 with HCC. The DNA was PCR-amplified at 2 segments of TGF-beta1RII: poly A region which includes the (A)10 microsatellite sequence, and poly GT region. PCR products were directly sequenced. DNA from normal and patients with chronic liver disease contained the 10 wild-type adenines but 3 cases with liver cirrhosis in whom there were only 9 adenines within poly A tract. This microdeletion of one A resulted in a frameshift and truncated a predicted length of amino acids. In HCC lesions, the same deletion was noted in 4 cases (25%) of well-differentiated type, 10 (40%) of moderately differentiated type, 18 (53%) of poorly differentiated type. None of the lesions had mutations within the GT region. Our findings indicate that one adenine deletion of poly A microsatellite tract within TGF-beta1RII is frequently detected in patients with HCC, and the mutation may cause the abrogation of the function of TGF-beta1RII gene.     

Chromosomal abnormalities and microsatellite instability in sporadic endometrial cancer

Defective DNA mismatch repair and nonfunctional mechanisms controlling the proper progression of the cell cycle have been proposed as being responsible for the genomic instability and accumulation of karyotypic alterations in endometrial cancer (EC). To assess whether numerical chromosomal anomalies (aneuploidy) and microsatellite instability (MSI) might be representative of distinctive tumour behaviour, paraffin-embedded tissue samples from 86 patients with sporadic EC were evaluated by both fluorescence in situ hybridisation (FISH) and microsatellite analysis, using free nuclei and genomic DNAs (respectively). Approximately one-third of the tumours analysed (24/74; 32%) exhibited MSI, whereas 38/86 (44%) of the EC samples displayed aneuploidy. The majority of the unstable cases (15/24; 63%) were from advanced-stage patients. Conversely, 23 (61%) out of the 38 tumours with aneuploidy were from early-stage patients. No apparent correlation was found between MSI and aneuploidy, whereas the immunohistochemical (IHC) analysis revealed that inactivation of the MLH1 mismatch repair gene may be involved in the majority of the MSI+ sporadic ECs. No genetic or cytogenetic alteration analysed here seems to add any significant predictive value to the stage of disease.     

Mutation and downregulation of the transforming growth factor beta type II receptor gene in primary squamous cell carcinomas of the head and neck

In the present study, we analyzed 28 squamous cell carcinomas of the head and neck (SCCHN) for mutations in the coding region of TbetaR-II using 'Cold' SSCP and automatic DNA sequencing analyses. Twenty-one percent (6/28) of the SCCHN examined contained TbetaR-II mutations compared with patient-matched normal tissues. These alterations included five missense mutations (A:T-->G:C transitions in codons 250, 401, 448 and 488, and a G:C-->T:A transversion in codon 373), and a 38- bp deletion between nucleotides 1825 to 1862. In addition to these code- altering mutations, one case exhibited a silent mutation (A:T-->G:C transition in codon 451) and three cases contained one of two potential population polymorphisms (codons 354 and 389). In contrast to colon and gastric cancers exhibiting microsatellite instability (MI) or replication errors (RER+), no 'indirect' frameshift mutations were identified within a 10-bp polyadenine repeat present in the TbetaR-II coding sequence. All of the mutations in the present study occurred within the highly conserved serine/threonine kinase domain and represent the first report of such 'direct' TbetaR-II mutations in primary human tumors. In addition, we analyzed a subset of SCCHN and corresponding normal samples for TbetaR-II mRNA expression using semi- quantitative multiplex RT-PCR. Expression of TbetaR-II was decreased by 24% to 74% in 20 of 23 SCCHN (87%) compared with patient-matched normal tissues. Taken together, the results from this study suggest that alterations in the nucleic acid sequence and mRNA expression of TbetaR- II are prevalent events in the development of SCCHN, which may deregulate cell cycle control.      

肺癌微卫星不稳定性与错配修复基因缺陷的相关性研究

目的 通过对肺癌微卫星不稳定性(MSI)的分析与错配修复基因蛋白表达的检测,探讨肺癌发病的分子机制.方法 从50例肺癌患者的正常肺组织、癌组织中提取DNA;SSCP法检测标本中MSI发生情况;免疫组织化学法检测错配修复基因hMLH1及hMSH2在肺癌中的表达情况.结果 50例肺癌中微卫星高度不稳定(MSI-H)14例,低度不稳定(MSI-I)21例,稳定(MSS)15例,正常组织中未出现MSI,两者之间差异有统计学意义(P=0.000);免疫组化结果显示hMLH1在MSI肺癌组织中常为缺失表达,表达率为74%(37/50);hMSH2在MSI肺癌组织中也呈缺失表达,表达率为32%(16/50);而在MSS肺癌组织中均显示hMLH1、hMSH2基因蛋白表达阳性.结论 肺癌的发生可能存在MSI途径,而hMLH1、hMSH2的表达失活则可能导致MSI的发生,因此,MSI可作为肺癌诊断的指标之一.     

肺癌微卫星不稳定性与错配修复基因缺陷的相关性研究

 目的　通过对肺癌微卫星不稳定性（MSI）的分析与错配修复基因蛋白表达的检测,探讨肺癌发病的分子机制。方法　从50例肺癌患者的正常肺组织、癌组织中提取DNA;SSCP法检测标本中MSI发生情况;免疫组织化学法检测错配修复基因hMLH1及hMSH2在肺癌中的表达情况。结果　50例肺癌中微卫星高度不稳定（MSI-H）14例,低度不稳定（MSI-I）21 例,稳定（MSS）15例,正常组织中未出现MSI,两者之间差异有统计学意义（P＝0.000）;免疫组化结果显示hMLH1在MSI肺癌组织中常为缺失表达,表达率为74 %（37／50）;hMSH2在MSI肺癌组织中也呈缺失表达,表达率为32 %（16／50）;而在MSS肺癌组织中均显示hMLH1、 hMSH2基因蛋白表达阳性。结论　肺癌的发生可能存在MSI途径,而hMLH1、hMSH2的表达失活则可能导致MSI的发生,因此,MSI可作为肺癌诊断的指标之一。