Prognostic value of KRAS and BRAF mutations in curatively resected colorectal cancer

AIM: To investigate the prognostic role of KRAS and BRAF mutations after adjustment for microsatellite instability(MSI) status in Japanese colorectal cancer(CRC) population.METHODS: We assessed KRAS and BRAF mutations and MSI status in 813 Japanese patients with curatively resected, stage Ⅰ-Ⅲ CRC and examined associations of these mutations with disease-free survival(DFS) and overall survival(OS) using uni- and multivariate Cox proportional hazards models.RESULTS: KRAS and BRAF mutations were detected in 312(38%) of 812 and 40(5%) of 811 tumors, respectively. KRAS mutations occurred more frequently in females than in males(P = 0.02), while the presence of BRAF mutations was significantly associated with the female gender(P = 0.006), proximal tumor location(P 0.001), mucinous or poorly differentiated histology(P 0.001), and MSI-high tumors(P 0.001). After adjusting for relevant variables, including MSI status, KRAS mutations were associated with poorer DFS(HR = 1.35; 95%CI: 1.03-1.75) and OS(HR = 1.46; 95%CI: 1.09-1.97). BRAF mutations were poor prognostic factors for DFS(HR = 2.20; 95%CI: 1.19-4.06) and OS(HR = 2.30; 95%CI: 1.15-4.71). Neither the BRAF by MSI interaction test nor the KRAS by MSI interaction test yielded statistically significant results for DFS and OS.CONCLUSION: KRAS and BRAF mutations are associated with inferior survival, independent of MSI status, inJapanese patients with curatively resected CRC.     

Involvement of the DNA mismatch repair system in antineoplastic drug resistance

Different types of antineoplastic drugs, such as the alkylating agents busulfan, N-methyl-N′-nitro-N-nitrosoguanidine, N-methyl-N-nitrosourea, procarbazine and temozolomide, the antimetabolites, mercaptopurine and 6-thioguanine, the platinum compounds carboplatin and cisplatin, the anthracycline doxorubicin and the epipodophyllotoxine etoposide act by damaging DNA directly or indirectly. Increasing evidence has shown that tumours could acquire resistance to these drugs by loss of DNA-mismatch repair (MMR) activity. This phenomenon is caused by a decreased MMR-dependent stimulation of signal-transduction pathways causing programmed cell death. Simultaneously, the mutation rate in MMR-deficient tumours is increasing, which could lead to additional secondary drug/resistance phenotypes to other antineoplastic agents. In addition to this, an enhanced mutation rate may contribute to increased phenotypic variation and therefore the clinical aggressiveness of primary tumours and their metastases. Received: 11 November 1998 / Accepted: 2 January 1999     

Microsatellite instability and novel mismatch repair gene mutations in northern Chinese population with Hereditary non‐polyposis colorectal cancer

OBJECTIVE: Hereditary non‐polyposis colorectal cancer (HNPCC) syndrome is the most common cause of hereditary colorectal cancer with an early age of onset. Microsatellite instability (MSI) and germline mutation in one of the DNA mismatch repair (MMR) genes are found in the majority of HNPCC families and provide an opportunity for genetic diagnosis and prophylactic screening. The MMR gene mutation spectrum may vary across different populations and be influenced by founder mutations that prevail in specific ethnic groups. China is a big and ancient nation with enormous genetic diversity, which is especially notable between the northern and southern Chinese populations. A MMR gene mutation database for the southern Chinese population based in Hong Kong has been previously established. This study compares the MMR gene mutation spectrum and the MSI of HNPCC between the northern and southern Chinese populations. METHODS: Twenty‐five HNPCC families from northern China were systematically analyzed. The MSI analysis was performed using five loci in the USA National Cancer Institute (NCI) panel (D2S123, D5S346, BAT‐25, BAT‐26 and BAT‐40) by PCR from the tumor and normal tissue. MSH2, MSH6 and MLH1 were performed using immunohistochemical staining. Two founder mutations of MSH2 and MLH1 were examined by PCR base analyses using primers flanking the two deletion sites (c.1452_1455delAATG in MSH2 and 1.8 kb deletion involving exon 11 of MLH1) . RESULTS: Of the 25 families collected, 19 met Bethesda guideline (BG) 1 and six met BG3. Twenty‐two (15.7%) were extra‐colonic cancers with gastric cancer (in seven patients) being the most common cancer type. Of the 25 tumors analyzed, 21 (84%) were high level microsatellite instability (MSI‐H) and four (16%) were microsatellite stable (MSS). Eighteen (86%) of the 21 MSI‐H tumors showed loss of either the MLH1 or the MSH2 protein. Three MSI‐H tumors and all four MSS tumors showed no loss of expression of the three MMR proteins. Out of the 21 patients with MSI‐H tumors, 12 (57%) showed pathogenic germline mutations in either MLH1 (n = 8) or MSH2 (n = 4). Overall, three novel mutations (in patients H22, H17 and H29) have been identified. One of them, c.503_4insA, caused a frameshift mutation in the MLH1 gene. The other two were found in the MSH2 gene, including a frameshift (c.899_890insAT) and a splice junction (IVS7‐1G→A, SA of Exon 8) mutation. CONCLUSIONS: The results suggest a distinctly different mutation spectrum of MMR genes between northern and southern Chinese populations and call for a systematic, nationwide study to facilitate the design of a MMR gene mutation detection strategy tailored for individual populations in China.     

Risk of colorectal polyps and of malignancies in asymptomatic carriers of mutations in the main DNA mismatch repair genes

Objective: Mutation carriers (Mut+) in DNA mismatch repair genes are predisposed to cancer of various organs and to adenomatous polyps; however, they may remain asymptomatic and cancer or polyp-free for several years. We purposed to analyse the clinical follow-up of individuals carrying constitutional mutations in the MLH1, MSH2 or MSH6 genes who were unaffected by benign polyps or malignant tumours at diagnosis.

Material and Methods: Mut?+?subjects (n.81) were members of Lynch syndromes in whom mutations were detected between 1993 and 2015; all were asymptomatic at diagnosis. They were informed of the cancer risk and surveillance was suggested. As controls, 113 nongene carriers (Mut?) in the same Lynch families were identified.

Results: About one-fourth of the mutation carriers developed polyps, mostly adenomas; polyps were less (12%, p?MLH1 vs. MSH2 mutation carriers. In Mut+, 21 malignant tumours developed in 14 carriers vs. 4 tumours in 3 patients among Mut? (p?Conclusions: Cancer developed more often in Mut+, with no consistent difference between MLH1 and MSH2 carriers. More polyps (mostly adenomas) were detected in MLH1 carriers. The majority (13 of 21) of malignant tumours occurred in organs for which there is no recommended surveillance, and were lethal in three patients.     

Dynamic control of strand excision during human DNA mismatch repair

Mismatch repair (MMR) is activated by evolutionarily conserved MutS homologs (MSH) and MutL homologs (MLH/PMS). MSH recognizes mismatched nucleotides and form extremely stable sliding clamps that may be bound by MLH/PMS to ultimately authorize strand-specific excision starting at a distant 3′- or 5′-DNA scission. The mechanical processes associated with a complete MMR reaction remain enigmatic. The purified human (Homo sapien or Hs) 5′-MMR excision reaction requires the HsMSH2–HsMSH6 heterodimer, the 5′ → 3′ exonuclease HsEXOI, and the single-stranded binding heterotrimer HsRPA. The HsMLH1–HsPMS2 heterodimer substantially influences 5′-MMR excision in cell extracts but is not required in the purified system. Using real-time single-molecule imaging, we show that HsRPA or Escherichia coli EcSSB restricts HsEXOI excision activity on nicked or gapped DNA. HsMSH2–HsMSH6 activates HsEXOI by overcoming HsRPA/EcSSB inhibition and exploits multiple dynamic sliding clamps to increase tract length. Conversely, HsMLH1–HsPMS2 regulates tract length by controlling the number of excision complexes, providing a link to 5′ MMR.Mismatch repair (MMR) is a highly conserved strand-specific excision-resynthesis process that corrects nucleotide misincorporation errors during replication and nucleotide mismatches arising from recombination between heteroallelic parents or physical damage to the DNA (for review see ref. 1). Mutation of core MMR components results in elevated mutation rates and susceptibility to a variety of cancers (2).MMR has been reconstituted with purified Escherichia coli, Saccharomyces cerevisae, and human proteins (3–6). The core MutS homologs (MSH) and MutL homologs (MLH/PMS) components direct a strand-specific excision reaction, whereas resynthesis appears to be uniquely performed by the replicative polymerase complex (1). In all organisms the excision process is initiated at a single-strand DNA scission (ssDNA/S) that may be located either 3′ or 5′ and hundreds to thousands of base pairs distant from the mismatch (4, 7). An ssDNA/S positioned on the newly replicated strand ensures accurate correction of replication misincorporation errors (1).Excision directionality in γ-proteobacteria (E. coli) is linked to the choice of 3′ or 5′ exonucleases that specifically degrade ssDNA generated by the EcUvrD helicase in concert with EcMutS and EcMutL (1). The lack of a helicase distinguishes yeast and human MMR from γ-proteobacteria. Moreover, the eukaryotic 3′- and 5′-excision reactions require different core MMR components and likely occur by different mechanisms (1). For example, the 3′-MMR excision requires the replicative processivity factor PCNA to activate a cryptic MLH/PMS endonuclease activity (8), whereas 5′ MMR uses the only known MMR exonuclease EXOI (3, 5, 6). Unlike the E. coli ssDNA exonucleases, EXOI will initiate 5′ excision from a ssDNA/S in the absence of a helicase (9). Whereas the purified 5′-MMR reaction does not require MLH/PMS or PCNA, complementation studies with cellular extracts displayed a substantial requirement for MLH/PMS (10, 11).A number of models have been proposed to account for the transmission of mismatch recognition to the ssDNA/S (12) as well as the roles of MMR components in the ensuing excision process (1, 13). However, the ensemble functions of the MMR components during excision in all organisms remain largely unknown. We have applied several single-molecule imaging techniques to visualize the complete human 5′ MMR strand excision process in real time. Our results suggest that dynamic and stochastic processes ultimately control 5′ excision, which may at least partially explain the different factor requirements in crude and purified reactions.     

Four novel germline mutations in the MLH1 and PMS2 mismatch repair genes in patients with hereditary nonpolyposis colorectal cancer

Background  Hereditary nonpolyposis colorectal cancer (HNPCC) is the most common cause of early onset hereditary colorectal cancer. In the majority of HNPCC families, microsatellite instability (MSI) and germline mutation in one of the DNA mismatch repair (MMR) genes are found. Materials and methods  The entire coding sequence of MMR genes (MLH1, MLH2, MLH6, and PMS2) was analyzed using direct sequencing. Also, tumor tests were done as MSI and immunohistochemistry testing. Results  We were able to find three novel MLH1 and one novel PMS2 germline mutations in three Iranian HNPCC patients. The first was a transversion mutation c.346A>C (T116P) and happened in the highly conserved HATPase-c region of MLH1 protein. The second was a transversion mutation c.736A>T (I246L), which caused an amino acid change of isoleucine to leucine. The third mutation (c.2145,6 delTG) was frameshift and resulted in an immature stop codon in five codons downstream. All of these three mutations were detected in the MLH1 gene. The other mutation was a transition mutation, c.676G>A (G207E), which has been found in exon six of the PMS2 gene and caused an amino acid change of glycine to glutamic acid. MSI assay revealed high instability in microsatellite for two patients and microsatellite stable for one patient. Conclusion  In all patients, an abnormal expression of the MMR proteins in HNPCC was related to the above novel mutations.     

Helicobacter pylori infection and expression of DNA mismatch repair proteins

AIM： TO determine the expression of DNA （MMR） proteins, including hMLH1 and hMSH2, in gastric epithelial cells in the patients with or without Helicobacter pylori （H pylori）-infected gastritis. METHODS： Fifty Hpylori-positive patients and 50 H pylori-negative patients were enrolled in the study. During endoscopy of patients with non-ulcer dyspepsia, two antral and two corpus biopsies were taken for histological examination （Giemsa stain） and for immunohistochemical staining of hMLH1 and hMSH2. RESULTS： The percentage of epithelial cell nuclei that demonstrated positivity for hMLH1 staining was 84.14 ± 7.32% in Hpylori-negative patients, while it was 73.34 ±10.10% in Hpylori-positive patients （P 〈 0.0001）. No significant difference was seen between the two groups regarding the percentage of epithelial cell nuclei that demonstrated positivity for hMSH2 staining （81.16±8.32% in H pylori-negative versus 78.24 ± 8.71% in Hpylori-positive patients; P = 0.09）. CONCLUSION： This study indicates that Hpylori might promote development of gastric carcinoma at least in part through its ability to affect the DNA MMR system     

错配修复基因突变检测对遗传性非息肉病性结直肠癌患病风险的预测

目的 探讨错配修复(MMR)基因种系突变检测在遗传性非息肉病性结直肠癌(HNPCC)家系成员患癌风险预测中的作用.方法 对43个携带致病性突变的HNPCC家系的316名家庭成员的发病情况进行详细调查,并对结果进行统计学分析.结果 ①突变状态明确的HNPCC家系年龄大于20岁的成员共263例,其中突变携带者144例,非携带者119例;HNPCC相关恶性肿瘤的发生率分别为59.03%(85/144)和2.52%(3/119),二者差异有统计学意义(X2=93.44,P＜0.01).②在144例年龄大于20岁的突变携带者中,男、女HNPCC相关恶性肿瘤发生率分别为72.00%(54/75)和44.93%(31/69),二者差异有统计学意义(χ~2=10.89,P＜0.01).③随着年龄的增加,突变携带者发生HNPCC相关肿瘤的累计风险度逐渐增加.结论 在HNPCC家系中,MMR基因种系突变携带者为发生HNPCC相关肿瘤的高危人群,MMR基因种系突变的检测能很好地预测HNPCC相关肿瘤的发生危险.     

Clinical significance of K-ras and BRAF mutations in Chinese colorectal cancer patients

AIM:To identify and assess mutations in the K-ras and BRAF genes in a cohort of Chinese patients with colorectal cancer (CRC) for their association with various clinicopathological parameters and prognosis.METHODS:Genomic DNA was isolated from frozen tissues.Pyrosequencing analysis was conducted to detect mutations in the K-ras (codons 12,13,and 61) and BRAF genes (codon 600).Statistical analysis was carried out using SPSS-15.0 software.RESULTS:Among the 118 colorectal cancer patients,we detected 41 (34.7%)...     

Importance of MutL homologue MLH1 and MutS homologue MSH2 expression in Turkish patients with sporadic colorectal cancer

AIM: To assess the incidence of MLH1 (the human MutL homologue) and MSH2 (the human MutS homologue) protein expression in Turkish patients with sporadic colorectal cancers and to compare their survival and clinicopathological features. METHODS: We validated the tissue microarray technology in 77 colorectal carcinomas by analyzing the immunohistochemical expression of proteins involved in two main pathways of colorectal carcinogenesis: p53 protein for loss of heterozygosity tumors; MLH1 and MSH2 proteins for microsatellite instability (MSI). RESULTS: Our analysis showed that 29 (39.2%) had loss of MLH1 expression, 5 (6.8%) had loss of MSH2 expression and 2 cases had loss of expression of both proteins. We found that 60% of MSH2-negative tumors were located in the right side of the colon; all MSH2-negative cases were women. In addition, the loss of MSH2 expression was correlated with low p53 expression. Neither MLH1 nor MSH2 expressions were associated with prognosis, although there seemed a tendency of longer survival (71.7 ± 8.65 mo vs 47.08 ± 5.26 mo) for the patients with MLH1-negative versus MLH1-positive carcinomas. There were not significant differences in overall and recurrence-free survival among MLH1/MSH2-positive and -negative cases.CONCLUSION: Our data supports that Turkish patients with MLH1- and MSH2-defective tumors have some distinct features from each other. Although prognostic importance remains controversial, immunohistochemical analysis of mismatch repair genes may be used as a routine histopathological examination of sporadic colorectal carcinomas.     

Deficient DNA mismatch repair is associated with favorable prognosis in Thai patients with sporadic colorectal cancer

AIM:To determine the prognostic significance of deficient mismatch repair(d MMR) and BRAF V600 E in Thai sporadic colorectal cancer(CRC) patients.METHODS:We studied a total of 211 out of 405 specimens obtained from newly diagnosed CRC patients between October 1,2006 and December 31,2007 at Siriraj Hospital,Mahidol University.Formalinfixed paraffin-embedded blocks of CRC tissue samples w e re a n a l y ze d fo r d M M R b y d e t e c t i o n o f M M R protein expression loss by immunohistochemistry or microsatellite instability using polymerase chain reaction(PCR)-DHPLC.BRAF V600 E mutational analysis was performed in DNA extracted from the same archival tissues by two-round allele-specific PCR and analyzed by high sensitivity DHPLC.Associations between patient characteristics,MMR and BRAF status with diseasefree survival(DFS) and overall survival(OS) were determined by Kaplan-Meier survival plots and log-rank test together with Cox’s proportional hazard regression.RESULTS:d MMR and BRAF V600 E mutations were identified in 31 of 208(14.9%) and 23 of 211(10.9%) tumors,respectively.d MMR was more commonly found in patients with primary colon tumors rather than rectal cancer(20.4% vs 7.6%,P =0.01),but there was no difference in MMR status between the right-sided and left-sided colon tumors(20.8% vs 34.6%,P = 0.24).d MMR was associated with early-stage rather than metastatic disease(17.3% vs 0%,P = 0.015).No clinicopathological features such primary site or tumor differentiation were associated with the BRAF mutation.Six of 31(19.3%) samples with d MMR carried the BRAFmutation,while 17 of 177(9.6%) with proficient MMR(p MMR) harbored the mutation(P = 0.11).Notably,patients with d MMR tumors had significantly superior DFS(HR = 0.30,95%CI:0.15-0.77; P = 0.01) and OS(HR = 0.29,95%CI:0.10-0.84; P = 0.02) compared with patients with p MMR tumors.By contrast,the BRAF V600 E mutation had no prognostic impact on DFS and OS.CONCLUSION:The prevalence of d MMR and BRAF V600 E in Thai sporadic CRC patients was 15% and 11%,respectively.The d MMR phenotype was associated with a favorable outcome.     

Somatic molecular changes and histo-pathological features of colorectal cancer in Tunisia

AIM:To determine correlations between family history,clinical features and mutational status of genes involved in the progression of colorectal cancer(CRC).METHODS:Histo-pathological features and molecular changes[KRAS,BRAF and CTNNB1 genes mutations,microsatellite instability(MSI)phenotype,expression of mismatch repair(MMR)and mucin(MUC)5AC proteins,mutation and expression analysis of TP53,MLH1promoter hypermethylation analysis]were examined in a series of 51 unselected Tunisian CRC patients,10 of them had a proven or probable hereditary disease,on the track of new tumoral markers for CRC susceptibility in Tunisian patients.RESULTS:As expected,MSI and MMR expression loss were associated to the presence of familial CRC(75%vs 9%,P<0.001).However,no significant associations have been detected between personal or familial cancer history and KRAS(codons 12 and 13)or TP53(exons 4-9)alterations.A significant inverse relationship has been observed between the presence of MSI and TP53 accumulation(10.0%vs 48.8%,P=0.0335)in CRC tumors,suggesting different molecular pathways to CRC that in turn may reflect different environmental exposures.Interestingly,MUC5AC expression was significantly associated to the presence of MSI(46.7%vs 8.3%,P=0.0039),MMR expression loss(46.7%vs8.3%,P=0.0039)and the presence of familial CRC(63%vs 23%,P=0.039).CONCLUSION:These findings suggest that MUC5AC expression analysis may be useful in the screening of Tunisian patients with high risk of CRC.     

KRAS mutation testing in metastatic colorectal cancer

The KRAS oncogene is mutated in approximately 35%-45% of colorectal cancers, and KRAS mutational status testing has been highlighted in recent years. The most frequent mutations in this gene, point substitutions in codons 12 and 13, were validated as negative predictors of response to anti-epidermal growth factor receptor antibodies. Therefore, determining the KRAS mutational status of tumor samples has become an essential tool for managing patients with colorectal cancers. Currently, a variety of detection methods have been established to analyze the mutation status in the key regions of the KRAS gene; however, several challenges remain related to standardized and uniform testing, including the selection of tumor samples, tumor sample processing and optimal testing methods. Moreover, new testing strategies, in combination with the mutation analysis of BRAF, PIK3CA and loss of PTEN proposed by many researchers and pathologists, should be promoted. In addition, we recommend that microsatellite instability, a prognostic factor, be added to the abovementioned concomitant analysis. This review provides an overview of KRAS biology and the recent advances in KRAS mutation testing. This review also addresses other aspects of status testing for determining the appropriate treatment and offers insight into the potential drawbacks of mutational testing.     

错配修复基因和骨保护素在胃癌中的表达及意义

目的 研究胃癌组织中错配修复基因MSH2和骨保护素(OPG)的表达、两者间的相关性及与胃癌生物学行为的关系.方法 制备组织芯片,应用原位杂交和免疫组化技术检测220例胃癌组织中MSH2和OPG的表达情况.结果 MSH2 mRNA、OPG mRNA、MSH2蛋白和OPG蛋白在胃癌组织中的阳性表达率分别为57.3%、56.4%、59.6%和55.9%.MSH2和OPG表达均与胃痛的TNM分期、浸润深度、脉管侵犯、淋巴结转移和远处转移呈正相关,与分化程度呈负相关.胃癌中MSH2和OPG的表达呈正相关.MSH2和OPG阳性表达病例的平均生存时间和5年生存率明显低于阴性者.结论 胃癌中MSH2和OPG的表达上凋,且两者呈正相关.MSH2和OPG的表达与胃癌的临床病理特征相关,两者的联合测定有利于胃癌诊断和判断预后.     

26 280例结直肠癌患者MLH1和PMS2基因表达情况及临床病理特征的多中心回顾性研究

目的研究MLH1和PMS2蛋白表达情况与临床病理特征。 方法本研究纳入2010年1月至2018年12月包括中国医学科学院肿瘤医院在内7家医院的结直肠癌数据平台的患者205 071人次,其中26 280例免疫组化信息和病例信息满足研究标准。分析MLH1和PMS2基因蛋白表达情况与患者发病年龄、性别、肿瘤大小、病理分期等因素的关系。 结果MLH1缺失率4%,PMS2缺失率3.25%。两种蛋白表达缺失的患者男女比例差异存在统计学意义（均P<0.05）,其发病年龄均小于正常表达组患者（均P<0.0001）。其第二原发癌的发病率也高于正常表达组（均P<0.0001）。MLH1和PMS2蛋白表达缺失的患者肿瘤最大径大于正常表达组（均P<0.0001）,清扫淋巴结总数目也高于正常表达组（均P<0.0001）。此外,与正常组相比,MLH1表达缺失组呈现明显家族聚集倾向（P=0.001）。而在部位上,肿瘤部位发生在右半结肠的患者数据显示,MLH1和PMS2蛋白缺失的发生率高于蛋白表达正常组。肿瘤分期方面,MLH1和PMS2蛋白的T分期在表达缺失组与正常组差异具有统计学意义（均P<0.0001）,M分期中,PMS2蛋白缺失患者的远处转移率低于正常组患者（P=0.0008）。 结论MLH1与PMS2表达缺失的患者发病年龄更早,肿瘤体积大,右半结肠比例相对较高,第二原发癌的发生率更高,伴有更高的淋巴结清扫数目,且与病理分期存在密切关联。     

Correlation between polymorphisms in DNA mismatch repair genes and the risk of primary hepatocellular carcinoma for the Han population in northern China

Abstract

Purpose: This study investigated correlations between polymorphisms in DNA mismatch repair (MMR) genes and the risk of primary hepatocellular carcinoma (PHC). Methods. Single nucleotide polymorphisms (SNPs) in the DNA MMR genes MLH3 (rs175080), PMS1 (rs5742933), PMS2 (rs1059060), MSH3 (rs26279), MSH5 (rs1150793, rs2075789) and MSH6 (rs1042821) were detected using the SNaPshot method in 250 PHC cases and in 308 patients without PHC in the Han population in northern China. Results. The AA genotype in MLH3 (rs175080) increased the risk of PHC (odds ratio [OR] = 3.424; 95% confidence interval [CI]: 1.097–10.689). The AG and GG genotypes in MSH3 (rs26279) increased the risk of PHC (OR: 1.644 and 3.300; 95% CI: 1.112–2.428 and 1.765–6.168, respectively). The AA genotype in MSH5 (rs2075789) increased the risk of PHC (OR: 9.229; 95% CI: 1.174–72.535). The CT genotype in MSH6 (rs1042821) reduced the risk of PHC (OR: 0.629; 95% CI: 0.428–0.924). Conclusions. Our study suggests that polymorphisms in MLH3 (rs175080), MSH3 (rs26279), MSH5 (rs2075789) and MSH6 (rs1042821) may be independent risk factors for PHC.     

Mutational analysis of the DNA mismatch repair gene hMLH1 in myeloid leukaemias

Mutations of the DNA mismatch repair (MMR) gene hMLH1 have recently been linked to the development of some hereditary and sporadic cancers which frequently display widespread microsatellite instability (MSI). Conflicting results regarding the extent of MSI in myeloid leukaemias prompted us to perform mutational analysis of all 19 exons of the hMLH1 gene by polymerase chain reaction-single-stranded conformation polymorphism (PCR-SSCP) and sequence analysis in a total of 133 patients with acute and chronic myeloid leukaemia. Apart from one exonic and one intronic polymorphism, no mutations were detected in any of the samples indicating that the major MMR gene hMLH1 is not involved in the pathogenesis or progression of myeloid malignancies.     

MicroRNA-31 expression in colorectal serrated pathway progression

MicroRNAs have been increasingly recognized as useful biomarkers for colorectal cancers (CRC). We have recently observed that microRNA-31 (miR-31) expression is associated with BRAF mutation and prognosis in CRC. Moreover, high miR-31 expression is frequently detected in sessile serrated adenomas compared with hyperplastic polyps (HPs). These results suggest that miR-31 may contribute to the progression of serrated lesions. At a follow-up colonoscopy, we observed the case of a 75-year-old man with a 7-mm flat-elevated lesion in the cecum and diagnosed the lesion as an early invasive carcinoma with serrated features. Tissue specimens were obtained from the representative areas to compare the molecular alterations in the carcinoma component with those in the HP component. Higher miR-31 expression was observed in the carcinoma component (57-fold increase) and the HP component (8-fold increase) compared with the paired normal mucosa, suggesting that miR-31 may be one of the key molecules in serrated pathway progression.     

北方人群HNPCC微卫星不稳定性和错配修复基因突变规律研究

目的探讨中国北方人群遗传性非息肉病性结直肠癌（HNPCC）微卫星不稳定性（MSI）和错配修复（MMR）基因突变的特征。方法通过MSI检测和MMR基因种系突变检测对30个中国北方人HNPCC家系进行系统分析。结果①25个家系表现为高度微卫星不稳定（MSI-H）,1个家系为低度微卫星不稳定（MSI-L）,4个家系表现为微卫星稳定（MSS）;②在25个MSI-H家系的先证者中,检测到14种致病性种系突变（hMLH1基因突变9种,hMSH2基因突变5种）,突变类型包括框移突变、无义突变、剪接区突变、错义突变,并发现3种新突变位点。结论中国北方人群HNPCC的错配修复基因突变谱广泛而多样,应开展系统研究,以建立北方人群的HNPCC错配修复基因突变库并制定相应的突变检测策略。