Somatic mutations of APC gene in carcinomas from hereditary non-polyposis colorectal cancer patients

AIM:To investigate the mutational features of adenomatouspolyposis coli (APC) gene and its possible arising mechanismin hereditary non-polyposis colorectal cancers (HNPCC).METHODS:PCR-based In Vitro Synthesized Protein Test(IVSP) assay and sequencing analysis were used to confirmsomatic mutations of whole APC gene in 19 HNPCC cases.RESULTS:Eleven cases with 13 mutations were determinedto harbor APC mutations.The prevalence of APC mutationwas 58%(11/19).The mutations consisted of 9 frameshiftand 4 nonsense ones,indicating that there were moreframeshift mutations (69%).The frameshift mutations allexhibited deletion or insertion of 1-2 bp and most of them(7/9) happened at simple nucleotide repeat sequences,particularly within (A)n tracts (5/9).All point mutationspresented C-to-T transitions at CpG sites.CONCLUSION:Mutations of APC gene were detected inmore than half of HNPCC,indicating that its mutation was acommon molecular event and might play an important rolein the tumorigenesis of HNPCC.Locations of frameshiftmutations at simple nucleotide repeat sequences and pointmutations at CpG sites suggested that many mutationsprobably derived from endogenous processes includingmismatch repair (MMR) deficiency.Defective MMR mightaffect the nature of APC mutations in HNPCC and likely occurearlier than APC mutational inactivation in some patients.     

Is colonoscopy sufficient for colorectal cancer surveillance in all HNPCC patients？

A 34-year-old male with hereditary non-polyposis colon cancer with a mutation in hMSH2 line is reported. Despite regular colonoscopic follow-up, he developed cecal cancer involving the extraluminal area. Due to sub-occlusive symptoms, the patient was submitted to further colonoscopy, however with no clear evidence of neoplasia. Thin slice multiplanar reconstruction computed tomography CT scan performed thereafter revealed a transmural mass 2.5 cm in size localized near the cecal valve. Discussion is made on the reliability of colonoscopic examinations as well as the need for further investigations in the follow-up of patients at very high risk of right-sided colon cancer, such as male hMSH2 carrier affected by hereditary non-polyposis colon cancer.     

Risk of colorectal neoplasm in patients with acromegaly： A meta-analysis

AIM： To examine the risk of colorectal neoplasm in acromegalic patients by meta-analyzing all relevant controlled studies.
METHODS： Extensive English language medical literature searches for human studies, up to December 2007, were performed using suitable keywords. Pooled estimates [odds ratio （OR） with 95% confidence intervals （CI）] were obtained using either the fixed or random-effects model as appropriate. Heterogeneity between studies was evaluated with the Cochran Q test whereas the likelihood of publication bias was assessed by constructing funnel plots. Their symmetry was estimated by the adjusted rank correlation test.
RESULTS： For hyperplastic polyps the pooled ORs with 95% CI were 3.557 （2.587-4.891） by fixed effects model and 3.703 （2.565-5.347） by random effects model. The Z test values for overall effect were 7.81 and 6.984, respectively （P 〈 0.0001）. For colon adenomas the pooled ORs with 95% CI were 2.486 （1.908-3.238） （fixed effects model） and 2.537 （1.914-3.364） （random effects model）. The Z test values were 6.747 and 6.472, respectively （P 〈 0.0001）. For colon cancer the pooled OR with 95% CI was identical for both fixed and random effects model （OR, 4.351; 95% CI, 1.533-12.354; Z = 2.762, P = 0.006]. There was no significant heterogeneity and no publication bias in all the above meta-analyses.
CONCLUSION： Acromegaly is associated with an increased risk of colorectal neoplasm.     

The genetics of nicotine dependence： Relationship to pancreatic cancer

INTRODUCTION The use of tobacco products constitutes the most preventable cause of premature death worldwide. It is estimated that half of all Americans who continue to smoke will die of smoking-related diseases'11, including cancer, emphysema and heart d…     

Germline MLH1 and MSH2 mutational spectrum including frequent large genomic aberrations in Hungarian hereditary non-polyposis colorectal cancer families： Implications for genetic testing

AIM: To analyze the prevalence of germline MLH1 and MSH2 gene mutations and evaluate the clinical characteristics of Hungarian hereditary non-polyposis colorectal cancer (HNPCC) families. METHODS: Thirty-six kindreds were tested for mutations using conformation sensitive gel electrophoreses, direct sequencing and also screening for genomic rearrangements applying multiplex ligation-dependent probe amplifi cation (MLPA). RESULTS: Eighteen germline mutations (50%) were identifi ed, 9 in MLH1 and 9 in MSH2. Sixteen of these sequence alterations were considered pathogenic, the remaining two were non-conservative missense alterations occurring at highly conserved functional motifs. The majority of the defi nite pathogenic mutations (81%, 13/16) were found in families fulfilling the stringent Amsterdam Ⅰ/Ⅱ criteria, including three rearrangements revealed by MLPA (two in MSH2 and one in MLH1). However, in three out of sixteen HNPCC-suspected families (19%), a disease-causing alteration could be revealed. Furthermore, nine mutations described here are novel, and none of the sequence changes were found in more than one family.CONCLUSION: Our study describes for the f irst time the prevalence and spectrum of germline mismatch repair gene mutations in Hungarian HNPCC and suspected-HNPCC families. The results presented here suggest that clinical selection criteria should be relaxed and detection of genomic rearrangements should be included in genetic screening in this population.     

Azoxymethane-induced rat aberrant crypt foci： Relevance in studying chemoprevention of colon cancer

The pathogenesis of colon cancer involves sequential and multistep progression of epithelial cells initiated to a cancerous state with defined precancerous intermediaries. Aberrant crypt foci （ACF） represent the earliest identifiable intermediate precancerous lesions during colon carcinogenesis in both laboratory animals and humans. ACF are easily induced by colon-specific carcinogens in rodents and can be used to learn more about the process of colon carcinogenesis. For over two decades, since its first discovery, azoxymethane （AOM）-induced rodent ACF have served as surrogate biomarkers in the screening of various anticarcinogens and carcinogens. Several dietary constituents and phytochemicals have been tested for their colon cancer chemopreventive efficacy using the ACF system. There has been substantial effort in defining and refining ACF in terms of understanding their molecular make-up, and extensive research in this field is currently in progress. In chemoprevention studies, AOM-induced rat ACF have been very successful as biomarkers, and have provided several standardized analyses of data. There have been several studies that have reported that ACF data do not correlate to actual colon tumor outcome, however, and hence there has been an ambiguity about their role as biomarkers. The scope of this mini-review is to provide valuable insights and limitations of AOM-induced rat ACF as biomarkers in colon cancer chemoprevention studies. The role of the dynamics and biological heterogeneity of ACF is critical in understanding them as biomarkers in chemoprevention studies.     

Clinical predictors of colorectal polyps and carcinoma in a low prevalence region： Results of a colonoscopy based study

AIM： To estimate the prevalence of colorectal cancer （CRC） in patients with long lasting colonic symptoms undergoing total colonoscopy; and to establish clinical features predicting its occurrence. METHODS： This prospective study was carried out in Imam Hospital, Tabriz University of medical sciences, Iran. Continuous patients with long lasting lower gastrointestinal tract symptoms who had the criteria of a colonoscopy were included. The endoscopist visualized the caecum documented by a photo and/or a specimen from terminal ileum. RESULTS： Four hundred and eighty consecutive symptomatic patients [mean age （SD）： 42.73 （16.21）] were included. The prevalence of colorectal neoplasia was 15.3% （34 subjects） and 37.7% （181 subjects） had a completely normal colon. Adenomatous polyps were detected in 56 （11.7%） patients, in 12.3% of men and 10.9% of women. The mean age of the patients with a polyp was significantly higher than the others （49.53 ± 14.16 vs 41.85 ± 16.26, P = 0.001）. Most of the adenomatous polyps were left sided and tubular; only 22.5% of polyps were more than 10 mm. Cancer was detected in 16 （3.6%） of our study population, which was mostly right sided （57.2%）. The mean age of patients with cancer was significantly higher than the others （60.25 ± 8.26 vs 42.13 ± 16.08, P 〈 0.005） and higher than patients with polyps [60.25 （8.26） vs 49.53 （1.91） （P 〈 0.0005）]. None of the symptoms （diarrhea, abdominal pain, rectal bleeding, constipation, altering diarrhea and constipation, history of cancer, known irritable bowel disease, history of polyp and fissure or family history of cancer） were predictors for cancer or polyps, but the age of the patient and unexplainedanemia independently predicted cancer. CONCLUSION： Less advanced patterns and smaller sizes of adenomas in Iran is compatible with other data from Asia and the Middle East, but in contrast to western countries. Prevalence of colonic neoplasia in our community seems to be lower th     

Left paraduodenal hernia in an adult complicated by ascending colon cancer： A case report

Paraduodenal hernia is the most common internal hernia. The clinical symptoms of paraduodenal hernia may be intermittent and nonspecific. Therefore, it is difficult to diagnose preoperatively. Abdominal computed tomography (CT) scan currently plays an important role in the evaluation and management of paraduodenal hernia before surgical operation. We report one unique case of preoperatively diagnosed left paraduodenal hernia complicated by advanced ascending colon cancer and reviews of Japanese literature.     

Effect of mucin production on survival in colorectal cancer： A case-control study

AIM： TO investigate the impact of mucin production on prognosis in colorectal cancer, in terms of overall survival （OS） and time to disease progression （TTP） in patients with mucinous compared to those with nonmucinous colorectal cancer （NMCRC）, matched for age, gender, and tumor stage. METHODS： Thirty five patients with mucinous colorectal cancer （MCRC） were matched for age, gender, and tumor stage with 35 controls having NMCRC. OS and TTP were compared among 4 groups divided according to mucin content： group A （50%-75% mucin）, group B （75%-100% mucin）, group C or controls （〈 50% mucin）. Group D consisted of all patients with tumors having 〈 75% mucin （controls and groups A together）. RESULTS： Median survival in MCRC and NMCRC groups was 46.2 and 112.9 mo, respectively （P = 0.26）. OS in groups A and B was 70.1 and 32.8 mo （P = 0.46）, and in groups B and D was 32.8 and 70.1 mo, respectively （P = 0.143）. TTP in MCRC and NMCRC was 50.17 and 44.77 too, respectively （P = 0.795）. TTP in groups A, B, and D was 70.1, 24.8, and 65.5 too, respectively. Twenty-eight percent of patients with MCRC had poorly differentiated adenocarcinoma versus 8.6% in NMCRC patients （P = 0.028）. CONCLUSION： MCRC is associated with a non-significant decrease in median survival and TTP, particularly when mucin content is 〉 75% of tumor volume. However, it tends to be more poorly differentiated. A larger study matching for stage and grade is needed.     

Clinical and molecular analysis of hereditary non-polyposis colorectal cancer in Chinese colorectal cancer patients

AIM:To analyze the frequency of hereditary non-polyposis colorectal cancer(HNPCC)in Chinese colorectal cancer(CRC)patients,and to discuss the value of microsatellite instability(MSI)and/or immunohistochemistry(IHC)for MSH2/MLH1 protein analysis as pre-screening tests in China.METHODS:The Amsterdam criteriaⅠandⅡ(clinical diagnosis)and/or germline hMLH1/hMSH2 mutations(genetic diagnosis)were used to classify HNPCC families.Genetic tests,including microsatellite instability,immunohistochemistry for MSH2/MLH1 proteins and hMSH2/hMLH1 genes,were performed in each proband.RESULTS:From July 2000 to June 2004,1988 patients with colorectal cancer were analysed and 114 CRC patients(5.7%)from 48 families were categorized as having HNPCC,including 76 from 26 families diagnosed clinically and 38 from the other 22 families diagnosed genetically.The sensitivity and specificity of high MSI and IHC for predicting mutations were 100% and 54%,and 79% and 77%,respectively.CONCLUSION:The frequency of HNPCC is approximately 10% among all Chinese CRC cases.The MSI and IHC detections for hMSH2/hMLH1 proteins are reliable pre-screening tests for hMLH1/hMSH2 germline mutations in families suspected of having HNPCC.     

Molecular signaling mechanisms of apoptosis in hereditary non-polyposis colorectal cancer

Colorectal cancer is the second most leading cause of cancer related deaths in the western countries. One of the forms of colorectal cancer is hereditary non-polyposis colorectal cancer (HNPCC), also known as "Lynch syndrome". It is the most common hereditary form of cancer accounting for 5%-10% of all colon cancers. HNPCC is a dominant autosomal genetic disorder caused by germ line mutations in mismatch repair genes. Human mismatch repair genes play a crucial role in genetic stability of DNA, the inactivation of which results in an increased rate of mutation and often a loss of mismatch repair function. Recent studies have shown that certain mismatch repair genes are involved in the regulation of key cellular processes including apoptosis. Thus, differential expression of mismatch repair genes particularly the contributions of MLH1 and MSH2 play important roles in therapeutic resistance to certain cytotoxic drugs such as cisplatin that is used normally as chemoprevention. An understanding of the role of mismatch repair genes in molecular signaling mechanism of apoptosis and its involvement in HNPCC needs attention for further work into this important area of cancer research, and this review article is intended to accomplish that goal of linkage of apoptosis with HNPCC. The current review was not intended to provide a comprehensive enumeration of the entire body of literature in the area of HNPCC or mismatch repair system or apoptosis; it is rather intended to focus primarily on the current state of knowledge of the role of mismatch repair proteins in molecular signaling mechanism of apoptosis as it relates to understanding of HNPCC.     

遗传性非息肉病性大肠癌的研究进展

遗传性非息肉病性大肠癌(HNPCC)是一种由错配修复基因(MMR)突变造成的常染色体显性遗传病,又称Lynch综合征,是遗传性大肠癌的代表.HNPCC约占全部大肠癌的5%-15%.错配修复基因(MMR)的种系突变和微卫星不稳定(MSI)是其分子遗传学基础.HNPCC的临床病理特点突出,具有右半结肠多见、发病早、病理分化差、多原发癌多见的特点.目前其治疗方法以手术为主,COX-2阻滞剂可能成为HNPCC治疗的一个新的途径.近年来分子生物学的进展也为人们对HNPCC生物学行为和治疗的认识提供了有益的参考.     

Three novel missense germline mutations in different exons of MSH6 gene in Chinese hereditary non-polyposis colorectal cancer families

AIM To investigate the germline mutations of MSH6 gene in probands of Chinese hereditary non-polyposis colorectal cancer (HNPCC) families fulfilling different clinical criteria.METHODS Germline mutations of MSH6 gene were detected by PCR-based DNA sequencing in 39 unrelated HNPCC probands fulfilling different clinical criteria in which MSH2 and MLH1 mutations were excluded. To further investigate the pathological effects of detected missense mutations, we analyzed the above related MSH6 exons using PCR-based sequencing in 137 healthy persons with no family history. The clinicopathological features were collected from the Archive Library of Cancer Hospital, Fudan University and analyzed.RESULTS Four germline missense mutations distributed in the 4th, 6th and 9th exons were observed. Of them,three were not found in international HNPCC databases and did not occur in 137 healthy controls, indicating that they were novel missense mutations. The remaining mutation which is consistent with the case H14 at c.3488A＞T of exon 6 of MSH6 gene was also found in the controls, the rate was approximately 3.65%(5/137) and the type of mutation was not found in the international HNPCC mutational and SNP databases,suggesting that this missense mutation was a new SNP unreported up to date.CONCLUSION Three novel missense mutations and a new SNP observed in the probands of Chinese HNPCC families, may play an important role in the development of HNPCC.     

MS-HRM在遗传性非息肉性大肠癌筛查中的应用

目的探讨甲基化敏感性高分辨率熔解曲线分析(MS-HRM)在遗传性非息肉性大肠癌(HNPCC)筛查中的应用价值。方法采用实时荧光定量PCR技术检测miR-195在41例散发性大肠癌(SCRC)和9例HNPCC患者癌组织及对应癌旁正常组织(距离癌组织5 cm)中的表达水平,随后使用MS-HRM检测miR-195启动子区域CpG岛甲基化情况。结果 miR-195在HNPCC癌组织中的表达量为1.20±1.48,甲基化比例为55.56%(5/9);miR-195在SCRC组织中的表达量为0.76±1.06,甲基化比例为58.54%(24/41),差异无统计学意义(P0.05);miR-195在肠癌组织及癌旁正常组织中的平均表达水平分别为0.837±1.145和2.236±2.468,差异具有统计学意义(P0.05)。结论 miR-195在SCRC和HNPCC癌组织中的表达有无差异尚待进一步研究。miR-195可能有助于抑制肠癌发展,并且因其甲基化而参于大肠癌的发病机制。     

Colonic epithelial cell proliferation in hereditary non-polyposis colorectal cancer

Background—Despite the recentdiscovery of four genes responsible for up to 90% of all cases ofhereditary non-polyposis colorectal cancer (HNPCC), there will still befamilies in whom predictive testing is not possible. A phenotypicbiomarker would therefore be useful. An upwards shift of theproliferative compartment in colonic crypts is reported to be one ofthe earliest changes in premalignant mucosa.
Aims—To assess the role of cryptcell proliferation as a phenotypic biomarker in HNPCC.
Patients—Thirty five patients at50% risk of carrying the HNPCC gene (21 of whom subsequently underwentpredictive testing and hence gene carrier status was known) and 18controls.
Methods—Crypt cell proliferationwas measured at five sites in the colon using two different techniques.Labelling index was determined using the monoclonal antibody MIB1 andwhole crypt mitotic index was measured using the microdissection andcrypt squash technique. The distribution of proliferating cells within the crypts was also assessed.
Results—There were no significantdifferences in the total labelling index or mean number of mitoses percrypt, nor in the distribution of proliferating cells within the crypt,between the study and control groups at any site. When the 21 patients in whom gene carrier status was known were analysed separately therewere no significant differences in the measured indices ofproliferation between the HNPCC gene carriers and non-gene carriers.
Conclusion—Crypt cell proliferationis not a discriminative marker of gene carriage in HNPCC.

Keywords:cell proliferation; hereditary non-polyposiscolorectal cancer

     

Endoscopic surveillance for hereditary non-polyposis colorectal cancer (HNPCC) family members in a Southern Italian region

Background

Surveillance in hereditary non-polyposis colorectal cancer (HNPCC) family members recommends baseline colonoscopy starting at age 20 and then surveillance colonoscopy every 1–2 years.

Aims

To verify adherence to the guidelines for HNPCC family members enrolled in endoscopic surveillance.

Methods

Data regarding 11 HNPCC families was retrieved from our database. Excluding 11 probands, 106 family members were evaluated and 40 underwent surveillance.

Results

At baseline colonoscopy, 7 colorectal cancers (CRC), 14 polyps (PO) [1 inflammatory, 2 hyperplastic, 10 adenomas with low grade dysplasia (LGD-AD) and 1 adenoma with high-grade dysplasia (HGD-AD)] were diagnosed in sixteen individuals. Twenty-eight HNPCC family members underwent endoscopic surveillance, with a total of 94 surveillance colonoscopies. Of these, 45 were positive (4 CRC, 3 inflammatory PO, 34 hyperplastic PO, 21 LGD-AD and 5 HGD-AD).Mean time between two consecutive surveillance colonoscopies was 24.6 months (range 4–168). Median time to first positive surveillance colonoscopy was 84 months for HNPCC family members with negative baseline colonoscopy, and 60 months for those with positive baseline colonoscopy (p = 0.21).

Conclusions

Our data suggests that surveillance colonoscopy every 2 years is adequate to diagnose advanced lesions in HNPCC family members, and improves their compliance with surveillance.     

Genetic diagnosis strategy of hereditary non-polyposis colorectal cancer

AIM： To study the characteristics of mismatch repair gene mutation of Chinese hereditary non-polyposis colorectal cancer （HNPCC） and hMLH1 gene promoter methylation, and to improve the screening strategy and explore the pertinent test methods. METHODS： A systematic analysis of 30 probands from HNPCC families in the north of China was performed by immunohistochemistry, microsatellite instability （MSI）, gene mutation and methylation detection. RESULTS： High frequency microsatellite instability occurred in 25 probands （83.3%） of HNPCC family. Loss of hMLH1 and hMSH2 protein expression accounted for 88% of all microsatellite instability. Pathogenic mutation occurred in 14 samples and 3 novel mutational sites were discovered. Deletion of exons 1-6, 1-7 and 8 of hMSH2 was detected in 3 samples and no large fragment deletion was found in hMLH1. Of the 30 probands, hMLH1 gene promoter methylation occurred in 3 probands. The rate of gene micromutation detection combined with large fragment deletion detection was 46.7%-56.7%. The rate of the two methods in combination with methylation detection was 63.3%. CONCLUSION： Scientific and rational detection strategy can improve the detection rate of HNPCC. Based on traditional molecular genetics and combined with epigenetics, multiple detection methods can accurately diagnose HNPCC.     

Lynch syndrome and Lynch syndrome mimics: The growing complex landscape of hereditary colon cancer

Hereditary non-polyposis colorectal cancer (HNPCC) was previously synonymous with Lynch syndrome; however, identification of the role of germline mutations in the DNA mismatch repair (MMR) genes has made it possible to differentiate Lynch syndrome from other conditions associated with familial colorectal cancer (CRC). Broadly, HNPCC may be dichotomized into conditions that demonstrate defective DNA MMR and microsatellite instability (MSI) vs those conditions that demonstrate intact DNA MMR. Conditions characterized by MMR deficient CRCs include Lynch syndrome (germline MMR mutation), Lynch-like syndrome (biallelic somatic MMR mutations), constitutional MMR deficiency syndrome (biallelic germline MMR mutations), and sporadic MSI CRC (somatic biallelic methylation of MLH1). HNPCC conditions with intact DNA MMR associated with familial CRC include polymerase proofreading associated polyposis and familial colorectal cancer type X. Although next generation sequencing technologies have elucidated the genetic cause for some HNPCC conditions, others remain genetically undefined. Differentiating between Lynch syndrome and the other HNPCC disorders has profound implications for cancer risk assessment and surveillance of affected patients and their at-risk relatives. Clinical suspicion coupled with molecular tumor analysis and testing for germline mutations can help differentiate the clinical mimicry within HNPCC and facilitate diagnosis and management.