中国人遗传性非息肉病性结直肠癌家系的临床表型分析

目的 分析中国人遗传性非息肉病性结直肠癌（HNPCC）家系的临床特征,并评价中国人HNPCC家系标准的临床应用价值。方法 收集符合中国人HNPCC家系标准的家系26个,与509例散发性大肠癌比较,分析其临床特点,26个家系中,8个同时符合Amsterdam标准,分入A组;另18个不符合Amsterdam标准,仅符合中国人HNPCC家系标准,分入B组,分析比较两组间临床特点。结果 26个家系中,大肠癌患者77例,发生同时或异时大肠癌7例（9．1％）,共发生大肠癌癌灶86个,部位明确的71个癌灶中,28个（39．4％）发生在近端结肠,51例（71．8％）患者发病年龄〈50岁,共发生肠外恶性肿瘤24个,其中胃癌9个（37．5％）,是最常见的类型。与散发性大肠癌相比,HNPCC家系具有平均发病年龄轻（P=0．000）、〈50岁者多见（P=0．000）、多原发癌比例高（P=0．015）等特征。与B组相比,A组平均每个家系发生大肠癌的例数明显多于B组（4．5：2．3,P=0．022）;而在平均发病年龄、肿瘤发生部位、多原发大肠癌发生情况、肠外恶性肿瘤谱等方面差异均无统计学意义。结论 （1）中国人HNPCC具有发病年龄轻、多原发大肠癌发生率高及肠外恶性肿瘤以胃癌多见的特点,（2）符合中国人HNPCC家系标准的家系与符合Amsterdam标准的家系具有相似的临床特征,而中国人HNPCC家系标准更适用于小型家系的诊断、同时体现了中国人的肿瘤谱特征。     

Microsatellite marker analysis in screening for hereditary nonpolyposis colorectal cancer (HNPCC)

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant cancer predisposition syndrome caused by germ-line mutations in DNA mismatch repair genes. It is relevant to identify HNPCC patients because colonoscopic screening of individuals with HNPCC mutations reduces cancer morbidity and mortality. Microsatellite instability (MSI) is characteristic of HNPCC tumors. A panel of five markers (BAT25, BAT26, D2S123, D5S346, and D17S250, the so-called Bethesda markers) has been proposed for screening for MSI. To test a hypothesis that the use of BAT26 alone is feasible in screening for MLH1/MSH2 mutation-positive HNPCC patients, we compared the MSI results of 494 colorectal cancer patients obtained using BAT26 with results obtained using the Bethesda markers. BAT26 was able to identify all 27 mutation-positive individuals in this series. The marker failed to identify 2 high MSI tumors and 20 low MSI tumors, all of which expressed MLH1, MSH2, and MSH6 when scrutinized by immunohistochemistry.     

人类错配修复基因在HNPCC家系中的突变研究

目的 了解２９个遗传性非息肉病性结直肠癌（ＨＮＰＣＣ０这 中ｈＭＬＨＩ和ｈＭＳＨ２基因的种系突变状况。方法 ＨＰＣＲ－ＳＳＣＰ和ＤＮＡ测序的方法进行突变筛选。结果 （１）在２９个家系中,ｈＭＬＨ１和ｈＭＳＨ２两个基因的总突变率为３１．０％,与对照组（２％）相比差异有极显著性,其中ＨＭＬＨ１基因是主要的相关基因。（２）１０名患大肠癌的家系成员均含有与先证者相同的突变,反映了突变与在肠癌的主要的相关基     

N-acetyltransferase (NAT) 2 acetylator status and age of onset in patients with hereditary nonpolyposis colorectal cancer (HNPCC)

N-acetyltransferase (NAT) 2 is an essential polymorphic enzyme involved in the metabolism of various xenobiotics, including potential carcinogens. The individual differences in the NAT2 metabolic capacity are caused by allelic variants of the NAT2 gene which are determined by a pattern of single nucleotide polymorphisms (SNPs) resulting in slow (SA), intermediate (IA) or rapid acetylator (RA) phenotypes. Highly penetrant germline mutations in mismatch repair (MMR) genes are the cause of the disease in hereditary nonpolyposis colorectal cancer (HNPCC). There is no strict correlation between the type of germline mutation in MMR genes and the HNPCC phenotype, but age of tumor onset (AO) in HNPCC has been associated at least in part with different variants in apoptosis-related genes. To clarify the potential modifying role of the NAT2 acetylator status in HNPCC, we performed a multicenter study in 226 individuals with colorectal cancer carrying exclusively pathogenic germline mutations in MSH2 or MLH1. We did not observe any significant difference in the NAT2 acetylator status frequency between HNPCC patients and 107 healthy controls (P=0.156), and between MLH1 and MSH2 mutation carriers (P=0.198). Multivariate Cox regression analysis revealed that male patients had a significantly increased risk to develop CRC compared to females during any interval (P=0.043), while the NAT2 acetylator status (P=0.447) and the mutated gene (MLH1 or MSH2) (P=0.236) were not risk factors for AO. The median AO in HNPCC patients was 39 years in patients with RA as well as with SA status (P=0.347). In MLH1 mutation carriers, the median AO was 38 years in RA and 36 years in SA status patients (P=0.901), whereas in MSH2 mutation carriers, the median AO was 39 years in RA and 42 years in SA status patients (P=0.163). Log-rank test revealed a significantly lower age of CRC onset in male compared to female HNPCC patients (P=0.0442). These data do not support the hypothesis that the NAT2 acetylatorship acts as a modifying factor on AO in HNPCC-associated CRC.     

Exclusion of breast cancer as an integral tumor of hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant genetic predisposition syndrome that accounts for 2-7% of all colorectal cancers. Diagnosis of HNPCC is based on family history (defined by Amsterdam or Bethesda Criteria), which often includes a history of multiple synchronous or metachronous cancers. The majority of HNPCC results from germ-line mutations in the DNA mismatch repair (MMR) genes hMSH2 and hMLH1 with rare alterations in hMSH6 and hPMS2 in atypical families. Both HNPCC and sporadic MMR-deficient tumors invariably display high microsatellite instability (MSI-H). Two types of HNPCC families can be distinguished: type I (Lynch I) with tumors exclusively located in the colon; and type II (Lynch II) with tumors found in the endometrium, stomach, ovary, and upper urinary tract in addition to the colon. A proposed association of breast cancer with type II HNPCC is controversial. To address this important clinical question, we examined MSI in a series of 27 female patients who presented with synchronous or metachronous breast plus colorectal cancer. Although MSI-H was found in 5 of 27 (18.5%) of the colon cancers, in all cases the matched breast cancer was microsatellite stable. We also examined the breast tumors from three women who were carriers of MMR gene mutations from HNPCC families. None of these three breast tumors displayed MSI nor was the expression of MMR proteins altered in these tumors. We conclude that breast cancer largely arises sporadically in HNPCC patients and is rarely associated with the HNPCC syndrome.     

遗传性非腺瘤病性结直肠癌的诊治进展

遗传性非腺瘤病性结直肠癌（HNPCC）是一种常染色体显性遗传的综合症,占总的结直肠癌的56%--10%。该病由错配修复基因缺陷造成,肿瘤表现出高度的微卫星不稳。临床上辨别HNPCC患者对诊断和治疗以及监测HNPCC家庭成员发病有指导意义。     

遗传性非息肉病性大肠癌的诊治进展

遗传性非息肉病性结直肠癌(HNPCC)是一种常染色体显性遗传病，错配修复基因的种系突变是发病基础，在散发性大肠癌中遴选HNPCC家族，并对HNPCC患者及其家属进行基因检测可以发现HNPCC相关肿瘤的高危人群，使家族中发病率低的成员免受长期医疗随访之苦，而且对HNPCC相关肿瘤患者进行预防性手术有较大的临床意义。     

Mismatch repair and the hereditary non-polyposis colorectal cancer syndrome (HNPCC)

The hereditary non-polyposis colorectal cancer (HNPCC)-syndrome is the most common form of hereditary colorectal cancers, and accounts for 2-7% of the total colorectal cancer burden. Since there are no single clinical features specific for HNPCC, diagnosis is based on family history (Amsterdam or Bethesda criteria) and is confirmed by the detection of a mutation in one of the responsible mismatch repair (MMR) genes. Two types of HNPCC-families can be distinguished. Type I HNPCC tumors are exclusively located in the colon, whereas in Type II HNPCC patients, extracolonic tumors are present in the stomach, endometrium, ovary, and urinary tract. The identification of the human homologues of yeast mismatch repair genes hMSH2, hMSH3, hMSH6, hMLH1, hMLH3, hPMS1 (scMLH2), and hPMS2 (scPMS1) offered the prospect of genetic screening leading to an extensive search for mutations in HNPCC-families. The majority of the alterations have been found in hMSH2 (40%) and hMLH1 (40%) genes. Mutations in the other MMR genes appear rare, absent, and/or associated with atypical families (1-5%). As a result of the mismatch repair deficiency, replication misincorporation errors accumulate, resulting in a mutator phenotype. Diagnosis of HNPCC-associated replication errors is most easily determined by the examination of a panel of the National Cancer Institute (NCI)-recommended simple repeated sequences (microsatellites), combined with immunohistochemical analysis. Although the exact molecular mechanism of the tumor development in these patients remains poorly understood, the identification of tumors that harbor a microsatellite instability has clinical and prognostic implications.     

The management of families affected by hereditary non-polyposis colorectal cancer (HNPCC)

This study assessed current practice and methods for improvement in the management of families with hereditary non-polyposis colorectal cancer (HNPCC). HNPCC families registered at five London Genetics Centres and a specialised Colorectal family cancer clinic (CFCC) were identified. Ascertainment of management and outcome details were obtained by scrutiny of patient records and by correspondence with General practitioners (GPs). Two hundred and three families with HNPCC were identified. 79.5% (403/507) of at-risk relatives ascertained were contacted by the genetics centres, and 80.2% (65/81) by the CFCC (P = 1.0). 54.8% (211/385) of probands and relatives within genetics centres’ catchment areas were advised to undertake a surveillance programme, compared with 82.1% (64/78) of those cared for by the CFCC (P < 4.2 × 10⁻⁶). Adherence to surveillance guidelines was 76.6% (49/64) in individuals cared for by the only centre that undertook responsibility for surveillance follow-up (CFCC) and 41.7% (88/211) for the genetics centres, which did not assume responsibility (P < 8.9 × 10⁻⁷) (using two sided P-values for P (O ≥ E|O ≤ E)). 15.3% of GPs were unaware their patient had been recommended a surveillance programme, 65% did not know who was responsible for ensuring surveillance follow-up. A questionnaire to fifteen UK genetics centres demonstrated that the majority (86.7%) did not assume responsibility for surveillance follow-up. Since surveillance adherence is clearly better where centres assume responsibility for follow-up, it is recommended that regional or national registers of HNPCC families be developed and maintained to ensure effective management.     

The risk of brain tumours in hereditary non-polyposis colorectal cancer (HNPCC)

Hereditary non-polyposis colorectal cancer (HNPCC) is known to be associated with several extracolonic cancers, e.g., cancers of the endometrium, stomach, urinary tract, small bowel and ovary. An association between HNPCC and brain tumours has also been reported, although previous risk analysis did not reveal an excess of this type of tumour. To determine whether HNPCC predisposes patients to brain tumours, we used risk analysis to compare families with HNPCC to those in the general population. Of the 1,321 subjects from 50 HNPCC families (with 60,237 person-years of follow-up) in the Dutch HNPCC Registry which satisfy the Amsterdam Criteria, 312 had colorectal cancer. The registry revealed 14 brain tumours in the HNPCC-patients and their first-degree relatives: 5 astrocytomas, 3 oligodendrogliomas, 1 ependymoma and 5 tumours for which a pathological report was not available. The relative risk of brain tumour in patients with HNPCC and their first-degree relatives was 6 times greater than in the general population (95% confidence interval, 3.5 to 10.1). After exclusion of the cases based only on family history, the relative risk was 4.3 (95% confidence interval, 2.3 to 8.0). Although the relative risk of brain tumour was increased, the lifetime risk was low (3.35%). Because it is not certain whether an improvement of the overall prognosis can be achieved by early diagnosis and intervention, and in view of the low lifetime risk, we do not recommend screening for brain tumours in HNPCC families. © 1996 Wiley-Liss, Inc.     

Tumor spectrum in cancer family syndrome (hereditary nonpolyposis colorectal cancer)

The distribution of different malignant tumors was studied in 40 cancer family syndrome (CFS) families with 315 affected family members and a total of 472 separate tumors or malignant diseases. Only families with three or more first-degree family members with colorectal carcinoma were included and other CFS characteristics were required in at least two cases. Colorectal (63%), endometrial (8%), gastric (6%), biliopancreatic (4%), and uroepithelial carcinomas (2%) were the most frequent, and represent the tumors typical of CFS. Families with endometrial cancer (23, 57%) and those without endometrial cancer (17, 43%) did not differ in frequencies of other extracolonic carcinomas. Families with endometrial cancer has more affected members and especially more affected female members than those without endometrial cancer (means, 9.7 and 4.9 versus 5.5 and 1.6 per family, respectively). The authors conclude, therefore, that the occurrence of one or more types of extracolonic tumors in members of CFS families does not provide a firm basis for subdividing the CFS (or hereditary nonpolyposis colorectal carcinoma syndrome.     

High proportion of large genomic rearrangements in hMSH2 in hereditary nonpolyposis colorectal cancer (HNPCC) families of the Basque Country

Hereditary nonpolyposis colorectal cancer (HNPCC), which represents the most common form of inherited colorectal cancer, results from germline alterations of the mismatch repair genes MSH2, MLH1 and MSH6. Rearrangements of MSH2 and MLH1 are involved in at least 10% and 4.3%, respectively, of the HNPCC families fulfilling the Amsterdam (AMS) criteria. We applied a recently developed method, multiplex ligation-dependent probe amplification (MLPA), to study MLH1/MSH2 copy number changes in 29 unrelated Basque Country HNPCC families. We detected six different genomic rearrangements in total (6/29=20.69%), four in MSH2 gene (13.79%), and two in MLH1 gene. All of the MSH2 rearrangements were genomic deletions involving several exons. The MLH1 rearrangements were initially detected as one deletion of exon 18 and one deletion of exon 19, but after sequencing analysis, these deletions were not confirmed and corresponded to base pair mutations. We conclude that MLPA is an excellent tool for detecting exon copy number changes in MLH1 and MSH2 in the DNA from HNPCC patients, although all detected rearrangements should be confirmed by an independent molecular methodology. Furthermore, our results in the Basque Country show higher percentages of rearrangements than previously published by other authors.     

Screening for Lynch syndrome (hereditary nonpolyposis colorectal cancer) among endometrial cancer patients

Endometrial cancer is the most common cancer in women with Lynch syndrome. The identification of individuals with Lynch syndrome is desirable because they can benefit from increased cancer surveillance. The purpose of this study was to determine the feasibility and desirability of molecular screening for Lynch syndrome in all endometrial cancer patients. Unselected endometrial cancer patients (N = 543) were studied. All tumors underwent microsatellite instability (MSI) testing. Patients with MSI-positive tumors underwent testing for germ line mutations in MLH1, MSH2, MSH6, and PMS2. Of 543 tumors studied, 118 (21.7%) were MSI positive (98 of 118 MSI high and 20 of 118 MSI low). All 118 patients with MSI-positive tumors had mutation testing, and nine of them had deleterious germ line mutations (one MLH1, three MSH2, and five MSH6). In addition, one case with an MSI-negative tumor had abnormal MSH6 immunohistochemical staining and was subsequently found to have a mutation in MSH6. Immunohistochemical staining was consistent with the mutation result in all seven truncating mutation-positive cases but was not consistent in two of the three missense mutation cases. We conclude that in central Ohio, at least 1.8% (95% confidence interval, 0.9-3.5%) of newly diagnosed endometrial cancer patients had Lynch syndrome. Seven of the 10 Lynch syndrome patients did not meet any published criteria for hereditary nonpolyposis colorectal cancer, and six of them were diagnosed at age >50. Studying all endometrial cancer patients for Lynch syndrome using a combination of MSI and immunohistochemistry for molecular prescreening followed by gene sequencing and deletion analysis is feasible and may be desirable.     

Gene-related cancer spectrum in families with hereditary non-polyposis colorectal cancer (HNPCC)

The family histories of 130 individuals with documented hereditary non-polyposis colorectal cancer (HNPCC) (caused by mutations in mismatch-repair (MMR) genes MSH2 (n = 64), MLH1 (n = 62) or MSH6 (n = 4)) were obtained, and incidence of cancers in those families was compared to that in the general population. There were a total of 982 cancers in 723 individuals. Colorectal cancer (CRC) was the commonest type (64% and 55% in individuals from families with germline MLH1 and MSH2 mutations respectively). Median age at diagnosis of first CRC in MSH6 mutation families was 59 years compared to 45 years in both MLH1 and MSH2 mutation families. The relative risk (RR) of endometrial cancer was 55 in MSH2 mutation families, compared with 27 in MLH1 mutation families, and 37 in MSH6 mutation families; median age at diagnosis 49 years. Even within MSH2 families, endometrial cancer tended to cluster, with 28 of the 58 cases coming from families with three or more cases (P < 0.001). Absolute risk of endometrial cancer in MLH1 families was still greater than any other cancer (other than CRC). 5% of cancers in both MLH1 and MSH2 mutation families were gastric (RR = 12); 53% of these were diagnosed before 50 years. Seven cases of small intestinal cancer occurred in MSH2 and MLH1 mutation families (RR = 26). There were 13 cases of cancer of the ureter; all were in MSH2 families. These cancers tended to cluster within families (P < 0.001); three of seven families with urothelial cancer had such cases in two or more individuals; two others had kidney cancer. Nineteen of 27 ovarian cancers (70%) were in MSH2 mutation families and 70% of these were diagnosed before age 50 years. There were 9 cases of sebaceous skin cancer, 3 in two MLH1 and 6 in four MSH2 mutation families. Of 22 pancreatic cancers, 14 were known to be diagnosed before 60 years. Breast cancer RR was 1.7 overall. The type of mutation (truncating or other type, and site of mutation) showed no obvious correlation with the presence or absence of extra-colonic cancers in families.     

Psychological consequences of predictive genetic testing for hereditary non-polyposis colorectal cancer (HNPCC): a prospective follow-up study

Predictive genetic testing for cancer allows identification of those with the mutation (mutation positive) who should undergo cancer surveillance aiming at early detection of cancer and those without the mutation (mutation negative), whose unnecessary worry can be alleviated and who need not undergo frequent surveillance. However, there is a risk that predictive testing might have a harmful emotional impact on an individual. In the course of a predictive genetic testing protocol, we assessed general anxiety (by the State-Trait Anxiety Inventory [STAI]), fear of cancer and death, satisfaction with life and attitude to the future using a questionnaire survey in 271 individuals tested for hereditary non-polyposis colorectal cancer (HNPCC). Measurements were made before the first counseling (baseline), at the test disclosure session (STAI only) and 1 and 12 months after disclosure. Although at every measurement, the mutation-positive individuals were more afraid of cancer than those who were mutation negative, in both groups fear of cancer decreased significantly from baseline after disclosure. The mutation-positive subjects were more anxious than their counterparts immediately after the test disclosure, but the differences had disappeared at the follow-ups. In other variables, neither differences between the groups defined by mutation status nor changes with time were detected. Our findings suggest that counseling and testing relieve fear of cancer; no harmful emotional impact was detectable at the 1-year follow-up. To confirm these findings, however, the impact of testing should be studied after a longer interval. Furthermore, to evaluate the ultimate interpretation of these results, studies are needed to investigate the impact of fear of cancer on surveillance behavior among the mutation-positive subjects.