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.     

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.     

Lynch syndrome in Tunisia: first description of clinical features and germline mutations

Purpose

High rates of early colorectal cancers (CRC) are observed in Tunisia suggesting genetic susceptibility. Nevertheless, up to now, no molecular study has been performed in the Tunisian population. In our research, we evaluated the clinical characteristics of Tunisian families suspected of Lynch syndrome and the contribution of DNA mismatch repair (MMR) genes.

Methods

Thirty-one unrelated families suspected of Lynch syndrome were studied. Probands were tested for the presence of germline mutations in the MMR genes MLH1, MSH2, MSH6 and in MUTYH. Available tumours were analysed for microsatellite instability and expression of MMR proteins. Detailed family and medical histories were collected.

Results

A total of 134 cancers were noted in the 31 families, the most frequent type of cancer corresponding to CRC (69%), followed by uterine cancer (7.5%). Germline mutations were identified in 11 (35.5%) families (six MSH2, five MLH1, including seven novel mutations), seven of which fulfilled the Amsterdam criteria (sensitivity, 63.6%; positive predictive value, 58.3%). Noteworthy, germline mutations were detected in 52.6% of male patients tested, but in only 8.3% of females (p?=?0.02). Moreover, CRC were essentially left sided in families without detected mutation (p?=?0.017). Ages of onset of cancers and tumour spectrum were very similar in families with or without MMR germline mutation, contrasting with previous studies performed in other populations.

Conclusions

MMR genes contribute significantly to CRC susceptibility in the Tunisian population. However, the cause of early CRC susceptibility remains unknown in most cases, especially in women and in patients with early left colon or rectal cancer.     

Functional analysis of human mismatch repair gene mutations identifies weak alleles and polymorphisms capable of polygenic interactions

Many of the mutations reported as potentially causing Lynch syndrome are missense mutations in human mismatch repair (MMR) genes. Here, we used a Saccharomyces cerevisiae-based system to study polymorphisms and suspected missense mutations in human MMR genes by modeling them at the appropriate S. cerevisiae chromosomal locus and determining their effect on mutation rates. We identified a number of weak alleles of MMR genes and MMR gene polymorphisms that are capable of interacting with other weak alleles of MMR genes to produce strong polygenic MMR defects. We also identified a number of alleles of MSH2 that act as if they inactivate the Msh2-Msh3 mispair recognition complex thus causing weak MMR defects that interact with an msh6Δ mutation to result in complete MMR defects. These results indicate that weak MMR gene alleles capable of polygenic interactions with other MMR gene alleles may be relatively common.     

Extended microsatellite analysis in microsatellite stable, MSH2 and MLH1 mutation-negative HNPCC patients: genetic reclassification and correlation with clinical features

BACKGROUND: Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disorder predisposing to predominantly colorectal cancer (CRC) and endometrial cancer frequently due to germline mutations in DNA mismatch repair (MMR) genes, mainly MLH1, MSH2 and also MSH6 in families seen to demonstrate an excess of endometrial cancer. As a consequence, tumors in HNPCC reveal alterations in the length of simple repetitive genomic sequences like poly-A, poly-T, CA or GT repeats (microsatellites) in at least 90% of the cases. AIM OF THE STUDY: The study cohort consisted of 25 HNPCC index patients (19 Amsterdam positive, 6 Bethesda positive) who revealed a microsatellite stable (MSS)--or low instable (MSI-L)--tumor phenotype with negative mutation analysis for the MMR genes MLH1 and MSH2. An extended marker panel (BAT40, D10S197, D13S153, D18S58, MYCL1) was analyzed for the tumors of these patients with regard to three aspects. First, to reconfirm the MSI-L phenotype found by the standard panel; second, to find minor MSIs which might point towards an MSH6 mutation, and third, to reconfirm the MSS status of hereditary tumors. The reconfirmation of the MSS status of tumors not caused by mutations in the MMR genes should allow one to define another entity of hereditary CRC. Their clinical features were compared with those of 150 patients with sporadic CRCs. RESULTS: In this way, 17 MSS and 8 MSI-L tumors were reclassified as 5 MSS, 18 MSI-L and even 2 MSI-H (high instability) tumors, the last being seen to demonstrate at least 4 instable markers out of 10. Among all family members, 87 malignancies were documented. The mean age of onset for CRCs was the lowest in the MSI-H-phenotyped patients with 40.5 +/- 4.9 years (vs. 47.0 +/- 14.6 and 49.8 +/- 11.9 years in MSI-L- and MSS-phenotyped patients, respectively). The percentage of CRC was the highest in families with MSS-phenotyped tumors (88%), followed by MSI-L-phenotyped (78%) and then by MSI-H-phenotyped (67%) tumors. MSS tumors were preferentially localized in the distal colon supposing a similar biologic behavior like sporadic CRC. MSH6 mutation analysis for the MSI-L and MSI-H patients revealed one truncating mutation for a patient initially with an MSS tumor, which was reclassified as MSI-L by analyzing the extended marker panel. CONCLUSION: Extended microsatellite analysis serves to evaluate the sensitivity of the reference panel for HNPCC detection and permits phenotype confirmation or upgrading. Additionally, it confirms the MSS status of hereditary CRCs not caused by the common mutations in the MMR genes and provides hints to another entity of hereditary CRC.     

KRAS and BRAF gene mutations and DNA mismatch repair status in Chinese colorectal carcinoma patients

AIM:To investigate gene mutations and DNA mismatch repair(MMR) protein abnormality in Chinese colorectalcarcinoma(CRC) patients and their correlations with clinicopathologic features.METHODS:Clinical and pathological information for 535 patients including 538 tumors was reviewed and recorded.Mutation analyses for exon 2 of KRAS gene and exon 15 of BRAF gene were performed by Sanger sequencing except that in 9 tumors amplification refractory mutation system PCR was used.Expression of MMR proteins including MHL1,MSH2,MSH6 and PMS2 was evaluated by immunohistochemistry.Correlations of KRAS and BRAF mutation status and the expression status of MMR proteins with age,gender,cancer stage,location,and histology were analyzed.Correlations between KRAS or BRAF mutations and MMR protein expression were also explored.RESULTS:The overall frequencies of KRAS and BRAF mutations were 37.9% and 4.4%,respectively.KRAS mutations were more common in patients ≥ 50 years old(39.8% vs 22% in patients 50 years old,P 0.05).The frequencies of BRAF mutants were higher in tumors from females(6.6% vs males 2.8%,P 0.05),located in the right colon(9.6% vs 2.1% in the left colon,1.8% in the rectum,P 0.01),with mucinous differentiation(9.8% vs 2.8% without mucinous differentiation,P 0.01),or being poorly differentiated(9.5% vs 3.4% well/moderately differentiated,P 0.05).MMR deficiency was strongly associated with proximal location(20.5% in the right colon vs 9.2% in the left colon and 5.1% in the rectum,P 0.001),early cancer stage(15.0% in stages Ⅰ-Ⅱ vs 7.7% in stages Ⅲ-Ⅳ,P 0.05),and mucinous differentiation(20.2% vs 9.2% without mucin,P 0.01).A higher frequency of MLH1/PMS2 loss was found in females(9.2% vs 4.4% in males,P 0.05),and MSH2/MSH6 loss tended to be seen in younger(50 years old) patients(12.0% vs 4.0% ≥ 50 years old,P 0.05).MMR deficient tumors were less likely to have KRAS mutations(18.8% vs 41.7% in MMR proficient tumors,P 0.05) and tumorswith abnormal MLH1/PMS2 tended to harbor BRAF mutations(15.4% vs 4.2% in MMR proficient tumors,P 0.05).CONCLUSION:The frequency of sporadic CRCs having BRAF mutation,MLH1 deficiency and MSI in Chinese population may be lower than that in the Western population.     

Lynch综合征相关结直肠癌的遗传基因及分子病理筛查策略

Lynch综合征（Lynch syndrom）是结直肠癌中最常见的遗传性肿瘤综合征,约占全部大肠癌的2~3%。该病患者同时增加了罹患肠外及第二肿瘤的风险。现已证明,Lynch综合征是由于编码错配修复基因（mismatch repair,MMR）——MLH1,MSH2,MSH6和PMS2的种系突变、失活导致的一类显性遗传性疾病,近年发现EPCAM的突变与MSH2表达缺失相关。尽管有Amsterdan及Bethesda等临床诊断标准,利用分子遗传学检测在MMR基因中发现致病性胚系突变仍为目前诊断Lynch综合征的金标准。对于发病年龄小于70岁的结直肠癌患者,均应进行Lynch综合征的筛查。首先需进行微卫星不稳定性（microsatellites instability,MSI）检测,检测手段包括PCR扩增微卫星位点及免疫组化（IHC）检测,而后对相应的MMR基因进行胚系突变的检测以明确是否为Lynch综合征以及相应的致病位点。对于MLH1表达缺失患者需进行BRAF基因突变检测和（或）MLH1启动子区域甲基化检测以除外散发性结直肠癌。对于确诊的患者建议进行家系筛查并进行规律的监测和随访。     

Annexin A10 expression in colorectal cancers with emphasis on the serrated neoplasia pathway

AIM: To validate the utility of Annexin A10 as a surrogate marker of the serrated neoplasia pathway in invasive colorectal cancers(CRCs).METHODS: A total of 1133 primary CRC patients who underwent surgical resection at Seoul National University Hospital between January 2004 and December 2007 were enrolled.Expression of Annexin A10 was evaluated by immunohistochemistry using tissue microarray and paired to our findings on clinicopathologic and molecular characteristics of each individual.Cp G island methylator phenotype was determined by Methy Light assay and microsatellite instability was determined by high performance liquid chromatography.KRAS and BRAF mutation status was evaluated by direct sequencing and allele-specific PCR.Univariate and stage-specific survival analyses were performed to reveal the prognostic value of Annexin A10 expression.RESULTS: Annexin A10 expression was observed in 66(5.8%) of the 1133 patients.Annexin A10 expression was more commonly found in females and was associated with proximal location,ulcerative gross type,advanced T category,N category and TNM stage.CRCs with Annexin A10 expression showed an absence of luminal necrosis,luminal serration and mucin production.CRCs with Annexin A10 expression were associated with Cp G island methylator phenotype,microsatellite instability and BRAF mutation.In survival analysis,Annexin A10 expression was associated with poor overall survival and progression-free survival,especially in stage Ⅳ CRCs.CONCLUSION: Annexin A10 expression is associated with poor clinical behavior and can be used a supportive surrogate marker of the serrated neoplasia pathway in invasive CRCs.     

Epithelial-mesenchymal transition in colorectal cancer tissue of patients with Lynch syndrome

AIM:To explore the epithelial-mesenchymal transition(EMT)in tissue from patients with Lynch syndrome,and to interpret biological behaviour of Lynch syndrome.METHODS:Sixty-eight formalin-fixed and paraffin embedded tissue blocks were analyzed in this study,including tissues from Lynch syndrome(n=30),sporadic colorectal carcinoma(CRC)(n=30),and tumoradjacent tissues(n=8).Tissue sections were stained for human mutS homolog 2(hMSH2),human mutL homolog 1(hMLH1),transforming growth factor-βtypeⅡreceptor(TGFβRⅡ),E-cadherin,β-catenin,matrix metalloproteinase-7(MMP-7)and tissue inhibitor of metalloproteinase-2(TIMP-2)by immunohistochemical staining.Furthermore,clinical data such as age,gender and tumor-node-metastasis stage were also collected retrospectively.RESULTS:The positive expression rates of hMSH2,hMLH1,TGFβRⅡ,E-cadherin,β-catenin,MMP-7 and TIMP-2 were significantly related to the depth of invasion and lymph node metastasis,but not to sex or tumour size or location.The differences in the positive expression rates of hMSH2,hMLH1,TGFβRⅡ,E-cadherin,cytomembraneβ-catenin,cytoplasmicβ-catenin,MMP-7 and TIMP-2 were significant between sporadic CRC and Lynch syndrome.The expression of hMSH2 had a positive correlation with that of hMLH1 in Lynch syndrome and sporadic CRC.The expression of TGFβRⅡhad a positive correlation with that of hMSH2,hMLH1 and MMP-7,and a negative correlation with that of TIMP-2.The expression of MMP-7 had a negative correlation with that of TIMP-2 in Lynch syndrome and sporadic CRC.The expression of E-cadherin was positively correlated with that of cytomembraneβ-catenin.However,the expression of cytomembraneβ-catenin was negatively correlated with that of cytoplasmicβ-catenin,and the expression of cytoplasmicβ-catenin was positively correlated with that of MMP-7.CONCLUSION:EMT may play an important role in the development and progression of Lynch syndrome.Lynch syndrome was caused by the mutations of mismatch repair genes,mainly hMSH2 and hMLH1,which also beget the mutational inactivation of TGFβRⅡ.Therefore,the colorectal cancer of Lynch syndrome can escape the inhibitory effect of TGFβ1.However,TGFβ1 can up-regulate the expression of MMP-7 and down-regulate the expression of TIMP-2 in tumors by disassembling the E-cadherin/β-catenin complex in the cytomembrane.     

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.     

Amplifications of NCOA3 gene in colorectal cancers in a Chinese population

AIM: To investigate the copy number variation of NACO3 gene in colorectal cancer (CRC) and its correlation with tumor progression. METHODS: A total of 142 samples of case-matched CRC tissues and adjacent normal tissues were obtained from patients undergoing bowel resection. Quantitative real-time polymerase chain reaction method was used to investigate the copy number variations of NCOA3 as well as gene expression in the collected tissues. RESULTS: Copy number gains of NCOA3 were detected in 39 CRC samples (27.5%) and were correlatedwith tumor progression (χ2 = 6.42, P = 0.0112). Moreover, there was a positive correlation between copy number gain and mRNA over-expression of NCOA3 in CRCs (P = 0.0023). Expression level of NCOA3 mRNA was also enhanced in the CRC samples with unaltered copy numbers (3.85 ± 1.23 vs 2.71 ± 0.64, P 0.01). CONCLUSION: Sporadic colorectal cancers exhibit different mechanisms of NCOA3 regulation.     

Clinical meaning of BRAF mutation in Korean patients with advanced colorectal cancer

AIM:To evaluate the clinicopathological features ofcolorectal cancer(CRC)with a v-Raf murine sarcomaviral oncogene homolog B1(BRAF)mutation and itsmolecular interaction with microsatellite instability(MSI)and v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog(KRAS)in patients with advanced CRCs.METHODS:From October 2009 to December 2011,141 patients with stageⅢ(n=51)orⅣ(n=90)CRCs who were tested for the BRAF mutation at Severance Hospital were included.Among 141 patients,fivewere excluded due to follow-up loss.Therefore,136patients were included in the study.The clinicopathological data,MSI status,and KRAS/BRAF mutation status were reviewed retrospectively.In addition,to evaluating the value of BRAF mutation status,progressionfree survival and overall survival in all patients werecollected and compared between the BRAF wild-typegroup and BRAF mutation group.RESULTS:Of 136 patients,80(58.8%)were male and the mean age was 59 years.BRAF and KRAS mutations were detected in 9.6%and 35.3%of patients,respectively.Only 4.3%of patients had MSIhigh tumors and there were no MSI-high in tumors with a BRAF mutation.BRAF mutations tended to be more frequent in stageⅣthan in stageⅢ(11.76%vs 5.88%,P=0.370).Patients with a BRAF mutation had a lower incidence of KRAS mutation than those without(7.69%vs 38.21%,P=0.033).Overall survival was significantly shorter in the BRAF mutation group than in the BRAF wild-type group both by univariate analysis(P=0.041)and multivariate analysis(HR=2.195;95%CI:1.039-4.640;P=0.039),while progression-free survival was not different according to BRAF mutation status.CONCLUSION:CRCs with a BRAF mutation have distinct molecular features and resulted in a poor prognosis in Korean patients with advanced CRC.     

Consequences of testing for mismatch repair deficiency of colorectal cancer in clinical practice

Introduction: Mismatch repair deficiency (dMMR) can be found in Lynch syndrome (LS)-associated colorectal carcinoma and in 15% of sporadic colorectal cancer (CRC). Outcome of MMR-deficiency testing is important for surgical decisions as extended colectomy is recommended in young LS-patients with CRC. Moreover, the finding of a dMMR tumour has consequences for the choices of adjuvant chemotherapy as MMR-deficient CRC is resistant to 5-fluorouracil (5-FU) monotherapy. Aims of our study are to evaluate whether MMR-deficiency testing leads to (1) identification of LS, (2) change in surgical treatment and (3) adjustment of systemic therapy in patients with dMMR CRC.

Methods: We performed a multicentre, retrospective study, in a community hospital and a University Medical Centre. We included all CRC-patients between 2012 and 2016 who were tested for microsatellite instability. We collected clinical data such as gender, age, referral to clinical geneticist, surgical procedure and choice of chemotherapy.

Results: We analysed 225 CRCs. Twenty-four (10.7%) of 225 CRC were MMR-deficient. Of the 24 patients with dMMR CRC, 18 (75%) were referred to the clinical geneticist and in nine (37%) patients a MMR mutation was identified. In one (4%) of the 24 patients, a subtotal colectomy was performed. In seven (35%) out of 20 MMR deficient patients, the chemotherapy regimen was adjusted.

Conclusions: The finding of a dMMR CRC had consequences for decisions on chemotherapy in a relative high proportion of patients. We recommend testing in all patients with CRC independent of age at diagnosis, as proper treatment decisions and genetic counselling are very important.     

Familial Colon Cancer Syndromes: an Update of a Rapidly Evolving Field

Colorectal cancer (CRC) is a major cause of morbidity and mortality in the world. Up to 30?% of CRCs have evidence of a familial component, and about 5?% are thought to be due to well-characterized inherited mutations. This review will focus on recent developments in the understanding of the individual hereditary CRC syndromes, including Lynch syndrome, familial CRC type X, familial adenomatous polyposis, MutYH-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, PTEN hamartomatous syndrome, and serrated polyposis syndrome. Advances within the area of hereditary colon cancer syndromes paint a picture of a rapidly moving, rapidly maturing, and increasingly collaborative field with many opportunities for ongoing research and development.     

Immunohistochemical analysis reveals high frequency of PMS2 defects in colorectal cancer

BACKGROUND & AIMS: Germline mutations in the DNA mismatch repair (MMR) genes MSH2, MSH6, or MLH1 predispose to colorectal cancer (CRC) with an autosomal dominant inheritance pattern. The protein encoded by PMS2 is also essential for MMR; however, alterations in this gene have been documented only in extremely rare cases. We addressed this unexpected finding by analyzing a large series of CRCs. METHODS: Expression of MSH2, MSH6, MLH1, and PMS2 was studied by immunohistochemistry in 1048 unselected, consecutive CRCs. Where absence of MMR proteins was detected, microsatellite instability and cytosine methylation of the respective gene promoter were analyzed. The DNA of patients presenting with PMS2-deficient cancers was examined for germline and somatic alterations in the PMS2 gene. RESULTS: An aberrant pattern of MMR protein expression was detected in 13.2% of CRCs. Loss of expression of MSH2, MSH6, or MLH1 was found in 1.4%, 0.5%, and 9.8%, respectively. PMS2 deficiency accompanied by microsatellite instability was found in 16 cases (1.5%) with a weak family history of cancer. The PMS2 promoter was not hypermethylated in these cases. Despite interference of the PMS2 pseudogenes, we identified several heterozygous germline mutations in the PMS2 gene. CONCLUSIONS: PMS2 defects account for a small but significant proportion of CRCs and for a substantial fraction of tumors with microsatellite instability. However, the penetrance of heterozygous germline mutations in PMS2 is considerably lower than that of mutations in other MMR genes. The possible underlying causes of this unorthodox inheritance pattern are discussed.     

Clinicopathological and molecular genetic analysis of HNPCC in China

AIM: To explore the clinicopathological and molecular genetic features of hereditary nonpolyposis colorectal cancer (HNPCC) in Chinese population. METHODS: We collected 16 Chinese HNPCC families from Wenzhou, Zhejiang Province, China. Tumor tissues and peripheral white blood cells were studied using microdissection, microsatellite analysis, immunostaining of hMSH2 and hMLH1 proteins and direct DNA sequencing of hMSH2 and hMLH1 genes. RESULTS: (1) A total of 50 patients had CRC. Average age at diagnosis of the first CRC was 45.7 years; 40.9% and 28.7% of the CRCs were located proximal to the splenic flexure and in the rectum, respectively. Thirty-eight percent of the colorectal cancer patients had synchronous and metachronous CRC. 34.4% and 25% of the CRCs were poor differentiation cancer and mucinous adenocarcinoma, respectively. Fourteen extracoloni tumors were found, and the hepatic cancer was the most common tumor type. Twenty-one patients whose median survival time was 5.7 years died during 1-23 years. Twenty-nine patients have survived for 1-28 years, 58.6%, 41.4% and 24.1% patients have survived for more than 5, 10 and 15 years, respectively; (2) All nine tumor-tissues showed microsatellite instability (MSI) at more than two loci. Four tumor-tissues lost hMSH2 protein expression and one lost hMLH1 protein expression. Three pathological germline mutations were identified from five genetically analyzed families; two of three mutations had not been reported previously as they were a transition from C to A in exon 14 (codon 743) of hMSH2 and a TIC deletion in exon 14 (codon 530)of hMLH1. CONCLUSION: Chinese HNPCC have specific clinicopathological features, such as early onset, propensity to involve the proximal colon, and high frequency of multiple CRCs, liver cancer more frequent than endometrial cancer. Chinese HNPCC showed relatively frequent germline mutation of mismatch repair (MMR) genes that correlated closely with high-level MSI and loss of expression of MMR genes protein.     

Reduced expression of cyclooxygenase 2 proteins in hereditary nonpolyposis colorectal cancers relative to sporadic cancers.

BACKGROUND & AIMS: Cyclooxygenase (COX) enzymes catalyze the conversion of arachidonic acid to prostaglandins. Evidence suggests that nonsteroidal anti-inflammatory drugs reduce the risk of colorectal cancer (CRC) and that this effect is mediated through COX inhibition. We analyzed and compared expression of the inducible COX-2 isoform in colorectal neoplasms from patients with hereditary nonpolyposis colorectal cancer (HNPCC), familial adenomatous polyposis (FAP), and sporadic CRC. Given that COX-2 is induced by transforming growth factor (TGF)-beta and that TGF-beta type II receptor (RII) mutations are found in HNPCCs, we determined the relationship between RII status and COX-2 expression. METHODS: COX-2 protein expression was determined in colorectal epithelia using immunohistochemistry and Western blotting. Patients with HNPCC had known mutations in hMLH1 or hMSH2 genes and/or met the Amsterdam criteria. In CRCs from HNPCC cases, mutations were sought in the coding region of the RII gene using the polymerase chain reaction. RESULTS: COX-2 was detected in adenomas from 2 of 3 HNPCC, 6 of 7 FAP, and 5 of 8 sporadic cases. In CRCs, COX-2 staining was found in 16 of 24 (67%) HNPCC vs. 24 of 26 (92%) sporadic cases (P = 0.035) and in 2 of 2 FAP cases. Staining intensity was reduced in HNPCCs compared with sporadic CRCs (P = 0.035). Staining localized to the cytoplasm of neoplastic cells; normal epithelial cells were negative for COX-2. Overexpression of COX-2 in CRCs relative to normal mucosa was confirmed by Western blotting. TGF-beta RII mutations were detected in 12 of 14 HNPCCs examined, including 3 of 4 COX-2-negative and 9 of 10 COX-2-positive cancers. CONCLUSIONS: The frequency and intensity of COX-2 expression was significantly reduced in HNPCCs relative to sporadic CRCs, and was not a consequence of RII mutations. Given that many HNPCCs express COX-2, inhibition of this enzyme may be an important strategy to prevent CRC in these patients.     

The Two-Week Referral System for colorectal cancer—not fit for purpose

Purpose

The UK government target expects all suspected colorectal cancer (CRC) patients to be seen within the Two-Week Referral (TWR) system made by general practitioners. These guidelines originally derived from only level 5 evidence. However, this has significant impact on the workload for colorectal surgeons. The aim of the study is to investigate the effectiveness of this colorectal service and whether the referral criteria are predictive of CRC.

Methods

A retrospective study of all patients referred under the TWR guidance in 2010 was assessed. The first 573 TWRs were piloted for analysis. Clinical information from each patient was collected regarding TWR criteria and additional colorectal symptoms or risk factors. Multiple regression analysis was performed to determine which symptoms independently correlated with CRC.

Results

One hundred twenty-six CRCs were diagnosed via all methods of referral in 2010. There were 940 patients referred under the TWR guidelines in that year, when 50 CRC patients were identified. Amongst the 573 patients, 32 CRCs were diagnosed. Multiple regression analysis revealed tenesmus to be independently associated with CRC (p?=?0.003, Pearson’s r?=?0.09185). None of the individual TWR criteria confidently predicted CRC.

Conclusion

Our preliminary results suggest that the current TWR guidelines cannot effectively predict CRC. There is an urgent need for an evidence-based approach to referral criteria for suspected CRC.     

Aberrant protein expression and frequent allelic loss of MSH3 in colorectal cancer with low-level microsatellite instability

Purpose

High level of microsatellite instability (MSI-H) in colorectal cancer (CRC) is caused by the inactivation of mismatch repair (MMR) genes; however, it is unknown for tumors with low level MSI (MSI-L). The protein complex involving MSH3 preferentially recognizes insertion/deletion loops (IDLs) of two to eight bases and di- and tetranucleotide repeats are affected in the majority of MSI-L CRC.

Methods

We selected 10 and eight MSI-L CRCs from 228 and 204 patients with sporadic and hereditary disease, respectively. The tumors were analyzed for protein expression of MSH3, MSH2, MSH6, MLH1, and PMS2, and for mutations and loss of heterozygosity (LOH) in MSH3.

Results

Four tumors showed a markedly reduced MSH3 expression, whereas all 18 tumors had normal expression of the remaining MMR proteins. Twenty-five different sequence variants were identified. None of these results in a truncated protein, though L902W represents the first constitutional missense mutation in MSH3 predicted to be functional based on conservation among mutS homologues. All variants have also been found in normal DNA of the patients and in controls. LOH intragenic to MSH3 was evident for 12 of 16 (75%) informative tumors.

Conclusions

Occurrence of sequence variants in normal DNA of the patients and in controls excludes somatic mutations and mutations specific to the CRC patient population, respectively. In contrast, the high frequency of LOH as well as the aberrant protein expression in some tumors indicates an involvement of MSH3 impairment in MSI-L CRC.     

The American College of Gastroenterology Emily Couric Lecture--the adenoma-carcinoma sequence revisited: has the era of genetic tailoring finally arrived?

Colorectal cancer (CRC) remains a common and often lethal disease. The classic adenoma-carcinoma sequence was defined on histologic grounds but over the last 25 years, the molecular basis of this process has been progressively clarified. There are at least three distinct molecular pathways to CRC: the chromosomal instability (CIN) pathway is thought to be largely driven by mutational events in oncogenes and tumor suppressor genes, the microsatellite instability pathway is responsible for Lynch syndrome CRCs and is driven by mutations in one of the DNA mismatch repair genes, and the epigenetic pathway is thought to be driven in large part by hypermethylation-induced silencing of tumor suppressor-like genes. The molecular understanding of this sequence has had a profound impact on our understanding of the process(s) of colonic carcinogenesis and this understanding has begun to change the clinical care of patients with colonic polyps and cancer including changes in therapy of established CRCs (anti-epidermal growth factor receptor antibody therapy is no longer offered to patients with mutant KRAS CRCs), identification of high-risk groups (diagnosis of Lynch syndrome by molecular analysis of CRCs) and the management of precursor lesions (identification of the serrated polyp pathway to CRC).