Germline variants in POLE are associated with early onset mismatch repair deficient colorectal cancer

Germline variants affecting the exonuclease domains of POLE and POLD1 predispose to multiple colorectal adenomas and/or colorectal cancer (CRC). The aim of this study was to estimate the prevalence of previously described heterozygous germline variants POLE c.1270C>G, p.(Leu424Val) and POLD1 c.1433G>A, p.(Ser478Asn) in a Dutch series of unexplained familial, early onset CRC and polyposis index cases. We examined 1188 familial CRC and polyposis index patients for POLE p.(Leu424Val) and POLD1 p.(Ser478Asn) variants using competitive allele-specific PCR. In addition, protein expression of the POLE and DNA mismatch repair genes was studied by immunohistochemistry in tumours from POLE carriers. Somatic mutations were screened using semiconductor sequencing. We detected three index patients (0.25%) with a POLE p.(Leu424Val) variant. In one patient, the variant was found to be de-novo. Tumours from three patients from two families were microsatellite instable, and immunohistochemistry showed MSH6/MSH2 deficiency suggestive of Lynch syndrome. Somatic mutations but no germline MSH6 and MSH2 variants were subsequently found, and one tumour displayed a hypermutator phenotype. None of the 1188 patients carried the POLD1 p.(Ser478Asn) variant. POLE germline variant carriers are also associated with a microsatellite instable CRC. POLE DNA analysis now seems warranted in microsatellite instable CRC, especially in the absence of a causative DNA mismatch repair gene germline variant.     

Familial and hereditary colorectal cancer with emphasis on the hereditary non-polyposis colorectal cancer syndrome

Previously, the role of the pathologist was restricted to the primary diagnosis of cancer. Recent developments in the field of molecular pathology now show that effective tools such as microsatellite instability analysis in combination with immuno-histochemistry can also identify a so-called mismatch repair defect and guide germline mutation testing in families with clustering of colorectal cancer. In this review, we come up with practical guidelines for the pathologist as we use them in daily practice. Furthermore, we discuss the (clinical) consequences of such developments.     

Risk of colorectal cancer for carriers of a germ-line mutation in POLE or POLD1

BackgroundGerm-line mutations in the exonuclease domains of the POLE and POLD1 genes are associated with an increased, but yet unquantified, risk of colorectal cancer (CRC).MethodsWe identified families with POLE or POLD1 variants by searching PubMed for relevant studies prior to October 2016 and by genotyping 669 population-based CRC cases diagnosed in patients under 60 years of age, from the Australasian Colorectal Cancer Family Registry. We estimated the age-specific cumulative risks (penetrance) using a modified segregation analysis.ResultsWe observed 67 CRCs (mean age at diagnosis = 50.2 (SD = 13.8) years) among 364 first- and second- degree relatives from 41 POLE families, and 6 CRCs (mean age at diagnosis = 39.7 (SD = 6.83) years) among 69 relatives from 9 POLD1 families. We estimated risks of CRC up to the age of 70 years (95% confidence interval) for males and females, respectively, to be 40% (26–57%) and 32% (20–47%) for POLE mutation carriers and 63% (15–99%) and 52% (11–99%) for POLD1 mutation carriers.ConclusionCRC risks for POLE mutation carriers are sufficiently high to warrant consideration of annual colonoscopy screening and implementation of management guidelines comparable to those applied in cases of Lynch syndrome. Refinement of estimates of CRC risk for POLD1 carriers is needed; however, clinical management recommendations could follow those made for POLE carriers.     

Diagnostic application of hMLH1 methylation in hereditary non-polyposis colorectal cancer

Colorectal cancer (CRC) due to mismatch repair (MMR) defect has distinct characteristics among unselected CRCs. These CRCs are biologically less aggressive and, thus, showing better prognosis but less sensitive to the 5FU-based chemotherapy. CRCs with MMR defect derive from both hereditary and sporadic reasons. Germline inactivation of MMR genes (hMLH1, hMSH2, hMSH6, and hPMS2) underlies the hereditary CRC with MMR defect (Lynch syndrome) and epigenetic silencing of hMLH1 gene causes the sporadic CRC with MMR defect. Hereditary and sporadic CRC with MMR defect can be detectable by microsatellite instability (MSI) test or immunohistochemical analysis among general CRCs. Lynch syndrome can be diagnosed by the clinical criteria or by genetic test to detect pathogenic germline mutations in MMR genes. However, both clinical criteria and genetic test are inadequate for the diagnosis of Lynch syndrome. Since genetic test for the diagnosis of the Lynch syndrome is expensive and not always identify pathogenic germline mutations, effective and inexpensive screening program is desirable. Here we propose a possible application of methylation test combined with MSI or pathological analysis as an effective and a cost-saving new strategy for screening of Lynch syndrome.     

Role of POLE and POLD1 in familial cancer

PurposeGermline pathogenic variants in the exonuclease domain (ED) of polymerases POLE and POLD1 predispose to adenomatous polyps, colorectal cancer (CRC), endometrial tumors, and other malignancies, and exhibit increased mutation rate and highly specific associated mutational signatures. The tumor spectrum and prevalence of POLE and POLD1 variants in hereditary cancer are evaluated in this study.MethodsPOLE and POLD1 were sequenced in 2813 unrelated probands referred for genetic counseling (2309 hereditary cancer patients subjected to a multigene panel, and 504 patients selected based on phenotypic characteristics). Cosegregation and case–control studies, yeast-based functional assays, and tumor mutational analyses were performed for variant interpretation.ResultsTwelve ED missense variants, 6 loss-of-function, and 23 outside-ED predicted-deleterious missense variants, all with population allele frequencies <1%, were identified. One ED variant (POLE p.Met294Arg) was classified as likely pathogenic, four as likely benign, and seven as variants of unknown significance. The most commonly associated tumor types were colorectal, endometrial and ovarian cancers. Loss-of-function and outside-ED variants are likely not pathogenic for this syndrome.ConclusionsPolymerase proofreading–associated syndrome constitutes 0.1–0.4% of familial cancer cases, reaching 0.3–0.7% when only CRC and polyposis are considered. ED variant interpretation is challenging and should include multiple pieces of evidence.     

Concurrent pathogenic variations in patients with hereditary cancer syndromes

Cancer is a multifactorial disorder; however, 5–10% of all cancers show hereditary background. In recent years many targeted next generation sequencing panels comprising cancer predisposition genes have been developed and used for diagnostic purposes in patients with increased cancer risk. Screening multiple genes at a time allows multiple variants in different genes to be detected as well. This study aims to determine the cases with concurrent mutations in different hereditary cancer predisposition genes and how they are clinically affected. Here, we screened 1090 index cases by next generation sequencing based hereditary cancer panels and evaluated the reflection of multiple variations on the phenotype. We detected 11 (1%) cases with pathogenic variants in more than one gene. These concurrent variations occurred mostly in BRCA1/2 (7/11) accompanied with MUTYH, ATM, CHECK2, NBN, and RAD50. In addition, MUTYH&ATM, NBN&MSH6, MUTYH&CHEK2 double heterozygous cases were detected. Moreover, we identified a case with three heterozygous variations in CDH1, MUTYH, and CHEK2. These patients presented malignancies that were mostly related to pathogenic variations they carried. Although they are rare, defining double heterozygous cases is important for managing appropriate therapy and accurate genetic consulting for the patients and family members.     

Seven novel MLH1 and MSH2 germline mutations in hereditary nonpolyposis colorectal cancer

Hereditary nonpolyposis colorectal cancer (HNPCC) is the most frequent hereditary form of colorectal cancer and is caused by germline mutations in mismatch repair (MMR) genes. The majority of mutations occur in MLH1 and MSH2. We report hereby seven novel germline mutations in these two genes (five in MLH1 and two in MSH2). All mutations have been found in families fulfilling criteria of the Bethesda guidelines and four of which also fulfilled the Amsterdam criteria. We identified three insertions or deletions of 1 bp leading to premature stop codons (MLH1: c.341delC, c.1413‐1414insA; MSH2: c.1119delG) and three nonsense mutations (MLH1: c.67G>T [E23X], c.436C>T [Q146X]; MSH2: c.1857T>G [Y619X]). The corresponding tumors showed a high level of microsatellite instability (MSI‐H) and a complete loss of expression of the affected protein. In addition, a missense mutation in MLH1 was identified (c.1984A>C [T662P]). The respective tumor also showed a high level of microsatellite instability but a reduced, rather then lost, expression of the MLH1‐protein. This missense mutation was not found in 107 healthy control individuals and in 54 HNPCC patients. © 2001 Wiley‐Liss, Inc.     

Frequency of hereditary non-polyposis colorectal cancer among Uruguayan patients with colorectal cancer

Few studies have investigated the frequency of hereditary non-polyposis colorectal cancer (HNPCC) in patients with colorectal cancer (CRC), and these have shown marked geographic variations. The aim of this study was to estimate the frequency of HNPCC in a cohort of Uruguayan CRC patients. We included all patients operated consecutively for CRC in the Hospital Central de las Fuerzas Armadas (Uruguay) between 1987 and 2003. Cases were classified into three groups: (i) those fulfilling Amsterdam criteria; (ii) those not fulfilling Amsterdam criteria but considered as a population at increased risk of cancer; and (iii) sporadic CRC. Genetic analysis to detect point mutations in hMLH/hMSH2/hMSH6 genes was performed in group 1 patients. Cases not showing mutations were tested by multiplex ligation-dependent probe amplification. Among 461 patients, group 1 represented 2.6%, group 2 represented 5.6%, and sporadic cases 91.8%. hMLH1/hMSH2/hMSH6 mutations were found in 25% of cases classified as HNPCC (two in hMLH1 and one in hMSH2). No mutations were detected in hMSH6 gene. The proportion of CRC patients that fulfilled Amsterdam criteria agrees with other reports. However, the percentage of HNPCC cases with identified mutations (25%) may be lower than that reported from other populations. This may reflect, among other possible causes, a different genetic profile in the Uruguayan population.     

遗传性非息肉性结直肠癌家系的MLH1基因两个胚系新突变

目的初步评价遗传性非息肉性结直肠癌（HNPCC）胚系MLH1基因突变中新突变的病理性。方法收集符合AmsterdamⅡ标准的12个不同家系的12例患者外周血,用特异引物和耐热性逆转录酶特异地逆转录MLH1的mRNA;利用长模板PCR扩增酶扩增逆转录产物（cDNA）;测序分析扩增产物;利用PCR-Genescan技术和免疫组织化学染色分别检测有新突变患者肿瘤组织的5个微卫星位点（BAT26,BAT25,D5S346,D2S123和Mfd15）和MLH1蛋白的表达。结果在4例患者中检出4个MLH1突变,其中2个突变为第12外显子的第384密码子（1151bp处）GTT→GAT的突变,该突变是已报道的病理性突变;另外2个突变分别是第8外显子的第217密码子（649bp处）CGC→TGC突变和第16外显子的第581密码子（1742bp处）CC→CTG突变;后两者为尚未报道的新突变。2个新突变的患者肿瘤组织均呈高度微卫星不稳定性,两者的瘤组织MLH1蛋白均失表达。结论MLH1第8外显子的第217密码子突变和第16外显子的第581密码子的两个新突变很可能为病理性突变。     

PALB2 variants in hereditary and unselected Finnish Prostate cancer cases

Background  

PALB2 1592delT mutation is associated with increased breast cancer and suggestive prostate cancer (PRCA) risk in Finland. In this study we wanted to assess if any other PALB2 variants associate to increased PRCA risk and clinically describe patients with formerly found PALB2 1592delT mutation.     

Carrier risk status changes resulting from mutation testing in hereditary non-polyposis colorectal cancer and hereditary breast-ovarian cancer

Context: In hereditary cancer syndrome families with an identified cancer associated mutation, mutation testing changes the carrier risk status of the tested person and may change the carrier risk status of relatives.

Objective: This study aimed to describe the change in the distribution of carrier risk status resulting from testing in hereditary breast-ovarian cancer (HBOC) and hereditary non-polyposis colorectal cancer (HNPCC) families.

Design: This was an observational cohort study.

Patients: The cohort included members of 75 HBOC and 47 HNPCC families. Of the 10 910 cohort members, 1408 were tested for a mutation and learned their test results.

Outcome measure: Carrier risk for all cohort members was assessed before and after mutation testing.

Results: There was a change in carrier risk status in 2906 subjects after testing of 1408 family members. The most common type of carrier risk change, from at risk to non-carrier status, accounted for 77% of the risk changes; 12% were a change to known carrier status from a lower risk. Sixty percent of persons with a carrier risk status change were not themselves tested; their risk status changed because of a relative's test result.

Conclusions: Carrier risk status changes from uncertainty to certainty (that is, to carrier or to non-carrier) account for 89% of risk changes resulting from testing. These risk changes affect cancer prevention recommendations, most commonly reducing their burden. Current practices do not ensure that untested family members are informed about changes in their carrier risk status which result from mutation testing of their relatives.

     

Cyclin D1 rare variants in UK multiple adenoma and early-onset colorectal cancer patients

We examined the influence that rare variants and low-frequency polymorphisms in the cancer candidate gene CCND1 have on the development of multiple intestinal adenomas and the early onset of colorectal cancer. Individuals with <100 multiple polyps and patients with colorectal cancer diagnosed before 50 years of age were recruited in UK, and screened for sequence changes in the coding and regulatory regions of CCND1. A set of about 800 UK control individuals was genotyped for the variants discovered in the cases. Variants in the promoter, intron-exon boundaries and untranslated regions of the CCND1 gene had higher frequencies in cases than in controls. Five of these variants were typed in a set of French multiple adenoma and early-onset patients, who also showed higher allele frequencies than UK controls. When pooled together, variants with frequencies lower than 1% conferred an increased risk of disease that was significant in the multiple adenoma group (odds ratio (OR) 2.2; 95% confidence interval, 1.1-4.4; P = 0.03). Most variants had a putative functional effect when assessed in silico. We conclude that rare variants of CCND1 are risk factors for colorectal cancer, with considerably larger effects than common polymorphisms, and as such should be systematically evaluated in susceptibility studies.     

Genetic epidemiology of hereditary non-polyposis colorectal cancer syndromes in Modena, Italy: results of a complex segregation analysis

Complex segregation analysis was conducted in a series of patients with hereditary non-polyposis colorectal cancer (HNPCC) ascertained through probands registered in the Cancer Registry of the Health Care District of Modena in Northern Italy. Altogether there were 71 nuclear families segregating for HNPCC in 28 pedigrees. The analysis favoured the two-loci model, in which the segregation at the major locus is compatible with codominant transmission with a frequency of 0·0044 for the high-risk allele for HNPCC and a lifetime penetrance of 0·728 for heterozygotes.     

Neuroendocrine differentiation in sporadic CRC and hereditary nonpolyosis colorectal cancer

Extent neuroendocrine differentiation can be encountered in many human neoplasm derived from different organs and systems using immunohistochemistry and ultrastructural techniques. The tumor cells' behaviors resemble those of neurons and neuroendocrine cells. The presence of neuroendocrine differentiation reputedly appears to be associated with a poorer prognosis than the adenocarcinoma counterparts in sporadic human neoplasm. In this review the neuroendocrine carcinoma and the adenocarcinoma with neuroendocrine differentiation of colon and rectum both in sporadic colorectal carcinoma and the hereditary nonpolyposis colorectal cancer, the relationship of neuroendocrine differentiation and some possible molecular pathways in tumorogenesis of colorectal cancer will be discussed. Possible treatment strategy will also be addressed.