Hereditary Colorectal Cancer Syndrome Research Articles

Adolescent and Young Adult Colorectal Cancer

Although the overall incidence of colorectal cancer (CRC) in adolescents and young adults (AYAs) is low, it has seen an increase over the past 2 to 3 decades, which contrasts with the trend of decreased incidence in the older population. This phenomenon is conceivably caused by a lack of routine CRC screening in the young population and lifestyle issues, including the obesity epidemic and dietary factors. Hereditary genetic syndromes (eg, familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer syndrome) and known predisposing medical conditions (eg, inflammatory bowel disease) account for only a minority of CRC cases in AYA. Younger patients with CRC commonly present with more advanced disease at diagnosis and exhibit specific molecular and clinical characteristics associated with a distinct biologic phenotype of CRC compared with older individuals. Matched for stage, however, the prognosis of patients with young-onset CRC is similar to or better than that for older patients. A surprising paucity of data exists on outcomes associated with modern systemic cytotoxic and biologic therapy specifically in young patients with CRC. The toxicity pattern of these treatments, however, differs between young and older patients, partly because of the lower rate of pertinent comorbidities in younger adults. Issues regarding surgical management in the setting of hereditary syndromes and fertility preservation while on therapy are of particular importance to the younger patient population. Future studies should seek to increase understanding of the distinct tumor biology of AYA patients with CRC and the consequences of treatment interventions to optimize outcomes for this population.

Familial risk-colorectal cancer: ESMO Clinical Practice Guidelines

J. Balmana1, F. Balaguer2, A. Cervantes3 & D. Arnold4, on behalf of the ESMO Guidelines Working Group* Department of Medical Oncology, Hospital Vall d’Hebron, Vall d’Hebron Institute of Oncology (VHIO), Universitat Autonoma de Barcelona, Barcelona; Department of Gastroenterology, Hospital Clinic, CIBERehd, IDIBAPS, University of Barcelona, Barcelona; Department of Hematology and Medical Oncology, INCLIVA, University of Valencia, Valencia, Spain; Department of Medical Oncology, Tumor Biology Clinic, Albert Ludwigs University, Freiburg, Germany;

Clinical significance of microsatellite instability in colorectal cancer

Colorectal cancer is a heterogeneous tumor type with regard to molecular pathogenesis and genetic instability. The majority of colorectal cancers display chromosomal instability and follow the classical adenoma-carcinoma sequence of tumor progression. A subset of about 15% of colorectal cancers, however, displays DNA mismatch repair (MMR) deficiency and the high-level microsatellite instability (MSI-H) phenotype. MSI-H colorectal cancers can occur as sporadic tumors or in the context of hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome. The MSI-H phenotype is a hallmark of Lynch syndrome-associated cancers, which is of diagnostic relevance for the identification of Lynch syndrome mutation carriers. MSI-H colorectal cancers are characterized by a distinct clinical behavior, which results from their particular molecular pathogenesis and gives microsatellite instability testing its clinical significance. The MSI-H phenotype shows association with proximal tumor localization, a dense local lymphocyte infiltration, and a low frequency of distant organ metastasis. Moreover, MSI-H colorectal cancers have a better prognosis than their microsatellite-stable counterparts. A distinct responsiveness of MSI-H colorectal cancer patients towards chemotherapy has been shown in several studies. The clinical characteristics of MSI-H cancers are closely linked to their molecular pathogenesis, and research on the molecular alteration characteristic of MSI-H cancers may provide the basis for novel diagnostic or therapeutic approaches.

Hereditary Syndromes With Associated Renal Neoplasia

Many hereditary tumor syndromes are associated with neoplasms of the kidney. It is becoming increasingly well recognized that a given familial tumor syndrome may be very heterogenous in clinical appearance and that unrecognized patients may present initially for the treatment of a renal mass. It is therefore important for surgical pathologists to be aware of the specific gross and microscopic findings in the kidney that suggest a possible syndromic association. In this review, we detail the histologic features of syndromic-associated renal neoplasms, describe the presence of characteristic changes in the background renal parenchyma, and provide an update on associated extrarenal manifestations for each of the following syndromes: von Hippel-Lindau disease, hereditary papillary renal cell carcinoma (RCC), hereditary leiomyomatosis-RCC, Birt-Hogg-Dubé syndrome, tuberous sclerosis complex, germline succinate dehydrogenase mutation, hereditary nonpolyposis colorectal cancer syndrome, hyperparathyroidism-jaw tumor syndrome, PTEN hamartoma syndrome, constitutional chromosome 3 translocation, and familial nonsyndromic clear cell RCC. We also include a synopsis of renal medullary carcinoma because of its association with hereditary hemoglobinopathies.

Telomere Length and Genetic Anticipation in Lynch Syndrome

Telomere length variation has been associated with increased risk of several types of tumors, and telomere shortening, with genetic anticipation in a number of genetic diseases including hereditary cancer syndromes. No conclusive studies have been performed for Lynch syndrome, a hereditary colorectal cancer syndrome caused by germline mutations in the DNA mismatch repair genes. Here we evaluate telomere length in Lynch syndrome, both as a cancer risk factor and as a mechanism associated with anticipation in the age of cancer onset observed in successive generations of Lynch syndrome families. Leukocyte telomere length was measured in 244 mismatch repair gene mutation carriers from 96 Lynch syndrome families and in 234 controls using a monochrome multiplex quantitative PCR method. Cancer-affected mutation carriers showed significantly shorter telomeres than cancer-free mutation carriers. In addition, cancer-affected carriers showed the most pronounced shortening of telomere length with age, compared with unaffected carriers. The anticipation in the age of cancer onset observed in successive generations was not associated with telomere shortening, although, interestingly, all mother-son pairs showed telomere shortening. In conclusion, cancer-affected mismatch repair gene mutation carriers have distinct telomere-length pattern and dynamics. However, anticipation in the age of onset is not explained by telomere shortening. Pending further study, our findings suggest that telomere attrition might explain the previously reported dependence of cancer risk on the parent-of-origin of mismatch repair gene mutations.

MUTYH-associated colorectal cancer and adenomatous polyposis

MUTYH-associated polyposis (MAP) was first described in 2002. MUTYH is a component of a base excision repair system that protects the genomic information from oxidative damage. When the MUTYH gene product is impaired by bi-allelic germline mutation, it leads to the mutation of cancer-related genes, such as the APC and/or the KRAS genes, via G to T transversion. MAP is a hereditary colorectal cancer syndrome inherited in an autosomal-recessive fashion. The clinical features of MAP include the presence of 10-100 adenomatous polyps in the colon, and early onset of colorectal cancer. Ethnic and geographical differences in the pattern of the MUTYH gene mutations have been suggested. In Caucasian patients, c.536A>G (Y179C) and c.1187G>A (G396D) mutations are frequently detected. In the Asian population, Y179C and G396D are uncommon, whereas other variants are suggested to be the major causes of MAP. We herein review the literature on MUTYH-associated colorectal cancer and adenomatous polyposis.

Practical genetics of colorectal cancer.

Hereditary colorectal cancer (CRC) is highly heterogeneous, both genotypically and phenotypically. The most frequently occurring hereditary colorectal cancer syndrome is Lynch syndrome, accounting for approximately 3% of the total colorectal cancer burden. Polyposis syndromes, such as familial adenomatous polyposis, account for a lesser percentage. Familial colorectal cancer, defined by family history, occurs in an estimated 20% of all colorectal cancer cases. With a worldwide annual colorectal cancer incidence of over one million, and annual mortality of over 600,000, hereditary and familial forms of colorectal cancer are a major public health problem. Lynch syndrome is attributable to DNA mismatch repair germline mutations, with the MSH2, MLH1, MSH6, and PMS2 genes being implicated. The characteristics of Lynch syndrome-associated colorectal tumors, including early age of onset and predilection to the proximal colon, mandate surveillance by colonoscopy beginning by age 20 to 25 and repeated every other year through age 40 and annually thereafter. Besides colorectal cancer, Lynch syndrome also predisposes to a litany of extracolonic cancers, foremost of which is endometrial cancer, followed by cancer of the ovary, stomach, renal pelvis and ureter, small bowel, hepatobiliary tract, pancreas, glioblastoma multiforme in the Turcot's variant, and sebaceous skin tumors in the Muir-Torre variant and, more recently identified, cancers of the breast and prostate. The most common polyposis syndrome is familial adenomatous polyposis, caused by mutations in the APC gene. Affected individuals have multiple colonic adenomas and, without treatment invariably develop colorectal cancer. Colonic surveillance with polypectomy may be pursued until the appearance of multiple colonic adenomas, at which time prophylactic colectomy should be considered. Extra-intestinal manifestations include desmoid tumor, hepatoblastoma, thyroid carcinoma, and medulloblastoma. Other polyposis syndromes include the hamartomatous polyp syndromes, including juvenile polyposis syndrome, Peutz-Jeghers syndrome, Cowden syndrome, and Bannayan-Ruvalcaba-Riley syndrome.

Simple Detection of Germline Microsatellite Instability for Diagnosis of Constitutional Mismatch Repair Cancer Syndrome

Heterozygous mutations in DNA mismatch repair (MMR) genes result in predisposition to colorectal cancer (hereditary nonpolyposis colorectal cancer or Lynch syndrome). Patients with biallelic mutations in these genes, however, present earlier, with constitutional mismatch repair deficiency cancer syndrome (CMMRD), which is characterized by a spectrum of rare childhood malignancies and café-au-lait skin patches. The hallmark of MMR deficiency, microsatellite instability (MSI), is readily detectable in tumor DNA in Lynch syndrome, but is also present in constitutional DNA of CMMRD patients. However, detection of constitutional or germline MSI (gMSI) has hitherto relied on technically difficult assays that are not routinely applicable for clinical diagnosis. Consequently, we have developed a simple high-throughput screening methodology to detect gMSI in CMMRD patients based on the presence of stutter peaks flanking a dinucleotide repeat allele when amplified from patient blood DNA samples. Using the three different microsatellite markers, the gMSI ratio was determined in a cohort of normal individuals and 10 CMMRD patients, with biallelic germline mutations in PMS2 (seven patients), MSH2 (one patient), or MSH6 (two patients). Subjects with either PMS2 or MSH2 mutations were easily identified; however, this measure was not altered in patients with CMMRD due to MSH6 mutation.

Hereditary colorectal cancer and Lynch syndrome.

The term Hereditary Nonpolyposis Colorectal Cancer, or HNPCC, has been less used for naming the classical autosomal dominantly inherited susceptibility to cancer [1]. As this susceptibility applies to tumors from different primary sites other than but including colorectal cancer (CRC), the term Lynch Syndrome (LS) is a less restrictive name. Lynch Syndrome is characterized by an autosomal dominantly inherited susceptibility to cancer, caused by inherited germline mutations in the mismatch repair (MMR) genes. It is characterized by early age of onset, predilection to the proximal colon, multiple primary CRCs, and extracolonic tumors, particularly endometrium carcinoma (EC) [2,3]. To establish a profile of the disease, a better definition of the spectrum of related tumors has been a constant concern [4,5]. It is therefore expected to find heterogeneity among the families regarding the susceptibility to develop tumors in different specific sites. The risk of cancer in fact varies among families with LS, although the variation does not necessarily result from genetic heterogeneity. The standards of environmental exposure must contribute to the differential gene expression, justifying at least in part this heterogeneity [6]. LS accounts for 2%–5% of all CRC cases [7]. In fact, it is believed that 20% to 30% of patients with CRC present some type of genetic susceptibility, but without meeting criteria for known typical syndromes. However, new cancer cases in the patient’s family or supplemental information on previously unknown cases can lead to a reclassification that may characterize a typical syndrome. In other situations, despite the lack of clinical criteria for determining an inherited character, molecular inquiry can define the diagnosis of inherited syndrome. For these reasons, even in the absence of typical clinical characterization, criteria must be used to direct the inquiry of an inherited condition. The spectrum of extracolonic tumors in LS began to be the subject of several publications in which the most common cancers found were those affecting the endometrium, the stomach and the urinary tract [8-14]. Watson and Lynch [6] calculated the frequency of cancer in other specific sites in 1,300 high-risk individuals from 23 families having LS and demonstrated a significant increase of the risk of developing cancer in the stomach (RR:4.1), small bowel (RR:25), kidneys (RR:3.2), ureter (RR:22), and ovary (RR:3.5). The proposed extracolonic cancers associated with LS are endometrium, stomach, ovary, small bowel, ureter, renal pelvis, brain, and hepatobiliary tract. Among these tumors, endometrium, ureter, renal pelvis, and small bowel cancers present the highest relative risk, and are therefore the most specific for LS. The Amsterdam criteria for clinical diagnosis of LS are: (1) at least three relatives must have histologically verified CRC, endometrium, ureter, renal pelvis, or small bowel cancer; (2) one must be a first-degree relative of the other two; (3) at least two successive generations must be affected; (4) at least one of the relatives with cancer must have received the diagnosis before age 50; and (5) familial adenomatous polyposis must have been excluded. Because there are families with an MMR mutation present exclusively in patients with endometrial cancer without CRC, the requirement of at least one case of CRC was suppressed [15,16]. Patients with LS may also have sebaceous adenomas, sebaceous carcinomas, and multiple keratoacanthomas, findings consonant with Torre’s syndrome variant [17,18]. The definition of LS includes a familial clustering of colorectal and/or endometrial cancer and as associated cancers stomach, ovary, ureter/renal pelvis, brain, small bowel, hepatobiliary tract, and skin (sebaceous tumors) tumors [15,19]. As discussed by Vasen [20], since it is known that LS is caused by an mismatch repair gene defect and that the hallmark of the syndrome is microsatellite instability (MSI), more attention should be given to the so-called Bethesda guidelines, which describe almost all clinical conditions in which there is suspicion of LS and in which a search for MSI is indicated, mainly early onset of colorectal adenomas and cancer.

Features of Adenoma and Colonoscopy Associated With Recurrent Colorectal Neoplasia Based on a Large Community-Based Study

We investigated adenoma and colonoscopy characteristics that are associated with recurrent colorectal neoplasia based on data from community-based surveillance practice. We analyzed data of 2990 consecutive patients (55% male; mean age 61 years) newly diagnosed with adenomas from 1988 to 2002 at 10 hospitals throughout The Netherlands. Medical records were reviewed until December 1, 2008. We excluded patients with hereditary colorectal cancer (CRC) syndromes, a history of CRC, inflammatory bowel disease, or without surveillance data. We analyzed associations among adenoma number, size, grade of dysplasia, villous histology, and location with recurrence of advanced adenoma (AA) and nonadvanced adenoma (NAA). We performed a multivariable multinomial logistic regression analysis to estimate odds ratios (ORs) and 95% confidence intervals (CIs). During the surveillance period, 203 (7%) patients were diagnosed with AA and 954 (32%) patients with NAA. The remaining 1833 (61%) patients had no adenomas during a median follow-up of 48 months. Factors associated with AA during the surveillance period included baseline number of adenomas (ORs ranging from 1.6 for 2 adenomas; 95% CI: 1.1-2.4 to 3.3 for ≥5 adenomas; 95% CI: 1.7-6.6), adenoma size ≥10 mm (OR = 1.7; 95% CI: 1.2-2.3), villous histology (OR = 2.0; 95% CI: 1.2-3.2), proximal location (OR = 1.6; 95% CI: 1.2-2.3), insufficient bowel preparation (OR = 3.4; 95% CI: 1.6-7.4), and only distal colonoscopy reach (OR = 3.2; 95% CI: 1.2-8.5). Adenoma number had the greatest association with NAA. High-grade dysplasia was not associated with AA or NAA. Large size and number, villous histology, proximal location of adenomas, insufficient bowel preparation, and poor colonoscopy reach were associated with detection of AA during surveillance based on data from community-based practice. These characteristics should be used jointly to develop surveillance policies for adenoma patients.

Clinical characterization and mutation spectrum in Hispanic families with adenomatous polyposis syndromes

Several genetically defined hereditary colorectal cancer (CRC) syndromes are associated with colonic polyposis including familial adenomatous polyposis (FAP) and MUTYH adenomatous polyposis (MAP). Limited data exists on the clinical characterization and genotypic spectrum of polyposis syndromes among Hispanics. To describe the phenotype and genotype of Puerto Rican Hispanic patients with FAP and MUTYH and compare with other ethnic and racial groups. Probands were identified from the Puerto Rico Familial Colorectal Cancer Registry (PURIFICAR). Recruited individuals completed risk factors, medical, and family history questionnaires and underwent genetic testing for genotype analysis. Frequency analysis, Chi square, Fisher's exact and Wilcoxon rank-sum tests were used for statistical analysis methods. A total of 31 FAP (from 19 families) and 13 MAP (from 13 families) Hispanic patients recruited from the PURIFICAR were evaluated. Among the FAP cases, mean age at diagnosis was 27.6 (range 9-71 years); 67.7 % cases had more than 100 polyps and 41.9 % had upper gastrointestinal polyps. Among the 19 FAP families, there were 77 affected FAP individuals and 26 colorectal cancer cases. Genetic mutations were available for 42.2 % of FAP families; all mutations identified were unique. Surgeries were reported in 31 cases; 14 (45.2 %) prophylactic surgeries and 6 (19.4 %) therapeutic surgeries for management of CRC. Among MAP cases, mean age at diagnosis was 53 (range 34-76 years). Genetic analysis revealed homozygous biallelic mutations (G382D) in 53.8 %, compound heterozygous mutations (G382/Y165C) in 23 %, and non-G382/Y165C monoallelic mutations in 23 %. Familial cancer registries should be promoted as vehicles for detection, education and follow up of families at-risk of acquiring familial cancers. PURIFICAR is the first and only familial cancer registry in Puerto Rico providing these services to families affected with familial cancer syndromes promoting education, testing and surveillance of at-risk family members, and focusing on cancer prevention efforts. The fact that only 40 % of FAP patients had access to genetic testing stresses the need to promote the establishment of policies supporting genetic testing coverage by medical insurance companies in order to provide patients with the highest standard of care to prevent cancer. Furthermore, our results suggest that Hispanics may have uncommon mutations in adenomatous polyposis related genes, which emphasize the need for full gene sequencing to establish genetic diagnosis.

Ureteroscopic management of upper tract urothelial carcinoma (UTUC) in patients with Lynch Syndrome (hereditary nonpolyposis colorectal cancer syndrome)

To report our experience with ureteroscopic laser ablation of upper tract urothelial carcinoma (UTUC) in patients with Lynch Syndrome (LS), as defined by a documented germline mutation in the MSH-2 gene. To increase awareness among urologists about UTUC in this unique patient population and refer to genetic counselling when appropriate. Demographic, clinical and pathological data on 13 consecutive patients with UTUC and documented MSH-2 mutation comprising 15 involved renal units were retrospectively collected. Ureteroscopic evaluations involved biopsy and laser treatment with combination holmium/neodymium yttrium aluminum garnet (YAG) lasers. Tumours were graded from 1 to 3 according to the 1973 World Health Organisation classification by a single pathologist evaluating cell block preparations. The mean patient age at initial presentation was 56.5 years, with six of 13 patients having metachronous bilateral UT disease. The mean follow-up was 59 months with a mean number of surveillances of 12. Of 15 affected renal units, 10/15 (67%) of initial tumours involved the ureter with mean lesion size of 17.5 mm, while five of 15 (33%) involved the intrarenal collecting system with mean lesion size of 25 mm. Ureteroscopy cleared 13/15 (87%) lesions and four of those 13 (31%) needed staged procedures. Renal preservation rate was 14/15 (93%) with one nephroureterectomy and one segmental ureterectomy performed. One patient developed metastatic UTUC after 40 months surveillance. No patient presented with bladder tumours but seven of the 13 (54%) developed them within 10 months of the initial ureteroscopy. Patients with LS who develop UTUC present at younger ages and appear to be more likely to have bilateral UT disease over their lifetimes vs sporadic UTUC patients. Ureteroscopic laser ablation offers a good renal preservation rate with reasonable cancer control in patients willing to undergo endoscopic surveillance. Development of new bladder tumours is common.

Pathways of Colorectal Carcinogenesis

This review of the molecular and cellular changes in the different pathways of colorectal carcinogenesis sets out the classic adenoma-carcinoma sequence of the large bowel as a stepwise series of pathologic neoplastic changes associated with accumulation of genetic and epigenetic molecular alterations. The 2 major types of genomic instability found in colorectal cancers are chromosomal instability (CIN) and microsatellite instability (MSI). CIN is often associated with mutated APC. MSI is due to defective DNA mismatch repair. The associated familial cancer susceptibility syndromes are familial adenomatous polyposis coli, due to inherited APC mutations, and Lynch Syndrome or hereditary nonpolyposis colorectal cancer syndrome, due to inherited mutations in one of the mismatch repair genes (predominantly MLH1 and MSH2). In the CpG island methylator phenotype, a number of genes become transcriptionally silenced because of hypermethylation of their promoters, and this represents a key epigenetic mechanism of inactivation of tumor suppressor genes, including certain DNA repair genes. An overview of the contributions of CIN, MSI, and CpG island methylator phenotype to the different pathways of colorectal carcinogenesis allows categorization of colorectal cancers into 5 major groups on the basis of their molecular and pathologic characteristics.

Knowledge of and Practice Patterns for Hereditary Colorectal Cancer Syndromes in Korean Surgical Residents

PurposeObtaining a detailed family history through detailed pedigree is essential in recognizing hereditary colorectal cancer (CRC) syndromes. This study was performed to assess the current knowledge and practice patterns of surgery residents regarding familial risk of CRC.MethodsA questionnaire survey was performed to evaluate the knowledge and the level of recognition for analyses of family histories and hereditary CRC syndromes in 62 residents of the Department of Surgery, Seoul National University Hospital. The questionnaire consisted of 22 questions regarding practice patterns for, knowledge of, and resident education about hereditary CRC syndromes.ResultsTwo-thirds of the residents answered that family history should be investigated at the first interview, but only 37% of them actually obtained pedigree detailed family history at the very beginning in actual clinical practice. Three-quarters of the residents answered that the quality of family history they obtained was poor. Most of them could diagnose hereditary nonpolyposis colorectal cancer and recommend an appropriate colonoscopy surveillance schedule; however, only 19% knew that cancer surveillance guidelines differed according to the family history. Most of our residents lacked knowledge of cancer genetics, such as causative genes, and diagnostic methods, including microsatellite instability test, and indicated a desire and need for more education regarding hereditary cancer and genetic testing during residency.ConclusionThis study demonstrated that surgical residents' knowledge of hereditary cancer was not sufficient and that the quality of the family histories obtained in current practice has to be improved. More information regarding hereditary cancer should be considered in education programs for surgery residents.

Abdominal pain post endoscopic mucosal resection: Treat the patient not the CT scan

An 85-year-old female, with hereditary nonpolyposis colorectal cancer syndrome, underwent a colonoscopy and endoscopic mucosal resection (EMR) of a 25-mm proximal ascending colon polyp (Paris classification 0-Is). Post-procedure, the patient developed abdominal pain in the right iliac fossa which settled 1 h later. An urgent computed tomography (CT) scan of her abdomen was organised which happened 6 h post onset of abdominal pain. She had radiological evidence of perforation on the CT scan but clinically remained well and was managed conservatively. The exact aetiology of this patient's symptoms is not known. We suspect the radiological findings are probably due to a combination of injectate within the colonic wall and leakage of insufflated air or CO2 following transmural passage of the EMR needle. As EMR is becoming an increasingly effective treatment modality in the management of large sessile polyps, clinicians need to be aware of potential complications of treatment. It is also important to recognise that radiological features of perforation can be seen post EMR in the absence of an EMR associated perforation.

MUTYH the base excision repair gene family member associated with colorectal cancer polyposis.

sporadic (70-75%), familial (20-25%) and hereditary (5-10%). hereditary colorectal cancer syndromes classified into two different subtypes: polyposis and non polyposis. Familial Adenomatous polyposis (FAP; OMIM #175100) is the most common polyposis syndrome, account for <1% of colorectal cancer incidence and characterized by germline mutations in the Adenomatous polyposis coli (APC, 5q21- q22; OMIM #175100). FAP is a dominant cancer predisposing syndrome which 20-25% cases are de novo. There is also another polyposis syndrome; MUTYH associated polyposis (MAP, OMIM 608456) which it is caused by mutation in human Mut Y homologue MUTYH (MUTYH; OMIM 604933) and it is associated with multiple (15-100) colonic adenomas. In this paper we discuss MUTYH mechanism as an important member of Base Excision Repair (BER) family and its important role in polyposis condition.

MUTYH DNA glycosylase: the rationale for removing undamaged bases from the DNA

Maintenance of genetic stability is crucial for all organisms in order to avoid the onset of deleterious diseases such as cancer. One of the many proveniences of DNA base damage in mammalian cells is oxidative stress, arising from a variety of endogenous and exogenous sources, generating highly mutagenic oxidative DNA lesions. One of the best characterized oxidative DNA lesion is 7,8-dihydro-8-oxoguanine (8-oxo-G), which can give rise to base substitution mutations (also known as point mutations). This mutagenicity is due to the miscoding potential of 8-oxo-G that instructs most DNA polymerases (pols) to preferentially insert an Adenine (A) opposite 8-oxo-G instead of the appropriate Cytosine (C). If left unrepaired, such A:8-oxo-G mispairs can give rise to CG→AT transversion mutations. A:8-oxo-G mispairs are proficiently recognized by the MutY glycosylase homologue (MUTYH). MUTYH can remove the mispaired A from an A:8-oxo-G, giving way to the canonical base-excision repair (BER) that ultimately restores undamaged Guanine (G). The importance of this MUTYH-initiated pathway is illustrated by the fact that biallelic mutations in the MUTYH gene are associated with a hereditary colorectal cancer syndrome termed MUTYH-associated polyposis (MAP). In this review, we will focus on MUTYH, from its discovery to the most recent data regarding its cellular roles and interaction partners. We discuss the involvement of the MUTYH protein in the A:8-oxo-G BER pathway acting together with pol λ, the pol that can faithfully incorporate C opposite 8-oxo-G and thus bypass this lesion in a correct manner. We also outline the current knowledge about the regulation of MUTYH itself and the A:8-oxo-G repair pathway by posttranslational modifications (PTM). Finally, to achieve a clearer overview of the literature, we will briefly touch on the rather confusing MUTYH nomenclature. In short, MUTYH is a unique DNA glycosylase that catalyzes the excision of an undamaged base from DNA.

CHEK2 1100DELC germline mutation: a frequency study in hereditary breast and colon cancer Brazilian families

CHEK2 encodes a cell cycle checkpoint kinase that plays an important role in the DNA damage repair pathway, activated mainly by ATM (Ataxia Telangiectasia Mutated) in response to double-stranded DNA breaks. A germline mutation in CHEK2, 1100delC, has been described as a low penetrance allele in a significant number of families with breast and colorectal cancer in certain countries and is also associated with increased risk of contralateral breast cancer in women previously affected by the disease. About 5%-10% of all breast and colorectal cancers are associated with hereditary predisposition and its recognition is of great importance for genetic counseling and cancer risk management. Here, we have assessed the frequency of the CHEK2 1100delC mutation in the germline of 59 unrelated Brazilian individuals with clinical criteria for the hereditary breast and colorectal cancer syndrome. A long-range PCR strategy followed by gene sequencing was used. The 1100delC mutation was encountered in the germline of one (1.7%) individual in this high risk cohort. This indicates that the CHEK2 1100delC is not commonly encountered in Brazilian families with multiple diagnoses of breast and colorectal cancer. These results should be confirmed in a larger series of families and further testing should be undertaken to investigate the molecular mechanisms underlying the hereditary breast and colorectal cancer phenotype.

Mutation mismatch repair gene deletions in diffuse large B-cell lymphoma

To further unravel the molecular pathogenesis of diffuse large B-cell lymphoma (DLBCL), we performed high-resolution comparative genomic hybridization on lymph node biopsies from 70 patients. With this strategy, we identified microdeletions of genes involved in the mutation mismatch repair (MMR) pathway in two samples. The first patient presented with a homozygous deletion of MSH2–MSH6 due to duplication of an unbalanced pericentric inversion of chromosome 2. The other case showed a PMS2 heterozygous deletion. PMS2 and MSH2–MSH6 abnormalities, respectively, resulted in a decrease and complete loss of gene expression. However, unlike tumors associated with the hereditary non-polyposis colorectal cancer syndrome or immunodeficiency-related lymphomas, no microsatellite instability was detected. Mutational profiles revealed especially in one patient an aberrant hypermutation without a clear activation-induced cytidine deaminase signature, indicating a breakdown of the high-fidelity repair in favor of the error-prone repair pathway. Our findings suggest that in a rare subset of patients, inactivation of the genes of the MMR pathway is likely an important step in the molecular pathogenesis of DLBCL and does not involve the same molecular mechanisms as other common neoplasms with MMR deficiency.

General aspects of colorectal cancer.

Colorectal cancer (CRC) is one of the main causes of death. Cancer is initiated by several DNA damages, affecting proto-oncogenes, tumour suppressor genes, and DNA repairing genes. The molecular origins of CRC are chromosome instability (CIN), microsatellite instability (MSI), and CpG island methylator phenotype (CIMP). A brief description of types of CRC cancer is presented, including sporadic CRC, hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndromes, familiar adenomatous polyposis (FAP), MYH-associated polyposis (MAP), Peutz-Jeghers syndrome (PJS), and juvenile polyposis syndrome (JPS). Some signalling systems for CRC are also described, including Wnt-β-catenin pathway, tyrosine kinase receptors pathway, TGF-β pathway, and Hedgehog pathway. Finally, this paper describes also some CRC treatments.