Candidate predisposing germline copy number variants in early onset colorectal cancer patients

Purpose. A great proportion of the heritability of colorectal cancer (CRC) still remains unexplained, and rare variants, as well as copy number changes, have been proposed as potential candidates to explain the so-called ‘missing heritability’. We aimed to identify rare high-to-moderately penetrant copy number variants (CNVs) in patients suspected of having hereditary CRC due to an early onset. Methods/patients. We have selected for genome-wide copy number analysis, 27 MMR-proficient early onset CRC patients (<50 years) without identifiable germline mutations in Mendelian genes related to this phenotype. Rare CNVs were selected by removing all CNVs detected at MAF >1% in the in-house control CNV database (n = 629 healthy controls). Copy number assignment was checked by duplex real-time quantitative PCR or multiplex ligation probe amplification. Somatic mutation analysis in candidate genes included: loss of heterozygosity studies, point mutation screening, and methylation status of the promoter. Results. We have identified two rare germline deletions involving the AK3 and SLIT2 genes in two patients. The search for a second somatic mutational event in the corresponding CRC tumors showed loss of heterozygosity in AK3, and promoter hypermethylation in SLIT2. Both genes have been previously related to colorectal carcinogenesis. Conclusions. These findings suggest that AK3 and SLIT2 may be potential candidates involved in genetic susceptibility to CRC (AU)

No disponible

Candidate predisposing germline copy number variants in early onset colorectal cancer patients.

PURPOSE: A great proportion of the heritability of colorectal cancer (CRC) still remains unexplained, and rare variants, as well as copy number changes, have been proposed as potential candidates to explain the so-called 'missing heritability'. We aimed to identify rare high-to-moderately penetrant copy number variants (CNVs) in patients suspected of having hereditary CRC due to an early onset. METHODS/PATIENTS: We have selected for genome-wide copy number analysis, 27 MMR-proficient early onset CRC patients (<50 years) without identifiable germline mutations in Mendelian genes related to this phenotype. Rare CNVs were selected by removing all CNVs detected at MAF >1% in the in-house control CNV database (n = 629 healthy controls). Copy number assignment was checked by duplex real-time quantitative PCR or multiplex ligation probe amplification. Somatic mutation analysis in candidate genes included: loss of heterozygosity studies, point mutation screening, and methylation status of the promoter. RESULTS: We have identified two rare germline deletions involving the AK3 and SLIT2 genes in two patients. The search for a second somatic mutational event in the corresponding CRC tumors showed loss of heterozygosity in AK3, and promoter hypermethylation in SLIT2. Both genes have been previously related to colorectal carcinogenesis. CONCLUSIONS: These findings suggest that AK3 and SLIT2 may be potential candidates involved in genetic susceptibility to CRC.

High incidence of large deletions in the PMS2 gene in Spanish Lynch syndrome families.

Lynch syndrome (LS) is caused by germline mutations in one of the four mismatch repair (MMR) genes. Defects in this pathway lead to microsatellite instability (MSI) in DNA tumors, which constitutes the molecular hallmark of this disease. Selection of patients for genetic testing in LS is usually based on fulfillment of diagnostic clinical criteria (i.e. Amsterdam criteria or the revised Bethesda guidelines). However, following these criteria PMS2 mutations have probably been underestimated as their penetrances appear to be lower than those of the other MMR genes. The use of universal MMR study-based strategies, using MSI testing and immunohistochemical (IHC) staining, is being one proposed alternative. Besides, germline mutation detection in PMS2 is complicated by the presence of highly homologous pseudogenes. Nevertheless, specific amplification of PMS2 by long-range polymerase chain reaction (PCR) and the improvement of the analysis of large deletions/duplications by multiplex ligation-dependent probe amplification (MLPA) overcome this difficulty. By using both approaches, we analyzed 19 PMS2-suspected carriers who have been selected by clinical or universal strategies and found five large deletions and one frameshift mutation in PMS2 in six patients (31%). Owing to the high incidence of large deletions found in our cohort, we recommend MLPA analysis as the first-line method for searching germline mutations in PMS2.

A genome-wide association study on copy-number variation identifies a 11q11 loss as a candidate susceptibility variant for colorectal cancer.

Colorectal cancer (CRC) is a complex disease, and therefore its development is determined by the combination of both environmental factors and genetic variants. Although genome-wide association studies (GWAS) of SNP variation have conveniently identified 20 genetic variants so far, a significant proportion of the observed heritability is yet to be explained. Common copy-number variants (CNVs) are one of the most important genomic sources of variability, and hence a potential source to explain part of this missing genetic fraction. Therefore, we have performed a GWAS on CNVs to explore the relationship between common structural variation and CRC development. Phase 1 of the GWAS consisted of 881 cases and 667 controls from a Spanish cohort. Copy-number status was validated by quantitative PCR for each of those common CNVs potentially associated with CRC in phase I. Subsequently, SNPs were chosen as proxies for the validated CNVs for phase II replication (1,342 Spanish cases and 1,874 Spanish controls). Four common CNVs were found to be associated with CRC and were further replicated in Phase II. Finally, we found that SNP rs1944682, tagging a 11q11 CNV, was nominally associated with CRC susceptibility (p value = 0.039; OR = 1.122). This locus has been previously related to extreme obesity phenotypes, which could suggest a relationship between body weight and CRC susceptibility.

Pharmacogenomics in colorectal cancer: a genome-wide association study to predict toxicity after 5-fluorouracil or FOLFOX administration.

The development of genotyping technologies has allowed for wider screening for inherited causes of variable outcomes following drug administration. We have performed a genome-wide association study (GWAS) on 221 colorectal cancer (CRC) patients that had been treated with 5-fluorouracil (5-FU), either alone or in combination with oxaliplatin (FOLFOX). A validation set of 791 patients was also studied. Seven SNPs (rs16857540, rs2465403, rs10876844, rs10784749, rs17626122, rs7325568 and rs4243761) showed evidence of association (pooled P-values 0.020, 9.426E-03, 0.010, 0.017, 0.042, 2.302E-04, 2.803E-03) with adverse drug reactions (ADRs). This is the first study to explore the genetic basis of inter-individual variation in toxicity responses to the administration of 5-FU or FOLFOX in CRC patients on a genome-wide scale.

A two-phase case-control study for colorectal cancer genetic susceptibility: candidate genes from chromosomal regions 9q22 and 3q22.

BACKGROUND: Colorectal cancer (CRC) is the second cause of cancer-related death in the Western world. Much of the CRC genetic risk remains unidentified and may be attributable to a large number of common, low-penetrance genetic variants. Genetic linkage studies in CRC families have reported additional association with regions 9q22-31, 3q21-24, 7q31, 11q, 14q and 22q. There are several plausible candidate genes for CRC susceptibility within the aforementioned linkage regions including PTCH1, XPA and TGFBR1 in 9q22-31, and EPHB1 and MRAS in 3q21-q24. METHODS: CRC cases and matched controls were from EPICOLON, a prospective, multicentre, nationwide Spanish initiative, composed of two independent phases. Phase 1 corresponded to 515 CRC cases and 515 controls, whereas phase 2 consisted of 901 CRC cases and 909 controls. Genotyping was performed for 172 single-nucleotide polymorphisms (SNPs) in 84 genes located within regions 9q22-31 and 3q21-q24. RESULTS: None of the 172 SNPs analysed in our study could be formally associated with CRC risk. However, rs1444601 (TOPBP1) and rs13088006 (CDV3) in region 3q22 showed interesting results and may have an effect on CRC risk. CONCLUSIONS: TOPBP1 and CDV3 genetic variants on region 3q22 may modulate CRC risk. Further validation and meta-analysis should be undertaken in larger CRC cohorts.

COGENT (COlorectal cancer GENeTics): an international consortium to study the role of polymorphic variation on the risk of colorectal cancer.

It is now recognised that a part of the inherited risk of colorectal cancer (CRC) can be explained by the co-inheritance of low-penetrance genetic variants. The accumulated experience to date in identifying these variants has served to highlight difficulties in conducting statistically and methodologically rigorous studies and follow-up analyses. The COGENT (COlorectal cancer GENeTics) consortium includes 20 research groups in Europe, Australia, the Americas, China and Japan. The overarching goal of COGENT is to identify and characterise low-penetrance susceptibility variants for CRC through association-based analyses. In this study, we review the rationale for identifying low-penetrance variants for CRC and our proposed strategy for establishing COGENT.

Breast tumor resembling the tall cell variant of papillary thyroid carcinoma: a case report.

The breast tumor resembling the tall cell variant of papillary thyroid carcinoma is a very unusual mammary carcinoma whose histologic and predominant nuclear features mimic a papillary thyroid carcinoma. We report the case of a 64-year-old woman who presented with a palpable nodule in the right breast. Fine needle aspiration disclosed abundant cellularity with isolated cells, sheets, and papillary formations of epithelial cells with nuclear grooves. Histologically, the neoplastic cells were arranged in a solid to papillary architecture, with follicular-like and cribriform areas. The cells were columnar to cuboidal with eosinophilic cytoplasm, clear chromatin, nuclear grooves, and occasional nuclear pseudoinclusions. Tumor cells were positive for cytokeratins, alpha and beta-estrogen receptors, progesterone receptor, androgen receptor, CEA, and bcl-2. We searched for BRAF mutations with negative results. Recognizing the cytologic and histologic characteristics of these peculiar mammary tumors that mimic thyroid carcinomas can avoid unnecessary clinical investigations.

Duplication and deletion analysis by fluorescent real-time PCR-based genotyping.

BACKGROUND: Gene dosage determination is an increasingly important field for the study of genome variation and organization. In parallel, the advances in our understanding of the genetic basis of disease have produced an exponential increase in the demand for molecular diagnostic analyses. Although efforts have been spent on increasing both the accuracy and the throughput of the gene dosage analysis, the success has been limited. METHODS: A large number of suitable methods has been proposed; most are based on quantitative real-time PCR or amplification of multiple targets. A new approach exploits the differences between fluorescent signals of SNP alleles in heterozygous samples to assess duplications. The SNP typing-dependent fluorescent signal allelic asymmetry is an intrinsic characteristic of a SNP typing assay and can lead to a simple and cost-effective gene dosage method. This strategy provides sufficient throughput and sensitivity for duplication analysis. CONCLUSIONS: There are advantages and disadvantages of real-time methodology when applying the approach to the molecular diagnostic field.

[Smith-Magenis syndrome: a report of two new cases and an approximation to their characteristic behavioural phenotype]. / Síndrome de Smith-Magenis: aportación de dos nuevos casos y aproximación a su característico fenotipo conductual.

INTRODUCTION: Smith-Magenis syndrome (SMS) is a well defined contiguous gene syndrome that is caused by an interstitial deletion in the 17p11.2 region. It is characterised by the presentation of characteristic facial features, brachydactylia, short stature, varying degrees of mental retardation, occasional neuropathy and a specific behavioural phenotype that points to this entity. AIMS: Our aim was to report the cases of two children with SMS and carry out an approximation towards their characteristic behavioural phenotype. CASE REPORTS: We studied the cases of two 12-year-old children who were suspected of suffering from SMS following the findings of a physical exploration and the presence of a specific behavioural phenotype. This was confirmed by the genetic-molecular study which proved the existence of the 17p11.2 deletion. CONCLUSIONS: Although SMS is a relatively infrequent syndrome, a patient with mental retardation and characteristic dysmorphic features who presents an especially relevant behavioural disorder including different stereotypic movements, aggression phenomena and sleep disorders is suggestive of this diagnostic possibility.

Síndrome de Smith-Magenis: aportación de dos nuevos casos y aproximación a su característico fenotipo conductual / Smith-magenis syndrome: a report of two new cases and an approximation to their characteristic behavioural phenotype

Introducción. El síndrome de Smith-Magenis (SSM) es un síndrome de genes contiguos bien definido, causado por una deleción intersticial en la región 17p11.2, caracterizado por presentar rasgos faciales característicos, braquidactilia, talla baja, un grado variable de retraso mental, neuropatía ocasional y un fenotipo conductual específico sugerente de esta entidad. Objetivo. Presentar dos niños con SSM y realizar una aproximación a su característico fenotipo conductual. Casos clínicos. Dos niños de 12 años de edad, en los que los hallazgos en la exploración física y la presencia de un fenotipo conductual específico sugirieron la posibilidad de un SSM, hecho que se confirmó mediante la demostración de la deleción 17p11.2 en el estudio genético molecular. Conclusiones. Aunque el SSM es un síndrome relativamente infrecuente, la presencia en un paciente con retraso mental y rasgos dismórficos característicos de un trastorno conductual especialmente relevante, que incluye distintas estereotipias, fenómenos de agresividad y trastornos del sueño, sugiere esta posibilidad diagnóstica (AU)

Introduction. Smith-Magenis syndrome (SMS) is a well defined contiguous gene syndrome that is caused by an interstitial deletion in the 17p11.2 region. It is characterised by the presentation of characteristic facial features, brachydactylia, short stature, varying degrees of mental retardation, occasional neuropathy and a specific behavioural phenotype that points to this entity. Aims. Our aim was to report the cases of two children with SMS and carry out an approximation towards their characteristic behavioural phenotype. Case reports. We studied the cases of two 12-year-old children who were suspected of suffering from SMS following the findings of a physical exploration and the presence of a specific behavioural phenotype. This was confirmed by the genetic-molecular study which proved the existence of the 17p11.2 deletion. Conclusions. Although SMS is a relatively infrequent syndrome, a patient with mental retardation and characteristic dysmorphic features who presents an especially relevant behavioural disorder including different stereotypic movements, aggression phenomena and sleep disorders is suggestive of this diagnostic possibility (AU)

Analysis of BRCA1 and BRCA2 in breast and breast/ovarian cancer families shows population substructure in the Iberian peninsula.

An estimated 5-10% of all breast and ovarian cancers are due to an inherited predisposition, representing a rather large number of patients. In Spain 1/13-1/14 women will be diagnosed with breast cancer during their lifetime. Two major breast cancer genes, BRCA1 and BRCA2, have been identified. To date, several hundred pathogenic mutations in these two genes have been published or reported to the Breast Cancer Information Core, BIC database (http://www.nhgri.nih.gov/Intramural_research_Lab transfer/Bic/index.html). In the present study, 30 Spanish breast and breast/ovarian cancer families (29 from Galicia, NW Spain, and 1 from Catalonia, NE Spain) were screened for mutations in the BRCA1 and BRCA2 genes. The analysis of these genes was carried out by SSCP for shorter exons and direct sequencing in the case of longer ones. Mutations were found in 8 of the 30 families studied (26.66%). It is important to note that all mutations were detected within the BRCA1 gene: 330 A>G, 910_913delGTTC, 2121 C>T, 3958_3962delCTCAGinsAGGC, and 5530 T>A. The BRCA1 330 A>G mutation was found in four unrelated families and accounted for 50% of all identified mutations.

Rare HRAS1 alleles are a risk factor for the development of brain tumors.

BACKGROUND: The highly polymorphic HRAS1 minisatellite locus, located 1 kilobase downstream from the H-ras1 gene, has been associated with increased susceptibility to a variety of cancers. Microsatellite instability (MI), another molecular abnormality observed in human neoplasms, most likely reflects an increased mutation rate and also is thought to underlie cancer predisposition. The purpose of this study was to investigate the association between rare HRAS1 alleles and brain tumors and to correlate the HRAS1 allelotype with MI and clinicopathologic features. METHODS: Ninety-four patients with primary brain tumors (52 gliomas, 32 meningiomas, and 10 schwannomas) and 109 healthy control individuals were studied. The size of HRAS1 alleles was determined by fluorescent detection in an automated DNA sequencer. The interspersion pattern was assessed by the minisatellite variant repeat-polymerase chain reaction technique. RESULTS: Twenty of 94 (21.28%) patients with brain tumors had at least one rare allele, compared with 13 of 109 (11.92%) in the control population (Fisher exact test; P = 0.0329). The presence of rare alleles was associated with an increased risk of brain tumors (odds ratio, 1.99; 95% confidence interval, 0.93-4.27). The overrepresentation of rare alleles in tumor patients mainly reflects the higher frequency observed in the glioma group (P = 0.0086). The authors did not detect association between the presence of rare HRAS1 alleles and MI in their series. No significant difference in the distribution of these alleles was found when tumors were compared according to other clinicopathologic variables. CONCLUSIONS: The presence of rare HRAS1 alleles is associated with an increased risk for the development of glial neoplasms (OR = 2.72; 95% CI, 1.17-6.32). The lack of association between rare HRAS1 polymorphisms and MI suggests that these two genetic factors are not likely to be expression of the same underlying defect.

Mutation analysis of the adenomatous polyposis coli (APC) gene in northwest Spanish patients with familial adenomatous polyposis (FAP) and sporadic colorectal cancer.

Germline mutations in the tumor-suppresor APC gene are associated with hereditary familial adenomatous polyposis (FAP) and somatic mutations are common in sporadic colorectal cancer. In this study, we report the identification of three novel germline mutations: 1682-1683insA, 3252-3253insAT, 3544A>T and a new somatic mutation 4130-4131delTT, all giving rise to truncated APC proteins. The majority of the mutations we found originate a truncated APC protein and cause the FAP phenotype. However, special attention must be given to the missense mutations Asp1822Val and Ser2621Cys since their segregation with the FAP phenotype is questionable. In our FAP families we did not find any genetical alterations at codon 1309, being this mutation the most frequent reported in APC. Differences in the recurrence of pathological mutations in APC could exist among populations. However, epidemiological studies must be performed to confirm this hypothesis.