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M Genuardi

Publications and source records attributed to M Genuardi.

At least 19 recordsLinked to original sources
PubMed2006

A genetic model for determining MSH2 and MLH1 carrier probabilities based on family history and tumor microsatellite instability.

Mutation-predicting models can be useful when deciding on the genetic testing of individuals at risk and in determining the cost effectiveness of screening strategies at the population level. The aim of this study was to evaluate the performance of a newly developed genetic model that incorporates tumor microsatellite instability (MSI) information, called the AIFEG model, and in predicting the presence of mutations in MSH2 and MLH1 in probands with suspected hereditary non-polyposis colorectal cancer. The AIFEG model is based on published estimates of mutation frequencies and cancer penetrances in carriers and non-carriers and employs the program MLINK of the FASTLINK package to calculate the proband's carrier probability. Model performance is evaluated in a series of 219 families screened for mutations in both MSH2 and MLH1, in which 68 disease-causing mutations were identified. Predictions are first obtained using family history only and then converted into posterior probabilities using information on MSI. This improves predictions substantially. Using a probability threshold of 10% for mutation analysis, the AIFEG model applied to our series has 100% sensitivity and 71% specificity.

Adaptor Proteins, Signal Transducing↗
PubMed2006

SDH mutations in patients affected by paraganglioma syndromes: a personal experience.

Mutations in genes encoding mitochondrial succinate dehydrogenase (SDH) are frequently involved in the development of neural crest-derived (NCD) tumors, such as pheochromocytomas (PHEOs) or paragangliomas (PGLs). In this study we report the results of sequencing analysis in leukocyte DNA of patients affected by PHEO/PGL who turned out to be SDH mutation carriers. A nonsense germline heterozygous mutation (Q109X) was found in the exon 4 of the SDHD gene in the index cases of six unrelated families affected by PHEO/PGL. Haplotype analysis showed the presence of a founder effect. Affected patients showed high clinical variability, ranging from monolateral to bilateral glomus tumors, variably associated or not with PGLs or PHEOs. A novel missense SDHD variant, T112I, was also found in one of our families. A new missense G106D mutation, involving a highly conserved amino acid, was found in two sisters affected by bilateral glomus tumors. A P81L mutation associated with abdominal and head and neck PGL was detected in three families. A G12S variant of the SDHD gene was found in one patient affected by a PHEO. The finding of this variant in 3 of 100 control subjects suggests that it is a polymorphism and not a mutation. A novel IVS2-1G>T variant was found at intron 2 of SDHD gene in one patient affected by a glomus tumor. All the tumors associated with SDHD mutations were benign. Conversely, the only mutation we found in SDHB gene (IVS3+1G>A) was associated with a malignant PHEO.

Amino Acid Sequence↗
PubMed2005

A novel microdeletion syndrome with loss of the MSH2 locus and hereditary non-polyposis colorectal cancer.

Constitutional chromosome deletions can predispose to the development of cancer with the phenotypic characteristics of inherited cancer syndromes, when the deleted region encompasses a tumour suppressor gene. Examples of such conditions are represented by the cytogenetic deletions associated with retinoblastoma, Wilms tumour and familial adenomatous polyposis. So far, no constitutional deletions involving the genes implicated in hereditary non-polyposis colorectal cancer (HNPCC) have been identified. This may be at least partially because of the lack of distinctive phenotypic manifestations in HNPCC. We describe the first case of a constitutional microdeletion associated with HNPCC. Suspicion of a microdeletion was prompted by the association of mental retardation, postnatal growth deficiency, minor congenital anomalies and early onset (37 years) sporadic colon cancer. The patient was found to harbour a microdeletion within chromosome 2p16-p21, including the MSH2 gene. Since there are very few reports of deletions of the 2p16-p21 region, our observation sets the grounds for the definition of a novel multiple congenital anomaly/mental retardation/cancer microdeletion syndrome.

Abnormalities, Multiple↗
PubMed2005

Phenotype variability of neural crest derived tumours in six Italian families segregating the same founder SDHD mutation Q109X.

BACKGROUND: Mutations in genes coding for the mitochondrial complex II succinate dehydrogenase (SDH) subunits cause familial neural crest derived (NCD) tumours. METHODS: Index cases from six apparently unrelated families affected by NCD tumours were analysed for mutations in the SDHB, SDHC, and SDHD genes. RESULTS: The same nonsense germline heterozygous mutation (Q109X) in exon 4 of the SDHD gene was found in each of the six families. Overall, 43 heterozygotes were identified. These were evaluated for the presence of NCD tumours through radiological examination of the neck, thorax, and abdomen, and measurement of urinary metanephrines and plasma chromogranin A. A novel missense SDHD variant, T112I, which did not segregate with the Q109X mutation and was not associated with phenotypic manifestations, was observed in one of the families. Microsatellite analysis showed a common haplotype in all individuals heterozygous for the Q109X mutation, indicating a founder effect. Overall, 18 heterozygotes were clinically affected by at least one NCD tumour. Every affected patient inherited the germline mutation from the father, confirming SDHD maternal genomic imprinting. Penetrance of the paternally inherited mutation progressively increased from 33% to 83% at 30 and 60 years, respectively. Affected patients showed high clinical variability, ranging from monolateral to bilateral glomus tumours variably associated or not with paragangliomas or phaeochromocytomas. Loss of heterozygosity was observed in tumour cells isolated by laser capture microdissection. CONCLUSIONS: This study shows that a single founder SDHD mutation is present in an area of central Italy and that this mutation is associated with widely variable interfamilial and intrafamilial expressivity.

Adult↗
PubMed2004

Genetic testing among high-risk individuals in families with hereditary nonpolyposis colorectal cancer.

Hereditary nonpolyposis colorectal cancer (HNPCC) is frequently associated with constitutional mutations in a class of genes involved in DNA mismatch repair. We identified 32 kindreds, with germline mutations in one of three genes hMSH2, hMLH1 or hMSH6. In this study, we purposed to evaluate how many high-risk individuals in each family underwent genetic testing: moreover, we assessed how many mutation-positive unaffected individuals accepted colonoscopic surveillance and the main findings of the recommended follow-up. Families were identified through a population-based registry, or referred from other centres. Members of the families were invited for an education session with two members of the staff. When a kindred was consistent with HNPCC, neoplastic tissues were examined for microsatellite instability (MSI) and immunohistochemical expression of MSH2, MLH1 and MSH6 proteins. Moreover, constitutional mutations were searched by SSCP or direct sequencing of the whole genomic region. Of the 164 subjects assessed by genetic testing, 89 were gene carriers (66 affected - that is, with HNPCC-related cancer diagnosis - and 23 unaffected) and 75 tested negative. Among the 23 unaffected gene carriers, 18 (78.3%) underwent colonoscopy and four declined. On a total of 292 first degree at risk of cancer, 194 (66.4%) did not undergo genetic testing. The main reasons for this were: (a) difficulty to reach family members at risk, (b) lack of collaboration, (c) lack of interest in preventive medicine or 'fatalistic' attitude towards cancer occurrence. The number of colorectal lesions detected at endoscopy in gene carriers was significantly (P<0.01) higher than in controls (noncarriers). We conclude that a large fraction of high-risk individuals in mutation-positive HNPCC families does not undergo genetic testing, despite the benefits of molecular screening and endoscopic surveillance. This clearly indicates that there are still barriers to genetic testing in HNPCC, and that we are unable to provide adequate protection against cancer development in these families.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Nonhomologous Robertsonian translocations (NHRTs) and uniparental disomy (UPD) risk: an Italian multicentric prenatal survey.

OBJECTIVES: The risk of uniparental disomy (UPD) occurrence associated with the prenatal finding of balanced nonhomologous Robertsonian translocations (NHRTs) has been estimated only on limited empirical data. The aim of the study was to verify the estimate of the general risk, to get narrower confidence intervals by cumulating the data and to obtain risk estimates for specific translocation types. METHODS: We tested for UPD 160 prenatal specimens referred to the participant centers after the cytogenetic finding of NHRT. RESULTS: One case of upd(14)mat was found, associated with a 45,XX,der(14;22)mat fetal karyotype. The general empirical risk of UPD occurrence in NHRT carrier fetuses, corrected for the actual number of chromosomes analyzed, was 0.76% (95% CI 0.02-4.25%). Cumulative data with previous studies gives a general risk of UPD associated with NHRT of 0.80% (95% CI 0.17-2.34%). The UPD risk for the specific NHRT der(13;14) did not significantly differ from that of the other NHRTs taken together. CONCLUSION: The present survey confirms the previously estimated risk of occurrence of UPD in offspring of NHRT carriers as a low, but not negligible risk, worth being investigated in prenatal diagnosis.

Amniocentesis↗
PubMed2004

Aetiology of colorectal cancer and relevance of monogenic inheritance.

BACKGROUND AND AIMS: Although diet and lifestyle are associated with the development of colorectal malignancies, the only clearly identified aetiological factors in colorectal cancer are inheritance (hereditary non-polyposis colorectal cancer (HNPCC) and familial polyposis), inflammatory bowel diseases, papillomavirus, and acquired immunodeficiency syndrome (AIDS). Our aim was to determine what proportion of colorectal neoplasms could be attributed to these specific factors. PATIENTS AND METHODS: Data from a colorectal cancer registry were analysed over a 15 year period, during which nearly 2500 cases were recorded. In patients with suspected HNPCC, microsatellite instability and immunohistochemical expression of proteins encoded by the main DNA mismatch repair genes were assessed. In families with unstable neoplasms, constitutional mutations of the mismatch repair genes hMSH2, hMLH1, and hMSH6 were evaluated by single strand conformation polymorphism analysis and sequencing. RESULTS: Inflammatory bowel diseases, familial polyposis, and AIDS were rare causes of colorectal cancer (three, three, and one case, respectively). Anal squamous carcinoma developed in 27 patients (1.0%) and could be attributed to papillomavirus infection. In 58 patients (from 34 families) a clinical diagnosis of HNPCC was established (2.4%). In total, cases with a known aetiology were 92 (3.7% of all patients). Microsatellite instability was detected in 15 cancers from HNPCC families, and germline mutations in six families (12 patients, 0.5% of the total). Families with unstable tumours, with or without mutations, were clinically similar, suggesting the involvement of the mismatch repair system even when mutations were not detected. CONCLUSIONS: The study suggests that the aetiology of colorectal malignancies remains elusive in the large majority of cases. Among specific causes, HNPCC represents the most frequent. However, with a population based approach, constitutional mutations of the main genes involved in HNPCC can be detected in only 20% of cases.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Two novel mutations and a new STK11/LKB1 gene isoform in Peutz-Jeghers patients.

Peutz-Jeghers syndrome (PJS) is a rare autosomal dominantly inherited disorder with variable expression and incomplete penetrance characterized by mucocutaneous pigmentation, predisposition to hamartomatous intestinal polyposis, and various other neoplasms. It occurs in approximately 1 in 8,300 to 29,000 live births. In nearly 50% of patients PJS is caused by germ line mutations in the STK11/LKB1 serine/threonine kinase gene, the only kinase gene currently known to act as a tumor suppressor. We have performed a mutation search in the STK11/LKB1 gene in 8 sporadic cases and 3 PJS families using a combination of different screening techniques. We have identified four mutations, two of which I177N and the IVS2+1A->G, were previously unreported. We have also evaluated the presence of cDNA alterations by means of RT-PCR analysis and direct cDNA sequencing and have found two aberrant transcripts in a single PJS case despite the lack of any apparent genomic alteration. Finally, we report the presence of a novel STK11/LKB1 cDNA isoform observed in all the normal subjects studied as well as in the majority of the PJS patients.

AMP-Activated Protein Kinase Kinases↗
PubMed2001

Molecular screening for hereditary nonpolyposis colorectal cancer: a prospective, population-based study.

PURPOSE: Germline mutations in mismatch repair genes predispose to hereditary nonpolyposis colorectal cancer (HNPCC). To address effective screening programs, the true incidence of the disease must be known. Previous clinical investigations reported estimates ranging between 0.5% and 13% of all the colorectal cancer (CRC) cases, whereas biomolecular studies in Finland found an incidence of 2% to 2.7% of mutation carriers for the disease. The aim of the present report is to establish the frequency of the disease in a high-incidence area for colon cancer. PATIENTS AND METHODS: Through the data of the local CRC registry, we prospectively collected all cases of CRC from January 1, 1996, through December 31, 1997 (N = 391). Three hundred thirty-six CRC cases (85.9% of the incident cases) were screened for microsatellite instability (MSI) with six to 12 mono- and dinucleotide markers. MSI cases were subjected to MSH2 and MLH1 germline mutation analysis and immunohistochemistry; the methylation of the promoter region was studied for MLH1. RESULTS: Twenty-eight cases (8.3% of the total) showed MSI. MSI cases differed significantly from microsatellite-stable (MSS) cases for their proximal location (P <.01), high mucinous component (P <.01), and poor differentiation (P =.002). Of MSI cases studied (n = 12), only one with a family history compatible with HNPCC had a germline mutation (in MSH2). Five other patients with a family history of HNPCC (two with MSI and three with MSS tumors) did not show germline mutations. CONCLUSION: We conclude that the incidence of molecularly confirmed HNPCC (one [0.3%] of 336) in a high-incidence area for CRC is lower than in previous biomolecular and clinical estimates.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Clinical and biologic heterogeneity of hereditary nonpolyposis colorectal cancer.

MMR gene mutations and MSI are not found in all clinically diagnosed HNPCC families. We evaluated whether MMR genotyping and tumor MSI analysis could identify distinct clinical subgroups among HNPCC families. Twenty-nine clinical HNPCC families were divided into 3 groups: A, families with hMLH1 or hMSH2 gene mutations; B, MMR gene mutations not present but MSI present in at least 50% of tumors tested; C, mutational and MSI analyses negative. We evaluated tumor spectrum, age at onset, risk of cancer in the follow-up and survival for CRC in the 3 groups. Tumors of the target organs in HNPCC (colon and rectum, endometrium, ovary, small bowel, stomach, renal pelvis and ureter) were more frequent in the first 2 groups than in the latter. Colon cancer was more frequently located in the proximal colon and showed an earlier age at onset in families with MMR gene mutation or with MSI than in families with stable tumors. Comparing the occurrence of tumors in the follow-up, in the first 2 groups patients younger than 50 years had a higher RR, which was particularly marked for CRC (RR = 18.6 for group A vs. group C, RR = 16.7 for group B vs. group C). CRC patients in the first 2 groups had a better clinical prognosis. The results of molecular analysis could distinguish, within clinically defined HNPCC families, different subgroups to which specific programs of surveillance could be addressed.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Microsatellite instability is an independent indicator of recurrence in sporadic stage I-II endometrial adenocarcinoma.

PURPOSE: The aim of this study was to define the prognostic role of microsatellite status in 65 stage I-II primary sporadic endometrioid endometrial adenocarcinoma (EEA) patients. PATIENTS AND METHODS: Familiarity for neoplasia was ascertained in all patients on the basis of a questionnaire. Microsatellite status was assessed by matching normal and tumoral DNA probed for five dinucleotide repeats and one mononucleotide repeat marker. Microsatellite status was analyzed in relation to clinicopathologic characteristics of the patients and length of disease-free survival (DFS). RESULTS: Eleven tumors (17%) of 65 had instability at two or more loci and were considered as unstable or microsatellite instability (MI). Tumors with no instability or instability at one locus were classified as microsatellite stable (MS). The percentage of MI was significantly higher in poorly than in well to moderately differentiated tumors (50% v 9%; P =.003). The 5-year DFS rate of MI patients was 63% (95% confidence interval [CI], 35% to 91%) versus 96% (95% CI, 91% to 101%) of MS patients (P =.0004). In multivariate analysis, only the presence of MI, stage II of disease, and depth of myometrial invasion greater than 50% retained independent prognostic roles. CONCLUSION: The assessment of microsatellite status may provide useful information for preoperative prognostic characterization of stage I-II primary sporadic EEA patients in which more individualized treatment options can be attempted.

Adaptor Proteins, Signal Transducing↗
PubMed2001

CDKN2A germline splicing mutation affecting both p16(ink4) and p14(arf) RNA processing in a melanoma/neurofibroma kindred.

The CDKN2A locus encodes two tumor suppressor proteins, p16(ink4) and p14(arf), through use of alternative first exons. CDKN2A mutations detected in melanoma families are usually missense or nonsense changes which mainly impair p16(ink4) function. Large genomic deletions spanning the entire locus have been observed in two pedigrees with melanomas and nervous tumors. We have detected a novel splice site mutation in a family with melanomas, neurofibromas, and multiple dysplastic nevi. Both alternative mRNAs produced by the mutant allele lacked shared sequences from exon 2, which encodes a substantial portion (>50%) of both p16(ink4) and p14(arf) proteins. The development of neurofibromas can be explained by cooperative effects of combined inactivation of p16(ink4) and p14(arf) or, alternatively, of p14(arf) alone.

Adolescent↗
PubMed2001

Four novel MSH2 and MLH1 frameshift mutations and occurrence of a breast cancer phenocopy in hereditary nonpolyposis colorectal cancer.

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by mutations of genes encoding for proteins of the mismatch repair (MMR) machinery. The majority of mutations occur in the MLH1 and MSH2 genes, and consist of splice-site, frameshift and nonsense changes, leading to loss of protein function. In this study, we screened 7 HNPCC families for MLH1/MSH2 mutations. Sequence changes were identified in 5 families. Four alterations were novel 1- or 2-bp deletions or insertions causing a frameshift and appearance of premature stop codons (MLH1: c.597-598delGA, c.1520-1521insT; MSH2: c.1444delA, c.119delG). The four small insertions/ deletions were located within stretches of simple repeated sequences. By reviewing the HNPCC mutation database, we found that the majority of 1-2 bp frameshift mutations similarly affects simple repetitive stretches, pointing to DNA polymerase slippage during replication as the most likely source of such errors. We also evaluated microsatellite instability (MSI) in a breast carcinoma (BC) from an MLH1 mutation carrier. While a colon cancer from the same individual showed MSI, the BC specimen was MSI-negative, indicating that development of the latter tumor was unrelated to MMR impairment, despite presence of a constitutional MLH1 mutation. Hum Mutat 17:521, 2001.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Familial microsatellite-stable non-polyposis colorectal cancer: incidence and characteristics in a clinic-based population.

BACKGROUND: About 15%-20% of colorectal cancers (CRCs) are familial. While a fraction of these arise in the context of hereditary syndromes, the causes underlying the majority of familial CRCs are not yet understood. PATIENTS AND METHODS: Family history of cancer, clinical characteristics, and microsatellite instability (MSI) in a series of 100 consecutive CRC patients were evaluated. RESULTS: Eighteen patients had a positive family history of CRC in a first-degree relative. Of these, two had a clinical diagnosis of familial adenomatous polyposis (FAP), and three were diagnosed with hereditary non-polyposis colorectal cancer (HNPCC) following results of MSI analysis. A diagnosis of HNPCC was also established in a fourth patient with early onset CRC, who had a second-degree relative with CRC, and whose tumor was positive for MSI. The remaining 13 familial CRCs did not show MSI in tumor DNA. The mean age at tumor diagnosis in patients with familial microsatellite-stable (MSS) CRC was higher than in HNPCC and FAP patients and similar to that recorded in sporadic cases. The incidence of second primary malignancies was significantly higher in familial MSS CRC probands (n = 4) compared to patients who did not have a diagnosis of FAP or HNPCC and did not have first-degree relatives affected with CRC (n = 6, in a total of 81 probands with these characteristics). CONCLUSIONS: These results define the existence of a subset of familial CRCs characterized by relatively late age at onset, high incidence of second primary tumors, and absence of MSI in tumor DNA.

Adenomatous Polyposis Coli↗
PubMed2001

Mutations of the 'minor' mismatch repair gene MSH6 in typical and atypical hereditary nonpolyposis colorectal cancer.

Mutations of the mismatch repair (MMR) genes MLH1 and MSH2 are associated with hereditary nonpolyposis colorectal cancer (HNPCC), a highly penetrant autosomal dominant condition characterized by hypermutability of short tandemly repeated sequences in tumor DNA. Mutations of another MMR gene, MSH6, seem to be less common than MLH1 and MSH2 defects, and have been mostly observed in atypical HNPCC families, characterized by a weaker tumor family history, higher age at disease onset, and low degrees of microsatellite instability (MSI), predominantly involving mononucleotide runs. We have investigated the MSH6 gene sequence in the peripheral blood of 4 HNPCC and 20 atypical HNPCC probands. Two frameshift mutations within exon 4 were detected in 2 patients. One mutation was found in a proband from a typical HNPCC family, who had developed a colorectal cancer (CRC), a gastric cancer and a rectal adenoma. The CRC and the adenoma showed mild MSI limited to mononucleotide tracts, while the gastric carcinoma was microsatellite stable. The other mutation was detected in an atypical HNPCC proband, whose CRC showed widespread MSI involving both mono- and dinucleotide repeats. The phenotypic variability associated with MSH6 constitutional mutations represents a complicating factor for the optimization of strategies aimed at identifying candidates to MSH6 genetic testing.

Adult↗
PubMed2001

Multiple lipomas linked to an RB1 gene mutation in a large pedigree with low penetrance retinoblastoma.

Hereditary predisposition to lipomas is observed in familial multiple lipomatosis (OMIM 151900) and benign cervical lipomatosis (OMIM 151800) and can also be associated with mutations in the MEN1 and PTEN genes (OMIM 131100 and 153480, respectively). In addition, a recent report indicates that a few patients with hereditary retinoblastoma also have lipomas. Here we report on an extended family segregating a splice site mutation in the RB1 gene. Almost all adult carriers of this mutation had multiple lipomas while penetrance for retinoblastoma was incomplete. In an unrelated pedigree, which was reported previously, the identical mutation was only associated with low-penetrance retinoblastoma but not lipomas. Our data indicate that lipoma predisposition in hereditary retinoblastoma is not associated with specific RB1 gene mutations but is influenced by modifying factors linked to this gene.

Base Sequence↗
PubMed2001

Investigation of G2-phase chromosomal radiosensitivity in hereditary non-polyposis colorectal cancer cells.

PURPOSE: To investigate whether cells from hereditary nonpolyposis colorectal cancer (HNPCC) patients, a genetic condition characterized by constitutional mutations in DNA mismatch repair genes and associated with predisposition to colorectal carcinoma (CRC), could present a higher G2 chromosomal radiosensitivity. It is generally hypothesized that cancer predisposition in HNPCC is associated with the loss of the wild-type allele in somatic cells, resulting in defective DNA mismatch repair but, to date, no data on G2 radiosensitivity have been reported for HNPCC. MATERIALS AND METHODS: Lymphoblastoid cell lines derived from six HNPCC patients heterozygous for MLH1, one HNPCC patient carrying a mutant MSH2 allele and three healthy controls were treated with 50 cGy of X-rays and sampled at various harvesting times, monitoring cell-cycle progression by 5-bromo-2-deoxyuridine (BrdUrd) incorporation in order to analyse chromosomal damage in the homogeneous G2 population. RESULTS: There were no differences between lymphoblasts derived from patients in the frequency of G2 chromosomal aberrations induced by X-rays when compared with control cell lines. However, despite the absence of G2 radiosensitivity in HNPCC cells, lymphoblasts from patients heterozygous for MLH1 mutations showed a higher induction of chromatid exchanges. CONCLUSIONS: The observed possible incorrect rejoining of double-strand breaks in MLH1 heterozygotes would be an additional and important factor contributing to loss of heterozygosity in HNPCC patients.

Adaptor Proteins, Signal Transducing↗