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Biomedical subjects

A Viel

Publications and source records attributed to A Viel.

76 records · Page 5Linked to original sources
PubMedDate not supplied

Assessment of pathogenicity criteria for constitutional missense mutations of the hereditary nonpolyposis colorectal cancer genes MLH1 and MSH2.

To determine the role played by MLH1 and MSH2 missense variants in cancer susceptibility, we have investigated the following genetic and biological characteristics associated with six MLH1 and four MSH2 missense changes identified in Italian hereditary nonpolyposis colorectal cancer (HNPCC) families: co-segregation with disease phenotype and/or bonafide pathogenetic mutations; presence of the variant in healthy control subjects; evolutionary conservation of the involved aminoacid and type of aminoacid change; and presence/absence of microsatellite instability (MSI) in tumour DNA. Overall, nine variants did not fulfil > or = 2 pathogenicity criteria. MSI was investigated in tumour samples from carriers of nine different missense mutations. Only 3/9 variants were associated with MSI in tumour DNA. In addition, four variants were not present in affected pedigree members, and five variants were observed in the control population. Based upon these results, we conclude that most MLH1 and MSH2 missense changes are unlikely to act as major causative factors in colorectal cancer susceptibility and development.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

Microsatellite instability and MLH1 and MSH2 germline defects are related to clinicopathological features in sporadic colorectal cancer.

Clinical and pathological features were evaluated to predict tumor microsatellite instability (MSI) and germline mutations in MLH1 and MSH2 DNA mismatch repair genes in two patient groups with sporadic colorectal cancer (CRC): 38 young patients (age </=45 years) and 31 old patients (age >/=60 years). Nine (25.7%) young patients out of 35 and five (16%) old patients out of 31 exhibited MSI in their cancers. MSI+ cancers were related to proximal cancer and mucinous carcinoma independently of the age at cancer onset. Three (7.9%) out of 38 young patients had mutations in MLH1 and MSH2 genes that led to truncated protein products; they were all at age <35 years and showed MSI in their tumors, with mucinous histotype in two cases. In conclusion, histopathological and clinical features of CRC allow identification of cancers showing DNA microsatellite instability. MSI in CRC at very early onset (age <35 years) appears useful to predict germline MMR gene defects.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

Clinical and molecular diagnosis of hereditary non-polyposis colorectal cancer: problems and pitfalls in an extended pedigree.

Hereditary non-polyposis colorectal cancer (or Lynch syndrome) is an autosomal dominant disease in which early onset colorectal carcinomas aggregate in families together with tumours of other organs. The genetic basis of the syndrome has been clarified with the identification of mutations in several DNA mismatch repair genes (MSH2, MLH1, PMS1, PMS2 and MSH6). We describe the clinical features and molecular characterization of a large hereditary non-polyposis colorectal cancer family which has been followed for almost 10 years. The kindred showed a striking aggregation of colorectal tumours in 3 successive generations; most of these neoplasms developed before the age of 50 years and were localized in the proximal colon. Molecular tests (carried out in ten individuals) showed specific alterations at the MLH1 gene, consisting in the insertion of a T nucleotide between bases 2,269 and 2,270; the mutation caused frameshift of the open reading frame and synthesis of a polypeptide longer than normal. The only tumour that could be analysed was positive for microsatellite instability. Physicians should become more confident with hereditary tumours and their implications, which are not limited to a single individual but concern all family members at risk of cancer. This family approach is different, and requires more expertise than the traditional individual approach. Common problems encountered in Hereditary Non-polyposis Colorectal Cancer families include: A) poor collaboration of subjects at risk (a situation which may cause some conflict between the doctor's duty to inform patients about their risk of disease and the rights of patients to choose and decide about their health); B) definition of the most appropriate surveillance programme for a given family (how many investigations to propose to the patients, and how often); C) possible interaction between genes and environmental factors (for instance, a gene carrier--in this family--developed an endometrial carcinoma after standard tamoxifen adjuvant therapy for breast cancer).

Adult↗