Detection of mutations in mismatch repair genes in Portuguese families with hereditary non-polyposis colorectal cancer (HNPCC) by a multi-method approach

Abstract

Mutation searching was performed in the hMSH2 and hMLH1 genes in 20 Portuguese families representing 124 registered affected individuals. Of the 20, 16 fulfilled the classic 'Amsterdam' criteria for HNPCC, whereas the remaining four families satisfied a modified set of criteria. These criteria required a CRC diagnosed before age 50 years and cancers diagnosed in two other relatives within the HNPCC spectrum. A multi-method approach was performed using the protein truncation test (PTT), single strand conformation polymorphism (SSCP) with two different sets of conditions, heteroduplex analysis (HA) and denaturing gradient gel electrophoresis (DGGE). Putative phenotype-genotype correlations were also explored. Ten different germline mutations were identified. Six of these were found in hMLH1 in seven families and four in hMSH2 in four families. SSCP and DGGE had the highest diagnostic yields with the percentage of variants detected above 67% and together HA and PTT had the lowest. No single technique detected all variants. Trends for the absence of extracolonic manifestations were observed in families carrying hMLH1 germline mutations (four of seven in hMLH1 vs one of four in hMSH2). Most of the families with rectal cancer were associated with hMLH1 (six of seven in hMLH1 vs two of four in hMSH2). A multi-technique approach is necessary to identify a high percentage of germline mutations. Seven novel mutations were found in this Portuguese population.

The Germline MLH1 K618A Variant and Susceptibility to Lynch Syndrome-Associated Tumors

“…First, because the control population genotyped at the Mayo Clinic were not ethnically matched (nor ageand sex-matched) with the cases from the literature, there is the possibility of population stratification and bias. Similarly, the studies that we pooled for analysis were conducted with different populations (Sweden, 7 the United States, 13 Portugal, 17 Spain, 22 and Austria 26 ), which may have introduced a bias into our analysis. In addition, it is difficult to weld such different types of analyses into a single, coherent whole.…”

Novel MLH1 mutations and a novel MSH2 polymorphism identified by SSCP and DHPLC in Portuguese HNPCC families

“…In spite of the large number of mutations previously described (The Human Gene Mutation Database, Cardiff http://archive.uwcm.ac.uk/uwcm/mg/hgmd/search.html) the present study reveals additional ones in Portuguese HNPCC families which, together with other published studies (Isidro et al, 2000;Fidalgo et al, 2000) indicate a relatively high number of novel mutations in the Portuguese population.…”

Two novel mutations in hMLH1 gene in Iranian hereditary non-polyposis colorectal cancer patients

“…In many studies hMLH1 has been reported as the major gene. For example, in Portuguese and Brazilian populations mutations in hMLH1 were very frequent [22,23] and in a survey on Spanish families 64.3% of mutations were detected in hMLH1 and 35.7% in hMSH2 [24]. However, in some reports, such as a study by Irmejs et al [25] in Latvia, more mutations were reported in the hMSH2 gene.…”