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

Mutation searching was performed in the hMSH2 and hMLH1 genes in 20 Portugu ese families representing 124 registered affected individuals. Of the 20, 1 6 fulfilled the classic 'Amsterdam' criteria for HNPCC, whereas the remaini ng four families satisfied a modified set of criteria. These criteria requi red a CRC diagnosed before age 50years and cancers diagnosed in two other r elatives within the HNPCC spectrum. A multi-method approach was performed u sing the protein truncation test (PTT), single strand conformation polymorp hism (SSCP) with two different sets of conditions, heteroduplex analysis (H A) and denaturing gradient gel electrophoresis (DGGE). Putative phenotype-g enotype correlations were also explored. Ten different germline mutations w ere 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 h MLH1 germline mutations (four of seven in hMLH1 vs one of four in hMSH2). M ost of the families with rectal cancer were associated with hMLH1 (six of s even in hMLH1 vs two of four in hMSH2). A multi-technique approach is neces sary to identify a high percentage of germline mutations. Seven novel mutat ions were found in this Portuguese population.