title: Assessing the pathogenicity of MLH1 missense mutations in patients with suspected hereditary nonpolyposis colorectal cancer: correlation with clinical, genetic and functional features.
abstract: Assessing the pathogenicity of missense mutations of MLH1 and MSH2 is critical to counsel patients with suspected hereditary nonpolyposis colorectal cancer (HNPCC). Approximately 32% of all MLH1 mutations and 18% of MSH2 mutations are missense variants which often have an uncertain genetic significance. To assess the pathogenicity of four MLH1 missense mutations which were found in five patients with suspected HNPCC, P648S (CCC --> TCC), L559R (CTG --> CGG), K618A (AAG --> GCG), Y646C (TAT --> TGT), we studied their ability to disrupt MLH1 protein function and their relationship with all those clinical, genetic and pathological features which are typical of this syndrome. Our results indicated that the P648S and L559R mutations were probably pathogenic because they disrupted MLH1 protein interaction with its partner PMS2 in vitro and abolished MLH1 expression in HCT116 cells. In addition these variants were associated with features often found in HNPCC patients: in particular high microsatellite instability, occurrence of high grade tumours and, in one case, strong family history. The pathogenicity of the K618A and Y646C mutations was questionable as their correlation with features typical of HNPCC was low and the outcome of the functional analysis was ambiguous. These observations suggested that a clinically usable assessment of the pathogenicity of MLH missense variants can be achieved through the analysis of multiple mutation characteristics among which loss of protein function, occurrence of microsatellite instability and family history seemed to have a predominant role.
authors.affiliation: Oncologia Medica, Facolta' di Medicina e Chirurgia, Università Politecnica delle Marche, Ancona, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Belvederesi
authors.forename: Francesca
authors.initials: F
authors.lastname: Bianchi
authors.forename: Cristian
authors.initials: C
authors.lastname: Loretelli
authors.forename: Daniela
authors.initials: D
authors.lastname: Gagliardini
authors.forename: Eva
authors.initials: E
authors.lastname: Galizia
authors.forename: Raffaella
authors.initials: R
authors.lastname: Bracci
authors.forename: Saverio
authors.initials: S
authors.lastname: Rosati
authors.forename: Italo
authors.initials: I
authors.lastname: Bearzi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Viel
authors.forename: Riccardo
authors.initials: R
authors.lastname: Cellerino
authors.forename: Emilio
authors.initials: E
authors.lastname: Porfiri
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000328:Adult; D000368:Aged; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D016022:Case-Control Studies; D002460:Cell Line; D045744:Cell Line, Tumor; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics* / Q000503:physiopathology; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D017422:Sequence Analysis, DNA; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C497172:MSH2 protein, human; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes