title: Methylation analysis of MLH1 improves the selection of patients for genetic testing in Lynch syndrome.
abstract: Inactivation of MLH1 due to promoter hypermethylation strongly suggests a sporadic origin, providing exclusion criteria for Lynch syndrome. The aim of this study is to compare the utility of methylation analysis of MLH1 and BRAF V600E mutations for the selection of patients with MLH1 negative colorectal cancer for genetic testing. MLH1 methylation status was evaluated by MethyLight and methylation-specific MLPA (MS-MLPA) in tumor DNA from 73 colorectal cancer patients with loss of MLH1 protein expression. These tumors were analyzed for BRAF V600E mutations, and genetic testing for germline MLH1 mutations was performed in all corresponding patients. Ten patients had germline mutations in MLH1 and none of their tumors showed significant MLH1 methylation or BRAF V600E mutation. MLH1 genetic testing excluded patients by MethyLight in 47 patients (64%), by MS-MLPA in 49 (67%), and BRAF V600E mutation in only 25 patients (34%) (chi(2) P = 0.00001). Specificity was 75% for MethyLight, 78% for MS-MLPA and 40% for BRAF V600E mutation. The use of MethyLight or MS-MLPA instead of BRAF mutation resulted in a cost reduction of 41% and 45%, respectively, per every MLH1 mutation detected. Taken together, methylation analysis of MLH1 shows better performance characteristics than BRAF V600E mutation in the selection of patients for genetic testing of MLH1, especially when using MS-MLPA.
authors.affiliation: Unidad de Investigación, Hospital General Universitario de Alicante, Pintor Baeza 12, 03010 Alicante, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Pérez-Carbonell
authors.forename: Cristina
authors.initials: C
authors.lastname: Alenda
authors.forename: Artemio
authors.initials: A
authors.lastname: Payá
authors.forename: Adela
authors.initials: A
authors.lastname: Castillejo
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Barberá
authors.forename: Carmen
authors.initials: C
authors.lastname: Guillén
authors.forename: Estefanía
authors.initials: E
authors.lastname: Rojas
authors.forename: Nuria
authors.initials: N
authors.lastname: Acame
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Gutiérrez-Aviñó
authors.forename: Antoni
authors.initials: A
authors.lastname: Castells
authors.forename: Xavier
authors.initials: X
authors.lastname: Llor
authors.forename: Montserrat
authors.initials: M
authors.lastname: Andreu
authors.forename: José-Luis
authors.initials: JL
authors.lastname: Soto
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Jover
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000368:Aged; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics*; D019175:DNA Methylation / Q000235:genetics*; D005260:Female; D005820:Genetic Testing / Q000191:economics / Q000379:methods*; D018095:Germ-Line Mutation / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics*; D018579:Patient Selection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1