Immunohistochemistry and microsatellite instability testing for selecting MLH1, MSH2 and MSH6 mutation carriers in hereditary non-polyposis colorectal cancer.
Hereditary non-polyposis colorectal cancer (HNPCC) represents 1-3% of all colorectal cancers. HNPCC is caused by a constitutional defect in a mismatch repair (MMR) gene, most commonly affecting the genes MLH1, MSH2 and MSH6. The MMR defect results in an increased cancer risk, with the greatest lifetime risk for colorectal cancer and other cancers associated to HNPCC. The HNPCC-associated tumor phenotype is generally characterized by microsatellite instability (MSI) and immunohistochemical loss of expression of the affected MMR protein. The aim of this study was to determine the sensitivity of IHC for MLH1, MSH2 and MSH6, and MSI analysis in tumors from known MMR gene mutation carriers. Fifty-eight paired normal and tumor samples from HNPCC families enrolled in our high-risk colorectal cancer registry were studied for the presence of germline mutations in MLH1, MSH2 and MSH6 by DGGE and direct sequencing. MSI analysis and immunostaining for MLH1, MSH2 and MSH6 were evaluated. Of the 28 patients with a real pathogenic mutation, loss of immunohistochemical expression for at least 1 of these MMR proteins was found, and all except 1 have MSI-H. Sensitivity by MSI analysis was 96%. IHC analysis had a sensitivity of 100% in detecting MMR deficiency in carriers of a pathogenic MMR mutation, and can be used to predict which gene is expected to harbor the mutation for MLH1, MSH2 and MSH6. This study suggests that both analyses are useful for selecting high-risk patients because most MLH1, MSH2 and MSH6 gene carriers will be detected by this 2-step approach. This practical method should have immediate application in the clinical work of patients with inherited colorectal cancer syndromes.
Molecular Oncology Laboratory, Hospital Clínico San Carlos, Martin Lagos s/n, 28040 Madrid, Spain. tcaldes@hcsc.es
Trinidad
T
Caldés
Javier
J
Godino
Ana
A
Sanchez
Cesar
C
Corbacho
Miguel
M
De la Hoya
Jose
J
Lopez Asenjo
Carmen
C
Saez
Julian
J
Sanz
Manuel
M
Benito
Santiago
S
Ramon Y Cajal
Eduardo
E
Diaz-Rubio
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D004252:DNA Mutational Analysis; D004260:DNA Repair; D043243:DNA Sequence, Unstable; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005192:Family Health; D017353:Gene Deletion; D018095:Germ-Line Mutation; D006579:Heterozygote; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D017403:In Situ Hybridization; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics*; D009687:Nuclear Proteins; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics*; D012306:Risk; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D004247:DNA; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein