Frequent Novel Variations Within MSH2 and MLH1 Genes in a Subset of Iranian Families With Hereditary Non-Polyposis Colorectal Cancer

摘要

Hereditary non-polyposis colorectal cancer (HNPCC) is the most frequent autosomal dominantpredisposition for development of colorectal cancer (CRC) caused by germline defects in mismatch repair(MMR) genes. Current study was aimed to find genetic variations in MSH2 and MLH1 genes and theircorrelation with the serum levels of Carcinoembryonic Antigen (CEA) in seven Iranian HNPCC families.Seven unrelated Iranian families including 11 HNPCC patients and 7 affected family members were selected.They were initially screened for mutations in exons 7 of MSH2 and exon 15 of MLH1 gene throughpolymerase chain reaction single-strand conformation polymorphism (PCR-SSCP). Positive PCR results werefurther analyzed through exon sequencing. Serum CEA level was determined using the ELISA test. PCRSSCPwas positive in 8 out of 18 patients (44%) for exons 7 of MSH2 gene, whereas two samples (11%)demonstrated to bear a mutation in exon 15 of the MLH1 gene. Sequencing analysis of both amplified exonsin positive and negative samples have confirmed no mutation in negative samples while revealed 5 and 7novel mutations in exons 7 and 15, respectively. The mean serum concentration of CEA had a significantdifference between HNPCC patients and their healthy family members. Our results demonstrated that thePCR-SSCP method has high specificity and sensitivity in the first step of mutation screening of HNPCCfamilies. High frequency of novel alterations found in the current assay may revise the mutation screening ofMSH2 and MLH1 genes and abet further assessment of their frequency among individual HNPCC patients.