A novel germline mutation of hMLH1 in a patient with hereditary nonpolyposis colorectal cancer

DNA mismatch repair genes, hMLH1 and hMSH2, assigned on chromosome 3p21-23 and 2p21-22 are involved in hereditary non-polyposis colorectal cancer (HNPCC). The heterozygous carrier of the mutated allele results in a mutator phenotype and accelerating tumorigenesis, which especially causes carcinomas in the gastrointestinal and genitourinary tracts. We screened germline mutations of mismatch repair genes hMLH1 and hMSH2 in a patient with multiple primary neoplasms (multiple stomach cancers, colon cancer and brain tumor) in a cancer clustered HNPCC family. Screening by long RT-PCR from the RNA extracted from puromycin-treated heparinized blood showed skipping of the exon 2 in hMLH1. The analysis of the genomic DNA showed a GT deletion in the splice-donor site of the exon 2, which is compatible with the splicing variant detected by long RT-PCR analysis. This is a novel germline mutation that has not been reported previously.