The mRNA level of MLH1 in peripheral blood is a biomarker for the diagnosis of hereditary nonpolyposis colorectal cancer.

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by functional defects in mismatch repair (MMR) genes, including mutL homolog 1 (MLH1) and mutS homolog 2 (MSH2). This study aimed to assess whether the mRNA expression of MLH1 in peripheral blood could be used as a biomarkers for the diagnosis of HNPCC. The mRNA level of MLH1 was determined in 19 HNPCC families (46 members) using real-time quantitative polymerase chain reaction (qPCR). The mRNA levels of MLH1 in HNPCC were significantly lower than controls (P < 0.001). Receiver operating characteristic (ROC) curve showed a high diagnostic value of the mRNA level of MLH1 for the diagnosis of HNPCC with the area under curve of 0.858. At an optimal cut-off value (0.511), the mRNA level of MLH1 had a sensitivity of 81.3% and a specificity of 86.7% for distinguishing HNPCC from controls. In conclusion, the mRNA expression of MLH1 in peripheral blood may serve as a biomarker for the diagnosis of HNPCC.