KRAS and BRAF mutations in serum exosomes from patients with colorectal cancer in a Chinese population

The efficacy of epidermal growth factor receptor- targeted therapy is significantly associated with Kirsten rat sarcoma viral oncogene homolog (KRAS) and B-raf serine/threonine kinase proto-oncogene (BRAF) mutation in patients with colorectal cancer (CRC), for which the standard gene testing is currently performed using tumor tissue DNA. The aim of the present study was to compare the presence of KRAS and BRAF mutations in the serum exosome and primary tumor tissue from patients with CRC. Genomic DNA were extracted from the tumor tissues of 35 patients with histologically-confirmed CRC and exosomal mRNA were obtained from peripheral blood, which were collected from the corresponding patients prior to surgery. Three mutations in the KRAS gene (codons 12, 13 and 61) and a mutation in the BRAF gene (codon 600) were detected using a polymerase chain reaction-based sequencing method and their presence were compared between tumor tissues and the matched serum exosomes. The KRAS mutation rates in tumor tissues and the matched serum exosomes were 57.6 and 42.4%, respectively, which was not significantly different (P=0.063). The detection rate of the BRAF mutation was 24.2 and 18.2% in tumor tissues and the matched serum exosomes, respectively, and there was no significant difference (P=0.500). The patients with CRC that had a KRAS mutation of codon 12 in exon 2 in their tumor tissues and serum exosomes were significantly older compared with those without this mutation (tumor tissue, P=0.002; serum exosome, P=0.022). The sensitivity of KRAS and BRAF mutation detection using exosomal mRNA was 73.7 and 75%, respectively. The specificity of the detected mutations exhibited an efficiency of 100%, and the total consistency rate was 94.9 and 93.9% for KRAS and BRAF mutations, respectively. These results suggested that serum exosomal mRNA may be used as a novel source for the rapid and non-invasive genotyping of patients with CRC.