A fast, sensitive and accurate high resolution melting (HRM) technology-based assay to screen for common K-ras mutations

Background: Increasing evidence points to a negative correlation between K-ras mutations and patient's response to, or survival benefit after, treatment with EGFR-inhibitors. Therefore, rapid and reliable assays for mutational analysis of the K-ras gene are strongly needed. Methods: We designed a high resolution melting (HRM) technology-based approach followed by direct sequencing to determine K-ras exon 1 (codons 12/13) tumour genotype. Results: Reconstruction experiments demonstrated an analytical sensitivity of the K-ras exon 1 HRM assay following sequencing of 1.5-2.5% of mutated DNA in a background of wild-type DNA. Assay reproducibility and accuracy were 100%. Application of the HRM assay following sequencing onto genomic DNA isolated from formalin-fixed paraffin-embedded tumour specimens of non-small cell lung cancer (n = 91) and colorectal cancer (n = 7) patients revealed nucleotide substitutions at codons 12 or 13, including a homozygous mutation, in 33 (34%) and 5 (5%) cases, respectively. Comparison to conventional nested-PCR following cycle-sequencing showed an overall high agreement in genotype findings (kappa value of 0.96), with more mutations detected by the HRM assay following sequencing. Conclusions: HRM allows rapid, reliable and sensitive pre-screening of routine diagnostic specimens for subsequent genotyping of K-ras mutations, even if present at low abundance or homozygosity, and may considerably facilitate personalized therapy planning.