Angelika Roesler

High-Resolution Melting Analysis as a Sensitive Prescreening Diagnostic Tool to Detect KRAS, BRAF, PIK3CA, and AKT1 Mutations in Formalin-Fixed, Paraffin-Embedded Tissues

CONTEXT As the availability of targeted therapies for several tumor types increases, the need for rapid and sensitive mutation screening is growing. KRAS mutations constitutively activate the RAS/RAF/mitogen-activated protein kinase (MAPK) pathway and therefore play an important role in anti-epidermal growth factor receptor therapy for patients with colorectal cancers. Mutationally activated PIK3CA and AKT1 genes are promising therapeutic targets in breast cancer. In 60% to 70% of malignant melanomas, a mutation in BRAF can be found. Thus, the blocking of the oncogenic signaling induced by this mutation is now used as treatment approach. OBJECTIVE To establish high-resolution melting assays for routinely used predictive analyses of KRAS , AKT1 , PIK3CA , and BRAF mutations. DESIGN High-resolution melting assays were developed by using specifically designed primers and genomic DNA isolated either from cell lines or formalin-fixed paraffin-embedded tissues, oligonucleotides, or plasmids. Melting curve analyses were performed on the LightCyler platform and mutation analyses were additionally confirmed by Sanger sequencing. RESULTS We developed high-resolution melting assays by using genomic DNA containing the desired mutation, which enabled us to detect percentages of mutated DNA (3.1% to 12.5%) mixed in a wild-type background. Assays were evaluated by hybridization probes and/or Sanger sequencing to exclude pseudogene amplification. The high-resolution melting assays were validated with genomic DNA from different tumor entities. The concordance between Sanger sequencing and high-resolution melting was 99% for KRAS exon 2 and PIK3CA exon 20 and 100% for the remaining assays. CONCLUSIONS High-resolution melting provides a valid and powerful tool for detecting genomic mutations efficiently.