CRE: a cost effective and rapid approach for PCR-mediated concatenation of KRAS and EGFR exons

Molecular diagnostics has changed the way lung cancer patients are treated worldwide. Of several different testing methods available, PCR followed by directed sequencing and amplification refractory mutation system (ARMS) are the two most commonly used diagnostic methods worldwide to detect mutations at  KRAS  exon 2 and  EGFR  kinase domain exons 18-21 in lung cancer. Compared to ARMS, the PCR followed by directed sequencing approach is relatively inexpensive but more cumbersome to perform. Moreover, with a limiting amount of genomic DNA from clinical formalin-fixed, paraffin-embedded (FFPE) specimens or fine biopsies of lung tumors, multiple rounds of PCR and sequencing reactions often get challenging. Here, we report a cost-effective single multiplex-PCR based method, CRE (for  C o-amplification of five  K R AS  and  E GFR  exons), followed by concatenation of the PCR product as a single linear fragment for direct sequencing. CRE is a robust protocol that can be adapted for routine use in clinical diagnostics with reduced variability, cost and turnaround time requiring a minimal amount of template DNA extracted from FFPE or fresh frozen tumor samples. As a proof of principle, CRE is able to detect the activating  EGFR  L858R and T790M  EGFR  mutations in lung cancer cell line and primary tumors.