Rapid Detection of Somatic Mutations in Cancer Genes
In the context of personalized cancer treatment, tumor mutation analysis by DNA sequencing has been
described frequently as the “gold standard”, yet DNA sequencing is one of the least sensitive methods
for characterizing mutation. At least 20% of a DNA population must be mutant for the mutation to be
detected by standard DNA sequencing. Implicit acceptance that this level of sensitivity is sufficient to characterize tumor mutations only makes sense if one assumes that tumors are monoclonal and that all the critical driver mutations will be present in the bulk of the tumor. Yet these are incorrect
assumptions. In fact, it has become clear that most if not all colon tumors are polyclonal and heterogeneous. Consequently, tumor driver mutations may not be detectable using standard DNA sequencing methods. In order to rapidly detect these low frequency mutations in tumor derived DNA we have developed a new technology that allows the detection of tumor driver and drug resistance somatic mutations at <0.1% sensitivity using quantitative PCR (qPCR) without the need for digital PCR or droplet digital PCR (ddPCR) methodology. We utilize xeno-nucleic acid (XNA) clamping probes that are specific for the target gene wild-type template and allow only the selective amplification of mismatched mutant templates. Direct detection of driver and drug resistance mutations within 2 hours of obtaining samples in KRAS, NRAS, BRAF, EGFR and JAK2 utilizing real-time qPCR with interchelating fluorescence dye detection.
described frequently as the “gold standard”, yet DNA sequencing is one of the least sensitive methods
for characterizing mutation. At least 20% of a DNA population must be mutant for the mutation to be
detected by standard DNA sequencing. Implicit acceptance that this level of sensitivity is sufficient to characterize tumor mutations only makes sense if one assumes that tumors are monoclonal and that all the critical driver mutations will be present in the bulk of the tumor. Yet these are incorrect
assumptions. In fact, it has become clear that most if not all colon tumors are polyclonal and heterogeneous. Consequently, tumor driver mutations may not be detectable using standard DNA sequencing methods. In order to rapidly detect these low frequency mutations in tumor derived DNA we have developed a new technology that allows the detection of tumor driver and drug resistance somatic mutations at <0.1% sensitivity using quantitative PCR (qPCR) without the need for digital PCR or droplet digital PCR (ddPCR) methodology. We utilize xeno-nucleic acid (XNA) clamping probes that are specific for the target gene wild-type template and allow only the selective amplification of mismatched mutant templates. Direct detection of driver and drug resistance mutations within 2 hours of obtaining samples in KRAS, NRAS, BRAF, EGFR and JAK2 utilizing real-time qPCR with interchelating fluorescence dye detection.
