Using Bridged Nucleic Acids for Detection of Phosphatidyl 3-Kinase Catalytic Subunit Alpha Mutation

Abstract

PIK3CA is responsible for producing the catalytic subunit (p110) of the lipid kinase heterodimer phosphoinositide 3-kinase (PIK3 or PI3K). The E545Q mutation, which is due to single nucleotide mutation (c.1633G>C) and found in the highly conserved helical domain of PIK3CA, has been linked to cases of non-small-cell lung carcinoma (NSCLC). Bridged nucleic acids (BNAs) are modified nucleic acid analogs that have the ability to bind DNA with high affinity so that the resulting Tm values are altered. Moreover, the BNA’s resistance to nucleases leads to increased stability in vitro and in vivo. We designed a couple of BNA probes to bind more tightly to wild-type DNA than to mutant DNA. Thus, using BNA we observed lower resulting Tm values of samples of DNA containing the mutant sequence than that of the wild-type DNA. The Tm values of the mutant were significantly lower than that of the wild-type. Using BNAs a greater difference between Tm values was observed than that of the control (e.g. solely DNA used, with no BNAs involved). This method of using BNAs for the detection of PIK3CA mutations was successful and could be utilized for earlier and more accurate diagnosis of NSCLC with only the use of BNAs and a Tm value measurement.