Abstract 2088: Detection of PIK3CA somatic mutations in cell-free DNA of breast cancer patients by high-resolution melting curve analysis

Abstract

Abstract Introduction: Somatic mutations in the gene encoding for the phosphatidyl-inositol 3-kinase (PI3K) catalytic subunit, PIK3CA, have been discovered in many different human cancers. We have recently developed a high-resolution melting curve analysis method for the detection of the three hotspot mutations of PIK3CA gene (Vorkas et al, J of Mol Diagn 2010). The aim of our study was to evaluate this method for the presence of PIK3CA mutations in cell-free DNA (cfDNA) circulating in plasma of breast cancer patients and healthy individuals. Patients and methods: cfDNA was isolated from plasma (200μL) of 30 patients with operable breast cancer, 45 patients with metastatic breast cancer and 12 healthy donors. After DNA extraction, real-time PCR was performed in triplicate for all samples in the LightCycler (Roche), in the presence of LC-Green Plus saturating dye (Idaho Technology Inc.). High-resolution melting curves were obtained with HR-1 High Resolution Melter (Idaho Technology Inc.). Results: We identified 15 cfDNA samples mutated out of 75 tested (20%). 3/75 (4%) cfDNA samples were mutated within the exon 9 amplified region, and 12/75 (16%) cfDNA samples were mutated within exon 20 (31.6%). In operable breast cancer 1/30 (3.3%) cfDNA sample was mutated in exon 9 and 3/30 (10%) cfDNA samples were mutated in exon 20, while in metastatic breast cancer 2/45 (4.4%) cfDNA samples wer mutated in exon 9 and 9/45 (20%) cfDNA samples were mutated in exon 20. PIK3CA mutations were not detected in any of the 12 cfDNA samples from healthy donors, used as negative controls. Conclusions: Using High-Resolution Melting curve Analysis (HRMA) PIK3CA gene mutations were detected in cfDNA circulating in plasma of patients with operable and metastatic breast cancer, but not in plasma of healthy individuals. The prognostic significance of this finding will be evaluated when a longer follow up period will be completed for these patients and a larger number of clinical samples will be analyzed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2088. doi:1538-7445.AM2012-2088