Moving next-generation sequencing into the clinical realm: Detection of somatic mutations in cancer by targeted amplicon sequencing.

Abstract

60 Background: Molecular targeted therapies are increasingly important in treating cancer patients; robust analytically validated clinical assays are required for patient selection in early-stage clinical trials. The goal of Molecular Characterization Laboratory (MoCha) is to develop clinical diagnostic assays using next generation sequencing methods to support clinical studies in DCTD (CTEP). Methods: We developed a custom assay for somatic mutation detection using Fluidigm access array technology for amplicon generation followed by sequencing with the Illumina Miseq. A panel of 62 amplicons covering 6 Kb genomic regions was designed to detect 92 DNA loci, including common therapeutically actionable targets, in 37 genes. Analytical studies were performed using genomic DNA samples from fresh or formalin fixed cancer cell-lines and a normal hapmap individual (CEPH). We subsequently applied this assay to characterize DNA samples from both tumor tissues and blood specimens from ovarian cancer patients. Results: The assay detected known variants in both frozen and fixed DNA samples reproducibly with high sensitivity and specificity (<2%). Using a series of positive control plasmid spikes mixed into a normal reference CEPH DNA at pre-defined copy number ratios, we verified the assay is sensitive to detect variants at 5% allelic frequency with a minimum 400 X coverage. We identified somatic mutations in TP53 and PIK3CA in a few patients, and a germ-line variant D1583N in ATM genes occurring in one-third of tested patients. Conclusions: We developed and validated a next generation sequencing assay suitable for patient selection for clinical trials. Plans are to correlate sequencing and clinical results when clinical data are available.