Ioncopy: a novel method for calling copy number alterations in amplicon sequencing data including significance assessment

Oncotarget. 2016 Mar 15;7(11):13236-47. doi: 10.18632/oncotarget.7451.

Abstract

Recently, it has been demonstrated that calling of copy number alterations (CNAs) from amplicon sequencing (AS) data is feasible. Most approaches, however, require non-tumor (germline) DNA for data normalization. Here, we present the method Ioncopy for CNA detection which requires no normal controls and includes a significance assessment for each detected alteration.Ioncopy was evaluated in a cohort of 184 clinically annotated breast carcinomas. A total number of 252 amplifications were detected, of which 183 (72.6%) could be validated by a call of an additional amplicon interrogating the same gene. Moreover, a total number of 33 deletions were found, whereof 27 (81.8%) could be validated. Analyzing the 16 most frequently amplified genes, validation rates of over 89% could be achieved for 11 of these genes. 11 of the top 16 genes showed significant overexpression in the amplified tumors. 89.5% of the HER2-amplified tumors were GRB7 and STARD3 co-amplified, whereas 68.4% of the HER2-amplified tumors had additional MED1 amplifications. Correlations between CNAs measured by amplicons in HER2 exons 19, 20 and 21 were strong (all R > 0.93). AS based detection of HER2 amplifications had a sensitivity of 90.0% and a specificity of 98.8% compared to the gold standard of HER2 immunohistochemistry combined with in situ hybridization.In summary, we developed and validated a novel method for detection and significance assessment of CNAs in amplicon sequencing data. Using Ioncopy, AS offers a straightforward and efficient approach to simultaneously analyze gene amplifications and gene deletions together with simple somatic mutations in a single assay.

Keywords: amplicon sequencing; breast cancer; copy number alterations; semiconductor sequencing; targeted sequencing.

MeSH terms

  • Algorithms*
  • Breast Neoplasms / genetics*
  • DNA Copy Number Variations / genetics
  • Female
  • Humans
  • Nucleic Acid Amplification Techniques / methods*
  • Sequence Analysis, DNA / methods*