title: Allele-specific copy number profiling by next-generation DNA sequencing.
abstract: The progression and clonal development of tumors often involve amplifications and deletions of genomic DNA. Estimation of allele-specific copy number, which quantifies the number of copies of each allele at each variant loci rather than the total number of chromosome copies, is an important step in the characterization of tumor genomes and the inference of their clonal history. We describe a new method, falcon, for finding somatic allele-specific copy number changes by next generation sequencing of tumors with matched normals. falcon is based on a change-point model on a bivariate mixed Binomial process, which explicitly models the copy numbers of the two chromosome haplotypes and corrects for local allele-specific coverage biases. By using the Binomial distribution rather than a normal approximation, falcon more effectively pools evidence from sites with low coverage. A modified Bayesian information criterion is used to guide model selection for determining the number of copy number events. Falcon is evaluated on in silico spike-in data and applied to the analysis of a pre-malignant colon tumor sample and late-stage colorectal adenocarcinoma from the same individual. The allele-specific copy number estimates obtained by falcon allows us to draw detailed conclusions regarding the clonal history of the individual's colon cancer.
authors.affiliation: Department of Statistics, University of California, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.affiliation: Division of Oncology, School of Medicine, Stanford University, 291 Campus Dr, Stanford, CA 94305, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Bell
authors.affiliation: Division of Oncology, School of Medicine, Stanford University, 291 Campus Dr, Stanford, CA 94305, USA.
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Zavala
authors.affiliation: Division of Oncology, School of Medicine, Stanford University, 291 Campus Dr, Stanford, CA 94305, USA.
authors.forename: Hanlee P
authors.initials: HP
authors.lastname: Ji
authors.affiliation: Department of Statistics, The Wharton School, University of Pennsylvania, 3730 Walnut Street, Philadelphia, PA 19104, USA nzh@wharton.upenn.edu.
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Zhang
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics; D000483:Alleles; D060965:Clonal Evolution; D015179:Colorectal Neoplasms / Q000235:genetics; D018628:Gene Dosage; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000379:methods*; D012984:Software