Biostatistics Advance Access published online on October 15, 2009
Biostatistics, doi:10.1093/biostatistics/kxp045
PICNIC: an algorithm to predict absolute allelic copy number variation with microarray cancer data
Cancer Genome Project, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK cdg{at}sanger.ac.uk
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High-throughput oligonucleotide microarrays are commonly employed to investigate genetic disease, including cancer. The algorithms employed to extract genotypes and copy number variation function optimally for diploid genomes usually associated with inherited disease. However, cancer genomes are aneuploid in nature leading to systematic errors when using these techniques. We introduce a preprocessing transformation and hidden Markov model algorithm bespoke to cancer. This produces genotype classification, specification of regions of loss of heterozygosity, and absolute allelic copy number segmentation. Accurate prediction is demonstrated with a combination of independent experimental techniques. These methods are exemplified with affymetrix genome-wide SNP6.0 data from 755 cancer cell lines, enabling inference upon a number of features of biological interest. These data and the coded algorithm are freely available for download.
Keywords: Allelic; Cancer; Copy; Number; Somatic; Variation
Received July 23, 2008; revised November 10, 2009; revised March 16, 2009; revised April 27, 2009; revised July 13, 2009; revised August 24, 2009; accepted for publication September 15, 2009.