title: Next-generation sequencing of disseminated tumor cells.
abstract: Disseminated tumor cells (DTCs) detected in the bone marrow have been shown as an independent prognostic factor for women with breast cancer. However, the mechanisms behind the tumor cell dissemination are still unclear and more detailed knowledge is needed to fully understand why some cells remain dormant and others metastasize. Sequencing of single cells has opened for the possibility to dissect the genetic content of subclones of a primary tumor, as well as DTCs. Previous studies of genetic changes in DTCs have employed single-cell array comparative genomic hybridization which provides information about larger aberrations. To date, next-generation sequencing provides the possibility to discover new, smaller, and copy neutral genetic changes. In this study, we performed whole-genome amplification and subsequently next-generation sequencing to analyze DTCs from two breast cancer patients. We compared copy-number profiles of the DTCs and the corresponding primary tumor generated from sequencing and SNP-comparative genomic hybridization (CGH) data, respectively. While one tumor revealed mostly whole-arm gains and losses, the other had more complex alterations, as well as subclonal amplification and deletions. Whole-arm gains or losses in the primary tumor were in general also observed in the corresponding DTC. Both primary tumors showed amplification of chromosome 1q and deletion of parts of chromosome 16q, which was recaptured in the corresponding DTCs. Interestingly, clear differences were also observed, indicating that the DTC underwent further evolution at the copy-number level. This study provides a proof-of-principle for sequencing of DTCs and correlation with primary copy-number profiles. The analyses allow insight into tumor cell dissemination and show ongoing copy-number evolution in DTCs compared to the primary tumors.
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway.
authors.forename: Elen K
authors.initials: EK
authors.lastname: Møller
authors.affiliation: Centre for Human Genetics, Department of Human Genetics, University Hospital Leuven, KU Leuven , Leuven , Belgium.
authors.forename: Parveen
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Centre for Human Genetics, Department of Human Genetics, University Hospital Leuven, KU Leuven , Leuven , Belgium ; Single-Cell Genomics Centre, Wellcome Trust Sanger Institute , Hinxton , UK.
authors.forename: Thierry
authors.initials: T
authors.lastname: Voet
authors.affiliation: Institute for Genomics and Systems Biology, Department of Human Genetics, The University of Chicago , Chicago, IL , USA.
authors.forename: April
authors.initials: A
authors.lastname: Peterson
authors.affiliation: Cancer Genome Project, Wellcome Trust Sanger Institute , Hinxton , UK ; Department of Human Genetics, VIB and KU Leuven , Leuven , Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Van Loo
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; Department of Oncology, Division of Surgery and Cancer Medicine, Oslo University Hospital Radiumhospitalet , Oslo , Norway.
authors.forename: Randi R
authors.initials: RR
authors.lastname: Mathiesen
authors.affiliation: Department of Pathology, Oslo University Hospital Radiumhospitalet , Oslo , Norway.
authors.forename: Renathe
authors.initials: R
authors.lastname: Fjelldal
authors.affiliation: Institute for Genomics and Systems Biology, Department of Human Genetics, The University of Chicago , Chicago, IL , USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Grundstad
authors.affiliation: Department of Pathology, Oslo University Hospital Radiumhospitalet , Oslo , Norway.
authors.forename: Elin
authors.initials: E
authors.lastname: Borgen
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway.
authors.forename: Lars O
authors.initials: LO
authors.lastname: Baumbusch
authors.affiliation: K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway ; Department of Oncology, Division of Surgery and Cancer Medicine, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Naume
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway.
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Børresen-Dale
authors.affiliation: Institute for Genomics and Systems Biology, Department of Human Genetics, The University of Chicago , Chicago, IL , USA.
authors.forename: Kevin P
authors.initials: KP
authors.lastname: White
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway.
authors.forename: Silje
authors.initials: S
authors.lastname: Nord
authors.affiliation: Department of Genetics, Institute for Cancer Research, Oslo University Hospital Radiumhospitalet , Oslo , Norway ; K.G. Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, Faculty of Medicine, University of Oslo , Oslo , Norway ; Department of Clinical Molecular Biology (EpiGen), Medical Division, Akershus University Hospital , Lørenskog , Norway.
authors.forename: Vessela N
authors.initials: VN
authors.lastname: Kristensen
keywords: circulating tumor cells; clonal evolution; disseminating tumor cells; single tumor cell sequencing; tumor heterogeneity