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BMC Cancer. 2012; 12: 78.
Published online Feb 28, 2012. doi:  10.1186/1471-2407-12-78
PMCID: PMC3395839
Isolation and genomic analysis of circulating tumor cells from castration resistant metastatic prostate cancer
Mark Jesus M Magbanua,1 Eduardo V Sosa,1 Janet H Scott,1 Jeff Simko,2,5 Colin Collins,3 Dan Pinkel,4,5 Charles J Ryan,1,5 and John W Parkcorresponding author1,5,6
1Department of Medicine, Division of Hematology/Oncology, University of California San Francisco (UCSF), San Francisco, CA, USA
2Department of Pathology and Urology, UCSF, San Francisco, CA, USA
3Vancouver Prostate Center and Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada
4Department of Laboratory Medicine, UCSF, San Francisco, CA, USA
5Helen Diller Family Comprehensive Cancer Center, UCSF, San Francisco, CA, USA
6Division of Hematology/Oncology, University of California San Francisco, 2340 Sutter St. Box 1387, San Francisco, CA 94115, USA
corresponding authorCorresponding author.
Mark Jesus M Magbanua: mark.magbanua/at/ucsf.edu; Eduardo V Sosa: eduardo.sosa/at/ucsf.edu; Janet H Scott: janet.scott/at/ucsf.edu; Jeff Simko: jeff.simko/at/ucsf.edu; Colin Collins: ccollins/at/prostatecentre.com; Dan Pinkel: pinkel/at/cc.ucsf.edu; Charles J Ryan: ryanc/at/medicine.ucsf.edu; John W Park: jpark/at/cc.ucsf.edu
Received November 18, 2011; Accepted February 28, 2012.
Abstract
Background
The number of circulating tumor cells (CTCs) in metastatic prostate cancer patients provides prognostic and predictive information. However, it is the molecular characterization of CTCs that offers insight into the biology of these tumor cells in the context of personalized treatment.
Methods
We developed a novel approach to isolate CTCs away from hematopoietic cells with high purity, enabling genomic analysis of these cells. The isolation protocol involves immunomagnetic enrichment followed by fluorescence activated cell sorting (IE/FACS). To evaluate the feasibility of isolation of CTCs by IE/FACS and downstream genomic profiling, we conducted a pilot study in patients with metastatic castration resistant prostate cancer (CRPC). Twenty (20) sequential CRPC patients were assayed using CellSearch™. Twelve (12) patients positive for CTCs were subjected to immunomagnetic enrichment and fluorescence activated cell sorting (IE/FACS) to isolate CTCs. Genomic DNA of CTCs was subjected to whole genome amplification (WGA) followed by gene copy number analysis via array comparative genomic hybridization (aCGH).
Results
CTCs from nine (9) patients successfully profiled were observed to have multiple copy number aberrations including those previously reported in primary prostate tumors such as gains in 8q and losses in 8p. High-level copy number gains at the androgen receptor (AR) locus were observed in 7 (78%) cases. Comparison of genomic profiles between CTCs and archival primary tumors from the same patients revealed common lineage. However, high-level copy number gains in the AR locus were observed in CTCs, but not in the matched archival primary tumors.
Conclusions
We developed a new approach to isolate prostate CTCs without significant leukocyte admixture, and to subject them to genome-wide copy number analysis. Our assay may be utilized to explore genomic events involved in cancer progression, e.g. development of castration resistance and to monitor therapeutic efficacy of targeted therapies in clinical trials in a relatively non-invasive manner.
Keywords: Circulating tumor cells, Castration resistant prostate cancer, Copy number analysis, Array comparative genomic hybridization, Androgen receptor
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