Isolation and genomic analysis of circulating tumor cells from castration resistant metastatic prostate cancer

Mark Jesus M Magbanua,Jeff Simko,Eduardo V Sosa,Dan Pinkel,John W Park,Janet H Scott,Colin Collins,Charles J Ryan

doi:10.1186/1471-2407-12-78

Abstract

BackgroundThe 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.MethodsWe 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).ResultsCTCs 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.ConclusionsWe 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.

Highlights

The number of circulating tumor cells (CTCs) in metastatic prostate cancer patients provides prognostic and predictive information
Patient samples Clinical samples were obtained from 20 castration resistant prostate cancer patients who were recruited from November 2008 to August 2009 at the University of California San Francisco (UCSF) to participate in our study (Table 1)
In summary, our pilot study demonstrates that CTCs can be feasibly isolated away from hematopoietic cells via immunomagnetic enrichment (IE)/fluorescence activated cell sorting (FACS) and profiled for genome-wide copy number aberrations

Summary

Introduction

The number of circulating tumor cells (CTCs) in metastatic prostate cancer patients provides prognostic and predictive information. It is the molecular characterization of CTCs that offers insight into the biology of these tumor cells in the context of personalized treatment. Cancer metastasis typically occurs through hematogenous spread, and strategies to detect tumor cells in the blood have been developed. Such detection methods may be used in applications such as staging/prognosis, disease monitoring, and studies of the metastatic process [1,2,3]. Detailed molecular characterization of CTCs, has been hampered because of their rarity and the difficulty of isolating CTCs for analytical techniques [for review see Ref. [3]]

Methods

Results

Discussion

Conclusion