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High-resolution genomic profiling of disseminated tumor cells in prostate cancer

ABSTRACT: Circulating (CTCs) and disseminated (DTCs) tumor cells are of great interest to the field of cancer research as they provide a minimally-invasive window for assessing aspects of cancer biology including tumor heterogeneity, a means to discover biomarkers of disease behavior, and a way to identify and prioritize therapeutic targets in the emerging era of precision oncology. However, the rarity of CTC/DTC poses a significant challenge to the consistent success in analyzing the molecular features of these cells including genomic aberrations. Herein, we demonstrate our optimized and robust methods to reproducibly detect genomic copy number alterations in samples of 2-40 cells after whole-genome amplification using a high resolution SNP-array platform and refined computational algorithms. We have determined the limit of detection for heterogeneity within a sample as 50% and also demonstrated success in analyzing single cells. We validated the genes in genomic regions that are frequently amplified or deleted by qPCR and nCounter copy number quantification. We further applied these methods to DTCs isolated from individuals with advanced prostate cancer to confirm the highly aberrant nature of these cells. We compared copy number alterations of DTCs to matched metastatic tumors isolated from the same individual to gain biological insight. These developments provide high-resolution genomic profiling of single and rare cell populations, and should be applicable to a wide-range of sample sources.

ORGANISM(S): Homo sapiens

PROVIDER: GSE73180 | GEO | 2015/10/02

SECONDARY ACCESSION(S): PRJNA297628

REPOSITORIES: GEO

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Project description:The aim of this study was to establish a single-cell array comparative genomic hybridization (SCaCGH) method providing in-depth genomic analysis of circulating tumor cells (CTCs) and disseminated tumor cells (DTCs). The robustness and resolution limits of the method were estimated with different cell amounts of the breast cancer cell line SKBR3 using 44k and 244k arrays. Subsequent adjustments of the method were conducted analyzing the copy number profiles of 28 CTCs in combination with four hematopoietic cell (HC) controls from eight metastatic patients and of 24 DTCs, three probable HCs, and five HC controls from seven breast cancer patients and one healthy donor. The frequency of the major genomic gains and losses of the analyzed DTC revealed similarities to primary breast tumor samples with some evident differences. Three of the patients had available profiles for DTC and the corresponding primary tumor. In 2/3 of the examined DTCs, equivalent genomic changes and common aberration breakpoints were disclosed, both to each other and to the corresponding primary tumors. Interestingly, similar copy number changes were found in DTCs taken at time of diagnosis or in DTCs collected at 3-years relapse-free follow up. Residual immunomorphological characterized tumor cells showed balanced profiles with only minor aberrations. Three cells with unclear morphological identification showed either balanced profiles (n=2) or aberrations comparable to the primary tumor and DTC (n=1). SCaCGH may be a powerful tool for molecular characterisation of immunostained and morphological identified CTCs and DTCs to explore the malignant potential, therapeutic targets and tumor heterogeneity of single tumor cells. 24 DTCs, 3 probable HCs, and 5 HCs from 7 early-stage breast cancer patients, 28 CTCs and 4 HCs from 8 metastatic breast cancer patients, and 1 healthy donor were analysed. Comparison with the primary tumor was done in 3 patients. The reference for the patients was DNA from multiple anonymous female donors. This submission does not include the SKBR3 data obtained from the 44k array.

Project description:Background: Since the high relapse rate is considered to be responsible for the poor survival of stage M neuroblastoma patients, we tested whether the genomic information of bone marrow-derived disseminated tumor cells (DTCs) would help to better understand tumor evolution and to characterize the relapse-seeding clone. Methods: Seven samples from different regions of a primary tumor of a stage M neuroblastoma patient, corresponding DTCs at diagnosis, and DTCs and a metastatic tumor at relapse were analyzed by a high-density SNP array. Relapse-associated chromosomal aberrations found in this case were then validated in DTCs and tumor samples of 154 stage M neuroblastoma patients. Findings: In this case study, unique aberrations were evident in certain tissue/time points aside from a high concordance of genomic aberrations between all analyzed samples. Surprisingly, DTCs at diagnosis, and DTCs and the metastatic tumor at relapse all displayed a terminal deletion in 1q which was not detected in any of the primary tumor samples. In the validation cohort, 1q terminal deletions were found with a higher frequency in DTCs at diagnosis (17.8%) and at relapse (27.5%) compared to primary tumors (11%). 1q deletions were significantly associated with 19q and ATRX deletions. The presence of each individual aberration in the diagnostic DTCs was associated with an increased likelihood of an adverse event and in case of 19q deletion with a decreased overall survival. Moreover, PTPRD deletion and loss of chromosome Y had significantly higher frequencies in the relapse samples compared to the diagnostic samples. Interpretation: These data strongly suggest a branched clonal evolution and a parallel progression of primary and metastatic tumor cells. In addition, the higher frequency of relapse-associated genomic aberrations in the diagnostic DTCs compared to the primary tumors and their effect on the event-free survival rate indicate that analysis of DTCs at diagnosis may provide a higher probability for detecting the relapse-seeding clone compared to the primary tumor. Background: Since the high relapse rate is considered to be responsible for the poor survival of stage M neuroblastoma patients, we tested whether the genomic information of bone marrow-derived disseminated tumor cells (DTCs) would help to better understand tumor evolution and to characterize the relapse-seeding clone. Methods: Seven samples from different regions of a primary tumor of a stage M neuroblastoma patient, corresponding DTCs at diagnosis, and DTCs and a metastatic tumor at relapse were analyzed by a high-density SNP array. Relapse-associated chromosomal aberrations found in this case were then validated in DTCs and tumor samples of 154 stage M neuroblastoma patients. Findings: In this case study, unique aberrations were evident in certain tissue/time points aside from a high concordance of genomic aberrations between all analyzed samples. Surprisingly, DTCs at diagnosis, and DTCs and the metastatic tumor at relapse all displayed a terminal deletion in 1q which was not detected in any of the primary tumor samples. In the validation cohort, 1q terminal deletions were found with a higher frequency in DTCs at diagnosis (17.8%) and at relapse (27.5%) compared to primary tumors (11%). 1q deletions were significantly associated with 19q and ATRX deletions. The presence of each individual aberration in the diagnostic DTCs was associated with an increased likelihood of an adverse event and in case of 19q deletion with a decreased overall survival. Moreover, PTPRD deletion and loss of chromosome Y had significantly higher frequencies in the relapse samples compared to the diagnostic samples. Interpretation: These data strongly suggest a branched clonal evolution and a parallel progression of primary and metastatic tumor cells. In addition, the higher frequency of relapse-associated genomic aberrations in the diagnostic DTCs compared to the primary tumors and their effect on the event-free survival rate indicate that analysis of DTCs at diagnosis may provide a higher probability for detecting the relapse-seeding clone compared to the primary tumor.

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High-resolution genomic profiling of disseminated tumor cells in prostate cancer

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