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Neuroblastoma cells undergo transcriptomic alterations during dissemination into the bone marrow and subsequent tumor progression

ABSTRACT: Background: Neuroblastoma is the most common extracranial solid tumor in childhood. The vast majority of stage M patients present with disseminated tumor cells (DTCs) in the bone marrow (BM). Although these cells represent a major obstacle in the treatment of neuroblastoma patients, their transcriptomic profile was not intensively analyzed so far. Results: RNA-Seq of stage M primary tumors, enriched BM-derived DTCs and the corresponding non-tumor mononuclear cells (MNCs) revealed that DTCs largely retained the gene expression signature of tumors. However, we identified 322 genes that were differentially expressed (q < 0.001, |log2FC|>2). Particularly genes encoded by mitochondrial DNA were highly up-regulated in DTCs, whereas e.g. genes involved in angiogenesis were down-regulated. Furthermore, 224 genes were highly expressed in DTCs and only slightly, if at all, in MNCs (q < 8x10-75 log2FC > 6). Interestingly, we found that the gene expression profiles of diagnostic DTCs largely resembled those of relapse DTCs with only 113 differentially expressed genes under relaxed cut-offs (q < 0.01, |log2FC| > 0.5). Notably, relapse DTCs showed a positional enrichment of 31 down-regulated genes encoded by chromosome 19, including five tumor suppressor genes (SIRT6, PUMA, STK11, CADM4 and GLTSCR2). Conclusion: This first RNA-Seq analysis of DTCs from neuroblastoma patients revealed their unique expression profile in comparison to the corresponding MNCs and tumor samples, and, interestingly, also expression differences between diagnostic and relapse DTCs preferentially affecting chromosome 19. As these alterations might be associated with treatment failure and disease relapse, they should be considered for further functional studies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE94035 | GEO | 2017/08/21

SECONDARY ACCESSION(S): PRJNA368627

REPOSITORIES: GEO

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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.

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.

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Neuroblastoma cells undergo transcriptomic alterations during dissemination into the bone marrow and subsequent tumor progression

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