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.
Centre for Human Genetics, Department of Human Genetics, University Hospital Leuven, KU Leuven , Leuven , Belgium.
Front Oncol. 2013 Dec 31;3:320. doi: 10.3389/fonc.2013.00320. eCollection 2013.
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.
骨髓中检测到的弥散性肿瘤细胞 (DTCs) 已被证明是乳腺癌女性的独立预后因素。然而，肿瘤细胞扩散的机制仍不清楚，需要更详细的知识来充分了解为什么有些细胞保持休眠而有些细胞转移。单细胞测序为剖析原发性肿瘤亚克隆和 DTC 的遗传内容开辟了可能性。先前对 DTC 中遗传变化的研究采用了单细胞阵列比较基因组杂交技术，该技术提供了关于较大异常的信息。迄今为止，下一代测序提供了发现新的、更小的和拷贝中性遗传变化的可能性。在这项研究中，我们对两名乳腺癌患者的 DTC 进行了全基因组扩增，随后进行了下一代测序分析。我们比较了 DTC 和相应原发性肿瘤的拷贝数图谱，分别来自测序和 SNP 比较基因组杂交 (CGH) 数据。虽然一个肿瘤主要显示全臂增益和缺失，但另一个肿瘤具有更复杂的改变，以及亚克隆扩增和缺失。原发性肿瘤中的全臂增益或缺失通常也在相应的 DTC 中观察到。两个原发性肿瘤都显示出 1q 染色体的扩增和 16q 部分缺失，这在相应的 DTC 中被捕获。有趣的是，还观察到明显的差异，表明 DTC 在拷贝数水平上进一步进化。这项研究为 DTC 测序及其与原发性拷贝数图谱的相关性提供了原理证明。这些分析深入了解了肿瘤细胞的扩散，并显示与原发性肿瘤相比，DTC 中持续的拷贝数进化。
