Department of Clinical Genetics, Lund University, Skåne University and Regional Laboratories, Lund, Sweden.
PLoS One. 2013;8(3):e59268. doi: 10.1371/journal.pone.0059268. Epub 2013 Mar 21.
Neuroblastomas (NBs) are tumours of the sympathetic nervous system accounting for 8-10% of paediatric cancers. NBs exhibit extensive intertumour genetic heterogeneity, but their extent of intratumour genetic diversity has remained unexplored. We aimed to assess intratumour genetic variation in NBs with a focus on whole chromosome changes and their underlying mechanism. Allelic ratios obtained by SNP-array data from 30 aneuploid primary NBs and NB cell lines were used to quantify the size of clones harbouring specific genomic imbalances. In 13 cases, this was supplemented by fluorescence in situ hybridisation to assess copy number diversity in detail. Computer simulations of different mitotic segregation errors, single cell cloning, analysis of mitotic figures, and time lapse imaging of dividing NB cells were used to infer the most likely mechanism behind intratumour variation in chromosome number. Combined SNP array and FISH analyses showed that all cases exhibited higher inter-cellular copy number variation than non-neoplastic control tissue, with up to 75% of tumour cells showing non-modal chromosome copy numbers. Comparisons of copy number profiles, resulting from simulations of different segregation errors to genomic profiles of 120 NBs indicated that loss of chromosomes from a tetraploid state was more likely than other mechanisms to explain numerical aberrations in NB. This was supported by a high frequency of lagging chromosomes at anaphase and polyploidisation events in growing NB cells. The dynamic nature of numerical aberrations was corroborated further by detecting substantial copy number diversity in cell populations grown from single NB cells. We conclude that aneuploid NBs typically show extensive intratumour chromosome copy number diversity, and that this phenomenon is most likely explained by continuous loss of chromosomes from a polyploid state.
神经母细胞瘤（NBs）是交感神经系统的肿瘤，占儿童癌症的 8-10%。NBs 表现出广泛的肿瘤间遗传异质性，但它们的肿瘤内遗传多样性程度仍未得到探索。我们旨在评估 NBs 中的肿瘤内遗传变异，重点关注全染色体变化及其潜在机制。从 30 个非整倍体原发性 NBs 和 NB 细胞系的 SNP 阵列数据获得的等位基因比，用于定量携带特定基因组不平衡的克隆的大小。在 13 个病例中，通过荧光原位杂交补充了这一点，以详细评估拷贝数多样性。不同有丝分裂分离错误、单细胞克隆、有丝分裂图分析和分裂 NB 细胞的延时成像的计算机模拟，用于推断肿瘤内染色体数量变异背后最可能的机制。结合 SNP 阵列和 FISH 分析表明，所有病例均表现出比非肿瘤对照组织更高的细胞间拷贝数变异，高达 75%的肿瘤细胞显示非模态染色体拷贝数。对不同分离错误模拟的拷贝数谱与 120 个 NBs 的基因组谱的比较表明，从四倍体状态丢失染色体比其他机制更有可能解释 NB 中的数值异常。这得到了在生长的 NB 细胞中后期滞后染色体和多倍体化事件的高频支持。通过检测从单个 NB 细胞生长的细胞群体中的大量拷贝数多样性，进一步证实了数值异常的动态性质。我们得出结论，非整倍体 NBs 通常表现出广泛的肿瘤内染色体拷贝数多样性，这种现象最可能是由从多倍体状态连续丢失染色体引起的。
