Mutations of 1p genes do not consistently abrogate tumor suppressor functions in 1p-intact neuroblastoma. Mutations of 1p genes do not consistently abrogate tumor suppressor functions in 1p-intact neuroblastoma

Deletion of 1p is associated with poor prognosis in neuroblastoma, however selected 1p-intact patients still experience poor outcomes. Since mutations of 1p genes may mimic the deleterious effects of chromosomal loss, we studied the incidence, spectrum and effects of mutational variants in 1p-intact neuroblastoma. Methods: We characterized the 1p status of 325 neuroblastoma patients, and correlated the mutational status of 1p tumor suppressors and neuroblastoma candidate genes with survival outcomes among 100 1p-intact cases, then performed functional validation of selected novel variants of 1p36 genes identified from our patient cohort. Results: Among patients with adverse disease characteristics, those who additionally had 1p deletion had significantly worse overall survival. Among 100 tumor-normal pairs sequenced, somatic mutations of 1p tumor suppressors KIF1Bβ and CHD5 were most frequent (2%) after ALK and ATRX (8%), and BARD1 (3%). Mutations of neuroblastoma candidate genes were associated with other synchronous mutations and concurrent 11q deletion (P = 0.045). In total, 24 of 38 variants identified were novel and predicted to be deleterious or pathogenic. Functional validation identified novel KIF1Bβ I1355M variant as a gain-of-function mutation with increased expression and tumor suppressive activity, correlating with indolent clinical behavior; another novel variant CHD5 E43Q was a loss-of-function mutation with decreased expression and increased long-term cell viability, corresponding with aggressive disease characteristics. Conclusions: Our study showed that chromosome 1 gene mutations occurred frequently in 1p-intact neuroblastoma, but may not consistently abrogate the function of bonafide 1p tumor suppressors. These findings may augment the evolving model of compounding contributions of 1p gene aberrations toward tumor

1号染色体短臂（1p）缺失与神经母细胞瘤的不良预后密切相关，但部分1p完整的患者仍会出现不良预后结局。鉴于1p相关基因的突变可模拟染色体缺失的有害效应，本研究针对1p完整型神经母细胞瘤，分析了其突变变异的发生率、谱型及效应。方法：本研究对325例神经母细胞瘤患者的1p状态进行了鉴定，并在100例1p完整型病例中，将1p肿瘤抑制基因及神经母细胞瘤候选基因的突变状态与生存结局进行关联分析；此外，针对从本研究患者队列中筛选出的1p36基因新型变异体开展了功能验证。结果：在具有不良疾病特征的患者中，同时存在1p缺失者的总生存期显著更差。在完成测序的100例肿瘤-正常组织配对样本中，1p肿瘤抑制基因KIF1Bβ与CHD5的体细胞突变发生率为2%，其发生频率仅次于ALK与ATRX（8%）及BARD1（3%）。神经母细胞瘤候选基因的突变与其他同步突变及伴随的11q缺失存在关联（P=0.045）。本研究共鉴定出38种变异体，其中24种为新型变异，且经预测具有有害或致病效应。功能验证结果显示，新型KIF1Bβ I1355M变异体为功能获得性突变，其表达水平与肿瘤抑制活性均有所升高，与惰性临床行为相关；另一新型变异体CHD5 E43Q则为功能丧失性突变，其表达水平降低且长期细胞存活率升高，对应侵袭性疾病特征。结论：本研究表明，1p完整型神经母细胞瘤中1号染色体相关基因的突变较为常见，但此类突变未必会持续破坏真正的1p肿瘤抑制基因功能。本研究结果可进一步完善1p基因畸变对肿瘤发生的复合贡献这一不断发展的理论模型。