Shah Nilay, Wang Jianjun, Selich-Anderson Julia, Graham Garrett, Siddiqui Hasan, Li Xin, Khan Javed, Toretsky Jeffrey
Center for Childhood Cancer and Blood Diseases, The Research Institute of Nationwide Children's Hospital and The Ohio State University College of Medicine, Columbus, Ohio;
Oncogenomics Section, Advanced Technology Center, Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, Gaithersburg, Maryland;
Clin Cancer Res. 2014 Aug 15;20(16):4400-12. doi: 10.1158/1078-0432.CCR-13-1486. Epub 2014 Jun 19.
Neuroblastoma is an embryonic childhood cancer with high mortality. 13-cis retinoic acid (13-cisRA) improves survival for some patients, but many recur, suggesting clinical resistance. The mechanism of resistance and the normal differentiation pathway are poorly understood. Three-amino-acid loop extension (TALE) family genes are master regulators of differentiation. Because retinoids promote differentiation in neuroblastoma, we evaluated TALE family gene expression in neuroblastoma.
We evaluated expression of TALE family genes in RA-sensitive and -resistant neuroblastoma cell lines, with and without 13-cisRA treatment, identifying genes whose expression correlates with retinoid sensitivity. We evaluated the roles of one gene, PBX1, in neuroblastoma cell lines, including proliferation and differentiation. We evaluated PBX1 expression in primary human neuroblastoma samples by qRT-PCR, and three independent clinical cohort microarray datasets.
We confirmed that induction of PBX1 expression, and no other TALE family genes, was associated with 13-cisRA responsiveness in neuroblastoma cell lines. Exogenous PBX1 expression in neuroblastoma cell lines, mimicking induced PBX1 expression, significantly impaired proliferation and anchorage-independent growth, and promoted RA-dependent and -independent differentiation. Reduced PBX1 protein levels produced an aggressive growth phenotype and RA resistance. PBX1 expression correlated with histologic neuroblastoma subtypes, with highest expression in benign ganglioneuromas and lowest in high-risk neuroblastomas. High PBX1 expression is prognostic of survival, including in multivariate analysis, in the three clinical cohorts.
PBX1 is an essential regulator of differentiation in neuroblastoma and potentiates retinoid-induced differentiation. Neuroblastoma cells and tumors with low PBX1 expression have an immature phenotype with poorer prognosis, independent of other risk factors.
神经母细胞瘤是一种死亡率很高的儿童期胚胎性癌症。13-顺式维甲酸（13-cisRA）可提高部分患者的生存率，但许多患者会复发，提示存在临床耐药性。耐药机制和正常分化途径尚不清楚。三氨基酸环延伸（TALE）家族基因是分化的主要调节因子。由于维甲酸可促进神经母细胞瘤的分化，我们评估了神经母细胞瘤中TALE家族基因的表达。
我们评估了TALE家族基因在对维甲酸敏感和耐药的神经母细胞瘤细胞系中的表达，这些细胞系接受或未接受13-顺式维甲酸处理，以确定其表达与维甲酸敏感性相关的基因。我们评估了其中一个基因PBX1在神经母细胞瘤细胞系中的作用，包括增殖和分化。我们通过qRT-PCR评估了原发性人神经母细胞瘤样本中PBX1的表达，并分析了三个独立的临床队列微阵列数据集。
我们证实，在神经母细胞瘤细胞系中，只有PBX1的表达诱导与13-顺式维甲酸反应性相关，其他TALE家族基因则无此关联。在神经母细胞瘤细胞系中外源表达PBX1，模拟诱导的PBX1表达，显著损害增殖和非锚定依赖性生长，并促进维甲酸依赖性和非依赖性分化。PBX1蛋白水平降低产生侵袭性生长表型和维甲酸耐药性。PBX1表达与组织学神经母细胞瘤亚型相关，在良性神经节神经瘤中表达最高，在高危神经母细胞瘤中表达最低。在三个临床队列中，高PBX1表达是生存的预后指标，包括在多变量分析中。
PBX1是神经母细胞瘤分化的重要调节因子，并增强维甲酸诱导的分化。PBX1表达低的神经母细胞瘤细胞和肿瘤具有不成熟的表型，预后较差，与其他风险因素无关。
