Department of Pediatric Hematology/Oncology, Laura and Isaac Perlmutter Cancer Center at New York University Langone Medical Center, New York, New York.
Pediatr Blood Cancer. 2014 Oct;61(10):1779-85. doi: 10.1002/pbc.25119. Epub 2014 Jun 29.
Ikaros, the product of IKZF1, is a regulator of lymphoid development and polymorphisms in the gene have been associated with the acute lymphoblastic leukemia (ALL). Additionally, IKZF1 deletions and mutations identify high-risk biological subsets of childhood ALL [Georgopoulos et al. Cell 1995;83(2):289-299; Mullighan et al. N Engl J Md 2009;360(5):470-480].
To discover the underlying pathways modulated by Ikaros we performed gene expression and gene ontology analysis in IKZF1 deleted primary B-ALL pediatric patient samples. To validate downstream targets we performed qPCR on individual patient samples. We also created IKZF1 knockdown B-ALL cell lines with over 50% reduction of Ikaros, mimicking haplosufficient Ikaros deletions, and again performed qPCR to investigate the downstream targets. Finally, to understand the association of Ikaros deletion with a poor prognosis we challenged our IKZF1 knockdown cell lines with chemotherapy and compared responses to IKZF1 wild-type controls.
We report a specific gene expression signature of 735 up-regulated and 473 down-regulated genes in IKZF1 deleted primary B-ALL pediatric patient samples. Gene ontology studies revealed an up-regulation of genes associated with cell adhesion, cytoskeletal regulation, and motility in IKZF deleted patient samples. Validated up-regulated target genes in IKZF1 deleted patient samples included CTNND1 and PVRL2 (P = 0.0003 and P = 0.001), and RAB3IP and SPIB (P = 0.005 and P = 0.032) were down-regulated. In further studies in IKZF1 knockdown cell lines, apoptosis assays showed no significant chemoresistance.
IKZF1 knockdown alone does not impart intrinsic chemotherapy resistance suggesting that the association with a poor prognosis may be due to additional lesions, microenvironmental interactions with the bone marrow niche, or other factors.
Ikaros 是 IKZF1 的产物，是淋巴样发育的调节剂，该基因的多态性与急性淋巴细胞白血病（ALL）有关。此外，IKZF1 缺失和突变确定了儿童 ALL 的高风险生物学亚群[Georgopoulos 等人，细胞 1995；83（2）：289-299；Mullighan 等人，新英格兰医学杂志 2009；360（5）：470-480]。
为了发现 Ikaros 调节的潜在途径，我们对 IKZF1 缺失的原发性 B-ALL 儿科患者样本进行了基因表达和基因本体分析。为了验证下游靶标，我们对单个患者样本进行了 qPCR。我们还创建了 IKZF1 敲低的 B-ALL 细胞系，Ikaros 减少了 50%以上，模拟 haplosufficient Ikaros 缺失，并再次进行 qPCR 以研究下游靶标。最后，为了了解 Ikaros 缺失与预后不良的关联，我们用化疗挑战我们的 IKZF1 敲低细胞系，并将其与 IKZF1 野生型对照进行比较。
我们报告了 IKZF1 缺失的原发性 B-ALL 儿科患者样本中 735 个上调和 473 个下调基因的特定基因表达谱。基因本体研究显示，IKZF 删除患者样本中与细胞黏附、细胞骨架调节和运动相关的基因上调。在 IKZF1 缺失的患者样本中验证的上调靶基因包括 CTNND1 和 PVRL2（P=0.0003 和 P=0.001），以及 RAB3IP 和 SPIB（P=0.005 和 P=0.032）下调。在 IKZF1 敲低细胞系的进一步研究中，凋亡试验显示没有明显的化疗耐药性。
单独的 IKZF1 敲低不会赋予内在的化疗耐药性，这表明与预后不良的关联可能是由于其他病变、与骨髓龛的微环境相互作用或其他因素。
