Neuroblastoma is the most common malignancy in infants. Overexpression of the epidermal growth factor receptor (EGFR) in neuroblastoma tumors underlies resistance to chemotherapeutics. UBE4B, an E3/E4 ubiquitin ligase involved in EGFR degradation, is located on chromosome 1p36, a region in which loss of heterozygosity is observed in approximately one-third of neuroblastoma tumors and is correlated with poor prognosis. In chemoresistant neuroblastoma cells, depletion of UBE4B yielded significantly reduced cell proliferation and migration, and enhanced apoptosis in response to EGFR inhibitor, Cetuximab. We have previously shown that UBE4B levels are inversely correlated with EGFR levels in neuroblastoma tumors. We searched for additional targets of UBE4B that mediate cellular alterations associated with tumorogenesis in chemoresistant neuroblastoma cells depleted of UBE4B using reverse phase protein arrays. The expression of STAT5a, an effector protein downstream of EGFR, doubled in the absence of UBE4B, and verified by quantitative immunoblotting. Chemoresistant neuroblastoma cells were treated with SH-4-54, a STAT5 inhibitor, and observed insignificant effects on cell proliferation, migration, and apoptosis. However, SH-4-54 significantly enhanced the anti-proliferative and anti-migratory effects of Cetuximab in naïve SK-N-AS neuroblastoma cells. Interestingly, in UBE4B depleted SK-N-AS cells, SH-4-54 significantly potentiated the effect of Cetuximab rendering cells increasingly sensitive an otherwise minimally effective Cetuximab concentration. Thus, neuroblastoma cells with low UBE4B levels were significantly more sensitive to combined EGFR and STAT5 inhibition than parental cells. These findings may have potential therapeutic implications for patients with 1p36 chromosome LOH and low tumor UBE4B expression.

中文翻译：

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UBE4B的低表达增加了化学耐药性神经母细胞瘤细胞对EGFR和STAT5抑制的敏感性。

神经母细胞瘤是婴儿中最常见的恶性肿瘤。在神经母细胞瘤肿瘤中表皮生长因子受体（EGFR）的过表达是对化学治疗药物耐药的基础。UBE4B是一种参与EGFR降解的E3 / E4泛素连接酶，位于1p36号染色体上，该区域在大约三分之一的神经母细胞瘤肿瘤中观察到杂合性丧失，并与不良预后相关。在化学耐药性神经母细胞瘤细胞中，UBE4B的消耗明显减少了细胞的增殖和迁移，并增强了对EGFR抑制剂西妥昔单抗的响应。先前我们已经证明，在神经母细胞瘤肿瘤中，UBE4B水平与EGFR水平成反比。我们搜索了UBE4B的其他目标，这些目标介导与UBE4B耗尽的化学耐药性神经母细胞瘤细胞中使用反相蛋白阵列介导的肿瘤发生相关的细胞改变。STAT5a（EGFR下游的效应蛋白）的表达在不存在UBE4B的情况下增加了一倍，并通过定量免疫印迹进行了验证。化疗耐药的神经母细胞瘤细胞用STAT5抑制剂SH-4-54处理，观察到对细胞增殖，迁移和凋亡的影响不明显。然而，SH-4-54显着增强了西妥昔单抗在未用过的SK-N-AS神经母细胞瘤细胞中的抗增殖和抗迁移作用。有趣的是，在UBE4B耗尽的SK-N-AS细胞中，SH-4-54显着增强了西妥昔单抗的作用，从而使细胞对本来最小有效的西妥昔单抗浓度变得越来越敏感。从而，UBE4B水平低的成神经细胞瘤细胞对EGFR和STAT5联合抑制作用的敏感性明显高于亲代细胞。这些发现可能对具有1p36染色体LOH和低肿瘤UBE4B表达的患者具有潜在的治疗意义。