Program in Neuroscience, University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences , Houston , TX , USA.
Department of Neurobiology and Anatomy, McGovern Medical School , Houston , TX , USA.
Cancer Biol Ther. 2019;20(12):1416-1429. doi: 10.1080/15384047.2019.1647049. Epub 2019 Sep 1.
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.
神经母细胞瘤是婴儿中最常见的恶性肿瘤。表皮生长因子受体（EGFR）在神经母细胞瘤肿瘤中的过度表达是导致对化疗药物产生耐药性的基础。UBE4B 是一种参与 EGFR 降解的 E3/E4 泛素连接酶，位于染色体 1p36 上，在大约三分之一的神经母细胞瘤肿瘤中观察到该区域杂合性丢失，并且与预后不良相关。在化疗耐药的神经母细胞瘤细胞中，UBE4B 的耗竭导致细胞增殖和迁移显著减少，并增强了对 EGFR 抑制剂西妥昔单抗的细胞凋亡。我们之前已经表明，UBE4B 的水平与神经母细胞瘤肿瘤中的 EGFR 水平呈负相关。我们使用反相蛋白阵列搜索了在 UBE4B 耗尽的化疗耐药神经母细胞瘤细胞中与肿瘤发生相关的细胞变化的其他 UBE4B 靶标。在没有 UBE4B 的情况下，EGFR 下游效应蛋白 STAT5a 的表达增加了一倍，并通过定量免疫印迹进行了验证。用 STAT5 抑制剂 SH-4-54 处理化疗耐药的神经母细胞瘤细胞，观察到对细胞增殖、迁移和凋亡的影响不明显。然而，SH-4-54 显著增强了西妥昔单抗在幼稚 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 显著增强了西妥昔单抗的作用，使细胞对原本效果不佳的西妥昔单抗浓度更加敏感。因此，UBE4B 水平较低的神经母细胞瘤细胞对 EGFR 和 STAT5 联合抑制的敏感性明显高于亲本细胞。这些发现可能对具有 1p36 染色体 LOH 和肿瘤 UBE4B 表达低的患者具有潜在的治疗意义。
