Bortezomib Causes ER Stress-related Death of Acute Promyelocytic Leukemia Cells Through Excessive Accumulation of PML-RARA.
Bortezomib Causes ER Stress-related Death of Acute Promyelocytic Leukemia Cells Through Excessive Accumulation of PML-RARA.
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发表时间：
2015-06
影响因子：
2
通讯作者：
M. Takenokuchi;K. Miyamoto;K. Saigo;T. Taniguchi
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作者：
M. Takenokuchi;K. Miyamoto;K. Saigo;T. Taniguchi
背景/目的 蛋白酶体抑制剂在治疗多发性骨髓瘤中的成功导致其用于其他恶性肿瘤。对于蛋白酶体抑制剂硼替佐米，与组蛋白脱乙酰酶抑制剂联合治疗可上调泛素蛋白酶体系统 (UPS) 相关酶，产生有益效果。然而，硼替佐米作用的机制尚不完全清楚。我们假设硼替佐米会导致异常蛋白过度积累，从而增加内质网（ER）应激，导致恶性细胞死亡。材料和方法从表达早幼粒细胞白血病/视黄酸受体α（PML-RARA）融合蛋白的急性早幼粒细胞白血病（APL）患者建立的NB4细胞系用于通过蛋白质印迹和免疫沉淀测定评估硼替佐米引起的细胞活力和细胞凋亡的变化，以及PML-RARA和UPS相关酶的变化。结果硼替佐米呈时间和剂量依赖性地降低细胞活力并诱导细胞凋亡。 Bortezomib 显着增加了泛素化 PML-RARA (Ub-PML-RARA)、泛素结合人酶 8 (UbcH8) 和 Ub-UbcH8 的丰度，表明 UbcH8 是 PML-RARA 的 E2 泛素结合酶。此外，硼替佐米处理的细胞的培养上清液中 UbcH8 丰度呈剂量依赖性增加。结论 UbcH8 可能可作为 APL 患者对硼替佐米治疗反应的生物标志物。此外，硼替佐米会导致 PML-RARA 过度积累，增强 ER 应激并导致 APL 细胞死亡，从而损害控制正常蛋白质稳态的 UPS。该研究为将蛋白酶体抑制剂纳入治疗表达异常蛋白的疾病提供了理论依据。此外，监测 UPS 相关酶可能有助于预测蛋白酶体抑制剂的治疗反应并评估其治疗效果。
BACKGROUND/AIM The success of proteasome inhibitors in therapy of multiple myeloma has led to their use for other malignancies. For the proteasome inhibitor bortezomib, combination therapies with histone deacetylase inhibitors, which up-regulate ubiquitin-proteasome system (UPS)-related enzymes, produce a beneficial effect. However, the mechanisms underlying the effect of bortezomib are not completely understood. We hypothesized that bortezomib causes excessive accumulation of aberrant proteins, which augments endoplasmic reticulum (ER) stress, leading to death of malignant cells. MATERIALS AND METHODS The NB4 cell line established from a patient with acute promyelocytic leukemia (APL) expressing the promyelocytic leukemia/retinoic acid receptor alpha (PML-RARA) fusion protein was used to assess changes in cell viability and apoptosis caused by bortezomib, as well as alterations in PML-RARA and UPS-related enzymes via western blotting and immunoprecipitation assays. RESULTS Bortezomib time- and dose-dependently reduced cell viability and induced apoptosis. Bortezomib significantly increased the abundance of ubiquitinated-PML-RARA (Ub-PML-RARA), ubiquitin-conjugating human enzyme 8 (UbcH8), and Ub-UbcH8, indicating that UbcH8 is the E2 ubiquitin-conjugating enzyme for PML-RARA. Moreover, UbcH8 abundance was dose-dependently increased in the culture supernatant of bortezomib-treated cells. CONCLUSION UbcH8 may have a utility as a biomarker of treatment response to bortezomib in patients with APL. Furthermore, bortezomib impairs the UPS that controls normal protein homeostasis by causing excessive accumulation of PML-RARA augmenting ER stress and leading to APL cell death. The study provides a rationale for incorporating proteasome inhibitors in the treatment of diseases expressing aberrant proteins. Furthermore, monitoring of UPS-related enzymes might have use in predicting the treatment response to proteasome inhibitors and in assessing their therapeutic effects.