Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
Department of Blood Transfusion, the Third Xiangya Hospital, Central South University, Changsha, 410013, China.
Theranostics. 2022 Mar 21;12(6):2894-2907. doi: 10.7150/thno.67710. eCollection 2022.
The endoplasmic reticulum unfolded protein response (UPR) is a conserved adaptive signaling in ER homeostasis and has emerged as critical in highly proliferating cells and potential treatment target for acute T-cell lymphoblastic leukemia (T-ALL). in this study, we assessed the transcriptomic and phenotypic alterations in UPR response of the bone marrow endothelial cells (ECs) in mice engrafted with T-ALL and in bone marrow specimens from patients who have T-ALL. We used PERK inhibitor and generated endothelial specific PERK knockout mice to study the impact of PERK on leukemia progression and hematopoiesis. We performed chromatin immunoprecipitation (ChIP) to study the mechanistic regulation of JAG1 by ATF4. We characterized small extracellular vesicles (SEV) from leukemia-developing mice and studied the effect of SEVs on EC function. we found that T-ALL development induced a robust activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dominant UPR in the bone marrow endothelial vascular niche. The activation of PERK-eIF2a-ATF4 axis remodels the vascular niche, upregulates angiogenic factors including VEGFα and ATF4-regulated JAG1, and suppresses the expression of SCF and CXCL12, which are important to HSC maintenance and regeneration. Further, targeting endothelial PERK significantly improved T-ALL outcome. EC-specific deletion of PERK abolished the aberrant JAG1 up-regulation, improved HSC maintenance, promoted leukemia apoptosis, and improved overall survival. Finally, we showed that small extracellular vesicles are critical mediators of endothelial PERK-eIF2a-ATF4 activation and JAG1 up-regulation in leukemia. Corroborating animal model studies, activation of PERK-ATF4-JAG1 is prominent in human T-ALL bone marrow and T-ALL xenografts. our studies thus revealed for the first time that the leukemia-initiated PERK-ATF4-JAG1 axis plays a critical role in the remodeling of the bone marrow vascular niche and that targeting vascular niche UPR is a potential therapeutic opportunity in T-ALL.
内质网未折叠蛋白反应（UPR）是内质网稳态的一种保守适应性信号转导，已成为高度增殖细胞的关键因素，并可能成为急性 T 细胞淋巴细胞白血病（T-ALL）的潜在治疗靶点。在这项研究中，我们评估了骨髓内皮细胞（EC）中 UPR 反应的转录组和表型改变，这些细胞在患有 T-ALL 的小鼠和患有 T-ALL 的患者的骨髓标本中进行了移植。我们使用 PERK 抑制剂并生成内皮细胞特异性 PERK 敲除小鼠，以研究 PERK 对白血病进展和造血的影响。我们进行了染色质免疫沉淀（ChIP）实验，以研究 ATF4 对 JAG1 的机制调节。我们对来自白血病发展小鼠的小细胞外囊泡（SEV）进行了特征描述，并研究了 SEV 对 EC 功能的影响。我们发现，T-ALL 的发展诱导了骨髓内皮血管龛中蛋白激酶 RNA 样内质网激酶（PERK）主导的 UPR 的强烈激活。PERK-eIF2a-ATF4 轴的激活重塑了血管龛，上调了血管生成因子，包括 VEGFα 和 ATF4 调节的 JAG1，并抑制了干细胞因子（SCF）和 CXCL12 的表达，这对于 HSC 的维持和再生很重要。此外，针对内皮 PERK 的治疗显著改善了 T-ALL 的结果。内皮细胞特异性 PERK 缺失消除了异常的 JAG1 上调，改善了 HSC 的维持，促进了白血病细胞凋亡，并提高了总生存率。最后，我们表明，小细胞外囊泡是内皮 PERK-eIF2a-ATF4 激活和白血病中 JAG1 上调的关键介质。与动物模型研究相吻合，PERK-ATF4-JAG1 的激活在人类 T-ALL 骨髓和 T-ALL 异种移植中非常明显。我们的研究首次揭示了白血病起始的 PERK-ATF4-JAG1 轴在骨髓血管龛重塑中起着关键作用，靶向血管龛 UPR 是 T-ALL 的潜在治疗机会。
