Division of Experimental Hematology and Cancer Biology, Cancer and Blood Diseases Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA.
State Key Laboratory of Genetic Engineering, Department of Biostatistics and Computational Biology, School of Life Sciences, Fudan University, Shanghai, 200438, China.
Leukemia. 2023 Oct;37(10):2073-2081. doi: 10.1038/s41375-023-01987-w. Epub 2023 Aug 2.
mTOR, as a serine/threonine kinase, is a widely pursued anticancer target. Multiple clinical trials of mTOR kinase inhibitors are ongoing, but their specificity and safety features remain lacking. Here, we have employed an inducible kinase-inactive D2338A mTOR knock-in mouse model (mTOR) together with a mTOR conditional knockout model (mTOR) to assess the kinase-dependent/-independent function of mTOR in hematopoiesis and the on-/off-target effects of mTOR kinase inhibitor AZD2014. Despite exhibiting many similar phenotypes to mTOR mice in hematopoiesis, the mTOR mice survived longer and showed differences in hematopoietic progenitor cells compared to mTOR mice, suggesting a kinase-independent function of mTOR in hematopoiesis. Gene expression signatures in hematopoietic stem cells (HSCs) further revealed both kinase-dependent and independent effects of mTOR. AZD2014, a lead mTOR kinase inhibitor, appeared to work mostly on-target in suppressing mTOR kinase activity, mimicking that of mTOR HSCs in transcriptome analysis, but it also induced a small set of off-target responses in mTOR HSCs. In murine and human myeloid leukemia, besides kinase-inhibitory on-target effects, AZD2014 displayed similar off-target and growth-inhibitory cytostatic effects. These studies provide new insights into kinase-dependent/-independent effects of mTOR in hematopoiesis and present a genetic means for precisely assessing the specificity of mTOR kinase inhibitors.
mTOR 作为一种丝氨酸/苏氨酸激酶，是一个广泛研究的抗癌靶点。目前正在进行多项 mTOR 激酶抑制剂的临床试验，但它们的特异性和安全性特征仍有待提高。在这里，我们使用了一种可诱导的激酶失活 D2338A mTOR 敲入小鼠模型（mTOR）和 mTOR 条件性敲除模型（mTOR）来评估 mTOR 在造血中的激酶依赖性/非依赖性功能，以及 mTOR 激酶抑制剂 AZD2014 的靶内/靶外效应。尽管 mTOR 敲入小鼠在造血方面表现出许多与 mTOR 小鼠相似的表型，但 mTOR 敲入小鼠的存活时间更长，与 mTOR 小鼠相比造血祖细胞存在差异，这表明 mTOR 在造血中具有非激酶依赖性功能。造血干细胞（HSCs）中的基因表达谱进一步揭示了 mTOR 的激酶依赖性和非依赖性效应。AZD2014 是一种领先的 mTOR 激酶抑制剂，在抑制 mTOR 激酶活性方面似乎主要是靶内作用，在转录组分析中模拟了 mTOR HSCs 的作用，但它也在 mTOR HSCs 中诱导了一小部分靶外反应。在鼠类和人类髓性白血病中，除了激酶抑制性的靶内作用外，AZD2014 还显示出类似的靶外和生长抑制细胞毒性作用。这些研究为 mTOR 在造血中的激酶依赖性/非依赖性效应提供了新的见解，并为精确评估 mTOR 激酶抑制剂的特异性提供了一种遗传手段。
