A gain-of-function p53 mutant synergizes with oncogenic Nras to promote acute myeloid leukemia in mice

We previously demonstrated that a subset of acute myeloid leukemia (AML) patients with concurrent RAS pathway and TP53 mutations have extremely poor prognosis, and most of these TP53 mutations are missense mutations. Here, we report that in contrast to mixed AML and T-cell malignancy developed in NrasG12D/+; p53-/- (NP-/-) mice, NrasG12D/+; p53R172H/+ (NPmut) mice rapidly developed an inflammation-associated AML. Under the inflammatory conditions, NPmut hematopoietic stem and progenitor cells (HSPCs) displayed imbalanced myelopoiesis and lymphopoiesis and largely normal cell proliferation despite MEK/ERK hyperactivation. RNA-Seq analysis revealed that NrasG12D signaling and p53mut synergize to establish an NPmut-AML transcriptome distinct from that of NA-/- cells. The NPmut-AML transcriptome showed GATA2 downregulation and elevated expression of inflammatory genes, including those linked to NFΚB signaling. NFΚB was also upregulated in human NRAS;TP53 AML. Exogenous expression of GATA2 in human NPmut KY821 AML cells downregulated inflammatory gene expression. Mouse and human NPmut AML cells were sensitive to MEK and NFΚB inhibition in vitro. The proteasome inhibitor bortezomib stabilized NFΚB inhibitory protein IΚBɑ mitigated inflammatory gene expression, and potentiated the survival benefit of a MEK inhibitor in NPmut mice. Our study demonstrates that a p53 structural mutant synergizes with NrasG12D to promote AML through mechanisms distinct from p53 loss. To investigate how mutant p53 cooperates with oncogenic Nras to promote leukemogenesis, we performed RNA-Seq with sorted Lin- cKit+ bone marrow HSPCs from moribund double mutant [NPmut] (n=4) as well as poly I:C treated, age-matched control (n=3), p53 mutant (n=3), and oncogenic Nras (n=3) mice.

我们此前已有研究证实，伴发RAS通路（RAS pathway）与TP53突变的急性髓系白血病（acute myeloid leukemia, AML）患者亚群预后极差，且此类TP53突变大多为错义突变。本文报道，与NrasG12D/+；p53全敲除（NrasG12D/+; p53-/-，简称NP-/-）小鼠中出现的混合性AML与T细胞恶性肿瘤不同，NrasG12D/+；p53R172H/+（简称NPmut）小鼠会快速罹患炎症相关性AML。在炎症条件下，NPmut小鼠的造血干祖细胞（hematopoietic stem and progenitor cells, HSPCs）表现出髓系与淋系生成失衡，尽管MEK/ERK通路存在过度激活，但细胞增殖基本维持正常。RNA测序（RNA-Seq）分析显示，NrasG12D信号与突变型p53协同作用，可形成与NP-/-细胞截然不同的NPmut-AML转录组特征。NPmut-AML转录组表现为GATA结合蛋白2（GATA2）表达下调，以及包括核因子κB（NF-κB）相关信号通路基因在内的炎症基因表达升高。在人类NRAS；TP53突变AML样本中，核因子κB通路同样存在上调现象。在人类NPmut型AML细胞系KY821中外源过表达GATA2，可下调炎症基因的表达。小鼠与人类NPmut AML细胞在体外对MEK与NF-κB抑制剂均敏感。蛋白酶体抑制剂硼替佐米（bortezomib）可稳定核因子κB抑制蛋白IκBα，减轻炎症基因的表达，并增强MEK抑制剂对NPmut小鼠的生存获益。本研究证实，一种结构突变型p53可与NrasG12D协同，通过不同于p53缺失的机制促进AML发生。为探究突变型p53与致癌性Nras如何协同促进白血病发生，我们对终末期双突变[NPmut]小鼠（n=4）以及经聚肌胞苷酸（poly I:C）处理的同龄对照小鼠（n=3）、p53突变小鼠（n=3）、致癌性Nras小鼠（n=3）的分选Lin阴性、cKit阳性骨髓造血干祖细胞进行了RNA测序。