Hematology Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1202, USA.
Int J Oncol. 2018 Apr;52(4):1209-1223. doi: 10.3892/ijo.2018.4290. Epub 2018 Feb 28.
Additional sex combs-like 1 (ASXL1) is a well‑known tumor suppressor gene and epigenetic modifier. ASXL1 mutations are frequent in myeloid malignances; these mutations are risk factors for the development of myelodysplasia and also appear as small clones during normal aging. ASXL1 appears to act as an epigenetic regulator of cell survival and myeloid differentiation; however, the molecular mechanisms underlying the malignant transformation of cells with ASXL1 mutations are not well defined. Using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein-9 nuclease (Cas9) genome editing, heterozygous and homozygous ASXL1 mutations were introduced into human U937 leukemic cells. Comparable cell growth and cell cycle progression were observed between wild-type (WT) and ASXL1-mutated U937 cells. Drug-induced cytotoxicity, as measured by growth inhibition and apoptosis in the presence of the cell-cycle active agent 5-fluorouracil, was variable among the mutated clones but was not significantly different from WT cells. In addition, ASXL1-mutated cells exhibited defects in monocyte/macrophage differentiation. Transcriptome analysis revealed that ASXL1 mutations altered differentiation of U937 cells by disturbing genes involved in myeloid differentiation, including cytochrome B-245 β chain and C-type lectin domain family 5, member A. Dysregulation of numerous gene sets associated with cell death and survival were also observed in ASXL1-mutated cells. These data provide evidence regarding the underlying molecular mechanisms induced by mutated ASXL1 in leukemogenesis.
额外的性梳状结构 1（ASXL1）是一种已知的肿瘤抑制基因和表观遗传修饰物。ASXL1 突变在髓系恶性肿瘤中很常见；这些突变是骨髓增生异常和正常衰老过程中出现小克隆的风险因素。ASXL1 似乎作为细胞存活和髓系分化的表观遗传调节剂发挥作用；然而，ASXL1 突变细胞恶性转化的分子机制尚不清楚。使用成簇规律间隔短回文重复（CRISPR）/CRISPR 相关蛋白-9 核酸酶（Cas9）基因组编辑，将杂合和纯合 ASXL1 突变引入人 U937 白血病细胞中。在野生型（WT）和 ASXL1 突变的 U937 细胞之间观察到相似的细胞生长和细胞周期进程。在细胞周期活性药物 5-氟尿嘧啶存在的情况下，药物诱导的细胞毒性（通过生长抑制和凋亡来衡量）在突变克隆之间是可变的，但与 WT 细胞没有显著差异。此外，ASXL1 突变细胞表现出单核细胞/巨噬细胞分化缺陷。转录组分析显示，ASXL1 突变通过扰乱涉及髓系分化的基因，包括细胞色素 B-245β 链和 C 型凝集素结构域家族 5 成员 A，改变了 U937 细胞的分化。在 ASXL1 突变细胞中还观察到与细胞死亡和存活相关的许多基因集的失调。这些数据提供了关于 ASXL1 突变在白血病发生中诱导的潜在分子机制的证据。
