急性髓系白血病（AML）是一组异质性血液恶性肿瘤，其特征是分化停滞、复发率高和生存率低。骨髓 (BM) 微环境被认为是耐药性的关键介质，也是导致 AML 复发的主要部位。我们之前的研究报道，5-氨基咪唑-4-甲酰胺核糖核苷 (AICAr) 通过抑制嘧啶合成和激活检查点激酶 1 来诱导 AML 细胞分化。虽然 BM 基质对白血病细胞响应细胞毒性药物的保护作用已有充分记录，其对 AML 分化的影响仍鲜有研究。在这项研究中，我们研究了基质细胞系和原代间充质基质细胞 (MSC) 对 AICAr 和 brequinar（一种已知的二氢乳清酸脱氢酶 (DHODH) 抑制剂）触发的 AML 细胞系分化的影响。我们的研究结果表明，以其细胞保护作用而闻名的小鼠 MS-5 基质细胞系不会抑制嘧啶合成抑制剂诱导的 AML 细胞分化。有趣的是，AICAr 通过 AMPK 依赖性途径引起 MS-5 基质细胞的形态变化和生长停滞。与小鼠细胞相比，人基质细胞系 HS-5 和 HS-27 以及从患者骨髓中分离的原代 MSC 在促进 AML 分化方面优于小鼠细胞，对 AICAr 和布喹那的反应更佳，且抑制剂不会显着影响基质细胞本身。总之，我们的研究强调了人骨髓间充质干细胞在增强嘧啶合成​​抑制剂对 AML 细胞的分化作用方面的支持作用，表明专注于分化而不是细胞杀伤的 AML 治疗策略可能在临床环境中取得成功。

Acute myeloid leukemia (AML) is a heterogeneous group of hematologic malignancies characterized by differentiation arrest, high relapse rates, and poor survival. The bone marrow (BM) microenvironment is recognized as a critical mediator of drug resistance and a primary site responsible for AML relapse. Our previous study reported that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAr) induces AML cell differentiation by inhibiting pyrimidine synthesis and activating Checkpoint kinase 1. While the protective effect of BM stroma on leukemia cells in response to cytotoxic drugs is well-documented, its effect on AML differentiation remains less explored. In this study, we investigated the impact of stromal cell lines and primary mesenchymal stromal cells (MSCs) on AML cell line differentiation triggered by AICAr and brequinar, a known dihydroorotate dehydrogenase (DHODH) inhibitor. Our findings indicate that the mouse MS-5 stromal cell line, known for its cytoprotective effects, does not inhibit AML cell differentiation induced by pyrimidine synthesis inhibitors. Interestingly, AICAr caused morphological changes and growth arrest in MS-5 stromal cells via an AMPK-dependent pathway. Human stromal cell lines HS-5 and HS-27, as well as primary MSCs isolated from patient bone marrow, were superior in promoting AML differentiation compared to mouse cells in response to AICAr and brequinar, with the inhibitors not significantly affecting the stromal cells themselves. In conclusion, our study highlights the supportive role of human BM MSCs in enhancing the differentiation effects of pyrimidine synthesis inhibitors on AML cells, suggesting that AML treatment strategies focusing on differentiation rather than cell killing may be successful in clinical settings.