Erythropoiesis is a crucial process in hematopoiesis, yet it remains highly susceptible to disruption by various diseases, which significantly contribute to the global challenges of anemia and blood shortages. Current treatments like erythropoietin (EPO) or glucocorticoids often fall short, especially for hereditary anemias such as Diamond-Blackfan anemia (DBA). To uncover new erythropoiesis-stimulating agents, we devised a screening system using primary human hematopoietic stem and progenitor cells (HSPCs). We discovered that BRAF inhibitors (BRAFi), commonly used to treat BRAF^V600E melanoma, can unexpectedly and effectively promote progenitor cell proliferation by temporarily delaying erythroid differentiation. Notably, these inhibitors exhibited pronounced efficacy even under cytokine-restricted conditions and in patient samples of DBA. Mechanistically, although these BRAFi inhibit the MAPK cascade in BRAF^V600E mutant cells, they paradoxically act as amplifiers in wild-type BRAF cells, potently enhancing the cascade. Furthermore, we found that while the oncogenic BRAF^V600E mutation disrupts hematopoiesis and erythropoiesis through AP-1 hyperactivation, BRAFi minimally impact HSPC self-renewal and differentiation. In vivo studies have shown that BRAFi can enhance human hematopoiesis and erythropoiesis in severe immunodeficient mouse models and alleviate anemia in the Rpl11 haploinsufficiency DBA model, as well as other relevant anemia models. This discovery underscores the role of the MAPK pathway in hematopoiesis and positions BRAFi as a promising therapeutic option for improving hematopoietic reconstitution and treating anemias, including DBA.

红细胞生成是造血的关键过程，但它仍然极易受到各种疾病的破坏，这极大地加剧了贫血和血液短缺的全球挑战。目前的治疗方法，如促红细胞生成素 （EPO） 或糖皮质激素，往往达不到要求，尤其是对于遗传性贫血，如 Diamond-Blackfan 贫血 （DBA）。为了发现新的红细胞生成刺激剂，我们设计了一个使用原代人类造血干细胞和祖细胞 （HSPC） 的筛选系统。我们发现，常用于治疗 BRAF^V600E 黑色素瘤的 BRAF 抑制剂 （BRAFi） 可以通过暂时延迟红细胞分化来意外有效地促进祖细胞增殖。值得注意的是，即使在细胞因子限制的条件下和 DBA 患者样本中，这些抑制剂也表现出显着的疗效。从机制上讲，尽管这些 BRAFi 抑制了 BRAF^V600E 突变细胞中的 MAPK 级联反应，但它们在野生型 BRAF 细胞中反常地充当放大器，有效地增强了级联反应。此外，我们发现虽然致癌 BRAF^V600E 突变通过 AP-1 过度激活破坏造血和红细胞生成，但 BRAFi 对 HSPC 自我更新和分化的影响最小。体内研究表明，BRAFi 可以增强严重免疫缺陷小鼠模型中的人类造血和红细胞生成，并减轻 Rpl11 单倍体不足 DBA 模型以及其他相关贫血模型中的贫血。这一发现强调了 MAPK 通路在造血中的作用，并将 BRAFi 定位为改善造血重建和治疗贫血（包括 DBA）的有前途的治疗选择。