Artemisinin and its derivatives (ARTs) were reported to display heme-dependent antitumor activity. On the other hand, histone deacetylase inhibitors (HDACi) were known to be able to promote heme synthesis in erythroid cells. Nevertheless, the effect of HDACi on heme homeostasis in non-erythrocytes remains unknown. We envisioned that the combination of HDACi and artesunate (ARS) might have synergistic antitumor activity through modulating heme synthesis. In vitro studies revealed that combination of ARS and HDACi exerted synergistic tumor inhibition by inducing cell death. Moreover, this combination exhibited more effective antitumor activity than either ARS or HDACi monotherapy in xenograft models without apparent toxicity. Importantly, mechanistic studies revealed that HDACi coordinated with ARS to increase 5-aminolevulinate synthase (ALAS1) expression, and subsequent heme production, leading to enhanced cytotoxicity of ARS. Notably, knocking down ALAS1 significantly blunted the synergistic effect of ARS and HDACi on tumor inhibition, indicating a critical role of ALAS1 upregulation in mediating ARS cytotoxicity. Collectively, our study revealed the mechanism of synergistic antitumor action of ARS and HDACi. This finding indicates that modulation of heme synthesis pathway by the combination based on ARTs and other heme synthesis modulators represents a promising therapeutic approach to solid tumors.

据报道，青蒿素及其衍生物（ART）具有血红素依赖性抗肿瘤活性。另一方面，已知组蛋白脱乙酰酶抑制剂（HDACi）能够促进红细胞中血红素的合成。然而，HDACi 对非红细胞血红素稳态的影响仍不清楚。我们设想 HDACi 和青蒿琥酯 (ARS) 的组合可能通过调节血红素合成具有协同抗肿瘤活性。体外研究表明，ARS 和 HDACi 组合通过诱导细胞死亡发挥协同肿瘤抑制作用。此外，在异种移植模型中，这种组合比 ARS 或 HDACi 单一疗法表现出更有效的抗肿瘤活性，且没有明显毒性。重要的是，机制研究表明，HDACi 与 ARS 协同增加 5-氨基乙酰丙酸合酶 (ALAS1) 的表达以及随后的血红素产生，从而增强 ARS 的细胞毒性。值得注意的是，敲低ALAS1显着削弱了 ARS 和 HDACi 对肿瘤抑制的协同作用，表明 ALAS1 上调在介导 ARS 细胞毒性中发挥着关键作用。总的来说，我们的研究揭示了 ARS 和 HDACi 协同抗肿瘤作用的机制。这一发现表明，通过基于 ART 和其他血红素合成调节剂的组合来调节血红素合成途径代表了一种有前途的实体瘤治疗方法。