Several myeloid cell leukemia sequence 1 protein (MCL1) inhibitors including S64315 have undergone clinical testing for leukemia. Because of the toxicities after MCL1 inhibition, including hematopoietic, hepatic, and cardiac toxicities, there is substantial interest in finding agents that can sensitize leukemia cells to these MCL1 inhibitors. Melatonin is a chronobiotic that promotes chemo-induced cancer cell death while protecting normal cells from cytotoxic effects. In this study, we found melatonin sensitizes over 10 leukemia cell lines to the MCL1 inhibitors S63845 (S64315 analog) and A-1210477. Further studies demonstrate that melatonin sensitizes Jurkat cells to S63845 and A-1210477 independent of melatonin receptors MT1 and MT2, but through multiple mechanisms, including upregulating the death receptor pathway, increasing mitochondrial reactive oxygen species (ROS), inhibiting nuclear factor-κB (NF-κB) signaling, and causing cell cycle arrest. First, death receptor pathway inhibition only slightly diminishes the melatonin sensitization of S63845, while inhibiting mitochondrial ROS partially reduces the S63845/melatonin combination-induced apoptosis and depletion of the mitochondrial pathway totally abolishes it, indicating that both death receptor and mitochondrial apoptosis pathways are involved. Second, transcriptome sequencing analysis found that NF-κB signaling is downregulated by melatonin that inhibition of NF-κB signaling by parthenolide also dramatically sensitizes Jurkat cells to S63845. Third, melatonin induces G1 cell cycle arrest and upregulates NOXA while NOXA knockdown diminishes the sensitization to S63845 by melatonin. In addition, a xenograft model suggests that melatonin in combination with S63845 causes shrinkage of leukemic deposit while S63845 or melatonin monotherapy only has limited effects. Thus, our results demonstrate that melatonin efficiently sensitizes various leukemia to the MCL1 inhibitors, potentially allowing the usage of lower doses.

中文翻译：

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褪黑素通过多种途径使白血病细胞对 MCL1 抑制剂 S63845 和 A-1210477 敏感

包括 S64315 在内的几种骨髓细胞白血病序列 1 蛋白 (MCL1) 抑制剂已接受针对白血病的临床测试。由于 MCL1 抑制后的毒性，包括造血、肝脏和心脏毒性，人们对寻找能够使白血病细胞对这些 MCL1 抑制剂敏感的药物产生了极大的兴趣。褪黑激素是一种计时生物素，可促进化疗诱导的癌细胞死亡，同时保护正常细胞免受细胞毒性作用。在这项研究中，我们发现褪黑激素使 10 多种白血病细胞系对 MCL1 抑制剂 S63845（S64315 类似物）和 A-1210477 敏感。进一-κB) 信号传导，并导致细胞周期停滞。首先，死亡受体途径抑制仅轻微减弱S63845的褪黑激素敏感性，而抑制线粒体ROS部分减少S63845/褪黑激素组合诱导的细胞凋亡，而线粒体途径的耗尽则完全消除它，表明死亡受体和线粒体凋亡途径都参与其中。其次，转录组测序分析发现，褪黑激素下调 NF-κB 信号传导，小白菊内酯抑制 NF-κB 信号传导也会显着提高 Jurkat 细胞对 S63845 的敏感性。第三，褪黑素诱导 G1 细胞周期停滞并上调 NOXA，而 NOXA 敲低则降低褪黑素对 S63845 的敏感性。此外，异种移植模型表明，褪黑激素与 S63845 联合使用可导致白血病沉积物缩小，而 S63845 或褪黑激素单一疗法的效果有限。因此，我们的结果表明，褪黑激素有效地使各种白血病对 MCL1 抑制剂敏感，可能允许使用较低剂量。