Fisher-Wellman Kelsey H, Kassai Miki, Hagen James T, Neufer P Darrell, Kester Mark, Loughran Thomas P, Chalfant Charles E, Feith David J, Tan Su-Fern, Fox Todd E, Ung Johnson, Fabrias Gemma, Abad Jose' Luis, Sharma Arati, Golla Upendarrao, Claxton David F, Shaw Jeremy J P, Bhowmick Debajit, Cabot Myles C
Department of Integrative Physiology and Metabolism, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA.
East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27858, USA.
Cancers (Basel). 2023 Mar 21;15(6):1883. doi: 10.3390/cancers15061883.
Acute myelogenous leukemia (AML), the most prevalent acute and aggressive leukemia diagnosed in adults, often recurs as a difficult-to-treat, chemotherapy-resistant disease. Because chemotherapy resistance is a major obstacle to successful treatment, novel therapeutic intervention is needed. Upregulated ceramide clearance via accelerated hydrolysis and glycosylation has been shown to be an element in chemotherapy-resistant AML, a problem considering the crucial role ceramide plays in eliciting apoptosis. Herein we employed agents that block ceramide clearance to determine if such a "reset" would be of therapeutic benefit. SACLAC was utilized to limit ceramide hydrolysis, and D--1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D--PDMP) was used to block the glycosylation route. The SACLAC D--PDMP inhibitor combination was synergistically cytotoxic in drug-resistant, P-glycoprotein-expressing (P-gp) AML but not in wt, P-gp-poor cells. Interestingly, P-gp antagonists that can limit ceramide glycosylation via depression of glucosylceramide transit also synergized with SACLAC, suggesting a paradoxical role for P-gp in the implementation of cell death. Mechanistically, cell death was accompanied by a complete drop in ceramide glycosylation, concomitant, striking increases in all molecular species of ceramide, diminished sphingosine 1-phosphate levels, resounding declines in mitochondrial respiratory kinetics, altered Akt, pGSK-3β, and Mcl-1 expression, and caspase activation. Although ceramide was generated in wt cells upon inhibitor exposure, mitochondrial respiration was not corrupted, suggestive of mitochondrial vulnerability in the drug-resistant phenotype, a potential therapeutic avenue. The inhibitor regimen showed efficacy in an in vivo model and in primary AML cells from patients. These results support the implementation of SL enzyme targeting to limit ceramide clearance as a therapeutic strategy in chemotherapy-resistant AML, inclusive of a novel indication for the use of P-gp antagonists.
急性髓性白血病（AML）是成人中最常见的急性侵袭性白血病，常复发为难治性、化疗耐药性疾病。由于化疗耐药是成功治疗的主要障碍，因此需要新的治疗干预措施。通过加速水解和糖基化上调神经酰胺清除率已被证明是化疗耐药性AML中的一个因素，鉴于神经酰胺在引发细胞凋亡中起关键作用，这是一个问题。在此，我们使用阻断神经酰胺清除的药物来确定这种“重置”是否具有治疗益处。使用SACLAC来限制神经酰胺水解，并使用D- -1-苯基-2-癸酰氨基-3-吗啉代-1-丙醇（D- -PDMP）来阻断糖基化途径。SACLAC与D- -PDMP抑制剂组合在耐药、表达P-糖蛋白（P-gp）的AML中具有协同细胞毒性，但在野生型、P-gp表达少的细胞中则没有。有趣的是，能够通过抑制葡糖神经酰胺转运来限制神经酰胺糖基化的P-gp拮抗剂也与SACLAC协同作用，这表明P-gp在细胞死亡过程中具有矛盾的作用。从机制上讲，细胞死亡伴随着神经酰胺糖基化的完全下降，同时，所有神经酰胺分子种类显著增加，1-磷酸鞘氨醇水平降低，线粒体呼吸动力学显著下降，Akt、pGSK-3β和Mcl-1表达改变，以及半胱天冬酶激活。尽管在野生型细胞中暴露于抑制剂时会产生神经酰胺，但线粒体呼吸并未受损，这表明耐药表型中线粒体易损性是一种潜在的治疗途径。该抑制剂方案在体内模型和患者的原发性AML细胞中显示出疗效。这些结果支持将靶向鞘脂酶以限制神经酰胺清除作为化疗耐药性AML的治疗策略，包括P-gp拮抗剂使用的新适应症。
