School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
Int J Mol Sci. 2021 Mar 24;22(7):3315. doi: 10.3390/ijms22073315.
Chemo-resistance hinders treatment of patients with hepatocellular carcinoma. Although there are many models that can be found in the literature, the root mechanism to explain chemo-resistance is still not fully understood. To gain a better understanding of this phenomenon, a chemo-resistant line, R-HepG2, was developed from a chemo-sensitive HepG2 line through an exposure of doxorubicin (DOX). The R-HepG2 exhibited a cancer stem cell (CSC) phenotype with an over-expression of P-glycoprotein (P-gp), conferring it a significant enhancement in drug efflux and survival. With these observations, we hypothesize that metabolic alteration in this drug-resistant CSC is the root cause of chemo-resistance. Our results show that, unlike other metabolic-reprogrammed CSCs that exhibit glycolytic phenotype described by the "Warburg effect", the R-HepG2 was metabolically quiescent with glucose independence, high metabolic plasticity, and relied on glutamine metabolism via the mitochondria for its chemo-resistance Intriguingly, drug efflux by P-gp in R-HepG2 depended on the mitochondrial ATP fueled by glutamine instead of glycolytic ATP. Armed with these observations, we blocked the glutamine metabolism in the R-HepG2 and a significant reduction of DOX efflux was obtained. We exploited this metabolic vulnerability using a combination of DOX and metformin in a glutamine-free condition to target the R-HepG2, resulting in a significant DOX sensitization. In conclusion, our findings highlight the metabolic modulation of chemo-resistance in CSCs. We delineate the altered metabolism that drives chemo-resistance and offer a new approach to target this CSC through metabolic interventions.
化疗耐药性阻碍了肝细胞癌患者的治疗。尽管文献中有许多模型可以找到，但解释化疗耐药性的根本机制仍未完全了解。为了更好地理解这一现象，我们从化疗敏感的 HepG2 细胞系通过暴露于阿霉素（DOX）中开发了一个化疗耐药系 R-HepG2。R-HepG2 表现出癌症干细胞（CSC）表型，过度表达 P-糖蛋白（P-gp），使其具有显著增强的药物外排和存活能力。有了这些观察结果，我们假设这种耐药性 CSC 中的代谢改变是化疗耐药的根本原因。我们的结果表明，与其他代谢重编程的 CSCs 不同，这些 CSCs 表现出“Warburg 效应”描述的糖酵解表型，R-HepG2 的代谢处于静止状态，对葡萄糖不依赖，具有高代谢可塑性，并通过线粒体依赖谷氨酰胺代谢来抵抗化疗。有趣的是，R-HepG2 中的 P-gp 药物外排依赖于谷氨酰胺提供的线粒体 ATP，而不是糖酵解 ATP。有了这些观察结果，我们在 R-HepG2 中阻断了谷氨酰胺代谢，从而显著减少了 DOX 的外排。我们利用 DOX 和二甲双胍在无谷氨酰胺条件下的联合作用，针对 R-HepG2 的这种代谢脆弱性，从而显著增强了 DOX 的敏感性。总之，我们的研究结果强调了 CSCs 中化疗耐药性的代谢调节。我们描述了驱动化疗耐药性的改变代谢，并提供了一种通过代谢干预靶向这种 CSC 的新方法。
