Koh King Xin, Tan Gim Hwa, Hui Low Sarah Hong, Mohd Omar Mohd Feroz, Han Min Ji, Iacopetta Barry, Soo Ross, Beloueche-Babari Mounia, Bhattacharya Bhaskar, Soong Richie
Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore.
Department of Haematology Oncology, National University Cancer Institute of Singapore, Singapore, Singapore.
Oncotarget. 2017 Nov 24;8(66):110133-110144. doi: 10.18632/oncotarget.22655. eCollection 2017 Dec 15.
Acquired resistance (AQR) to drug treatment occurs frequently in cancer patients and remains an impediment to successful therapy. The aim of this study was to gain insight into how AQR arises following the application of PI3K/mTOR inhibitors. H1975 lung cancer cells with EGFR T790M mutations that confer resistance to EGFR inhibitors underwent prolonged treatment with the PI3K/mTOR inhibitor, BEZ235. Monoclonal cells with stable and increased resistance to BEZ235 were obtained after 8 months treatment. These AQR clones showed class-specific resistance to PI3K/mTOR inhibitors, reduced G1 cell cycle arrest and impedance of migration following PI3K/mTOR inhibition, reduced PTEN expression and increased Akt and S6RP phosphorylation. Transcriptome analysis revealed the AQR clones had increased expression of the metabolite transporters SLC16A9 and SLC16A7, suggestive of altered cell metabolism. Subsequent experiments revealed that AQR clones possess features consistent with elevated glycolysis, including increased levels of glucose, lactate, glutamine, glucose dependence, GLUT1 expression, and rates of post-glucose extracellular acidification, and decreased levels of reactive oxygen species and rates of oxygen consumption. Combination treatment of BEZ235 with the glycolysis inhibitor 3-bromopyruvate was synergistic in AQR clones, but only additive in parental cells. DNA sequencing revealed the presence of a mitochondrial DNA (mtDNA) MT-C01 variant in AQR but not parental cells. Depletion of mitochondrial DNA in parental cells induced resistance to BEZ235 and other PI3K/mTOR inhibitors, and was accompanied by increased glycolysis. The results of this study provide the first evidence that a metabolic switch associated with mtDNA mutation can be an underlying mechanism for AQR.
癌症患者中经常会出现对药物治疗的获得性耐药（AQR），这仍然是成功治疗的一个障碍。本研究的目的是深入了解PI3K/mTOR抑制剂应用后AQR是如何产生的。对EGFR抑制剂耐药的具有EGFR T790M突变的H1975肺癌细胞接受了PI3K/mTOR抑制剂BEZ235的长期治疗。经过8个月的治疗后，获得了对BEZ235具有稳定且增强耐药性的单克隆细胞。这些AQR克隆对PI3K/mTOR抑制剂表现出类别特异性耐药，PI3K/mTOR抑制后G1期细胞周期停滞减少且迁移受到阻碍，PTEN表达降低，Akt和S6RP磷酸化增加。转录组分析显示，AQR克隆中代谢物转运蛋白SLC16A9和SLC16A7的表达增加，提示细胞代谢发生改变。随后的实验表明，AQR克隆具有与糖酵解升高一致的特征，包括葡萄糖、乳酸、谷氨酰胺水平升高，葡萄糖依赖性增加，GLUT1表达增加，葡萄糖后细胞外酸化速率增加，活性氧水平降低和耗氧率降低。BEZ235与糖酵解抑制剂3 - 溴丙酮酸联合治疗在AQR克隆中具有协同作用，但在亲本细胞中仅具有相加作用。DNA测序显示AQR细胞中存在线粒体DNA（mtDNA）MT - C01变体，而亲本细胞中不存在。亲本细胞中线粒体DNA的缺失诱导了对BEZ235和其他PI3K/mTOR抑制剂的耐药性，并伴有糖酵解增加。本研究结果提供了首个证据，表明与mtDNA突变相关的代谢转换可能是AQR的潜在机制。
