Marini Cecilia, Ravera Silvia, Buschiazzo Ambra, Bianchi Giovanna, Orengo Anna Maria, Bruno Silvia, Bottoni Gianluca, Emionite Laura, Pastorino Fabio, Monteverde Elena, Garaboldi Lucia, Martella Roberto, Salani Barbara, Maggi Davide, Ponzoni Mirco, Fais Franco, Raffaghello Lizzia, Sambuceti Gianmario
CNR Institute of Molecular Bioimaging and Physiology (IBFM), Milan, Section of Genoa, Genoa, Italy.
Nuclear Medicine Unit, Department of Health Sciences, University of Genoa and IRCCS AOU San Martino-IST, Genoa, Italy.
Sci Rep. 2016 Apr 28;6:25092. doi: 10.1038/srep25092.
Cancer metabolism is characterized by an accelerated glycolytic rate facing reduced activity of oxidative phosphorylation. This "Warburg effect" represents a standard to diagnose and monitor tumor aggressiveness with (18)F-fluorodeoxyglucose whose uptake is currently regarded as an accurate index of total glucose consumption. Studying cancer metabolic response to respiratory chain inhibition by metformin, we repeatedly observed a reduction of tracer uptake facing a marked increase in glucose consumption. This puzzling discordance brought us to discover that (18)F-fluorodeoxyglucose preferentially accumulates within endoplasmic reticulum by exploiting the catalytic function of hexose-6-phosphate-dehydrogenase. Silencing enzyme expression and activity decreased both tracer uptake and glucose consumption, caused severe energy depletion and decreased NADPH content without altering mitochondrial function. These data document the existence of an unknown glucose metabolism triggered by hexose-6-phosphate-dehydrogenase within endoplasmic reticulum of cancer cells. Besides its basic relevance, this finding can improve clinical cancer diagnosis and might represent potential target for therapy.
癌症代谢的特征是糖酵解速率加快,而氧化磷酸化活性降低。这种“瓦伯格效应”是用(18)F-氟脱氧葡萄糖诊断和监测肿瘤侵袭性的标准,其摄取目前被视为总葡萄糖消耗的准确指标。在研究二甲双胍对呼吸链抑制的癌症代谢反应时,我们反复观察到示踪剂摄取减少,而葡萄糖消耗显著增加。这种令人费解的不一致促使我们发现,(18)F-氟脱氧葡萄糖通过利用己糖-6-磷酸脱氢酶的催化功能优先在内质网中积累。沉默酶的表达和活性会降低示踪剂摄取和葡萄糖消耗,导致严重的能量消耗和NADPH含量降低,而不会改变线粒体功能。这些数据证明了癌细胞内质网中由己糖-6-磷酸脱氢酶触发的未知葡萄糖代谢的存在。除了其基本相关性外,这一发现可以改善临床癌症诊断,并可能代表潜在的治疗靶点。