Integrated Approach Reveals Role of Mitochondrial Germ-Line Mutation F18L in Respiratory Chain, Oxidative Alterations, Drug Sensitivity, and Patient Prognosis in Glioblastoma

• Published in: International journal of molecular sciences Vol. 20; no. 13; p. 3364
• Main Authors: Keatley, Kathleen, Stromei-Cleroux, Samuel, Wiltshire, Tammy, Rajala, Nina, Burton, Gary, Holt, William V, Littlewood, D Timothy J, Briscoe, Andrew G, Jung, Josephine, Ashkan, Keyoumars, Heales, Simon J, Pilkington, Geoffrey J, Meunier, Brigitte, McGeehan, John E, Hargreaves, Iain P, McGeehan, Rhiannon E
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09.07.2019; MDPI
• Subjects: Adenosine triphosphate; Apoptosis; Binding sites; Biopsy; Brain cancer; Calcium signalling; Calcium transport; Cell culture; Cell growth; Cell proliferation; clomipramine; Clomipramine - pharmacology; CoQ10; Dehydrogenases; Deoxyribonucleic acid; DNA; DNA methylation; DNA, Mitochondrial - genetics; Drugs; Electron transport; Gene expression; Germ-Line Mutation - genetics; Glioblastoma; Glioblastoma - genetics; Humans; Hypoxia-inducible factor 1; Kaplan-Meier Estimate; Life Sciences; Male; Medical prognosis; Membrane potential; Metabolism; Mitochondria; Mitochondria - metabolism; Mitochondrial DNA; mtDNA; Mutation; Mutation - genetics; NADP; Nucleotides; Oxidation-Reduction; OXPHOS; Parameter sensitivity; Patients; prognosis; Protein transport; Reactive Oxygen Species - metabolism; Redox properties; Regulatory sequences; Replication initiation; ROS; Sensitivity; Transcription factors; Transcription initiation; Translocation; Transport; Tricarboxylic acid cycle; Ubiquinone - analogs & derivatives; Ubiquinone - metabolism; clomipramine; mutation; glioblastoma; mtDNA; mitochondria; CoQ10; ROS; OXPHOS; prognosis
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20133364

Glioblastoma is the most common and malignant primary brain tumour in adults, with a dismal prognosis. This is partly due to considerable inter- and intra-tumour heterogeneity. Changes in the cellular energy-producing mitochondrial respiratory chain complex (MRC) activities are a hallmark of glioblastoma relative to the normal brain, and associate with differential survival outcomes. Targeting MRC complexes with drugs can also facilitate anti-glioblastoma activity. Whether mutations in the mitochondrial DNA (mtDNA) that encode several components of the MRC contribute to these phenomena remains underexplored. We identified a germ-line mtDNA mutation (m. 14798T > C), enriched in glioblastoma relative to healthy controls, that causes an amino acid substitution F18L within the core mtDNA-encoded cytochrome b subunit of MRC complex III. F18L is predicted to alter corresponding complex III activity, and sensitivity to complex III-targeting drugs. This could in turn alter reactive oxygen species (ROS) production, cell behaviour and, consequently, patient outcomes. Here we show that, despite a heterogeneous mitochondrial background in adult glioblastoma patient biopsy-derived cell cultures, the F18L substitution associates with alterations in individual MRC complex activities, in particular a 75% increase in MRC complex II_III activity, and a 34% reduction in CoQ10, the natural substrate for MRC complex III, levels. Downstream characterisation of an F18L-carrier revealed an 87% increase in intra-cellular ROS, an altered cellular distribution of mitochondrial-specific ROS, and a 64% increased sensitivity to clomipramine, a repurposed MRC complex III-targeting drug. In patients, F18L-carriers that received the current standard of care treatment had a poorer prognosis than non-carriers (373 days vs. 415 days, respectively). Single germ-line mitochondrial mutations could predispose individuals to differential prognoses, and sensitivity to mitochondrial targeted drugs. Thus, F18L, which is present in blood could serve as a useful non-invasive biomarker for the stratification of patients into prognostically relevant groups, one of which requires a lower dose of clomipramine to achieve clinical effect, thus minimising side-effects.