Integrated approach reveals role of mitochondrial germ-line mutation F18L in respiratory chain, oxidative alterations, drug sensitivity, and patient prognosis in glioblastoma

Kathleen Keatley, Samuel Stromei-Cleroux , Tammy Wiltshire, Nina Katja Maria Rajala, Gary David Burton, William V. Holt, D. Timothy J. Littlewood, Andrew G. Briscoe, Josephine Jung, Keyoumars Ashkan, Simon J. Heales, Geoff Pilkington, Brigitte Meunier, John McGeehan, Iain Hargreaves, Rhiannon Lloyd

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Abstract

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 encodes several components of the MRC contribute to these phenomena, remains underexplored. We identified a germ-line mtDNA mutation (T14798C), 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.
Original languageEnglish
Article number3364
JournalInternational Journal of Molecular Sciences
Volume20
Issue number13
DOIs
Publication statusPublished - 9 Jul 2019

Keywords

  • Glioblastoma
  • clomipramine
  • prognosis
  • CoQ10
  • ROS
  • OXPHOS
  • mitochondria
  • mutation
  • mtDNA

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