Preneoplastic cells switch to Warburg metabolism from their inception exposing multiple vulnerabilities for targeted elimination

Summary Otto Warburg first described tumour cells as displaying enhanced aerobic glycolysis whilst maintaining defective oxidative phosphorylation (OXPHOS) for energy production almost 100 years ago 1,2 . Since then, the ‘Warburg effect’ has been widely accepted as a key feature of rapidly proliferating cancer cells 3,4 . Targeting cancer metabolism is now being considered as a promising precision oncology therapeutic approach 5 . What is not clear is how early “Warburg metabolism” initiates during cancer progression and whether changes in energy metabolism might influence tumour progression ab initio . We set out to investigate energy metabolism in HRAS G12V driven preneoplastic cell (PNC) at inception, in a zebrafish skin PNC model; and to test how the impact of manipulating energy metabolism in the whole animal may impact PNC initiation. We find that, within 24 hours of HRAS G12V induction, PNCs upregulate “Warburg metabolism”, and that this is required for their expansion. We show that blocking glycolysis reduces PNC proliferation, whilst increasing available glucose both enhances PNC proliferation and also reduces apoptosis. Impaired OXPHOS of PNCs might be exploited therapeutically since a mild complex I inhibitor, metformin, selectively induces apoptosis and suppresses proliferation of PNCs. In addition, we find mitochondrial fragmentation in PNCs occur prior to metabolic alteration and this is important for their survival since exposure to Drp1/Dnml1 inhibitor, mdivi, which blocks mitochondrial fragmentation leads to enhanced PNC apoptosis. Our data indicate that altered energy metabolism is one of the earliest events upon oncogene activation in somatic cells, which provide a targeted and effective tumour prevention therapy. Key findings Glycolysis is upregulated in HRAS G12V expressing preneoplastic cells (PNCs) in zebrafish skin, and is required for PNC proliferation OXPHOS respiration is impaired in PNCs and metformin complex I inhibition specifically eliminates PNCs PNC undergo mitochondrial fragmentation and exhibit reduced membrane potential Mdivi reverses mitochondrial fragmentation in PNCs and triggers apoptosis