Elliot, A. M. | bioRxiv Science

bioRxiv2023

Oncogenic RAS drives rapid onset cellular plasticity and elicits a tumour-promoting neutrophil response at the inception of preneoplastic development

Oncogenic driver mutations are frequently found in normal tissues, suggesting that additional non-genetic factors are required for tumourigenesis. Phenotypic plasticity is an important gateway to malignancy and inflammation can fuel tumourigenesis, however, little is known about when and how these hallmarks first arise. Using single-cell transcriptomics and in vivo live imaging we have characterised the immediate cell intrinsic and innate immune responses during the first 24 hours following oncogenic Ras activation, in an inducible zebrafish model of HRASG12V-mediated skin tumour initiation. We found that only a subset of basal keratinocytes, but not superficial keratinocytes, are susceptible to RAS-driven phenotypic plasticity. These preneoplastic cells undergo dedifferentiation and partial EMT, resembling malignant cells observed in human squamous cell carcinoma (SCC). Strikingly, the same subset instigates the development of tumour-promoting neutrophils, which in turn enhance preneoplastic cell proliferation. Our findings demonstrate that the effects of oncogenic Ras are primarily determined by the cell of origin and reveal an association between the unlocking of phenotypic plasticity and the onset of tumour-promoting inflammation.

cancer biology↗

bioRxiv2023

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

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 cells3,4. Targeting cancer metabolism is now being considered as a promising precision oncology therapeutic approach5. 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 HRASG12V 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 HRASG12V 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 findingsO_LIGlycolysis is upregulated in HRASG12V expressing preneoplastic cells (PNCs) in zebrafish skin, and is required for PNC proliferation C_LIO_LIOXPHOS respiration is impaired in PNCs and metformin complex I inhibition specifically eliminates PNCs C_LIO_LIPNC undergo mitochondrial fragmentation and exhibit reduced membrane potential C_LIO_LIMdivi reverses mitochondrial fragmentation in PNCs and triggers apoptosis C_LI

cancer biology↗