LAUSR

Skin epidermal stem cells detect, and correct aberrancies induced by oncogenic mutations. Different oncogenes invoke different mechanisms of epithelial tolerance: while wild-type cells outcompete β-catenin-Gain-of-Function (βcatGOF) mutant cells in the mouse skin epidermal stem cell layer, HrasG12V mutant cells outcompete wild-type cells, yet are integrated into normal tissue structure and function. We asked how metabolic states change as wild-type stem cells interface with mutant cells, and how this ultimately drives different cell competition outcomes in vivo. Combining two powerful experimental modalities -1. optical redox imaging to visualize endogenous levels of the co-enzymes NAD(P)H/FAD, adapted and evolved within our in vivo imaging platform to enable long term tracking and visualization of metabolic states of cells within the live animal, and 2.13C6- glucose tracer-assisted mass spectrometry to measure metabolic fluxes directly - we provide unprecedented resolution of the metabolic state at the interface of Mutant and Wild-type stem cells within the epidermis in vivo. By tracking endogenous redox ratio (NAD(P)H/FAD) with single cell resolution in the same mice over time, we show that wild-type epidermal stem cells maintain robust redox ratio despite their heterogeneous cell cycle states. We discover that both βcatGOF and HrasG12V models lead to a rapid drop in redox ratios (NAD(P)H/FAD). However, the “winner” cells in each model (wild-type cells in βcatGOF and mutant cells in HrasG12V model), rapidly recover their redox ratios, irrespective of the mutation induced. Glucose catabolic flux studies reveal that both βcatGOF and HrasG12V mutant epidermis upregulate flux and fractional contribution of glucose through TCA cycle, in line with the change in redox ratios. Contrastingly, the “winner” mutation HrasG12V specifically upregulates pyruvate to lactate rates (glycolysis readout) while the “loser” βcatGOF mutation downregulates this step. Hence, we reveal the metabolic adaptations that define the hallmarks of winners and losers during cell competition in vivo and uncover the nodes of regulation unique to each cell fate. These novel findings contrast with the expectations of Warburg effect, a fundamental concept in cancer metabolism, wherein proliferative cells expressing oncogenic mutations are expected to upregulate glycolysis at the expense of downstream TCA cycle and mitochondrial oxidation. Instead, our study suggests that decoupling lactate levels (glycolysis) and mitochondrial oxidation could be a strategy used by “winners” in cell competition. This study also reveals a metabolic plasticity inherent to epidermal stem cells that affect cell competition outcome with profound implications for therapeutically eliminating oncogenic mutations from the skin epidermis. Citation Format: Anupama Hemalatha, Valentina Greco. Differential metabolic adaptations define responses of winner and loser oncogenic mutant cells in skin epidermis in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 282.