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Abstract

Metabolic reprogramming is a hallmark of cancer, and many oncogenic signaling pathways profoundly impact cellular metabolism. Here, I investigated oncogene-specific metabolic alterations in a mouse model of hepatocellular carcinoma (HCC) that could contribute to tumor initiation and progression and may be exploited for therapeutic intervention. Transposon-based vectors encoding either Myc overexpression (MycOE) and expression of constitutively active Akt1 (Akt1Myr) or MycOE, with mutant Nras (NrasG12V) were injected into the tail veins of C57BL/6 mice. Resulting tumour-bearing and control livers were subjected to multi-layered profiling, including transcriptomic profiling, immune staining, polar metabolite analysis (metabolomics), and lipid characterization (lipidomics, total fatty acids, and oxylipins).

Despite comparable overall survival, the two models displayed strikingly different phenotypes. MycOE; Akt1Myr tumors were larger and more aggressive, reflecting a highly proliferative state supported by anabolic metabolic reprogramming. These tumors exhibited elevated glycolytic intermediates, increased amino acid pools, higher monounsaturated fatty acid levels, and upregulated fatty acid uptake machinery, including Cd36 upregulation, consistent with enhanced biosynthetic activity. In contrast, MycOE; NrasG12V tumor-bearing livers contained numerous small tumor nodules and displayed a pronounced inflammatory and immunosuppressive phenotype, characterized by higher infiltration of tumor-associated macrophages, CD8+ T cells, and PD1 expression, indicative of T cell exhaustion. Furthermore, MycOE; NrasG12V tumors exhibited accumulation of inflammatory lipid mediators, such as lysophosphatidylcholines (LPCs). Transcriptomics corroborated these findings, showing upregulation of biosynthetic and oxidative phosphorylation pathways in MycOE; Akt1Myr tumors, and enhanced inflammatory and immune-modulatory signaling in MycOE; NrasG12V tumors.

Functionally, I tested metabolic alterations induced by these oncogenes in vitro using murine HCC cell lines driven either by MycOE; Akt1myr or MycOE; NrasG12V to identify selective vulnerabilities. Targeting lipid and eicosanoid metabolism, fatty acid desaturation, redox balance, and mitochondrial metabolism revealed genotype-specific dependencies: inhibition of Lp-PLA2 by darapladib suppressed proliferation of both cells, whereas celecoxib, a selective COX-2 inhibitor, unexpectedly promoted the growth of MycOE; NrasG12V; Trp53-/- cells. Cells from both genotypes were insensitive to blockade of fatty acid β-oxidation. Notably, MycOE; Akt1myr; Trp53-/- cells were more sensitive to Scd1 inhibition, whereas MycOE; NrasG12V; Trp53-/- cells exhibited pronounced vulnerability to ferroptosis induction and complex I inhibition, highlighting ferroptosis and mitochondrial respiration as potential therapeutic targets in this context.

I found that knockdown of prostaglandin-endoperoxide synthase 2 (Ptgs2, the gene encoding COX-2) in MycOE; NrasG12V tumors during tumorigenesis did not affect animal survival but resulted in distinct phenotypic changes, with immunohistochemistry revealing increased tumor cell proliferation and reduced immune infiltration. Transcriptomic analysis showed increased expression of gene signatures associated with proliferation and oxidative metabolism, accompanied by decreased inflammatory signatures. Lipidomic profiling demonstrated reduced levels of lysophospholipids and depletion of acylcarnitines, suggesting remodelling of the lipidome and enhanced fatty acid β-oxidation. Notably, these effects could not be recapitulated in vitro, suggesting a non-cell-autonomous mechanism.

Collectively, my findings demonstrate that different oncogenic drivers establish distinct metabolic and immunologic programs in murine HCC, potentially creating genotype-specific vulnerabilities. Furthermore, Ptgs2 orchestrates context-dependent metabolic and immune interactions that control proliferation and aggressiveness. Future studies employing timeresolved tumor induction, single-cell RNA sequencing, or modulation of specific immune compartments could clarify a potential role of Ptgs2 in defining tumor evolutionary trajectories and reveal windows of vulnerability for targeted or combinatorial therapies.