Cachexia, a severe wasting syndrome characterized by tumour-induced metabolic dysregulation, is a leading cause of death in people with cancer, yet its underlying mechanisms remain poorly understood. Here we show that a longitudinal full-body single-nuclei-resolution transcriptome analysis in a Drosophila model of cancer cachexia captures interorgan dysregulations. Our study reveals that the tumour-secreted interleukin-like cytokine Upd3 induces fat-body expression of Pepck1 and Pdk, key regulators of gluconeogenesis, disrupting glucose metabolism and contributing to cachexia. Similarly, in mouse cancer cachexia models, we observe IL-6–JAK–STAT-signalling-mediated induction of Pck1 and Pdk3 expression in the liver. Increased expression of these genes in fly, mouse, and human correlates with poor prognosis, and hepatic expression of Pdk3 emerges as a previously unknown mechanism contributing to metabolic dysfunction in cancer cachexia. This study highlights the conserved nature of tumour-induced metabolic disruptions and identifies potential therapeutic targets to mitigate cachexia in people with cancer.

De novo lipogenesis is a highly regulated metabolic process, which is known to be activated through transcriptional regulation of lipogenic genes, including fatty acid synthase (FASN). Unexpectedly, we find that the expression of FASN protein remains unchanged during Drosophila larval development from the second to the third instar larval stages (L2 to L3) when lipogenesis is hyperactive. Instead, acetylation of FASN is significantly upregulated in fast-growing larvae. We further show that lysine K813 residue is highly acetylated in developing larvae, and its acetylation is required for elevated FASN activity, body fat accumulation, and normal development. Intriguingly, K813 is autoacetylated by acetyl-CoA (AcCoA) in a dosage-dependent manner independent of acetyltransferases. Mechanistically, the autoacetylation of K813 is mediated by a novel P-loop-like motif (N-xx-G-x-A). Lastly, we find that K813 is deacetylated by Sirt1, which brings FASN activity to baseline level. In summary, this work uncovers a previously unappreciated role of FASN acetylation in developmental lipogenesis and a novel mechanism for protein autoacetylation, through which Drosophila larvae control metabolic homeostasis by linking AcCoA, lysine acetylation, and de novo lipogenesis.

Tumors reprogram lipid metabolism in distant tissues to support their growth. In adult Drosophila , gut tumors secrete the PDGF/VEGF-like factor Pvf1, which activates the TORC1-Hnf4 pathway in hepatocyte-like oenocytes. This drives production of very long-chain fatty acids and wax esters essential for tracheal growth around the tumor. Blocking Hnf4 or the elongase mElo in oenocytes strongly suppresses tracheogenesis, tumor progression, and cachexia-like organ wasting, while extending host lifespan. The same pathway also controls tracheal development in healthy flies. Lipoprotein receptor LpR2 depletion in oenocytes rescues the observed tumor induced tracheal tracheal remodeling. This tumor-host interaction is conserved: VEGF-A induces lipid metabolism genes in human hepatocytes, and lung tumor-bearing mice show elevated hepatic Hnf4 and Elovl7 . The study reveals a non-autonomous role of the TORC1-Hnf4 axis in lipid-mediated tumor progression and identifies potential therapeutic targets for cancer-associated metabolic dysfunction.

Lysine acetylation is a conserved post-translational modification and a key regulatory mechanism for various cellular processes, including metabolic control, epigenetic regulation, and cellular signaling transduction. Recent advances in mass spectrometry (MS) enable the extensive identification of acetylated lysine residues of histone and nonhistone proteins. However, protein enrichment before MS analysis may be necessary to improve the detection of low-abundant proteins or proteins that exhibit low acetylation levels. Fatty acid synthase (FASN), an essential enzyme catalyzing the de novo synthesis of fatty acids, has been found to be acetylated in various species, from fruit flies to humans. Here, we describe a step-by-step process of antibody-based protein enrichment and sample preparation for acetylation identification of endogenous FASN protein by MS-based proteomics analysis. Meanwhile, we provide a protocol for nicotinamide adenine dinucleotide phosphate (NADPH) absorbance assay for FASN activity measurement, which is one of the primary functional readouts of de novo lipogenesis.

Coenzyme A (CoA), derived from Vitamin B5 (VB5; also called pantothenate), is essential for lipid metabolism, energy production, and cell proliferation. While the intracellular functions of CoA are well-characterized, much less is known about its tissue-specific regulation and systemic physiological roles. Here, using Drosophila melanogaster , we uncover a gut-renal circuit in which dietary VB5 fuels CoA biosynthesis specifically in the Malpighian tubules (MTs, the fly kidney), non-autonomously impacting gut homeostasis. We show that, in the MTs, Myc boosts renal CoA production by directly upregulating the pantothenate kinase Fbl (human PANK1-3 ortholog) and downregulating CG5828 , which we characterize as the functional ortholog of the metabolite phosphatase and CoA synthesis suppressor PANK4 ( dPANK4 ). Elevated CoA biosynthesis enhances the mevalonate-isoprenoid pathway activity in the gut, promoting intestinal stem cell proliferation. We further demonstrate that renal CoA production is required for gut tumor growth in a fly model. Consistently, MYC and genes within the CoA-isoprenoid axis display strong association with clinical outcomes in human cancers. Together, our findings establish that Myc-driven CoA metabolism generates an inter-organ signal that couples VB5 availability to stem cell control and tumor growth, and identify the CoA-isoprenoid axis as a targetable metabolic vulnerability in cancer.

Circulating hormones, that mediate communications across organs to maintain physiological balance, are commonly detected and quantified using enzyme-linked immunosorbent assays (ELISAs). However, while ELISA is well-suited for organisms where sample blood can be readily obtained, its application is considerably more challenging in smaller organisms, particularly Drosophila , which has gained widespread use in recent years for physiological studies. Here, we present sensitive phage display-mediated immuno-PCR (PD-iPCR) to detect Drosophila hemolymph proteins via two approaches: 1) by identifying high-affinity nanobodies through phage-display library screening and subsequent affinity maturation and 2) by generating a knock-in fly line producing secreted proteins tagged with tandem NanoTags composed of VHH05 and 127D01. Using these approaches, we successfully established PD-iPCR to detect insulin-binding ImpL2 protein in fly hemolymph. Notably, the tandem NanoTag-based sandwich PD-iPCR enabled highly sensitive detection of tagged antigens, allowing us to quantify elevated ImpL2 levels in the hemolymph of starved flies and those bearing Yki -induced gut tumors. Collectively, our results demonstrate that PD-iPCR enables detection of endogenous, low-abundance circulating hormones in Drosophila , providing a powerful tool for studying interorgan communication. Significance statement: Hormones and other secreted factors orchestrate organism-wide physiology, yet their routine quantification in Drosophila has been limited by the limited volume of hemolymph available for assays like enzyme-linked immunosorbent assay (ELISA). Here, we present phage display-mediated immuno-PCR (PD-iPCR) as a novel sensitive platform for quantifying secreted proteins in flies in vivo . Using ImpL2 as an example, we successfully detected nanomolar level of circulating ImpL2 and monitored its physiological changes during starvation and tumorigenesis using PD-iPCR. This approach can be readily expanded to multiplexed quantification of secreted proteins in vivo by leveraging the multiple available nanobodies and the vast collection of epitope-tagged Drosophila lines. This work opens the door to systematic endocrine phenotyping across developmental stages and diverse physiological conditions.