Dysregulation of polyamine metabolism has been implicated in cancer initiation and progression; however, the mechanism of polyamine dysregulation in cancer is not fully understood. In this study, we investigated the role of MUC1, a mucin protein overexpressed in pancreatic cancer, in regulating polyamine metabolism. Utilizing pancreatic cancer patient data, we noted a positive correlation between MUC1 expression and the expression of key polyamine metabolism pathway genes. Functional studies revealed that knockdown of spermidine/spermine N1-acetyltransferase 1 ( SAT1 ), a key enzyme involved in polyamine catabolism, attenuated the oncogenic functions of MUC1, including cell survival and proliferation. We further identified a regulatory axis whereby MUC1 stabilized hypoxia-inducible factor (HIF-1α), leading to increased SAT1 expression, which in turn induced carbon flux into the tricarboxylic acid cycle. MUC1-mediated stabilization of HIF-1α enhanced the promoter occupancy of the latter on SAT1 promoter and corresponding transcriptional activation of SAT1 , which could be abrogated by pharmacological inhibition of HIF-1α or CRISPR/Cas9-mediated knockout of HIF1A . MUC1 knockdown caused a significant reduction in the levels of SAT1-generated metabolites, N1-acetylspermidine and N8-acetylspermidine. Given the known role of MUC1 in therapy resistance, we also investigated whether inhibiting SAT1 would enhance the efficacy of FOLFIRINOX chemotherapy. By utilizing organoid and orthotopic pancreatic cancer mouse models, we observed that targeting SAT1 with pentamidine improved the efficacy of FOLFIRINOX, suggesting that the combination may represent a promising therapeutic strategy against pancreatic cancer. This study provides insights into the interplay between MUC1 and polyamine metabolism, offering potential avenues for the development of treatments against pancreatic cancer.

Oleaginous yeast Rhodosporidium toruloides has great biotechnological potential and scientific interest, yet the molecular rationale of its cellular behavior to carbon and nitrogen ratios with concurrent lipid agglomeration remains elusive. Here, metabolomics adaptations of the R. toruloides in response to varying glucose and nitrogen concentrations have been investigated. In preliminary screening we found that 5% glucose (w/v) was optimal for further analysis in Rhodosporidium toruloides 3641. Hereafter, the effect of complementation to increase lipid agglomeration was evaluated with different nitrogen sources and their concentration. The results obtained illustrated that the biomass (13 g/L) and lipid (9.1 g/L) production were maximum on 5% (w/v) glucose and 0.12% (NH₄)₂SO₄. Furthermore, to shed lights on lipid accumulation induced by nitrogen-limitation, we performed metabolomic analysis of the oleaginous yeast R. toruloides 3641. Significant changes were observed in metabolite concentrations by qualitative metabolomics through gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), which were mapped onto the governing metabolic pathways. Notable finding in this strain concerns glycerol and CDP-DAG metabolism wherein reduced production of glycerol and phospholipids induced a bypass leading to enhanced de-novo triacylglyceride synthesis. Collectively, our findings help in understanding the central carbon metabolism of R. toruloides which may assist in developing rationale metabolic models and engineering efforts in this organism.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by frequent KRAS mutations, which activate the MAPK pathway to promote PDAC progression. In this study, we explored metabolic vulnerabilities of PDAC by assessing initial metabolic reprogramming upon ERK inhibition using metabolomics, lipidomics, and isotope-tracing experiments. ERK inhibition enhanced lipid turnover and fatty acid (FA) oxidation while inhibiting glycolysis, glucose oxidation, and glutamine metabolism in PDAC cells. Moreover, lipophagy, but not cytosolic lipolysis, was responsible for the increased lipid turnover and FA oxidation upon ERK inhibition. Lipophagy and lipophagy-fueled FA oxidation were induced by increased nuclear translocation and activity of the transcription factor TFEB. Pharmacologic inhibition of FA oxidation in combination with KRASG12D/MEK/ERK inhibitors synergistically decreased the growth of PDAC cell lines and organoids. The combination decreased tumor burden and improved survival in orthotopic cell line and patient-derived xenograft PDAC models. Overall, this study provides mechanistic insights into the development of metabolic resistance to KRAS signaling inhibition and demonstrates that FA oxidation is a metabolic vulnerability following KRAS signaling inhibition that can be utilized as an effective therapeutic target to treat PDAC. Significance: Treating pancreatic cancer with inhibitors that target the KRAS pathway rewires metabolism by increasing lipophagy and fatty acid oxidation, which can be targeted to sensitize tumors to KRAS signaling inhibition. See related article by Delgado Herrera et al., p. XX .

Radiotherapy (RT) is a mainstay in the treatment of solid tumors, including lung cancer, yet the long-term efficacy is often limited by radioresistance. RT promotes multiple different cell death processes, and gaining mechanistic insights into how metabolic cell death pathways like ferroptosis contribute to resistance could enable the development of effective modulators of radiation sensitivity. In this study, through metabolomic and functional analyses, we identified dihydroorotate dehydrogenase (DHODH) as a critical regulator of radioresistance in lung cancer. DHODH expression was induced by radiation in a cAMP response element-binding protein–dependent manner, and both radiation exposure and acquired radioresistant states were associated with elevated DHODH activity. DHODH promoted radioresistance in part by generating ubiquinol, a mitochondrial lipid antioxidant that suppresses ferroptosis, and by supporting DNA repair through its role in de novo pyrimidine synthesis. Although DHODH inhibition alone had limited therapeutic effect, its combination with interferon-gamma (IFNγ; delivered directly or via anti–PD-1 immunotherapy) synergistically enhanced RT-induced ferroptosis and overcame radioresistance in preclinical models. These findings reveal a metabolic mechanism of radioresistance driven by DHODH-mediated ferroptosis defense and provide a rationale for combining DHODH inhibitors with RT and immunotherapy in lung cancer and potentially other solid tumors. Significance: DHODH acts as a metabolic barrier to ferroptosis-driven radiosensitivity and can be targeted in combination with radiotherapy and immunotherapy as a strategy for treating lung cancer.