Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest tumors, partly due to its intrinsic aggressiveness, metastatic potential, and chemoresistance of the contained cancer stem cells (CSCs). Pancreatic CSCs strongly rely on mitochondrial metabolism to maintain their stemness, therefore representing a putative target for their elimination. Since mitochondrial homeostasis depends on the tightly controlled balance between fusion and fission processes, namely mitochondrial dynamics, we aim to study this mechanism in the context of stemness. In human PDAC tissues, the mitochondrial fission gene DNM1L (DRP1) was overexpressed and positively correlated with the stemness signature. Moreover, we observe that primary human CSCs display smaller mitochondria and a higher DRP1/MFN2 expression ratio, indicating the activation of the mitochondrial fission. Interestingly, treatment with the DRP1 inhibitor mDivi-1 induced dose-dependent apoptosis, especially in CD133⁺ CSCs, due to the accumulation of dysfunctional mitochondria and the subsequent energy crisis in this subpopulation. Mechanistically, mDivi-1 inhibited stemness-related features, such as self-renewal, tumorigenicity, and invasiveness and chemosensitized the cells to the cytotoxic effects of Gemcitabine. In summary, mitochondrial fission is an essential process for pancreatic CSCs and represents an attractive target for designing novel multimodal treatments that will more efficiently eliminate cells with high tumorigenic potential.

Lipid droplets as metabolic determinants for stemness and chemoresistance in cancer

The pronounced desmoplastic response in pancreatic ductal adenocarcinoma (PDAC) contributes to the development of a microenvironment depleted of oxygen and nutrients. To survive in this hostile environment, PDAC cells use various adaptive mechanisms that may represent therapeutic targets. In this study, we showed that nutrient starvation and microenvironmental signals commonly present in PDAC tumors activate PPARδ to rewire cellular metabolism and promote invasive and metastatic properties both in vitro and in vivo. Mild mitochondrial inhibition induced by low-dose etomoxir or signals from tumor-associated macrophages altered the lipidome and triggered the downstream transcriptional program of PPARδ. Specifically, PPARδ reduced mitochondrial oxygen consumption and boosted the glycolytic capacity by altering the ratio of MYC and PGC1A expression, two key regulators of pancreatic cancer metabolism. Notably, genetic or pharmacologic inhibition of PPARδ prevented this metabolic rewiring and suppressed both invasiveness in vitro and metastasis in vivo. These findings establish PPARδ as a central driver of metabolic reprogramming in response to starvation and tumor microenvironmental cues that promotes a prometastatic phenotype in PDAC, suggesting that PPARδ inhibition could serve as a therapeutic strategy to combat PDAC progression. Significance: Nutrient starvation and microenvironmental signals activate PPARδ in pancreatic cancer to support survival and metastasis by promoting metabolic plasticity and invasiveness, providing a strong rationale for developing PPARδ-targeted therapies for pancreatic cancer.

The peroxisome proliferator-activated receptors (PPAR-α, PPAR-δ, and PPAR-γ) are transcription factors that belong to the nuclear hormone receptor superfamily. Upon activation by specific lipids, they regulate gene expression by directly binding to PPAR response elements (PPREs) in the DNA. Although the functions of the different PPARs are specific to the isoform, tissue, and context, all three PPARs are generally involved in energy homeostasis through lipid sensing in physiological conditions. Importantly, there is increasing evidence linking PPARs with malignant behavior in cancer, regulating features frequently attributed to the aggressive subpopulation of cancer stem cells (CSCs): self-renewal, tumor initiation, chemoresistance, metastasis, and immune evasion. However, contradictory effects have been described for each isoform in various cancer types, and their implication in these malignant features may not consistently follow a pro- or anti-tumoral pattern. In this review, we revise the current knowledge on the role of the PPAR family members in cancer, with a special focus on cancer stemness, and discuss the potential for PPARs as therapeutic targets in CSC-driven relapse and resistance.

High-fat diet (HFD) and obesity are increasingly recognized as risk factors of pancreatic ductal adenocarcinoma (PDAC), yet the mechanisms by which dietary fat contribute to oncogenic transformation remain elusive. Using an inducible acinar-specific Kras ^G12V / Trp53 -loss genetically-engineered mouse model of PDAC, we established early-and late-onset protocols to assess age-dependent susceptibility to HFD. Specifically, HFD accelerated tumorigenesis with poorer prognosis in early-onset mice and, strikingly, enabled full PDAC development in late-onset adult mice otherwise resistant to oncogenic transformation. Tumors arising under HFD activated a distinct transcriptional and epigenetic state enriched in pathways or genes related to stemness, plasticity, and metastatic competence, which was maintained even in tumor-derived cell lines. Mechanistically, fatty acid-educated macrophages secreted the cathelicidin antimicrobial peptide (CAMP), activating P2X purinoceptor 7 (P2RX7) signaling in tumor cells to drive a highly plastic, immune-evasive phenotype reinforced by the expression of the peptidoglycan recognition protein 1 (PGLYRP1), further shielding tumor cells from macrophage phagocytosis. Functionally, HFD-induced tumors displayed enhanced metastatic potential independent of host context. Analysis of 164 human PDAC samples revealed that elevated body-mass index (BMI) was associated to a conserved CAMP-P2RX7-CXCR4 signature, maintained despite weight loss during disease progression. Together, these findings uncover a diet-imprinted macrophage-tumor cell circuit that promotes transformation and accelerates PDAC progression, positioning it as a therapeutic vulnerability in obesity-associated pancreatic cancer. Statement of significance: High-fat diet induces pancreatic tumorigenesis in adult tissue, driving metastatic competence and a plastic state, and ultimately engages a macrophage-derived CAMP-P2RX7 circuit that reinforces immune evasion and accelerates PDAC progression.

Induction of EMT-like phenotype and metabolic switch in PDAC cells upon starvation. A, Representative images illustrating morphologic changes for PDAC-354 cells in response to treatment for 72 hours with the complex I inhibitor metformin (3 mmol/L), the β-oxidation inhibitor etomoxir (20 μmol/L), the complex II inhibitor malonate (5 mmol/L), the pyruvate carrier inhibitor UK5099 (100 μmol/L), or tumor-like conditions [low pH (HCl 50 μmol/L) + low glucose (1 mmol/L) + 3%O2]. Scale bar, 50 μm. B, Expression of EMT-associated genes (ZEB1, SNAI1, SNAI2, LOXL2, and VIM) was determined by RT-qPCR after cells were treated for 48 hours as indicated in A or with MCM. Pooled data for PDAC-185, A6L, 215, 253, and 354 (n ≥ 4 for each cell type). Data are normalized to HPRT1. Eto, etomoxier; Mal, malonate; Met, metformin. C, PDAC-215, 253, and 354 cells were treated with MCM or 20 μmol/L etomoxir for 48 hours and seeded in modified Boyden invasion chambers containing 20% FBS in the lower compartment. The number of invasive cells was analyzed after 16 hours (n = 7–11). D, GFP+-Luciferase+-PDAC-354 cells were treated with control, MCM, or 20 μmol/L etomoxir for 48 hours and then injected intrasplenically to assess their metastatic capacity (n = 9 mice/group). Representative photographs of liver metastasis (top) and subsequent hematoxylin and eosin staining (bottom). Scale bar, 200 μm. E, Representative OCR profile for PDAC-253 cells treated for 48 hours as indicated (mitochondrial stress test). O, ATP synthase inhibitor oligomycin; F, mitochondrial OXPHOS uncoupler FCCP [carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone]; A+R, complex III inhibitor antimycin A + electron transport change inhibitor rotenone. F, Maximal and ATP-linked respiration (resp) in non-CSC vs. CSC cells. Bars represent pooled data from PDAC-215, 253, and 354, showing individual data points corresponding to each PDX (n = 5–7). G, Representative extracellular acidification rate (ECAR) profile for PDAC-253 cells treated for 48 hours as indicated (glycolysis test). G, glucose; O, ATP synthase inhibitor oligomycin; 2DG, glycolysis inhibitor 2-deoxy-glucose. H, Glycolysis, glycolytic capacity, and glycolytic reserve in adherent (non-CSC) vs. sphere-derived cells (CSC). Bars represent pooled data from PDAC-215, 253, and 354, showing individual data points corresponding to each PDX (n = 4–5). All data are represented as the mean ± SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001. See also Supplementary Figs. S1–S3.