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Pancreatic ductal adenocarcinoma (PDAC) remains among the most lethal cancers, with metastasis as the primary driver of mortality. While metastatic mechanisms are shared across malignancies, PDAC metastasis poses unique therapeutic challenges due to the presence of extensive tumor heterogeneity, desmoplasia, and immunosuppression - features that enable diverse migratory behaviors and therapeutic resistance. Recent advances have shown that metastatic progression in PDAC emerges from dynamic interactions between tumor cell-intrinsic and microenvironmental factors, each adapting to evolving stressors throughout the metastatic cascade. In the primary tumor, genomic instability and epigenetic reprogramming generate subclones with heightened invasive potential, while dense stromal reactions and myeloid-dominated immune suppression facilitate escape. During circulation, PDAC cells employ distinctive survival strategies through homotypic clustering and heterotypic interactions with blood components. At distant sites, PDAC cells adapt to organ-specific microenvironments through context-dependent metabolic and immune modulation, resulting in phenotypes that diverge from the primary tumor. In this Review, we examine how tumor-stroma crosstalk mechanisms shape metastatic progression in PDAC, provide a framework for understanding why conventional therapies often fail against metastatic disease, and highlight emerging opportunities for stage- and site-specific therapeutic interventions that target these unique adaptations.

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in the US. Despite multiple large-scale genetic sequencing studies, identification of predictors of patient survival remains challenging. We performed a comprehensive assessment and integrative analysis of large-scale gene expression datasets, across multiple platforms, to enable discovery of a prognostic gene signature for patient survival in pancreatic cancer. PDAC RNA-Sequencing data from The Cancer Genome Atlas was stratified into Survival+ (>2-year survival) and Survival-(<1-year survival) cohorts (n = 47). Comparisons of RNA expression profiles between survival groups and normal pancreatic tissue expression data from the Gene Expression Omnibus generated an initial PDAC specific prognostic differential expression gene list. The candidate prognostic gene list was then trained on the Australian pancreatic cancer dataset from the ICGC database (n = 103), using iterative sampling based algorithms, to derive a gene signature predictive of patient survival. The gene signature was validated in 2 independent patient cohorts and against existing PDAC subtype classifications. We identified 707 candidate prognostic genes exhibiting differential expression in tumor versus normal tissue. A substantial fraction of these genes was also found to be differentially methylated between survival groups. From the candidate gene list, a 5-gene signature (ADM, ASPM, DCBLD2, E2F7, and KRT6A) was identified. Our signature demonstrated significant power to predict patient survival in two distinct patient cohorts and was independent of AJCC TNM staging. Cross-validation of our gene signature reported a better ROC AUC (≥ 0.8) when compared to existing PDAC survival signatures. Furthermore, validation of our signature through immunohistochemical analysis of patient tumor tissue and existing gene expression subtyping data in PDAC, demonstrated a correlation to the presence of vascular invasion and the aggressive squamous tumor subtype. Assessment of these genes in patient biopsies could help further inform risk-stratification and treatment decisions in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) remains among the most lethal cancers, with metastasis as the primary driver of mortality. While metastatic mechanisms are shared across malignancies, PDAC metastasis poses unique therapeutic challenges due to the presence of extensive tumor heterogeneity, desmoplasia, and immunosuppression - features that enable diverse migratory behaviors and therapeutic resistance. Recent advances have shown that metastatic progression in PDAC emerges from dynamic interactions between tumor cell-intrinsic and microenvironmental factors, each adapting to evolving stressors throughout the metastatic cascade. In the primary tumor, genomic instability and epigenetic reprogramming generate subclones with heightened invasive potential, while dense stromal reactions and myeloid-dominated immune suppression facilitate escape. During circulation, PDAC cells employ distinctive survival strategies through homotypic clustering and heterotypic interactions with blood components. At distant sites, PDAC cells adapt to organ-specific microenvironments through context-dependent metabolic and immune modulation, resulting in phenotypes that diverge from the primary tumor. In this Review, we examine how tumor-stroma crosstalk mechanisms shape metastatic progression in PDAC, provide a framework for understanding why conventional therapies often fail against metastatic disease, and highlight emerging opportunities for stage- and site-specific therapeutic interventions that target these unique adaptations.

TNF, acting through p55 tumor necrosis factor receptor 1 (TNFR1), contributes to the pathogenesis of many inflammatory diseases. TNFR-associated periodic syndrome (TRAPS, OMIM 142680) is an autosomal dominant autoinflammatory disorder characterized by prolonged attacks of fevers, peritonitis, and soft tissue inflammation. TRAPS is caused by missense mutations in the extracellular domain of TNFR1 that affect receptor folding and trafficking. These mutations lead to loss of normal function rather than gain of function, and thus the pathogenesis of TRAPS is an enigma. Here we show that mutant TNFR1 accumulates intracellularly in peripheral blood mononuclear cells of TRAPS patients and in multiple cell types from two independent lines of knockin mice harboring TRAPS-associated TNFR1 mutations. Mutant TNFR1 did not function as a surface receptor for TNF but rather enhanced activation of MAPKs and secretion of proinflammatory cytokines upon stimulation with LPS. Enhanced inflammation depended on autocrine TNF secretion and WT TNFR1 in mouse and human myeloid cells but not in fibroblasts. Heterozygous TNFR1-mutant mice were hypersensitive to LPS-induced septic shock, whereas homozygous TNFR1-mutant mice resembled TNFR1-deficient mice and were resistant to septic shock. Thus WT and mutant TNFR1 act in concert from distinct cellular locations to potentiate inflammation in TRAPS. These findings establish a mechanism of pathogenesis in autosomal dominant diseases where full expression of the disease phenotype depends on functional cooperation between WT and mutant proteins and also may explain partial responses of TRAPS patients to TNF blockade.

Cancer-associated fibroblasts (CAFs) are indispensable architects of the tumor microenvironment. They perform the essential functions of extracellular matrix deposition, stromal remodeling, tumor vasculature modulation, modification of tumor metabolism, and participation in crosstalk between cancer and immune cells. In this review, we discuss our current understanding of the principal differences between normal fibroblasts and CAFs, the origin of CAFs, their functions, and ultimately, highlight the intimate connection of CAFs to virtually all of the hallmarks of cancer. We address the remarkable degree of functional diversity and phenotypic plasticity displayed by CAFs and strive to stratify CAF biology among different tumor types into practical functional groups. Finally, we summarize the status of recent and ongoing trials of CAF-directed therapies and contend that the paucity of trials resulting in Food and Drug Administration (FDA) approvals thus far is a consequence of the failure to identify targets exclusive of pro-tumorigenic CAF phenotypes that are mechanistically linked to specific CAF functions. We believe that the development of a unified CAF nomenclature, the standardization of functional assays to assess the loss-of-function of CAF properties, and the establishment of rigorous definitions of CAF subpopulations and their mechanistic functions in cancer progression will be crucial to fully realize the promise of CAF-targeted therapies.

Despite efforts in understanding its underlying mechanisms, the etiology of chromosomal instability (CIN) remains unclear for many tumor types. Here, we identify CIN initiation as a previously undescribed function for APOBEC3A (A3A), a cytidine deaminase upregulated across cancer types. Using genetic mouse models of pancreatic ductal adenocarcinoma (PDA) and genomics analyses in human tumor cells we show that A3A-induced CIN leads to aggressive tumors characterized by enhanced early dissemination and metastasis in a STING-dependent manner and independently of the canonical deaminase functions of A3A. We show that A3A upregulation recapitulates numerous copy number alterations commonly observed in patients with PDA, including co-deletions in DNA repair pathway genes, which in turn render these tumors susceptible to poly (ADP-ribose) polymerase inhibition. Overall, our results demonstrate that A3A plays an unexpected role in PDA as a specific driver of CIN, with significant effects on disease progression and treatment.

Abstract The degree of metastatic disease varies widely amongst cancer patients and impacts clinical outcomes. However, the biological and functional differences that drive the extent of metastasis are poorly understood. We analyzed primary tumors and paired metastases using a multi-fluorescent lineage-labeled mouse model of pancreatic ductal adenocarcinoma (PDAC) – a tumor type where most patients present with metastases. Genomic and transcriptomic analysis revealed an association between metastatic burden and gene amplification or transcriptional upregulation of MYC and its downstream targets. Functional experiments showed that MYC promotes metastasis by recruiting tumor associated macrophages (TAMs), leading to greater bloodstream intravasation. Consistent with these findings, metastatic progression in human PDAC was associated with activation of MYC signaling pathways and enrichment for MYC amplifications specifically in metastatic patients. Collectively, these results implicate MYC activity as a major determinant of metastatic burden in advanced PDAC. Competing Interest Statement B.Z.S. has received research funding from Boehringer-Ingelheim and serves as a consultant to iTeos Therapeutics. E.L.C. has received research funding from Janssen, Merck, and Becton Dickinson. Footnotes * ↵✉ Ravikanth.Maddipati{at}UTsouthwestern.edu; bstanger{at}upenn.edu * Statement of Significance Here, we investigate metastatic variation seen clinically in PDAC patients and murine PDAC tumors and identify MYC as a major driver of this heterogeneity. * Conflict of interest statement B.Z.S. has received research funding from Boehringer-Ingelheim and serves as a consultant to iTeos Therapeutics. E.L.C. has received research funding from Janssen, Merck, and Becton Dickinson.