NEMO/NF-κB signaling functions as a double-edged sword in PanIN formation versus progression to pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is marked by a dismal survival rate, lacking effective therapeutics due to its aggressive growth, late-stage diagnosis, and chemotherapy resistance. Despite debates on NF-κB targeting for PDAC treatment, no successful approach has emerged. METHODS: To elucidate the role of NF-κB, we ablated NF-κB essential modulator (NEMO), critical for conventional NF-κB signaling, in the pancreata of mice that develop precancerous lesions (KC mouse model). Secretagogue-induced pancreatitis by cerulein injections was utilized to promote inflammation and accelerate PDAC development. RESULTS: NEMO deletion reduced fibrosis and inflammation in young KC mice, resulting in fewer pancreatic intraepithelial neoplasias (PanINs) at later stages. Paradoxically, however, NEMO deletion accelerated the progression of these fewer PanINs to PDAC and reduced median lifespan. Further, analysis of tissue microarrays from human PDAC sections highlighted the correlation between reduced NEMO expression in neoplastic cells and poorer prognosis, supporting our observation in mice. Mechanistically, NEMO deletion impeded oncogene-induced senescence (OIS), which is normally active in low-grade PanINs. This blockage resulted in fewer senescence-associated secretory phenotype (SASP) factors, reducing inflammation. However, blocked OIS fostered replication stress and DNA damage accumulation which accelerated PanIN progression to PDAC. Finally, treatment with the DNA damage-inducing reagent etoposide resulted in elevated cell death in NEMO-ablated PDAC cells compared to their NEMO-competent counterparts, indicative of a synthetic lethality paradigm. CONCLUSIONS: NEMO exhibited both oncogenic and tumor-suppressive properties during PDAC development. Caution is suggested in therapeutic interventions targeting NF-κB, which may be detrimental during PanIN progression but beneficial post-PDAC development.

Epithelial NEMO/IKKγ limits fibrosis and promotes regeneration during pancreatitis.

OBJECTIVE: Inhibitory κB kinase (IKK)/nuclear factor κB (NF-κB) signalling has been implicated in the pathogenesis of pancreatitis, but its precise function has remained controversial. Here, we analyse the contribution of IKK/NF-κB signalling in epithelial cells to the pathogenesis of pancreatitis by targeting the IKK subunit NF-κB essential modulator (NEMO) (IKKγ), which is essential for canonical NF-κB activation. DESIGN: Mice with a targeted deletion of NEMO in the pancreas were subjected to caerulein pancreatitis. Pancreata were examined at several time points and analysed for inflammation, fibrosis, cell death, cell proliferation, as well as cellular differentiation. Human samples were used to corroborate findings established in mice. RESULTS: In acute pancreatitis, NEMO deletion in the pancreatic parenchyma resulted in minor changes during the early phase but led to the persistence of inflammatory and fibrotic foci in the recovery phase. In chronic pancreatitis, NEMO deletion aggravated inflammation and fibrosis, inhibited compensatory acinar cell proliferation, and enhanced acinar atrophy and acinar-ductal metaplasia. Gene expression analysis revealed sustained activation of profibrogenic genes and the CXCL12/CXCR4 axis in the absence of epithelial NEMO. In human chronic pancreatitis samples, the CXCL12/CXCR4 axis was activated as well, with CXCR4 expression correlating with the degree of fibrosis. The aggravating effects of NEMO deletion were attenuated by the administration of the CXCR4 antagonist AMD3100. CONCLUSIONS: Our results suggest that NEMO in epithelial cells exerts a protective effect during pancreatitis by limiting inflammation and fibrosis and improving acinar cell regeneration. The CXCL12/CXCR4 axis is an important mediator of that effect and may also be of importance in human chronic pancreatitis.

Functional IKK/NF-κB signaling in pancreatic stellate cells is essential to prevent autoimmune pancreatitis.

Pancreatic stellate cells (PSCs) are resident cells in the exocrine pancreas which contribute to pancreatic fibrogenesis and inflammation. Studies on NF-κB in pancreatitis so far focused mainly on the parenchymal and myeloid compartments. Here we show a protective immunomodulatory function of NF-κB in PSCs. Conditional deletion of NEMO (IKKγ) in PSCs leads to spontaneous pancreatitis with elevated circulating IgM, IgG and antinuclear autoantibodies (ANA) within 18 weeks. When further challenged with caerulein, NEMOΔCol1a2 mice show an exacerbated autoimmune phenotype characterized by increased infiltration of eosinophils, B and T lymphocytes with reduced latency period. Transcriptomic profiling shows that NEMOΔCol1a2 mice display molecular signatures resembling autoimmune pancreatitis patients. Mechanistically, we show that PSCΔNEMO cells produce high levels of CCL24 ex vivo which contributes to eosinophil recruitment, as neutralization with a CCL24 antibody abolishes the transwell migration of eosinophils. Our findings uncover an unexpected immunomodulatory role specifically of NF-κB in PSCs during pancreatitis.

Deletion of NEMO Inhibits EMT and Reduces Metastasis in KPC Mice.

Pancreatic ductal adenocarcinoma (PDAC) remains a largely incurable cancer type. Its high mortality is attributed to the lack of efficient biomarkers for early detection combined with its high metastatic properties. The aim of our study was to investigate the role of NF-κB signaling in the development and metastasis of PDAC. We used the well-established KPC mouse model, and, through genetic manipulation, we deleted NF-κB essential modulator (NEMO) in the pancreata of KPC mice. Interestingly, NEMO deletion altered the differentiation status of the primary tumor but did not significantly affect its development. However, in the absence of NEMO, the median survival of the mice was prolonged by 13.5 days (16%). In addition, examination of the liver demonstrated that, whereas KPC mice occasionally developed liver macro-metastasis, NEMO deletion completely abrogated this outcome. Further analysis of the tumor revealed that the expression of epithelial-mesenchymal transition (EMT) transcription factors was diminished in the absence of NEMO. Conclusively, our study provides evidence that NF-κB is dispensable for the progression of high-grade PanINs towards PDAC. In contrast, NF-κB signaling is essential for the development of metastasis by regulating the gene expression program of EMT.

Block of NF-kB signaling accelerates MYC-driven hepatocellular carcinogenesis and modifies the tumor phenotype towards combined hepatocellular cholangiocarcinoma.

Primary liver cancer ranks among the leading causes of cancer death worldwide. Risk factors are closely linked to inflammation, such as viral hepatitis and alcoholic as well as non-alcoholic steatohepatitis. Among the pathways involved in the pathogenesis of malignant liver tumors, dysregulation of NF-κB signaling plays a prominent role. It provides a link between inflammation and cancer. To examine the role of NF-κB in a MYC-induced model of hepatocellular carcinoma we deleted NEMO (IKKγ) specifically from hepatocytes. NEMO deletion accelerated tumor development and shortened survival, suggesting a tumor-suppressive function of NF-κB signaling. We observed increased proliferation, inflammation and fibrosis, as well as activation of MAPK and STAT signaling. Importantly, deletion of NEMO modified the tumor phenotype from hepatocellular carcinoma to combined hepatocellular cholangiocarcinoma. The intrahepatic cholangiocarcinoma tumor component showed increased expression of progenitor markers such as Sox9 and reduced expression of mature hepatic markers such as CPS1. In both cases tumorigenesis was reversible by turning off MYC expression. To our knowledge this is the first mouse model of combined hepatocellular cholangiocarcinoma and may provide insights into the development of this rare malignant tumor.