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.

Nucleolar TFIIE plays a role in ribosomal biogenesis and performance.

Ribosome biogenesis is a highly energy-demanding process in eukaryotes which requires the concerted action of all three RNA polymerases. In RNA polymerase II transcription, the general transcription factor TFIIH is recruited by TFIIE to the initiation site of protein-coding genes. Distinct mutations in TFIIH and TFIIE give rise to the degenerative disorder trichothiodystrophy (TTD). Here, we uncovered an unexpected role of TFIIE in ribosomal RNA synthesis by RNA polymerase I. With high resolution microscopy we detected TFIIE in the nucleolus where TFIIE binds to actively transcribed rDNA. Mutations in TFIIE affects gene-occupancy of RNA polymerase I, rRNA maturation, ribosomal assembly and performance. In consequence, the elevated translational error rate with imbalanced protein synthesis and turnover results in an increase in heat-sensitive proteins. Collectively, mutations in TFIIE-due to impaired ribosomal biogenesis and translational accuracy-lead to a loss of protein homeostasis (proteostasis) which can partly explain the clinical phenotype in TTD.

Crosstalk between Tumor and Stromal Cells in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) remains a lethal cancer. The poor prognosis calls for a more detailed understanding of disease biology in order to pave the way for the development of effective therapies. Typically, the pancreatic tumor is composed of a minority of malignant cells within an excessive tumor microenvironment (TME) consisting of extracellular matrix (ECM), fibroblasts, immune cells, and endothelial cells. Research conducted in recent years has particularly focused on cancer-associated fibroblasts (CAFs) which represent the most prominent cellular component of the desmoplastic stroma. Here, we review the complex crosstalk between CAFs, tumor cells, and other components of the TME, and illustrate how these interactions drive disease progression. We also discuss the emerging field of CAF heterogeneity, their tumor-supportive versus tumor-suppressive capacity, and the consequences for designing stroma-targeted therapies in the future.

Accelerated aging in mice with astrocytic redox imbalance as a consequence of SOD2 deletion.

Aging of the central nervous system (CNS) leads to motoric and cognitive decline and increases the probability for neurodegenerative disease development. Astrocytes fulfill central homeostatic functions in the CNS including regulation of immune responses and metabolic support of neurons and oligodendrocytes. In this study, we investigated the effect of redox imbalance in astrocytes by using a conditional astrocyte-specific SOD2-deficient mouse model (SOD2ako ) and analyzed these animals at different stages of their life. SOD2ako mice did not exhibit any overt phenotype within the first postnatal weeks. However, already as young adults, they displayed progressive motoric impairments. Moreover, as these mice grew older, they exhibited signs of a progeroid phenotype and early death. Histological analysis in moribund SOD2ako mice revealed the presence of age-related brain alterations, neuroinflammation, neuronal damage and myelin impairment in brain and spinal cord. Additionally, transcriptome analysis of primary astrocytes revealed that SOD2 deletion triggered a hypometabolic state and promoted polarization toward A1-neurotoxic status, possibly underlying the neuronal and myelin deficits. Conclusively, our study identifies maintenance of ROS homeostasis in astrocytes as a critical prerequisite for physiological CNS aging.

NF-κB is a critical mediator of post-mitotic senescence in oligodendrocytes and subsequent white matter loss.

BACKGROUND: Inflammaging represents an accepted concept where the immune system shifts to a low-grade chronic pro-inflammatory state without overt infection upon aging. In the CNS, inflammaging is mainly driven by glia cells and associated with neurodegenerative processes. White matter degeneration (WMD), a well-known process in the aging brain, manifests in myelin loss finally resulting in motor, sensory and cognitive impairments. Oligodendrocytes (OL) are responsible for homeostasis and maintenance of the myelin sheaths, which is a complex and highly energy demanding process sensitizing these cells to metabolic, oxidative and other forms of stress. Yet, the immediate impact of chronic inflammatory stress like inflammaging on OL homeostasis, myelin maintenance and WMD remains open. METHODS: To functionally analyze the role of IKK/NF-κB signaling in the regulation of myelin homeostasis and maintenance in the adult CNS, we established a conditional mouse model allowing NF-κB activation in mature myelinating oligodendrocytes. IKK2-CAPLP-CreERT2 mice were characterized by biochemical, immunohistochemical, ultrastructural and behavioral analyses. Transcriptome data from isolated, primary OLs and microglia cells were explored by in silico pathway analysis and validated by complementary molecular approaches. RESULTS: Chronic NF-κB activation in mature OLs leads to aggravated neuroinflammatory conditions phenocopying brain inflammaging. As a consequence, IKK2-CAPLP-CreERT2 mice showed specific neurological deficits and impaired motoric learning. Upon aging, persistent NF-κB signaling promotes WMD in these mice as ultrastructural analysis revealed myelination deficits in the corpus callosum accompanied by impaired myelin protein expression. RNA-Seq analysis of primary oligodendrocytes and microglia cells uncovers gene expression signatures associated with activated stress responses and increased post mitotic cellular senescence (PoMiCS) which was confirmed by elevated senescence-associated ß-galactosidase activity and SASP gene expression profile. We identified an elevated integrated stress response (ISR) characterized by phosphorylation of eIF2α as a relevant molecular mechanism which is able to affect translation of myelin proteins. CONCLUSIONS: Our findings demonstrate an essential role of IKK/NF-κB signaling in mature, post-mitotic OLs in regulating stress-induced senescence in these cells. Moreover, our study identifies PoMICS as an important driving force of age-dependent WMD as well as of traumatic brain injury induced myelin defects.

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.