Abstract

Simple SummaryThe incidence of pancreatic cancer is increasing but there has been little progress in the diagnosis and survival rates of this lethal cancer for decades. Understanding the biological mechanisms and defining how pancreatic cancer develops from normal pancreas tissue, to early lesions and then tumor is vital in developing better treatment options. Unrelenting inflammation in the pancreas significantly increases the risk of developing precursor lesions which result in pancreatic cancer. This inflammatory environment can result in the “switching on” of signaling pathways in the pancreas that influences many factors such as cell survival and turnover involved in tumor initiation, development and spread. In this review we discuss in detail how components of one such pathway, the NF-κB signaling network, are involved at various stages of pancreatic cancer development and in the cellular milieu of this cancer. We also discuss how this signaling pathway could be potentially “switched off” or regulated using new inhibitors and how these agents may be coupled with conventional and/or other therapies for better patient treatment outcomes.Pancreatic Ductal Adenocarcinoma (PDAC) is one of the world’s most lethal cancers. An increase in occurrence, coupled with, presently limited treatment options, necessitates the pursuit of new therapeutic approaches. Many human cancers, including PDAC are initiated by unresolved inflammation. The transcription factor NF-κB coordinates many signals that drive cellular activation and proliferation during immunity but also those involved in inflammation and autophagy which may instigate tumorigenesis. It is not surprising therefore, that activation of canonical and non-canonical NF-κB pathways is increasingly recognized as an important driver of pancreatic injury, progression to tumorigenesis and drug resistance. Paradoxically, NF-κB dysregulation has also been shown to inhibit pancreatic inflammation and pancreatic cancer, depending on the context. A pro-oncogenic or pro-suppressive role for individual components of the NF-κB pathway appears to be cell type, microenvironment and even stage dependent. This review provides an outline of NF-κB signaling, focusing on the role of the various NF-κB family members in the evolving inflammatory PDAC microenvironment. Finally, we discuss pharmacological control of NF-κB to curb inflammation, focussing on novel anti-cancer agents which reinstate the process of cancer cell death, the Smac mimetics and their pre-clinical and early clinical trials.

Highlights

  • Pancreatic cancers are associated with a poor prognosis and are one of the leading causes of cancer mortality worldwide [1,2,3]

  • Cancers of the pancreas are mainly divided into two types; stromal-rich pancreatic ductal adenocarcinomas (PDAC), arising from the pancreatic exocrine tissue and pancreatic neuroendocrine tumors emanating from pancreatic endocrine tissue (PanNET, less than 5% of pancreatic cancers) [10]

  • Additional studies have shown that induction of autophagy mediated by OPN/NF-κB signaling is required for maintenance of PDAC stem cell activity and combination of gemcitabine with pharmacological autophagy inhibitors (NF-κB inhibitors) could be a promising therapeutic strategy [176,180]

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Summary

Introduction

Pancreatic cancers are associated with a poor prognosis and are one of the leading causes of cancer mortality worldwide [1,2,3]. There are strong non-modifiable familial and specific syndrome risk factors (e.g., Lynch syndrome [2,10]) for PDAC, that are associated with certain genetic variations or mutations [6,7,11] These only account for 5–10% of new cases [12,13]. Recent modifications of chemotherapy combination treatment regimens, such as FOLFIRINOX [31] have modestly increased 5 year survival rates [31,32,33,34,35] Immunotherapies such as immune checkpoint blockade or engineered (CAR) T cells have been efficacious in certain sub-groups of cancer patients but to date have been disappointing for PDAC [36,37,38]. While much is known about the NFκB family of proteins, how this is translates in a cell-type specific and cellular context dependent manner, and how sustained NF-κB activation can lead to nascent tumorigenesis are still far from completely understood

The NF-κB Family
Downstream Signaling of Canonical and Non-Canonical NF-κB Activation
NF-κB and Pancreatic Inflammation
Pancreatitis Elevates the Risk for PDAC Development
NF-κB Promotor or Inhibitor of Pancreatitis?
The Role of NF-κB in Various Facets of PDAC Biology
NF-κB and Angiogenesis
Metastasis and NF-κB
NF-κB and Chemotherapeutic Drug Resistance
An Emerging Role for NF-κB in the Tumor Microenvironment
NF-κB and Myeloid Subsets in PDAC
NF-κB and Tregs
Generalized Anti-Inflammatories
Direct Inhibition of NF-κB or NF-κB Subunits
TNFR Pathway Inhibitors
Other Modes of NF-κB Inhibition and Combination Therapy
Findings
Conclusions
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