TRAIL/NF-κB/CX3CL1 Mediated Onco-Immuno Crosstalk Leading to TRAIL Resistance of Pancreatic Cancer Cell Lines

Mechanisms underlying reversed TRAIL sensitivity in acquired bortezomib-resistant non-small cell lung cancer cells

Aim: The therapeutic targeting of the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) death receptors in cancer, including non-small cell lung cancer (NSCLC), is a widely studied approach for tumor selective apoptotic cell death therapy. However, apoptosis resistance is often encountered. The main aim of this study was to investigate the apoptotic mechanism underlying TRAIL sensitivity in three bortezomib (BTZ)-resistant NSCLC variants, combining induction of both the intrinsic and extrinsic pathways. Methods: Sensitivity to TRAIL in BTZ-resistant variants was determined using a tetrazolium (MTT) and a clonogenic assay. A RT-qPCR profiling mRNA array was used to determine apoptosis pathway-specific gene expression. The expression of these proteins was determined through ELISA assays and western Blotting, while apoptosis (sub-G1) and cytokine expression were determined using flow cytometry. Apoptotic genes were silenced by specific siRNAs. Lipid rafts were isolated with fractional ultracentrifugation. Results: A549BTZR (BTZ-resistant) cells were sensitive to TRAIL in contrast to parental A549 cells, which are resistant to TRAIL. TRAIL-sensitive H460 cells remained equally sensitive for TRAIL as H460BTZR. In A549BTZR cells, we identified an increased mRNA expression of TNFRSF11B [osteoprotegerin (OPG)] and caspase-1, -4 and -5 mRNAs involved in cytokine activation and immunogenic cell death. Although the OPG, interleukin-6 (IL-6), and interleukin-8 (IL-8) protein levels were markedly enhanced (122-, 103-, and 11-fold, respectively) in the A549BTZR cells, this was not sufficient to trigger TRAIL-induced apoptosis in the parental A549 cells. Regarding the extrinsic apoptotic pathway, the A549BTZR cells showed TRAIL-R1-dependent TRAIL sensitivity. The shift of TRAIL-R1 from non-lipid into lipid rafts enhanced TRAIL-induced apoptosis. In the intrinsic apoptotic pathway, a strong increase in the mRNA and protein levels of the anti-apoptotic myeloid leukemia cell differentiation protein (Mcl-1) and B-cell leukemia/lymphoma 2 (Bcl-2) was found, whereas the B-cell lymphoma-extra large (Bcl-xL) expression was reduced. However, the stable overexpression of Bcl-xL in the A549BTZR cells did not reverse the TRAIL sensitivity in the A549BTZR cells, but silencing of the BH3 Interacting Domain Death Agonist (BID) protein demonstrated the importance of the intrinsic apoptotic pathway, regardless of Bcl-xL. Conclusion: In summary, increased sensitivity to TRAIL-R1 seems predominantly related to the relocalization into lipid rafts and increased extrinsic and intrinsic apoptotic pathways.

TNF-Related Apoptosis-Inducing Ligand: Non-Apoptotic Signalling

TNF-related apoptosis-inducing ligand (TRAIL or Apo2 or TNFSF10) belongs to the TNF superfamily. When bound to its agonistic receptors, TRAIL can induce apoptosis in tumour cells, while sparing healthy cells. Over the last three decades, this tumour selectivity has prompted many studies aiming at evaluating the anti-tumoral potential of TRAIL or its derivatives. Although most of these attempts have failed, so far, novel formulations are still being evaluated. However, emerging evidence indicates that TRAIL can also trigger a non-canonical signal transduction pathway that is likely to be detrimental for its use in oncology. Likewise, an increasing number of studies suggest that in some circumstances TRAIL can induce, via Death receptor 5 (DR5), tumour cell motility, potentially leading to and contributing to tumour metastasis. While the pro-apoptotic signal transduction machinery of TRAIL is well known from a mechanistic point of view, that of the non-canonical pathway is less understood. In this study, we the current state of knowledge of TRAIL non-canonical signalling.

Microglia govern the extinction of acute stress-induced anxiety-like behaviors in male mice

Anxiety-associated symptoms following acute stress usually become extinct gradually within a period of time. However, the mechanisms underlying how individuals cope with stress to achieve the extinction of anxiety are not clear. Here we show that acute restraint stress causes an increase in the activity of GABAergic neurons in the CeA (GABACeA) in male mice, resulting in anxiety-like behaviors within 12 hours; meanwhile, elevated GABACeA neuronal CX3CL1 secretion via MST4 (mammalian sterile-20-like kinase 4)-NF-κB-CX3CL1 signaling consequently activates microglia in the CeA. Activated microglia in turn inhibit GABACeA neuronal activity via the engulfment of their dendritic spines, ultimately leading to the extinction of anxiety-like behaviors induced by restraint stress. These findings reveal a dynamic molecular and cellular mechanism in which microglia drive a negative feedback to inhibit GABACeA neuronal activity, thus facilitating maintenance of brain homeostasis in response to acute stress.

Silencing TRIM29 Sensitizes Non-small Cell Lung Cancer Cells to Anlotinib by Promoting Apoptosis via Binding RAD50

BACKGROUND

Previous studies have proposed that the transcriptional regulatory factor tripartite motif containing 29 (TRIM29) is involved in carcinogenesis via binding with nucleic acid. TRIM29 is confirmed to be highly expressed when the cancer cells acquire therapy-resistant properties. We noticed that TRIM29 levels were significantly increased in anlotinib-resistant NCIH1975 (NCI-H1975/AR) cells via mining data information from gene expression omnibus (GEO) gene microarray (GSE142031; log2 fold change > 1, p < 0.05).

OBJECTIVE

Our study aimed to investigate the function of TRIM29 on the resistance to anlotinib in non-small cell lung cancer (NSCLC) cells, including NCI-H1975 and A549 cells.

METHODS

Real-time RT-PCR and western blot were used to detect TRIM29 expression in anlotinib- resistant NSCLC (NSCLC/AR) cells. Apoptosis were determined through flow cytometry, acridine orange/ethidium bromide staining as well as western blot. ELISA was used to measure the content of C-X3-C motif chemokine ligand 1. Co-Immunoprecipitation assay was performed to verify the interaction between TRIM29 and RAD50 double-strand break repair protein (RAD50).

RESULTS

TRIM29 expression was shown to be elevated in the cytoplasm and nucleus of NSCLC/ AR cells compared to normal NSCLC cells. Next, we demonstrated that TRIM29 knockdown facilitated apoptosis and enhanced the sensitivity to anlotinib in NSCLC/AR cells. Based on the refined results citing from the database BioGRID, it was proved that TRIM29 interacted with RAD50. Herein, RAD50 overexpression diminished the pro-apoptotic effect induced by silencing TRIM29 in anlotinib-resistant A549 (A549/AR) cells.

CONCLUSION

Finally, we concluded that the increased sensitivity to anlotinib in NSCLC/AR cells was achieved by knocking down TRIM29, besides, the positive effects of TRIM29 knockdown were attributed to the promotion of apoptosis via binding to RAD50 in NSCLC/AR cell nucleus. Therefore, TRIM29 might become a potential target for overcoming anlotinib resistance in NSCLC treatment.

NF-κB and Pancreatic Cancer; Chapter and Verse

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.

Vertebral-specific activation of the CX3CL1/ICAM-1 signaling network mediates non-small-cell lung cancer spinal metastasis by engaging tumor cell-vertebral bone marrow endothelial cell interactions

Rationale: The spine is one of the most common metastatic sites of non-small cell lung cancer (NSCLC), and NSCLC spinal metastasis results in serious consequences. Metastatic extravasation of disseminated cancer cells including increased invasiveness, adhesion and transendothelial migration is crucial for tumor metastasis. This study aimed to investigate the mechanisms underlying NSCLC spinal metastasis based on the C-X3-C motif chemokine ligand 1- (CX3CL1) and intercellular adhesion molecule-1- (ICAM-1) mediated signaling network. Methods: Immunohistochemistry, western blotting, and reverse transcription-quantitative PCR were conducted to detect the distribution of CX3CL1/ICAM-1 in different organs. Transwell, adhesion, and transendothelial migration assays were performed to evaluate the regulatory effects of CX3CL1/ICAM-1 on NSCLC cell invasion, adhesion, and transendothelial migration in vitro. A spontaneous spinal metastasis mouse model was established via injection of NSCLC cells into the left cardiac ventricle of NOD/SCID mice. The effects of CX3CL1/ICAM-1 on NSCLC spinal metastasis in vivo were validated using bioluminescent, micro-computerized tomography, immunohistochemistry and histological analyses. Results: CX3CL1 expression was specifically higher in vertebral bone compared with limb bones and lung tissue, and was associated with NSCLC spinal metastasis. Mechanically, vertebral bone marrow endothelial cells (VBMECs) enhanced NSCLC cell invasion via CX3CL1 signaling-mediated activation of the PI3K/AKT pathway. Furthermore, we found that VBMECs effectively induced ICAM-1-dependent NSCLC cell adhesion in coordination with platelets through the CX3CL1/ICAM-1/LFA-1 pathway. Meanwhile, CX3CL1 enhanced NSCLC cell transendothelial migration by increasing permeability of VBMECs via ICAM-1-dependent activation of the Src/GEF-H1 pathway. Interestingly, NSCLC cells were indicated to promote CX3CL1 secretion of VBMECs through MAPK14/ADMA17-dependent CX3CL1 release and NF-κB-dependent CX3CL1 synthesis. Based on these findings, we revealed a novel feedback cycle between circulating NSCLC cells and VBMECs mediated by CX3CL1/ICAM-1 signaling. Further disengagement of the CX3CL1/ICAM-1-mediated feedback cycle in vivo significantly restricted metastasis and prolonged mouse survival. Conclusions: Our results indicated a unique feedback cycle between circulating NSCLC cells and VBMECs mediated by CX3CL1/ICAM-1 signaling, which is necessary for NSCLC spinal metastasis. This work provides a new perspective for underlying the mechanisms of NSCLC spinal metastasis and indicates potential novel targets for the prevention of NSCLC spinal metastasis.

Research trends in pharmacological modulation of tumor-associated macrophages

As one of the most abundant immune cell populations in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play important roles in multiple solid malignancies, including breast cancer, prostate cancer, liver cancer, lung cancer, ovarian cancer, gastric cancer, pancreatic cancer, and colorectal cancer. TAMs could contribute to carcinogenesis, neoangiogenesis, immune-suppressive TME remodeling, cancer chemoresistance, recurrence, and metastasis. Therefore, reprogramming of the immune-suppressive TAMs by pharmacological approaches has attracted considerable research attention in recent years. In this review, the promising pharmaceutical targets, as well as the existing modulatory strategies of TAMs were summarized. The chemokine-chemokine receptor signaling, tyrosine kinase receptor signaling, metabolic signaling, and exosomal signaling have been highlighted in determining the biological functions of TAMs. Besides, both preclinical research and clinical trials have suggested the chemokine-chemokine receptor blockers, tyrosine kinase inhibitors, bisphosphonates, as well as the exosomal or nanoparticle-based targeting delivery systems as the promising pharmacological approaches for TAMs deletion or reprogramming. Lastly, the combined therapies of TAMs-targeting strategies with traditional treatments or immunotherapies as well as the exosome-like nanovesicles for cancer therapy are prospected.

Stem Cells and Organoid Technology in Precision Medicine in Inflammation: Are We There Yet?

Individualised cellular models of disease are a key tool for precision medicine to recapitulate chronic inflammatory processes. Organoid models can be derived from induced pluripotent stem cells (iPSCs) or from primary stem cells ex vivo. These models have been emerging over the past decade and have been used to reconstruct the respective organ-specific physiology and pathology, at an unsurpassed depth. In cancer research, patient-derived cancer organoids opened new perspectives in predicting therapy response and provided novel insights into tumour biology. In precision medicine of chronic inflammatory disorders, stem-cell based organoid models are currently being evaluated in pre-clinical pharmacodynamic studies (clinical studies in a dish) and are employed in clinical studies, e.g., by re-transplanting autologous epithelial organoids to re-establish intestinal barrier integrity. A particularly exciting feature of iPSC systems is their ability to provide insights into organ systems and inflammatory disease processes, which cannot be monitored with clinical biopsies, such as immune reactions in neurodegenerative disorders. Refinement of differentiation protocols, and next-generation co-culturing methods, aimed at generating self-organised, complex tissues in vitro, will be the next logical steps. In this mini-review, we critically discuss the current state-of-the-art stem cell and organoid technologies, as well as their future impact, potential and promises in combating immune-mediated chronic diseases.

Targets (Metabolic Mediators) of Therapeutic Importance in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The higher mortality in PDAC is often attributed to the inability to detect it until it has reached advanced stages. The major challenge in tackling PDAC is due to its elusive pathology, minimal effectiveness, and resistance to existing therapeutics. The aggressiveness of PDAC is due to the capacity of tumor cells to alter their metabolism, utilize the diverse available fuel sources to adapt and grow in a hypoxic and harsh environment. Therapeutic resistance is due to the presence of thick stroma with poor angiogenesis, thus making drug delivery to tumor cells difficult. Investigating the metabolic mediators and enzymes involved in metabolic reprogramming may lead to the identification of novel therapeutic targets. The metabolic mediators of glucose, glutamine, lipids, nucleotides, amino acids and mitochondrial metabolism have emerged as novel therapeutic targets. Additionally, the role of autophagy, macropinocytosis, lysosomal transport, recycling, amino acid transport, lipid transport, and the role of reactive oxygen species has also been discussed. The role of various pro-inflammatory cytokines and immune cells in the pathogenesis of PDAC and the metabolites involved in the signaling pathways as therapeutic targets have been previously discussed. This review focuses on the therapeutic potential of metabolic mediators in PDAC along with stemness due to metabolic alterations and their therapeutic importance.

STK3 Suppresses Ovarian Cancer Progression by Activating NF-κB Signaling to Recruit CD8+ T-Cells

Serine/threonine protein kinase-3 (STK3) is a critical molecule of the Hippo pathway but little is known about its biological functions in the ovarian cancer development. We demonstrated the roles of STK3 in ovarian cancer. Existing databases were used to study the expression profile of STK3. STK3 was significantly downregulated in OC patients, and the low STK3 expression was correlated with a poor prognosis. In vitro cell proliferation, apoptosis, and migration assays, and in vivo subcutaneous xenograft tumor models were used to determine the roles of STK3. The overexpression of STK3 significantly inhibited cell proliferation, apoptosis, and migration of ovarian cancer cells in vitro and tumor growth in vivo. Bisulfite sequencing PCR analysis was performed to validate the methylation of STK3 in ovarian cancer. RNA sequencing and gene set enrichment analysis (GSEA) were used to compare the transcriptome changes in the STK3 overexpression ovarian cancer and control cells. The signaling pathway was analyzed by western blotting. STK3 promoted the migration of CD8⁺ T-cells by activating nuclear transcription factor κB (NF-κB) signaling. STK3 is a potential predictor of OC. It plays an important role in suppressing tumor growth of ovarian cancer and in chemotaxis of CD8⁺ T-cells.

Clinical significance of expression level of CX3CL1-CX3CR1 axis in bone metastasis of lung cancer

PURPOSE

To investigate the clinical significance of CX3 chemokine ligand 1(CX3CL1) and CX3CR1 in patients with bone metastasis from lung cancer. The expression levels of CX3CL1 and CX3CR1 mRNA and protein in primary lung cancer and lung cancer bone metastasis were detected by qRT-PCR and Western blot.

METHODS

One hundred patients with lung cancer were divided into a boneless metastasis group (50 patients with bone metastasis) and a bone metastasis group (50 patients without distant metastasis). The bone transfer component was graded by Soloway classification (0 to III). The expression levels of serum CX3CL1-CX3CR1 axis were detected by enzyme-linked immunosorbent assay (ELISA). RT-qPCR and Western Blot were used to verify the transfection efficiency. The scratching assay was used to detect the migration of CX3CL1 to 95-D cells after down-regulating the expression of CX3CR1.

RESULTS

The expression levels of CX3CL1 and CX3CR1 mRNA and protein in the primary lung cancer and lung cancer bone metastasis were significantly higher than those in the adjacent tissues (P < 0.0001). The levels of serum CX3CL1 and CX3CR1 in bone metastasis group were significantly higher than those in boneless metastasis group and healthy control group (P < 0.05). In the bone metastasis group, the levels of serum CX3CL1 and CX3CR1 were significantly positively correlated with the degree of disease progression (P < 0.01).

CONCLUSION

The expression level of serum CX3CL1-CX3CR1 axis is expected to be an auxiliary reference index for monitoring bone metastasis of lung cancer.

Fractalkine/CX3CL1 in Neoplastic Processes

Fractalkine/CX3C chemokine ligand 1 (CX3CL1) is a chemokine involved in the anticancer function of lymphocytes-mainly NK cells, T cells and dendritic cells. Its increased levels in tumors improve the prognosis for cancer patients, although it is also associated with a poorer prognosis in some types of cancers, such as pancreatic ductal adenocarcinoma. This work focuses on the 'hallmarks of cancer' involving CX3CL1 and its receptor CX3CR1. First, we describe signal transduction from CX3CR1 and the role of epidermal growth factor receptor (EGFR) in this process. Next, we present the role of CX3CL1 in the context of cancer, with the focus on angiogenesis, apoptosis resistance and migration and invasion of cancer cells. In particular, we discuss perineural invasion, spinal metastasis and bone metastasis of cancers such as breast cancer, pancreatic cancer and prostate cancer. We extensively discuss the importance of CX3CL1 in the interaction with different cells in the tumor niche: tumor-associated macrophages (TAM), myeloid-derived suppressor cells (MDSC) and microglia. We present the role of CX3CL1 in the development of active human cytomegalovirus (HCMV) infection in glioblastoma multiforme (GBM) brain tumors. Finally, we discuss the possible use of CX3CL1 in immunotherapy.

Regulation of pancreatic cancer TRAIL resistance by protein O-GlcNAcylation

TRAIL-activating therapy is promising in treating various cancers, including pancreatic cancer, a highly malignant neoplasm with poor prognosis. However, many pancreatic cancer cells are resistant to TRAIL-induced apoptosis despite their expression of intact death receptors (DRs). Protein O-GlcNAcylation is a versatile posttranslational modification that regulates various biological processes. Elevated protein O-GlcNAcylation has been recently linked to cancer cell growth and survival. In this study, we evaluated the role of protein O-GlcNAcylation in pancreatic cancer TRAIL resistance, and identified higher levels of O-GlcNAcylation in TRAIL-resistant pancreatic cancer cells. With gain- and loss-of-function of the O-GlcNAc-adding enzyme, O-GlcNActransferase (OGT), we determined that increasing O-GlcNAcylation rendered TRAIL-sensitive cells more resistant to TRA-8-induced apoptosis, while inhibiting O-GlcNAcylation promoted TRA-8-induced apoptosis in TRAIL-resistance cells. Furthermore, we demonstrated that OGT knockdown sensitized TRAIL-resistant cells to TRA-8 therapy in a mouse model in vivo. Mechanistic studies revealed direct O-GlcNAc modifications of DR5, which regulated TRA-8-induced DR5 oligomerization. We further defined that DR5 O-GlcNAcylation was independent of FADD, the adapter protein for the downstream death-inducing signaling. These studies have demonstrated an important role of protein O-GlcNAcylation in regulating TRAIL resistance of pancreatic cancer cells; and uncovered the contribution of O-GlcNAcylation to DR5 oligomerization and thus mediating DR-inducing signaling.

Stress Management: Death Receptor Signalling and Cross-Talks with the Unfolded Protein Response in Cancer

Throughout tumour progression, tumour cells are exposed to various intense cellular stress conditions owing to intrinsic and extrinsic cues, to which some cells are remarkably able to adapt. Death Receptor (DR) signalling and the Unfolded Protein Response (UPR) are two stress responses that both regulate a plethora of outcomes, ranging from proliferation, differentiation, migration, cytokine production to the induction of cell death. Both signallings are major modulators of physiological tissue homeostasis and their dysregulation is involved in tumorigenesis and the metastastic process. The molecular determinants of the control between the different cellular outcomes induced by DR signalling and the UPR in tumour cells and their stroma and their consequences on tumorigenesis are starting to be unravelled. Herein, I summarize the main steps of DR signalling in relation to its cellular and pathophysiological roles in cancer. I then highlight how the UPR and DR signalling control common cellular outcomes and also cross-talk, providing potential opportunities to further understand the development of malignancies.

Macrophage and Tumor Cell Cross-Talk Is Fundamental for Lung Tumor Progression: We Need to Talk

Regardless of the promising results of certain immune checkpoint blockers, current immunotherapeutics have met a bottleneck concerning response rate, toxicity, and resistance in lung cancer patients. Accumulating evidence forecasts that the crosstalk between tumor and immune cells takes center stage in cancer development by modulating tumor malignancy, immune cell infiltration, and immune evasion in the tumor microenvironment (TME). Cytokines and chemokines secreted by this crosstalk play a major role in cancer development, progression, and therapeutic management. An increased infiltration of Tumor-associated macrophages (TAMs) was observed in most of the human cancers, including lung cancer. In this review, we emphasize the role of cytokines and chemokines in TAM-tumor cell crosstalk in the lung TME. Given the role of cytokines and chemokines in immunomodulation, we propose that TAM-derived cytokines and chemokines govern the cancer-promoting immune responses in the TME and offer a new immunotherapeutic option for lung cancer treatment.

CX3CL1 Signaling in the Tumor Microenvironment

CX3CL1 (Fractalkine) is a multifunctional inflammatory chemokine with a single receptor CX3CR1. The biological effects elicited by CX3CL1 on surrounding cells vary depending on a number of factors including its structure, the expression pattern of CX3CR1, and the cell type. For instance, the transmembrane form of CX3CL1 primarily serves as an adhesion molecule, but when cleaved to a soluble form, CX3CL1 predominantly functions as a chemotactic cytokine (Fig. 1.1). However, the biological functions of CX3CL1 also extend to immune cell survival and retention. The pro-inflammatory nature of CX3CR1-expressing immune cells place the CX3CL1:CX3CR1 axis as a central player in multiple inflammatory disorders and position this chemokine pathway as a potential therapeutic target. However, the emerging role of this chemokine pathway in the maintenance of effector memory cytotoxic T cell populations implicates it as a key chemokine in anti-viral and anti-tumor immunity, and therefore an unsuitable therapeutic target in inflammation. The reported role of CX3CL1 as a key regulator of cytotoxic T cell-mediated immunity is supported by several studies that demonstrate CX3CL1 as an important TIL-recruiting chemokine and a positive prognostic factor in colorectal, breast, and lung cancer. Such reports are conflicting with an overwhelming number of studies demonstrating a pro-tumorigenic and pro-metastatic role of CX3CL1 across multiple blood and solid malignancies.This chapter will review the unique structure, function, and biology of CX3CL1 and address the diversity of its biological effects in the immune system and the tumor microenvironment. Overall, this chapter highlights how we have just scratched the surface of CX3CL1's capabilities and suggests that further in-depth and mechanistic studies incorporating all CX3CL1 interactions must be performed to fully appreciate its role in cancer and its potential as a therapeutic target.

NF-κB Dependent Chemokine Signaling in Pancreatic Cancer

Pancreatic cancer is one of the carcinomas with the worst prognoses, as shown by its five-year survival rate of 9%. Although there have been new therapeutic innovations, the effectiveness of these therapies is still limited, resulting in pancreatic ductal adenocarcinoma (PDAC) becoming the second leading cause of cancer-related death in 2020 in the US. In addition to tumor cell intrinsic resistance mechanisms, this disease exhibits a complex stroma consisting of fibroblasts, immune cells, neuronal and vascular cells, along with extracellular matrix, all conferring therapeutic resistance by several mechanisms. The NF-κB pathway is involved in both the tumor cell-intrinsic and microenvironment-mediated therapeutic resistance by regulating the transcription of a plethora of target genes. These genes are involved in nearly all scenarios described as the hallmarks of cancer. In addition to classical regulators of apoptosis, NF-κB regulates the expression of chemokines and their receptors, both in the tumor cells and in cells of the microenvironment. These chemokines mediate autocrine and paracrine loops among tumor cells but also cross-signaling between tumor cells and the stroma. In this review, we will focus on NF-κB-mediated chemokine signaling, with an emphasis on therapy resistance in pancreatic cancer.

NF-κB Signaling in Targeting Tumor Cells by Oncolytic Viruses-Therapeutic Perspectives

In recent years, oncolytic virotherapy became a promising therapeutic approach, leading to the introduction of a novel generation of anticancer drugs. However, despite evoking an antitumor response, introducing an oncolytic virus (OV) to the patient is still inefficient to overcome both tumor protective mechanisms and the limitation of viral replication by the host. In cancer treatment, nuclear factor (NF)-κB has been extensively studied among important therapeutic targets. The pleiotropic nature of NF-κB transcription factor includes its involvement in immunity and tumorigenesis. Therefore, in many types of cancer, aberrant activation of NF-κB can be observed. At the same time, the activity of NF-κB can be modified by OVs, which trigger an immune response and modulate NF-κB signaling. Due to the limitation of a monotherapy exploiting OVs only, the antitumor effect can be enhanced by combining OV with NF-κB-modulating drugs. This review describes the influence of OVs on NF-κB activation in tumor cells showing NF-κB signaling as an important aspect, which should be taken into consideration when targeting tumor cells by OVs.