The complexity of pancreatic ductal cancers and multidimensional strategies for therapeutic targeting

PAK4 inhibition significantly potentiates Gemcitabine activity in PDAC cells via inhibition of Wnt/β-catenin, p-ERK/MAPK and p-AKT/PI3K pathways

Pancreatic Ductal Adenocarcinoma (PDAC) remains one of the most difficult to treat cancers. Gemcitabine is still the standard of care treatment for PDAC but with modest survival benefit and well reported resistance. Here we explored potential of inhibiting p21 activated kinase 4 (PAK4), a downstream protein of KRAS oncogenic pathway, in combination with Gemcitabine in PDAC cells. PAK4 inhibition by KPT-9274 led to significant potentiation of Gemcitabine activity in PDAC cells, with an increase in apoptosis, DNA damage and cell cycle arrest. At molecular level, PAK4 inhibition dose dependently inhibited Gemcitabine-induced β-catenin, c-JUN and Ribonucleotide Reductase subunit 2 (RRM2) levels. PAK4 inhibition further inhibited levels of phosphorylated ERK (p-ERK); Gemcitabine-induced phosphorylated AKT (p-AKT), phosphorylated and total c-Myc. These results suggest possible role of β-catenin, p-ERK and p-AKT, key effector proteins of Wnt/β-catenin, MAPK and PI3K pathways respectively, in sensitisation of Gemcitabine activity with PAK4 inhibition. Our data unravel probable molecular mechanisms behind combination of PAK4 inhibition with Gemcitabine to counter PDAC, which may be unequivocally proved further with knock down of PAK4. Our findings provide a strong rationale to exploit the combination therapy of Gemcitabine and PAK4 inhibitor for PDAC at pre-clinical and clinical levels.

Identification and verification of CCNB1 as a potential prognostic biomarker by comprehensive analysis

As one of the most common types of pancreatic cancer, pancreatic ductal adenocarcinoma (PDAC) is highly invasive and lethal. This study aims to develop biomarkers and targets for the diagnosis and treatment of PDAC. Differentially expressed genes (DEGs) were screened via GEO2R, protein network was constructed through STRING and Cytoscape. Functional enrichment analysis was performed, followed by survival analysis and expression validation. A total of 115 DEGs were identified, including 108 upregulated and 7 downregulated genes. After enrichment, survival analysis, one potential gene, Cyclin B1 (CCNB1), was selected for further expression verification at the mRNA and protein level. Taker together, CCNB1 may act as a potential biomarker which provided new idea for elucidation of the pathogenesis of PDAC.

Natural killer T cell immunotherapy combined with IL-15-expressing oncolytic virotherapy and PD-1 blockade mediates pancreatic tumor regression

BACKGROUND

Pancreatic cancer is one of the leading causes of cancer death, with a 5-year -year survival rate of less than 10%. This results from late detection, high rates of metastasis, and resistance to standard chemotherapies. Furthermore, chemotherapy and radiation are associated with significant morbidity, underscoring the need for novel therapies. Recent clinical studies have shown that immunotherapies can provide durable outcomes in cancer patients, but successes in pancreatic cancer have been limited. It is likely that novel and combined therapies will be needed to achieve clinical benefits.

METHODS

Using experimental mouse models of pancreatic ductal adenocarcinoma, we examined natural killer T (NKT) cell activation therapy in combination with a recombinant oncolytic vesicular stomatitis virus (VSVΔM51) engineered to express the cytokine IL-15 (VSV-IL-15). Panc02 pancreatic ductal carcinoma cells were implanted subcutaneously or orthotopically into syngeneic C57BL/6 mice. Mice were then treated with VSV expressing green fluorescent protein (VSV-GFP) or VSV-IL-15 and/or NKT cell activation therapy via delivery of α-GalCer-loaded DCs. We further assessed whether the addition of PD-1 blockade could increase the therapeutic benefit of our combination treatment. Three days after NKT cell activation, some groups of mice were treated with anti-PD-1 antibodies weekly for 3 weeks.

RESULTS

VSV-GFP and VSV-IL-15 mediated equal killing of human and mouse pancreatic cancer lines in vitro. In vivo, VSV-IL-15 combined with NKT cell activation therapy to enhance tumor regression and increase survival time over individual treatments, and was also superior to NKT cell therapy combined with VSV-GFP. Enhanced tumor control was associated with increased immune cell infiltration and anti-tumor effector functions (cytotoxicity and cytokine production). While ineffective as a monotherapy, the addition of blocking PD-1 antibodies to the combined protocol sustained immune cell activation and effector functions, resulting in prolonged tumor regression and complete tumor clearance in 20% of mice. Mice who cleared the initial tumor challenge exhibited reduced tumor growth uponon rechallenge, consistent with the formation of immune memory.

CONCLUSION

TThese results demonstrate that NKT cell immunotherapy combined with oncolytic VSV-IL-15 virotherapy and PD-1 blockade enhances tumor control and presents a promising treatment strategy for targeting pancreatic cancer.

TGIF1-Twist1 axis in pancreatic ductal adenocarcinoma

TG-interacting factor 1 (TGIF1) exerts inhibitory effects on transforming growth factor-beta (TGF-β) signaling by suppressing Smad signaling pathway at multiple levels. TGIF1 activity is important for normal embryogenesis and organogenesis, yet its dysregulation can culminate in tumorigenesis. For instance, increased expression of TGIF1 correlates with poor prognosis in triple-negative breast cancer patients, and enforced expression of TGIF1 facilitates Wnt-driven mammary tumorigenesis, suggesting that TGIF1 might function as an oncoprotein. Quite surprisingly, TGIF1 has recently been shown to function as a tumor suppressor in pancreatic ductal adenocarcinoma (PDAC), possibly owing to its ability to antagonize the pro-malignant transcription factor Twist1. In this article, we will briefly elaborate on the biological and clinical significance of the unique tumor-suppressive function of TGIF1 and its functional interaction with Twist1 in the context of PDAC pathogenesis and progression.

An Integrated Meta-Analysis of Secretome and Proteome Identify Potential Biomarkers of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is extremely aggressive, has an unfavorable prognosis, and there are no biomarkers for early detection of the disease or identification of individuals at high risk for morbidity or mortality. The cellular and molecular complexity of PDAC leads to inconsistences in clinical validations of many proteins that have been evaluated as prognostic biomarkers of the disease. The tumor secretome, a potential source of biomarkers in PDAC, plays a crucial role in cell proliferation and metastasis, as well as in resistance to treatments, which together contribute to a worse clinical outcome. The massive amount of proteomic data from pancreatic cancer that has been generated from previous studies can be integrated and explored to uncover secreted proteins relevant to the diagnosis and prognosis of the disease. The present study aimed to perform an integrated meta-analysis of PDAC proteome and secretome public data to identify potential biomarkers of the disease. Our meta-analysis combined mass spectrometry data obtained from two systematic reviews of the pancreatic cancer literature, which independently selected 20 studies of the secretome and 35 of the proteome. Next, we predicted the secreted proteins using seven in silico tools or databases, which identified 39 secreted proteins shared between the secretome and proteome data. Notably, the expression of 31 genes of these secretome-related proteins was upregulated in PDAC samples from The Cancer Genome Atlas (TCGA) when compared to control samples from TCGA and The Genotype-Tissue Expression (GTEx). The prognostic value of these 39 secreted proteins in predicting survival outcome was confirmed using gene expression data from four PDAC datasets (validation set). The gene expression of these secreted proteins was able to distinguish high- and low-survival patients in nine additional tumor types from TCGA, demonstrating that deregulation of these secreted proteins may also contribute to the prognosis in multiple cancers types. Finally, we compared the prognostic value of the identified secreted proteins in PDAC biomarkers studies from the literature. This analysis revealed that our gene signature performed equally well or better than the signatures from these previous studies. In conclusion, our integrated meta-analysis of PDAC proteome and secretome identified 39 secreted proteins as potential biomarkers, and the tumor gene expression profile of these proteins in patients with PDAC is associated with worse overall survival.

TGIF1 functions as a tumor suppressor in pancreatic ductal adenocarcinoma

A prominent function of TGIF1 is suppression of transforming growth factor beta (TGF-β) signaling, whose inactivation is deemed instrumental to the progression of pancreatic ductal adenocarcinoma (PDAC), as exemplified by the frequent loss of the tumor suppressor gene SMAD4 in this malignancy. Surprisingly, we found that genetic inactivation of Tgif1 in the context of oncogenic Kras, KrasG12D , culminated in the development of highly aggressive and metastatic PDAC despite de-repressing TGF-β signaling. Mechanistic experiments show that TGIF1 associates with Twist1 and inhibits Twist1 expression and activity, and this function is suppressed in the vast majority of human PDACs by KrasG12D /MAPK-mediated TGIF1 phosphorylation. Ablating Twist1 in KrasG12D ;Tgif1KO mice completely blunted PDAC formation, providing the proof-of-principle that TGIF1 restrains KrasG12D -driven PDAC through its ability to antagonize Twist1. Collectively, these findings pinpoint TGIF1 as a potential tumor suppressor in PDAC and further suggest that sustained activation of TGF-β signaling might act to accelerate PDAC progression rather than to suppress its initiation.

Genome-Wide Profiling Reveals the Landscape of Prognostic Alternative Splicing Signatures in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive lethal malignancy. Identification of potential alternative splicing (AS) prognostic indicators and related splicing pathways for the prediction of PDAC outcomes is lacking but urgently needed. A combined strategy of prognostic assessment and computational biology was performed to investigate survival-related AS signatures and their correlation with splicing factors. The prognostic signatures of each type were conducted according to the top 10 prognosis-related AS events, which were filtered through univariate Cox regression analysis. A time-dependent receiver operating characteristic curve was constructed to access the predictive accuracy of prognostic signatures. The independent predictors were identified using multivariate Cox regression analysis. Potential regulation mechanisms between splicing factors and splicing events were investigated through regulatory networks and correlation analyses. A total of 915 overall survival (OS) and 480 recurrence-free survival (RFS)-related AS events were identified in 120 patients with PDAC. The independent prognostic signatures for each type displayed favorable accuracy for the prediction of OS and short-term RFS [area under the curves were >0.6] except for the Exclusive Exons type. The splicing regulatory networks showed potential interactions between splicing factors and AS parent genes. Moreover, a positive relationship was detected among each splicing factor and Percent Spliced In values of prognostic signatures. Our results provide a view of the landscape of prognosis-related AS events and reveal the potential correlation between splicing factors and prognostic signatures, which may represent novel outcome-predictor markers and opportunities for targeted therapy for PDAC.

Key genes associated with pancreatic cancer and their association with outcomes: A bioinformatics analysis

Pancreatic cancer is a highly malignant neoplastic disease of the digestive system. In the present study, the dataset GSE62165 was downloaded from the Gene Expression Omnibus (GEO) database. GSE62165 contained the data of 118 pancreatic ductal adenocarcinoma samples (38 early‑stage tumors, 62 lymph node metastases and 18 advanced tumors) and 13 control samples. Differences in the expression levels of genes between normal tissues and early‑stage tumors were investigated. A total of 240 differentially expressed genes (DEGs) were identified using R software 3.5 (137 upregulated genes and 103 downregulated genes). Then, the differentially expressed genes were subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. The following 18 core genes were identified using Cytoscape, based on the protein‑interaction network of DEGs determined using the online tool STRING: EGF, ALB, COL17A1, FN1, TIMP1, PLAU, PLA2G1B, IGFBP3, PLAUR, VCAN, COL1A1, PNLIP, CTRL, PRSS3, COMP, CPB1, ITGA2 and CEL. The pathways of the core genes were primarily associated with pancreatic secretion, protein digestion and absorption, and focal adhesion. Finally, survival analyses of core genes in pancreatic cancer were conducted using the UALCAN online database. It was revealed that PLAU and COL17A1 were significantly associated with poor prognosis (P<0.05). The expression levels of genes in primary pancreatic cancer tissues were then compared; only one gene, COL17A1, was identified to be significantly differentially expressed. Finally, another dataset from GEO, GSE28735, was analyzed to verify the upregulated expression of COL17A1. Taken together, the results of the present study have indicated that the expression of COL17A1 gene may be associated with the occurrence and development of pancreatic cancer.

Stromal protein βig-h3 reprogrammes tumour microenvironment in pancreatic cancer

OBJECTIVE

Pancreatic cancer is associated with an abundant stromal reaction leading to immune escape and tumour growth. This massive stroma drives the immune escape in the tumour. We aimed to study the impact of βig-h3 stromal protein in the modulation of the antitumoural immune response in pancreatic cancer.

DESIGN

We performed studies with p48-Cre;KrasG12D, pdx1-Cre;KrasG12D;Ink4a/Arffl/fl, pdx1-Cre;KrasG12D; p53R172H mice and tumour tissues from patients with pancreatic ductal adenocarcinoma (PDA). Some transgenic mice were given injections of anti-βig-h3, anti-CD8, anti-PD1 depleting antibodies. Tumour growth as well as modifications in the activation of local immune cells were analysed by flow cytometry, immunohistochemistry and immunofluorescence. Tissue stiffness was measured by atomic force microscopy.

RESULTS

We identified βig-h3 stromal-derived protein as a key actor of the immune paracrine interaction mechanism that drives pancreatic cancer. We found that βig-h3 is highly produced by cancer-associated fibroblasts in the stroma of human and mouse. This protein acts directly on tumour-specific CD8+ T cells and F4/80 macrophages. Depleting βig-h3 in vivo reduced tumour growth by enhancing the number of activated CD8+ T cell within the tumour and subsequent apoptotic tumour cells. Furthermore, we found that targeting βig-h3 in established lesions released the tissue tension and functionally reprogrammed F4/80 macrophages in the tumour microenvironment.

CONCLUSIONS

Our data indicate that targeting stromal extracellular matrix protein βig-h3 improves the antitumoural response and consequently reduces tumour weight. Our findings present βig-h3 as a novel immunological target in pancreatic cancer.

The NQO1 bioactivatable drug, β-lapachone, alters the redox state of NQO1+ pancreatic cancer cells, causing perturbation in central carbon metabolism

Many cancer treatments, such as those for managing recalcitrant tumors like pancreatic ductal adenocarcinoma, cause off-target toxicities in normal, healthy tissue, highlighting the need for more tumor-selective chemotherapies. β-Lapachone is bioactivated by NAD(P)H:quinone oxidoreductase 1 (NQO1). This enzyme exhibits elevated expression in most solid cancers and therefore is a potential cancer-specific target. β-Lapachone's therapeutic efficacy partially stems from the drug's induction of a futile NQO1-mediated redox cycle that causes high levels of superoxide and then peroxide formation, which damages DNA and causes hyperactivation of poly(ADP-ribose) polymerase, resulting in extensive NAD⁺/ATP depletion. However, the effects of this drug on energy metabolism due to NAD⁺ depletion were never described. The futile redox cycle rapidly consumes O₂, rendering standard assays of Krebs cycle turnover unusable. In this study, a multimodal analysis, including metabolic imaging using hyperpolarized pyruvate, points to reduced oxidative flux due to NAD⁺ depletion after β-lapachone treatment of NQO1+ human pancreatic cancer cells. NAD⁺-sensitive pathways, such as glycolysis, flux through lactate dehydrogenase, and the citric acid cycle (as inferred by flux through pyruvate dehydrogenase), were down-regulated by β-lapachone treatment. Changes in flux through these pathways should generate biomarkers useful for in vivo dose responses of β-lapachone treatment in humans, avoiding toxic side effects. Targeting the enzymes in these pathways for therapeutic treatment may have the potential to synergize with β-lapachone treatment, creating unique NQO1-selective combinatorial therapies for specific cancers. These findings warrant future studies of intermediary metabolism in patients treated with β-lapachone.

MicroRNA-7 functions as a tumor-suppressor gene by regulating ILF2 in pancreatic carcinoma

Interleukin enhancer binding factor 2 (ILF2) has been found to be markedly upregulated in pancreatic carcinoma and is involved in the pathogenesis of pancreatic carcinoma. Thus, ILF2 may be a potential target for therapy. Yet, the regulatory mechanisms of ILF2 in pancreatic carcinoma remain largely elusive. In the present study, we demonstrated that ILF2 functioned as an oncogene and regulated epithelial-mesenchymal transition (EMT)-associated genes in pancreatic carcinoma PANC-1 cells. MicroRNA-7 (miR-7) suppressed ILF2 mRNA expression and the protein level in PANC-1 cells. Contrary to ILF2, miRNA-7 functioned as a tumor-suppressor gene and negatively regulated EMT-associated genes in the PANC-1 cells. Curcumin, a polyphenol natural product isolated from the rhizome of the plant Curcuma longa, has emerged as a promising anticancer therapeutic agent. We found that treatment with curcumin increased miR-7 expression and suppressed ILF2 protein in the PANC-1 cells. Thus, we identified ILF2 as a new downstream target gene of curcumin. The results revealed that ILF2 is regulated by miR-7 and suggest that downregulation of miR-7 may be an important factor for the ILF2 overexpression in pancreatic carcinoma.

Molecular targets for the treatment of pancreatic cancer: Clinical and experimental studies

Pancreatic cancer is the fourth most common cause of cancer deaths worldwide. Although recent therapeutic developments for patients with pancreatic cancer have provided survival benefits, the outcomes for patients with pancreatic cancer remain unsatisfactory. Molecularly targeted cancer therapy has advanced in the past decade with the use of a number of pathways as candidates of therapeutic targets. This review summarizes the molecular features of this refractory disease while focusing on the recent clinical and experimental findings on pancreatic cancer. It also discusses the data supporting current standard clinical outcomes, and offers conclusions that may improve the management of pancreatic cancer in the future.

Quantitative Proteomic Analysis of Differentially Expressed Protein Profiles Involved in Pancreatic Ductal Adenocarcinoma

OBJECTIVES

The aim of this study was to identify differentially expressed proteins among various stages of pancreatic ductal adenocarcinoma (PDAC) by shotgun proteomics using nano-liquid chromatography coupled tandem mass spectrometry and stable isotope dimethyl labeling.

METHODS

Differentially expressed proteins were identified and compared based on the mass spectral differences of their isotope-labeled peptide fragments generated from protease digestion.

RESULTS

Our quantitative proteomic analysis of the differentially expressed proteins with stable isotope (deuterium/hydrogen ratio, ≥ 2) identified a total of 353 proteins, with at least 5 protein biomarker proteins that were significantly differentially expressed between cancer and normal mice by at least a 2-fold alteration. These 5 protein biomarker candidates include α-enolase, α-catenin, 14-3-3 β, VDAC1, and calmodulin with high confidence levels. The expression levels were also found to be in agreement with those examined by Western blot and histochemical staining.

CONCLUSIONS

The systematic decrease or increase of these identified marker proteins may potentially reflect the morphological aberrations and diseased stages of pancreas carcinoma throughout progressive developments leading to PDAC. The results would form a firm foundation for future work concerning validation and clinical translation of some identified biomarkers into targeted diagnosis and therapy for various stages of PDAC.

Eukaryotic Translation Initiation Factor 5A (EIF5A) Regulates Pancreatic Cancer Metastasis by Modulating RhoA and Rho-associated Kinase (ROCK) Protein Expression Levels

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers with an overall survival rate of less than 5%. The poor patient outcome in PDAC is largely due to the high prevalence of systemic metastasis at the time of diagnosis and lack of effective therapeutics that target disseminated cells. The fact that the underlying mechanisms driving PDAC cell migration and dissemination are poorly understood have hindered drug development and compounded the lack of clinical success in this disease. Recent evidence indicates that mutational activation of K-Ras up-regulates eIF5A, a component of the cellular translational machinery that is critical for PDAC progression. However, the role of eIF5A in PDAC cell migration and metastasis has not been investigated. We report here that pharmacological inhibition or genetic knockdown of eIF5A reduces PDAC cell migration, invasion, and metastasis in vitro and in vivo. Proteomic profiling and bioinformatic analyses revealed that eIF5A controls an integrated network of cytoskeleton-regulatory proteins involved in cell migration. Functional interrogation of this network uncovered a critical RhoA/ROCK signaling node that operates downstream of eIF5A in invasive PDAC cells. Importantly, eIF5A mediates PDAC cell migration and invasion by modulating RhoA/ROCK protein expression levels. Together our findings implicate eIF5A as a cytoskeletal rheostat controlling RhoA/ROCK protein expression during PDAC cell migration and metastasis. Our findings also implicate the eIF5A/RhoA/ROCK module as a potential new therapeutic target to treat metastatic PDAC cells.

NF45 overexpression is associated with poor prognosis and enhanced cell proliferation of pancreatic ductal adenocarcinoma

NF45, also referred to as nuclear factor of activated T cells, has been reported to promote the progression of multiple cancer types. However, the expression and physiological significance of NF45 in pancreatic ductal adenocarcinoma (PDAC) remain largely elusive. In this study, we investigated the clinical relevance and potential role of NF45 expression in PDAC development. Western blot analysis revealed that NF45 was remarkably upregulated in PDAC tissues, compared with the adjacent non-tumorous ones. In addition, the expression of NF45 in 122 patients with PDAC was evaluated using immunohistochemistry. In this way, we found that NF45 was abundantly expressed in PDAC tissues, and the expression of NF45 was correlated with tumor size (p = 0.007), histological differentiation (p = 0.033), and TNM stage (p = 0.001). Importantly, patients with low levels of NF45 expression exhibited better postoperative prognosis as compared with those with high NF45 expression. Furthermore, using PDAC cell cultures, we found that interference of NF45 expression using siRNA oligos suppressed PDAC cell proliferation and retarded cell cycle progression. Moreover, depletion of NF45 impaired the levels of cellular cyclin E and proliferating cell nuclear antigen (PCNA). Conversely, overexpression of NF45 facilitated the cell growth and accelerated cell cycle progression. Our results establish NF45 as an important indicator of PDAC prognosis with potential utility as a therapeutic target in this lethal disease.

Irreversible electroporation of the pancreas is feasible and safe in a porcine survival model

OBJECTIVES

Use of thermal tumor ablation in the pancreatic parenchyma is limited because of the risk of pancreatitis, pancreatic fistula, or hemorrhage. This study aimed to evaluate the feasibility and safety of irreversible electroporation (IRE) in a porcine model.

METHODS

Ten pigs were divided into 2 study groups. In the first group, animals received IRE of the pancreatic tail and were killed after 60 minutes. In the second group, animals received IRE at the head of the pancreas and were followed up for 7 days. Clinical parameters, computed tomography imaging, laboratory results, and histology were obtained.

RESULTS

All animals survived IRE ablation, and no cardiac adverse effects were noted. Sixty minutes after IRE, a hypodense lesion on computed tomography imaging indicated the ablation zone. None of the animals developed clinical signs of acute pancreatitis. Only small amounts of ascites fluid, with a transient increase in amylase and lipase levels, were observed, indicating that no pancreatic fistula occurred.

CONCLUSIONS

This porcine model shows that IRE is feasible and safe in the pancreatic parenchyma. Computed tomography imaging reveals significant changes at 60 minutes after IRE and therefore might serve as an early indicator of therapeutic success. Clinical studies are needed to evaluate the efficacy of IRE in pancreatic cancer.

A hypusine-eIF5A-PEAK1 switch regulates the pathogenesis of pancreatic cancer

Deregulation of protein synthesis is a hallmark of cancer cell proliferation, survival, and metastatic progression. eIF5A1 and its highly related isoform eIF5A2 are translation initiation factors that have been implicated in a range of human malignancies, but how they control cancer development and disease progression is still poorly understood. Here, we investigated how eIF5A proteins regulate pancreatic ductal adenocarcinoma (PDAC) pathogenesis. eIF5A proteins are the only known proteins regulated by a distinct posttranslational modification termed hypusination, which is catalyzed by two enzymes, deoxyhypusine synthase (DHPS) and deoxyhypusine hydroxylase (DOHH). The highly selective nature of the hypusine modification and its amenability to pharmacologic inhibition make eIF5A proteins attractive therapeutic targets. We found that the expression and hypusination of eIF5A proteins are upregulated in human PDAC tissues and in premalignant pancreatic intraepithelial neoplasia tissues isolated from Pdx-1-Cre: LSL-KRAS(G12D) mice. Knockdown of eIF5A proteins in PDAC cells inhibited their growth in vitro and orthotopic tumor growth in vivo, whereas amplification of eIF5A proteins increased PDAC cell growth and tumor formation in mice. Small-molecule inhibitors of DHPS and DOHH both suppressed eIF5A hypusination, preventing PDAC cell growth. Interestingly, we found that eIF5A proteins regulate PDAC cell growth by modulating the expression of PEAK1, a nonreceptor tyrosine kinase essential for PDAC cell growth and therapy resistance. Our findings suggest that eIF5A proteins utilize PEAK1 as a downstream effector to drive PDAC pathogenesis and that pharmacologic inhibition of the eIF5A-hypusine-PEAK1 axis may provide a novel therapeutic strategy to combat this deadly disease.

Mnk kinase pathway: Cellular functions and biological outcomes

The mitogen-activated protein kinase (MAPK) interacting protein kinases 1 and 2 (Mnk1 and Mnk2) play important roles in controlling signals involved in mRNA translation. In addition to the MAPKs (p38 or Erk), multiple studies suggest that the Mnk kinases can be regulated by other known kinases such as Pak2 and/or other unidentified kinases by phosphorylation of residues distinct from the sites phosphorylated by the MAPKs. Several studies have established multiple Mnk protein targets, including PSF, heterogenous nuclear ribonucleoprotein A1, Sprouty 2 and have lead to the identification of distinct biological functions and substrate specificity for the Mnk kinases. In this review we discuss the pathways regulating the Mnk kinases, their known substrates as well as the functional consequences of engagement of pathways controlled by Mnk kinases. These kinases play an important role in mRNA translation via their regulation of eukaryotic initiation factor 4E (eIF4E) and their functions have important implications in tumor biology as well as the regulation of drug resistance to anti-oncogenic therapies. Other studies have identified a role for the Mnk kinases in cap-independent mRNA translation, suggesting that the Mnk kinases can exert important functional effects independently of the phosphorylation of eIF4E. The role of Mnk kinases in inflammation and inflammation-induced malignancies is also discussed.

Challenges and future directions in therapeutics for pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the USA. The 5-year survival of < 5% has not changed in decades. In contrast to other major cancers, the incidence of PDAC is increasing.

AREAS COVERED

The aims of this paper are first to analyze why PDAC is so difficult to treat and, second, to suggest future directions for PDAC therapeutics. The authors provide an article that is based on a comprehensive search through MEDLINE and the clinicalTrials.gov website.

EXPERT OPINION

Progress has been made recently. Notably, FOLFIRINOX or nab-paclitaxel plus gemcitabine provide survival benefit over gemcitabine alone, which was previously the mainstay of therapy for PDAC. Most of the current trials are testing combinations of repurposed drugs rather than addressing key targets in the PDAC pathogenesis. It is clear that to really make an impact on this disease, it will be necessary to address three different problems with targeted therapeutics. First, it is important to eradicate PDAC stem cells that result in recurrence. Second, it is important to reduce the peritumoral stroma that provides the tumors with growth support and provides a barrier to access of therapeutic agents. Finally, it is important to address the marked cachexia and metabolic derangement that contribute to morbidity and mortality and further complicate therapeutic intervention.

Epidemiological-molecular evidence of metabolic reprogramming on proliferation, autophagy and cell signaling in pancreas cancer

Pancreatic cancer remains one of the deadliest human cancers with little progress made in survival over the past decades, and 5-year survival usually below 5%. Despite this dismal scenario, progresses have been made in understanding of the underlying tumor biology through among other definition of precursor lesions, delineation of molecular pathways, and advances in genome-wide technology. Further, exploring the relationship between epidemiological risk factors involving metabolic features to that of an altered cancer metabolism may provide the foundation for new therapies. Here we explore how nutrients and caloric intake may influence the KRAS-driven ductal carcinogenesis through mediators of metabolic stress, including autophagy in presence of TP53, advanced glycation end products (AGE) and the receptors (RAGE) and ligands (HMGB1), as well as glutamine pathways, among others. Effective understanding the cancer metabolism mechanisms in pancreatic cancer may propose new ways of prevention and treatment.

Efficient targeting and tumor retardation effect of pancreatic adenocarcinoma up-regulated factor (PAUF)-specific RNA replacement in pancreatic cancer mouse model

The soluble protein pancreatic adenocarcinoma up-regulated factor (PAUF) plays an important role in pancreatic tumor progression and has begun to attract attention as a therapeutic target for pancreatic cancer. We herein present PAUF RNA-targeting gene therapy strategies with both targeting and therapeutic function using trans-splicing ribozyme (TSR) in pancreatic cancer. We developed adenoviral PAUF-targeting TSR (Rz) containing a PAUF-specific internal guide sequence (IGS) determined by library screening. This Rz harbors suicide gene, herpes simplex virus thymidine kinase (HSV-tk) or firefly luciferase (Luc) as a transgene for 3' exon replacement of PAUF RNAs. Ad-Rz-TK, Rz harboring the HSV-tk, showed significant inhibition of tumor growth in vivo as well as PAUF-dependent cell death in vitro via a successful trans-splicing reaction. Selective induction of Rz-controlled transgene in PAUF-expressing pancreatic cancer was confirmed through noninvasive in vivo imaging; a luminescence signal from Rz harboring Luc (Ad-Rz-Luc) was detectable only in pancreatic tumor sites, not in normal mice. In addition, a [(125)I] FIAU signal reflecting thymidine kinase expression through SPECT and ex vivo biodistribution was co-localized with the tumor sites when we treated with Ad-Rz-TK in orthotopic xenograft model. Taken together, these results imply that PAUF-targeting TSR can contribute to successful targeted gene therapy for pancreatic cancer.

uPAR-controlled oncolytic adenoviruses eliminate cancer stem cells in human pancreatic tumors

Pancreatic tumors contain cancer stem cells highly resistant to chemotherapy. The identification of therapies that can eliminate this population of cells might provide with more effective treatments. In the current work we evaluated the potential of oncolytic adenoviruses to act against pancreatic cancer stem cells (PCSC). PCSC from two patient-derived xenograft models were isolated from orthotopic pancreatic tumors treated with saline, or with the chemotherapeutic agent gemcitabine. An enrichment in the number of PCSC expressing the cell surface marker CD133 and a marked enhancement on tumorsphere formation was observed in gemcitabine treated tumors. No significant increase in the CD44, CD24, and epithelial-specific antigen (ESA) positive cells was observed. Neoplastic sphere-forming cells were susceptible to adenoviral infection and exposure to oncolytic adenoviruses resulted in elevated cytotoxicity with both Adwt and the tumor specific AduPARE1A adenovirus. In vivo, intravenous administration of a single dose of AduPARE1A in human-derived pancreatic xenografts led to a remarkable anti-tumor effect. In contrast to gemcitabine AduPARE1A treatment did not result in PCSC enrichment. No enrichment on tumorspheres neither on the CD133(+) population was detected. Therefore our data provide evidences of the relevance of uPAR-controlled oncolytic adenoviruses for the elimination of pancreatic cancer stem cells.

Intraductal delivery of adenoviruses targets pancreatic tumors in transgenic Ela-myc mice and orthotopic xenografts

Gene-based anticancer therapies delivered by adenoviruses are limited by the poor viral distribution into the tumor. In the current work we have explored the feasibility of targeting pancreatic tumors through a loco-regional route. We have taken advantage of the ductal network in the pancreas to retrogradelly inject adenoviruses through the common bile duct in two different mouse models of pancreatic carcinogenesis: The transgenic Ela-myc mice that develop mixed neoplasms displaying both acinar-like and duct-like neoplastic cells affecting the whole pancreas; and mice bearing PANC-1 and BxPC-3 orthotopic xenografts that constitute a model of localized human neoplastic tumors. We studied tumor targeting and the anticancer effects of newly thymidine kinase-engineered adenoviruses both in vitro and in vivo, and conducted comparative studies between intraductal or intravenous administration. Our data indicate that the intraductal delivery of adenovirus efficiently targets pancreatic tumors in the two mouse models. The in vivo application of AduPARTKT plus ganciclovir (GCV) treatment induced tumor regression in Ela-myc mice. Moreover, the intraductal injection of ICOVIR15-TKT oncolytic adenoviruses significantly improved mean survival of mice bearing PANC-1 and BxPC-3 pancreatic xenografts from 30 to 52 days and from 20 to 68 days respectively (p less than 0.0001) when combined with GCV. Of notice, both AduPARTKT and ICOVIR15-TKT antitumoral responses were stronger by ductal viral application than intravenously, in line with the 38-fold increase in pancreas transduction observed upon ductal administration. In summary our data show that cytotoxic adenoviruses retrogradelly injected to the pancreas can be a feasible approach to treat localized pancreatic tumors.

Gemcitabine triggers a pro-survival response in pancreatic cancer cells through activation of the MNK2/eIF4E pathway

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive neoplastic disease. Gemcitabine, the currently used chemotherapeutic drug for PDAC, elicits only minor benefits, because of the development of escape pathways leading to chemoresistance. Herein, we aimed at investigating the involvement of the mitogen activating protein kinase interacting kinase (MNK)/eIF4E pathway in the acquired drug resistance of PDAC cells. Screening of a cohort of PDAC patients by immunohistochemistry showed that eIF4E phosphorylation correlated with disease grade, early onset of disease and worse prognosis. In PDAC cell lines, chemotherapeutic drugs induced MNK-dependent phosphorylation of eIF4E. Importantly, pharmacological inhibition of MNK activity synergistically enhanced the cytostatic effect of gemcitabine, by promoting apoptosis. RNA interference (RNAi) experiments indicated that MNK2 is mainly responsible for eIF4E phosphorylation and gemcitabine resistance in PDAC cells. Furthermore, we found that gemcitabine induced the expression of the oncogenic splicing factor SRSF1 and splicing of MNK2b, a splice variant that overrides upstream regulatory pathways and confers increased resistance to the drug. Silencing of SRSF1 by RNAi abolished this splicing event and recapitulated the effects of MNK pharmacological or genetic inhibition on eIF4E phosphorylation and apoptosis in gemcitabine-treated cells. Our results highlight a novel pro-survival pathway triggered by gemcitabine in PDAC cells, which leads to MNK2-dependent phosphorylation of eIF4E, suggesting that the MNK/eIF4E pathway represents an escape route utilized by PDAC cells to withstand chemotherapeutic treatments.

Depletion of RAD17 sensitizes pancreatic cancer cells to gemcitabine

Chemotherapy of advanced pancreatic cancer has mainly been gemcitabine-based for the past 15 years, with only limited effect. Recently, combination therapy that also targets checkpoint kinase 1 (CHK1) has become an attractive option. The central role of CHK1 in many DNA-damage response pathways, however, may result in undesired cytotoxicity in normal cells, causing side effects. We were searching for other target molecules of similar function that may be more specific and thus better suited for combination therapy. To this end a negative selection RNAi screen was performed in cell lines with small hairpin RNA molecules targeting over 10,000 genes. Genes that were found to be synthetically lethal with gemcitabine and whose proteins act upstream of CHK1 were characterised in more detail. In particular, the inhibition of RAD17 potentiated gemcitabine cytotoxicity in the pancreatic cancer cell lines BxPC-3 and MiaPaca-2 and in the primary cell line JoPaca-1 that closely resembles primary tumour tissue. Further analysis showed that the synergistic effect of RAD17 knockdown and gemcitabine leads to forced mitotic entry of cells arrested in S phase by gemcitabine treatment, resulting in asymmetric DNA distribution during anaphase followed by DNA fragmentation and finally cell death by mitotic catastrophe. Our data suggest RAD17 as a novel target protein for gemcitabine combination therapy supplementing or complementing inhibition of CHK1. In contrast to CHK1, RAD17 knockdown by itself does not lead to abnormal DNA segregation, suggesting a more specific action.

Establishment and characterization of a highly tumourigenic and cancer stem cell enriched pancreatic cancer cell line as a well defined model system

Standard cancer cell lines do not model the intratumoural heterogeneity situation sufficiently. Clonal selection leads to a homogeneous population of cells by genetic drift. Heterogeneity of tumour cells, however, is particularly critical for therapeutically relevant studies, since it is a prerequisite for acquiring drug resistance and reoccurrence of tumours. Here, we report the isolation of a highly tumourigenic primary pancreatic cancer cell line, called JoPaca-1 and its detailed characterization at multiple levels. Implantation of as few as 100 JoPaca-1 cells into immunodeficient mice gave rise to tumours that were histologically very similar to the primary tumour. The high heterogeneity of JoPaca-1 was reflected by diverse cell morphology and a substantial number of chromosomal aberrations. Comparative whole-genome sequencing of JoPaca-1 and BxPC-3 revealed mutations in genes frequently altered in pancreatic cancer. Exceptionally high expression of cancer stem cell markers and a high clonogenic potential in vitro and in vivo was observed. All of these attributes make this cell line an extremely valuable model to study the biology of and pharmaceutical effects on pancreatic cancer.

The matricellular protein CCN1/Cyr61 is a critical regulator of Sonic Hedgehog in pancreatic carcinogenesis

CCN1 is a matricellular protein and a member of the CCN family of growth factors. CCN1 is associated with the development of various cancers including pancreatic ductal adenocarcinoma (PDAC). Our recent studies found that CCN1 plays a critical role in pancreatic carcinogenesis through the induction of EMT and stemness. CCN1 mRNA and protein were detected in the early precursor lesions, and their expression intensified with disease progression. However, biochemical activity and the molecular targets of CCN1 in pancreatic cancer cells are unknown. Here we show that CCN1 regulates the Sonic Hedgehog (SHh) signaling pathway, which is associated with the PDAC progression and poor prognosis. SHh regulation by CCN1 in pancreatic cancer cells is mediated through the active Notch-1. Notably, active Notch-1is recruited by CCN1 in these cells via the inhibition of proteasomal degradation results in stabilization of the receptor. We find that CCN1-induced activation of SHh signaling might be necessary for CCN1-dependent in vitro pancreatic cancer cell migration and tumorigenicity of the side population of pancreatic cancer cells (cancer stem cells) in a xenograft in nude mice. Moreover, the functional role of CCN1 could be mediated through the interaction with the αvβ3 integrin receptor. These extensive studies propose that targeting CCN1 can provide a new treatment option for patients with pancreatic cancer since blocking CCN1 simultaneously blocks two critical pathways (i.e. SHh and Notch1) associated with the development of the disease as well as drug resistance.

KRas induces a Src/PEAK1/ErbB2 kinase amplification loop that drives metastatic growth and therapy resistance in pancreatic cancer

Early biomarkers and effective therapeutic strategies are desperately needed to treat pancreatic ductal adenocarcinoma (PDAC), which has a dismal 5-year patient survival rate. Here, we report that the novel tyrosine kinase PEAK1 is upregulated in human malignancies, including human PDACs and pancreatic intraepithelial neoplasia (PanIN). Oncogenic KRas induced a PEAK1-dependent kinase amplification loop between Src, PEAK1, and ErbB2 to drive PDAC tumor growth and metastasis in vivo. Surprisingly, blockade of ErbB2 expression increased Src-dependent PEAK1 expression, PEAK1-dependent Src activation, and tumor growth in vivo, suggesting a mechanism for the observed resistance of patients with PDACs to therapeutic intervention. Importantly, PEAK1 inactivation sensitized PDAC cells to trastuzumab and gemcitabine therapy. Our findings, therefore, suggest that PEAK1 is a novel biomarker, critical signaling hub, and new therapeutic target in PDACs.

Oncogenic Kras-induced GM-CSF production promotes the development of pancreatic neoplasia

Stromal responses elicited by early stage neoplastic lesions can promote tumor growth. However, the molecular mechanisms that underlie the early recruitment of stromal cells to sites of neoplasia remain poorly understood. Here, we demonstrate an oncogenic Kras(G12D)-dependent upregulation of GM-CSF in mouse pancreatic ductal epithelial cells (PDECs). An enhanced GM-CSF production is also observed in human PanIN lesions. Kras(G12D)-dependent production of GM-CSF in vivo is required for the recruitment of Gr1(+)CD11b(+) myeloid cells. The suppression of GM-CSF production inhibits the in vivo growth of Kras(G12D)-PDECs, and, consistent with the role of GM-CSF in Gr1(+)CD11b(+) mobilization, this effect is mediated by CD8(+) T cells. These results identify a pathway that links oncogenic activation to the evasion of antitumor immunity.

Targeting heat shock response pathways to treat pancreatic cancer

Pancreatic cancer belongs to the group of extremely aggressive human cancers; conventional cancer treatments have little impact. Increasing understanding of the pathways associated with pancreatic cancer progression has enabled the development of targeted therapy on this cancer. Heat shock proteins (HSPs) and related heat shock response (HSR) pathways control multiple important oncogenic pathways for pancreatic cancer development. Consequently, they represent promising novel targets for pancreatic cancer therapy. Various strategies have been proposed and elaborated to target HSPs/HSR in pancreatic cancer with the corresponding modulators, the details of which are highlighted in this review.

Impact of curcumin, raspberry extract, and neem leaf extract on rel protein-regulated cell death/radiosensitization in pancreatic cancer cells

OBJECTIVES

Nuclear factor κB (NF-κB) plays an intrinsic role in promoting growth, angiogenesis, and metastasis in pancreatic cancer (PC) and serves as a mechanism underlying therapeutic resistance. Accordingly, we investigated the efficacy of bioactive phytochemicals in inhibiting radiotherapy (RT)-induced NF-κB activity, signaling, and NF-κB-dependent regulation of cell death.

METHODS

Panc-1, BxPC-3, and MIA PaCa-2 cells exposed to 10 Gy (single high dose [SDR]) or 2 Gy/d for 5 days (fractionated radiation [FIR]) with or without curcumin (CUR), neem leaf extract (NLE), or black raspberry extract (RSE) were analyzed.

RESULTS

Radiotherapy profoundly induced NF-κB-DNA-binding activity with relatively robust activation after FIR. Curcumin, NLE, and RSE significantly inhibited both constitutive and RT-induced NF-κB. Furthermore, quantitative polymerase chain reaction profiling of 88 NF-κB pathway molecules demonstrated that CUR, NLE, and RSE comprehensively, yet differentially inhibited FIR/SDR-induced genes. Functionally, CUR, NLE, and RSE markedly conferred RT-inhibited cell viability/survival, robustly activated caspase-3/7 activity, and subsequent cell death. More importantly, NF-κB overexpression and silencing studies demonstrate that these compounds potentiate RT-induced cell death by targeting RT-induced NF-κB.

CONCLUSIONS

These data strongly imply that CUR, NLE, and RSE may serve as effective "deliverables" to potentiate RT in PC cure and further throw light that these phytochemicals-induced cell killing may involve selective regulation of RT-induced NF-κB.

Advances in pancreatic cancer

PURPOSE OF REVIEW

This review intends to describe recent studies on the interaction between pancreatic cancer cells and tumor stroma, and potential opportunities and limitations to therapeutically targeting the stroma.

RECENT FINDINGS

Pancreatic cancer is characterized by densely desmoplastic stroma. It is becoming increasingly clear that there are complex and mutually supportive interactions between cancer cells and the stroma. Specific signaling pathways exist between cancer cells and cancer-associated fibroblasts that contribute to hypoxic desmoplasia. Recent developments in therapeutic approaches to targeting the stroma have demonstrated potential for enhancing efficacy of cytotoxic therapies. However, the heterogeneity and genomic complexity between tumors has also become more evident based on recent findings. There is increasing evidence for hierarchy of cancer cells with identification of a subpopulation of cancer stem cells that are inherently resistant to traditional therapies.

SUMMARY

Targeting pancreatic cancer stroma is a novel therapeutic strategy that appears justified based on recent studies; however, continued focus is needed to develop more effective therapies against cells resistant to standard chemotherapy.

Genome profiling of pancreatic adenocarcinoma

Pancreatic adenocarcinoma is one of the most aggressive human cancers. It displays many different chromosomal abnormalities and mutations. By using 244 K high-resolution array-comparative genomic hybridization (aCGH) we studied the genome alterations of 39 fine-needle aspirations from pancreatic adenocarcinoma and eight human adenocarcinoma pancreatic cell lines. Using both visual inspection and GISTIC analysis, recurrent losses were observed on 1p, 3p, 4p, 6, 8p, 9, 10, 11q, 15q, 17, 18, 19p, 20p, 21, and 22 and comprised several known or suspected tumor suppressor genes such as ARHGEF10, ARID1A, CDKN2A/B, FHIT, PTEN, RB1, RUNX1-3, SMAD4, STK11/LKB1, TP53, and TUSC3. Heterozygous deletion of the 1p35-p36 chromosomal region was identified in one-third of the tumors and three of the cell lines. This region, commonly deleted in human cancers, contains several tumor suppressor genes including ARID1A and RUNX3. We identified frequent genetic gains on chromosome arms 1q, 3q, 5p, 6p, 7q, 8q, 12q, 15q, 18q, 19q, and 20q. Amplifications were observed in 16 tumors. AKT2, CCND3, CDK4, FOXA2, GATA6, MDM2, MYC, and SMURF1 genes were gained or amplified. The most obvious amplification was located at 18q11.2 and targeted the GATA6 gene, which plays a predominant role in the initial specification of the pancreas and in pancreatic cell type differentiation. In conclusion, we have identified novel biomarkers and potential therapeutic targets in pancreatic adenocarcinoma.

Cancer biology and genomics: translating discoveries, transforming pathology

Advances in our understanding of cancer biology and discoveries emerging from cancer genomics are being translated into real clinical benefits for patients with cancer. The 2011 Journal of Pathology Annual Review Issue provides a snapshot of recent rapid progress on multiple fronts in the war on cancer or, more precisely, the wars on cancers. Indeed, perhaps the most notable recent shift is reflected by the sharp increase in understanding the biology of multiple specific cancers and using these new insights to inform rationally targeted therapies, with often striking successes. These recent developments, as reviewed in this issue, show how the long-term investments in basic cancer research are finally beginning to bear fruit.

Molecular targeted approaches for treatment of pancreatic cancer

Human pancreatic cancer remains a highly malignant disease with almost similar incidence and mortality despite extensive research. Many targeted therapies are under development. However, clinical investigation showed that single targeted therapies and most combined therapies were not able to improve the prognosis of this disease, even though some of these therapies had excellent anti-tumor effects in pre-clinical models. Cross-talk between cell proliferation signaling pathways may be an important phenomenon in pancreatic cancer, which may result in cancer cell survival even though some pathways are blocked by targeted therapy. Pancreatic cancer may possess different characteristics and targets in different stages of pathogenesis, maintenance and metastasis. Sensitivity to therapy may also vary for cancer cells at different stages. The unique pancreatic cancer structure with abundant stroma creates a tumor microenvironment with hypoxia and low blood perfusion rate, which prevents drug delivery to cancer cells. In this review, the most commonly investigated targeted therapies in pancreatic cancer treatment are discussed. However, how to combine these targeted therapies and/or combine them with chemotherapy to improve the survival rate of pancreatic cancer is still a challenge. Genomic and proteomic studies using pancreatic cancer samples obtained from either biopsy or surgery are recommended to individualize tumor characters and to perform drug sensitivity study in order to design a tailored therapy with minimal side effects. These studies may help to further investigate tumor pathogenesis, maintenance and metastasis to create cellular expression profiles at different stages. Integration of the information obtained needs to be performed from multiple levels and dimensions in order to develop a successful targeted therapy.