PTEN loss accelerates KrasG12D-induced pancreatic cancer development

Efficient Gene Delivery and Expression in Pancreas and Pancreatic Tumors by Capsid-Optimized AAV8 Vectors

Despite efforts to use adeno-associated viral (AAV) vector-mediated gene therapy for treatment of pancreatic ductal adenocarcinoma (PDAC), transduction efficiency remains a limiting factor and thus improvement of AAV delivery would significantly facilitate the treatment of this malignancy. Site-directed mutagenesis of specific tyrosine (Y) residues to phenylalanine (F) on the surface of various AAV serotype capsids has been reported as a method for enhancing gene transfer efficiencies. In the present studies, we determine whether Y-to-F mutations could also enhance AAV8 gene transfer in the pancreas to facilitate gene therapy for PDAC. Three different Y-to-F mutant vectors (a single-mutant, Y733F; a double-mutant, Y447F+Y733F; and a triple-mutant, Y275F+Y447F+Y733F) and wild-type AAV8 (WT-AAV8) were administered by intraperitoneal or tail-vein routes to Kras^G12D+/-, Kras^G12D+/-/Pten^+/-, and wild-type mice. The transduction efficiency of these vectors expressing the mCherry reporter gene was evaluated 2 weeks post administration in pancreas or PDAC and correlated with viral genome copy numbers. Our comparative and quantitative analyses of the transduction profiles demonstrated that the Y-to-F double-mutant exhibited the highest mCherry expression in pancreatic tissues (range 45-70%) compared with WT-AAV8 (7%; p < 0.01). We also detected a 7-fold higher level of vector genome copy numbers in normal pancreas following transduction with the double-mutant AAV8 compared with WT-AAV8 (10,285 vs. 1,500 vector copies/μg DNA respectively, p < 0.05). In addition, we observed that intraperitoneal injection of the double-mutant AAV8 led to a 15-fold enhanced transduction efficiency as compared to WT-AAV8 in mouse PDAC, with a corresponding ∼14-fold increase in vector genome copy numbers (26,575 vs. 2,165 copies/μg DNA respectively, p < 0.05). These findings indicate that the Y447+Y733F-AAV8 leads to a significant enhancement of transduction efficiency in both normal and malignant pancreatic tissues, suggesting the potential use of this vector in targeting pancreatic diseases in general, and PDAC in particular.

A combinatorial strategy using YAP and pan-RAF inhibitors for treating KRAS-mutant pancreatic cancer

KRAS mutation is the most common genetic event in pancreatic cancer. Whereas KRAS itself has proven difficult to inhibit, agents that target key downstream signals of KRAS, such as RAF, are possibly effective for pancreatic cancer treatment. Because selective BRAF inhibitors paradoxically induce downstream signaling activation, a pan-RAF inhibitor, LY3009120 is a better alternate for KRAS-mutant tumor treatment. Here we explored a new combinational strategy using a YAP inhibitor and LY3009120 in pancreatic cancer treatment. We found that reduced YAP expression closely correlates with longer relapse-free and overall survival of patients. Stable knockdown of YAP significantly inhibited pancreatic cancer cell proliferation and tumor growth. In addition, LY3009120 exhibited a dramatically enhanced antitumor effect in combination with YAP knockdown. YAP depletion blocks the activation of a parallel AKT signal pathway after LY3009120 treatment. Finally, combination with a YAP inhibitor, verteporfin, significantly enhanced the antitumor efficacy of LY3009120. Collectively, our results demonstrate that genetic or pharmacological inhibition of YAP can increase sensitivity to LY3009120 in pancreatic cancer through blocking compensatory activation of a parallel AKT signal pathway, thereby validating a combinatorial approach for treating KRAS-mutant pancreatic cancer.

Acinar cell plasticity and development of pancreatic ductal adenocarcinoma

Acinar cells in the adult pancreas show high plasticity and can undergo transdifferentiation to a progenitor-like cell type with ductal characteristics. This process, termed acinar-to-ductal metaplasia (ADM), is an important feature facilitating pancreas regeneration after injury. Data from animal models show that cells that undergo ADM in response to oncogenic signalling are precursors for pancreatic intraepithelial neoplasia lesions, which can further progress to pancreatic ductal adenocarcinoma (PDAC). As human pancreatic adenocarcinoma is often diagnosed at a stage of metastatic disease, understanding the processes that lead to its initiation is important for the discovery of markers for early detection, as well as options that enable an early intervention. Here, the critical determinants of acinar cell plasticity are discussed, in addition to the intracellular and extracellular signalling events that drive acinar cell metaplasia and their contribution to development of PDAC.

Epithelial-mesenchymal transition in cancer: Role of the IL-8/IL-8R axis

Epithelial-mesenchymal transition (EMT) is a biological process that is associated with cancer metastasis and invasion. In cancer, EMT promotes cell motility, invasion and distant metastasis. Interleukin (IL)-8 is highly expressed in tumors and may induce EMT. The IL-8/IL-8R axis has a vital role in EMT in carcinoma, which is regulated by several signaling pathways, including the transforming growth factor β-spleen associated tyrosine kinase/Src-AKT/extracellular signal-regulated kinase, p38/Jun N-terminal kinase-activating transcription factor-2, phosphoinositide 3-kinase/AKT, nuclear factor-κB and Wnt signaling pathways. Blocking the IL-8/IL-8R signaling pathway may be a novel strategy to reduce metastasis and improve patient survival rates. This review will cover IL-8-IL-8R signaling pathway in tumor epithelial-mesenchymal transition.

Molecular Drivers of Pancreatic Cancer Pathogenesis: Looking Inward to Move Forward

Pancreatic cancer (PC) continues to rank among the most lethal cancers. The consistent increase in incidence and mortality has made it the seventh leading cause of cancer-associated deaths globally and the third in the United States. The biggest challenge in combating PC is our insufficient understanding of the molecular mechanism(s) underlying its complex biology. Studies during the last several years have helped identify several putative factors and events, both genetic and epigenetic, as well as some deregulated signaling pathways, with implications in PC onset and progression. In this review article, we make an effort to summarize our current understanding of molecular and cellular events involved in the pathogenesis of pancreatic malignancy. Specifically, we provide up-to-date information on the genetic and epigenetic changes that occur during the initiation and progression of PC and their functional involvement in the pathogenic processes. We also discuss the impact of the tumor microenvironment on the molecular landscape of PC and its role in aggressive disease progression. It is envisioned that a better understanding of these molecular factors and the mechanisms of their actions can help unravel novel diagnostic and prognostic biomarkers and can also be exploited for future targeted therapies.

Integrated expression profiles analysis reveals novel predictive biomarker in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most lethal human malignant tumor, with a dismal 5-year survival rate of less than 5%. The lack of specific symptoms at early tumor stages and the paucity of biomarkers contribute to the poor diagnosis of pancreatic ductal adenocarcinoma. To improve prognosis, a screening biomarker for early diagnosis of pancreatic cancer is in urgent need. We searched the databases of expression profiling by array on GEO, aiming at comparing gene expression profile of matched pairs of pancreatic tumor and adjacent non-tumor tissues, and we screen out 4 suitable series of gene expression microarray data (“GSE15471”, “GSE18670”, “GSE28735” and “GSE58561”). After carefully analyzing, 13 DEGs (MYOF, SLC6A6, S100P, HK2, IFI44L, OSBPL3, IGF2BP3, PDK4, IL1R2, ERO1A, EGLN3, PLAC8 and ACSL5) are significantly differentially expressed in four microarray databases in common. After analyzing mRNA expression data and clinical follow-up survey provided in the TCGA database and clinicopathological data of 137 pancreatic ductal adenocarcinoma patients, we carefully demonstrated that three of these differentially expressed genes (ERO1A, OSBPL3 and IFI44L) are correlated with poor prognosis of pancreatic ductal adenocarcinoma patients. In addition, we revealed that cell–matrix adhesion and extracellular matrix were top significantly regulated pathways in pancreatic ductal adenocarcinoma and depicted two protein-protein interactions networks of extracellular matrix related Genes which are dysregulated according to 4 gene expression microarray data mentioned above (“GSE15471”, “GSE18670”, “GSE28735” and “GSE58561”), hoping to shed light on the etiology of PDAC and mechanisms of drug resistance in PDAC in this study.

Cells of origin of pancreatic neoplasms

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignant disease associated with poor prognosis, despite recent medical advances. It is of great importance to understand the initial events and cells of origin of pancreatic cancer to prevent the development and progression of PDAC. There are three distinct precursor lesions that develop into PDAC: pancreatic intraepithelial neoplasms (PanINs), intraductal papillary mucinous neoplasms (IPMNs), and mucinous cystic neoplasms (MCNs). Studies on genetically engineered mouse models have revealed that the initiation and development of these lesions largely depend on genetic alterations. These lesions originate from different populations in the pancreas. PanIN development seems to be the result of the transdifferentiation of acinar cells, whereas IPMNs most likely arise from the progenitor niche of the pancreatic ductal epithelium. Pancreatic carcinogenesis is dependent on various events, including gene alterations, environmental insults, and cell types. However, further studies are needed to fully understand the initial processes of pancreatic cancer.

Chronic inflammation initiates multiple forms of K-Ras-independent mouse pancreatic cancer in the absence of TP53

Chronic inflammation (CI) is a risk factor for pancreatic cancer (PC) including the most common type, ductal adenocarcinoma (PDAC), but its role and the mechanisms involved are unclear. To investigate the role of CI in PC, we generated genetic mouse models with pancreatic specific CI in the presence or absence of TP53. Mice were engineered to express either cyclooxygenase-2 (COX-2) or IκB kinase-2 (IKK2), and TP53^+/+ or TP53^f/f specifically in adult pancreatic acinar cells by using a full-length pancreatic elastase promoter-driven Cre. Animals were followed for >80 weeks and pancreatic lesions were evaluated histologically and immunohistochemically. The presence of K-ras mutations was assessed by direct sequencing, locked nuclei acid (LNA)-based PCR, and immunohistochemistry. We observed that sustained COX-2/IKK2 expression caused histological abnormalities of pancreas, including increased immune cell infiltration, proliferation rate and DNA damage. A minority of animals with CI developed pre-neoplastic lesions, but cancer was not observed in any TP53^+/+ animals within 84 weeks. In contrast, all animals with CI-lacking TP53 developed various subtypes of PC, including acinar cell carcinoma, ductal adenocarcinoma, sarcomatoid carcinoma and neuroendocrine tumors, and all died within 65 weeks. No evidence of K-ras mutations was observed. Variations in the activity of the Hippo, pERK and c-Myc pathways were found in the diverse cancer subtypes. In summary, chronic inflammation is extremely inefficient at inducing PC in the presence of TP53. However, in the absence of TP53, CI leads to the development of several rare K-ras-independent forms of PC, with infrequent PDAC. This may help explain the rarity of PDAC in persons with chronic inflammatory conditions.

Genetic ablation of Smoothened in pancreatic fibroblasts increases acinar-ductal metaplasia

Liu et al. show that disruption of paracrine Hedgehog signaling via genetic ablation of Smoothened (Smo) in stromal fibroblasts in a Kras^G12D mouse model increased acinar-to-ductal metaplasia (ADM). Smo-deleted fibroblasts had higher expression of transforming growth factor-α (Tgfα) mRNA and secreted higher levels of TGFα, leading to activation of EGFR signaling in acinar cells and increased ADM.

The contribution of the microenvironment to pancreatic acinar-to-ductal metaplasia (ADM), a preneoplastic transition in oncogenic Kras-driven pancreatic cancer progression, is currently unclear. Here we show that disruption of paracrine Hedgehog signaling via genetic ablation of Smoothened (Smo) in stromal fibroblasts in a Kras^G12D mouse model increased ADM. Smo-deleted fibroblasts had higher expression of transforming growth factor-α (Tgfa) mRNA and secreted higher levels of TGFα, leading to activation of EGFR signaling in acinar cells and increased ADM. The mechanism involved activation of AKT and noncanonical activation of the GLI family transcription factor GLI2. GLI2 was phosphorylated at Ser230 in an AKT-dependent fashion and directly regulated Tgfa expression in fibroblasts lacking Smo. Additionally, Smo-deleted fibroblasts stimulated the growth of Kras^G12D/Tp53^R172H pancreatic tumor cells in vivo and in vitro. These results define a non-cell-autonomous mechanism modulating Kras^G12D-driven ADM that is balanced by cross-talk between Hedgehog/SMO and AKT/GLI2 pathways in stromal fibroblasts.

KRAS-related proteins in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly metastatic disease with a high mortality rate. Genetic and biochemical studies have shown that RAS signaling mediated by KRAS plays a pivotal role in disease initiation, progression and drug resistance. RAS signaling affects several cellular processes in PDAC, including cellular proliferation, migration, cellular metabolism and autophagy. 90% of pancreatic cancer patients harbor somatic oncogenic point mutations in KRAS, which lead to constitutive activation of the molecule. Pancreatic cancers lacking KRAS mutations show activation of RAS via upstream signaling through receptor mediated tyrosine kinases, like EGFR, and in a small fraction of patients, oncogenic activation of the downstream B-RAF molecule is detected. RAS-stimulated signaling of RAF/MEK/ERK, PI3K/AKT/mTOR and RalA/B is active in human pancreatic cancers, cancer cell lines and mouse models of PDAC, although activation levels of each signaling arm appear to be variable across different tumors and perhaps within different subclones of single tumors. Recently, several targeted therapies directed towards MEK, ERK, PI3K and mTOR have been assayed in pancreatic cancer cell lines and in mouse models of the disease with promising results for their ability to impede cellular growth or delay tumor formation, and several inhibitors are currently in clinical trials. However, therapy-induced cross activation of RAS effector molecules has elucidated the complexities of targeting RAS signaling. Combinatorial therapies are now being explored as an approach to overcome RAS-induced therapeutic resistance in pancreatic cancer.

Study of Clinical Survival and Gene Expression in a Sample of Pancreatic Ductal Adenocarcinoma by Parsimony Phylogenetic Analysis

Pancreatic ductal adenocarcinoma (PDAC) is one of the rapidly growing forms of pancreatic cancer with a poor prognosis and less than 5% 5-year survival rate. In this study, we characterized the genetic signatures and signaling pathways related to survival from PDAC, using a parsimony phylogenetic algorithm. We applied the parsimony phylogenetic algorithm to analyze the publicly available whole-genome in silico array analysis of a gene expression data set in 25 early-stage human PDAC specimens. We explain here that the parsimony phylogenetics is an evolutionary analytical method that offers important promise to uncover clonal (driver) and nonclonal (passenger) aberrations in complex diseases. In our analysis, parsimony and statistical analyses did not identify significant correlations between survival times and gene expression values. Thus, the survival rankings did not appear to be significantly different between patients for any specific gene (p > 0.05). Also, we did not find correlation between gene expression data and tumor stage in the present data set. While the present analysis was unable to identify in this relatively small sample of patients a molecular signature associated with pancreatic cancer prognosis, we suggest that future research and analyses with the parsimony phylogenetic algorithm in larger patient samples are worthwhile, given the devastating nature of pancreatic cancer and its early diagnosis, and the need for novel data analytic approaches. The future research practices might want to place greater emphasis on phylogenetics as one of the analytical paradigms, as our findings presented here are on the cusp of this shift, especially in the current era of Big Data and innovation policies advocating for greater data sharing and reanalysis.

Inhibition of JNK-mediated autophagy enhances NSCLC cell sensitivity to mTORC1/2 inhibitors

As the activation of autophagy contributes to the efficacy of many anticancer therapies, deciphering the precise role of autophagy in cancer therapy is critical. Here, we report that the dual mTORC1/2 inhibitors PP242 and OSI-027 decreased cell viability but did not induce apoptosis in the non-small cell lung cancer (NSCLC) cell lines H460 and A549. PP242 induced autophagy in NSCLC cells as demonstrated by the formation of massive vacuoles and acidic vesicular organelles and the accumulation of LC3-II. JNK was activated by PP242, and PP242-induced autophagy was blocked by inhibiting JNK pathway with SP600125 or JNK siRNA, suggesting that JNK activation is required for the mTORC1/2 inhibitor-mediated induction of autophagy in NSCLC cells. Inhibiting JNK or autophagy increased the sensitivity of H460 cells to mTORC1/2 inhibitors, indicating that JNK or autophagy promoted survival in NSCLC cells treated with mTORC1/2 inhibitors. Together, these data suggest that combining mTORC1/2 inhibitors with inhibitors of JNK or autophagy might be an effective approach for improving therapeutic outcomes in NSCLC.

Genetics and biology of pancreatic ductal adenocarcinoma

Ying et al. review pancreatic ductal adenocarcinoma (PDAC) genetics and biology, particularly altered cancer cell metabolism, the complexity of immune regulation in the tumor microenvironment, and impaired DNA repair processes.

With 5-year survival rates remaining constant at 6% and rising incidences associated with an epidemic in obesity and metabolic syndrome, pancreatic ductal adenocarcinoma (PDAC) is on track to become the second most common cause of cancer-related deaths by 2030. The high mortality rate of PDAC stems primarily from the lack of early diagnosis and ineffective treatment for advanced tumors. During the past decade, the comprehensive atlas of genomic alterations, the prominence of specific pathways, the preclinical validation of such emerging targets, sophisticated preclinical model systems, and the molecular classification of PDAC into specific disease subtypes have all converged to illuminate drug discovery programs with clearer clinical path hypotheses. A deeper understanding of cancer cell biology, particularly altered cancer cell metabolism and impaired DNA repair processes, is providing novel therapeutic strategies that show strong preclinical activity. Elucidation of tumor biology principles, most notably a deeper understanding of the complexity of immune regulation in the tumor microenvironment, has provided an exciting framework to reawaken the immune system to attack PDAC cancer cells. While the long road of translation lies ahead, the path to meaningful clinical progress has never been clearer to improve PDAC patient survival.

Report on the use of non-clinical studies in the regulatory evaluation of oncology drugs

Non‐clinical studies are necessary at each stage of the development of oncology drugs. Many experimental cancer models have been developed to investigate carcinogenesis, cancer progression, metastasis, and other aspects in cancer biology and these models turned out to be useful in the efficacy evaluation and the safety prediction of oncology drugs. While the diversity and the degree of engagement in genetic changes in the initiation of cancer cell growth and progression are widely accepted, it has become increasingly clear that the roles of host cells, tissue microenvironment, and the immune system also play important roles in cancer. Therefore, the methods used to develop oncology drugs should continuously be revised based on the advances in our understanding of cancer. In this review, we extensively summarize the effective use of those models, their advantages and disadvantages, ranges to be evaluated and limitations of the models currently used for the development and for the evaluation of oncology drugs.

This review summarizes the effective use of animal models, their advantages and disadvantages, ranges to be evaluated and limitations of the models currently used for the development and for the evaluation of oncology drugs.

Effects of orexin A on glucose metabolism in human hepatocellular carcinoma in vitro via PI3K/Akt/mTOR-dependent and -independent mechanism

Orexins are hypothalamic neuropeptides that regulate food intake, energy homeostasis, reward system and sleep/wakefulness states. The purpose of this study was to investigate the effects of orexin A on glucose metabolism in human hepatocellular carcinoma cell line, Hep3B, and determine the possible mechanisms. Hep3B cells were incubated with different concentrations of orexin A (10(-9)-10(-7) M) in vitro in the presence or absence of the orexin receptor 1 (OX1R) inhibitor (SB334867), Akt inhibitor (PF-04691502) and mammalian target of rapamycin (mTOR) inhibitor (temsirolimus). Subsequently, OX1R protein expression, glucose transporter 1 (GLUT1) expression, glucose uptake, the mRNA expression of lactate dehydrogenase (LDHA), pyruvate dehydrogenase kinase 1 (PDK1) and pyruvate dehydrogenase B (PDHB), lactate generation and mitochondrial pyruvate dehydrogenase (PDH) enzyme activity were measured. The activity of phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling was also determined. OX1R was expressed in hepatoma tissues and Hep3B cells. Stimulation of the Hep3B cells with orexin A resulted in a dose-dependent increase of GLUT1 expression and glucose uptake, which was associated with the activation of PI3K/Akt/mTOR pathway. Further, orexin A increased PDHB expression and PDH enzyme activity, decreased LDHA, PDK1 mRNA levels and lactate generation independent of PI3K/Akt/mTOR pathway. Our results demonstrated that orexin A directed the cellular metabolism towards mitochondrial glucose oxidation rather than glycolysis. These findings provide functional evidence of the metabolic actions of orexin A in hepatocellular carcinoma cells.

RAS signaling and anti-RAS therapy: lessons learned from genetically engineered mouse models, human cancer cells, and patient-related studies

Activating mutations of oncogenic RAS genes are frequently detected in human cancers. The studies in genetically engineered mouse models (GEMMs) reveal that Kras-activating mutations predispose mice to early onset tumors in the lung, pancreas, and gastrointestinal tract. Nevertheless, most of these tumors do not have metastatic phenotypes. Metastasis occurs when tumors acquire additional genetic changes in other cancer driver genes. Studies on clinical specimens also demonstrated that KRAS mutations are present in premalignant tissues and that most of KRAS mutant human cancers have co-mutations in other cancer driver genes, including TP53, STK11, CDKN2A, and KMT2C in lung cancer; APC, TP53, and PIK3CA in colon cancer; and TP53, CDKN2A, SMAD4, and MED12 in pancreatic cancer. Extensive efforts have been devoted to develop therapeutic agents that target enzymes involved in RAS posttranslational modifications, that inhibit downstream effectors of RAS signaling pathways, and that kill RAS mutant cancer cells through synthetic lethality. Recent clinical studies have revealed that sorafenib, a pan-RAF and VEGFR inhibitor, has impressive benefits for KRAS mutant lung cancer patients. Combination therapy of MEK inhibitors with either docetaxel, AKT inhibitors, or PI3K inhibitors also led to improved clinical responses in some KRAS mutant cancer patients. This review discusses knowledge gained from GEMMs, human cancer cells, and patient-related studies on RAS-mediated tumorigenesis and anti-RAS therapy. Emerging evidence demonstrates that RAS mutant cancers are heterogeneous because of the presence of different mutant alleles and/or co-mutations in other cancer driver genes. Effective subclassifications of RAS mutant cancers may be necessary to improve patients' outcomes through personalized precision medicine.

Constitutively active Akt1 cooperates with KRas(G12D) to accelerate in vivo pancreatic tumor onset and progression

BACKGROUND AND AIMS: Pancreatic adenocarcinoma is a deadly disease characterized by metastatic progression and resistance to conventional therapeutics. Mutation of KRAS is the most frequent early event in pancreatic tumor progression. AKT isoforms are frequently activated in pancreatic cancer, and reports have implicated hyperactivation of AKT1, as well as AKT2, in pancreatic tumor formation. The objective here is to delineate the role of AKT in facilitating in vivo pancreatic tumor progression in the context of KRAS mutation and predisposition to pancreatic cancer. METHODS: Mice with Akt1 and KRas mutant alleles expressed using the pancreas Pdx promoter were mated to characterize the incidence and frequency of histologic and genetic alterations known to occur commonly in human pancreatic ductal adenocarcinoma. RESULTS: Active Akt1 (Akt1^Myr, containing a myristoylation sequence) cooperated with active mutant KRas^G12D to accelerate pancreatic carcinoma onset and progression and increase phosphorylation of downstream effectors in the Akt pathway. Mucin and smooth muscle actin expression was found in and around pancreatic intraepithelial neoplasms (PanINs), and accelerated time to metastasis was found in Akt1^Myr/KRas^G12D mice. CONCLUSIONS: In contrast to prior reports of pancreatic KRas mutant mice mated with mice deficient for various tumor suppressor genes, which resulted in aggressive disease within a few months of age, Akt1^Myr/KRas^G12D mice enabled the study of PanINs and spontaneous pancreatic transformation more characteristic of human pancreatic progression in elderly individuals. The Akt1^Myr/KRas^G12D model holds promise for delineating the tumor biology and biomarkers critical for understanding their cooperation in cancer oncogenesis and future targeting in therapeutic strategies.

Wild-Type Hras Suppresses the Earliest Stages of Tumorigenesis in a Genetically Engineered Mouse Model of Pancreatic Cancer

Oncogenic, activating mutations in KRAS initiate pancreatic cancer. There are, however, two other Ras family members, Nras and Hras, which can be activated in the presence of oncogenic Kras. The role of these wild-type Ras proteins in cancer remains unclear, as their disruption has been shown to enhance or inhibit tumorigenesis depending upon the context. As pancreatic cancer is critically dependent upon Ras signaling, we tested and now report that loss of Hras increases tumor load and reduces survival in an oncogenic Kras-driven pancreatic adenocarcinoma mouse model. These effects were traced to the earliest stages of pancreatic cancer, suggesting that wild-type Hras may suppress tumor initiation. In normal cells, activated Ras can suppress proliferation through p53-dependent mechanisms. We find that the tumor suppressive effects of Hras are nullified in a homozygous mutant p53 background. As such, loss of wild-type Hras fosters the earliest stages of pancreatic cancer in a p53-dependent manner.

Molecular signature of pancreatic adenocarcinoma: an insight from genotype to phenotype and challenges for targeted therapy

INTRODUCTION

Pancreatic adenocarcinoma remains one of the most clinically challenging cancers despite an in-depth characterization of the molecular underpinnings and biology of this disease. Recent whole-genome-wide studies have elucidated the diverse and complex genetic alterations which generate a unique oncogenic signature for an individual pancreatic cancer patient and which may explain diverse disease behavior in a clinical setting.

AREAS COVERED

In this review article, we discuss the key oncogenic pathways of pancreatic cancer including RAS-MAPK, PI3KCA and TGF-β signaling, as well as the impact of these pathways on the disease behavior and their potential targetability. The role of tumor suppressors particularly BRCA1 and BRCA2 genes and their role in pancreatic cancer treatment are elaborated upon. We further review recent genomic studies and their impact on future pancreatic cancer treatment.

EXPERT OPINION

Targeted therapies inhibiting pro-survival pathways have limited impact on pancreatic cancer outcomes. Activation of pro-apoptotic pathways along with suppression of cancer-stem-related pathways may reverse treatment resistance in pancreatic cancer. While targeted therapy or a 'precision medicine' approach in pancreatic adenocarcinoma remains an elusive challenge for the majority of patients, there is a real sense of optimism that the strides made in understanding the molecular underpinnings of this disease will translate into improved outcomes.

GEMMs as preclinical models for testing pancreatic cancer therapies

Pancreatic ductal adenocarcinoma is the most common form of pancreatic tumour, with a very limited survival rate and currently no available disease-modifying treatments. Despite recent advances in the production of genetically engineered mouse models (GEMMs), the development of new therapies for pancreatic cancer is still hampered by a lack of reliable and predictive preclinical animal models for this disease. Preclinical models are vitally important for assessing therapies in the first stages of the drug development pipeline, prior to their transition to the clinical arena. GEMMs carry mutations in genes that are associated with specific human diseases and they can thus accurately mimic the genetic, phenotypic and physiological aspects of human pathologies. Here, we discuss different GEMMs of human pancreatic cancer, with a focus on the Lox-Stop-Lox (LSL)-Kras(G12D); LSL-Trp53(R172H); Pdx1-cre (KPC) model, one of the most widely used preclinical models for this disease. We describe its application in preclinical research, highlighting its advantages and disadvantages, its potential for predicting clinical outcomes in humans and the factors that can affect such outcomes, and, finally, future developments that could advance the discovery of new therapies for pancreatic cancer.

Critical role of NF-κB in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, and in spite of intense efforts there are limited therapeutic options for patients with PDAC. PDACs harbor a high frequency of Kras mutations and other driver mutations that lead to altered signaling pathways and contribute to therapeutic resistance. Importantly, constitutive activation of nuclear factor κB (NF-κB) is frequently observed in PDAC. An increasing body of evidence suggests that both classical and non-classical NF-κB pathways play a crucial role in PDAC development and progression. In this review, we update the most recent advances regarding different aspects of NF-κB involvement in PDAC development and progression, emphasizing its potential as a therapeutic target and the need to discover pathway-specific cytosolic NF-κB regulators which could be used to design novel therapeutic strategies for PDAC.

Reserve stem cells: Differentiated cells reprogram to fuel repair, metaplasia, and neoplasia in the adult gastrointestinal tract

It has long been known that differentiated cells can switch fates, especially in vitro, but only recently has there been a critical mass of publications describing the mechanisms adult, postmitotic cells use in vivo to reverse their differentiation state. We propose that this sort of cellular reprogramming is a fundamental cellular process akin to apoptosis or mitosis. Because reprogramming can invoke regenerative cells from mature cells, it is critical to the long-term maintenance of tissues like the pancreas, which encounter large insults during adulthood but lack constitutively active adult stem cells to repair the damage. However, even in tissues with adult stem cells, like the stomach and intestine, reprogramming may allow mature cells to serve as reserve ("quiescent") stem cells when normal stem cells are compromised. We propose that the potential downside to reprogramming is that it increases risk for cancers that occur late in adulthood. Mature, long-lived cells may have years of exposure to mutagens. Mutations that affect the physiological function of differentiated, postmitotic cells may lead to apoptosis, but mutations in genes that govern proliferation might not be selected against. Hence, reprogramming with reentry into the cell cycle might unmask those mutations, causing an irreversible progenitor-like, proliferative state. We review recent evidence showing that reprogramming fuels irreversible metaplastic and precancerous proliferation in the stomach and pancreas. Finally, we illustrate how we think reprogrammed differentiated cells are likely candidates as cells of origin for cancers of the intestine.

Sp1-driven up-regulation of miR-19a decreases RHOB and promotes pancreatic cancer

Cancer treatment alters microRNA (miRNA) expression, revealing potential therapeutic targets (oncotarget). Here we treated pancreatic cancer (ASPC-1) cells with either recombinant human endostatin (rh-endostatin) or gemcitabine. Then high-throughput sequencing assay was performed to screen for altered miRNAs. Both treatments decreased levels of MiR-19a. We found that miR-19a stimulated cell proliferation, migration, invasion in vitro and tumor growth in vivo. High levels of miR-19a correlated with poor prognosis in patients. Ras homolog family member B (RHOB) was identified as a direct target of miR-19a. Furthermore, RHOB was down-regulated in human pancreatic cancer samples. Restoration of RHOB induced apoptosis, inhibited proliferation and migration of ASPC-1 cells. SP-1 was identified as an upstream transcription factor of miR-19a gene, promoting miR-19a transcription. Rh-endostatin decreased miR-19a expression by down-regulating SP-1. These findings suggest that miR-19a is a potential therapeutic target in pancreatic cancer.

A Transition Zone Showing Highly Discontinuous or Alternating Levels of Stem Cell and Proliferation Markers Characterizes the Development of PTEN-Haploinsufficient Colorectal Cancer

BACKGROUND

Stepwise acquisition of oncogene mutations and deletion/inactivation of tumor suppressor genes characterize the development of colorectal cancer (CRC). These genetic events interact with discrete morphologic transitions from hyperplastic mucosa to adenomatous areas, followed by in situ malignant transformation and finally invasive carcinoma. The goal of this study was to identify tissue markers of the adenoma-carcinoma morphogenetic transitions in CRC.

METHODS AND FINDINGS

We analyzed the patterns of expression of growth regulatory and stem cell markers across these distinct morphologic transition zones in 735 primary CRC tumors. In 202 cases with preserved adenoma-adenocarcinoma transition, we identified, in 37.1% of cases, a zone of adenomatous epithelium, located immediately adjacent to the invasive component, that showed rapidly alternating intraglandular stretches of PTEN+ and PTEN- epithelium. This zone exactly overlapped with similar alternating expression of Ki-67 and inversely with the transforming growth factor-beta (TGF-β) growth regulator SMAD4. These zones also show parallel alternating levels and/or subcellular localization of multiple cancer stem/progenitor cell (CSC) markers, including β-catenin/CTNNB1, ALDH1, and CD44. PTEN was always re-expressed in the invasive tumor in these cases, unlike those with complete loss of PTEN expression. Genomic microarray analysis of CRC with prominent CSC-like expansions demonstrated a high frequency of PTEN genomic deletion/haploinsufficiency in tumors with CSC-like transition zones (62.5%) but not in tumors with downregulated but non-alternating PTEN expression (14.3%). There were no significant differences in the levels of KRAS mutation or CTNNB1 mutation in CSC-like tumors as compared to unselected CRC cases.

CONCLUSIONS

In conclusion, we have identified a distinctive CSC-like pre-invasive transition zone in PTEN-haploinsufficient CRC that shows convergent on-off regulation of the PTEN/AKT, TGF-β/SMAD and Wnt/β-catenin pathways. This bottleneck-like zone is usually followed by the emergence of invasive tumors with intact PTEN expression but dysregulated TP53 and uniformly high proliferation rates.

Implication of PI3K/Akt pathway in pancreatic cancer: When PI3K isoforms matter?

Pancreatic cancer belongs to the incurable family of solid cancers. Despite of a recent better understanding its molecular biology, and an increased number of clinical trials, there is still a lack for innovative targeted therapies to fight this deadly malignancy. PI3K/Akt signalling is one of the most commonly deregulated signalling pathways in cancer, which explains the massive attention from many pharmaceutical companies over the ten past years on these signalling molecules. The already developed small molecule inhibitors are currently under clinical trial in various cancer types. Class I PI3Ks have 4 isoforms for which the role in physiology starts to be well described in the literature. Data are more unclear for their differential involvement in oncogenesis. In this review, we will discuss about the cognitive and therapeutic potential of targeting this signalling pathway and in particular Class I PI3K isoforms for pancreatic cancer treatment. Isoform-specificity of PI3K inhibitors are currently designed to achieve the same goal as pan-PI3K inhibitors but without potential adverse effects. We will discuss if such strategy is relevant in pancreatic adenocarcinoma.

New insights into pancreatic cancer stem cells

Pancreatic cancer (PC) has been one of the deadliest of all cancers, with almost uniform lethality despite aggressive treatment. Recently, there have been important advances in the molecular, pathological and biological understanding of pancreatic cancer. Even after the emergence of recent new targeted agents and the use of multiple therapeutic combinations, no treatment option is viable in patients with advanced cancer. Developing novel strategies to target progression of PC is of intense interest. A small population of pancreatic cancer stem cells (CSCs) has been found to be resistant to chemotherapy and radiation therapy. CSCs are believed to be responsible for tumor initiation, progression and metastasis. The CSC research has recently achieved much progress in a variety of solid tumors, including pancreatic cancer to some extent. This leads to focus on understanding the role of pancreatic CSCs. The focus on CSCs may offer new targets for prevention and treatment of this deadly cancer. We review the most salient developments in important areas of pancreatic CSCs. Here, we provide a review of current updates and new insights on the role of CSCs in pancreatic tumor progression with special emphasis on DclK1 and Lgr5, signaling pathways altered by CSCs, and the role of CSCs in prevention and treatment of PC.

p85α is a microRNA target and affects chemosensitivity in pancreatic cancer

BACKGROUND

We previously identified a correlation between increased expression of the phosphoinositide 3-kinase (PI3K) regulatory subunit p85α and improved survival in human pancreatic ductal adenocarcinoma (PDAC). The purpose of this study was to investigate the impact of changes in p85α expression on response to chemotherapy and the regulation of p85α by microRNA-21 (miR-21).

MATERIALS AND METHODS

PDAC tumor cells overexpressing p85α were generated by viral transduction, and the effect of p85α overexpression on sensitivity to gemcitabine was tested by MTT assay. Primary human PDAC tumors were stained for p85α and miR-21 via immunohistochemistry and in situ hybridization, respectively. Additionally, PDAC cells were treated with miR-21 mimic, and changes in p85α and phospho-AKT were assessed by Western blot. Finally, a luciferase reporter assay system was used to test direct regulation of p85α by miR-21.

RESULTS

Higher p85α expression resulted in increased sensitivity to gemcitabine (P < 0.01), which correlated with decreased PI3K-AKT activation. Human tumors demonstrated an inverse correlation between miR-21 and p85α expression levels (r = -0.353, P < 0.001). In vitro, overexpression of miR-21 resulted in decreased levels of p85α and increased phosphorylation of AKT. Luciferase reporter assays confirmed the direct regulation of p85α by miR-21 (P < 0.01).

CONCLUSIONS

Our results demonstrate that p85α expression is a determinant of chemosensitivity in PDAC. Additionally, we provide novel evidence that miR-21 can influence PI3K-AKT signaling via its direct regulation of p85α. These data provide insight into potential mechanisms for the known relationship between increased p85α expression and improved survival in PDAC.

Low expression of the E3 ubiquitin ligase CBL confers chemoresistance in human pancreatic cancer and is targeted by epidermal growth factor receptor inhibition

PURPOSE

Expression of CBL, an ubiquitin ligase, is decreased in 60% of human pancreatic ductal adenocarcinomas (PDAC) and is associated with shorter overall survival. We sought to determine how low CBL directly contributes to clinically more aggressive PDAC.

EXPERIMENTAL DESIGN

Human PDACs were stained for CBL, pEGFR, and EGFR. CBL-low was modeled in PDAC cells (Panc-1, L3.6pl, and AsPC-1) via transient transfection (siRNA) or stable knockdown (shRNA). Cell viability and apoptosis were measured by MTT assays and FACS. Immunoblot and a phospho-receptor tyrosine kinase (pRTK) array were used to probe signal transduction. NOD-scid-IL2Rγ(null) mice were subcutaneously implanted with PDAC or PDAC(CBL-low) cells on opposite flanks and treated with gemcitabine ± erlotinib for ≥4 weeks.

RESULTS

There was an inverse correlation between CBL and pEGFR protein expression in 12 of 15 tumors. CBL knockdown increased PDAC resistance to gemcitabine and 5-fluorouracil (5-FU) by upregulating pEGFR (Y1068), pERK, and pAKT. A pRTK array of PDAC(CBL-low) cells revealed additional activated tyrosine kinases but all to a much lower magnitude than EGFR. Increased chemoresistance from low CBL was abrogated by the EGFR inhibitor erlotinib both in vitro and in vivo. Erlotinib+gemcitabine-treated PDAC(CBL-low) cells exhibited greater apoptosis by cleaved PARP, caspase-3, and Annexin V/PI.

CONCLUSIONS

Low CBL causes chemoresistance in PDAC via stress-induced EGFR activation that can be effectively abrogated by EGFR inhibition. These results suggest that dysregulation of ubiquitination is a key mechanism of EGFR hyperactivation in PDAC and that low CBL may define PDAC tumors likely to respond to erlotinib treatment.

Pancreatic cell plasticity and cancer initiation induced by oncogenic Kras is completely dependent on wild-type PI 3-kinase p110α

Increased PI 3-kinase (PI3K) signaling in pancreatic ductal adenocarcinoma (PDAC) correlates with poor prognosis, but the role of class I PI3K isoforms during its induction remains unclear. Using genetically engineered mice and pharmacological isoform-selective inhibitors, we found that the p110α PI3K isoform is a major signaling enzyme for PDAC development induced by a combination of genetic and nongenetic factors. Inactivation of this single isoform blocked the irreversible transition of exocrine acinar cells into pancreatic preneoplastic ductal lesions by oncogenic Kras and/or pancreatic injury. Hitting the other ubiquitous isoform, p110β, did not prevent preneoplastic lesion initiation. p110α signaling through small GTPase Rho and actin cytoskeleton controls the reprogramming of acinar cells and regulates cell morphology in vivo and in vitro. Finally, p110α was necessary for pancreatic ductal cancers to arise from Kras-induced preneoplastic lesions by increasing epithelial cell proliferation in the context of mutated p53. Here we identify an in vivo context in which p110α cellular output differs depending on the epithelial transformation stage and demonstrate that the PI3K p110α is required for PDAC induced by oncogenic Kras, the key driver mutation of PDAC. These data are critical for a better understanding of the development of this lethal disease that is currently without efficient treatment.

Cooperative interactions of PTEN deficiency and RAS activation in melanoma metastasis

Melanoma displays frequent activation of RAS/RAF/MAPK and PI3K/AKT signaling pathways as well as inactivation of CDKN2A (INK4a/ARF) and PTEN tumor suppressors via genetic and epigenetic alterations. Pathogenetic roles of these melanoma-prone mutations and their genetic interactions have been established in genetically engineered mouse models. Here, we catalog frequent genetic alterations observed in human melanomas and describe mouse models of melanoma initiation and progression, including our recent study that investigated the genetic interactions of RAS activation and PTEN loss in a CDKN2A (INK4a/ARF) null melanoma prone genetic background. We showed that loss of PTEN cooperates with HRAS activation, leading to increased development of melanoma and emergence of metastasis. Moreover, we observed that RNA i-mediated PTEN inactivation in RAS-driven melanomas enhanced migration and invasion with concomitant downregulation of E-cadherin, the major regulator of epithelial and mesenchymal transition, and enhanced AKT2 phosphorylation, which has been previously linked to invasion and metastasis of several cancer types, including breast and ovary. These data show that activated RAS cooperates with PTEN loss in melanoma genesis and progression.

PTEN expression and function in adult cancer stem cells and prospects for therapeutic targeting

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) is a non-redundant lipid phosphatase that restrains and fine tunes the phosphatidylinositol-3-kinase (PI3K) signaling pathway. PTEN is involved in inherited syndromes, which predispose to different types of cancers and is among the most frequently inactivated tumor suppressor genes in sporadic cancers. Indeed, loss of PTEN function occurs in a wide spectrum of human cancers through a variety of mechanisms, including mutations, deletions, transcriptional silencing, or protein instability. PTEN prevents tumorigenesis through multiple mechanisms and regulates a plethora of cellular processes, including survival, proliferation, energy metabolism and cellular architecture. Moreover, recent studies have demonstrated that PTEN is able to exit, exist, and function outside the cell, allowing for inhibition of the PI3K pathway in neighboring cells in a paracrine fashion. Most recently, studies have shown that PTEN is also critical for stem cell maintenance and that PTEN loss can lead to the emergence and proliferation of cancer stem cell (CSC) clones. Depending on the cellular and tissue context of origin, PTEN deletion may result in increased self-renewal capacity or normal stem cell exhaustion and PTEN-defìcient stem and progenitor cells have been reported in prostate, lung, intestinal, and pancreatic tissues before tumor formation; moreover, reversible or irreversible PTEN loss is frequently observed in CSC from a variety of solid and hematologic malignancies, where it may contribute to the functional phenotype of CSC. In this review, we will focus on the role of PTEN expression and function and downstream pathway activation in cancer stem cell biology and regulation of the tumorigenic potential; the emerging role of PTEN in mediating the crosstalk between the PI3K and MAPK pathways will also be discussed, together with prospects for the therapeutic targeting of tumors lacking PTEN expression.

miR-148a- and miR-216a-regulated oncolytic adenoviruses targeting pancreatic tumors attenuate tissue damage without perturbation of miRNA activity

Oncolytic virotherapy shows promise for pancreatic ductal adenocarcinoma (PDAC) treatment, but there is the need to minimize associated-toxicities. In the current work, we engineered artificial target sites recognized by miR-216a and/or miR-148a to provide pancreatic tumor-selectivity to replication-competent adenoviruses (Ad-miRTs) and improve their safety profile. Expression analysis in PDAC patients identified miR-148a and miR-216a downregulated in resectable (FC(miR-148a) = 0.044, P < 0.05; FC(miR-216a) = 0.017, P < 0.05), locally advanced (FC(miR-148a) = 0.038, P < 0.001; FC(miR-216a) = 0.001, P < 0.001) and metastatic tumors (FC(miR-148a) = 0.041, P < 0.01; FC(miR-216a) = 0.002, P < 0.001). In mouse tissues, miR-216a was highly specific of the exocrine pancreas whereas miR-148a was abundant in the exocrine pancreas, Langerhans islets, and the liver. In line with the miRNA content and the miRNA target site design, we show E1A gene expression and viral propagation efficiently controlled in Ad-miRT-infected cells. Consequently, Ad-miRT-infected mice presented reduced pancreatic and liver damage without perturbation of the endogenous miRNAs and their targets. Interestingly, the 8-miR148aT design showed repressing activity by all miR-148/152 family members with significant detargeting effects in the pancreas and liver. Ad-miRTs preserved their oncolytic activity and triggered strong antitumoral responses. This study provides preclinical evidences of miR-148a and miR-216a target site insertions to confer adenoviral selectivity and proposes 8-miR148aT as an optimal detargeting strategy for genetically-engineered therapies against PDAC.

Emerging role of the KRAS-PDK1 axis in pancreatic cancer

Pancreatic cancer is a highly aggressive tumour that is very resistant to treatments and it is rarely diagnosed early because of absence of specific symptoms. Therefore, the prognosis for this disease is very poor and it has the grim supremacy in terms of unfavourable survival rates. There have been great advances in survival rates for many types of cancers over the past few decades but hardly any change for pancreatic cancer. Mutations of the Ras oncogene are the most frequent oncogenic alterations in human cancers. The frequency of KRAS mutations in pancreatic cancer is around 90%. Given the well-established role of KRAS in cancer it is not surprising that it is one of the most attractive targets for cancer therapy. Nevertheless, during the last thirty years all attempts to target directly KRAS protein have failed. Therefore, it is crucial to identify downstream KRAS effectors in order to develop specific drugs able to counteract activation of this pathway. Among the different signalling pathways activated by oncogenic KRAS, the phosphoinositide 3-Kinase (PI3K) pathway is emerging as one of the most critical KRAS effector. In turn, PI3K activates several parallel pathways making the identification of the precise effectors activated by KRAS/PI3K more difficult. Recent data identify 3-phosphoinositide-dependent protein kinase 1 as a key tumour-initiating event downstream KRAS interaction with PI3K in pancreatic cancer.

Angiopoietin-like protein 2 negatively regulated by microRNA-25 contributes to the malignant progression of colorectal cancer

Angiopoietin-like protein 2 (ANGPTL2) is associated with tumor progression while dysregulation of its expression has been observed in various types of cancer. However, the expression and role of ANGPTL2 remain exclusive in colorectal cancer (CRC). In the present study, we determined the expression levels of ANGPTL2 in CRC tissues and cells. The roles of ANGPTL2 and miR-25 in the migration and invasion of CRC SW620 and HCT-116 cells were also investigated using transwell assays or scratch wound assays. The results showed that ANGPTL2 increased with metastatic progression. Increased ANGPTL2 and decreased microRNA-25 (miR-25) expression were found to coexist in CRC. The functional studies revealed that knockdown of ANGPTL2 reduced colony formation, and the invasive and migratory abilities of human CRC SW620 and HCT-116 cells. Similarly, overexpression of miR-25 resulted in reduced colony formation, invasion and migration in both cell lines. The overexpression of miR-25 led to a decreased ANGPTL2 mRNA and protein expression, whereas the downregulation of miR-25 resulted in increased ANGPTL2 mRNA and protein expression, in SW620 and HCT-116 cells. miR-25 directly targeted ANGPTL2 by binding to its 3'‑UTR, as determined by the dual luciferase reporter assay. To the best of our know-ledge, the results of this study suggest for the first time that the abnormal upregulation of ANGPTL2 in CRC is associated with miR-25 downregulation. Additionally, miR-25‑mediated ANGPTL2 promoted the malignant progression of CRC. The present study provides evidence supporting ANGPTL2 and miR-25 as diagnostic or therapeutic targets for CRC.

A genetically engineered mouse model developing rapid progressive pancreatic ductal adenocarcinoma

The premalignant lesions of pancreatic cancer, pancreatic intraepithelial neoplasia (PanIN), have a high frequency of mutations in Kirsten rat sarcoma viral oncogene homologue (KRAS), and genetic alterations in the retinoblastoma (Rb)-E2 factor (E2F) and transformed 3T3 cell double minute 2 (MDM2)-p53 pathways accelerate development of pancreatic ductal adenocarcinoma. The viral oncoprotein SV40 large T antigen (TAg) can inhibit the effects of the Rb family of molecules and of p53 on these pathways, and targeted expression of TAg in mouse pancreas is associated with the development of endocrine or acinar cell tumours. In this study, to determine whether the viral oncoprotein promotes pancreatic duct carcinogenesis initiated by oncogenic KRAS, we generated mice expressing temperature-sensitive SV40 large T antigen (tsTAg) on pancreatic epithelial cells in the presence or absence of Kras(G12D) . Mice with pancreas-specific tsTAg expression developed acinar cell dysplasia by 22 weeks without PanIN formation, while mice expressing both tsTAg and Kras(G12D) developed highly aggressive adenocarcinoma with a ductal cell phenotype within a short period, and died within 3 weeks. The tumours resembled human pancreatic ductal adenocarcinoma (PDAC) at the histological level, and oncogenic Kras and tsTAg synergistically activated E2f and Sre transcription in established PDAC cell lines. These results suggest that tsTAg synergistically promotes Kras(G12D) -associated PDAC formation, and our study identifies a new mouse model of PDAC that may allow a better understanding of the mechanism of carcinogenesis in pancreatic carcinoma, which shows a catastrophic clinical course.

Rottlerin suppresses growth of human pancreatic tumors in nude mice, and pancreatic cancer cells isolated from Kras(G12D) mice

The purpose of the study was to examine the molecular mechanisms by which rottlerin inhibited growth of human pancreatic tumors in Balb C nude mice, and pancreatic cancer cells isolated from Kras(G12D) mice. AsPC-1 cells were injected subcutaneously into Balb c nude mice, and tumor-bearing mice were treated with rottlerin. Cell proliferation and apoptosis were measured by Ki67 and TUNEL staining, respectively. The expression of components of Akt, Notch, and Sonic Hedgehog (Shh) pathways were measured by the immunohistochemistry, Western blot analysis, and/or q-RT-PCR. The effects of rottlerin on pancreatic cancer cells isolated from Kras(G12D) mice were also examined. Rottlerin-treated mice showed a significant inhibition in tumor growth which was associated with suppression of cell proliferation, activation of capase-3 and cleavage of PARP. Rottlerin inhibited the expression of Bcl-2, cyclin D1, CDK2 and CDK6, and induced the expression of Bax in tumor tissues compared to untreated control. Rottlerin inhibited the markers of angiogenesis (Cox-2, VEGF, VEGFR, and IL-8), and metastasis (MMP-2 and MMP-9), thus blocking production of tumorigenic mediators in tumor microenvironment. Rottlerin also inhibited epithelial-mesenchymal transition by up-regulating E-cadherin and inhibiting the expression of Slug and Snail. Furthermore, rottlerin treatment of xenografted tumors or pancreatic cancer cells isolated from Kras(G12D) mice showed a significant inhibition in Akt, Shh and Notch pathways compared to control groups. These data suggest that rottlerin can inhibit pancreatic cancer growth by suppressing multiple signaling pathways which are constitutively active in pancreatic cancer. Taken together, our data show that the rottlerin induces apoptosis and inhibits pancreatic cancer growth by targeting Akt, Notch and Shh signaling pathways, and provide a new therapeutic approach with translational potential for humans.

Biomarkers as predictors of recurrence following curative resection for pancreatic ductal adenocarcinoma: a review

Pancreatic ductal adenocarcinoma (PDA) is the fourth most common cancer causing death in the United States. Early tumor recurrence is an important contributor to the dismal prognosis. The availability of an accurate prognostic biomarker for predicting disease recurrence following curative resection will be beneficial for patient care. Most of the currently studied biomarkers remain in the investigational phase, with CA 19-9 being the only biomarker currently approved by the FDA. Herein, we review the utility of CA 19-9 and other investigational cellular, gene, and molecular tumor markers for predicting PDA recurrence following curative surgical resection.

Yap1 activation enables bypass of oncogenic Kras addiction in pancreatic cancer

Activating mutations in KRAS are among the most frequent events in diverse human carcinomas and are particularly prominent in human pancreatic ductal adenocarcinoma (PDAC). An inducible Kras(G12D)-driven mouse model of PDAC has established a critical role for sustained Kras(G12D) expression in tumor maintenance, providing a model to determine the potential for and the underlying mechanisms of Kras(G12D)-independent PDAC recurrence. Here, we show that some tumors undergo spontaneous relapse and are devoid of Kras(G12D) expression and downstream canonical MAPK signaling and instead acquire amplification and overexpression of the transcriptional coactivator Yap1. Functional studies established the role of Yap1 and the transcriptional factor Tead2 in driving Kras(G12D)-independent tumor maintenance. The Yap1/Tead2 complex acts cooperatively with E2F transcription factors to activate a cell cycle and DNA replication program. Our studies, along with corroborating evidence from human PDAC models, portend a novel mechanism of escape from oncogenic Kras addiction in PDAC.

Genetic inactivation of Nupr1 acts as a dominant suppressor event in a two-hit model of pancreatic carcinogenesis

BACKGROUND

Nuclear protein 1 (Nupr1) is a major factor in the cell stress response required for Kras(G12D)-driven formation of pancreatic intraepithelial neoplastic lesions (PanINs). We evaluated the relevance of Nupr1 in the development of pancreatic cancer.

METHODS

We investigated the role of Nupr1 in pancreatic ductal adenocarcinoma (PDAC) progression beyond PanINs in Pdx1-cre;LSL-Kras(G12D);Ink4a/Arf(fl/fl)(KIC) mice.

RESULTS

Even in the context of the second tumorigenic hit of Ink4a/Arf deletion, Nupr1 deficiency led to suppression of malignant transformation involving caspase 3 activation in premalignant cells of KIC pancreas. Only half of Nupr1-deficient;KIC mice achieved PDAC development, and incident cases survived longer than Nupr1(wt);KIC mice. This was associated with the development of well-differentiated PDACs in Nupr1-deficient;KIC mice, which displayed enrichment of genes characteristic of the recently identified human classical PDAC subtype. Nupr1-deficient;KIC PDACs also shared with human classical PDACs the overexpression of the Kras-activation gene signature. In contrast, Nupr1(wt);KIC mice developed invasive PDACs with enriched gene signature of human quasi-mesenchymal (QM) PDACs. Cells derived from Nupr1-deficient;KIC PDACs growth in an anchorage-independent manner in vitro had higher aldehyde dehydrogenase activity and overexpressed nanog, Oct-4 and Sox2 transcripts compared with Nupr1(wt);KIC cells. Moreover, Nupr1-deficient and Nurpr1(wt);KIC cells differed in their sensitivity to the nucleoside analogues Ly101-4b and WJQ63. Together, these findings show the pivotal role of Nupr1 in both the initiation and late stages of PDAC in vivo, with a potential impact on PDAC cell stemness.

CONCLUSIONS

According to Nupr1 status, KIC mice develop tumours that phenocopy human classical or QM-PDAC, respectively, and present differential drug sensitivity, thus becoming attractive models for preclinical drug trials.

Pancreatic intraepithelial neoplasia in the background of invasive ductal carcinoma of the pancreas as a prognostic factor

AIMS

Of the recognized precursor lesions of pancreatic adenocarcinoma, pancreatic intraepithelial neoplasia (PanIN) is the most common form. However, little is known about the relationship between the grade of PanIN and prognosis for patients with invasive ductal carcinoma.

METHODS AND RESULTS

In 124 patients with invasive ductal carcinoma, we examined the grade and number of PanIN lesions in all slides of resected pancreas. The prevalence rates of PanIN-1A, PanIN-1B, PanIN-2 and PanIN-3 were 86%, 84%, 57% and 30%, respectively. We allocated PanIN-2 and PanIN-3 cases into a PanIN-high group, and cases showing PanIN-1A, PanIN-1B or absence of PanIN into a PanIN-low group. In clinicopathological analysis, PanIN-high status was significantly correlated with the number of PanIN lesions (P < 0.0001). Disease-free and overall survival were statistically better in the PanIN-high group than in the PanIN-low group (P = 0.0005 and P = 0.0003). Univariate and multivariate analyses revealed that tumour size and PanIN-low status were statistically significant factors for a poorer prognosis (P = 0.042 and P = 0.007).

CONCLUSIONS

In a pathological examination, it is important to evaluate the grade and number of PanINs in assessing the prognosis of pancreatic cancer.

Embelin suppresses growth of human pancreatic cancer xenografts, and pancreatic cancer cells isolated from KrasG12D mice by inhibiting Akt and Sonic hedgehog pathways

Pancreatic cancer is a deadly disease, and therefore effective treatment and/or prevention strategies are urgently needed. The objectives of this study were to examine the molecular mechanisms by which embelin inhibited human pancreatic cancer cell growth in vitro, and xenografts in Balb C nude mice, and pancreatic cancer cell growth isolated from Kras^G12D transgenic mice. XTT assays were performed to measure cell viability. AsPC-1 cells were injected subcutaneously into Balb c nude mice and treated with embelin. Cell proliferation and apoptosis were measured by Ki67 and TUNEL staining, respectively. The expression of Akt, and Sonic Hedgehog (Shh) and their target gene products were measured by the immunohistochemistry, and Western blot analysis. The effects of embelin on pancreatic cancer cells isolated from 10-months old Kras^G12D mice were also examined. Embelin inhibited cell viability in pancreatic cancer AsPC-1, PANC-1, MIA PaCa-2 and Hs 766T cell lines, and these inhibitory effects were blocked either by constitutively active Akt or Shh protein. Embelin-treated mice showed significant inhibition in tumor growth which was associated with reduced expression of markers of cell proliferation (Ki67, PCNA and Bcl-2) and cell cycle (cyclin D1, CDK2, and CDK6), and induction of apoptosis (activation of caspase-3 and cleavage of PARP, and increased expression of Bax). In addition, embelin inhibited the expression of markers of angiogenesis (COX-2, VEGF, VEGFR, and IL-8), and metastasis (MMP-2 and MMP-9) in tumor tissues. Antitumor activity of embelin was associated with inhibition of Akt and Shh pathways in xenografts, and pancreatic cancer cells isolated from Kras^G12D mice. Furthermore, embelin also inhibited epithelial-to-mesenchymal transition (EMT) by up-regulating E-cadherin and inhibiting the expression of Snail, Slug, and ZEB1. These data suggest that embelin can inhibit pancreatic cancer growth, angiogenesis and metastasis by suppressing Akt and Shh pathways, and can be developed for the treatment and/or prevention of pancreatic cancer.

A modular and flexible ESC-based mouse model of pancreatic cancer

Saborowski et al. developed a flexible embryonic stem cell (ESC)-based mouse model for pancreatic cancer. The ESCs harbor a latent Kras mutant, a homing cassette, and other genetic elements needed for rapid insertion and conditional expression of tetracycline-controlled transgenes, including fluorescence-coupled shRNAs. This model produces a disease that follows the progression of human pancreatic cancer, and they used it to dissect temporal roles for Pten and c-Myc in pancreatic cancer development and maintenance.

Genetically engineered mouse models (GEMMs) have greatly expanded our knowledge of pancreatic ductal adenocarcinoma (PDAC) and serve as a critical tool to identify and evaluate new treatment strategies. However, the cost and time required to generate conventional pancreatic cancer GEMMs limits their use for investigating novel genetic interactions in tumor development and maintenance. To address this problem, we developed flexible embryonic stem cell (ESC)-based GEMMs that facilitate the rapid generation of genetically defined multiallelic chimeric mice without further strain intercrossing. The ESCs harbor a latent Kras mutant (a nearly ubiquitous feature of pancreatic cancer), a homing cassette, and other genetic elements needed for rapid insertion and conditional expression of tetracycline-controlled transgenes, including fluorescence-coupled shRNAs capable of efficiently silencing gene function by RNAi. This system produces a disease that recapitulates the progression of pancreatic cancer in human patients and enables the study and visualization of the impact of gene perturbation at any stage of pancreas cancer progression. We describe the use of this approach to dissect temporal roles for the tumor suppressor Pten and the oncogene c-Myc in pancreatic cancer development and maintenance.

PTEN loss and KRAS activation leads to the formation of serrated adenomas and metastatic carcinoma in the mouse intestine

Mutation or loss of the genes PTEN and KRAS have been implicated in human colorectal cancer (CRC), and have been shown to co-occur despite both playing a role in the PI3' kinase (PI3'K) pathway. We investigated the role of these genes in intestinal tumour progression in vivo, using genetically engineered mouse models, with the aim of generating more representative models of human CRC. Intestinal-specific deletion of Pten and activation of an oncogenic allele of Kras was induced in wild-type (WT) mice and mice with a predisposition to adenoma development (Apc(fl/+) ). The animals were euthanized when they became symptomatic of a high tumour burden. Histopathological examination of the tissues was carried out, and immunohistochemistry used to characterize signalling pathway activation. Mutation of Pten and Kras resulted in a significant life-span reduction of mice predisposed to adenomas. Invasive adenocarcinoma was observed in these animals, with evidence of activation of the PI3'K pathway but no metastasis. However, mutation of Pten and Kras in WT animals not predisposed to adenomas led to perturbed homeostasis of the intestinal epithelium and the development of hyperplastic polyps, dysplastic sessile serrated adenomas and metastasizing adenocarcinomas with serrated features. These studies demonstrate synergism between Pten and Kras mutations in intestinal tumour progression, in an autochthonous and immunocompetent murine model, with potential application to preclinical drug testing. In particular, they show that Pten and Kras mutations alone predispose mice to the spectrum of serrated lesions that reflect the serrated pathway of CRC progression in humans.

ERKs in cancer: friends or foes?

The extracellular signal-regulated kinase ERK1 and ERK2 (ERK1/2) cascade regulates a variety of cellular processes by phosphorylating multiple target proteins. The outcome of its activation ranges from stimulation of cell survival and proliferation to triggering tumor suppressor responses such as cell differentiation, cell senescence, and apoptosis. This pathway is intimately linked to cancer as several of its upstream activators are frequently mutated in human disease and are shown to accelerate tumorigenesis when engineered in the mouse genome. However, measurement of activated ERKs in human cancers or mouse models does not always support a role in tumorigenesis, and data consistent with a role in tumor suppression have been reported as well. The intensity of ERK signaling, negative feedback loops that regulate the pathway, and cross-talks with other signaling pathways, seem to be of primary importance in determining the final cellular outcome. Cell senescence, a putative tumor-suppression mechanism, depends on high-intensity ERK signals that trigger phosphorylation-dependent protein degradation of multiple proteins required for cell-cycle progression. This response may be circumvented during carcinogenesis by a variety of mechanisms, some of them yet to be discovered, which in essence turn ERK functions from tumor suppression to tumor promotion. The use of pharmacologic inhibitors targeting this pathway must be carefully evaluated so they are applied to cases in which ERKs are mainly oncogenic.

The challenge of pancreatic cancer therapy and novel treatment strategy using engineered mesenchymal stem cells

Mesenchymal stem cells (MSCs) have attracted significant attention in cancer research as a result of their accessibility, tumor-oriented homing capacity, and the feasibility of auto-transplantation. This review provides a comprehensive overview of current challenges in pancreatic cancer therapy, and we propose a novel strategy for using MSCs as means of delivering anticancer genes to the site of pancreas. We aim to provide a practical platform for the development of MSC-based therapy for pancreatic cancer.

The roles of FOXM1 in pancreatic stem cells and carcinogenesis

Pancreatic ductal adenocarcinoma (PDAC) has one of the poorest prognoses among all cancers. Over the past several decades, investigators have made great advances in the research of PDAC pathogenesis. Importantly, identification of pancreatic cancer stem cells (PCSCs) in pancreatic cancer cases has increased our understanding of PDAC biology and therapy. PCSCs are responsible for pancreatic tumorigenesis and tumor progression via a number of mechanisms, including extensive proliferation, self-renewal, high tumorigenic ability, high propensity for invasiveness and metastasis, and resistance to conventional treatment. Furthermore, emerging evidence suggests that PCSCs are involved in the malignant transformation of pancreatic intraepithelial neoplasia. The molecular mechanisms that control PCSCs are related to alterations of various signaling pathways, for instance, Hedgehog, Notch, Wnt, B-cell-specific Moloney murine leukemia virus insertion site 1, phosphoinositide 3-kinase/AKT, and Nodal/Activin. Also, authors have reported that the proliferation-specific transcriptional factor Forkhead box protein M1 is involved in PCSC self-renewal and proliferation. In this review, we describe the current knowledge about the signaling pathways related to PCSCs and the early stages of PDAC development, highlighting the pivotal roles of Forkhead box protein M1 in PCSCs and their impacts on the development and progression of pancreatic intraepithelial neoplasia.

Loss of PTEN expression is associated with poor prognosis in patients with intraductal papillary mucinous neoplasms of the pancreas

PURPOSE

Previously, we reported PIK3CA gene mutations in high-grade intraductal papillary mucinous neoplasms (IPMN). However, the contribution of phosphatidylinositol-3 kinase pathway (PI3K) dysregulation to pancreatic carcinogenesis is not fully understood and its prognostic value unknown. We investigated the dysregulation of the PI3K signaling pathway in IPMN and its clinical implication.

EXPERIMENTAL DESIGN

Thirty-six IPMN specimens were examined by novel mutant-enriched sequencing methods for hot-spot mutations in the PIK3CA and AKT1 genes. PIK3CA and AKT1 gene amplifications and loss of heterozygosity at the PTEN locus were also evaluated. In addition, the expression levels of PDPK1/PDK1, PTEN, and Ki67 were analyzed by immunohistochemistry.

RESULTS

Three cases carrying the E17K mutation in the AKT1 gene and one case harboring the H1047R mutation in the PIK3CA gene were detected among the 36 cases. PDK1 was significantly overexpressed in the high-grade IPMN versus low-grade IPMN (P = 0.034) and in pancreatic and intestinal-type of IPMN versus gastric-type of IPMN (P = 0.020). Loss of PTEN expression was strongly associated with presence of invasive carcinoma and poor survival in these IPMN patients (P = 0.014).

CONCLUSION

This is the first report of AKT1 mutations in IPMN. Our data indicate that oncogenic activation of the PI3K pathway can contribute to the progression of IPMN, in particular loss of PTEN expression. This finding suggests the potential employment of PI3K pathway-targeted therapies for IPMN patients. The incorporation of PTEN expression status in making surgical decisions may also benefit IPMN patients and should warrant further investigation.