Frequency of K-ras mutations in pancreatic intraductal neoplasias associated with pancreatic ductal adenocarcinoma and chronic pancreatitis: a meta-analysis

MicroRNA-506 is up-regulated in the development of pancreatic ductal adenocarcinoma and is associated with attenuated disease progression

BACKGROUND

MicroRNA-506 (miR-506) has been reported to function in several tumors as a tumor suppressor gene or oncogene. However, the expression and role of miR-506 in pancreatic ductal adenocarcinoma (PDAC) remains unclear. In this study, we aimed to evaluate the phenotype of miR-506 in PDAC.

METHODS

Using miRNA in situ hybridization, we examined the expression of miR-506 in 113 PDACs and 87 paired normal pancreatic tissues. We evaluated miR-506 expression in PDAC cells, normal pancreatic ducts, and acinus/islands, and we analyzed the associations between miR-506 expression and the clinicopathologic characteristics of PDAC patients.

RESULTS

miR-506 expression was higher in PDAC than in matched normal pancreatic ductal cells (P < 0.001). On the other hand, the combined group of well and moderately differentiated PDACs showed higher levels of miR-506 than the poorly differentiated ones (P = 0.023). Moreover, miR-506 expression was negatively associated with pathologic T category (P = 0.004) and lymph node metastasis (P = 0.033), suggesting that miR-506 might inhibit the progression of PDAC.

CONCLUSIONS

Our results suggest that miR-506 either plays a role as an oncogene in the tumorigenesis and a tumor suppressor in the progression or serves as a house-keeping, tumor-suppressing miRNA, whose expression can be activated by oncogenic signals in early development to hinder the progression of PDAC.

KRAS Engages AGO2 to Enhance Cellular Transformation

Oncogenic mutations in RAS provide a compelling yet intractable therapeutic target. Using co-immunoprecipitation mass spectrometry, we uncovered an interaction between RAS and Argonaute 2 (AGO2). Endogenously, RAS and AGO2 co-sediment and co-localize in the endoplasmic reticulum. The AGO2 N-terminal domain directly binds the Switch II region of KRAS, agnostic of nucleotide (GDP/GTP) binding. Functionally, AGO2 knockdown attenuates cell proliferation in mutant KRAS-dependent cells and AGO2 overexpression enhances KRAS(G12V)-mediated transformation. Using AGO2-/- cells, we demonstrate that the RAS-AGO2 interaction is required for maximal mutant KRAS expression and cellular transformation. Mechanistically, oncogenic KRAS attenuates AGO2-mediated gene silencing. Overall, the functional interaction with AGO2 extends KRAS function beyond its canonical role in signaling.

Molecular Biomarkers of Pancreatic Intraepithelial Neoplasia and Their Implications in Early Diagnosis and Therapeutic Intervention of Pancreatic Cancer

Lack of early detection and effective interventions is a major reason for the poor prognosis and dismal survival rates for pancreatic cancer. Pancreatic intraepithelial neoplasia (PanIN) is the most common precursor of invasive pancreatic ductal adenocarcinoma (PDAC). Each stage in the progression from PanIN to PDAC is well characterized by multiple significant genetic alterations affecting signaling pathways. Understanding the biological behavior and molecular alterations in the progression from PanIN to PDAC is crucial to the identification of noninvasive biomarkers for early detection and diagnosis and the development of preventive and therapeutic strategies for control of pancreatic cancer progression. This review focuses on molecular biomarkers of PanIN and their important roles in early detection and treatment of pancreatic cancer.

Pancreatic cancer: Current research and future directions

Despite the survival rate advancements in different types of cancer in the last 40 years, the perspective for pancreatic cancer patients has seen no substantial changes. Indeed, the five year survival rate remains around 5%. Nevertheless, in the last decade we have witnessed an increased interest in pancreatic cancer biology and this has produced a substantial increment in our knowledge on pancreatic cancer progression. The big challenge is now to translate this knowledge in better outcomes for patients. The aim of this review is to describe the latest discoveries and advancements in pancreatic cancer research and to discuss future directions.

Intraductal Papillary Mucinous Neoplasm and Pancreas Divisum: Two Cases

Background: Pancreatic intraductal papillary mucinous neoplasms (IPMNs) are a subset of ductal cell tumors with potential for malignancy. Because it is difficult to predict whether and when they will become malignant, management and resection are widely debated.

Case 1: A 70-year-old male with a 1-year history of epigastric pain was found to have pancreas divisum with a dominant 2.4 cm multicystic uncinate process lesion communicating with the main pancreatic duct and associated uncinate duct dilation.

Case 2: An 83-year-old male with pancreas divisum had a 7.3 cm uncinate cystic lesion with mural nodularity that had increased in size from 2.1 cm in 2008.

Conclusion: Management of patients with IPMNs can be challenging and may require resection to prevent malignant transformation.

Pathobiology of pancreatic cancer: implications on therapy

Although the concept of tumor heterogeneity was established several decades ago, the interest in this topic is still unbroken. With the identification of inter- and intratumoral genomic rearrangements and the detection of cancer stem cells (CSCs) through phenotypic variations of cancer cells there are increasing options for pancreatic cancer therapy. Indeed, some pre-clinical studies have shown promising results in the treatment of drug-resistant CSCs, whereby a few strategies were already tested in clinical trials. Basically, CSCs are influenced by the tumor microenvironment and an epigenetic reprogramming to gain stem cell-like characteristics. Targeting options inhibiting the epithelial-mesenchymal crosstalk or promoting epigenetic-driven differentiation of CSCs to a less aggressive phenotype raised the possibilities of further therapeutic applications, which will be discussed in this review.

Inhibition of mutant KrasG12D-initiated murine pancreatic carcinoma growth by a dual c-Raf and soluble epoxide hydrolase inhibitor t-CUPM

Mutant Kras and chronic pancreatitis are the most common pathological events involved in human pancreatic cancer. It has been demonstrated that c-Raf is responsible for transmitting signals from mutant Ras to its downstream signals including MEK-ERK and for initiating carcinogenesis. The soluble epoxide hydrolase (sEH), a pro-inflammatory enzyme, generally inactivates anti-inflammatory and anti-pain epoxyeicosatrienoic acids (EETs). Herein, we have synthesized a novel compound of trans-4-{4-[3-(4-chloro-3-trifluoromethyl-phenyl)-ureido]-cyclohexyloxy}-pyridine-2-carboxylic acid methylamide (t-CUPM) via modifying the central phenyl ring of sorafenib and confirmed its dual inhibition of sEH and c-Raf by recombinant kinase activity assay. Pharmacokinetic analysis revealed that oral dosing of t-CUPM resulted in higher blood levels than that of sorafenib throughout the complete time course (48 h). The effect of t-CUPM on the inhibition of mutant Kras(G12D)-initiated murine pancreatic cancer cell growth was determined using the mouse pancreatic carcinoma cell model obtained from LSL-Kras(G12D)/Pdx1-Cre mice and showed that t-CUPM significantly inhibited this murine pancreatic carcinoma cell growth both in vitro and in mice in vivo. Inhibition of mutant Kras-transmitted phosphorylations of cRAF/MEK/ERK was demonstrated in these pancreatic cancer cells using Western blot assay and immunohistochemical approach. Modulation of oxylipin profile, particularly increased EETs/DHET ratio by sEH inhibition, was observed in mice treated with t-CUPM. These results indicate that t-CUPM is a highly potential agent to treat pancreatic cancer via simultaneously targeting c-Raf and sEH.

Targeting the Janus-activated kinase-2-STAT3 signalling pathway in pancreatic cancer using the HSP90 inhibitor ganetespib

BACKGROUND

Pancreatic cancer (PC) is an aggressive malignancy characterised by chemoresistance. HSP90 is important for stabilisation of proteins, cell signalling and malignant growth. We hypothesised that ganetespib, an HSP90 inhibitor, can inhibit PC cell growth by interfering with multiple signalling cascades, including the Janus-activated kinase (JAK)-STAT pathway, and act synergistically with chemotherapeutic drugs.

METHODS

The effects of ganetespib were evaluated in ASPC-1, HPAC, MIA PaCA-2 and PANC-1 cell lines using a cell proliferation assay. Effects on the expression of phosphoinositide 3-kinase (PI3K)/AKT, mitogen-activated protein kinase (MAPK) and JAK-STAT pathways were examined by Western blot. JAK2 and STAT3 were knocked down by transient transfection with JAK2 or STAT3 small interfering RNA. ASPC-1 and HPAC cell lines were tested for sensitivity to ganetespib, 5-fluorouracil/oxaliplatin, and gemcitabine/paclitaxel, alone and in combination, using an in vivo tumour xenograft model.

RESULTS

Ganetespib significantly decreased cell proliferation in all tested PC cell lines. Ganetespib decreased the activation of extracellular signal-related kinase (ERK), PI3K/AKT, and c-Jun NH2-terminal kinase (JNK) signalling molecules and diminished the activation of STAT3 in an additive manner with isolated downregulation of JAK2 expression. In animal models, ganetespib potentiated the effects of 5-fluouracil/oxaliplatin and gemcitabine/paclitaxel, as measured by tumour volume. Western blot analysis from tumours removed from animals confirmed the effects of ganetespib on PI3K/AKT, ERK and JNK pathways.

CONCLUSIONS

Ganetespib inhibits the growth of PC cells, an effect associated with downregulation of signalling through the JAK2-STAT3, PI3K/AKT and MAPK pathways. This provides preclinical proof-of-principle that ganetespib enhances the activity of chemotherapeutic agents and warrants further evaluation in PC clinical trials.

A Revised Classification System and Recommendations From the Baltimore Consensus Meeting for Neoplastic Precursor Lesions in the Pancreas

International experts met to discuss recent advances and to revise the 2004 recommendations for assessing and reporting precursor lesions to invasive carcinomas of the pancreas, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), mucinous cystic neoplasm, and other lesions. Consensus recommendations include the following: (1) To improve concordance and to align with practical consequences, a 2-tiered system (low vs. high grade) is proposed for all precursor lesions, with the provision that the current PanIN-2 and neoplasms with intermediate-grade dysplasia now be categorized as low grade. Thus, "high-grade dysplasia" is to be reserved for only the uppermost end of the spectrum ("carcinoma in situ"-type lesions). (2) Current data indicate that PanIN of any grade at a margin of a resected pancreas with invasive carcinoma does not have prognostic implications; the clinical significance of dysplasia at a margin in a resected pancreas with IPMN lacking invasive carcinoma remains to be determined. (3) Intraductal lesions 0.5 to 1 cm can be either large PanINs or small IPMNs. The term "incipient IPMN" should be reserved for lesions in this size with intestinal or oncocytic papillae or GNAS mutations. (4) Measurement of the distance between an IPMN and invasive carcinoma and sampling of intervening tissue are recommended to assess concomitant versus associated status. Conceptually, concomitant invasive carcinoma (in contrast with the "associated" group) ought to be genetically distinct from an IPMN elsewhere in the gland. (5) "Intraductal spread of invasive carcinoma" (aka, "colonization") is recommended to describe lesions of invasive carcinoma invading back into and extending along the ductal system, which may morphologically mimic high-grade PanIN or even IPMN. (6) "Simple mucinous cyst" is recommended to describe cysts >1 cm having gastric-type flat mucinous lining at most minimal atypia without ovarian-type stroma to distinguish them from IPMN. (7) Human lesions resembling the acinar to ductal metaplasia and atypical flat lesions of genetically engineered mouse models exist and may reflect an alternate pathway of carcinogenesis; however, their biological significance requires further study. These revised recommendations are expected to improve our management and understanding of precursor lesions in the pancreas.

A case of MUC5AC-positive intraductal neoplasm of the pancreas classified as an intraductal tubulopapillary neoplasm?

This report describes a unique case of intraductal tubulopapillary neoplasm (ITPN) of the pancreas in order to clarify its oncogenesis and more precisely classify pancreatic intraductal neoplasms. A 74-year-old man visited our institution for follow-up of acute pancreatitis. Imaging examinations revealed a hypovascular intraductal mass in the head of the pancreas with progressive dilation of the pancreatic duct, atrophy of the pancreatic parenchyma, and a non-mucinous appearance. A pancreatoduodenectomy was performed to identify this pancreatic intraductal neoplasm. Macroscopically, the tumor was a solid nodular mass with no visibly secreted mucin obstructing the dilated ducts. Histologically, it had a homogeneous appearance with nodules of back-to-back tubular glands and occasional papillary elements, and there were no apparent transitions to areas with less marked cytoarchitectural atypia. Although the intraductal neoplastic growth corresponded to an ITPN, immunohistochemical staining revealed partial positivity for MUC5AC, for which ITPNs are characteristically negative. Somatic mutations in KRAS, GNAS, BRAF, and PIK3CA were not detected. A loss of MUC5AC expression and mutations in KRAS and GNAS are key elements in the diagnosis of ITPN. Thus, it was difficult to distinguish the present case as a pancreatobiliary-type (PB-type) intraductal papillary mucinous neoplasm (IPMN) or a phenotypic variant of ITPN. As it is possible that some cases of PB-type IPMN and ITPN overlap, the precise classification of these rare lesions may require re-evaluation.

Preventive effects of fermented brown rice and rice bran against N-nitrosobis (2-oxopropyl) amine-induced pancreatic tumorigenesis in male hamsters

Fermented brown rice by Aspergillus oryzae (FBRA) is known to have the potential to prevent chemical carcinogenesis of the colon, liver, esophagus, urinary bladder, stomach and lungs in rodents. The present study examined the possible chemopreventive effects of FBRA on N-nitrosobis(2-oxopropyl)amine (BOP)-induced pancreatic tumorigenesis in hamsters. Five-week-old male Syrian golden hamsters were divided into seven groups. Groups 1–5 were subcutaneously injected with BOP (10 mg/kg body weight) four times during week 6 to induce pancreatic tumors, while groups 6 and 7 were injected with saline. Groups 2 and 3 were fed diets containing 5 and 10% FBRA, respectively, during the initiation phase. By contrast, groups 4 and 5 were fed diets containing 5 and 10% FBRA, respectively, during the post-initiation phase. Group 6 received a diet containing 10% FBRA throughout the experiment, and group 7 was kept on the basal diet alone and served as the untreated control. At the termination of the study (week 22), oral intake of 10% FBRA (group 5) during the post-initiation phase was identified to have significantly reduced the multiplicity (number of lesions/animal) of ductal adenocarcinoma [pancreatic intraepithelial neoplasia 3 (PanIN3); carcinoma in situ and invasive carcinoma] in comparison with group 1 control hamsters (0.24±0.44 vs. 0.71±0.72; P<0.05). Treatment with 10% FBRA in the post-initiation phase inhibited the progression of normal/precancerous lesions (PanIN1, mild hyperplastic lesions; and PanIN2, papillary hyperplasia) to ductal adenocarcinomas. Furthermore, dietary exposure to 10% FBRA during the initiation (group 3) and post-initiation phases (group 5) significantly reduced the multiplicity of PanIN2 (group 3, 0.55±0.69; group 5, 0.45±0.69; versus group 1, 1.26±1.24; P<0.05 and P<0.01, respectively). A significant reduction of Ki-67 positivity of PanIN2 in group 5 was also confirmed (group 5, 0.05±0.03; group 1, 0.22±0.12; P<0.01). Using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, augmentation of apoptosis by FBRA exposure in the non-lesional ductal epithelium and proliferative lesions was not evident. These findings indicate that FBRA exhibits inhibitory effects on BOP-induced pancreatic tumorigenesis in hamsters due to the reduced proliferation rate of tumor cells. Thus, FBRA may be a promising chemopreventive agent in human pancreatic cancer.

Genomic alterations in pancreatic cancer and their relevance to therapy

Pancreatic cancer is a highly lethal cancer type, for which there are few viable therapeutic options. But, with the advance of sequencing technologies for global genomic analysis, the landscape of genomic alterations in pancreatic cancer is becoming increasingly well understood. In this review, we summarize current knowledge of genomic alterations in 12 core signaling pathways or cellular processes in pancreatic ductal adenocarcinoma, which is the most common type of malignancy in the pancreas, including four commonly mutated genes and many other genes that are mutated at low frequencies. We also describe the potential implications of these genomic alterations for development of novel therapeutic approaches in the context of personalized medicine.

Mutational spectrum of intraepithelial neoplasia in pancreatic heterotopia

Heterotopic pancreatic parenchyma recapitulates the normal pancreas in extrapancreatic locations and, on rare occasions, can even give rise to pancreatic adenocarcinoma. The genetic signatures of pancreatic adenocarcinoma and its precursor lesions are well characterized. We explored the genetic alterations in precursor lesions (intraductal papillary mucinous neoplasms [IPMN], pancreatic intraepithelial neoplasia [PanIN]) in patients with pancreatic heterotopias but without concomitant pancreatic ductal adenocarcinomas. This allowed us to determine whether the stereotypical dysplasia--infiltrating carcinoma sequence also occurs in these extrapancreatic foci. Seven cases of heterotopic pancreas with ductal precursor lesions were identified. These included 2 IPMNs with focal high-grade dysplasia and 5 PanINs with low- to moderate-grade dysplasia (PanIN grades 1-2). Neoplastic epithelium was microdissected and genomic DNA was extracted. Sequencing of commonly mutated hotspots (KRAS, TP53, CDKN2A, SMAD4, BRAF, and GNAS) in pancreatic ductal adenocarcinoma and its precursor lesions was performed. Both IPMNs were found to have KRAS codon 12 mutations. The identification of KRAS mutations suggests a genetic pathway shared with IPMN of the pancreas. No mutations were identified in our heterotopic PanINs. One of the possible mechanisms for the development of dysplasia in these lesions is field effect. At the time of these resections, there was no clinical or pathologic evidence of a prior or concomitant pancreatic lesion. However, a clinically undetectable lesion is theoretically possible. Therefore, although a field effect cannot be excluded, there was no evidence for it in this study.

Variant Profiling of Candidate Genes in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis. Variant profiling is crucial for developing personalized treatment and elucidating the etiology of this disease.

METHODS

Patients with PDAC undergoing surgery from 2007 to 2012 (n = 73) were followed from diagnosis until death or the end of the study. We applied an anchored multiplex PCR (AMP)-based next-generation sequencing (NGS) method to a panel of 65 selected genes and assessed analytical performance by sequencing a quantitative multiplex DNA reference standard. In clinical PDAC samples, detection of low-level KRAS (Kirsten rat sarcoma viral oncogene homolog) mutations was validated by allele-specific PCR and digital PCR. We compared overall survival of patients according to KRAS mutation status by log-rank test and applied logistic regression to evaluate the association between smoking and tumor variant types.

RESULTS

The AMP-based NGS method could detect variants with allele frequencies as low as 1% given sufficient sequencing depth (>1500×). Low-frequency KRAS G12 mutations (allele frequency 1%-5%) were all confirmed by allele-specific PCR and digital PCR. The most prevalent genetic alterations were in KRAS (78% of patients), TP53 (tumor protein p53) (25%), and SMAD4 (SMAD family member 4) (8%). Overall survival in T3-stage PDAC patients differed among KRAS mutation subtypes (P = 0.019). Transversion variants were more common in ever-smokers than in never-smokers (odds ratio 5.7; 95% CI 1.2-27.8).

CONCLUSIONS

The AMP-based NGS method is applicable for profiling tumor variants. Using this approach, we demonstrated that in PDAC patients, KRAS mutant subtype G12V is associated with poorer survival, and that transversion variants are more common among smokers.

Pancreatic adenocarcinoma pathology: changing "landscape"

Pancreatic cancer is a devastating disease. At time of diagnosis the disease is usually advanced and only a minority of patients are eligible for surgical resection. The overall 5-year survival is 6%. However, survival of patients with early stage pancreatic cancer is significantly better. To improve the prognosis of patients with pancreatic cancer, it is essential to diagnose and treat pancreatic cancer in the earliest stage. Prevention of pancreatic cancer by treating noninvasive precursor lesions just before they invade tissues can potentially lead to even better outcomes. Pancreatic carcinogenesis results from a stepwise progression in which accumulating genetic alterations drive neoplastic progression in well-defined precursor lesions, ultimately giving rise to an invasive adenocarcinoma. A thorough understanding of the genetic changes that drive pancreatic carcinogenesis can lead to identification of biomarkers for early detection and targets for therapy. Recent next-generation sequencing (NGS) studies have shed new light on our understanding of the natural history of pancreatic cancer and the precursor lesions that give rise to these cancers. Importantly, there is a significant window of opportunity for early detection and treatment between the first genetic alteration in a cell in the pancreas and development of full-blown pancreatic cancer. The current views on the pathology and genetics of pancreatic carcinogenesis that evolved from studies of pancreatic cancer and its precursor lesions are discussed in this review.

Association between pancreatitis and subsequent risk of pancreatic cancer: a systematic review of epidemiological studies

This study aimed to summarize published epidemiological evidence for the relationship between pancreatitis and subsequent risk of pancreatic cancer (PC). We searched Medline and Embase for epidemiological studies published by February 5th, 2014 examining the risk of PC in pancreatitis patients using highly inclusive algorithms. Information about first author, year of publication, country of study, recruitment period, type of pancreatitis, study design, sample size, source of controls and attained age of subjects were extracted by two researchers and Stata 11.0 was used to perform the statistical analyses and examine publication bias. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated with the random effects model. A total of 17 articles documenting 3 cohort and 14 case-control studies containing 14,667 PC cases and 17,587 pancreatitis cases were included in this study. The pooled OR between pancreatitis and PC risk was 7.05 (95%CI: 6.42-7.75). However, the pooled ORs of case-control and cohort studies were 4.62 (95%CI: 4.08-5.22) and 16.3 (95%CI: 14.3-18.6) respectively. The risk of PC was the highest in patients with chronic pancreatitis (pooled OR=10.35; 95%CI: 9.13-11.75), followed by unspecified type of pancreatitis (pooled OR=6.41; 95%CI: 4.93-8.34), both acute and chronic pancreatitis (pooled OR=6.13; 95%CI: 5.00-7.52), and acute pancreatitis (pooled OR=2.12; 95%CI: 1.59-2.83). The pooled OR of PC in pancreatitis cases diagnosed within 1 year was the highest (pooled OR=23.3; 95%CI: 14.0-38.9); and the risk in subjects diagnosed with pancreatitis for no less than 2, 5 and 10 years were 3.03 (95%CI: 2.41-3.81), 2.82 (95%CI: 2.12-3.76) and 2.25 (95%CI: 1.59-3.19) respectively. Pancreatitis, especially chronic pancreatitis, was associated with a significantly increased risk of PC; and the risk decreased with increasing duration since diagnosis of pancreatitis.

Discriminating patients with early-stage pancreatic cancer or chronic pancreatitis using serum electrospray mass profiling

Blood tests are needed to aid in the early detection of pancreatic ductal adenocarcinoma (PDAC), and monitoring pancreatitis development into malignancy especially in high risk patients. This study exhibits efforts and progress toward developing such blood tests, using electrospray-mass spectrometry (MS) serum profiling to distinguish patients with early-stage PDAC or pancreatitis from each other and from controls. Identification of significant serum mass peak differences between these individuals was performed using t tests and "leave one out" cross validation. Serum mass peak distributions of control individuals were distinguished from those of patients with chronic pancreatitis or early-stage PDAC with P values <10(-15), and patients with chronic pancreatitis were distinguished from those of patients with early-stage PDAC with a P value <10(-12). Sera from 12 out of 12 patients with PDAC stages I, IIA and IIB were blindly validated from controls. Tandem MS/MS identified a cancer phenotype with elements of PDAC involved in early-stage PDAC/control discrimination. These studies indicate electrospray-MS mass profiling can detect serum changes in patients with pancreatitis or early-stage pancreatic cancer. Such technology has the potential to aid in early detection of pancreatic cancer, biomarker development, and in monitoring development of pancreatitis into PDAC.

Addressing the challenges of pancreatic cancer: future directions for improving outcomes

Pancreatic ductal adenocarcinoma (PDAC), which accounts for more than 90% of all pancreatic tumours, is a devastating malignancy with an extremely poor prognosis, as shown by a 1-year survival rate of around 18% for all stages of the disease. The low survival rates associated with PDAC primarily reflect the fact that tumours progress rapidly with few specific symptoms and are thus at an advanced stage at diagnosis in most patients. As a result, there is an urgent need to develop accurate markers of pre-invasive pancreatic neoplasms in order to facilitate prediction of cancer risk and to help diagnose the disease at an earlier stage. However, screening for early diagnosis of prostate cancer remains challenging and identifying a highly accurate, low-cost screening test for early PDAC for use in clinical practice remains an important unmet need. More effective therapies are also crucial in PDAC, since progress in identifying novel therapies has been hampered by the genetic complexity of the disease and treatment remains a major challenge. Presently, the greatest step towards improved treatment efficacy has been made in the field of palliative chemotherapy by introducing FOLFIRINOX (folinic acid, 5-fluorouracil, irinotecan and oxaliplatin) and gemcitabine/nab-paclitaxel. Strategies designed to raise the profile of PDAC in research and clinical practice are a further requirement in order to ensure the best treatment for patients. This article proposes a number of approaches that may help to accelerate progress in treating patients with PDAC, which, in turn, may be expected to improve the quality of life and survival for those suffering from this devastating disease.

Roles of Commensal Microbiota in Pancreas Homeostasis and Pancreatic Pathologies

The pancreas plays a central role in metabolism, allowing ingested food to be converted and used as fuel by the cells throughout the body. On the other hand, the pancreas may be affected by devastating diseases, such as pancreatitis, pancreatic adenocarcinoma (PAC), and diabetes mellitus (DM), which generally results in a wide metabolic imbalance. The causes for the development and progression of these diseases are still controversial; therefore it is essential to better understand the underlying mechanisms which compromise the pancreatic homeostasis. The interest in the study of the commensal microbiome increased extensively in recent years, when many discoveries have illustrated its central role in both human physiology and maintenance of homeostasis. Further understanding of the involvement of the microbiome during the development of pathological conditions is critical for the improvement of new diagnostic and therapeutic approaches. In the present review, we discuss recent findings on the behavior and functions played by the microbiota in major pancreatic diseases and provide further insights into its potential roles in the maintenance of pancreatic steady-state activities.

Demographics, epidemiology, and inheritance of pancreatic ductal adenocarcinoma

Pancreatic cancer (PC) will affect 48,960 persons in the United States and will result in 40,560 deaths in 2015, according to the American Cancer Society. On a global basis, at least 337,000 persons will be diagnosed with PC. The incidence of PC has increased slightly in the United States, though worldwide cases are likely to increase substantially due to the influence of cigarette smoking, rising obesity and type II diabetes. The development of PC is related to a state of chronic inflammation and insulin resistance. Well-established environmental and personal risk factors for PC include advancing age, cigarette smoking, second-hand tobacco smoke exposure, obesity, inherited familial cancer syndromes, Ashkenazi Jewish heritage, chronic pancreatitis, dietary factors, and diabetes. Other identified associations are human immunodeficiency virus infection, ABO blood group polymorphisms, hepatitis B virus, and Helicobacter pylori.

Screening for pancreatic cancer

Even with improved cancer care generally, the incidence and death rate is increasing for pancreatic cancer. Concern exists that a further increase in deaths caused by pancreatic cancer will be seen as other causes of death, such as heart disease and other cancers, decline. Critical exploration of screening high-risk patients as a tool to reduce deaths from pancreatic cancer should be considered. Technological advances and improved understanding of pancreatic cancer biology provides an opportunity to identify and test a panel of early detection biomarkers easily, accurately, and inexpensively measured in blood, urine, stool, or saliva samples. These biomarkers may have additional usefulness in staging, stratification for treatment, establishing prognosis, and assessing response to therapy in this disease. Screening may prove to be one of several strategies to improve outcomes in a disease that has otherwise been difficult to defeat.

Pancreatic fatty degeneration and fibrosis as predisposing factors for the development of pancreatic ductal adenocarcinoma

OBJECTIVES

Knowledge of risk factors for development of pancreatic ductal adenocarcinoma (PDAC) is limited. To clarify the background condition of the pancreas for the development of PDAC, we analyzed pancreatic histological changes in noncancerous lesion specimens after pancreatectomy in PDAC patients.

METHODS

Seventy-six patients with PDAC were enrolled in this study. The PDAC was in the pancreatic head in 37 patients, in the body in 31, and in the tail in 8. No patients had a history of clinical chronic pancreatitis. As controls, 98 patients without PDAC were enrolled. The following parameters were examined: fibrosis, fatty degeneration, and inflammatory cell infiltration. More than 5% of fatty degeneration in the specimen, more than 10% of fibrosis, and more than 5% of inflammatory cell infiltration were considered positive changes.

RESULTS

Pancreatectomy specimens showed a higher ratio of positive change in fibrosis (86% vs 42%), fatty degeneration (72% vs 44%), and inflammatory cell infiltration (14% vs 3%) than control samples. Multivariate analyses demonstrated that each histological change was a significant, independent determinant for PDAC.

CONCLUSIONS

Our study demonstrated that cryptogenic pancreatic inflammation with fatty changes represents an important predisposing factor for PDAC. Screening for subclinical chronic pancreatitis in healthy populations may enable the detection of PDAC at an early stage.

Complex role for the immune system in initiation and progression of pancreatic cancer

The immune system plays a complex role in the development and progression of pancreatic cancer. Inflammation can promote the formation of premalignant lesions and accelerate pancreatic cancer development. Conversely, pancreatic cancer is characterized by an immunosuppressive environment, which is thought to promote tumor progression and invasion. Here we review the current literature describing the role of the immune response in the progressive development of pancreatic cancer, with a focus on the mechanisms that drive recruitment and activation of immune cells at the tumor site, and our current understanding of the function of the immune cell types at the tumor. Recent clinical and preclinical data are reviewed, detailing the involvement of the immune response in pancreatitis and pancreatic cancer, including the role of specific cytokines and implications for disease outcome. Acute pancreatitis is characterized by a predominantly innate immune response, while chronic pancreatitis elicits an immune response that involves both innate and adaptive immune cells, and often results in profound systemic immune-suppression. Pancreatic adenocarcinoma is characterized by marked immune dysfunction driven by immunosuppressive cell types, tumor-promoting immune cells, and defective or absent inflammatory cells. Recent studies reveal that immune cells interact with cancer stem cells and tumor stromal cells, and these interactions have an impact on development and progression of pancreatic ductal adenocarcinoma (PDAC). Finally, current PDAC therapies are reviewed and the potential for harnessing the actions of the immune response to assist in targeting pancreatic cancer using immunotherapy is discussed.

Pancreatic cancer: advances in treatment

Pancreatic cancer is a leading cause of cancer mortality and the incidence of this disease is expected to continue increasing. While patients with pancreatic cancer have traditionally faced a dismal prognosis, over the past several years various advances in diagnosis and treatment have begun to positively impact this disease. Identification of effective combinations of existing chemotherapeutic agents, such as the FOLFIRINOX and the gemcitabine + nab-paclitaxel regimen, has improved survival for selected patients although concerns regarding their toxicity profiles remain. A better understanding of pancreatic carcinogenesis has identified several pre-malignant precursor lesions, such as pancreatic intraepithelial neoplasias, intraductal papillary mucinous neoplasms, and cystic neoplasms. Imaging technology has also evolved dramatically so as to allow early detection of these lesions and thereby facilitate earlier management. Surgery remains a cornerstone of treatment for patients with resectable pancreatic tumors, and advances in surgical technique have allowed patients to undergo resection with decreasing perioperative morbidity and mortality. Surgery has also become feasible in selected patients with borderline resectable tumors as a result of neoadjuvant therapy. Furthermore, pancreatectomy involving vascular reconstruction and pancreatectomy with minimally invasive techniques have demonstrated safety without significantly compromising oncologic outcomes. Lastly, a deeper understanding of molecular aberrations contributing to the development of pancreatic cancer shows promise for future development of more targeted and safe therapeutic agents.

Phase I/II clinical trial of encapsulated, cytochrome P450 expressing cells as local activators of cyclophosphamide to treat spontaneous canine tumours

Based upon promising preclinical studies, a clinical trial was performed in which encapsulated cells overexpressing cytochrome P450 enzyme isoform 2B1 were implanted around malignant mammary tumours arising spontaneously in dogs. The dogs were then given cyclophosphamide, one of the standard chemotherapeutic agents used for the treatment of mammary tumours. The dogs were assessed for a number of clinical parameters as well as for reduction in tumour size. The treatment was well tolerated with no evidence of adverse reactions or side effects being associated with the administration of the encapsulated cells. Reductions in tumour size of more than 50% were observed for 6 out of the 11 tumours analysed while 5 tumours showing minor responses, i.e. stable disease. In contrast, the tumours that received cyclophosphamide alone showed only stable disease. Taken together, this data suggests that encapsulated cytochrome P450 expressing cells combined with chemotherapy may be useful in the local treatment of a number of dog mammary tumours and support the performance of further clinical studies to evaluate this new treatment.

The complex landscape of pancreatic cancer metabolism

Pancreatic ductal adenocarcinomas (PDA) are extremely aggressive cancers and currently available therapies are only minimally effective in treating this disease. Tackling this devastating cancer has been a major challenge to the scientific and medical communities, in part due to its intense therapeutic resistance. One of the aspects of this tumor that contributes to its aggressive behavior is its altered cellular metabolism. Indeed, PDA cells seem to possess the ability to adapt their metabolism to the particular environment to which they are exposed, including utilizing diverse fuel sources depending on their availability. Moreover, PDA tumors are efficient at recycling various metabolic substrates through activation of different salvage pathways such as autophagy and macropinocytosis. Together, these diverse metabolic adaptations allow PDA cells to survive and thrive in harsh environments that may lack nutrients and oxygen. Not surprisingly, given its central role in the pathogenesis of this tumor, oncogenic Kras plays a critical role in much of the metabolic reprogramming seen in PDA. In this review, we discuss the metabolic landscape of PDA tumors, including the molecular underpinnings of the key regulatory nodes, and describe how such pathways can be exploited for future diagnostic and therapeutic approaches.

Molecular analysis of pancreatic acinar cell cystadenomas: Evidence of a non-neoplastic nature

The biology of pancreatic acinar cell cystadenomas has not been clearly defined. However, a non-neoplastic process, caused by a cell differentiation failure leading to a cystic transformation, has been discussed, as well as a benign neoplastic lesion. Pancreatic acinar cell cystadenomas usually consist of thin-walled unilocular or multilocular cysts, and mural nodules have been described in two cases of a recent series. In one of these nodules, chromosomal imbalances were detected, which provided preliminary evidence for a neoplastic process. The aim of the current study was to further characterize the lesions by molecular analyses. In four cases without mural nodules, the clonality was assessed by performing mutational analyses within the highly variable displacement-loop region of the mitochondrial DNA. As a result, no closer correlation was identified between different foci within the tumors than between the tumors and adjacent normal pancreatic acinar tissue, indicating polyclonality of these lesions. Further molecular analyses revealed no mutations of the β-catenin and K-ras genes. In addition, no immunohistochemical evidence was identified for mutations of Smad4 or p53. In conclusion, the results of the current study demonstrated that pancreatic acinar cell cystadenomas are non-neoplastic lesions, with the potential exception of those rare cases with mural nodules.

Downstream of mutant KRAS, the transcription regulator YAP is essential for neoplastic progression to pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor survival rates and frequently carries oncogenic KRAS mutation. However, KRAS has thus far not been a viable therapeutic target. We found that the abundance of YAP mRNA, which encodes Yes-associated protein (YAP), a protein regulated by the Hippo pathway during tissue development and homeostasis, was increased in human PDAC tissue compared with that in normal pancreatic epithelia. In genetically engineered Kras(G12D) and Kras(G12D):Trp53(R172H) mouse models, pancreas-specific deletion of Yap halted the progression of early neoplastic lesions to PDAC without affecting normal pancreatic development and endocrine function. Although Yap was dispensable for acinar to ductal metaplasia (ADM), an initial step in the progression to PDAC, Yap was critically required for the proliferation of mutant Kras or Kras:Trp53 neoplastic pancreatic ductal cells in culture and for their growth and progression to invasive PDAC in mice. Yap functioned as a critical transcriptional switch downstream of the oncogenic KRAS-mitogen-activated protein kinase (MAPK) pathway, promoting the expression of genes encoding secretory factors that cumulatively sustained neoplastic proliferation, a tumorigenic stromal response in the tumor microenvironment, and PDAC progression in Kras and Kras:Trp53 mutant pancreas tissue. Together, our findings identified Yap as a critical oncogenic KRAS effector and a promising therapeutic target for PDAC and possibly other types of KRAS-mutant cancers.

Pancreatic cancer, inflammation, and microbiome

Pancreatic cancer is one of the most lethal cancers worldwide. No effective screening methods exist, and available treatment modalities do not effectively treat the disease. Inflammatory conditions such as pancreatitis represent a well-known risk factor for pancreatic cancer development. Yet only in the past 2 decades has pancreatic cancer been recognized as an inflammation-driven cancer, and the precise mechanisms underlying the pathogenic role of inflammation are beginning to be explored in detail. A substantial amount of preclinical and clinical evidence suggests that bacteria are likely to influence this process by activating immune receptors and perpetuating cancer-associated inflammation. The recent explosion of investigations of the human microbiome have highlighted how perturbations of commensal bacterial populations can promote inflammation and promote disease processes, including carcinogenesis. The elucidation of the interplay between inflammation and microbiome in the context of pancreatic carcinogenesis will provide novel targets for intervention to prevent and treat pancreatic cancer more efficiently. Further studies toward this direction are urgently needed.

Pancreatic cancer genomes: toward molecular subtyping and novel approaches to diagnosis and therapy

Pancreatic neoplasms represent a broad range of clinical entities, many of which have drastic effects on the lives of patients. Recently, high-throughput sequencing analyses have been performed in many pancreatic neoplasms, providing deep insights into the underlying biology of these neoplasms as well as novel approaches to diagnosis and treatment. This review discusses the molecular alterations underlying pancreatic neoplasms as well as the clinical impact of these alterations for diagnosis and treatment.

Precursor lesions for sporadic pancreatic cancer: PanIN, IPMN, and MCN

Pancreatic cancer is still a dismal disease. The high mortality rate is mainly caused by the lack of highly sensitive and specific diagnostic tools, and most of the patients are diagnosed in an advanced and incurable stage. Knowledge about precursor lesions for pancreatic cancer has grown significantly over the last decade, and nowadays we know that mainly three lesions (PanIN, and IPMN, MCN) are responsible for the development of pancreatic cancer. The early detection of these lesions is still challenging but provides the chance to cure patients before they might get an invasive pancreatic carcinoma. This paper focuses on PanIN, IPMN, and MCN lesions and reviews the current level of knowledge and clinical measures.

Genetic progression of pancreatic cancer

The progression from normal cells to invasive pancreatic ductal adenocarcinoma (PDAC) requires the accumulation of multiple inherited or acquired mutations. Activating point mutations in the KRAS oncogene are prevalent in pancreatic cancer and result in the stimulation of several pathways including the RAF-mitogen-activated protein kinase pathway and the phosphoinositide 3-kinase pathway. Other genetic alterations, including telomere shortening and the inactivation of tumor suppressor genes such as CDKN2A, TP53, and SMAD4, which encode p16, p53, and SMAD4, respectively, also contribute to the progression of pancreatic cancer. These, and other genetic events, can present at different stages in the development of PDAC at histologically defined precursor lesions known as pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasms, or mucinous cystic neoplasms. Each precursor lesion represents alternate routes to PDAC formation and has a unique presentation and somewhat distinct genetic events controlling its development. Despite the advances in the understanding of the genetics of PDAC, the prognosis for this cancer remains poor, and several important aspects of its pathogenesis must be clarified to improve therapeutics, including the timing and method of metastases, as well as the relationship of the tumor cells with the desmoplastic stroma, which is a characteristic feature of the cancer. This review discusses the principal genetic alterations in PDAC and its precursor lesions, including their effects on promoting carcinogenesis.

A high-fat diet activates oncogenic Kras and COX2 to induce development of pancreatic ductal adenocarcinoma in mice

BACKGROUND & AIMS

Obesity is a risk factor for pancreatic ductal adenocarcinoma (PDAC), but it is not clear how obesity contributes to pancreatic carcinogenesis. The oncogenic form of KRAS is expressed during early stages of PDAC development and is detected in almost all of these tumors. However, there is evidence that mutant KRAS requires an additional stimulus to activate its full oncogenic activity and that this stimulus involves the inflammatory response. We investigated whether the inflammation induced by a high-fat diet, and the accompanying up-regulation of cyclooxygenase-2 (COX2), increases Kras activity during pancreatic carcinogenesis in mice.

METHODS

We studied mice with acinar cell-specific expression of KrasG12D (LSL-Kras/Ela-CreERT mice) alone or crossed with COX2 conditional knockout mice (COXKO/LSL-Kras/Ela-CreERT). We also studied LSL-Kras/PDX1-Cre mice. All mice were fed isocaloric diets with different amounts of fat, and a COX2 inhibitor was administered to some LSL-Kras/Ela-CreERT mice. Pancreata were collected from mice and analyzed for Kras activity, levels of phosphorylated extracellular-regulated kinase, inflammation, fibrosis, pancreatic intraepithelial neoplasia (PanIN), and PDACs.

RESULTS

Pancreatic tissues from LSL-Kras/Ela-CreERT mice fed high-fat diets (HFDs) had increased Kras activity, fibrotic stroma, and numbers of PanINs and PDACs than LSL-Kras/Ela-CreERT mice fed control diets; the mice fed the HFDs also had shorter survival times than mice fed control diets. Administration of a COX2 inhibitor to LSL-Kras/Ela-CreERT mice prevented these effects of HFDs. We also observed a significant reduction in survival times of mice fed HFDs. COXKO/LSL-Kras/Ela-CreERT mice fed HFDs had no evidence for increased numbers of PanIN lesions, inflammation, or fibrosis, as opposed to the increases observed in LSL-Kras/Ela-CreERT mice fed HFDs.

CONCLUSIONS

In mice, an HFD can activate oncogenic Kras via COX2, leading to pancreatic inflammation and fibrosis and development of PanINs and PDAC. This mechanism might be involved in the association between risk for PDAC and HFDs.

The role of K-ras gene mutation analysis in EUS-guided FNA cytology specimens for the differential diagnosis of pancreatic solid masses: a meta-analysis of prospective studies

BACKGROUND

Differential diagnosis of pancreatic solid masses with EUS-guided FNA (EUS-FNA) is still challenging in about 15% of cases. Mutation of the K-ras gene is present in over 75% of pancreatic adenocarcinomas (PADC).

OBJECTIVE

To assess the accuracy of K-ras gene mutation analysis for diagnosing PADC.

DESIGN

We systematically searched the electronic databases for relevant studies published. Data from selected studies underwent meta-analysis by use of a bivariate model providing a pooled value for sensitivity, specificity, diagnostic odds ratio, and summary receiver operating characteristic curve.

SETTING

Meta-analysis of 8 prospective studies.

PATIENTS

Total of 931 patients undergoing EUS-FNA for diagnosis of pancreatic solid masses.

INTERVENTION

K-ras mutation analysis.

MAIN OUTCOME MEASUREMENTS

Diagnostic accuracy of K-ras mutation analysis and of combined diagnostic strategy by using EUS-FNA and K-ras mutation analysis in the diagnosis of PADC.

RESULTS

The pooled sensitivity of EUS-FNA for the differential diagnosis of PADC was 80.6%, and the specificity was 97%. Estimated sensitivity and specificity were 76.8% and 93.3% for K-ras gene analysis, respectively, and 88.7% and 92% for combined EUS-FNA plus K-ras mutation analysis. Overall, K-ras mutation testing applied to cases that were inconclusive by EUS-FNA reduced the false-negative rate by 55.6%, with a false-positive rate of 10.7%. Not repeating EUS-FNA in cases in which mutation testing of the K-ras gene is inconclusive would reduce the repeat-biopsy rate from 12.5% to 6.8%.

LIMITATIONS

Small number of studies and between-study heterogeneity.

CONCLUSION

K-ras mutation analysis can be useful in the diagnostic work-up of pancreatic masses, in particular when tissue obtained by EUS-FNA is insufficient, and the diagnosis inconclusive.

Carcinogenesis of pancreatic adenocarcinoma: precursor lesions

Pancreatic adenocarcinoma displays a variety of molecular changes that evolve exponentially with time and lead cancer cells not only to survive, but also to invade the surrounding tissues and metastasise to distant sites. These changes include: genetic alterations in oncogenes and cancer suppressor genes; changes in the cell cycle and pathways leading to apoptosis; and also changes in epithelial to mesenchymal transition. The most common alterations involve the epidermal growth factor receptor (EGFR) gene, the HER2 gene, and the K-ras gene. In particular, the loss of function of tumor-suppressor genes has been documented in this tumor, especially in CDKN2a, p53, DPC4 and BRCA2 genes. However, other molecular events involved in pancreatic adenocarcinoma pathogenesis contribute to its development and maintenance, specifically epigenetic events. In fact, key tumor suppressors that are well established to play a role in pancreatic adenocarcinoma may be altered through hypermethylation, and oncogenes can be upregulated secondary to permissive histone modifications. Indeed, factors involved in tumor invasiveness can be aberrantly expressed through dysregulated microRNAs. This review summarizes current knowledge of pancreatic carcinogenesis from its initiation within a normal cell until the time that it has disseminated to distant organs. In this scenario, highlighting these molecular alterations could provide new clinical tools for early diagnosis and new effective therapies for this malignancy.

A novel combinatorial nanotechnology-based oral chemopreventive regimen demonstrates significant suppression of pancreatic cancer neoplastic lesions

Pancreatic cancer is a deadly disease killing 37,000 Americans each year. Despite two decades of research on treatment options, the chances of survival are still less than 5% upon diagnosis. Recently, chemopreventive strategies have gained considerable attention as an alternative to treatment. We have previously shown significant in vitro chemopreventive effects with low-dose combinations of aspirin, curcumin, and sulforaphane (ACS) on pancreatic cancer cell lines. Here, we report the results of 24-week chemopreventive study with the oral administration of ACS combinations on the N-nitrosobis (2-oxopropyl) amine (BOP)-treated Syrian golden hamster model to suppress the progression of pancreatic intraepithelial neoplasms (PanIN) using unmodified (free drug) combinations of ACS, and nanoencapsulated (solid lipid nanoparticles; SLN) combinations of aspirin, curcumin, and free sulforaphane. The use of three different doses (low, medium, and high) of unmodified ACS combinations exhibited reduction in tumor incidence by 18%, 50%, and 68.7% respectively; whereas the modified nanoencapsulated ACS regimens reduced tumor incidence by 33%, 67%, and 75%, respectively, at 10 times lower dose compared with the free drug combinations. Similarly, although the unmodified free ACS showed a notable reduction in cell proliferation, the SLN encapsulated ACS regimens showed significant reduction in cell proliferation at 6.3%, 58.6%, and 72.8% as evidenced by proliferating cell nuclear antigen expression. Cell apoptotic indices were also upregulated by 1.5, 2.8, and 3.2 times, respectively, compared with BOP control. These studies provide a proof-of-concept for the use of an oral, low-dose, nanotechnology-based combinatorial regimen for the long-term chemoprevention of pancreatic cancer.

Classification, morphology and molecular pathology of premalignant lesions of the pancreas

Over the past few years there have been substantial advances in our knowledge of premalignant lesions of the pancreas. Given the dismal prognosis of untreated pancreatic cancer, and the small proportion of patients who are operative candidates, an understanding of these premalignant lesions is essential for the development of strategies for early diagnosis and prevention. The 2010 WHO classification has added new entities, including intraductal tubular papillary neoplasms (ITPNs), and clarified the nomenclature and grading of previously recognised precursor lesions of pancreatic adenocarcinoma, such as intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCNs) and pancreatic intraepithelial neoplasia (PanIN). In particular, there has been an upsurge of interest in the natural history of IPMN, driven partly by improvements in imaging modalities and the consequent apparent increase in their incidence, and partly by recognition that subtypes based on location or histological appearance define groups with significantly different behaviours. In mid 2012 revised international guidelines for the classification and management of IPMNs and MCNs were published, although in several respects these guidelines represent a consensus view rather than being evidence-based. In recent years major advances in molecular technologies, including whole-exome sequencing, have significantly enhanced our knowledge of pancreatic premalignancy and have identified potentially highly specific diagnostic biomarkers such as mutations in GNAS and RNF43 that could be used to pre-operatively assess pancreatic cysts.

Demographics and epidemiology of pancreatic cancer

Pancreatic cancer affects 44,000 Americans and at least 250,000 individuals worldwide annually. The incidence is slowly increasing after a recent period of decline. Cases are predicted to increase globally because of increased longevity and the widespread adoption of cancer-causing behaviors, such as cigarette smoking, dietary indiscretion, and a global increase in diabetes. Well-known risk factors for pancreatic cancer are advancing age, tobacco smoking, obesity, certain inherited familial disorders, second-hand smoke exposure, chronic pancreatitis, and diabetes. Associations with human immunodeficiency virus, ABO blood group, hepatitis B virus, human immunodeficiency virus, and Helicobacter pylori have also been identified.

Monoclonal antibodies and other targeted therapies for pancreatic cancer

Pancreatic cancer continues to be a challenging disease to treat because of its aggressive nature, advanced stage at the time of diagnosis, and limited treatment options that are available. Traditional cytotoxic chemotherapy provides modest benefit to patients with pancreatic adenocarcinoma. Recently, a FOLFIRINOX regimen revealed improved response in overall and progression-free survival over single-agent gemcitabine in metastatic pancreatic cancer, but there is still much needed advancement in the systemic treatment of pancreatic cancer. There is a growing interest in the development of novel agents, while our understanding of molecular pathogenesis of pancreatic adenocarcinoma continues to expand. With identification of various molecular pathways in pancreatic cancer tumorigenesis, potential targets for drug development have been pursued with the use of monoclonal antibodies and small-molecule inhibitors. Although preclinical studies with multiple targeted therapies demonstrated encouraging results in pancreatic cancer, only erlotinib, an epidermal growth factor receptor inhibitor, showed a marginal survival benefit in a phase III clinical trial, when combined with gemcitabine. As further signaling pathways and their importance in pancreatic cancer tumorigenesis are better understood, further clinical trials will need to be designed to study these targeted agents as single agents, in combination with other novel agents or in combination with cytotoxic chemotherapy. In this review, we present the current knowledge on targeted therapy in pancreatic adenocarcinoma and its application in clinical practice.

Pathology and molecular genetics of pancreatic neoplasms

Cancer is fundamentally a genetic disease caused by the accumulation of somatic mutations in oncogenes and tumor suppressor genes. In the last decade, rapid advances in sequencing and bioinformatic technology led to an explosion in sequencing studies of cancer genomes, greatly expanding our knowledge of the genetic changes underlying a variety of tumor types. Several of these studies of cancer genomes have focused on pancreatic neoplasms, and cancers from the pancreas are some of the best characterized tumors at the genetic level. Pancreatic neoplasms encompass a wide array of clinical diseases, from benign cysts to deadly cancers, and the genetic alterations underlying neoplasms of the pancreas are similarly diverse. This new knowledge of pancreatic cancer genomes has deepened our understanding of tumorigenesis in the pancreas and has opened several promising new avenues for novel diagnostics and therapeutics.

Understanding the stroma of pancreatic cancer: co-evolution of the microenvironment with epithelial carcinogenesis

Pancreatic ductal adenocarcinoma (PDAC) is a notoriously therapy-resistant desmoplastic tumour. Antifibrotic therapy is shown to increase drug delivery in the preclinical setting. However, this approach can be a double-edged sword: first, PDAC is not uniform and some types of (dormant) stroma may in fact be protective; second, conventional chemotherapeutics are not powerful enough to eradicate all cancer cells in the tumour, therefore breaking down the stromal wall non-selectively may also lead to the increased dissemination of cancer cells. Recently, Kadaba et al have analysed the impact of the stromal cells in pancreatic, oesophageal and skin cancers, in bio-engineered, physiomimetic organotypic cultures. These authors show that the maximal effect on increasing cancer cell proliferation and invasion, as well as decreasing cancer cell apoptosis, occurs when pancreatic stellate cells constitute the majority of the cellular population in a three-dimensional (3D) model. This work may be instrumental for better understanding the types of stoma in PDAC before eliminating it non-selectively.

Therapeutic advances in pancreatic cancer

Despite our improved understanding of pancreatic cancer biology and ability to perform more complex pancreatic cancer surgeries that produce better short-term outcomes, major progress toward increasing survival times has been painstakingly slow. Through the often-repeated, dismal survival statistics, it is easy to lose sight of real progress that has been made in pancreatic cancer therapy. It is particularly interesting to observe the extent to which these advances are interdependent and the effects they have had on practice. For example, during the past 5-10 years, we have seen widespread adoption of pancreatic imaging protocols that allow for objectively defined criteria of resectability. This has led to the definition of "borderline resectable pancreatic cancer"--a new clinical category that has affected the design of clinical trials. A major change in our surgical approach has been the move to minimally invasive pancreatectomy, which continues to gain broader acceptance and use, particularly for left-sided lesions. Although many new agents have been developed aimed at putative molecular targets, recent breakthroughs in therapy for advanced disease have arisen from our ability to safely give patients combination cytotoxic chemotherapy. We are now faced with the challenge of combining multidrug, cytotoxic chemotherapies with newer-generation agents. Ultimately, the hope is that drug combinations will be selected based on biomarkers, and strategies for pancreatic cancer therapy will be personalized, which could prolong patients' lives and reduce toxicity. We review the major advances in pancreatic cancer therapy during the last 5 years, and discuss how these have set the stage for greater progress in the near future.

Loss of the transcription factor GLI1 identifies a signaling network in the tumor microenvironment mediating KRAS oncogene-induced transformation

Although the biological role of KRAS is clearly established in carcinogenesis, the molecular mechanisms underlying this phenomenon are not completely understood. In this study, we provide evidence of a novel signaling network regulated by the transcription factor GLI1 mediating KRAS-induced carcinogenesis. Using pancreatic cancer (a disease with high prevalence of KRAS mutations) as a model, we show that loss of GLI1 blocks the progression of KRAS-induced pancreatic preneoplastic lesions in mice with pancreas-specific Cre-activated oncogenic mutant kras. Mice lacking GLI1 develop only low-grade lesions at low frequency, and in most cases, the pancreata are histologically normal. Further characterization of the phenotype showed a decrease in the activation of STAT3 in pancreatic preneoplastic lesions; STAT3 is a transcription factor required for the development of premalignant lesions and their progression into pancreatic cancer. Analysis of the mechanisms revealed a key role for GLI1 in maintaining the levels of activated STAT3 through the modulation of IL-6 signaling. GLI1 binds to the IL-6 mouse promoter and regulates the activity and expression of this cytokine. This newly identified GLI1/IL-6 axis is active in fibroblasts, a known source of IL-6 in the tumor microenvironment. Sonic hedgehog induces GLI1 binding to the IL-6 promoter and increases IL-6 expression in fibroblasts in a paracrine manner. Finally, we demonstrate that mutant KRAS initiates this cascade by inducing the expression of Sonic hedgehog in cancer cells. Collectively, these results define a novel role for GLI1 in carcinogenesis acting as a downstream effector of oncogenic KRAS in the tumor microenvironment.

Lkb1 regulates organogenesis and early oncogenesis along AMPK-dependent and -independent pathways

A combination of ex vivo embryonic tissue culture, genetic manipulation, and chemical genetics reveals novel details of Lkb1-mediated regulation of tissue morphogenesis.

The tumor suppressor Lkb1/STK11/Par-4 is a key regulator of cellular energy, proliferation, and polarity, yet its mechanisms of action remain poorly defined. We generated mice harboring a mutant Lkb1 knockin allele that allows for rapid inhibition of Lkb1 kinase. Culturing embryonic tissues, we show that acute loss of kinase activity perturbs epithelial morphogenesis without affecting cell polarity. In pancreas, cystic structures developed rapidly after Lkb1 inhibition. In lung, inhibition resulted in cell-autonomous branching defects. Although the lung phenotype was rescued by an activator of the Lkb1 target adenosine monophosphate–activated kinase (AMPK), pancreatic cyst development was independent of AMPK signaling. Remarkably, the pancreatic phenotype evolved to resemble precancerous lesions, demonstrating that loss of Lkb1 was sufficient to drive the initial steps of carcinogenesis ex vivo. A similar phenotype was induced by expression of mutant K-Ras with p16/p19 deletion. Combining culture of embryonic tissues with genetic manipulation and chemical genetics thus provides a powerful approach to unraveling developmental programs and understanding cancer initiation.

The role of pancreatic stellate cells in pancreatic cancer

Since conventional and targeted therapies aiming at cancer cells have largely failed to prolong survival in pancreatic cancer, targeting the infrastructure of the tumor, hence its stroma is a novel strategy. It is believed that fibrotic and hypovascular stroma forms a barrier around cancer cells, hindering effective delivery of chemotherapy. Theoretically, antifibrotic therapy should reduce the compactness of the stroma and reduce the interstitial pressure, allowing better delivery of chemotherapy. This approach has worked successfully in a genetically engineered mouse model but failed in humans, paradoxically increasing mortality in the treatment arm. Normally, stromal cells deposit extracellular matrix as an innate defensive reaction to form a barrier between what is harmful and the rest of the body. Despite the significant amount of in vitro data suggesting the pro-tumorigenic roles of activated stellate cells, there is no reason to believe that stellate cells around genetically mutated cells are from the beginning there to support carcinogenesis. Such a stromal activation is also observed around PanIN lesions (which harbor genetically mutated cells) in chronic pancreatitis, where no cancer develops. In pancreatic cancer, the selection pressure created by the fibrotic and hypoxic stroma eventually leads to the evolution of more aggressive clones, indirectly contributing to the aggressiveness of the tumor. Here, the main problem is the late diagnosis of pancreatic cancer, which gives cancer cells enough time for malignant evolution. Therefore, applying antifibrotic therapy at a late stage can be counterproductive. It may increase delivery of chemotherapy, but also lead to the escape of cancer cells.

Oncogenic transcription factors: cornerstones of inflammation-linked pancreatic carcinogenesis

Transcription factors are proteins that regulate gene expression by modulating the synthesis of messenger RNA. Since this process is often one dominant control point in the production of many proteins, transcription factors represent the key regulators of numerous cellular functions, including proliferation, differentiation and apoptosis. Pancreatic cancer progression is characterised by activation of inflammatory signalling pathways converging on a limited set of transcription factors that fine-tune gene expression patterns contributing to the growth and maintenance of these tumours. Thus strategies targeting these transcriptional networks activated in pancreatic cancer cells could block the effects of upstream inflammatory responses participating in pancreatic tumorigenesis. The authors review this field of research and summarise current strategies for targeting oncogenic transcription factors and their activating signalling networks in the treatment of pancreatic cancer.