Molecular biology of pancreatic cancer; oncogenes, tumour suppressor genes, growth factors, and their receptors from a clinical perspective

The role of AMPK in pancreatic cancer: from carcinogenesis to treatment

Pancreatic cancer has doubled over the previous two decades. Routine therapies are becoming incredibly resistant and failing to compensate for the burden caused by this aggressive neoplasm. As genetic susceptibility has always been a highlighted concern for this disease, identifying the molecular pathways involved in the survival and function of pancreatic cancer cells provides insight into its variant etiologies, one of which is the role of AMPK. This regulating factor of cell metabolism is crucial in the homeostasis and growth of the cell. Herein, we review the possible role of AMPK in pancreatic cancer while considering its leading effects on glycolysis and autophagy. Then, we assess the probable therapeutic agents that have resulted from the suggested pathways. Studying the underlying genetic changes in pancreatic cancer provides a chance to detect and treat patients suffering from advanced stages of the disease, and those who have given up their hope on conventional therapies can gain an opportunity to combat this cancer.

The Link between Diabetes, Pancreatic Tumors, and miRNAs-New Players for Diagnosis and Therapy?

Despite significant progress in medicine, pancreatic cancer is one of the most tardily diagnosed cancer and is consequently associated with a poor prognosis and a low survival rate. The asymptomatic clinical picture and the lack of relevant diagnostic markers for the early stages of pancreatic cancer are believed to be the major constraints behind an accurate diagnosis of this disease. Furthermore, underlying mechanisms of pancreatic cancer development are still poorly recognized. It is well accepted that diabetes increases the risk of pancreatic cancer development, however the precise mechanisms are weakly investigated. Recent studies are focused on microRNAs as a causative factor of pancreatic cancer. This review aims to provide an overview of the current knowledge of pancreatic cancer and diabetes-associated microRNAs, and their potential in diagnosis and therapy. miR-96, miR-124, miR-21, and miR-10a were identified as promising biomarkers for early pancreatic cancer prediction. miR-26a, miR-101, and miR-200b carry therapeutic potential, as they not only regulate significant biological pathways, including the TGF-β and PI3K/AKT, but their re-expression contributes to the improvement of the prognosis by reducing invasiveness or chemoresistance. In diabetes, there are also changes in the expression of microRNAs, such as in miR-145, miR-29c, and miR-143. These microRNAs are involved, among others, in insulin signaling, including IRS-1 and AKT (miR-145), glucose homeostasis (hsa-miR-21), and glucose reuptake and gluconeogenesis (miR-29c). Although, changes in the expression of the same microRNAs are observed in both pancreatic cancer and diabetes, they exert different molecular effects. For example, miR-181a is upregulated in both pancreatic cancer and diabetes mellitus, but in diabetes it contributes to insulin resistance, whereas in pancreatic cancer it promotes tumor cell migration, respectively. To conclude, dysregulated microRNAs in diabetes affect crucial cellular processes that are involved in pancreatic cancer development and progression.

Liquid biopsy approach to pancreatic cancer

Pancreatic cancer (PC) continues to pose a major clinical challenge. There has been little improvement in patient survival over the past few decades, and it is projected to become the second leading cause of cancer mortality by 2030. The dismal 5-year survival rate of less than 10% after the diagnosis is attributable to the lack of early symptoms, the absence of specific biomarkers for an early diagnosis, and the inadequacy of available chemotherapies. Most patients are diagnosed when the disease has already metastasized and cannot be treated. Cancer interception is vital, actively intervening in the malignization process before the development of a full-blown advanced tumor. An early diagnosis of PC has a dramatic impact on the survival of patients, and improved techniques are urgently needed to detect and evaluate this disease at an early stage. It is difficult to obtain tissue biopsies from the pancreas due to its anatomical position; however, liquid biopsies are readily available and can provide useful information for the diagnosis, prognosis, stratification, and follow-up of patients with PC and for the design of individually tailored treatments. The aim of this review was to provide an update of the latest advances in knowledge on the application of carbohydrates, proteins, cell-free nucleic acids, circulating tumor cells, metabolome compounds, exosomes, and platelets in blood as potential biomarkers for PC, focusing on their clinical relevance and potential for improving patient outcomes.

Peptide-Based Therapeutics for Oncology

The development of peptide-based drugs, which are usually synthetic analogues of endogenous peptides, is currently one of the most topical directions in drug development. Among them, antitumor peptide-based drugs are of great interest. Anticancer peptides can be classified into three main groups based on their mechanism of action: inhibitory, necrosis-inducing and pro-apoptotic peptides. As an antitumor therapy, peptides are considered to have at least the same efficacy as chemotherapy or surgical treatment, but offer advantages in terms of safety and tolerability, given that chemotherapy is usually characterized by severe adverse effects, and surgery carries additional risks for patients. Short peptides have a number of benefits over other molecules. First, compared with full-length proteins and antibodies, short peptides are less immunogenic, more stable ex-vivo (prolonged storage at room temperature), and have better tumor or organ permeability. Moreover, the production of such short peptide-based drugs is more cost effective. Second, in comparison with small organic molecules, peptides have higher efficacy and specificity. Finally, due to the fact that the main products of peptide metabolism are amino acids, these drugs are usually characterized by lower toxicity. Short peptides have a highly selective mechanism of action, thereby demonstrating low toxicity. Furthermore, with the addition of different stabilizing structural modifications, as well as novel drug delivery systems, the peptide-based drugs are proving to be promising therapeutics for cancer mono- or polytherapy. However, challenges remain including that endogenous and synthetic peptide molecules can be oncogenic. Therefore, it is important to investigate whether peptides contribute to tumor growth. In order to answer such questions, numerous preclinical and clinical studies of peptide-based therapeutics are currently being conducted.

The active role of the transcription factor Sp1 in NFATc2-mediated gene regulation in pancreatic cancer

BACKGROUND

Adenocarcinoma of the pancreas is one of the most aggressive tumor diseases affecting the human body. The oncogenic potential of pancreatic cancer is mainly characterized by extremely rapid growth triggered by the activation of oncogenic signaling cascades, which suggests a change in the regulation of important transcription factors. Amongst others, NFAT transcription factors are assumed to play a central role in the carcinogenesis of pancreatic cancer. Recent research has shown the importance of the transcription factor Sp1 in the transcriptional activity of NFATc2 in pancreatic cancer. However, the role of the interaction between these two binding partners remains unclear. The current study investigated the role of Sp1 proteins in the expression of NFATc2 target genes and identified new target genes and their function in cells. A further objective was the domain of the Sp1 protein that mediates interaction with NFATc2. The involvement of Sp1 proteins in NFATc2 target genes was shown by means of a gene expression profile analysis, and the results were confirmed by quantitative RT-PCR. The functional impact of this interaction was shown in a thymidine incorporation assay. A second objective was the physical interaction between NFATc2 and different Sp1 deletion mutants that was investigated by means of immunoprecipitation.

RESULTS

In pancreatic cancer, the proto-oncogene c-Fos, the tumor necrosis factor TNF-alpha, and the adhesion molecule integrin beta-3 are target genes of the interaction between Sp1 and NFATc2. Loss of just one transcription factor inhibits oncogenic complex formation and expression of cell cycle-regulating genes, thus verifiably decreasing the carcinogenic effect. The current study also showed the interaction between the transcription factor NFATc2 and the N-terminal domain of Sp1 in pancreatic cancer cells. Sp1 increases the activity of NFATc2 in the NFAT-responsive promoter.

CONCLUSIONS

The regulation of gene promotors during transcription is a rather complex process because of the involvement of many proteins that - as transcription factors or co-factors - regulate promotor activity as required and control cell function. NFATc2 and Sp1 seem to play a key role in the progression of pancreatic cancer.

Pathological and prognostic role of mdig in pancreatic cancer

Pancreatic cancer is a highly aggressive malignant disease having very limited therapeutic options that ultimately results in its poor prognosis. It is still elusive on the etiology and tumorigenic mechanisms of pancreatic cancer. In the present report, we provide evidence showing involvement of the mineral dust-induced gene (mdig) in the pathogenesis and prognosis of the pancreatic cancer. Using immunohistochemistry approach on human pancreatic cancer tissue microarray, we found differential expression of mdig in pancreatic adenocarcinoma and normal pancreas. Based on the staining intensities of mdig in these tissue samples, we found that 12% of the cancer tissues were strongly positive for mdig, 39% and 31% were moderately and weakly positive respectively. Several alternatively spliced mdig mRNAs were detected in the selected pancreatic cancer cell lines. Through R2 platform for the patient survival analysis (http://r2.amc.nl), we found that enrichment of some specific exon of mdig predicates different survival rate of the pancreatic cancer patients. In summary, our findings may help in assessing the role of mdig in the pathogenesis of the pancreatic cancer and the prognosis of the pancreatic cancer patients.

Pancreas specific expression of oncogenes in a porcine model

Pancreatic cancer is the fourth leading course of cancer death and early detection of the disease is crucial for successful treatment. However, pancreatic cancer is difficult to detect in its earliest stages and once symptoms appear, the cancer has often progressed beyond possibility for curing. Research into the disease has been hampered by the lack of good models. We have generated a porcine model of pancreatic cancer with use of transgenic overexpression of an oncogene cassette containing MYC, KRAS ^G12D and SV40 LT. The expression was initiated from a modified Pdx-1 promoter during embryogenesis in a subset of pancreatic epithelial cells. Furthermore, cells expressing the oncogenes also expressed a yellow fluorescent protein (mVenus) and an inducible negative regulator protein (rtTR-KRAB). Cells where the Pdx-1 promoter had not been activated, expressed a red fluorescent protein (Katushka). In vitro analyses of cells obtained from the transgenic pigs showed increased proliferation and expression of the transgenes when activated. Induction of the repressor protein eliminated the oncogene expression and decreased cell proliferation. In vivo analysis identified foci of pancreatic cells expressing the oncogenes at day zero post farrowing. These populations expanded and formed hyperplastic foci, with beginning abnormality at day 45. Cells in the foci expressed the oncogenic proteins and the majority of the cells were positive for the proliferation marker, Ki67. We predict that this model could be used for advanced studies in pancreatic cancer in a large animal model with focus on early detection, treatment, and identification of new biomarkers.

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.

Predicting novel salivary biomarkers for the detection of pancreatic cancer using biological feature-based classification

AIM

The use of saliva as a diagnostic fluid enables non-invasive sampling and thus is a prospective sample for disease tests. This study fully utilized the information from the salivary transcriptome to characterize pancreatic cancer related genes and predict novel salivary biomarkers.

METHODS

We calculated the enrichment scores of gene ontology (GO) and pathways annotated in Kyoto Encyclopedia of Genes and Genomes database (KEGG) for pancreatic cancer-related genes. Annotation of GO and KEGG pathway characterize the molecular features of genes. We employed Random Forest classification and incremental feature selection to identify the optimal features among them and predicted novel pancreatic cancer-related genes.

RESULTS

A total of 2175 gene ontology and 79 KEGG pathway terms were identified as the optimal features to identify pancreatic cancer-related genes. A total of 516 novel genes were predicted using these features. We discovered 29 novel biomarkers based on the expression of these 516 genes in saliva. Using our new biomarkers, we achieved a higher accuracy (92%) for the detection of pancreatic cancer. Another independent expression dataset confirmed that these novel biomarkers performed better than the previously described markers alone.

CONCLUSION

By analyzing the information of the salivary transcriptome, we predict pancreatic cancer-related genes and novel salivary gene markers for detection.

A meta-analysis of the diagnostic value of detecting K-ras mutation in pancreatic juice as a molecular marker for pancreatic cancer

BACKGROUND

K-ras codon 12 mutation is one of the earliest genetic changes in the development of pancreatic cancer (PC) and accurate detection of K-ras mutations is gaining increasing attention in the field of molecular diagnosis.

METHODS

Original research articles which evaluated the diagnostic accuracy of K-ras mutation detection in PC were selected. Data were presented as forest plots and summary receiver operating characteristic curve analysis was used to summarize the overall test performance.

RESULTS

We assessed 16 studies from 15 published articles. The pooled sensitivity and specificity were 59% (95%CI: 54%-64%) and 87% (95%CI: 84%-89%), respectively. The pooled positive likelihood ratio and negative likelihood ratio were 4.13 (95%CI: 2.73-6.25) and 0.42 (95%CI: 0.32-0.56), respectively, and the pooled diagnostic odds ratio was 13.66 (95% CI: 7.25-25.74).

CONCLUSIONS

Our results indicate that the analysis of K-ras mutations in pancreatic juice has a considerable diagnostic value in PC. Further studies with rigorous design, large sample size, and multi-regional co-operation are needed.

Development of a cytokine-modified allogeneic whole cell pancreatic cancer vaccine

Management of patients with pancreatic cancer is a multidisciplinary approach that presents enormous challenges to the clinician. Overall 5-year survival for all patients remains <3%. Symptoms of early pancreas cancer are nonspecific. As such, only a fraction of patients are candidates for surgery. While surgical resection provides the only curative option, most patients will develop tumor recurrence and die of their disease. To date, the clinical benefits of chemotherapy and radiation therapy have been important but have led to modest improvements. Tumor vaccines have the potential to specifically target the needle of pancreas cancer cells amidst the haystack of normal tissue. The discovery of pancreas tumor-specific antigens and the subsequent ability to harness this technology has become an area of intense interest for tumor immunologists and clinicians alike. Without knowledge of specific antigen targets, the whole tumor cell represents the best source of immunizing antigens. This chapter will focus on the development of whole tumor cell vaccine strategies for pancreas cancer.

Interplay between autophagy and apoptosis in pancreatic tumors in response to gemcitabine

Pancreatic cancer is an aggressive disease. Its incidence has increased over the last two decades. It is currently the fourth cause of death among cancers in the western world. Unfortunately, systemic chemotherapy still relies on just a few drugs which until now have produced unsatisfactory results. Gemcitabine (2'-2'-difluorodeoxycytidine) is currently the standard chemotherapy treatment at all stages of pancreatic adenocarcinoma. Survival benefit and clinical impact however remain moderate due to a high degree of intrinsic and acquired resistance. Autophagy plays an important role in cell death decision but can also protect cells from various apoptotic stimuli. We investigated the function of autophagy in pancreatic carcinoma cells, which are frequently insensitive to standard chemotherapeutic agents. Here, we demonstrate that autophagy is one of the mechanisms responsible for the refractory response of pancreatic tumors to gemcitabine. We present evidence in vitro and in vivo that proves autophagy plays a protective role in pancreatic ductal carcinoma cells, preventing them from entering the apoptotic pathway after stimulus with gemcitabine, thus contributing to treatment resistance. A better understanding of the role in the process may help in the discovery of new strategies to overcome tumor drug resistance in this aggressive disease.

Atorvastatin delays progression of pancreatic lesions to carcinoma by regulating PI3/AKT signaling in p48Cre/+ LSL-KrasG12D/+ mice

Pancreatic cancer is the one of most common causes of cancer deaths and has the worst prognosis. Clinical observational studies suggest that statins may reduce the risk of pancreatic cancer. The chemopreventive efficacy of the statin atorvastatin (Lipitor(®)) and the role of the phosphatidyl-inositol 3-kinase (PI3/AKT) signaling pathway were evaluated for the progression of pancreatic intraepithelial neoplasms (PanINs) to pancreatic ductal adenocarcinoma (PDAC) in conditional p48(Cre/+) -LSL-Kras(G12D/+) transgenic mice. Six-week-old male p48(Cre/+) -LSL-Kras(G12D/+) (20/group) mice were fed AIN-76A diets containing 0, 200 and 400 ppm atorvastatin for 35 weeks. At termination, pancreata were evaluated histopathologically for PanINs and PDAC, and for various PI3/AKT signaling markers, and inflammatory cytokines, by immunohistochemistry/immunohistoflourscence, ELISA, Western blotting and/or reverse transcription-PCR methods. Control diet-fed mice showed 85% incidence of PDAC; whereas, mice fed with atorvastatin showed PDAC incidence of 65 and 35%, respectively (p < 0.0001). Similarly, significant suppression of PanIN-3 (22.6%) was observed in mice fed 400 ppm atorvastatin. Importantly, pancreata from atorvastatin-treated mice were ∼68% free from ductal lesions. Furthermore, pancreas of mice administered with atorvastatin had significantly reduced expressions levels of PCNA, p2X7, p-ERK, RhoA, cyclin D1, survivin, Akt, pAKT, β-catenin, cyclin E, cdK2 and caveolin-1. Also, atorvastatin-treated mice had shown dose-dependent suppression of inflammatory cytokines and a significant increase in tunnel-positive cells, p21 and PARP expression levels in pancreas. Atorvastatin significantly delays the progression of PanIN-1 and -2 lesions to PanIN-3 and PDAC by modulating PI3/AKT signal molecules in a preclinical model, suggesting potential clinical benefits of statins for high-risk pancreatic cancer patients.

Advances in biomarker research for pancreatic cancer

Pancreatic cancer (PC) is a leading cause of cancer related deaths in United States. The lack of early symptoms results in latestage detection and a high mortality rate. Currently, the only potentially curative approach for PC is surgical resection, which is often unsuccessful because the invasive and metastatic nature of the tumor masses makes their complete removal difficult. Consequently, patients suffer relapses from remaining cancer stem cells or drug resistance that eventually lead to death. To improve the survival rate, the early detection of PC is critical. Current biomarker research in PC indicates that a serum carbohydrate antigen, CA 19-9, is the only available biomarker with approximately 90% specificity to PC. However, the efficacy of CA 19-9 for assessing prognosis and monitoring patients with PC remains contentious. Thus, advances in technology and the detection of new biomarkers with high specificity to PC are needed to reduce the mortality rate of pancreatic cancer.

GABA (γ-aminobutyric acid), a non-protein amino acid counters the β-adrenergic cascade-activated oncogenic signaling in pancreatic cancer: a review of experimental evidence

GABA is a bioactive constituent of fruits, vegetables, cereals and is believed to play a role in defense against stress in plants. In animals, it acts as an inhibitory neurotransmitter in brain while also expressed in non-neuronal cells. Studies have implicated the regulator of fight or flight stress responses, β-AR signaling cascade, as mediators of cancer growth and progression in in vitro and in vivo models of pancreatic malignancies. Pancreatic cancer is the fourth leading cause of cancer mortality in western countries. This malignancy is generally unresponsive to conventional radio- and chemotherapy, resulting in mortality rate near 100% within 6 months of diagnosis. We review a series of experiments from our laboratory and those of others examining the contribution of this signaling network to pancreatic and other human malignancies. Stimulation of the β-adrenergic receptor by lifestyle and environmental factors, as well as a pre-existing risk of neoplasm, activates downstream effector molecules that lead to pro-oncogenic signaling and thereby aid cancer growth. GABAergic signaling mediated by the serpentine receptor GABA(B) acts as an antagonist to β-adrenergic cascade by intercepting adenylyl cyclase. These evidences enhance the pharmacological value of human diets rich in GABA for use as an adjuvant to standard therapies.

Study of apoptosis induction and deoxycytidine kinase/cytidine deaminase modulation in the synergistic interaction of a novel ceramide analog and gemcitabine in pancreatic cancer cells

This study investigated the interaction between the novel ceramide analog AL6 and gemcitabine in MIA PaCa-2 and PANC-1 pancreatic cancer cell lines, harboring different polymorphic variants of the gemcitabine catabolism enzyme cytidine deaminase (CDA). AL6 dose-dependently inhibited cell growth, induced apoptosis and synergistically enhanced the cytotoxic activity of gemcitabine. Moreover, it triggered apoptosis, which was significantly enhanced by the combination, and increased the ratio between gene expression of the activating enzyme deoxycytidine kinase (dCK) and CDA, potentially favoring gemcitabine activity. In conclusion, AL6 displays synergistic cytotoxic activity, enhances apoptosis, and favorably modulates enzymes involved in gemcitabine metabolism, supporting future investigation of this combination in pancreatic cancer.

Resequencing analysis of the human tyrosine kinase gene family in pancreatic cancer

OBJECTIVES

Pancreatic cancer is one of the most intractable of cancers. However, the comprehensive view of somatic mutations in this tumor is far from clear. The tyrosine kinase (TK) gene family, which encodes important regulators of various signal transduction pathways, is one of the most frequently altered gene families in human cancer.

METHODS

To clarify the somatic mutation profile of TKs in pancreatic cancer, we performed a systematic screening of mutations in the kinase domains of all human TK genes (636 exons of 90 genes in total) in 11 pancreatic cancer cell lines and 29 microdissected primary tumors.

RESULTS

We identified 15 nonsynonymous alterations that included 9 DNA alterations in cell lines and 6 somatic mutations in primary tumors. In particular, we identified the previously reported pathogenic mutation of NTRK3 in a KRAS/BRAF wild-type tumor and 2 somatic mutations in the Src family of kinases (YES1 and LYN) that would be expected to cause structural changes.

CONCLUSIONS

Our genome-wide resequencing approach revealed novel oncogenic pathways in pancreatic cancers.

Challenges in developing targeted therapy for pancreatic adenocarcinoma

BACKGROUND

Pancreatic adenocarcinoma is a leading cause of cancer deaths in the US. Gemcitabine-based chemotherapy remains the cornerstone treatment for advanced pancreatic cancers. Research into the molecular pathogenesis of pancreatic cancers has allowed scientists to understand the complex heterogeneous signals associated with them. Targeting these pathways with chemical inhibitors could improve patient outcome.

OBJECTIVE

To describe the molecular heterogeneity typical of pancreatic cancers and to discuss targeted therapies in development, and the challenges facing these agents.

METHODS

We reviewed Pub Med. literature, clinical trial database (clinicaltrials.gov), American Society of Clinical Oncology (ASCO) and American Association of Cancer Research (AACR) websites.

CONCLUSIONS

Molecular pathogenesis of pancreatic cancer involves multiple pathways and defined mutations. This molecular heterogeneity is a major reason for failure of targeted therapy. Targeting multiple oncogenic pathways using novel targeted therapies could improve patient survival.

Role of Ras signaling in the induction of snail by transforming growth factor-beta

The epithelial-mesenchymal transition (EMT) is a crucial morphological event that occurs during the progression of epithelial tumors. EMT can be induced by transforming growth factor (TGF)-beta in some tumor cells. Here, we demonstrate the molecular mechanism whereby Snail, a key regulator of EMT, is induced by TGF-beta in tumor cells. Snail induction by TGF-beta was highly dependent on cooperation with active Ras signals, and silencing of Ras abolished Snail induction by TGF-beta in pancreatic cancer Panc-1 cells. Transfection of constitutively active Ras into HeLa cells led to induction of Snail by TGF-beta, while representative direct targets of TGF-beta, including Smad7 and PAI-1, were not affected by Ras signaling. Using mitogen-activated protein kinase inhibitors or Smad3 or Smad2 mutants, we found that phosphorylation at the linker region of Smad2/3 was not required for the induction of Snail by TGF-beta. Taken together, these findings indicate that Ras and TGF-beta-Smad signaling selectively cooperate in the induction of Snail, which occurs in a Smad-dependent manner, but independently of phosphorylation at the linker region of R-Smads by Ras signaling.

Magnetic resonance imaging monitors physiological changes with antihedgehog therapy in pancreatic adenocarcinoma xenograft model

OBJECTIVES

The sonic hedgehog (Shh) pathway has an established role in pancreatic cancer (pancreatic adenocarcinoma [PDAC]). We tested whether magnetic resonance imaging measures of vascular volume fraction (VVF) using magnetic iron oxide nanoparticles are sensitive to the antiangiogenic effect of targeted Shh therapies in a PDAC xenograft model.

METHODS

Pancreatic adenocarcinoma xenograft lines were subcutaneously implanted into nude mice (n = 19 samples within 4 groups). Therapies were targeted to 3 loci of the Shh signaling pathway (anti-Shh antibody, cyclopamine, or forskolin). Magnetic resonance imaging (4.7-T Bruker Pharmascan) was performed (after 1 week of intraperitoneal therapy) before and after intravenous injection of MION-47. Vascular volume fraction was quantified as DeltaR2 (from multicontrast T2 sequences) and normalized to an assumed VVF in muscle of 3%. Linear regression compared VVF to histological indices including microvessel density (MVD), viable gland density (VGD), and proliferative index (PI).

RESULTS

In response to anti-Hh treatment, tumors showed a decrease in VGD, PI, MVD, and VVF compared with controls (P < 0.001). Vascular volume fraction was compared with histological indicators of response: PI (R2 = 0.88; P < 0.05), VGD (R2 = 0.87; P< 0.05), and MVD (R2 = 0.85; P < 0.05).

CONCLUSIONS

Magnetic resonance imaging VVF using magnetic iron oxide nanoparticles may serve as a noninvasive measure of biological response to Shh PDAC therapy with easy translation to the clinic.

Pancreatic cancer: from molecular signature to target therapy

Pancreatic adenocarcinoma is a leading cause of cancer death in western countries. The treatment of advanced disease with gemcitabine has only a modest activity on survival with a favourable impact on quality of life. However, recent data support the evidence that the combination of gemcitabine with erlotinib, capecitabine or platinum compounds could be more active than gemcitabine alone in advanced pancreatic cancer. New therapeutic strategies, particularly using molecular target agents, are under evaluation. A number of molecular mechanisms responsible of transformation and progression of pancreatic cancer have been identified, opening the possibility to identify also possible pharmacological targets. A promising approach is the pharmacological inhibition of tumor angiogenesis with anti-vascular endothelial growth factor (VEGF) agents, such as bevacizumab, cyclooxygenase-2 inhibitors (celecoxib), thalidomide and others. Also epidermal growth factor receptor (EGFR) plays an important role in progression of pancreatic cancer. Erlotinib, an oral available anti-EGFR compound, was the first agent capable to significantly improve overall survival in a phase III trial, leading to its approval by Food and Drug Administration (FDA) in combination with gemcitabine as first-line therapy. Ongoing studies are exploring the role of targeted therapy in the adjuvant setting. However, despite these promising results, several questions remain to be resolved, including the rational selection of the patients who are more likely to obtain benefit of target therapy, the choice of the optimal therapeutic schedule of therapy, the clinical setting of choice, and the management of the toxicity.

GABA B receptor is a novel drug target for pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death. Smoking, diabetes, and pancreatitis are risk factors. It has been shown that the growth of PDAC and pancreatic duct epithelial cells is regulated by beta-adrenoreceptors (beta-ARs). The activity of beta-ARs in the central nervous system is counteracted by gamma-aminobutyric acid (GABA) via GABA B receptor-mediated inhibition of adenylyl cyclase. The aim of the study was to investigate if GABA B R inhibits beta-AR signaling in PDAC and pancreatic duct epithelial cells, thus blocking driving forces of cancer progression, such as cell proliferation and cell migration.

METHODS

Intracellular cAMP was measured by immunoassays, DNA synthesis by BrdU incorporation assays, activation of ERK1/2 by ERK activation assays, and Western blots and metastatic potential by cell migration assays in the human PDAC cell lines PANC-1 and BXPC-3 and immortalized human pancreatic duct epithelial cells HPDE6-C7. The expression of norepinephrine, PKAR IIalpha, and GABA in PDAC microarrays was assessed by immunohistochemistry. RESULTS.: Stimulation of the GABA B R by GABA or baclofen inhibited isoproterenol-induced cAMP signaling below base levels. ERK1/2 activity in response to isoproterenol was blocked by GABA, an effect enhanced by transient overexpression of the GABA B R and abolished by GABA B R knockdown. DNA synthesis and cell migration were stimulated by isoproterenol, responses blocked by GABA and baclofen. Norepinephrine and PKAR IIalpha were overexpressed while GABA was underexpressed in human PDAC tissue arrays.

CONCLUSIONS

The data suggest the stimulation of GABA B R signaling as a novel target for the treatment and prevention of pancreatic cancer.

Prognostic significance of growth factors and the urokinase-type plasminogen activator system in pancreatic ductal adenocarcinoma

OBJECTIVES

To determine the diagnostic and prognostic significance of growth factors and the urokinase-type plasminogen activator (uPA) system in pancreatic ductal adenocarcinoma (PDAC) using a multigene assay.

METHODS

Messenger RNA (mRNA) expression of 15 genes from epidermal growth factor receptor, insulin-like growth factor (IGF), and uPA families were measured in 46 PDAC tissue samples using quantitative real-time reverse transcription-polymerase chain reaction. These results were compared with those of the uninvolved adjacent (AP) tissue and benign mucinous cystadenomas (BMC). The mRNA expression was evaluated using logistic regression and receiver operating characteristic area under the curve (ROC AUC) analyses. Their relationship with prognosis was tested by Cox regression multivariate analysis.

RESULTS

All genes were overexpressed in most of the PDAC tissue. When compared with AP tissue, the median expression values for IGF-binding protein 3 (IGFBP-3) and uPA receptor (uPAR) was 9.8- and 9.6-fold, respectively. Expression levels of uPA, uPAR, IGF-I, and IGFBP-3 mRNA were significantly greater in PDAC than in BMC. The IGFBP-3 mRNA expression demonstrated greatest ROC AUC values for PDAC versus AP tissue (ROC AUC, 0.745; 95% confidence interval [CI], 0.65-0.86); whereas ROC AUC values were greatest for uPAR when PDAC was compared with BMC (ROC AUC, 0.846; 95% CI, 0.76-0.94). The combination of uPA, uPAR, and IGF-I significantly improved discriminatory power (ROC AUC, 0.965; 95% CI, 0.93-1.00). The IGFBP-3, uPA, plasminogen activator inhibitor-2, and International Union Against Cancer stage had a significant influence on survival, but the effect of IGFBP-3 was lost after multivariate stepwise analysis.

CONCLUSIONS

These results indicate that there is an influence of IGF system in tumor progression from BMC to PDAC, whereas the uPA/uPAR system has the greater influence on survival in PDAC.

The OGF-OGFr axis utilizes the p21 pathway to restrict progression of human pancreatic cancer

Background

Pancreatic cancer is the 4th leading cause of death from cancer in the U.S. The opioid growth factor (OGF; [Met⁵]-enkephalin) and the OGF receptor form an inhibitory growth regulatory system involved in the pathogenesis and treatment of pancreatic cancer. The OGF-OGFr axis influences the G₀/G₁ phase of the cell cycle. In this investigation, we elucidate the pathway of OGF in the cell cycle.

Results

Using BxPC-3 cells, OGF decreased phosphorylation of retinoblastoma (Rb) protein without changing total Rb. This change was correlated with reduced cyclin-dependent kinase protein (Cdk) 2 kinase activity, but not total Cdk2. OGF treatment increased cyclin-dependent kinase inhibitor (CKI) p21 protein expression in comparison to controls, as well levels of p21 complexed with Cdk2. Naloxone abolished the increased expression of p21 protein by OGF, suggesting a receptor-mediated activity. p21 specific siRNAs blocked OGF's repressive action on proliferation in BxPC-3, PANC-1, and Capan-2 cells; cells transfected with negative control siRNA had no alteration in p21 expression, and therefore were inhibited by OGF.

Conclusion

These data are the first to reveal that the target of cell proliferative inhibitory action of OGF in human pancreatic cancer is a p21 CKI pathway, expanding strategies for diagnosis and treatment of these neoplasias.

Synergistic Antitumor Activity of ZD6474, An Inhibitor of Vascular Endothelial Growth Factor Receptor and Epidermal Growth Factor Receptor Signaling, with Gemcitabine and Ionizing Radiation against Pancreatic Cancer

PURPOSE

Standard treatments have modest effect against pancreatic cancer, and current research focuses on agents targeting molecular pathways involved in tumor growth and angiogenesis. This study investigated the interactions between ZD6474, an inhibitor of tyrosine kinase activities of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor (EGFR), gemcitabine, and ionizing radiation in human pancreatic cancer cells and analyzed the molecular mechanisms underlying this combination.

EXPERIMENTAL DESIGN

ZD6474, ionizing radiation, and gemcitabine, alone or in combination, were given in vitro to MIA PaCa-2, PANC-1, and Capan-1 cells and in vivo to MIA PaCa-2 tumor xenografts. The effects of treatments were studied by the evaluation of cytotoxicity, apoptosis, cell cycle, EGFR and Akt phosphorylation, modulation of gene expression of enzymes related to gemcitabine activity (deoxycytidine kinase and ribonucleotide reductase), as well as vascular endothelial growth factor immunohistochemistry and microvessel count.

RESULTS

In vitro, ZD6474 dose dependently inhibited cell growth, induced apoptosis, and synergistically enhanced the cytotoxic activity of gemcitabine and ionizing radiation. Moreover, ZD6474 inhibited phosphorylation of EGFR and Akt and triggered cell apoptosis. PCR analysis showed that ZD6474 increased the ratio between gene expression of deoxycytidine kinase and ribonucleotide reductase. In vivo, ZD6474 showed significant antitumor activity alone and in combination with radiotherapy and gemcitabine, and the combination of all three modalities enhanced MIA PaCA-2 tumor growth inhibition compared with gemcitabine alone.

CONCLUSIONS

ZD6474 decreases EGFR and Akt phosphorylation, enhances apoptosis, favorably modulates gene expression in cancer cells, and acts synergistically with gemcitabine and radiotherapy to inhibit tumor growth. These findings support the investigation of this combination in the clinical setting.

Ethanol and the tobacco-specific carcinogen, NNK, contribute to signaling in immortalized human pancreatic duct epithelial cells

OBJECTIVES

Smoking is a well-documented risk factor for pancreatic cancer. The tobacco-specific nitrosamine, NNK (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanone), significantly induces pancreatic ductal adenocarcinomas in laboratory rodents. Recent observations suggest that ethanol enhances the tumorigenic effects of smoking. Ethanol consumption is associated with the development of chronic pancreatitis, also considered a predisposing factor for pancreatic ductal adenocarcinoma. Because the precise role of ethanol in pancreatic carcinogenesis is not known, this study sought to elucidate the cumulative effects of ethanol and NNK on particular signal transduction pathways that might play a role in cell proliferation in immortalized human pancreatic duct epithelial cells.

METHODS

The HPDE6-c7 cells are developed from pancreatic duct epithelial cells, which are the putative cells of origin of pancreatic ductal adenocarcinoma. Cell proliferation assays, Western blot, and cyclic adenosine monophosphate assays were used to demonstrate the effects of ethanol and NNK treatments on these cells.

RESULTS

Ethanol cotreatments enhanced the NNK-induced proliferation of these cells. This response was inhibited by the adenylyl cyclase, protein kinase A, mitogen-activated protein kinase (p42/p44), and epidermal growth factor receptor-specific tyrosine kinase inhibitors. Cotreatments of NNK and ethanol also increased cyclic adenosine monophosphate accumulation, cAMP response element-binding family of proteins and mitogen-activated protein kinase phosphorylation, and protein kinase A activation.

CONCLUSIONS

These findings suggest a potential role for these pathways contributing to the development of smoking- and alcohol-related pancreatic carcinogenesis.

Pharmacogenetics of anticancer drug sensitivity in pancreatic cancer

Chemotherapy has produced unsatisfactory results in pancreas cancer and novel approaches, including treatment tailoring by pharmacogenetic analysis and new molecular-targeted drugs, are required. The scarcity of effective therapies may reflect the lack of knowledge about the influence of tumor-related molecular abnormalities on responsiveness to drugs. Advances in the understanding of pancreas cancer biology have been made over the past decade, including the discovery of critical mutations in oncogenes (i.e., K-Ras) as well as the loss of tumor suppressor genes, such as TP53 and p16(INK4). Other studies showed the dysregulation of the expression of proteins involved in the control of cell cycle, proliferation, apoptosis, and invasiveness, such as Bcl-2, Akt, mdm2, and epidermal growth factor receptor. These characteristics might contribute to the aggressive behavior of pancreatic cancer and influence response to treatment. Indeed, the inactivation of p53 may explain the relative resistance to 5-fluorouracil, whereas Bcl-2 overexpression is associated with reduced sensitivity to gemcitabine. However, the future challenge of pancreas cancer chemotherapy relies on the identification of molecular markers that help in the selection of drugs best suited to the individual patient. Recent pharmacogenetic studies focused on genes encoding proteins directly involved in drug activity, showing the role of thymidylate synthase and human equilibrative nucleoside transporter-1 as prognostic factor in 5-fluorouracil- and gemcitabine-treated patients, respectively. Finally, inhibitors of signal transduction and angiogenesis are under extensive investigation, and several prospective trials have been devoted to this area. Pharmacogenetics is likely to play a central role in the personalization of treatment, to stratify patients based on their likelihood of response to both standard agents (i.e., gemcitabine/nucleoside transporters) and targeted treatments (i.e., epidermal growth factor receptor gene mutations and/or amplification and tyrosine kinase inhibitors), Thus, molecular analysis should be implemented in the optimal management of the patient affected by pancreatic adenocarcinoma.

Transcription Analysis of Human Equilibrative Nucleoside Transporter-1 Predicts Survival in Pancreas Cancer Patients Treated with Gemcitabine

Gene expression analysis may help the management of cancer patients, allowing the selection of subjects responding to treatment. The aim of this study was the characterization of expression pattern of genes involved in gemcitabine activity in pancreas tumor specimens and its correlation with treatment outcome. The role of drug transport and metabolism on gemcitabine cytotoxicity was examined with specific inhibitors, whereas transcription analysis of human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (dCK), 5'-nucleotidase (5'-NT), cytidine deaminase (CDA), and ribonucleotide reductase subunits M1 and M2 (RRM1 and RRM2) was done by quantitative reverse transcription-PCR in tumor tissue isolated by laser microdissection from surgical or biopsy samples of 102 patients. Association between clinical outcome and gene expression levels was estimated using Kaplan-Meier method and Cox's proportional hazards model. Transport and metabolism had a key role on gemcitabine sensitivity in vitro; moreover, hENT1, dCK, 5'-NT, CDA, RRM1, and RRM2 were detectable in most tumor specimens. hENT1 expression was significantly correlated with clinical outcome. Patients with high levels of hENT1 had a significantly longer overall survival [median, 25.7; 95% confidence interval (95% CI), 17.6-33.7 months in the higher expression tertile versus median, 8.5; 95% CI, 7.0-9.9 months in the lower expression tertile]. Similar results were obtained with disease-free survival and time to disease progression, and the multivariate analysis confirmed the prognostic significance of hENT1. This study suggests that the expression levels of hENT1 may allow the stratification of patients based on their likelihood of survival, thus offering a potential new tool for treatment optimization.

Intraductal papillary mucinous neoplasms of the pancreas: A surgical perspective

Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas represent a relatively "new", but increasingly recognized entity. The emergence of this entity is due primarily to the widespread use of modern imaging methods, but also to a heightened awareness of physicians regarding this cystic neoplasm of the pancreas. No signs or symptoms are pathognomonic of IPMNs, but frequently, patients have a pancreatitis-like abdominal pain. Fully one-third of patients with IPMN are asymptomatic at the time of diagnosis. Cross-sectional imaging (ultrasonography, computed tomography, magnetic resonance cholangiopancreatography), endoscopic retrograde cholangiopancreatography, and endoscopic ultrasonography are the diagnostic and staging methods of choice in the evaluation of patients with IPMNs. IPMNs show a wide spectrum of histologic changes, ranging from adenoma to invasive neoplasm, even within the same neoplasm, suggesting a "field defect" predisposing major segments or even the entire ductal epithelium to the development of IPMN. Fine-needle aspiration/cytology and/or analysis of the cystic fluid may be useful diagnostic tools; however, these examinations are associated with high false-negative rates. Complete surgical resection is the therapeutic method of choice. The extent and type of pancreatectomy remain somewhat controversial but should be based on morphologic changes of the pancreas. Even the role of adjuvant therapy remains unclear; however, being "duct-derived" neoplasms of potential malignant character, some form of adjuvant chemo- or ratio-therapy seems indicated in the presence of invasive disease, despite a "curative" resection. In the absence of invasive disease, prognosis after R0 resection is highly favorable with recurrences of 5-10%. However, invasive IPMNs behave quite similar to ductal adenocarcinoma of the pancreas when analyzed stage-by-stage, with a slightly better prognosis; however, even after an R0 resection, recurrence is common.

Recent advances on the molecular mechanisms involved in pancreatic cancer progression and therapies

This review describes the recent advances in the molecular events involved in pancreatic cancer initiation, progression, and metastasis. Additionally, the importance of deregulated cellular signaling elements as potential targets for developing novel therapeutic strategies against incurable forms of pancreatic cancer is reported. The emphasis is on the critical functions gained by numerous growth factors and their receptors, such as epidermal growth factor receptor, hedgehog signaling, and proangiogenic agents such as vascular endothelial factor and interleukin-8 for the sustained growth, survival, and metastasis of pancreatic cancer cells. The molecular mechanisms associated with antitumoral properties and the clinical benefits of gemcitabine alone or in combination with other cytotoxic agents for the treatment of pancreatic cancer are discussed.

The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone stimulates proliferation of immortalized human pancreatic duct epithelia through beta-adrenergic transactivation of EGF receptors

PURPOSE

Pancreatic ductal adenocarcinoma is an aggressive smoking-associated human cancer in both men and women. The nicotine-derived 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is thought to contribute to the development of these neoplasms in smokers through genotoxic effects. However, NNK has been recently identified as an agonist for both beta(1)- and beta(2)-adrenergic receptors. Binding of NNK to these receptors stimulates proliferation of pulmonary and pancreatic adenocarcinomas cells in vitro and in hamster models. The goal of this study was to elucidate the NNK effects on the signal transduction pathways downstream of both beta(1)- and beta(2)-adrenergic receptors in immortalized human pancreatic HPDE6-c7 cells.

METHODS

The HPDE6-c7 cells are developed from normal pancreatic duct epithelial cells which are the putative cells of origin of pancreatic ductal adenocarcinoma. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cell proliferation assays, Western blot and cyclic AMP assays were employed to demonstrate the effects of NNK and other beta(1)- and beta(2)-adrenergic agonists and antagonist treatments on these cells.

RESULTS

MTT cell proliferation assays demonstrated that NNK and the classic beta-adrenergic agonist, isoproterenol, increased cell proliferation in HPDE6-c7 cells. Western blot and cyclic AMP assays demonstrated that NNK treatments also resulted in: (1) transactivation of the epidermal growth factor receptor, EGFR, (2) an increase in intracellular cyclic AMP accumulation, and (3) phosphorylation of mitogen-activated protein kinase, Erk1/2. The proliferative response to NNK and isoproterenol were inhibited by the use of beta-blockers (propranolol), and the inhibitors of adenylyl cyclase (SQ 22536), EGFR-specific tyrosine kinase (AG 1478) and Erk (PD 98059).

CONCLUSION

These findings suggest that the NNK -mediated beta-adrenergic receptor transactivation of the EGFR and phosphorylation of Erk1/2 in immortalized human pancreatic duct epithelial cells as a novel mechanism might contribute to the development of tobacco-associated pancreatic carcinogenesis.

Clinical significance of p16 protein expression loss and aberrant p53 protein expression in pancreatic cancer

Pancreatic cancer is a disease with poor prognosis mainly due to low resection rates and late diagnosis. To increase resectability and improve survival rates, a better understanding of pancreatic cancer pathogenesis and more effective screening techniques are required. New methods, such as genetic and molecular alterations, may suggest novel approaches for pancreatic cancer diagnosis and treatment. We immunohistochemically investigated 44 formalin-fixed, paraffin-embedded specimens of pancreatic ductal adenocarcinoma using monoclonal anti-p16 antibodies and monoclonal anti-p53 antibodies. The expressions of p16 and p53 proteins were compared using the Chi-square test with SPSS. Disease-free survival was analyzed using the Kaplan-Meier method, verified by the Log- Rank test. Loss of p16 expression was noted in 20 (45.5%) cases and aberrant p53 protein expression was detected in 14 (31.8%) cases. Loss of p16 expression was associated with a higher incidence of lymph node metastasis (p=0.040) and a more advanced stage (p=0.015), although there was no significant correlation between p16 expression and survival. Aberrant p53 protein expression correlated with histologic grade (p= 0.038). Disease-free survival rate was significantly lower in the aberrant p53 protein positive group compared to the negative group (p=0.029). From our results, we suggest that p53 is not a prognostic factor; however, p16 and p53 genes do play important roles in the progression of pancreatic ductal adenocarcinoma.

Diagnosis of pancreatic cancer using serum proteomic profiling

In the United States, mortality rates from pancreatic cancer (PCa) have not changed significantly over the past 50 years. This is due, in part, to the lack of early detection methods for this particularly aggressive form of cancer. The objective of this study was to use high-throughput protein profiling technology to identify biomarkers in the serum proteome for the early detection of resectable PCa. Using surface-enhanced laser desorption/ionization mass spectrometry, protein profiles were generated from sera of 49 PCa patients and 54 unaffected individuals after fractionation on an anion exchange resin. The samples were randomly divided into a training set (69 samples) and test set (34 samples), and two multivariate analysis procedures, classification and regression tree and logistic regression, were used to develop classification models from these spectral data that could distinguish PCa from control serum samples. In the test set, both models correctly classified all of the PCa patient serum samples (100% sensitivity). Using the decision tree algorithm, a specificity of 93.5% was obtained, whereas the logistic regression model produced a specificity of 100%. These results suggest that high-throughput proteomics profiling has the capacity to provide new biomarkers for the early detection and diagnosis of PCa.

Detection of Ki-ras mutations in tissue and plasma samples of patients with pancreatic cancer using PNA-mediated PCR clamping and hybridisation probes

In the present study, we combined the PCR-clamping approach with melting curve analysis using mutant specific hybridisation probes and wild-type specific peptide nucleic acids (PNAs) to determine the genotypes of the most frequent point mutation in codon 12 of the proto-oncogene Ki-ras in tissue and plasma samples of patients with pancreatic cancer. The sensitivity of our assay was 1–5 × 10⁻⁵. The melting curve analysis of tissue samples of four patients revealed two valine mutations, one none-valine mutation and one wild-type sequence. Ki-ras alterations were found in 28% of DNAs (18 out of 64) of nonrelated plasma samples of 10 patients with ductal adenocarcinoma of the pancreas. The valine mutation was the predominantly detected gene alteration (83%). Out of ten patients investigated, four patients (40%) became positive during clinical observation with respect to Ki-ras mutation. All four patients exhibited progressive disease and high levels of tumour marker CA 19-9. In conclusion, the one-step procedure discribed may be a useful clinical tool for analysing Ki-ras point mutations in tissue and plasmas samples. In addition, this method can be adapted for simultanous detection of multiple mutations and quantitation.

Intraperitoneal injection of adenovirus expressing antisense K-ras RNA suppresses peritoneal dissemination of hamster syngeneic pancreatic cancer without systemic toxicity

We examined the antitumor effect and safety of the adenovirus-mediated expression of antisense K-ras RNA in two peritoneal dissemination models of pancreatic cancer. First, we found that the infection of an adenovirus vector expressing antisense human K-ras RNA (AxCA-AS) induced significant apoptosis in vitro in human pancreatic cancer cells with K-ras mutation. Second, the intraperitoneal (ip) injection of AxCA-AS effectively suppressed the growth of human pancreatic cancer cells in the peritoneal cavity of nude mice. Third, in the hamster syngeneic peritoneal dissemination model, the ip injection of an adenovirus expressing antisense hamster K-ras RNA significantly suppressed the peritoneal growth of hamster pancreatic cancer cells, and no significant systemic toxicity was observed in the treated hamsters. This study suggests a feasibility of the development of a therapeutic strategy against pancreatic cancer based on the adenovirus-mediated transduction of an antisense K-ras construct.

Towards a model for the inhibition of choline kinase by a new type of inhibitor

Bispyridinium cyclophanes are novel templates for human choline kinase inhibitors. Molecular modelling of these compounds suggests three anchorage places at the binding site of the enzyme: (i) two anionic centres of the enzyme active site separated from each other at a distance of approximately 6.2 A that bind the two positively charged nitrogen atoms; (ii) a wide hydrophobic pocket that is fulfilled by the upper linker, the benzene ring that links the two amino groups; and (iii) a smaller hydrophobic pocket that can accommodate the lower benzene ring that links both benzylic carbons. This study may be useful for the development of more potent inhibitors of the enzyme.

A role for human MUC4 mucin gene, the ErbB2 ligand, as a target of TGF-beta in pancreatic carcinogenesis

MUC4: encodes a large transmembrane mucin that is overexpressed in pancreatic adenocarcinomas. The molecular mechanisms responsible for that altered pattern of expression are unknown. TGF-beta, a pleiotropic cytokine, regulates numerous genes involved in pancreatic carcinogenesis via activation of the Smads proteins and MUC4 promoter is rich in Smad-binding elements. Our aim was to study whether the regulation of MUC4 expression by TGF-beta in pancreatic cancer cells was strictly dependent on Smad4 activity. Three pancreatic cancer cell lines, CAPAN-1 (MUC4+/Smad4-), CAPAN-2 (MUC4+/Smad4+) and PANC-1 (MUC4-/Smad4+), were used. By RT-PCR, transfection assays and immunohistochemistry, we show that (i) both MUC4 mRNA and apomucin expression are upregulated by TGF-beta, (ii) Smad2 positively cooperates with Smad4 to activate the promoter, (iii) activation of Smad4 by exogenous TGF-beta induces Smad4 binding to the promoter, (iv) Smad7 and c-ski both inhibit activation by Smad4. When Smad4 is mutated and inactive, TGF-beta activates MUC4 expression via MAPK, PI3K and PKA signaling pathways. Absence of expression in PANC-1 cells is due to histone deacetylation. Altogether, these results indicate that upregulation of MUC4 by TGF-beta is restricted to well-differentiated pancreatic cancer cells, and point out a novel mechanism for TGF-beta as a key molecule in targeting MUC4 overexpression in pancreatic adenocarcinomas.

Development of gene therapy to target pancreatic cancer

Pancreatic cancer remains one of the most difficult cancers to treat. Its high propensity to infiltrate and metastasize early from a small primary focus necessitates development of a new therapy which can track down the disseminated cancer cells in vivo. Gene therapy may offer new opportunities for a variety of targeting strategies, and we review here some of our work related to the development of targeted gene therapy: 1) Targeting by specific molecular abnormality: Many pancreatic cancer cells show "addiction" to K-ras mutation, while normal cells appear resistant to suppression of K-ras-mediated signaling by antisense K-ras RNA expression adenoviral vector. 2) Targeting by in vivo tumor characteristics: In a peritoneal dissemination model, intraperitoneal lipofection/polyfection can deliver and express transgenes highly preferentially in tumor nodules. 3) Targeting by vector: An efficient protocol for construction of an adenovirus expression vector library has been developed, which will enable a direct functional selection of fiber knob-modified targeting vector species for given cells. 4) Targeting by tumor immunity: Several cytokines not only induce direct cytotoxicity, but are also expected to activate specific immunity to achieve targeted suppression of cancer cells in vivo. Unlike parenteral administration of short-lived recombinant interferon protein, local interferon gene transfer can provide a target tissue-restricted distribution and sustained expression, which may improve the efficacy/safety balance of cytokine therapy. Cancer gene therapy development is, in general, at the stage of proof of principles and safety. However, it is an art of integrated science. The recent rapid progress of related sciences and technologies will expand the potential and consolidate the clinical reality of gene therapy.

Fundamentals of transcription factors and their impact on pancreatic development and cancer

Transcription factors are proteins that regulate gene expression by modulating the synthesis of messenger RNA. Since this process, known as gene transcription, is often the dominant control point in the production of many proteins, transcription factors are key regulators of numerous cellular functions, including secretion, proliferation, differentiation, and apoptosis. Most transcription factors are also the final effectors of signaling pathways that transduce signals from the cell membrane to the nucleus. Therefore alterations in the activity or expression of some transcription factors have a significant impact on the biology of human cells and may lead to the development of diseases. In this article we review this field of research with a particular emphasis on the role of transcription factors in pancreatic development and cancer.

Leucine-zipper protein, LDOC1, inhibits NF-kappaB activation and sensitizes pancreatic cancer cells to apoptosis

We have isolated a novel gene, LDOC1, which encodes for a leucine zipper protein that was downregulated in a series of human pancreatic cancer cell lines but was expressed in corresponding normal tissues. We report the initial characterization of LDOC1 as a novel regulator of the transcriptional response mediated by the nuclear factor kappa B (NF-kappaB). Transient expression of LDOC1 significantly inhibited the luciferase activity in LDOC1-negative BxPC-3 pancreatic cancer cell line transfected with the NF-kappaB reporter plasmid, activated with mitogen-activated protein kinase/ERK kinase kinase-1 (MEEK). LDOC1, however, does not affect p53, AP1 and CRE-dependent reporter gene expression. The activation of NF-kappaB through ligand-induced stimulation by tumor necrosis factor-alpha (TNF-alpha) or phorbol 12-myristate 13-acetate (PMA) was also inhibited by transient expression of LDOC1 in a dose dependent manner. To determine the growth effect of LDOC1 expression on cancer cells, BxPC-3 cells were stably transfected with LDOC1 cDNA. Viability studies demonstrated that TNF-alpha or PMA-induced antiproliferative effects were significantly enhanced by stable transfection of cells with LDOC1. These observations suggest that LDOC1 is a novel regulator of NF-kappaB that can affect the PMA or TNF-alpha-mediated pathway to apoptosis through inhibition of NF-kappaB activation in BxPC3 pancreatic cancer cells.

Restoration of silenced Peutz-Jeghers syndrome gene, LKB1, induces apoptosis in pancreatic carcinoma cells

Germ line mutations of the LKB1 tumor suppressor gene lead to Peutz-Jeghers syndrome (PJS) with a predisposition to cancer. Previous reports suggest that inactivation of this tumor-suppressor gene plays a role in the pathogenesis of gastrointestinal hamartomas as well as several cancers, including adenocarcinoma of the pancreas. Here, we have shown that LKB1 gene is silenced in the pancreatic cancer cell line AsPC-1, but can be recovered by treatment with the methylation inhibitor, 5-aza-2'-deoxycytidine (5aza2dC). Restoring the level of LKB1 through gene transfer initiated mitochondria-mediated apoptosis in AsPC-1 cells, as evidenced by the release of cytochrome c from the mitochondria. By confocal microscopy as well as biochemical fractionation, we demonstrate that LKB1 is present in the nuclear and mitochondrial compartments of pancreatic cancer cells. Our observations also indicate that although functional p53 is absent, the p53 kin, p73, is inducible by doxorubicin in AsPC-1 cells. This suggests that LKB1-induced apoptosis is p53 independent but might be p73-mediated in the pancreatic tumor cell line, AsPC-1.

Biotherapeutic approaches to pancreatic cancer

The incidence of adenocarcinoma of the pancreas has risen steadily over the past four decades. Since pancreatic cancer is usually diagnosed at an advanced stage and because of the lack of effective therapies, the prognosis of such patients is extremely poor. Despite advances in our understanding of the molecular biology of pancreatic cancer, the systemic treatment of this disease remains unsatisfactory. Conventional chemotherapy has not produced dramatic improvements in response rates or patient survival. New treatment strategies are clearly needed. This paper will review emerging therapies for pancreatic carcinoma. A deeper understanding of the molecular biology of cell growth and proliferation, as well as of neoplastic cell transformation, has led to advances in several areas, including the use of hormones and antihormones as adjuvant therapy; inhibition of tumour growth and metastasis by inhibitors of matrix metalloproteases and angiogenesis, and by small molecules, such as retinoids, which interfere with progression through the cell cycle; immunotherapy with monoclonal antibodies; disruption of intracellular signal transduction with farnesyltransferase inhibitors; and, finally, gene therapy with specifically designed vaccines.

Current approaches to novel therapeutics in pancreatic cancer

Pancreatic cancer is one of the most refractory neoplasms to medical treatment. Until now there has been only modest improvement in the treatment of this disease. Standards of care for combined-modality treatment of resectable as well as locally advanced, unresectable disease have not been uniformly accepted to date because of an equivocal or conflicting data. The inception of gemcitabine introduced the new era in the management of metastatic pancreatic cancer, however, new therapeutic approaches still need to be defined. The article discusses the current knowledge of the biology of this lethal disease, its impact on treatment options, and explores novel therapeutic modalities that are likely to improve outcomes and survival for patients in the future.

Nerve growth factor and enhancement of proliferation, invasion, and tumorigenicity of pancreatic cancer cells

Nerve growth factor (NGF) exerts both stimulatory and inhibitory effects on neuronal and certain non-neuronal tumors. In pancreatic cancer NGF is overexpressed, and this overexpression is associated with increased perineural invasion. NGF has the potential to stimulate the growth of some pancreatic cancer cell lines, and this effect is mediated by the phosphorylation of tyrosine kinase receptor A and mitogen-activated protein kinase activation; it is dependent on the expression levels of tyrosine kinase receptor A and p75 receptors. To determine whether cancer cell-derived NGF can participate in the regulation of pancreatic cancer cell proliferation, PANC-1 human pancreatic cancer cells were stably transfected with a full-length human beta-NGF expression vector. In vitro and in vivo growth characteristics were analyzed by proliferation assays and invasion assays and in a nude mouse tumor model. Stable transfection of NGF in PANC-1 cells resulted in enhanced anchorage-dependent growth, with a decrease in doubling times of up to 50%, and in an approximately twofold increase in anchorage-independent cell growth and cell invasion. Furthermore, stably transfected PANC-1 cells showed enhanced tumorigenicity in nude mice. These results suggest that NGF has the capacity to act in a paracrine and/or an autocrine manner in pancreatic cancer and that it enhances cancer cell growth and invasion in vivo, thereby contributing to the aggressiveness and poor prognosis of this disease.

Gene therapy for pancreatic cancer

Gene transfer technology has the potential to revolutionize cancer treatment. Developments in molecular biology, genetics, genomics, stem cell technology, virology, bioengineering, and immunology are accelerating the pace of innovation and movement from the laboratory bench to the clinical arena. Pancreatic adenocarcinoma, with its particularly poor prognosis and lack of effective traditional therapy for most patients, is an area where gene transfer and immunotherapy have a maximal opportunity to demonstrate efficacy. In this review, we have discussed current preclinical and clinical investigation of gene transfer technology for pancreatic cancer. We have emphasized that the many strategies under investigation for cancer gene therapy can be classified into two major categories. The first category of therapies rely on the transduction of cells other than tumor cells, or the limited transduction of tumor tissue. These therapies, which do not require efficient gene transfer, generally lead to systemic biological effects (e.g., systemic antitumor immunity, inhibition of tumor angiogenesis, etc) and therefore the effects of limited gene transfer are biologically "amplified." The second category of gene transfer strategies requires the delivery of therapeutic genetic material to all or most tumor cells. While these elegant approaches are based on state-of-the-art advances in our understanding of the molecular biology of cancer, they suffer from the current inadequacies of gene transfer technology. At least in the short term, it is very likely that success in pancreatic cancer gene therapy will involve therapies that require only the limited transduction of cells. The time-worn surgical maxim, "Do what's easy first," certainly applies here.