The genetics of pancreatic cancer

Cultures derived from pancreatic cancer xenografts with long-term gemcitabine treatment produce chemoresistant secondary xenografts: Establishment of isogenic gemcitabine-sensitive and -resistant models

In attempts to establish sophisticated models to reproduce the process of acquired drug resistance, we transformed normal human pancreatic ductal epithelial cells by introducing genes for multiple cellular factors. We also created isogenic gemcitabine-sensitive and -resistant models by short- and long-term gemcitabine treatment, respectively. These models demonstrated differences in drug resistance in vivo, but not in vitro. Gemcitabine treatment also induced squamous transdifferentiation in xenografts in mice. The transcription factor p63 was identified as a possible resistance-determining factor but was unlikely to be solely responsible for the resistance to gemcitabine. This system would prove useful to discover novel molecular targets to overcome chemotherapy resistance, by allowing the evaluation of molecules of interest in xenograft models after in vitro genetic ablation.

Acquired and intrinsic gemcitabine resistance in pancreatic cancer therapy: Environmental factors, molecular profile and drug/nanotherapeutic approaches

A high number of cancer patients around the world rely on gemcitabine (GEM) for chemotherapy. During local metastasis of cancers, surgery is beneficial for therapy, but dissemination in distant organs leads to using chemotherapy alone or in combination with surgery to prevent cancer recurrence. Therapy failure can be observed as a result of GEM resistance, threatening life of pancreatic cancer (PC) patients. The mortality and morbidity of PC in contrast to other tumors are increasing. GEM chemotherapy is widely utilized for PC suppression, but resistance has encountered its therapeutic impacts. The purpose of current review is to bring a broad concept about role of biological mechanisms and pathways in the development of GEM resistance in PC and then, therapeutic strategies based on using drugs or nanostructures for overcoming chemoresistance. Dysregulation of the epigenetic factors especially non-coding RNA transcripts can cause development of GEM resistance in PC and miRNA transfection or using genetic tools such as siRNA for modulating expression level of these factors for changing GEM resistance are suggested. The overexpression of anti-apoptotic proteins and survival genes can contribute to GEM resistance in PC. Moreover, supportive autophagy inhibits apoptosis and stimulates GEM resistance in PC cells. Increase in metabolism, glycolysis induction and epithelial-mesenchymal transition (EMT) stimulation are considered as other factors participating in GEM resistance in PC. Drugs can suppress tumorigenesis in PC and inhibit survival factors and pathways in increasing GEM sensitivity in PC. More importantly, nanoparticles can increase pharmacokinetic profile of GEM and promote its blood circulation and accumulation in cancer site. Nanoparticles mediate delivery of GEM with genes and drugs to suppress tumorigenesis in PC and increase drug sensitivity. The basic research displays significant connection among dysregulated pathways and GEM resistance, but the lack of clinical application is a drawback that can be responded in future.

Target c-Myc to treat pancreatic cancer

C-Myc overexpression is a common finding in pancreatic cancer and predicts the aggressive behavior of cancer cells. It binds to the promoter of different genes, thereby regulating their transcription. C-Myc is downstream of KRAS and interacts with several oncogenic and proliferative pathways in pancreatic cancer. C-Myc enhances aerobic glycolysis in cancer cells and regulates glutamate biosynthesis from glutamine. It provides enough energy for cancer cells' metabolism and sufficient substrate for the synthesis of organic molecules. C-Myc overexpression is associated with chemoresistance, intra-tumor angiogenesis, epithelial-mesenchymal transition (EMT), and metastasis in pancreatic cancer. Despite its title, c-Myc is not "undruggable" and recent studies unveiled that it can be targeted, directly or indirectly. Small molecules that accelerate c-Myc ubiquitination and degradation have been effective in preclinical studies. Small molecules that hinder c-Myc-MAX heterodimerization or c-Myc/MAX/DNA complex formation can functionally inhibit c-Myc. In addition, c-Myc can be targeted through transcriptional, post-transcriptional, and translational modifications.

Recent nanotechnology advancements to treat multidrug-resistance pancreatic cancer: Pre-clinical and clinical overview

Pancreatic cancer (PC) remains one of the most lethal and incurable forms of cancer and has a poor prognosis. One of the significant therapeutic challenges in PC is multidrug resistance (MDR), a phenomenon in which cancer cells develop resistance toward administered therapy. Development of novel therapeutic platforms that could overcome MDR in PC is crucial for improving therapeutic outcomes. Nanotechnology is emerging as a promising tool to enhance drug efficacy and minimize off-target responses via passive and/or active targeting mechanisms. Over the past decade, tremendous efforts have been made to utilize nanocarriers capable of targeting PC cells while minimizing off-target effects. In this review article, we first give an overview of PC and the major molecular mechanisms of MDR, and then we discuss recent advancements in the development of nanocarriers used to overcome PC drug resistance. In doing so, we explore the developmental stages of this research in both pre-clinical and clinical settings. Lastly, we discuss current challenges and gaps in the literature as well as potential future directions in the field.

Autophagy: A Key Player in Pancreatic Cancer Progression and a Potential Drug Target

Pancreatic cancer is known to have the lowest survival outcomes among all major cancers, and unfortunately, this has only been marginally improved over last four decades. The innate characteristics of pancreatic cancer include an aggressive and fast-growing nature from powerful driver mutations, a highly defensive tumor microenvironment and the upregulation of advantageous survival pathways such as autophagy. Autophagy involves targeted degradation of proteins and organelles to provide a secondary source of cellular supplies to maintain cell growth. Elevated autophagic activity in pancreatic cancer is recognized as a major survival pathway as it provides a plethora of support for tumors by supplying vital resources, maintaining tumour survival under the stressful microenvironment and promoting other pathways involved in tumour progression and metastasis. The combination of these features is unique to pancreatic cancer and present significant resistance to chemotherapeutic strategies, thus, indicating a need for further investigation into therapies targeting this crucial pathway. This review will outline the autophagy pathway and its regulation, in addition to the genetic landscape and tumor microenvironment that contribute to pancreatic cancer severity. Moreover, this review will also discuss the mechanisms of novel therapeutic strategies that inhibit autophagy and how they could be used to suppress tumor progression.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

Prognostic Factors of Survival in Pancreatic Cancer Metastasis to Liver at Different Ages of Diagnosis: A SEER Population-Based Cohort Study

Background: Liver is a common metastatic organ for most malignancies, especially the pancreas. However, evidence for prognostic factors of pancreatic cancer metastasis to the liver at different ages is lacking. Thus, we aimed to evaluate the predictors of patients with pancreatic cancer metastasis to liver grouped by age of diagnosis.

Methods: We chose the patients diagnosed between 2004 and 2015 from the SEER database. The primary lesions of metastatic liver cancer between sexes were compared using the Pearson’s chi-square test for categorical variables. The overall survival (OS) and cancer-specific survival (CSS) were the endpoint of the study. The prognostic factors were analyzed with the Kaplan-Meier method and log-rank test, and Cox proportional-hazards regression model.

Results: The main primary sites of metastatic liver cancer for our patients are lung and brunchu, sigmoid colon, pancreas, which in males are lung and bronchu, sigmoid colon and pancreas, while breast, lung and bronchu, sigmoid colon in females. Furthermore, we explored the prognostic factors of pancreatic cancer metastasis to liver grouped by age at diagnosis. Tumor grade, histology and treatment are valid prognostic factors in all age groups. Additionally, gender and AJCC N stage in age<52 years old, while race and AJCC N stage in age >69 years old were predictors. Surgery alone was the optimal treatment in group age>69 years old, whereas surgery combined with chemotherapy was the best option in the other groups.

Conclusion: Our study evaluated the predictors of patients with pancreatic cancer metastasis to liver at various ages of diagnosis.

Metastasis Suppressor Genes in Pancreatic Cancer: An Update

ABSTRACT

Pancreatic cancer, especially pancreatic ductal adenocarcinoma (PDAC), has for long remained a deadly form of cancer characterized by high mortality rates resulting from metastasis to multiple organs. Several factors, including the late manifestation of the disease, partly amplified by lack of efficient screening methods, have hampered the drive to design an effective therapeutic strategy to treat this deadly cancer. Understanding the biology of PDAC progression and identifying critical genes regulating these processes are essential to overcome the barriers toward effective treatment. Metastasis suppressor genes have been shown to inhibit multiple steps in the metastatic cascade without affecting primary tumor formation and are considered to hold promise for treating metastatic cancers. In this review, we catalog the bona fide metastasis suppressor genes reported in PDAC and discuss their known mechanism of action.

MicroRNAs as biomarkers and perspectives in the therapy of pancreatic cancer

Pancreatic cancer is considered as one of the most aggressive tumor types, representing over 45,750 mortality cases annually in the USA solely. The aggressive nature and late identification of pancreatic cancer, combined with the restrictions of existing chemotherapeutics, present the mandatory need for the advancement of novel treatment systems. Ongoing reports have shown an important role of microRNAs (miRNAs) in the initiation, migration, and metastasis of malignancies. Besides, abnormal transcriptional levels of miRNAs have regularly been related with etiopathogenesis of pancreatic malignancy, underlining the conceivable utilization of miRNAs in the management of pancreatic disease patients. In this review article, we give a concise outline of molecular pathways involved in etiopathogenesis of pancreatic cancer patients as well as miRNA implications in pancreatic cancer patients. Ensuing sections describe the involvement of miRNAs in the diagnosis, prognosis, and therapy of pancreatic cancer patients. The involvement of miRNAs in the chemoresistance of pancreatic cancers was also discussed. End area portrays the substance of survey with future headings.

Identification of potential diagnostic biomarkers in MMPs for pancreatic carcinoma

Pancreatic cancer (PC) is a malignant tumor which ranks fourth in cancer-related death. However, the specificity and sensitivity of traditional biomarkers such as carbohydrate antigen 19-9 no longer meet the clinical requirements.Tools as ONCOMINE and Gene Expression Profiling Interactive Analysis (GEPIA) were used to analyze the differential expression of matrix metalloproteinases (MMPs) in PC and adjacent tissues. For further analysis, we adopted database for annotation, visualization and integrated discovery (DAVID 6.8), transcriptional regulatory relationships unraveled by sentence-based text (TRRUST) and other tools. We also identified drugs targeted the selected MMPs.Eight MMPs (MMP1, MMP2, MMP7, MMP9, MMP11, MMP12, MMP14, and MMP28) were differentially expressed in PC and adjacent tissue. MMP1 (P = .0189), MMP7 (P = .000216), MMP11 (P = .0209), MMP14 (P = .00611) were correlated with the pathological stages of PC. Patients with higher expression of MMP1 (P = .0011), MMP2 (P = .011), MMP7 (P = .0081), MMP9 (P = .046), MMP11 (P = .0019), MMP12 (P = .0011), MMP14 (P = .0011), and MMP28 (P = 6.3e-06) showed poor prognosis. Ten transcription factors were associated with the up-regulation of selected MMPs. Marimastat (DB00786) was found to target selected MMPs.Our research revealed that selected MMPs played an important role in the early diagnosis and prognosis of PC.

Advances in oncolytic adenovirus therapy for pancreatic cancer

Survival rates for pancreatic cancer patients have remained unchanged for the last four decades. The most aggressive, and most common, type of pancreatic cancer is pancreatic ductal adenocarcinoma (PDAC), which has the lowest 5-year survival rate of all cancers globally. The poor prognosis is typically due to late presentation of often non-specific symptoms and rapid development of resistance to all current therapeutics, including the standard-of-care cytotoxic drug gemcitabine. While early surgical intervention can significantly prolong patient survival, there are few treatment options for late-stage non-resectable metastatic disease, resulting in mostly palliative care. In addition, a defining feature of pancreatic cancer is the immunosuppressive and impenetrable desmoplastic stroma that blocks access to tumour cells by therapeutic drugs. The limited effectiveness of conventional chemotherapeutics reveals an urgent need to develop novel therapies with different mechanisms of action for this malignancy. An emerging alternative to current therapeutics is oncolytic adenoviruses; these engineered biological agents have proven efficacy and tumour-selectivity in preclinical pancreatic cancer models, including models of drug-resistant cancer. Safety of oncolytic adenoviral mutants has been extensively assessed in clinical trials with only limited toxicity to normal healthy tissue being reported. Promising efficacy in combination with gemcitabine was demonstrated in preclinical and clinical studies. A recent surge in novel adenoviral mutants entering clinical trials for pancreatic cancer indicates improved efficacy through activation of the host anti-tumour responses. The potential for adenoviruses to synergise with chemotherapeutics, activate anti-tumour immune responses, and contribute to stromal dissemination render these mutants highly attractive candidates for improved patient outcomes. Currently, momentum is gathering towards the development of systemically-deliverable mutants that are able to overcome anti-viral host immune responses, erythrocyte binding and hepatic uptake, to promote elimination of primary and metastatic lesions. This review will cover the key components of pancreatic cancer oncogenesis; novel oncolytic adenoviruses; clinical trials; and the current progress in overcoming the challenges of systemic delivery.

Preclinical development of G1T38: A novel, potent and selective inhibitor of cyclin dependent kinases 4/6 for use as an oral antineoplastic in patients with CDK4/6 sensitive tumors

Inhibition of the p16^INK4a/cyclin D/CDK4/6/RB pathway is an effective therapeutic strategy for the treatment of estrogen receptor positive (ER⁺) breast cancer. Although efficacious, current treatment regimens require a dosing holiday due to severe neutropenia potentially leading to an increased risk of infections, as well as tumor regrowth and emergence of drug resistance. Therefore, a next generation CDK4/6 inhibitor that can inhibit proliferation of CDK4/6-dependent tumors while minimizing neutropenia could reduce both the need for treatment holidays and the risk of inducing drug resistance.

Here, we describe the preclinical characterization and development of G1T38; a novel, potent, selective, and orally bioavailable CDK4/6 inhibitor. In vitro, G1T38 decreased RB1 (RB) phosphorylation, caused a precise G1 arrest, and inhibited cell proliferation in a variety of CDK4/6-dependent tumorigenic cell lines including breast, melanoma, leukemia, and lymphoma cells. In vivo, G1T38 treatment led to equivalent or improved tumor efficacy compared to the first-in-class CDK4/6 inhibitor, palbociclib, in an ER⁺ breast cancer xenograft model. Furthermore, G1T38 accumulated in mouse xenograft tumors but not plasma, resulting in less inhibition of mouse myeloid progenitors than after palbociclib treatment. In larger mammals, this difference in pharmacokinetics allowed for 28 day continuous dosing of G1T38 in beagle dogs without producing severe neutropenia. These data demonstrate G1T38 has unique pharmacokinetic and pharmacodynamic properties, which result in high efficacy against CDK4/6 dependent tumors while minimizing the undesirable on-target bone marrow activity, thus potentially allowing G1T38 to be used as a continuous, daily oral antineoplastic agent.

Advances in Molecular Profiling and Categorisation of Pancreatic Adenocarcinoma and the Implications for Therapy

Pancreatic ductal adenocarcinoma (PDAC) continues to be a disease with poor outcomes and short-lived treatment responses. New information is emerging from genome sequencing identifying potential subgroups based on somatic and germline mutations. A variety of different mutations and mutational signatures have been identified; the driver mutation in around 93% of PDAC is KRAS, with other recorded alterations being SMAD4 and CDKN2A. Mutations in the deoxyribonucleic acid (DNA) damage repair pathway have also been investigated in PDAC and multiple clinical trials are ongoing with DNA-damaging agents. Rare mutations in BRAF and microsatellite instability (MSI) have been reported in about 1-3% of patients with PDAC, and agents used in other cancers to target these have also shown some promise. Immunotherapy is a developing field, but has failed to demonstrate benefits in PDAC to date. While many trials have failed to improve outcomes in this deadly disease, there is optimism that by developing a better understanding of the translational aspects of this cancer, future informed therapeutic strategies may prove more successful.

Does Mutated K-RAS Oncogene Attenuate the Effect of Sulindac in Colon Cancer Chemoprevention?

The NSAID sulindac has been successfully used alone or in combination with other agents to suppress colon tumorigenesis in patients with genetic predisposition and also showed its efficacy in prevention of sporadic colon adenomas. At the same time, some experimental and clinical reports suggest that a mutant K-RAS oncogene may negate sulindac antitumor efficacy. To directly assess sulindac activity at suppressing premalignant lesions carrying K-RAS mutation, we utilized a novel mouse model with an inducible colon-specific expression of the mutant K-ras oncogene (K-ras^G12D ). Tumor development and treatment effects were monitored by minimally invasive endoscopic Optical coherence tomography. Expression of the mutant K-ras allele accelerated azoxymethane (AOM)-induced colon carcinogenesis in C57BL/6 mice, a strain otherwise resistant to this carcinogen. Sulindac completely prevented AOM-induced tumor formation in K-ras wild-type (K-ras wt) animals. In K-ras^G12D -mutant mice, a 38% reduction in tumor number, an 83% reduction in tumor volume (P ≤ 0.01) and an increase in the number of adenoma-free mice (P = 0.04) were observed. The partial response of K-Ras^G12D animals to sulindac treatment was evident by the decrease in mucosal thickness (P < 0.01) and delay in progression of the precancerous aberrant crypt foci to adenomas. Molecular analyses showed significant induction in cyclooxygenase 2 (COX-2), cleaved caspase-3 (CC3), and Ki-67 expression by AOM, but not sulindac treatment, in all genotypes. Our data underscore the importance of screening for K-RAS mutations in individuals with colon polyps to provide more personalized interventions targeting mutant K-RAS signaling pathways. Cancer Prev Res; 11(1); 16-26. ©2017 AACR.

Germline mutations in pancreatic cancer and potential new therapeutic options

Due to short-lived treatment responses in unresectable disease, pancreatic ductal adenocarcinoma (PDAC) continues to be one of the deadliest cancers. There is availability of new information about germline and sporadic mutations in the deoxyribonucleic acid (DNA) damage repair pathway in PDAC in recent decades and the expectation is that novel targeted therapies will thus be developed. A variety of germline mutations (BRCA2, BRCA1, PALB2, CDKN2A, ATM, TP53 and mismatch repair genes MLH1, MSH2, MSH6) have been reported in these patients with the highest prevalence being BRCA1/2. Positive results have been reported with the use of targeted therapies, particularly poly (ADP-ribose) polymerase inhibitors in BRCA-mutated ovarian and breast cancers, and their use is currently being investigated in germline-mutated pancreatic cancer. The aim of this review is to provide an outline of germline DNA damage repair mutations in pancreatic cancer and their effect on the incidence, outcomes and responses to different therapeutic options.

Targeting reactive nitrogen species suppresses hereditary pancreatic cancer

Germline mutation of BRCA2 induces hereditary pancreatic cancer. However, how BRCA2 mutation specifically induces pancreatic tumorigenesis remains elusive. Here, we have examined a mouse model of Brca2-deficiency-induced pancreatic tumors and found that excessive reactive nitrogen species (RNS), such as nitrite, are generated in precancerous pancreases, which induce massive DNA damage, including DNA double-strand breaks. RNS-induced DNA lesions cause genomic instability in the absence of Brca2. Moreover, with the treatment of antioxidant tempol to suppress RNS, not only are DNA lesions significantly reduced, but also the onset of pancreatic cancer is delayed. Thus, this study demonstrates that excess RNS are a nongenetic driving force for Brca2-deficiency-induced pancreatic tumors. Suppression of RNS could be an important strategy for pancreatic cancer prevention.

Proteomic strategies in the search for novel pancreatic cancer biomarkers and drug targets: recent advances and clinical impact

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers; despite a low incidence rate it is the fourth leading cause of cancer-related death in the world. Improvement of the diagnosis, prognosis and treatment remains the main focus of pancreatic cancer research. Rapid developments in proteomic technologies has improved our understanding of the pancreatic cancer proteome. Here, the authors summarise the recent proteomic strategies undertaken in the search for: novel biomarkers for early diagnosis, pancreatic cancer-specific proteins which may be used for novel targeted therapies and proteins which may be useful for monitoring disease progression post-therapy. Recent advances and findings discussed here provide great promise of having a significant clinical impact and improving the outcome of patients with this malignancy.

Effects of mutations in Wnt/β-catenin, hedgehog, Notch and PI3K pathways on GSK-3 activity-Diverse effects on cell growth, metabolism and cancer

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that participates in an array of critical cellular processes. GSK-3 was first characterized as an enzyme that phosphorylated and inactivated glycogen synthase. However, subsequent studies have revealed that this moon-lighting protein is involved in numerous signaling pathways that regulate not only metabolism but also have roles in: apoptosis, cell cycle progression, cell renewal, differentiation, embryogenesis, migration, regulation of gene transcription, stem cell biology and survival. In this review, we will discuss the roles that GSK-3 plays in various diseases as well as how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTOR, Ras/Raf/MEK/ERK, Wnt/beta-catenin, hedgehog, Notch and TP53. Mutations that occur in these and other pathways can alter the effects that natural GSK-3 activity has on regulating these signaling circuits that can lead to cancer as well as other diseases. The novel roles that microRNAs play in regulation of the effects of GSK-3 will also be evaluated. Targeting GSK-3 and these other pathways may improve therapy and overcome therapeutic resistance.

miRNAs in pancreatic cancer: therapeutic potential, delivery challenges and strategies

Pancreatic ductal adenocarcinoma (PDAC) is a severe pancreatic malignancy and is predicted to victimize 1.5% of men and women during their lifetime (Cancer statistics: SEER stat fact sheet, National Cancer Institute, 2014). miRNAs have emerged as a promising prognostic, diagnostic and therapeutic tool to fight against pancreatic cancer. miRNAs could modulate gene expression by imperfect base-pairing with target mRNA and hence provide means to fine-tune multiple genes simultaneously and alter various signaling pathways associated with the disease. This exceptional miRNA feature has provided a paradigm shift from the conventional one drug one target concept to one drug multiple target theory. However, in vivo miRNA delivery is not fully realized due to challenges posed by this special class of therapeutic molecules, which involves thorough understanding of the biogenesis and physicochemical properties of miRNA and delivery carriers along with the pathophysiology of the PDAC. This review highlights the delivery strategies of miRNA modulators (mimic/inhibitor) in cancer with special emphasis on PDAC since successful delivery of miRNA in vivo constitutes the major challenge in clinical translation of this promising class of therapeutics.

Pancreatic biomarkers: Could they be the answer?

Pancreatic ductal adenocarcinoma (PDA) is known for its poor prognosis. Most of the patients are diagnosed with advanced stages, when no curative treatment is available. Currently, despite extensive clinical research on PDA, the median overall survival remains short. Diagnosis delay and primary chemo-resistance due to its intrinsic biological nature may explain the challenges to improve our results. Our knowledge about the molecular biology of PDA has exponentially increased during the last decades and its use for the development of biomarkers could help to reach better results in the clinical setting. These biomarkers could be the clue for the improvement in PDA clinical research by earlier detection strategies with diagnostic biomarkers, and by an individualization of treatment approach with prognostic and predictive biomarkers. This review summarizes the current knowledge about the molecular biology of PDA and the status of the most important prognostic and predictive biomarkers.

Vertically integrated translational studies of PDX1 as a therapeutic target for pancreatic cancer via a novel bifunctional RNAi platform

RNA interference (RNAi) represents a powerful, new tool for scientific investigation as well as a promising new form of targeted gene therapy, with applications currently in clinical trials. Bifunctional short hairpin RNA (shRNA) are synthetic RNAi molecules, engineered to utilize multiple endogenous RNAi pathways to specifically silence target genes. Pancreatic and duodenal homeobox 1 (PDX1) is a key regulator of pancreatic development, β-cell differentiation, normal β-cell function and pancreatic cancer. Our aim is to review the process of identifying PDX1 as a specific, potential RNAi target in pancreatic cancer, as well as the underlying mechanisms and various forms of RNAi, with subsequent testing and development of PDX1-targeted bifunctional shRNA therapy.

Inhibition of NRF2 by PIK-75 augments sensitivity of pancreatic cancer cells to gemcitabine

We describe the potential benefit of PIK-75 in combination of gemcitabine to treat pancreatic cancer in a preclinical mouse model. The effect of PIK-75 on the level and activity of NRF2 was characterized using various assays including reporter gene, quantitative PCR, DNA-binding and western blot analyses. Additionally, the combinatorial effect of PIK-75 and gemcitabine was evaluated in human pancreatic cancer cell lines and a xenograft model. PIK-75 reduced NRF2 protein levels and activity to regulate its target gene expression through proteasome-mediated degradation of NRF2 in human pancreatic cancer cell lines. PIK-75 also reduced the gemcitabine-induced NRF2 levels and the expression of its downstream target MRP5. Co-treatment of PIK-75 augmented the antitumor effect of gemcitabine both in vitro and in vivo. Our present study provides a strong mechanistic rationale to evaluate NRF2 targeting agents in combination with gemcitabine to treat pancreatic cancers.

Biodegradable nanocapsules as siRNA carriers for mutant K-Ras gene silencing of human pancreatic carcinoma cells

The application of small interfering RNA (siRNA)-based RNA interference (RNAi) for cancer gene therapy has attracted great attention. Gene therapy is a promising strategy for cancer treatment because it is relatively non-invasive and has a higher therapeutic specificity than chemotherapy. However, without the use of safe and efficient carriers, siRNAs cannot effectively penetrate the cell membranes and RNAi is impeded. In this work, cationic poly(lactic acid) (CPLA)-based degradable nanocapsules (NCs) are utilized as novel carriers of siRNA for effective gene silencing of pancreatic cancer cells. These CPLA-NCs can readily form nanoplexes with K-Ras siRNA and over 90% transfection efficiency is achieved using the nanoplexes. Cell viability studies show that the nanoparticles are highly biocompatible and non-toxic, indicating that CPLA-NC is a promising potential candidate for gene therapy in a clinical setting.

Molecular evidence for increased antitumor activity of gemcitabine in combination with a cyclin-dependent kinase inhibitor, P276-00 in pancreatic cancers

Background

P276-00 is a novel cyclin-dependent kinase inhibitor currently in Phase II clinical trials. Gemcitabine is a standard of care for the treatment of pancreatic cancer. The present study investigated the effect of the combination of P276-00 and gemcitabine in five pancreatic cancer cell lines.

Methods

Cytotoxic activity was evaluated by Propidium Iodide assay. Cell cycle and apoptosis was analyzed by flow cytometry. Genes and proteins known to inhibit apoptosis and contribute to chemoresistance were analysed using western blot analysis and RT-PCR. In vivo efficacy was studied in PANC-1 xenograft model.

Results

The combination of gemcitabine followed by P276-00 was found to be highly to weakly synergistic in various pancreatic cancer cell lines as assessed by the combination index. Enhancement of apoptosis in PANC-1 cells and decrease in the antiapoptotic protein Bcl-2 and survivin was seen. P276-00 potentiated the gemcitabine-induced cytotoxicity by modulation of proteins involved in chemoresistance to gemcitabine and cell cycle viz. antiapoptotic proteins p8 and cox-2, proapoptotic protein BNIP3 and cell cycle related proteins Cdk4 and cyclin D1. The above results could explain the novel mechanisms of action of the combination therapy. We also show here that gemcitabine in combination with P276-00 is much more effective as an antitumor agent compared with either agent alone in the PANC-1 xenograft tumor model in SCID mice.

Conclusions

The chemosensitzation of pancreatic tumors to gemcitabine would likely be an important and novel strategy for treatment of pancreatic cancer and enable the use of lower and safer concentrations, to pave the way for a more effective treatment in this devastating disease. Phase IIb clinical trials of P276-00 in combination with gemcitabine in pancreatic cancer patients are ongoing.

The regulatory roles of miRNA and methylation on oncogene and tumor suppressor gene expression in pancreatic cancer cells

Carcinogenesis is driven by an accumulation of mutations and genetic lesions, which leads to activation of oncogenes and inactivation of tumor suppressor genes. However, the molecular mechanisms by which the expression of these genes was regulated in pancreatic cancer remains unclear. In this study, we investigated the regulatory effects of microRNA and methylation on the expression of k-ras, TP53 and PTEN genes in pancreatic cancer cells. The protein and miRNA levels were measured by Western blotting and Northern blotting, respectively. Xenograft pancreatic tumor models were established by inoculating BxPC-1, Capan-2, and Panc-1 tumor cells into athymic nu/nu mice. A disparate level of KRAS, p53, PTEN, Dnmts, and Dicer 1 proteins as well as let-7i, miR-22, miR-143, and miR-29b miRNA was observed in BxPC-1, Capan-2, and Panc-1 cells. Knockdown of Dicer 1 expression in BxPC-3 and Panc-1 cells resulted in significant increases in KRAS, p53, PTEN, and Dnmts protein levels and significant decreases in miR-22, miR-143, let-7i, and miR-29b expression. Knockdown of Dicer 1 expression in Capan-2 cells significantly increased p53 and PTEN expression, while significantly decreased miR-22 and miR-143 expression, but had no effects on PTEN, Dnmts, let-7i, and miR-29b expression. Knockdown of Dicer 1 expression significantly inhibited xenograft BxPC-3 tumor growth, but promoted xenograft Panc-1 tumor growth. In contrast, knockdown of Dicer 1 expression had no effect on xenograft Capan-2 tumor growth. Our study suggested that different pancreatic cancer cell lines exhibited obvious discrepancies in gene expression profiles, implying that different molecular mechanisms are involved in the carcinogenesis of pancreatic cancer subclasses. Our study highlighted the importance of personalized therapy.

A transcriptome analysis by lasso penalized Cox regression for pancreatic cancer survival

Pancreatic cancer is the fourth leading cause of cancer deaths in the United States with five-year survival rates less than 5% due to rare detection in early stages. Identification of genes that are directly correlated to pancreatic cancer survival is crucial for pancreatic cancer diagnostics and treatment. However, no existing GWAS or transcriptome studies are available for addressing this problem. We apply lasso penalized Cox regression to a transcriptome study to identify genes that are directly related to pancreatic cancer survival. This method is capable of handling the right censoring effect of survival times and the ultrahigh dimensionality of genetic data. A cyclic coordinate descent algorithm is employed to rapidly select the most relevant genes and eliminate the irrelevant ones. Twelve genes have been identified and verified to be directly correlated to pancreatic cancer survival time and can be used for the prediction of future patient's survival.

Current knowledge on pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer death with a median survival of 6 months and a dismal 5-year survival rate of 3-5%. The development and progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways. Therefore, the strategies targeting these molecules as well as their downstream signaling could be promising for the prevention and treatment of pancreatic cancer. However, although targeted therapies for pancreatic cancer have yielded encouraging results in vitro and in animal models, these findings have not been translated into improved outcomes in clinical trials. This failure is due to an incomplete understanding of the biology of pancreatic cancer and to the selection of poorly efficient or imperfectly targeted agents. In this review, we will critically present the current knowledge regarding the molecular, biochemical, clinical, and therapeutic aspects of pancreatic cancer.

Drugs in preclinical and early-stage clinical development for pancreatic cancer

INTRODUCTION

Pancreatic cancer (PC) is the fourth leading cause of cancer-related deaths in the US and Europe, and the lethality of this cancer is demonstrated by the fact that the annual incidences are approximately equal to the annual deaths. Current therapy for PC is multimodal, involving surgery and chemotherapy. Clinical symptoms are unspecific, and consequently about 85% of patients with PC are diagnosed at advanced tumor stages without any surgical therapy options. Since the therapeutic rates for PC are so dismal, it is essential to review the clinical targets for diagnosis and treatment of this lethal cancer.

AREAS COVERED

In this review, we discuss potential treatment options for PC by identifying molecular targets including those involved in cell proliferation, survival, migration, invasion and angiogenesis. Targeting these molecules in combination with surgery could improve the clinical outcome for PC patients.

EXPERT OPINION

For a decade, gemcitabine has remained the single first-line chemotherapeutic agent for advanced adenocarcinoma of the pancreas; however, less than 25% of patients benefit from gemcitabine. The reason for frequent reoccurrence of PC after conventional methods such as surgery, radiation and/or chemotherapy is due to the lack of understanding of the basic underlying metabolic cause of the cancer and thus consequently remains uncorrected. Our understanding of drug resistance in PC is still not clear and may be answered by focusing on new useful biomarkers and their role in chemo- and radioresistance.

Coffee, tea, and sugar-sweetened carbonated soft drink intake and pancreatic cancer risk: a pooled analysis of 14 cohort studies

BACKGROUND

Coffee has been hypothesized to have pro- and anticarcinogenic properties, whereas tea may contain anticarcinogenic compounds. Studies assessing coffee intake and pancreatic cancer risk have yielded mixed results, whereas findings for tea intake have mostly been null. Sugar-sweetened carbonated soft drink (SSB) intake has been associated with higher circulating levels of insulin, which may promote carcinogenesis. Few prospective studies have examined SSB intake and pancreatic cancer risk; results have been heterogeneous.

METHODS

In this pooled analysis from 14 prospective cohort studies, 2,185 incident pancreatic cancer cases were identified among 853,894 individuals during follow-up. Multivariate (MV) study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated using Cox proportional hazards models and then pooled using a random-effects model.

RESULTS

No statistically significant associations were observed between pancreatic cancer risk and intake of coffee (MVRR = 1.10; 95% CI, 0.81-1.48 comparing ≥900 to <0 g/d; 237g ≈ 8oz), tea (MVRR = 0.96; 95% CI, 0.78-1.16 comparing ≥400 to 0 g/d; 237g ≈ 8oz), or SSB (MVRR = 1.19; 95% CI, 0.98-1.46 comparing ≥250 to 0 g/d; 355g ≈ 12oz; P value, test for between-studies heterogeneity > 0.05). These associations were consistent across levels of sex, smoking status, and body mass index. When modeled as a continuous variable, a positive association was evident for SSB (MVRR = 1.06; 95% CI, 1.02-1.12).

CONCLUSION AND IMPACT

Overall, no associations were observed for intakes of coffee or tea during adulthood and pancreatic cancer risk. Although we were only able to examine modest intake of SSB, there was a suggestive, modest positive association for risk of pancreatic cancer for intakes of SSB.

SMAD4-dependent polysome RNA recruitment in human pancreatic cancer cells

Pancreatic cancer is the fourth leading cause of cancer death in the United States because most patients are diagnosed too late in the course of the disease to be treated effectively. Thus, there is a pressing need to more clearly understand how gene expression is regulated in cancer cells and to identify new biomarkers and therapeutic targets. Translational regulation is thought to occur primarily through non-SMAD directed signaling pathways. We tested the hypothesis that SMAD4-dependent signaling does play a role in the regulation of mRNA entry into polysomes and that novel candidate genes in pancreatic cancer could be identified using polysome RNA from the human pancreatic cancer cell line BxPC3 with or without a functional SMAD4 gene. We found that (i) differentially expressed whole cell and cytoplasm RNA levels are both poor predictors of polysome RNA levels; (ii) for a majority of RNAs, differential RNA levels are regulated independently in the nucleus, cytoplasm, and polysomes; (iii) for most of the remaining polysome RNA, levels are regulated via a "tagging" of the RNAs in the nucleus for rapid entry into the polysomes; (iv) a SMAD4-dependent pathway appears to indeed play a role in regulating mRNA entry into polysomes; and (v) a gene list derived from differentially expressed polysome RNA in BxPC3 cells generated new candidate genes and cell pathways potentially related to pancreatic cancer.

[New perspectives for radiosensitization in pancreatic carcinoma: a review of mechanisms involved in pancreatic tumorigenesis]

Pancreatic carcinoma is the fifth leading cause of cancer-related mortality. The 5-year overall survival is less than 5 %. This very poor prognosis can be explained both by late diagnosis and by treatment resistance, including resistance to radiation therapy. A better understanding of the pancreatic tumorigenesis and knowledge of the most frequent mutations in pancreatic adenocarcinoma (KRAS, p16, TP53, Smad4) open new perspectives for the development of more effective treatments. This review presents the major genetic and molecular alterations in pancreatic cancer that could be targeted to improve radiosensitization.

Association of diabetes susceptibility gene calpain-10 with pancreatic cancer among smokers

OBJECTIVE

The objective of this study was to test the association between calpain-10 (CAPN10), a diabetes susceptibility gene, with risk of pancreatic cancer (PC).

METHODS

DNA samples from 83 incident exocrine PC cases and 166 controls, all of whom were smokers, were genotyped for four markers of CAPN10 in a nested case-control study based on the Beta-Carotene and Retinol Efficacy Trial (CARET), a randomized chemoprevention trial of subjects at high risk of lung cancer. Controls were matched on sex, race, age, CARET intervention arm, duration of exposure to asbestos, and smoking history. Conditional logistic regression was used for statistical analyses.

RESULTS

The minor allele of SNP-43 (rs3792267) in intron 3 was associated with increased risk of PC with an odds ratio of 1.57 (95%CI 1.03-2.38, p = 0.035) per allele. The three markers of the highest risk haplotype had an odds ratio of 1.98 (95%CI 1.12-3.49, p = 0.019) for risk of PC compared to the most common haplotype. There was no evidence of interaction between either of these associations by diabetes status.

CONCLUSION

These results suggest that variation in CAPN10 may be associated with increased risk of PC among smokers. Thus, studies of genes associated with diabetes risk in PC are warranted in a larger population.

Ligand stimulation of ErbB4 and a constitutively-active ErbB4 mutant result in different biological responses in human pancreatic tumor cell lines

Pancreatic cancer is the fourth leading cause of cancer death in the United States. Indeed, it has been estimated that 37,000 Americans will die from this disease in 2010. Late diagnosis, chemoresistance, and radioresistance of these tumors are major reasons for poor patient outcome, spurring the search for pancreatic cancer early diagnostic and therapeutic targets. ErbB4 (HER4) is a member of the ErbB family of receptor tyrosine kinases (RTKs), a family that also includes the Epidermal Growth Factor Receptor (EGFR/ErbB1/HER1), Neu/ErbB2/HER2, and ErbB3/HER3. These RTKs play central roles in many human malignancies by regulating cell proliferation, survival, differentiation, invasiveness, motility, and apoptosis. In this report we demonstrate that human pancreatic tumor cell lines exhibit minimal ErbB4 expression; in contrast, these cell lines exhibit varied and in some cases abundant expression and basal tyrosine phosphorylation of EGFR, ErbB2, and ErbB3. Expression of a constitutively-dimerized and -active ErbB4 mutant inhibits clonogenic proliferation of CaPan-1, HPAC, MIA PaCa-2, and PANC-1 pancreatic tumor cell lines. In contrast, expression of wild-type ErbB4 in pancreatic tumor cell lines potentiates stimulation of anchorage-independent colony formation by the ErbB4 ligand Neuregulin 1β. These results illustrate the multiple roles that ErbB4 may be playing in pancreatic tumorigenesis and tumor progression.

Blocking angiotensin II Type 1 receptor triggers apoptotic cell death in human pancreatic cancer cells

OBJECTIVES

Pancreatic ductal adenocarcinoma (PDA) is an aggressive malignancy with an annual mortality rate close to its annual incidence. We recently demonstrated that angiotensin II (AngII) type 1 receptor (AT1R) might be involved in PDA angiogenesis. This study evaluated the antiproliferative and proapoptotic effects of an AT1R blocker, losartan, in PDA cells with different p53 mutation status.

METHODS

Cell cycle was analyzed by flow cytometric analysis of DNA content; apoptosis by annexin V-fluorescein isothiocyanate (V-FITC) and terminal deoxytransferase (TdT)-mediated dUTP nick-end labeling staining; messenger RNA and protein by real-time polymerase chain reaction and Western blotting; caspase-3 activity by colorimetric assay; and promoter activity by luciferase assay.

RESULTS

Losartan dose-dependently decreased cell survival and increased their preG1 accumulation. It also increased p53, p21, p27, and Bax and reduced Bcl-2 and Bcl-xl expression. In wtp53 cells, losartan increased p53 transcription and activated caspase-3 in both cell lines. However, its proapoptotic effects in mtp53 cells were mainly caspase-3-dependent.

CONCLUSION

Our data describe the involvement of AT1R in PDA cell apoptotic machinery and provide the first evidences that losartan stimulates the proapoptotic signaling pathways regardless of the p53 mutation status. As loss of p53 function is frequently observed in PDA patients, our data suggest AT1R blockade as a novel therapeutic strategy to control PDA growth.

Phenotype and genotype of pancreatic cancer cell lines

The dismal prognosis of pancreatic adenocarcinoma is due in part to a lack of molecular information regarding disease development. Established cell lines remain a useful tool for investigating these molecular events. Here we present a review of available information on commonly used pancreatic adenocarcinoma cell lines as a resource to help investigators select the cell lines most appropriate for their particular research needs. Information on clinical history; in vitro and in vivo growth characteristics; phenotypic characteristics, such as adhesion, invasion, migration, and tumorigenesis; and genotypic status of commonly altered genes (KRAS, p53, p16, and SMAD4) was evaluated. Identification of both consensus and discrepant information in the literature suggests careful evaluation before selection of cell lines and attention be given to cell line authentication.

Tumors of the Pancreatic Body and Tail

Tumors of the pancreatic body and tail are uncommon. They have a propensity to present late and often attain a large size with local invasion before they produce any clinical symptoms. The current review aims at comprehensively analysing these tumors with respect to their pathology, presentation, the investigation of these tumors, and finally the latest trends in their surgical and medical management.

Implementation of novel pyrosequencing assays to screen for common mutations of BRAF and KRAS in a cohort of sporadic colorectal cancers

Activating mutations of the BRAF and KRAS genes cause constitutive stimulation of an important cell-signaling pathway promoting tumorigenesis, and are increasingly recognized as determinants of response to targeted cancer therapies. The V600E mutation accounts for most of the BRAF mutations in cancer, and KRAS mutations are predominantly encoded by nucleotide substitutions within codons 12 and 13. We designed novel pyrosequencing assays for the detection of the common "hotspot" mutations in these genes, which demonstrated analytical sensitivities of <or=10% in titrations of mutant cell lines. The KRAS pyrosequencing assay has the ability to simultaneously identify all potential nucleotide changes within the mutation cluster at codons 12 and 13, with a sequence output in the sense direction to facilitate results interpretation. These assays were used to determine the mutation status in a prospective series of 1198 sporadic colorectal cancers. The BRAF V600E mutation was detected in 13.2% of the colorectal cancers. The frequency of KRAS mutations in our cohort was 32.4%, with G>A transitions at position 2 of codons 12 and 13 being most prevalent. Both assays proved highly sensitive and specific when applied to clinical specimens, and were applicable to both fresh-frozen and formalin-fixed paraffin-embedded archival tissues. These assays would serve as a suitable platform for large-scale mutation detection in cancer specimens where the facility for pyrosequencing is available.

Alcohol intake and pancreatic cancer risk: a pooled analysis of fourteen cohort studies

BACKGROUND

Few risk factors have been implicated in pancreatic cancer etiology. Alcohol has been theorized to promote carcinogenesis. However, epidemiologic studies have reported inconsistent results relating alcohol intake to pancreatic cancer risk.

METHODS

We conducted a pooled analysis of the primary data from 14 prospective cohort studies. The study sample consisted of 862,664 individuals among whom 2,187 incident pancreatic cancer cases were identified. Study-specific relative risks and 95% confidence intervals were calculated using Cox proportional hazards models and then pooled using a random effects model.

RESULTS

A slight positive association with pancreatic cancer risk was observed for alcohol intake (pooled multivariate relative risk, 1.22; 95% confidence interval, 1.03-1.45 comparing >or=30 to 0 grams/day of alcohol; P value, test for between-studies heterogeneity=0.80). For this comparison, the positive association was only statistically significant among women although the difference in the results by gender was not statistically significant (P value, test for interaction=0.19). Slightly stronger results for alcohol intake were observed when we limited the analysis to cases with adenocarcinomas of the pancreas. No statistically significant associations were observed for alcohol from wine, beer, and spirits comparing intakes of >or=5 to 0 grams/day. A stronger positive association between alcohol consumption and pancreatic cancer risk was observed among normal weight individuals compared with overweight and obese individuals (P value, test for interaction=0.01).

DISCUSSION

Our findings are consistent with a modest increase in risk of pancreatic cancer with consumption of 30 or more grams of alcohol per day.

Exdpf is a key regulator of exocrine pancreas development controlled by retinoic acid and ptf1a in zebrafish

Both endocrine and exocrine pancreatic cells arise from pancreatic-duodenal homeobox 1 (pdx1)-positive progenitors. The molecular mechanisms controlling cell fate determination and subsequent proliferation, however, are poorly understood. Unlike endocrine cells, less is known about exocrine cell specification. We report here the identification and characterization of a novel exocrine cell determinant gene, exocrine differentiation and proliferation factor (exdpf), which is highly expressed in the exocrine cell progenitors and differentiated cells of the developing pancreas in zebrafish. Knockdown of exdpf by antisense morpholino caused loss or significant reduction of exocrine cells due to lineage-specific cell cycle arrest but not apoptosis, whereas the endocrine cell mass appeared normal. Real-time PCR results demonstrated that the cell cycle arrest is mediated by up-regulation of cell cycle inhibitor genes p21(Cip), p27(Kip), and cyclin G1 in the exdpf morphants. Conversely, overexpression of exdpf resulted in an overgrowth of the exocrine pancreas and a severe reduction of the endocrine cell mass, suggesting an inhibitory role for exdpf in endocrine cell progenitors. We show that exdpf is a direct target gene of pancreas-specific transcription factor 1a (Ptf1a), a transcription factor critical for exocrine formation. Three consensus Ptf1a binding sites have been identified in the exdpf promoter region. Luciferase assay demonstrated that Ptf1a promotes transcription of the exdpf promoter. Furthermore, exdpf expression in the exocrine pancreas was lost in ptf1a morphants, and overexpression of exdpf successfully rescued exocrine formation in ptf1a-deficient embryos. Genetic evidence places expdf downstream of retinoic acid (RA), an instructive signal for pancreas development. Knocking down exdpf by morpholino abolished ectopic carboxypeptidase A (cpa) expression induced by RA. On the other hand, exdpf mRNA injection rescued endogenous cpa expression in embryos treated with diethylaminobenzaldehyde, an inhibitor of RA signaling. Moreover, exogenous RA treatment induced anterior ectopic expression of exdpf and trypsin in a similar pattern. Our study provides a new understanding of the molecular mechanisms controlling exocrine cell specification and proliferation by a novel gene, exdpf. Highly conserved in mammals, the expression level of exdpf appears elevated in several human tumors, suggesting a possible role in tumor pathogenesis.

Sp1, a new biomarker that identifies a subset of aggressive pancreatic ductal adenocarcinoma

Pancreatic adenocarcinoma is one of the leading causes of cancer-related deaths in the United States. Sp1 is a sequence-specific DNA binding protein that is important in the transcription of a number of regulatory genes involved in cancer cell growth, differentiation, and metastasis. In this study, we investigated Sp1 expression in pancreatic ductal adenocarcinoma and its association with clinical outcome. We studied 42 patients with primary pancreatic adenocarcinoma. The expression of Sp1 in pancreatic adenocarcinoma was evaluated by immunohistochemical staining. All 42 patients had clinical follow-up information and were evaluated for survival. Sp1 protein was aberrantly overexpressed in a subset of primary pancreatic adenocarcinoma. These tumors all developed metastasis, whereas none of the primary tumors without lymph node metastasis showed Sp1 overexpression. Statistically, Sp1 overexpression was associated with higher stage, higher grade, and lymph node metastasis (P < 0.001, P = 0.036, and P < 0.0001, respectively). Additionally, patients of this subset had a much shorter overall survival than patients without Sp1 overexpression, as evidenced by Kaplan-Meier plots and the log-rank test (P = 0.002). The 5-year overall survival rate was 19% in patients with Sp1 overexpression, compared with 55% in patients without Sp1 overexpression. The median survival was only 13 months for patients with Sp1 overexpression, compared with 65 months for patients without Sp1 overexpression. In conclusion, Sp1 is a new biomarker that identifies a subset of pancreatic ductal adenocarcinoma with aggressive clinical behavior. It can be used at initial diagnosis of pancreatic adenocarcinoma to identify patients with an increased probability of cancer metastasis and much shortened overall survival.

The association between selected risk factors for pancreatic cancer and the expression of p53 and K-ras codon 12 mutations

BACKGROUND

Pancreatic cancer is a major contributor to cancer mortality. Studies suggest that a few risk factors, including cigarette smoking, body mass index, having a relative with pancreatic cancer, and diabetes may be related to pancreatic cancer risk.

AIM OF THE STUDY

We conducted a case-control study in southeastern Michigan to examine the relation between the above mentioned risk factors and mutations of the K-ras oncogene and p53 tumor suppressor gene.

METHODS

Two hundred forty-five patients with newly diagnosed pancreatic cancer and 420 general population controls were enrolled in the study. For this analysis, all case subjects were restricted to the pancreatic cancer patients that had tissue blocks available for study (n = 51). In-person interviews were conducted to ascertain information on demographic and lifestyle factors. Adjusted logistic regression analyses were conducted to compare various subject characteristics of pancreatic cancer patients with K-ras and p53 mutations and their subtypes to the characteristics of the general population controls.

RESULTS

Smoking (adjusted odds ratio [aOR] = 2.0; 95% confidence interval [95%CI] = 0.9-4.3) and diabetes diagnosed 5 or more years before interview (aOR = 3.4; 95%CI = 1.3-8.8) were associated with pancreatic cancer patients positive for K-ras codon 12 mutations, but not with pancreatic cancer patients negative for K-ras codon 12 mutations. On the other hand, none of the examined risk factors were meaningfully related to patients with p53 mutations.

CONCLUSIONS

This study suggests that some recognized risk factors for pancreatic cancer may also be associated with K-ras codon 12 mutations. However, further large-scale studies are warranted.

Molecular targeted therapies for pancreatic cancer

BACKGROUND

Pancreatic cancer cells express different mutations that increase the aggressiveness and confer resistance to conventional chemotherapy and radiotherapy. Molecules that selectively bind and inhibit these mutations are effective in other solid tumors and are now emerging as a complementary therapy in pancreatic cancer. The objective of this review is to describe the effect of drugs that inhibit specific mutations present in pancreatic cancer with special emphasis on clinical trials.

DATA SOURCES

We reviewed the English-language literature (MedLine) addressing the role of drugs that target mutations present in pancreatic cancer. Both preclinical and clinical studies were included.

CONCLUSIONS

Preclinical evidence supports the combination of conventional approved therapies plus drugs that block epidermal growth factor receptor and vascular growth endothelial factor or induce apoptosis. However, most of the current clinical evidence is limited to small phase I trials evaluating the toxicity and safety of these regimens. The results of additional randomized trials that are still undergoing will clarify the role of these drugs in pancreatic cancer.

Modes of resistance to anti-angiogenic therapy

Angiogenesis inhibitors targeting the vascular endothelial growth factor (VEGF) signalling pathways are affording demonstrable therapeutic efficacy in mouse models of cancer and in an increasing number of human cancers. However, in both preclinical and clinical settings, the benefits are at best transitory and are followed by a restoration of tumour growth and progression. Emerging data support a proposition that two modes of unconventional resistance underlie such results: evasive resistance, an adaptation to circumvent the specific angiogenic blockade; and intrinsic or pre-existing indifference. Multiple mechanisms can be invoked in different tumour contexts to manifest both evasive and intrinsic resistance, motivating assessment of their prevalence and importance and in turn the design of pharmacological strategies that confer enduring anti-angiogenic therapies.

Expression of deleted in pancreatic carcinoma locus 4 and transforming growth factor-β1 in human colorectal carcinoma and their clinical significance

AIM: To investigate the expression of deleted in pancreatic carcinoma locus 4 (DPC4) and transforming growth factor-β1 (TGF-β1) in human colorectal cancer tissues and their clinical significances.

METHODS: Forty-eight samples of human colorectal carcinoma were collected from patients from January 2005 to December 2005. In situ hybridization and immunohistochemistry were used to detect DPC4/TGF-β1 mRNA and protein expression respectively.

RESULTS: The expression of DPC4 mRNA was lower in colorectal carcinoma specimens as compared with that in normal colorectal specimens (52.1% vs 72.9%, P < 0.01), while TGF-β1 mRNA expression was higher in carcinoma specimens (68.8% vs 41.7%, P < 0.01). The level of DPC4 protein expression in the cancer specimens was significantly lower than that in the normal specimens, while TGF-β1 protein level were higher in the carcinoma specimens. DPC4 expression was related with the tumor size, clinical stages, differentiation degree and lymph node metastasis, while TGF-β1 expression was related with the clinic stage, differentiation degree and lymph node metastasis. There existed a close correlation between DPC4 and TGF-β1 expression (χ² = 3.95, P < 0.05).

CONCLUSION: DPC4 and TGF-β1 are the capital factors in TGF-β transduction pathway. Low-expression of DPC4 and over-expression of TGF-β1 may serve as an index for unfavorable prognosis of colorectal carcinoma.

Chemoprevention of pancreatic cancer: characterization of Par-4 and its modulation by 3,3' diindolylmethane (DIM)

PURPOSE

Cancer chemoprevention is defined as the use of natural, synthetic, or biological agents to suppress, reverse or prevent the carcinogenic process from turning into aggressive cancer. Prostate apoptosis response-4 (Par-4) is a unique pro-apoptotic protein that selectively induces apoptosis in prostate cancer cells. However, its role in other malignancies has not been fully explored. This study tries to identify the functional significance of Par-4 in pancreatic cancer.

METHODS

Multiple molecular techniques such as Western blot analysis, trypan blue assay for cell viability, MTT assay for cell growth inhibition and Histone/DNA ELISA for apoptosis were used.

RESULTS

Western blot analysis revealed that 3,3'-diindolylmethane (DIM) a chemopreventive agent, specifically its more bioavailable formulation, B-DIM, at low doses (20 micromol/L) induces Par-4, in L3.6pl and Colo-357 pancreatic cancer cells. At similar doses, DIM reduced cell viability and caused cell growth inhibition and apoptosis. Moreover, DIM pre-treatment sensitized the cells to cytotoxic action of chemotherapeutic drug gemcitabine through up-regulation of Par-4.

CONCLUSION

The induction of Par-4 is indirectly related to increased sensitivity and cell death through apoptosis. To our knowledge the results reported here showed, for the first time, the induction of Par-4 by chemopreventive agents, in general, and DIM, in particular, in pancreatic cancer cells in vitro.

Loss of the eukaryotic initiation factor 3f in pancreatic cancer

Aberrant regulation of the translation initiation is known to contribute to tumorigenesis. eIF3 plays an important role in translation initiation. eIF3f is the p47 subunit of the eIF3 complex whose function in cancer is not clear. Initial studies from our group indicated that eIF3f expression is decreased in pancreatic cancer. Overexpression of eIF3f induces apoptosis in pancreatic cancer cells. The eIF3f gene is located at chromosome band region 11p15.4. Loss of 11p15.4 is a common event in many tumors including pancreatic cancer. In order to investigate the molecular mechanism of the decreased expression of eIF3f in pancreatic cancer, we performed loss of heterozygosity (LOH) analysis in 32 pancreatic cancer specimens using three microsatellite markers encompassing the eIF3f gene. We showed that the prevalence of LOH ranged from 71% to 93%. We also performed eIF3f gene copy number analysis using quantitative real time PCR to further confirm the specific allelic loss of eIF3f gene in pancreatic cancer. We demonstrated a statistically significant decrease of eIF3f gene copy number in pancreatic tumors compared with normal tissues with a tumor/normal ratio of 0.24. Furthermore, RNA in situ hybridization and tissue microarray immunohistochemistry analysis demonstrated that eIF3f expression is significantly decreased in human pancreatic adenocarcinoma tissues compared to normal pancreatic tissues. These data provides new insight into the understanding of the molecular pathogenesis of eIF3f during pancreatic tumorigenesis.