MicroRNA expression alterations are linked to tumorigenesis and non-neoplastic processes in pancreatic ductal adenocarcinoma

Epigenetic mechanisms in commonly occurring cancers

Cancer is a collection of very complex diseases that share many traits while differing in many ways as well. This makes a universal cure difficult to attain, and it highlights the importance of understanding each type of cancer at a molecular level. Although many strides have been made in identifying the genetic causes for some cancers, we now understand that simple changes in the primary DNA sequence cannot explain the many steps that are necessary to turn a normal cell into a rouge cancer cell. In recent years, some research has shifted to focusing on detailing epigenetic contributions to the development and progression of cancer. These changes occur apart from primary genomic sequences and include DNA methylation, histone modifications, and miRNA expression. Since these epigenetic modifications are reversible, drugs targeting epigenetic changes are becoming more common in clinical settings. Daily discoveries elucidating these complex epigenetic processes are leading to advances in the field of cancer research. These advances, however, come at a rapid and often overwhelming pace. This review specifically summarizes the main epigenetic mechanisms currently documented in solid tumors common in the United States and Europe.

Circulating microRNAs in serum of human K-ras oncogene transgenic rats with pancreatic ductal adenocarcinomas

OBJECTIVES

Novel biomarkers for pancreatic ductal adenocarcinoma (PDAC) are urgently needed because of its poor prognosis. We have previously established an animal model for human PDAC using transgenic rats in which expression of a human K-ras(G12V) oncogene is regulated by the Cre/lox system. Using this model, we searched for candidate circulating microRNAs (miRNAs) for use as novel clinical diagnostic biomarkers for PDAC.

METHODS

Rats bearing PDACs were generated using our model. MicroRNA expression in serum and pancreatic tissues of PDAC and control rats was compared by microarray analysis. Rat serum levels of 28 miRNAs identified by microarray analysis and 4 miRNAs previously reported to be high in plasma of PDAC patients were quantified by real-time quantitative reverse transcription polymerase chain reaction.

RESULTS

Quantification by real-time quantitative polymerase chain reaction revealed that miR-155, miR-21, and miR-210 were higher in serum of PDAC rats, similar to plasma of patients with PDAC. In addition, miR-18a, miR-203, miR-30b-5p, miR-31, miR-369-5p, miR-376a, and miR-541 were higher and miR-375 was lower in the serum of PDAC rats.

CONCLUSION

We identified 4 previously unreported miRNAs (miRNA-203, miRNA-369-5p, miRNA-376a, and miRNA-375) whose expression is significantly different in PDAC rats compared to control rats. These miRNAs need to be quantitated in humans as potential novel clinical diagnostic biomarkers for PDAC.

Early diagnosis of pancreatic cancer: challenges and new developments

Pancreatic cancer is a lethal malignancy with its incidence almost equivalent to mortality. The complex pathophysiology, absence of early diagnostic and prognostic markers and unresponsiveness to radiation and chemotherapies are major barriers against successful therapy. Poor performance of therapeutic agents, even in the initial stage of invasive cases, emphasizes the importance of early detection for improved survival. The present review discusses the challenges and advances in biomarkers including serological signatures, circulating tumor cells, autoantibodies, epigenetic markers and miRNAs that are being explored to detect this cancer at early stages. Considering the long time gap between the development of malignant lesions and full-blown primary and metastatic pancreatic cancer, unique opportunities are being contemplated for the development of potential diagnostic and prognostic markers.

Significance of miR-196b in tumor-related epilepsy of patients with gliomas

Objectives

Seizure is a common presenting symptom of primary brain tumors. There are no published studies regarding the roles of MicroRNA (miRNA) in tumor-related epilepsy. The authors set out to correlate miR-196b expression in low-grade glioma patients with pre-operative seizures and post-operative seizure control.

Methods

Twenty-three patients with WHO grade II astrocytomas and 83 similar patients for independent validation were included. Follow-up visits regarding seizure prognosis were scheduled at 6 months. MiRNA profiling was used to identify differentially expressed miRNAs. The most important miRNA was determined by quantitative reverse-transcriptase polymerase chain reaction (q-PCR) in the validation cohort. Gene ontology (GO) analysis and whole genome mRNA profiling was performed to investigate the underlying biological processes.

Results

Array results showed that 30 miRNAs were overexpressed and 10 miRNAs were underexpressed (with more than 2 fold change) in patients with pre-operative seizures. MiR-196b was validated in the independent validation cohort. Patients with good seizure prognosis exhibited low levels of miR-196b expression compared with those who had poor seizure prognosis in the group without pre-operative seizures. Biological processes that relate to transcription and cell cycles were over-represented in the miR-196b-associated gene expression signature. MiR-196b-associated gene expression profiling was characterized by enrichment of genes usually involved in cell proliferation.

Conclusions

We have provided the first evidence that expression of miR-196b was associated with the occurrence of pre-operative seizures in low-grade gliomas, and may predict seizure prognosis in patients without pre-operative seizures. Targeted treatments that decrease endogenous levels of miR-196b might represent novel therapeutic strategies.

Focal aberrations indicate EYA2 and hsa-miR-375 as oncogene and tumor suppressor in cervical carcinogenesis

Cervical cancer results from persistent infection with high-risk human papillomavirus (hrHPV). Common genetic aberrations in cervical (pre)cancers encompass large genomic regions with numerous genes, hampering identification of driver genes. This study aimed to identify genes functionally involved in HPV-mediated transformation by analysis of focal aberrations (<3 Mb) in high-grade cervical intraepithelial neoplasia (hgCIN). Focal chromosomal aberrations were determined in high-resolution array comparative genomic hybridization data of 60 hgCIN. Genes located within focal aberrations were validated using 2 external gene expression datasets or qRT-PCR. Functional roles of candidate genes EYA2 (20q13) and hsa-miR-375 (2q35) were studied by siRNA-mediated knock-down and overexpression, respectively, in hrHPV-containing cell lines. We identified 74 focal aberrations encoding 305 genes. Concurrent altered expression in hgCIN and/or cervical carcinomas compared with normal cervical samples was shown for ATP13A3, HES1, OPA1, HRASLS, EYA2, ZMYND8, APOBEC2, and NCR2. Gene silencing of EYA2 significantly reduced viability, migratory capacity, and anchorage-independent growth of HPV16-transformed keratinocytes. For hsa-miR-375, a direct correlation between a (focal) loss and significantly reduced expression was found. Downregulation of hsa-miR-375 expression was confirmed in an independent series of cervical tissues. Ectopic expression of hsa-miR-375 in 2 cervical carcinoma cell lines reduced cellular viability. Our data provide a proof of concept that chromosomal aberrations are actively contributing to HPV-induced carcinogenesis and identify EYA2 and hsa-miR-375 as oncogene and tumor suppressor gene, respectively.

Hepatitis B and C virus infections as possible risk factor for pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PAC) is a very aggressive and lethal cancer, with a very poor prognosis, because of absence of early symptoms, advanced stage at presentation, early metastatic dissemination and lack of both specific tests to detect its growth in the initial phases and effective systemic therapies. To date, the causes of PAC still remain largely unknown, but multiple lines of evidence from epidemiological and laboratory researches suggest that about 15-20% of all cancers are linked in some way to chronic infection, in particular it has been shown that several viruses have a role in human carcinogenesis. The purpose of this report is to discuss the hypothesis that two well-known oncogenic viruses, Human B hepatitis (HBV) and Human C hepatitis (HCV) are a possible risk factor for this cancer. Therefore, with the aim to examine the potential link between these viruses and PAC, we performed a selection of observational studies evaluating this association and we hypothesized that some pathogenetic mechanisms involved in liver carcinogenesis might be in common with pancreatic cancer development in patients with serum markers of present or past HBV and HCV infections. To date the available observational studies performed are few, heterogeneous in design as well as in end-points and with not univocal results, nevertheless they might represent the starting-point for future larger and better designed clinical trials to define this hypothesized relationship. Should these further studies confirm an association between HBV/HCV infection and PAC, screening programs might be justified in patients with active or previous hepatitis B and C viral infection.

Dysregulation of miR-31 and miR-21 induced by zinc deficiency promotes esophageal cancer

Zinc deficiency (ZD) increases the risk of esophageal squamous cell carcinoma (ESCC). In a rat model, chronic ZD induces an inflammatory gene signature that fuels ESCC development. microRNAs regulate gene expression and are aberrantly expressed in cancers. Here we investigated whether chronic ZD (23 weeks) also induces a protumorigenic microRNA signature. Using the nanoString technology, we evaluated microRNA profiles in ZD esophagus and six additional tissues (skin, lung, pancreas, liver, prostate and peripheral blood mononuclear cells [PBMC]). ZD caused overexpression of inflammation genes and altered microRNA expression across all tissues analyzed, predictive of disease development. Importantly, the inflammatory ZD esophagus had a distinct microRNA signature resembling human ESCC or tongue SCC miRNAomes with miR-31 and miR-21 as the top-up-regulated species. Circulating miR-31 was also the top-up-regulated species in PBMCs. In ZD esophagus and tongue, oncogenic miR-31 and miR-21 overexpression was accompanied by down-regulation of their respective tumor-suppressor targets PPP2R2A and PDCD4. Importantly, esophageal miR-31 and miR-21 levels were directly associated with the appearance of ESCC in ZD rats, as compared with their cancer-free Zn-sufficient or Zn-replenished counterparts. In situ hybridization analysis in rat and human tongue SCCs localized miR-31 to tumor cells and miR-21 to stromal cells. In regressing tongue SCCs from Zn-supplemented rats, miR-31 and miR-21 expression was concomitantly reduced, establishing their responsiveness to Zn therapy. A search for putative microRNA targets revealed a bias toward genes in inflammatory pathways. Our finding that ZD causes miR-31 and miR-21 dysregulation associated with inflammation provides insight into mechanisms whereby ZD promotes ESCC.

Epigenetic regulation of kallikrein-related peptidases: there is a whole new world out there

The human kallikreins are a cluster of 15 kallikreins and kallikrein-related peptidases (KLKs). Evidence shows the involvement of KLKs in a wide range of pathophysiological processes, and underscores their potential contribution to cancer, skin and neurodegenerative disorders. The control of KLK expression is not fully elucidated. Understanding the mechanisms controlling KLK expression is an essential step towards exploring the pathogenesis of several diseases and the use of KLKs as disease biomarkers and/or therapeutic targets. Recently, epigenetic changes (including methylation, histone modification and microRNAs [miRNAs]) have drawn attention as a new dimension for controlling KLK expression. Reports showed the effect of methylation on the expression of KLK genes. This was also shown to have potential utility as a prognostic marker in cancer. miRNAs are small RNAs that control the expression of their targets at the post-transcriptional level. Target prediction showed that KLKs are potential targets of miRNAs that are dysregulated in tumors, including prostate, kidney and ovarian cancers, with downstream effect on tumor proliferation. Experimental validation remains an essential step to confirm the KLK-miRNA interaction. Epigenetic regulation of KLKs holds promise for an array of therapeutic applications in many diseases including cancer.

Feasibility of fecal microRNAs as novel biomarkers for pancreatic cancer

INTRODUCTION

Pancreatic cancer (PCA) is an aggressive tumor that associates with high mortality rates. Majority of PCA patients are diagnosed usually at late tumor stages when the therapeutic options are limited. MicroRNAs (miRNA) are involved in tumor development and are commonly dysregulated in PCA. As a proof-of-principle study, we aimed to evaluate the potential of fecal miRNAs as biomarkers for pancreatic cancer.

MATERIALS AND METHODS

Total RNA was extracted from feces using Qiagen's miRNA Mini Kit. For miRNA expression analyses we selected a subset of 7 miRNAs that are frequently dysregulated in PCA (miR-21, -143, -155, -196a, -210, -216a, -375). Subsequently, expression levels of these miRNAs were determined in fecal samples from controls (n = 15), chronic pancreatitis (n = 15) and PCA patients (n = 15) using quantitative TaqMan-PCR assays.

RESULTS

All selected miRNAs were detectable in fecal samples with high reproducibility. Four of seven miRNAs (miR-216a, -196a, -143 und -155) were detected at lower concentrations in feces of PCA patients when compared to controls (p<0.05). Analysis of fecal miRNA expression in controls and patients with chronic pancreatitis and PCA revealed that the expression of miR-216a, -196a, -143 und -155 were highest in controls and lowest in PCA. The expression of the remaining three miRNAs (miR-21, -210 and -375) remained unchanged among controls and the patients with either chronic pancreatitis or PCA.

CONCLUSION

Our data provide novel evidence for the differential expression of miRNAs in feces of patients with PCA. If successfully validated in large-scale prospective studies, the fecal miRNA biomarkers may offer novel tools for PCA screening research.

MicroRNAs function as tumor suppressors or oncogenes: aberrant expression of microRNAs in head and neck squamous cell carcinoma

MicroRNAs (miRNAs) are endogenous short non-coding RNA molecules that regulate gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. Bioinformatic analyses predict that miRNAs regulate more than 30% of protein coding genes. To date, 1921 human mature miRNAs have been registered in miRBase release 18.0 (http://microrna.sanger.ac.uk/). A growing body of evidence suggests that miRNAs are aberrantly expressed in many human carcinomas and that they play key roles in the initiation, development and metastasis of human cancers, including head and neck squamous cell carcinoma (HNSCC). In this review, eight genome-wide miRNA expression profiles were used to selected aberrantly expressed miRNAs (up-regulated and down-regulated miRNAs) in HNSCC clinical specimens including our miRNA profiles of hypopharyngeal and maxillary sinus squamous cell carcinoma. We discuss recent findings on the aberrant expression of miRNAs and their contribution to human HNSCC oncogenesis.

Expression of miR-155 in primary hepatocellular carcinoma and its effect on tumor cell proliferation

AIM: To detect the expression of microRNA 155 (miR-155) in hepatocellular carcinoma and to analyze its influence on tumor cell proliferation and apoptosis.

METHODS: The expression of miR-155 in 42 cases of primary liver cancer and matched tumor-adjacent normal tissue was detected by quantitative PCR. The expression of miR-155 in hepatocellular carcinoma cell lines HepG2 and SMMC7721 was inhibited using a miR-155-specific antisense oligonucleotide (ASO-miR-155), and cell proliferation and early apoptosis were then determined by MTT assay and flow cytometry, respectively.

RESULTS: The positive rate of miR-155 expression was significantly higher in hepatocellular carcinoma (52%) than in tumor-adjacent tissue (P < 0.05). After ASO-miR-155 was transfected into HepG2 and SMMC7721 cells using Lipofectamine, the expression of miR-155 was significantly reduced. MiR155 knockdown significantly inhibited growth and promoted early apoptosis of HepG2 and SMMC7721 cells.

CONCLUSION: MiR-155 is overexpressed in hepatocellular carcinoma. Inhibition of miR-155 expression could inhibit growth and induce early apoptosis of hepatocellular carcinoma cells. MiR-155 may become a new target for the treatment of liver cancer.

microRNA-1/133a and microRNA-206/133b clusters: dysregulation and functional roles in human cancers

MicroRNAs (miRNAs) are endogenous short non-coding RNA molecules that regulate gene expression by repressing translation or cleaving RNA transcripts in a sequence-specific manner. A growing body of evidence suggests that miRNAs are aberrantly expressed in many human cancers and that they play significant roles in the initiation, development and metastasis of human cancers. Genome-wide miRNA expression signatures provide information on the aberrant expression of miRNAs in cancers rapidly and precisely. Recently, studies from our group and others revealed that microRNA-1 (miR-1), microRNA-133a (miR-133a), microRNA-133b (miR-133b) and microRNA-206 (miR-206) are frequently downregulated in various types of cancers. Interestingly, miR-1-1/miR-133a-2, miR-1-2/miR-133a-1, and miR-206/miR-133b form homologous clusters in three different chromosomal regions of the human genome – 20q13.33, 18q11.2 and 6p12.2, respectively. Here we review recent findings on the aberrant expression and functional significance of the miR-1/miR-133a and miR-206/miR-133b clusters in human cancers.

Loss of miR-126 is crucial to pancreatic cancer progression

The tumor-suppressor miRNA 126 (miR-126) is downregulated in many tumors and has recently been placed at the heart of complex metastatic pathways. Hamada and colleagues have identified miR-126 as being downregulated in pancreatic ductal adenocarcinoma (PDAC) patient samples and cell lines. The protein ADAM9 has been implicated in the progression of various solid tumors including PDAC. ADAM9 is overexpressed in PDAC and also a direct target of miR-126. The miR-126/ADAM9 axis was subsequently established to control migration and invasion in PDAC, as well as reversal of epithelial-to-mesenchymal transition. miR-126 is also known to target other crucial oncogenes in PDAC such as KRAS and CRK. Replacing miR-126 in PDAC patients may be a novel strategy for preventing progression and metastasis.

MicroRNA expression aids the preoperative diagnosis of pancreatic ductal adenocarcinoma

OBJECTIVES

This study aimed to evaluate microRNA (miRNA) expression in pancreatic resection specimens and fine needle aspiration biopsies and determine which, if any, miRNAs aid the distinction between benign and malignant pancreatic tumors in limited cytology material.

METHODS

Resection specimens containing adenocarcinoma (n = 17), intraductal papillary mucinous neoplasms (n = 11), and nonneoplastic tissues (n = 15) were evaluated for miR-21, miR-221, miR-100, miR-155, and miR-181b expression by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), and a subset of carcinomas and intraductal papillary mucinous neoplasms was analyzed with miRNA microarrays. Cellblocks containing carcinoma (n = 26) or benign pancreatic lesions (n = 11) from fine needle aspiration biopsies were subjected to qRT-PCR for miR-21, miR-221, miR-181b, miR-196a, and miR-217.

RESULTS

Carcinomas showed higher expression of miR-21, miR-221, miR-155, miR-100, and miR-181b than benign lesions by qRT-PCR, and overexpression of miR-21, miR-221, and miR-181b was confirmed by microarray analysis. Cellblocks containing carcinoma showed higher expression of miR-21, miR-221, and miR-196a than those from benign lesions (P < 0.001, P = 0.009, and P < 0.001, respectively).

CONCLUSIONS

Pancreatic ductal adenocarcinomas show differential expression of miRNAs compared to benign pancreatic lesions. A select panel of miRNAs aids the distinction between pancreatic lesions in cytology specimens.

Cancer chemoprevention with dietary isothiocyanates mature for clinical translational research

Inverse association between dietary intake of cruciferous vegetables and cancer risk observed in population-based case-control studies is partly attributable to structurally simple but mechanistically complex phytochemicals with an isothiocyanate (-N=C=S) functional group. Cancer protective role for dietary isothiocyanates (ITCs) is substantiated by preclinical studies in rodent models. A common feature of many naturally occurring ITCs relates to their ability to cause growth arrest and cell death selectively in cancer cells. At the same time, evidence continues to accumulate to suggest that even subtle change in chemical structure of the ITCs can have a profound effect on their activity and mechanism of action. Existing mechanistic paradigm stipulates that ITCs may not only prevent cancer initiation by altering carcinogen metabolism but also inhibit post-initiation cancer development by suppressing many processes relevant to tumor progression, including cellular proliferation, neoangiogenesis, epithelial-mesenchymal transition, and self-renewal of cancer stem cells. Moreover, the ITCs are known to suppress diverse oncogenic signaling pathways often hyperactive in human cancers (e.g. nuclear factor-κB, hormone receptors, signal transducer and activator of transcription 3) to elicit cancer chemopreventive response. However, more recent studies highlight potential adverse effect of Notch activation by ITCs on their ability to inhibit migration of cancer cells. Mechanisms underlying ITC-mediated modulation of carcinogen metabolism, growth arrest, and cell death have been reviewed extensively. This article provides a perspective on bench-cage-bedside evidence supporting cancer chemopreventive role for some of the most promising ITCs. Structure-activity relationship and mechanistic complexity in the context of cancer chemoprevention with ITCs is also highlighted.

miRNA biomarkers in cyst fluid augment the diagnosis and management of pancreatic cysts

PURPOSE

The diagnosis of pancreatic cystic lesions has increased dramatically. Most are benign, whereas some, such as intraductal papillary mucinous neoplasms (IPMN), represent precursors of pancreatic adenocarcinoma. Therapeutic stratification of IPMNs is challenging without precise information on dysplasia grade and presence of invasion. We assessed the diagnostic benefit of using miRNAs as biomarkers in pancreatic cyst fluid, focusing on IPMNs because of their frequency and malignant potential.

EXPERIMENTAL DESIGN

RNA was extracted from 55 microdissected formalin-fixed, paraffin-embedded (FFPE) IPMN specimens, and 65 cyst fluid specimens aspirated following surgical resection. Expression of 750 miRNAs was evaluated with TaqMan miRNA Arrays using 22 FFPE and 15 cyst fluid specimens. Differential expression of selected miRNA candidates was validated in 33 FFPE and 50 cyst fluid specimens using TaqMan miRNA Assays.

RESULTS

We identified 26 and 37 candidate miRNAs that distinguish low-grade from high-grade IPMNs using FFPE and cyst fluid specimens, respectively. A subset of 18 miRNAs, selected from FFPE and cyst fluid data, separated high-grade IPMNs from low-grade IPMNs, serous cystadenomas (SCA) and uncommon cysts, such as solid pseudopapillary neoplasms (SPN) and cystic pancreatic neuroendocrine tumors (PanNET). A logistic regression model using nine miRNAs allowed prediction of cyst pathology implying resection (high-grade IPMNs, PanNETs, and SPNs) versus conservative management (low-grade IPMNs, SCAs), with a sensitivity of 89%, a specificity of 100%, and area under the curve of 1.

CONCLUSIONS

We found candidate miRNAs that helped identify patients with high-grade IPMN and exclude nonmucinous cysts. These classifiers will require validation in a prospective setting to ultimately confirm their clinical usefulness.

Nur77: a potential therapeutic target in cancer

INTRODUCTION

The orphan nuclear receptor Nur77 (also known as NR4A1, NGFIB, TR3, TIS1, NAK-1, or N10) is a unique transcription factor encoded by an immediate early gene. Nur77 signaling is deregulated in many cancers and constitutes an important molecule for drug targeting.

AREAS COVERED

Nur77 as a versatile transcription factor that displays distinct dual roles in cell proliferation and apoptosis. In addition, several recent insights into Nur77's non-genomic signaling through its physical interactions with various signaling proteins and its phosphorylation-dependent regulation will be highlighted. The possible mechanisms by which Nur77 supports carcinogenesis and specific examples in different human cancers will be summarized. Different approaches to target Nur77 using mimetics, natural products, and synthetic compounds are also described.

EXPERT OPINION

These latest findings shed light on the novel roles of Nur77 as an exploitable target for new cancer therapeutics. Further work which focuses on a more complete understanding of the Nur77 interactome as well as how the different networks of Nur77 functional interactions are orchestrated in a stimulus or context-specific way will aid the development of more selective, non-toxic approaches for targeting Nur77 in future.

Angiotensin II type I receptor and miR-155 in endometrial cancers: synergistic antiproliferative effects of anti-miR-155 and losartan on endometrial cancer cells

OBJECTIVE

MicroRNA-155 (miR-155) is one of the micro RNAs (miRNA) most consistently involved in neoplastic diseases, and it is known to repress the angiotensin II type 1 receptor (AGTR1). The aim of the present study was to evaluate the expressions of miR-155 and AGTR1, and to clarify the potential efficacy of anti-miR-155, alone and in combination with AGTR1 blocker losartan in endometrial cancers.

METHODS

Expressions of miR-155 and AGTR1 were evaluated using real-time PCR and immunohistochemistry. And the MTT assay was performed in endometrial cancer cells following anti-miR-155 and AGTR1 blocker (losartan) treatment, alone and in combination.

RESULTS

miR-155 was over-expressed and AGTR1 was underexpressed in endometrial carcinoma tissues. AGTR1 immunoreactivity was found in six of ten (60.0%) normal endometrium, 11 of 14 (78.6%) endometrial hyperplasia, and 27 of 62 (43.5%) endometrial carcinoma tissues (P=0.051), and patients with AGTR1 expression showed trend towards improved survival after multivariate analysis (P=0.08). We checked that abolishing the function of miR-155 and AGTR1 by anti-miR-155 or losartan inhibited cell survival of endometrial carcinoma cells, respectively, and furthermore, combined treatment showed synergistic effects.

CONCLUSIONS

In this study, we characterized the expressions of miR-155 and AGTR1 in endometrial tissues. The combined treatment with anti-miR-155 and losartan has a synergistic antiproliferative effect and an improved understanding is required to clarify whether miR-155 and AGTR1 can be used as a novel therapeutic target in endometrial cancer.

Aberrant epigenetic grooming of miRNAs in pancreatic cancer: a systems biology perspective

Pancreatic cancer (PC) is a complex disease harboring a myriad of genetic and epigenetic changes. The dismal survival of patients diagnosed with PC is in part due to de novo and acquired resistance to conventional therapeutics, resulting from deregulated signaling including aberrant expression of small nc miRNAs. Emerging research in this area has lead to the identification and characterization of deregulated miRNAs, which have generated a renewed interest and hope in that novel targeting of miRNAs may lead to a better clinical outcome for patients diagnosed with PC. However, recent evidence suggests that miRNAs are also under a highly coordinated system of epigenetic regulation emphasizing the fact that the design of miRNAs as targeted therapy may not be as simple as originally anticipated. For a successful miRNA-based therapeutic regimen, a holistic integrated approach may be required to take into account because of these emerging epigenetic regulatory mechanisms. In this article, we will discuss miRNA epigenetics, it's significance in PC and the use of a systems science to identify these aberrant epigenetically groomed miRNAs, and we believe that such knowledge would likely benefit further research to realize the dream of miRNA-based targeted therapy for human malignancies.

MicroRNAs in pancreatic cancer metabolism

Advances in understanding the biology of tumour progression and metastasis have clearly highlighted the importance of aberrant tumour metabolism, which supports not only the energy requirements but also the enormous biosynthetic needs of tumour cells. Such metabolic alterations modulate glucose, amino acid and fatty-acid-dependent metabolite biosynthesis and energy production. Although much progress has been made in understanding the somatic mutations and expression genomics behind these alterations, the regulation of these processes by microRNAs (miRNAs) is only just beginning to be appreciated. This Review focuses on the miRNAs that are potential regulators of the expression of genes whose protein products either directly regulate metabolic machinery or serve as master regulators, indirectly modulating the expression of metabolic enzymes. We focus particularly on miRNAs in pancreatic cancer.

Diagnosis of pancreatic ductal adenocarcinoma and chronic pancreatitis by measurement of microRNA abundance in blood and tissue

A solid process for diagnosis could have a substantial impact on the successful treatment of pancreatic cancer, for which currently mortality is nearly identical to incidence. Variations in the abundance of all microRNA molecules from peripheral blood cells and pancreas tissues were analyzed on microarrays and in part validated by real-time PCR assays. In total, 245 samples from two clinical centers were studied that were obtained from patients with pancreatic ductal adenocarcinoma or chronic pancreatitis and from healthy donors. Utilizing the minimally invasive blood test, receiver operating characteristic (ROC) curves and the corresponding area under the curve (AUC) analysis demonstrated very high sensitivity and specificity of a distinction between healthy people and patients with either cancer or chronic pancreatitis; respective AUC values of 0.973 and 0.950 were obtained. Confirmative and partly even more discriminative diagnosis could be performed on tissue samples with AUC values of 1.0 and 0.937, respectively. In addition, discrimination between cancer and chronic pancreatitis was achieved (AUC = 0.875). Also, several miRNAs were identified that exhibited abundance variations in both tissue and blood samples. The results could have an immediate diagnostic value for the evaluation of tumor reoccurrence in patients, who have undergone curative surgical resection, and for people with a familial risk of pancreatic cancer.

BRCA1 regulates microRNA biogenesis via the DROSHA microprocessor complex

The BRCA1 tumor suppressor associates with both the DROSHA microRNA maturation complex and primary miRNA transcripts, and promotes transcript processing.

MicroRNAs (miRNAs) are noncoding RNAs that function as key posttranscriptional regulators of gene expression. miRNA maturation is controlled by the DROSHA microprocessor complex. However, the detailed mechanism of miRNA biogenesis remains unclear. We show that the tumor suppressor breast cancer 1 (BRCA1) accelerates the processing of miRNA primary transcripts. BRCA1 increased the expressions of both precursor and mature forms of let-7a-1, miR-16-1, miR-145, and miR-34a. In addition, this tumor suppressor was shown to be directly associated with DROSHA and DDX5 of the DROSHA microprocessor complex, and it interacted with Smad3, p53, and DHX9 RNA helicase. We also found that BRCA1 recognizes the RNA secondary structure and directly binds with primary transcripts of miRNAs via a DNA-binding domain. Together, these results suggest that BRCA1 regulates miRNA biogenesis via the DROSHA microprocessor complex and Smad3/p53/DHX9. Our findings also indicate novel functions of BRCA1 in miRNA biogenesis, which may be linked to its tumor suppressor mechanism and maintenance of genomic stability.

MicroRNA-10a is overexpressed in human pancreatic cancer and involved in its invasiveness partially via suppression of the HOXA1 gene

BACKGROUND

There is increasing evidence that microRNAs are differentially expressed in many types of cancers. Despite progress in analyses of microRNAs in several types of cancers, the functional contributions of microRNAs to pancreatic cancer remain unclear.

METHODS

In the present study, the expression levels of specific microRNAs identified by microarray analyses were examined in a panel of 15 pancreatic cancer cell lines. We then investigated the functional roles of these microRNAs in the proliferation and invasion of pancreatic cancer cells.

RESULTS

Based on the microarray data, we found frequent and marked overexpression of miR-10a, miR-92, and miR-17-5p in pancreatic cancer cell lines. Microdissection analyses revealed that miR-10a was overexpressed in pancreatic cancer cells isolated from a subset of primary tumors (12 of 20, 60%) compared with precursor lesions and normal ducts (P<.01). In vitro experiments revealed that miR-10a inhibitors decreased the invasiveness of pancreatic cancer cells (P<.01), but had no effect on their proliferation. Inhibition of HOXA1, a target of miR-10a, promoted the invasiveness of pancreatic cancer cells (P<.01).

CONCLUSIONS

The present data suggest that miR-10a is overexpressed in a subset of pancreatic cancers and is involved in the invasive potential of pancreatic cancer cells partially via suppression of HOXA1.

Serum microRNA biomarkers for detection of non-small cell lung cancer

Non small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality world-wide and the majority of cases are diagnosed at late stages of disease. There is currently no cost-effective screening test for NSCLC, and the development of such a test is a public health imperative. Recent studies have suggested that chest computed tomography screening of patients at high risk of lung cancer can increase survival from disease, however, the cost effectiveness of such screening has not been established. In this Phase I/II biomarker study we examined the feasibility of using serum miRNA as biomarkers of NSCLC using RT-qPCR to examine the expression of 180 miRNAs in sera from 30 treatment naive NSCLC patients and 20 healthy controls. Receiver operating characteristic curves (ROC) and area under the curve were used to identify differentially expressed miRNA pairs that could distinguish NSCLC from healthy controls. Selected miRNA candidates were further validated in sera from an additional 55 NSCLC patients and 75 healthy controls. Examination of miRNA expression levels in serum from a multi-institutional cohort of 50 subjects (30 NSCLC patients and 20 healthy controls) identified differentially expressed miRNAs. A combination of two differentially expressed miRNAs miR-15b and miR-27b, was able to discriminate NSCLC from healthy controls with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100% in the training set. Upon further testing on additional 130 subjects (55 NSCLC and 75 healthy controls), this miRNA pair predicted NSCLC with a specificity of 84% (95% CI 0.73–0.91), sensitivity of 100% (95% CI; 0.93–1.0), NPV of 100%, and PPV of 82%. These data provide evidence that serum miRNAs have the potential to be sensitive, cost-effective biomarkers for the early detection of NSCLC. Further testing in a Phase III biomarker study in is necessary for validation of these results.

MicroRNAs targeting oncogenes are down-regulated in pancreatic malignant transformation from benign tumors

BACKGROUND

MicroRNA (miRNA) expression profiles have been described in pancreatic ductal adenocarcinoma (PDAC), but these have not been compared with pre-malignant pancreatic tumors. We wished to compare the miRNA expression signatures in pancreatic benign cystic tumors (BCT) of low and high malignant potential with PDAC, in order to identify miRNAs deregulated during PDAC development. The mechanistic consequences of miRNA dysregulation were further evaluated.

METHODS

Tissue samples were obtained at a tertiary pancreatic unit from individuals with BCT and PDAC. MiRNA profiling was performed using a custom microarray and results were validated using RT-qPCR prior to evaluation of miRNA targets.

RESULTS

Widespread miRNA down-regulation was observed in PDAC compared to low malignant potential BCT. We show that amongst those miRNAs down-regulated, miR-16, miR-126 and let-7d regulate known PDAC oncogenes (targeting BCL2, CRK and KRAS respectively). Notably, miR-126 also directly targets the KRAS transcript at a "seedless" binding site within its 3'UTR. In clinical specimens, miR-126 was strongly down-regulated in PDAC tissues, with an associated elevation in KRAS and CRK proteins. Furthermore, miR-21, a known oncogenic miRNA in pancreatic and other cancers, was not elevated in PDAC compared to serous microcystic adenoma (SMCA), but in both groups it was up-regulated compared to normal pancreas, implicating early up-regulation during malignant change.

CONCLUSIONS

Expression profiling revealed 21 miRNAs down-regulated in PDAC compared to SMCA, the most benign lesion that rarely progresses to invasive carcinoma. It appears that miR-21 up-regulation is an early event in the transformation from normal pancreatic tissue. MiRNA expression has the potential to distinguish PDAC from normal pancreas and BCT. Mechanistically the down-regulation of miR-16, miR-126 and let-7d promotes PDAC transformation by post-transcriptional up-regulation of crucial PDAC oncogenes. We show that miR-126 is able to directly target KRAS; re-expression has the potential as a therapeutic strategy against PDAC and other KRAS-driven cancers.

MiR-155 is a liposarcoma oncogene that targets casein kinase-1α and enhances β-catenin signaling

Liposarcoma can be an aggressive, debilitating, and fatal malignancy. In this study, we identifed miRNAs associated with the differentiation status of liposarcoma to gain insight into the basis for its progression. miRNA expression profiles determined in human tumors and normal fat specimens identified a dedifferentiated tumor expression signature consisting of 35 miRNAs. Deregulated miRNA expression was confirmed in a second independent sample cohort. The miR-155 was the most overexpressed miRNA and functional investigations assigned an important role in the growth of dedifferentiated liposarcoma cell lines. Transient or stable knockdown of miR-155 retarded tumor cell growth, decreased colony formation, and induced G(1)-S cell-cycle arrest in vitro and blocked tumor growth in murine xenografts in vivo. We identified casein kinase 1α (CK1α) as a direct target of miR-155 control which enhanced β-catenin signaling and cyclin D1 expression, promoting tumor cell growth. In summary, our results point to important functions for miR-155 and β-catenin signaling in progression of liposarcoma, revealing mechanistic vulnerabilities that might be exploited for both prognostic and therapeutic purposes.

MicroRNA alterations of pancreatic intraepithelial neoplasias

PURPOSE

MicroRNA (miRNA) alterations are likely to contribute to the development of pancreatic cancer and may serve as markers for the early detection of pancreatic neoplasia.

EXPERIMENTAL DESIGN

To identify the miRNA alterations that arise during the development of pancreatic cancer, we determined the levels of 735 miRNAs in 34 pancreatic intraepithelial neoplasias (PanIN) and 15 normal pancreatic duct samples isolated by laser capture microdissection using TaqMan miRNA microarrays. Differential expression of selected miRNAs was confirmed by FISH analysis and by quantitative real-time reverse transcription PCR (qRT-PCR) analysis of selected candidate miRNAs in an independent set of PanIN and normal duct samples.

RESULTS

We identified 107 aberrantly expressed miRNAs in different PanIN grades compared with normal pancreatic duct samples and 35 aberrantly expressed miRNAs in PanIN-3 lesions compared with normal pancreatic duct samples. These differentially expressed miRNAs included those that have been previously identified as differentially expressed in pancreatic ductal adenocarcinomas (PDAC; including miR-21, miR-200a/b/c, miR-216a/b, miR-217, miR-146a, miR-155, miR-182, miR-196b, miR-203, miR-222, miR-338-3p, miR-486-3p, etc.) as well as miRNAs not previously described as differentially expressed in these lesions (miR-125b, miR-296-5p, miR-183*, miR-603, miR-625/*, miR-708, etc.). miR-196b was the most selectively differentially expressed miRNA in PanIN-3 lesions.

CONCLUSIONS

Many miRNAs undergo aberrant expression in PanIN lesions and are likely to be important in the development of PDAC. The miRNAs, such as miR-196b, whose expression is limited to PanIN-3 lesions or pancreatic cancers could be useful as diagnostic markers.

Biochemical role of the collagen-rich tumour microenvironment in pancreatic cancer progression

PDAC (pancreatic ductal adenocarcinoma) is among the most deadly of human malignances. A hallmark of the disease is a pronounced collagen-rich fibrotic extracellular matrix known as the desmoplastic reaction. Intriguingly, it is precisely these areas of fibrosis in which human PDAC tumours demonstrate increased expression of a key collagenase, MT1-MMP [membrane-type 1 MMP (matrix metalloproteinase); also known as MMP-14]. Furthermore, a cytokine known to mediate fibrosis in vivo, TGF-β1 (transforming growth factor-β1), is up-regulated in human PDAC tumours and can promote MT1-MMP expression. In the present review, we examine the regulation of PDAC progression through the interplay between type I collagen (the most common extracellular matrix present in human PDAC tumours), MT1-MMP and TGF-β1. Specifically, we examine the way in which signalling events through these pathways mediates invasion, regulates microRNAs and contributes to chemoresistance.

Molecular mechanisms underlying the role of microRNAs (miRNAs) in anticancer drug resistance and implications for clinical practice

Drug resistance remains a major problem in the treatment of cancer patients for both conventional chemotherapeutic and novel biological agents. Intrinsic or acquired resistance can be caused by a range of mechanisms, including increased drug elimination, decreased drug uptake, drug inactivation and alterations of drug targets. Recent data showed that other than by genetic (mutation, amplification) and epigenetic (DNA hypermethylation, histone post-translational modification) changes, drug resistance mechanisms might also be regulated by microRNAs (miRNAs). In this review we provide an overview on the role of miRNAs in anticancer drug resistance, reporting the main studies on alterations in cell survival and/or apoptosis pathways, as well as in drug targets and determinants of drug metabolism, mediated by deregulation of miRNA expression. The current status of pharmacogenetic studies on miRNA and their possible role in cancer stem cell drug resistance are also discussed. Finally, we integrated the preclinical data with clinical evidences, in lung and pancreatic cancers, showing how the study of miRNAs could help to predict resistance of individual tumours to different anticancer drugs, and guide the oncologists in the selection of rationally based tailor-made treatments.

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.

MicroRNA molecular profiles associated with diagnosis, clinicopathologic criteria, and overall survival in patients with resectable pancreatic ductal adenocarcinoma

PURPOSE

MicroRNAs (miRNA) have potential as diagnostic and prognostic biomarkers and as therapeutic targets in cancer. We sought to establish the relationship between miRNA expression and clinicopathologic parameters, including prognosis, in pancreatic ductal adenocarcinoma (PDAC).

EXPERIMENTAL DESIGN

Global miRNA microarray expression profiling of prospectively collected fresh-frozen PDAC tissue was done on an initial test cohort of 48 patients, who had undergone pancreaticoduodenectomy between 2003 and 2008 at a single institution. We evaluated association with tumor stage, lymph node status, and site of recurrence, in addition to overall survival, using Cox regression multivariate analysis. Validation of selected potentially prognostic miRNAs was done in a separate cohort of 24 patients.

RESULTS

miRNA profiling identified expression signatures associated with PDAC, lymph node involvement, high tumor grade, and 20 miRNAs were associated with overall survival. In the initial cohort of 48 PDAC patients, high expression of miR-21 (HR = 3.22, 95% CI: 1.21-8.58) and reduced expression of miR-34a (HR = 0.15, 95% CI: 0.06-0.37) and miR-30d (HR = 0.30, 95% CI: 0.12-0.79) were associated with poor overall survival following resection independent of clinical covariates. In a further validation set of 24 patients, miR-21 and miR-34a expression again significantly correlated with overall survival (P = 0.031 and P = 0.001).

CONCLUSION

Expression patterns of miRNAs are significantly altered in PDAC. Aberrant expression of a number of miRNAs was independently associated with reduced survival, including overexpression of miR-21 and underexpression of miR-34a.

SUMMARY

miRNA expression profiles for resected PDAC were examined to identify potentially prognostic miRNAs. miRNA microarray analysis identified statistically unique profiles, which could discriminate PDAC from paired nonmalignant pancreatic tissues as well as molecular signatures that differ according to pathologic features. miRNA expression profiles correlated with overall survival of PDAC following resection, indicating that miRNAs provide prognostic utility.

A miR image of stem cells and their lineages

MicroRNAs (miRs) comprise a class of tiny (∼19-24 nucleotide), noncoding RNAs that regulate gene expression posttranscriptionally. Since the discovery of the founding members lin-4 and let-7 as key regulators in the developing nematode, miRs have been found throughout the eukaryotic kingdom. Functions for miRs are wide-ranging and encompass embryogenesis, stem cell biology, tissue differentiation, and human diseases including cancers. In this chapter, we begin by acquainting our readers with miRs and introducing them to their biogenesis. Then, we focus on the roles of miRs in stem cells during tissue development and homeostasis. We use mammalian skin as our main paradigm, but we also consider miR functions in several different types of adult stem cells. We conclude by discussing future challenges that will lead to a comprehensive understanding of miR functions in stem cells and their lineages.

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.

Up-regulation of microRNA-155 promotes cancer cell invasion and predicts poor survival of hepatocellular carcinoma following liver transplantation

PURPOSE

MicroRNAs play important roles in cancer development, progression, and metastasis. The aim of this study was to determine whether altered microRNA-155 expression is associated with hepatocellular carcinoma (HCC) recurrence and prognosis following orthotopic liver transplantation (OLT).

METHODS

Tissue specimens from 100 HCC patients following OLT were recruited. MicroRNA-155 expression levels were detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Kaplan-Meier and Cox proportional regression analyses were utilized to determine the association of microRNA-155 expression with survival of patients. MicroRNA-155 expression levels of two HCC cell lines (HepG2 and SMMC-7721) and normal liver tissue were quantified using qRT-PCR. The potential function of miR-155 on invasiveness was evaluated in the above HCC cell lines.

RESULTS

We found that microRNA-155 expression levels were high in tumor tissues in patients with post-OLT HCC recurrence (n = 45) compared with those in patients with non-recurrence (n = 55) (P = 0.001) and correlated with micro-vascular invasion of HCC tissue samples (P = 0.001). Patients with higher miR-155 expression had significantly poorer recurrence-free survival (RFS, log rank P < 0.001) and overall survival (OS, log rank P < 0.001). Multivariate analysis revealed that high miR-155 expression was an independent predictor of poor prognosis (HR 2.748, P = 0.001 for RFS; HR 5.752, P < 0.001 for OS). In addition, the invasiveness of HCC cells was significantly increased by higher microRNA-155 expression.

CONCLUSIONS

MicroRNA-155 is a candidate oncogenic microRNA and plays an important role in promoting HCC cells invasion. Our findings suggest that microRNA-155 may serve as a novel biomarker for tumor recurrence and survival of HCC patients following OLT.

Potential applications of microRNAs in cancer diagnosis, prognosis, and treatment

Early studies have established that microRNAs (miRNAs) are widely deregulated in cancer and play a critical role in cancer pathogenesis. Recent research efforts are directed now towards translating these basic discoveries into novel tests or treatments that could improve the diagnosis and outcome of cancer patients. In this review, we will summarize the potential applications of miRNAs for cancer diagnosis, prognosis, and treatment. In addition, we will discuss current pitfalls and future directions.

MicroRNAs associated with mitogen-activated protein kinase in human pancreatic cancer

Aberrant expression of microRNAs (miRNA) is associated with phenotypes of various cancers, including pancreatic cancer. However, the mechanism of the aberrant expression is largely unknown. Activation of the mitogen-activated protein kinase (MAPK) signaling pathway plays a crucial role in gene expression related to the malignant phenotype of pancreatic cancer. Hence, we studied the role of MAPK in the aberrant expression of miRNAs in pancreatic cancer cells. The alterations in expression of 183 miRNAs induced by activation or inactivation of MAPK were assayed in cultured pancreatic cancer cells and HEK293 cells by means of the quantitative real-time PCR method. We found that four miRNAs, namely, miR-7-3, miR-34a, miR-181d, and miR-193b, were preferentially associated with MAPK activity. Among these miRNAs, miR-7-3 was upregulated by active MAPK, whereas the others were downregulated. Promoter assays indicated that the promoter activities of the host genes of miR-7-3 and miR-34a were both downregulated by alteration in MAPK activity. Exogenous overexpression of the MAPK-associated miRNAs had the effect of inhibition of the proliferation of cultured pancreatic cancer cells; miR-193b was found to exhibit the most remarkable inhibition. A search for target genes of miR-193b led to identification of CCND1, NT5E, PLAU, STARD7, STMN1, and YWHAZ as the targets. Translational suppression of these genes by miR-193b was confirmed by reporter assay. These results indicate that activation of MAPK may play a significant role in aberrant expression of miRNAs and their associated phenotypes in pancreatic cancer.

The molecular and cellular heterogeneity of pancreatic ductal adenocarcinoma

Current standard therapies for pancreatic ductal adenocarcinoma have failed to attenuate the aggressiveness of this disease or confer notable improvements in survival. Previous molecular research into pancreatic cancers, along with advances in sequencing technologies, have identified many altered genes in patients with pancreatic cancer and revealed the marked genetic heterogeneity of individual tumors. Thus, the lack of success of conventional empiric therapy can be partly attributed to the underlying heterogeneity of pancreatic tumors. The genetic alterations that have been detected in pancreatic cancer range from simple mutations at the level of base pairs to complex chromosomal structural changes and rearrangements. The identification of molecular changes that are unique to an individual patient's tumors, and the subsequent development of strategies to target the tumors in a personalized approach to therapeutics, is a necessary advance to improve therapy for patients with this disease.

MicroRNA-10b is overexpressed in pancreatic cancer, promotes its invasiveness, and correlates with a poor prognosis

BACKGROUND

MicroRNAs (miRNAs) have been gaining attention as new, key molecules that contribute to carcinogenesis. In pancreatic cancer, previous profiling analyses of miRNA expression have shown that several miRNAs are differently expressed in normal and cancerous tissues. Several pancreatic cancer-specific miRNAs differed, however, in each analysis.

METHODS

We investigated the miRNA expression profiles of the pancreatic cancer cell lines CAPAN-1 and CFPAC1 and an immortalized human normal pancreatic ductal epithelial cell line (HPDE) using a high-throughput, TaqMan, qRT-PCR array analysis. We also analyzed the expression levels of this miRNA in microdissected (n = 15) and formalin-fixed, paraffin-embedded (FFPE) (n = 115) samples from pancreatic cancers by quantitative RT-PCR. Finally, we investigated the effects of this miRNA on the invasiveness of pancreatic cancer cells.

RESULTS

Based on the microarray analysis, miR-372, miR-146a, miR-204, miR-10a, and miR-10b showed particularly large differences (>10-fold changes) between both pancreatic cell lines and HPDE cells. Thirteen of the 15 pancreatic cancer cell lines showed 2.1- to 36.4-fold (median, 15.3-fold) greater levels of miR-10b than HPDE cells. Microdissection analysis revealed that miR-10b exhibited greater expression levels in pancreatic cancer cells (n = 5) than in normal pancreatic ductal cells (n = 10) (P < .020). Analysis of FFPE samples showed that high miR-10b expression was associated with a lesser overall survival (P = .014). Furthermore, miR-10b correlated with the invasiveness of pancreatic cancer cells (P < .01).

CONCLUSION

miR-10b is overexpressed in pancreatic cancer and may be involved in the invasiveness in pancreatic cancer cells, thereby leading to a poor prognosis.

MicroRNA-150 directly targets MUC4 and suppresses growth and malignant behavior of pancreatic cancer cells

Pancreatic cancer (PC) has the worst prognosis among all cancers due to its late diagnosis and lack of effective therapies. Therefore, identification of novel gene targets, which are differentially expressed in PC and functionally involved in malignant phenotypes, is critical to achieve early diagnosis and development of effective therapeutic strategies. We have shown previously that MUC4, an aberrantly overexpressed transmembrane mucin, promotes growth, invasion and metastasis of PC cells, thus underscoring its potential as a clinical target. Here, we report a novel microRNA (miRNA)-mediated mechanism underlying aberrant expression of MUC4 in PC. We demonstrate that the 3' untranslated region of MUC4 contains a highly conserved miRNA-150 (miR-150) binding motif and its direct interaction with miR-150 downregulates endogenous MUC4 protein levels. We also show that miR-150-mediated MUC4 downregulation is associated with a concomitant decrease in human epidermal growth factor receptor 2 and its phosphorylated form, leading to reduced activation of downstream signaling. Furthermore, our findings demonstrate that miR-150 overexpression inhibits growth, clonogenicity, migration and invasion and enhances intercellular adhesion in PC cells. Finally, our data reveal a downregulated expression of miR-150 in malignant pancreatic tissues, which is inversely associated with MUC4 protein levels. Altogether, these findings establish miR-150 as a novel regulator of MUC4 and a tumor suppressor miRNA in PC.

Association between miR-224 expression and cell proliferation and apoptosis in pancreatic cancer

AIM: To investigate the expression of miR-224 in pancreatic carcinoma and to evaluate the role of miR-224 in pancreatic cancer cell proliferation and apoptosis.

METHODS: The expression of miR-224 in 40 pancreatic carcinoma tissue specimens and matched tumor-adjacent nontumorous tissue specimens was detected by real-time fluorescence PCR. After using the antisense technology to decrease the expression of miR-224 in pancreatic cancer cells (Aspc-1 and Bxpc-3), MTT assay and flow cytometry were performed to investigate the impact of miR-224 down-regulation on cell proliferation, cell cycle progression and apoptosis.

RESULTS: MiR-224 was found to be overexpressed in 43% of pancreatic carcinoma cases (P < 0.05). After antisense microRNA-mediated knockdown of miR-224, the proliferation of Aspc-1 and Bxpc-3 cells was significantly inhibited. Aspc-1 and Bxpc-3 cells were mainly arrested in G₀/G₁ phase, and the percentage of cells in S and G2/M phases decreased. In addition, miR-224 knockdown in Aspc-1 and Bxpc-3 cells resulted in an increase in early apoptosis.

CONCLUSION: MiR-224 is overexpressed in human pancreatic carcinoma. Inhibition of miR-224 expression can not only effectively suppress growth but also induce cell apoptosis of Aspc-1 and Bxpc-3 cells. MiR-224 may serve as a new molecular target for the treatment of pancreatic carcinoma.

MicroRNA alterations of pancreatic intraepithelial neoplasias

PURPOSE

MicroRNA (miRNA) alterations are likely to contribute to the development of pancreatic cancer and may serve as markers for the early detection of pancreatic neoplasia.

EXPERIMENTAL DESIGN

To identify the miRNA alterations that arise during the development of pancreatic cancer, we determined the levels of 735 miRNAs in 34 pancreatic intraepithelial neoplasias (PanIN) and 15 normal pancreatic duct samples isolated by laser capture microdissection using TaqMan miRNA microarrays. Differential expression of selected miRNAs was confirmed by FISH analysis and by quantitative real-time reverse transcription PCR (qRT-PCR) analysis of selected candidate miRNAs in an independent set of PanIN and normal duct samples.

RESULTS

We identified 107 aberrantly expressed miRNAs in different PanIN grades compared with normal pancreatic duct samples and 35 aberrantly expressed miRNAs in PanIN-3 lesions compared with normal pancreatic duct samples. These differentially expressed miRNAs included those that have been previously identified as differentially expressed in pancreatic ductal adenocarcinomas (PDAC; including miR-21, miR-200a/b/c, miR-216a/b, miR-217, miR-146a, miR-155, miR-182, miR-196b, miR-203, miR-222, miR-338-3p, miR-486-3p, etc.) as well as miRNAs not previously described as differentially expressed in these lesions (miR-125b, miR-296-5p, miR-183*, miR-603, miR-625/*, miR-708, etc.). miR-196b was the most selectively differentially expressed miRNA in PanIN-3 lesions.

CONCLUSIONS

Many miRNAs undergo aberrant expression in PanIN lesions and are likely to be important in the development of PDAC. The miRNAs, such as miR-196b, whose expression is limited to PanIN-3 lesions or pancreatic cancers could be useful as diagnostic markers.

MicroRNA alterations of pancreatic intraepithelial neoplasias

PURPOSE

MicroRNA (miRNA) alterations are likely to contribute to the development of pancreatic cancer and may serve as markers for the early detection of pancreatic neoplasia.

EXPERIMENTAL DESIGN

To identify the miRNA alterations that arise during the development of pancreatic cancer, we determined the levels of 735 miRNAs in 34 pancreatic intraepithelial neoplasias (PanIN) and 15 normal pancreatic duct samples isolated by laser capture microdissection using TaqMan miRNA microarrays. Differential expression of selected miRNAs was confirmed by FISH analysis and by quantitative real-time reverse transcription PCR (qRT-PCR) analysis of selected candidate miRNAs in an independent set of PanIN and normal duct samples.

RESULTS

We identified 107 aberrantly expressed miRNAs in different PanIN grades compared with normal pancreatic duct samples and 35 aberrantly expressed miRNAs in PanIN-3 lesions compared with normal pancreatic duct samples. These differentially expressed miRNAs included those that have been previously identified as differentially expressed in pancreatic ductal adenocarcinomas (PDAC; including miR-21, miR-200a/b/c, miR-216a/b, miR-217, miR-146a, miR-155, miR-182, miR-196b, miR-203, miR-222, miR-338-3p, miR-486-3p, etc.) as well as miRNAs not previously described as differentially expressed in these lesions (miR-125b, miR-296-5p, miR-183*, miR-603, miR-625/*, miR-708, etc.). miR-196b was the most selectively differentially expressed miRNA in PanIN-3 lesions.

CONCLUSIONS

Many miRNAs undergo aberrant expression in PanIN lesions and are likely to be important in the development of PDAC. The miRNAs, such as miR-196b, whose expression is limited to PanIN-3 lesions or pancreatic cancers could be useful as diagnostic markers.

Novel diagnostic value of circulating miR-18a in plasma of patients with pancreatic cancer

BACKGROUND

Several recent studies have demonstrated that microRNAs (miRNAs) are stably detectable in the plasma/serum. We hypothesised that miR-18a in the plasma is a potential biomarker in patients with pancreatic cancer.

METHODS

miR-18a is located in the miR-17-92 cluster and reported to be highly expressed in pancreatic cancer tissues. This study was divided into three parts: (1) Confirmation of higher miR-18a levels in primary pancreatic cancer tissues and cell lines than in normal pancreatic tissues and a human fibroblast cell line. (2) Evaluation of the plasma miR-18a assay using quantitative RT-PCR by comparing plasma results obtained from 36 patients with pancreatic cancer and from 30 healthy volunteers. (3) Evaluation of the assay for monitoring tumour dynamics in patients with pancreatic cancer.

RESULTS

(1) The expression of miR-18a was significantly higher in pancreatic cancer tissues (P=0.012) and pancreatic cancer cell lines (P=0.015) than in normal tissues and fibroblasts. (2) Plasma concentrations of miR-18a were significantly higher in pancreatic cancer patients than in controls (P<0.0001). The value of the area under the receiver-operating characteristic curve (AUC) was 0.9369. (3) Plasma levels of miR-18a were significantly lower in postoperative samples than in preoperative samples (P=0.0077).

CONCLUSION

Circulating miR-18a might provide new complementary tumour markers for pancreatic cancer.

Global microRNA expression profiling of microdissected tissues identifies miR-135b as a novel biomarker for pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is known for its poor prognosis resulting from being diagnosed at an advanced stage. Accurate early diagnosis and new therapeutic modalities are therefore urgently needed. MicroRNAs (miRNAs), considered a new class of biomarkers and therapeutic targets, may be able to fulfill those needs. Combining tissue microdissection with global miRNA array analyses, cell type-specific miRNA expression profiles were generated for normal pancreatic ductal cells, acinar cells, PDAC cells derived from xenografts and also from macrodissected chronic pancreatitis (CP) tissues. We identified 78 miRNAs differentially expressed between ND and PDAC cells providing new insights into the miRNA-driven pathophysiological mechanisms involved in PDAC development. Having filtered miRNAs which are upregulated in the three pairwise comparisons of PDAC vs. ND, PDAC vs. AZ and PDAC vs. CP, we identified 15 miRNA biomarker candidates including miR-135b. Using relative qRT-PCR to measure miR-135b normalized to miR-24 in 75 FFPE specimens (42 PDAC and 33 CP) covering a broad range of tumor content, we discriminated CP from PDAC with a sensitivity and specificity of 92.9% [95% CI=(80.5, 98.5)] and 93.4% [95% CI=(79.8, 99.3)], respectively. Furthermore, the area under the curve (AUC) value reached of 0.97 was accompanied by positive and negative predictive values of 95% and 91%, respectively. In conclusion, we report pancreatic cell-specific global miRNA profiles, which offer new candidate miRNAs to be exploited for functional studies in PDAC. Furthermore, we provide evidence that miRNAs are well-suited analytes for development of sensitive and specific aid-in-diagnosis tests for PDAC.

The Renin-angiotensin system and reactive oxygen species: implications in pancreatitis

SIGNIFICANCE

The renin-angiotensin system (RAS) is a circulating hormonal system involved in the regulation of blood pressure and circulating fluid electrolytes. Recent findings have revealed that locally generated angiotensin (Ang) II plays a pivotal role in normal physiology as well as pathophysiology in various tissues and organs, including the pancreas. This review article summarizes current progress that has been made in elucidating the putative roles of Ang II in both acute and chronic pancreatitis.

RECENT ADVANCES

A convergence of evidence suggests that the underlying mechanism may involve reactive oxygen species (ROS)-generating systems, such as nicotinamide adenine dinucleotide phosphate oxidase, and subsequent elevation of proinflammatory and profibrogenic gene expression as well as protein activity. More importantly, Ang II-induced ROS interacts with other ROS-generating systems to positively feed-forward the ROS-induced signaling.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Advances in basic research indicate that RAS blockers may provide potential therapeutic role for the management of pancreatic inflammation and, more importantly, pancreatitis-associated complications. Genetic alterations resulting from a malfunction in the epigenetic control of pancreatic RAS could be a causative factor in the development of pancreatitis.

Up-regulation of microRNA-155 promotes cancer cell invasion and predicts poor survival of hepatocellular carcinoma following liver transplantation

PURPOSE

MicroRNAs play important roles in cancer development, progression, and metastasis. The aim of this study was to determine whether altered microRNA-155 expression is associated with hepatocellular carcinoma (HCC) recurrence and prognosis following orthotopic liver transplantation (OLT).

METHODS

Tissue specimens from 100 HCC patients following OLT were recruited. MicroRNA-155 expression levels were detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Kaplan-Meier and Cox proportional regression analyses were utilized to determine the association of microRNA-155 expression with survival of patients. MicroRNA-155 expression levels of two HCC cell lines (HepG2 and SMMC-7721) and normal liver tissue were quantified using qRT-PCR. The potential function of miR-155 on invasiveness was evaluated in the above HCC cell lines.

RESULTS

We found that microRNA-155 expression levels were high in tumor tissues in patients with post-OLT HCC recurrence (n = 45) compared with those in patients with non-recurrence (n = 55) (P = 0.001) and correlated with micro-vascular invasion of HCC tissue samples (P = 0.001). Patients with higher miR-155 expression had significantly poorer recurrence-free survival (RFS, log rank P < 0.001) and overall survival (OS, log rank P < 0.001). Multivariate analysis revealed that high miR-155 expression was an independent predictor of poor prognosis (HR 2.748, P = 0.001 for RFS; HR 5.752, P < 0.001 for OS). In addition, the invasiveness of HCC cells was significantly increased by higher microRNA-155 expression.

CONCLUSIONS

MicroRNA-155 is a candidate oncogenic microRNA and plays an important role in promoting HCC cells invasion. Our findings suggest that microRNA-155 may serve as a novel biomarker for tumor recurrence and survival of HCC patients following OLT.

MicroRNA-375 and MicroRNA-221: Potential Noncoding RNAs Associated with Antiproliferative Activity of Benzyl Isothiocyanate in Pancreatic Cancer

The deregulated presence or absence of microRNAs (miRNAs) might play an important role in molecular pathways leading to neoplastic transformation. At present, it is also thought that the approaches to interfere miRNA functions should be helpful for developing novel therapeutic opportunities for human cancer. In this study, we provide evidence that the anticancer agent benzyl isothiocyanate (BITC) has the ability to modulate the level of miRNAs such as miR-221 and miR-375, known to be abnormally expressed in pancreatic cancer patients. Interestingly, ectopic expression of miR-375 or the enforced silencing of miR-221 in cultured pancreatic cancer cells attenuates cell viability and sensitizes antiproliferative action of BITC. We also show that the expression of putative tumor suppressor miR-375 is more abundant in nonpathological mice pancreata than those with Kras(G12D)-driven pancreatic intraepithelial neoplasia (PanIN). To the contrary, the expression of oncogenic miR-221 is significantly elevated in the mouse pancreas with PanIN lesions. Although miR-375 has been shown to be aberrantly expressed in pancreatic cancer patients, there has not been a comprehensive study to investigate the molecular pathways targeted by this miRNA in pancreatic cancer cells. Further analysis by gene expression microarray revealed that IGFBP5 and CAV-1, potential biomarkers of pancreatic cancer, were significantly downregulated in cells transfected with miR-375. Correlatively, elevated expression of IGFBP5 and CAV-1 was evident in the mouse pancreas with preneoplastic lesions in which the expression of miR-375 wanes. Taken together, our findings suggest that anticancer agent BITC might target the expression of miR-221 and miR-375 to switch hyperproliferative pancreatic cancer cells to a hypoproliferative state.