The Role of microRNAs in the Diagnosis and Treatment of Pancreatic Adenocarcinoma

Methylation of Tumor Suppressive miRNAs in Plasma from Patients With Pancreaticobiliary Diseases

BACKGROUND/AIM

We previously reported the usefulness of aberrant methylation of tumor suppressive miRNAs in bile to discriminate pancreaticobiliary cancers (PBCs) from benign pancreaticobiliary diseases (BD). Here we performed a methylation analysis of plasma miRNAs to identify miRNAs specific for PBCs.

PATIENTS AND METHODS

Plasma was collected from 80 patients with pancreatic cancer (PC); 18 with biliary tract cancer (BTC) and 28 with BD. Sequences encoding 3 tumor suppressive miRNAs (miR-200a, -200b, and -1247) were PCR amplified and sequenced, and their methylation rates were determined.

RESULTS

The methylation rate of miR-1247 was significantly higher in patients with BTC than in those with BD, and tended to be higher in patients with PC than in those with BD. Furthermore, it was significantly higher in three patients with stages I/II BTC than in those with BD.

CONCLUSION

Methylation of miR-1247 in plasma may be useful to distinguish BTC from BD.

Noncoding RNAs in drug-resistant pancreatic cancer: A review

Pancreatic cancer is the fourth-leading cause of cancer-related deaths and is expected to be the second-leading cause of cancer-related deaths in Europe and the United States by 2030. The high fatality rate of pancreatic cancer is ascribed to untimely diagnosis, early metastasis and limited responses to both chemotherapy and radiotherapy. Although gemcitabine, 5-fluorouracil and some other drugs can profoundly improve patient prognosis, most pancreatic cancer patients eventually develop drug resistance, leading to poor clinical outcomes. The underlying mechanisms of pancreatic cancer drug resistance are complicated and inconclusive. Interestingly, accumulating evidence has demonstrated that different noncoding RNAs (ncRNAs), such as microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), play a crucial role in pancreatic cancer resistance to chemotherapy reagents. In this paper, we systematically summarize the molecular mechanism underlying the influence of ncRNAs on the generation and development of drug resistance in pancreatic cancer and discuss the potential role of ncRNAs as prognostic markers and new therapeutic targets for pancreatic cancer.

MicroRNA-769-5p Inhibits Pancreatic Ductal Adenocarcinoma Progression by Directly Targeting and Downregulating ETS Proto-Oncogene 1

Purpose

MicroRNA-769-5p (miR-769) is aberrantly expressed and plays crucial roles in non-small cell lung cancer and melanoma. However, the expression pattern, biological role, and mechanisms of action of miR-769 in pancreatic ductal adenocarcinoma (PDAC) are yet to be fully elucidated. Therefore, we attempted to determine the potential regulatory function of miR-769 in PDAC progression and to explore the underlying mechanisms in detail.

Methods

In this study, reverse-transcription quantitative polymerase chain reaction was carried out to determine the expression profile of miR-769 in PDAC. A series of experiments, including a Cell Counting Kit-8 assay, flow-cytometric analysis, Transwell migration and invasion assays, and a xenograft animal model, were applied to test whether miR-769 affects the malignancy of PDAC.

Results

We found that miR-769 was significantly underexpressed in PDAC tissues and cell lines. The low miR-769 expression significantly correlated with the TNM stage and lymph node metastasis. Patients with PDAC harboring low miR-769 expression showed shorter overall survival than did the patients with high miR-769 expression. Forced upregulation of miR-769 suppressed PDAC cell proliferation, migration, and invasion in vitro; promoted apoptosis in vitro; and hindered tumor growth in vivo. Experiments on the mechanism identified ETS proto-oncogene 1 (ETS1) as a direct target gene of miR-769 in PDAC cells. Furthermore, ETS1 turned out to be upregulated in PDAC tissue samples, and the upregulation of ETS1 negatively correlated with miR-769 expression. Moreover, ETS1 knockdown simulated the tumor-suppressive effects of miR-769 overexpression on PDAC cells. Besides, ETS1 reintroduction attenuated the antitumor actions of miR-769 upregulation in PDAC cells.

Conclusion

Our findings indicate that miR-769 performs tumor-suppressive functions in PDAC by directly targeting ETS1, and this miRNA may represent a potential therapeutic target for the development of anticancer therapies.

The targeting of non‑coding RNAs by curcumin: Facts and hopes for cancer therapy (Review)

Curcumin [(1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl) hepta-1,6-diene-3,5-dione] is a natural polyphenol that is derived from the turmeric plant (curcuma longa L.). Curcumin is widely used in food coloring, preservatives, and condiments. Curcumin possesses anti-tumor, anti-oxidative and anti-inflammatory efficacy, as well as other pharmacological effects. Emerging evidence indicates that curcumin alters microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in various types of cancers. Both miRNAs and lncRNAs are non-coding RNAs that can epigenetically modulate the expression of multiple genes via post-transcriptional regulation. In the present review, the interactions between curcumin and non-coding RNAs are summarized in numerous types of cancers, including lung, colorectal, prostate, breast, nasopharyngeal, pancreatic, blood, and ovarian cancer, and the vital non-coding RNAs and their downstream targets are described.

MicroRNA-634 functions as a tumor suppressor in pancreatic cancer via directly targeting heat shock-related 70-kDa protein 2

Pancreatic cancer (PC) is one of the most malignant types of human cancer and has an extremely poor prognosis. MicroRNAs (miRs) reportedly serve a critical role in pancreatic ductal adenocarcinoma (PDAC) progression. Understanding the expression patterns and functions of miRs may provide strategies for the diagnosis and treatment of patients with PC. In particular, miR-634 is attracting interest due to its critical role in regulating the biology of some types of cancer. However, the expression patterns, biological function and molecular mechanism of miR-634 in PC remain unknown. In the present study, miR-634 expression levels in PC tissues and cell lines were significantly downregulated. Notably, the ectopic overexpression of miR-634 in PC cells inhibited tumor progression, whereas miR-634 silencing reversed these effects. Furthermore, reverse transcription-quantitative polymerase chain reaction, western blot analysis and the dual-luciferase assay revealed that miR-634 regulated heat shock-related 70 kDa protein 2 (HSPA2) by directly binding to its 3-untranslated region. In clinical samples of PC, miR-634 was inversely correlated with HSPA2, which was upregulated in PC. In the rescue experiment, HSPA2 overexpression partially abrogated the effects of miR-634 mimicry on biological function. In conclusion, miR-634 functioned as a tumor suppressor in regulating PC progression by targeting HSPA2 and may therefore be a novel potential therapeutic target for PC.

Overexpression of microRNA-519d-3p suppressed the growth of pancreatic cancer cells by inhibiting ribosomal protein S15A-mediated Wnt/β-catenin signaling

Ribosomal protein S15A (RPS15A) has emerged as a novel oncogene of various human cancers. However, whether RPS15A is involved in pancreatic cancer remains unclear. In this study, we aimed to investigate the potential relevance of RPS15A in pancreatic cancer and elucidate the underlying regulatory mechanism. We found that RPS15A expression was significantly up-regulated in pancreatic cancer cell lines. RPS15A knockdown resulted in a decrease of cell proliferation and colony formation, and induced cell cycle arrest in G0/G1 phases of pancreatic cancer cells in vitro. In addition, RPS15A knockdown down-regulated β-catenin expression and blocked the activation of Wnt signaling. Notably, RPS15A was identified as a target gene of microRNA-519d-3p (miR-519d-3p), a tumor suppressive miRNA. Further data showed that miR-519d-3p negatively regulated RPS15A expression in pancreatic cancer cells. Moreover, miR-591d-3p expression was significantly decreased in pancreatic cancer cell lines and tissues and was inversely correlated with RPS15A expression. The overexpression of miR-519d-3p significantly inhibited the proliferation and Wnt/β-catenin signaling in pancreatic cancer cells, mimicking the similar effect of RPS15A knockdown. However, restoration of RPS15A expression partially reversed the antitumor effect of miR-519d-3p. Taken together, our results demonstrate that RPS15A knockdown or RPS15A inhibition by miR-519d-3p suppresses the growth of pancreatic cancer cells associated with the inhibition of Wnt/β-catenin signaling. Our study suggests that the miR-519d-3p/RPS15A/Wnt/β-catenin regulation axis plays an important role in the progression of pancreatic cancer and may serve as potential targets for treatment of pancreatic cancer.

MicroRNA‑766 inhibits the malignant biological behaviours of pancreatic ductal adenocarcinoma by directly targeting ETS1

Increasing evidence indicates that numerous microRNAs (miRNAs) are altered in pancreatic ductal adenocarcinoma (PDAC), and their alterations significantly influence the malignant behaviour of PDAC. Therefore, identifying miRNAs associated with PDAC and their biological roles in the disease may provide promising therapeutic opportunities. Alteration of the expression of miRNA‑766 (miR‑766) has been previously reported in several types of human malignancy. However, to the best of our knowledge, whether miR‑766 exhibits different expression patterns in PDAC and its underlying functions in the progression of PDAC remain to be elucidated. In the present study, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to detect miR‑766 expression levels in PDAC tissues and cell lines. The effects of miR‑766 upregulation on PDAC cell proliferation and invasion were evaluated using MTT and invasion assays, respectively. The mechanisms underlying the role of miR‑766 in PDAC cells were explored using bioinformatics analysis, luciferase reporter assay, RT‑qPCR and western blot analysis. It was found that miR‑766 was significantly downregulated in PDAC tissues and cell lines. The detailed roles of miR‑766 in the progression of PDAC were characterised using Panc‑1 and Aspc‑1 cell lines. The results revealed that the upregulation of miR‑766 restricted the proliferation and invasion of PDAC cells. Through a series of experiments, it was found that E26 transformation specific‑1 (ETS1) was a direct target of miR‑766 in PDAC cells. Furthermore, ETS1 knockdown simulated the inhibitory effects of the overexpression of miR‑766 on PDAC cells, whereas the effects of miR‑766 restoration on the PDAC cells were reversed by overexpressing ETS1. In conclusion, the findings of the present study demonstrate that miR‑766 offers potential as a therapeutic target for patients with PDAC.

Down-regulation of MiR-539 Indicates Poor Prognosis in Patients with Pancreatic Cancer

It has been demonstrated that miR-539 plays an important role in the development and progression of tumors. The purpose of this study was to analyze the correlation between the expression level of miR-539 and the clinicopathological features and prognosis of patients with pancreatic cancer. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression level of miR-539 in 60 patients with pancreatic cancer. It was found that miR-539 gene expression was down-regulated in pancreatic cancer compared with that in paracancerous tissues. In addition, the expression level of miR-539 was inversely correlated with tumor differentiation (poorly to moderately differentiated vs. well differentiated, P=0.006), lymph node metastasis (positive vs. negative, P=0.006), clinical stage (III-IV vs. I-II, P=0.002), CA199 (≥200 vs. <200, P=0.019) and distant metastasis (positive vs. negative, P=0.035). The survival time of pancreatic cancer patients with low expression of miR-539 was significantly shorter than that of patients with high expression of miR-539. Multivariate analysis suggested that miR-539 expression level was an independent prognostic indicator for patients with pancreatic cancer (P=0.025). Down-regulation of miR-539 may be a potentially unfavorable prognostic factor for patients with pancreatic cancer, and further studies are needed to confirm our conclusion in the future.

MicroRNA‑3666 suppresses the growth and migration of glioblastoma cells by targeting KDM2A

MicroRNAs (miRNAs) are acknowledged as essential regulators in human cancer types, including glioblastoma (GBM). However, the functions of microRNA-3666 (miR-3666) in GBM remain unclear. In the present study, it was identified that the expression of miR-3666 was significantly downregulated in GBM tissues compared with adjacent normal tissues by reverse transcription-quantitative polymerase chain reaction. Additionally, miR-3666 was downregulated in GBM cell lines. Furthermore, it was observed that the miR-3666 expression level in patients with GBM was associated with prognosis. With functional experiments, it was identified that overexpression of miR-3666 significantly inhibited the proliferation, migration and invasion of GBM cells in vitro by Cell Counting kit-8 and Transwell assays. Ectopic expression of miR-3666 significantly arrested GBM cells in the G₀ phase by fluorescence activated cell sorting. In terms of the underlying mechanism, it was identified that lysine-specific demethylase 2A (KDM2A) is a direct target of miR-3666 in GBM cells. Overexpression of miR-3666 significantly decreased the expression of KDM2A in GBM cells. Furthermore, it was observed that knockdown of KDM2A significantly suppressed the proliferation, migration and invasion of GBM cells. Collectively, the present results demonstrated that the miR-3666/KDM2A axis serves an important role in the progression of GBM, which provides novel insight into the development of therapeutic strategies for GBM treatment.

Pre-operative Plasma miR-21-5p Is a Sensitive Biomarker and Independent Prognostic Factor in Patients with Pancreatic Ductal Adenocarcinoma Undergoing Surgical Resection

Blood plasma microRNAs (miRNAs) are emerging as a clinically useful tool for non-invasive detection and prognosis estimation in various cancer types including pancreatic ductal adenocarcinoma (PDAC). The aim of the present study was to provide an independent validation of circulating miRNAs identified in previous studies as diagnostic and/or prognostic biomarkers in PDAC. Based on the literature search, 6 miRNAs were chosen as candidates for independent validation; miR-21-5p, miR-375, miR-155, miR-17-5p, miR-126-5p and miR-1290. Validation of these miRNAs was performed in a cohort of 25 patients with PDAC undergoing surgical resection and 24 healthy donors. Plasma levels of miRNAs were determined using quantitative real-time PCR. We confirmed significantly higher levels of all tested miRNA in blood plasma of PDAC patients in comparison to healthy controls with miR-21-5p showing the highest analytical performance (p<0.001; AUC>0.99). Increased levels of miR-21-5p (p=0.045) and miR-375 (p=0.013) were significantly associated with overall survival. Multivariate analysis demonstrated that miR-21-5p is a significant unfavorable prognostic factor independent on other clinical variables including adjuvant chemotherapy (hazard ratio 2.95; 95% CI 1.06-8.18; p=0.038). Our preliminary data indicate promising diagnostic and prognostic utility of plasma miR-21-5p in PDAC patients.

Clinical utilization of serum- or plasma-based miRNAs as early detection biomarkers for pancreatic cancer: A meta-analysis up to now

BACKGROUND

Pancreatic cancer (PC) is a lethal disease, however current screening methods unable to achieve early diagnosis. Blood-based microRNAs (miRNAs) are promising molecular biomarkers for detecting PC. This meta-analysis summaries studies identifying serum- or plasma-based miRNAs dysregulated in PC patients compared to non-PC cases to evaluate their diagnostic accuracy for characterizing PC.

METHODS

A systematically reviews and meta-analysis of published studies was conducted to compare the serum or plasma miRNAs expressions between PC patients and non-PC cases. Summary estimates for sensitivity, specificity, along with other measures of accuracy of miRNAs in the diagnosis of PC were pooled using the random-effects model. I and Q tests were used to assess the heterogeneity of included studies. The Spearman test was used to analyze the threshold effect.

RESULTS

Twenty-seven eligible studies were identified after electronic search and literature selection. For single miRNA dysregulation, 32 miRNAs were found to be upregulated in PC patients, and 5 miRNAs were downregulated. Four studies identified a 2-miRNA panel, and 10 studies identified a panel consisting of 3 or more miRNAs which were used to detect PC patients. Additionally, 8 studies combined miRNA panels and carbohydrate antigen 19-9 (CA 19-9) to diagnose PC. The pooled sensitivities for these 4 groups were 0.77 to 0.85, and specificities were 0.70 to 0.87. The highest area under the curve (AUC), 0.9308, was identified using 2 miRNA panels with sensitivity and specificity of 0.79 (0.74-0.83) and 0.85 (0.81-0.89), respectively. There was great heterogeneity of these 4 miRNA groups. Results of Spearman test revealed that there existed a threshold effect on single miRNA group (r=-0.437, P=.001), and none of the other groups (P all>.05).

CONCLUSIONS

Serum- or plasma-based miRNAs are capable of distinguishing PC from non-PC with relatively high sensitivity and specificity. In future, miRNAs may be used as promising diagnostic biomarkers for detection of PC.

Nuclear Export Inhibition for Pancreatic Cancer Therapy

Pancreatic cancer is a deadly disease that is resistant to most available therapeutics. Pancreatic cancer to date has no effective drugs that could enhance the survival of patients once their disease has metastasized. There is a need for the identification of novel actionable drug targets in this unusually recalcitrant cancer. Nuclear protein transport is an important mechanism that regulates the function of several tumor suppressor proteins (TSPs) in a compartmentalization-dependent manner. High expression of the nuclear exporter chromosome maintenance region 1 (CRM1) or exportin 1 (XPO1), a common feature of several cancers including pancreatic cancer, results in excessive export of critical TSPs to the incorrect cellular compartment, leading to their functional inactivation. Small molecule inhibitors of XPO1 can block this export, retaining very important and functional TSPs in the nucleus and leading to the effective killing of the cancer cells. This review highlights the current knowledge on the role of XPO1 in pancreatic cancer and how this serves as a unique and clinically viable target in this devastating and by far incurable cancer.

MiR-142 inhibits the development of cervical cancer by targeting HMGB1

It has been reported that miRNAs is deregulated in diverse human cancers, involving human cervical cancer. However, the clinical significances and potential mechanisms of miR-142 in the development and progression of cervical cancer were not elucidated completely till now. In this study, we found that the expression of miR- 142 was obviously down-regulated in human cervical cancer tissues and a panel of cell lines. According to statistics, the expression of miR-142 was negatively related to advanced FIGO stage and lymphatic metastasis (p < 0.001). Furthermore, our functional analysis revealed the overexpression of miR-142 affected cell proliferation and invasiveness, and enhanced cell apoptosis in representative SiHa and HeLa cells. Based on the molecular level, our findings showed the 3′ untranslated region (3′-UTR) of high-mobility group box 1 protein (HMGB1) was a direct target of miR-142, and determined an inverse correlation with the expression of miR-142. Ectopic expression of HMGB1 could attenuate the inhibitory impact of miR-142 on the proliferation and invasiveness of cervical cancer cells. In conclusion, the present work suggested that miR-142 affects cervical cancer cell proliferation and invasiveness, and enhances cell apoptosis via directly targeting the expression of HMGB1, and these findings may lay a novel foundation for the promising therapy target of cervical cancer.

MicroRNA co-expression networks exhibit increased complexity in pancreatic ductal compared to Vater's papilla adenocarcinoma

MiRNA expression abnormalities in adenocarcinoma arising from pancreatic ductal system (PDAC) and Vater's papilla (PVAC) could be associated with distinctive pathologic features and clinical cancer behaviours. Our previous miRNA expression profiling data on PDAC (n=9) and PVAC (n=4) were revaluated to define differences/similarities in miRNA expression patterns. Afterwards, in order to uncover target genes and core signalling pathways regulated by specific miRNAs in these two tumour entities, miRNA interaction networks were wired for each tumour entity, and experimentally validated target genes underwent pathways enrichment analysis. One hundred and one miRNAs were altered, mainly over-expressed, in PDAC samples. Twenty-six miRNAs were deregulated in PVAC samples, where more miRNAs were down-expressed in tumours compared to normal tissues. Four miRNAs were significantly altered in both subgroups of patients, while 27 miRNAs were differentially expressed between PDAC and PVAC. Although miRNA interaction networks were more complex and dense in PDAC than in PVAC, pathways enrichment analysis uncovered a functional overlapping between PDAC and PVAC. However, shared signalling events were influenced by different miRNA and/or genes in the two tumour entities. Overall, specific miRNA expression patterns were involved in the regulation of a limited core signalling pathways in the biology landscape of PDAC and PVAC.

HnRNPK/miR-223/FBXW7 feedback cascade promotes pancreatic cancer cell growth and invasion

Several studies have identified miR-223 critically involved in various types of cancer, including pancreatic ductal adenocarcinoma (PDAC). However, its action and regulatory mechanisms in PDAC remains largely unclear. In this study, we found that the expression levels of miR-223 were increased in clinical samples with PDAC (81.6%). The upregulation of miR-223 increases the proliferation, migration, and invasive abilities of PDAC cells in vitro and in vivo. Mechanistically, miR-223 directly targeted FBXW7 and overexpression of FBXW7 reverted miR-223- induced drastic proliferation in PDAC cells. Interestingly, miR-223 promoter was found to form a coprecipitable complex with hnRNPK, and siRNA knockdown of hnRNPK in PDAC cells reduced the levels of miR-223. These results show that hnRNPK is a cellular protein that binds and affects the accumulation of miR-223 in PDAC. Furthermore, FBXW7 interacts with hnRNPK and promotes its degradation, which requires phosphorylation of hnRNPK at threonine 1695 by GSK3. Consistently, we observed an inverse expression pattern between FBXW7 and miR-223, whereas a positive expression pattern between miR-223 and hnRNPK was found in human PDAC tissues. These data unveiled an important new miR-223/FBXW7/HnRNPK feedback cascade in human PDAC.

Epigenetic alterations as biomarkers in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) prognosis remains very poor and has only marginally improved during the last decades. Epigenetic alterations have been the focus of many recent studies and offer valuable options for PDAC detection, prognosis and treatment. DNA methylation, histone modifications and microRNA (miR) level changes can be used as biomarkers. These alterations occur early in carcinogenesis and may be specific for PDAC. Additionally, epigenetic alterations can be analyzed from cell-free DNA, free-circulating nucleosomes or shed tumor cells in blood. High-throughput methods are available for miR and DNA methylation level detection. In particular, multiple promising miR level changes have been discovered. No single epigenetic biomarker that offers a sufficient specificity has been discovered yet, but patterns containing multiple independent biomarkers exist.

Down-regulation of PARP1 by miR-891b sensitizes human breast cancer cells to alkylating chemotherapeutic drugs

PURPOSE

Breast cancer is the most common invasive type of cancer among women. Role of different microRNAs (miRNAs) and poly(ADP-ribose) polymerases (PARPs) in breast cancer has been well established. This study aimed to explore the effects of miR-891b on sensitizing breast cancer cells to alkylating chemotherapeutic drugs through PARPs.

METHODS

The expression of miR-891b and PARP1 in human breast cancer cells HCC1806 was overexpressed by transfection with their mimics or expressing vector. Then, the transfected cells were exposed to 40 µM N-methyl-N-nitro-N-nitrosoguanidine (MNNG) for 1 h. The correlation between miR-891b and PARP1 was detected by RT-qPCR, western blot, and dual-luciferase reporter assay. Besides, MTT assay and Annexin V assay were done to measure cell proliferation and apoptosis, respectively.

RESULTS

PARP1 was a target of miR-891b, and it was negatively regulated by miR-891b. MiR-891b increased the sensitivity of the HCC1806 cells to the cytotoxic effects of MNNG through suppressing cell proliferation and increasing the percentage of apoptotic cells. Restoration of PARP1 activity in the HCC1806 cells led to loss of miR-891b mediated sensitivity of the HCC1806 cells to MNNG.

CONCLUSION

MiR-891b increases the sensitivity of the breast cancer cells (HCC1806) to the cytotoxic effects of the chemotherapeutic agent MNNG by suppressing the expression of PARP1.

Early detection of pancreatic cancer: Where are we now and where are we going?

Pancreatic cancer (PC) is one of the most lethal malignancies. Recent studies indicate that patients with incidentally diagnosed PC have better prognosis than those with symptoms and that there is a sufficient window for early detection. However, effective early diagnosis remains difficult and depends mainly on imaging modalities and the development of screening methodologies with highly sensitive and specific biomarkers. This review summarizes recent advances in effective screening for early diagnosis of PC using imaging modalities and novel molecular biomarkers discovered from various "omics" studies including genomics, epigenomics, non-coding RNA, metabonomics, liquid biopsy (CTC, ctDNA and exosomes) and microbiomes, and their use in body fluids (feces, urine and saliva). Although many biomarkers for early detection of PC have been discovered through various methods, larger scale and rigorous validation is required before their application in the clinic. In addition, more effective and specific biomarkers of PC are urgently needed.

Identification of candidate miRNA biomarkers for pancreatic ductal adenocarcinoma by weighted gene co-expression network analysis

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a dismal prognosis which is, among others, due to a lack of suitable biomarkers and therapeutic targets. Previously, basic gene expression analysis methods have been used for their identification, but recently new algorithms have been developed allowing more comprehensive data analyses. Among them, weighted gene co-expression network analysis (WGCNA) has already been applied to several cancer types with promising results.

METHODS

We applied WGCNA to miRNA expression data from PDAC patients. Specifically, we processed microarray-based expression data of 2555 miRNAs in serum from 100 PDAC patients and 150 healthy subjects. We identified network modules of co-expressed miRNAs in the healthy subject dataset and verified their preservation in the PDAC dataset. In the non-preserved modules, we selected key miRNAs and carried out functional enrichment analyses of their experimentally known target genes. Finally, we tested their prognostic significance using overall survival analyses.

RESULTS

Through WGCNA we identified several miRNAs that discriminate healthy subjects from PDAC patients and that, therefore, may play critical roles in PDAC development. At a functional level, we found that they regulate p53, FoxO and ErbB associated cellular signalling pathways, as well as cell cycle progression and various genes known to be involved in PDAC development. Some miRNAs were also found to serve as novel prognostic biomarkers, whereas others have previously already been proposed as such, thereby validating the WGCNA approach. In addition, we found that these novel data may explain at least some of our previous PDAC gene expression analysis results.

CONCLUSIONS

We identified several miRNAs critical for PDAC development using WGCNA. These miRNAs may serve as biomarkers for PDAC diagnosis/prognosis and patient stratification, and as putative novel therapeutic targets.

A new function for miRNAs as regulators of autophagy

Autophagy is a self-digestive process regulated by an intricate network of factors able either to ensure the prosurvival function of autophagy or to convert it in a death pathway. Recently, the involvement of miRNAs in the regulation of autophagy networks has been reported. This review will summarize the main features of these small noncoding endogenous RNAs, focusing on their relevance in cancer and finally addressing their impact on autophagy.

miR-15b Inhibits the Progression of Glioblastoma Cells Through Targeting Insulin-like Growth Factor Receptor 1

The microRNAs (miRNAs) have been suggested as a tumor suppressor in recent years. miR-15b was reported to exert an anti-oncogenic role in the proliferation, migration, and invasion of diverse tumor cells. However, the mechanisms underlying miR-15b-mediated biology of glioblastoma are still unclear. In the present study, the expression of miR-15b was down-regulated in glioblastoma tumor tissues and U87 and U251 cells, but insulin-like growth factor receptor 1 (IGF1R) expression became up-regulated in these tumor tissues and cells (all p < 0.001). Furthermore, IGF1R expression was inversely associated with miR-15b expression. Notably, patients with lower miR-15b expression have a much shorter survival period compared with high expression (log-rank test p = 0.045). In vitro data demonstrated that miR-15b mimics inhibited the proliferation, cell cycle arrest, and invasion of U87 and U251 cells. Besides, we validated IGF1R as a direct target of miR-15b using dual luciferase assays, and IGF1R plasmids partially abrogated miR-15b mimics inhibited cell proliferation. In vivo, miR-15b mimics indeed repressed cell proliferation in mouse xenograft model. In conclusion, our study demonstrated that miR-15b inhibits the progression of glioblastoma cells through targeting IGF1R, and miR-15b can be recommended as a tumor suppressor in the progression of glioblastoma.

MicroRNA-206 Inhibited the Progression of Glioblastoma Through BCL-2

Gliomas are the most common type of brain tumor and have a poor prognosis. MicroRNAs (miRNAs) are a class of small, endogenous, and non-coding RNAs that play crucial roles in cell proliferation, survival, and invasion. Deregulated expression of miR-206 has been investigated in many cancers. However, the role of miR-206 in glioblastoma is still unclear. In the present study, we found that the expression of miR-206 was decreased in cancer tissues compared with normal tissues. However, the expression level of BCL-2 was higher in cancer tissues than that in normal tissues (all p < 0.001). Statistically, the expression level of BCL-2 was inversely correlated with the miR-206. In addition, the overall survival of glioblastoma patients with lower miR-206 expression was significantly shorter than those with high miR-206 expression (p < 0.001). Besides, the expression of miR-206 was also decreased in U87 and U251 cells. In vitro assays showed that ectopic miR-206 expression affected the proliferation, cell cycle, and invasion in U87 and U251 cells. Importantly, we identified BCL-2 as a direct target of miR-206 in U87 and U251 cells using luciferase assay. Overexpression of BCL-2 partially attenuated the miR-206-mediated cell proliferation. In vivo, overexpression of miR-206 suppressed the progression of glioblastoma cells using mice xenograft model. In conclusion, this study suggested that miR-206 could act as a tumor suppressor gene through inhibiting BCL-2 in the development of glioblastoma.