Tamara Mh Gall

MicroRNAs Cooperatively Inhibit a Network of Tumor Suppressor Genes to Promote Pancreatic Tumor Growth and Progression

BACKGROUND & AIMS There has not been a broad analysis of the combined effects of altered activities of microRNAs (miRNAs) in pancreatic ductal adenocarcinoma (PDAC) cells, and it is unclear how these might affect tumor progression or patient outcomes. METHODS We combined data from miRNA and messenger RNA (mRNA) expression profiles and bioinformatic analyses to identify an miRNA-mRNA regulatory network in PDAC cell lines (PANC-1 and MIA PaCa-2) and in PDAC samples from patients. We used this information to identify miRNAs that contribute most to tumorigenesis. RESULTS We identified 3 miRNAs (MIR21, MIR23A, and MIR27A) that acted as cooperative repressors of a network of tumor suppressor genes that included PDCD4, BTG2, and NEDD4L. Inhibition of MIR21, MIR23A, and MIR27A had synergistic effects in reducing proliferation of PDAC cells in culture and growth of xenograft tumors in mice. The level of inhibition was greater than that of inhibition of MIR21 alone. In 91 PDAC samples from patients, high levels of a combination of MIR21, MIR23A, and MIR27A were associated with shorter survival times after surgical resection. CONCLUSIONS In an integrated data analysis, we identified functional miRNA-mRNA interactions that contribute to growth of PDACs. These findings indicate that miRNAs act together to promote tumor progression; therapeutic strategies might require inhibition of several miRNAs.

microRNAs with prognostic significance in pancreatic ductal adenocarcinoma: A meta-analysis.

BACKGROUND Reports have described the prognostic relevance of microRNAs (miRNAs) in patients treated for pancreatic ductal adenocarcinoma (PDAC). However, many of these include small numbers of patients. To increase statistical power and improve translation, we performed a systematic review and meta-analysis to determine a pooled conclusion. We examined the impact of miRNAs on overall survival (OS) and disease-free survival (DFS) in PDAC. METHODS Eligible studies were identified and quality assessed using multiple search strategies (last search December 2014). Data were collected from studies correlating clinical outcomes with dysregulated tumoural or blood miRNAs. Studies were pooled, and combined hazard ratios (HRs) with 95% confidence intervals (CIs) were used to estimate strength of the associations. RESULTS Twenty studies involving 1525 patients treated for PDAC were included. After correcting for publication bias, OS was significantly shortened in patients with high tumoural miR-21 (adjusted HR = 2.48; 1.96-3.14). This result persisted when only studies adjusting for adjuvant chemotherapy were combined (adjusted HR = 2.72; 1.91-3.89). High miR-21 also predicted reduced DFS (adjusted HR = 3.08; 1.78-5.33). Similarly, we found significant adjusted HRs for poor OS for high miR-155, high miR-203, and low miR-34a; and unadjusted HRs for high miR-222 and high miR-10b. The small number of studies, limited number of miRNAs and paucity of multivariate analyses are the limitations of our study. CONCLUSIONS This is the first rigorous pooled analysis assessing miRNAs as prognostic biomarkers in PDAC. Tumoural miR-21 overexpression emerged as an important predictor of poor prognosis after PDAC resection independent of other clinicopathologic factors, including adjuvant chemotherapy use.

Gene of the month: E-cadherin (CDH1).

Epithelial-cadherin (E-cadherin; encoded by CDH1 ) is a member of the classical cadherins (the others being neural cadherin (N-cadherin) and vascular endothelial cadherin (VE-cadherin)). These single-pass transmembrane glycoproteins are expressed by a variety of tissues and are involved in Ca2+-dependent cell–cell adhesion. Initially described as liver cell adhesion molecule in chickens1 and uvomorulin in mice,2 the name E-cadherin was first used by Takeichi and colleagues in the early 1980s.3 ,4 Since then its role in normal epithelial cell architecture and tissue formation, as well as a tumour suppressor gene in cancer development and progression, has been extensively studied. Cell–cell adhesions are vital to maintain the integrity of cells and cohesion of tissues, and the control of these junctions therefore plays an important part in tumourigenesis. E-cadherin mediates cell–cell contact at the basolateral membrane in adherens junctions and its expression is the hallmark of epithelial cell layers.5 This short review focuses on the structure and function of E-cadherin at the cell junction, including the cadherin–catenin complex and its involvement in epithelial-to-mesenchymal transition (EMT). Finally, the role of E-cadherin in cancer and the therapeutic implications are discussed. The CDH1 gene is located on chromosome 16q22.1, spanning a region of approximately 100 kb.6 CDH1 comprises 16 exons and 15 introns and is highly conserved between species.6 The resulting E-cadherin protein is a 120 kDa glycoprotein consisting of an extracellular domain of five tandem repeated domains, a cytoplasmic domain and a single transmembrane domain.7 ,8 The extracellular domain has binding sites for Ca2+ ions and extends from the cell surface to bind to cadherins on adjacent cells by lateral dimerisation.9 This allows a cadherin–cadherin interface and thus cell–cell adhesion. The cytoplasmic domain consists of the juxtamembrane domain (JMD) and the catenin-binding domain (CBD), each …

A microRNA meta-signature for pancreatic ductal adenocarcinoma

Evaluation of: Ma MZ, Kong X, Weng MZ et al. Candidate microRNA biomarkers of pancreatic ductal adenocarcinoma: meta-analysis, experimental validation and clinical significance. J. Exp. Clin. Cancer Res. 32(1), 71 (2013). Due to its aggressive and late presentation, there is an urgent need for novel and reliable biomarkers for the diagnosis and prognostication of pancreatic ductal adenocarcinoma (PDAC). MiRNAs have been extensively profiled in PDAC tissues, biopsies, blood samples and other biofluids and their expression levels compared to normal and chronic pancreatitis (CP) specimens in order to identify the most relevant candidates. Consolidation of these activities has not been attempted until now. The evaluated meta-review by Ma et al. helps to define the use of miRNAs as biomarkers for detecting this tumor-type and predicting survival outcomes in PDAC. Based on frequency and consistency between microarray studies, they identified a miRNA meta-signature for recognising PDAC: upregulation of miR-21, 23a, 31, 100, 143, 155, and 221; with downregulation of miR-148a, 217 and 375. Furthermore, they validated high miR-21, high miR-31 and low miR-375 tumoural expression as independently prognostic for poor overall-survival (OS; n = 70).

The p53 miRNA interactome and its potential role in the cancer clinic

p53 is one of the most frequently mutated tumor suppressors. It regulates protein-coding genes and noncoding RNAs involved in many cellular processes, functioning predominantly at the transcriptional level but also through nontranscriptional processes. miRNAs have recently been identified as key mediators of the p53 stress-response pathway. p53 regulates miRNA transcription and processing, and miRNAs regulate p53 activity and expression and, accordingly, various feedback/feed-forward loops have been identified. Many chemotherapeutic agents induce cancer cell death or senescence via DNA damage and the subsequent activation of p53. Resistance to chemotherapy can occur due to the mutation of components in p53 signaling networks. A better understanding of the role of the various components within these pathways and their interactions with each other may allow the modification and improvement of current treatments, and the design of novel therapies. Improving our knowledge of the role of miRNAs in such p53 signaling networks may be crucial to achieving this.

Integrated molecular analysis to investigate the role of microRNAs in pancreatic tumour growth and progression

BACKGROUND MicroRNAs (miRNAs) are small non-coding RNAs involved in the post-transcriptional regulation of mRNAs and are aberrantly expressed in cancer with important roles in tumorigenesis. A broad analysis of the combined effects of altered activities of miRNAs in pancreatic ductal adenocarcinoma (PDAC) has not been done, and how miRNAs might affect tumour progression or patient outcomes is unclear. METHODS We combined data from miRNA and mRNA expression profiles from PDAC and normal pancreas samples (each n=9) and used bioinformatic analyses to identify a miRNA-mRNA regulatory network in PDAC. We validated our findings in PDAC cell-lines (PANC-1, MIA PaCa-2, LPc006, and LPc167), subcutaneous PDAC xenografts in mice, and laser capture microdissected PDACs from patients (n=91). We used this information to identify miRNAs that contributed most to tumorigenesis. FINDINGS We identified three miRNAs (miR-21, miR-23a, and miR-27a) that acted as cooperative repressors of a network of tumour suppressor genes that included PDCD4, BTG2, and NEDD4L. Inhibition of miR-21, miR-23a, and miR-27a had synergistic effects in reducing proliferation of PDAC cells in culture and the growth of xenograft tumours. The level of inhibition was greater than that of silencing oncomiR-21 alone. In PDACs from patients, high levels of the combination of miR-21, miR-23a, and miR-27a was a strong independent predictor of short overall survival after surgical resection (hazard ratio 3·21, 95% CI 1·78-5·78). High expression of this combination was also associated with a more aggressive tumour phenotype: more microscopic tumour infiltration at resection margin and increased perineural invasion. INTERPRETATION In an integrated data analysis, we identified functional miRNA-mRNA interactions that contribute to PDAC growth. These findings indicate that miRNAs act together to promote tumour progression and that future therapeutic strategies might require inhibition of several miRNAs. Furthermore, high tumour expression of the miR-21, miR-23a, and miR-27a combination could have potential use in the future as a prognostic signature for patients with PDAC. FUNDING Peel Medical Research Trust, Alliance Family Foundation, Action Against Cancer, National Institute for Health Research, Association for International Cancer Research, Jason Boas Fellowship, Imperial Biomedical Research Centre, Rosetrees Trust, Joseph Ettedgui Charitable Foundation.

Pancreatic cancer: current management and treatment strategies.

The 5-year survival of patients with pancreatic cancer is poor and, despite oncological advances over the past two decades, has not significantly improved. However, there have been several surgical and oncological advances which have improved morbidity and mortality in surgery and more efficacious chemotherapy regimens, resulting in a better patient experience and an increase in survival by a number of months. Most patients have a tumour at the head of the pancreas and those with resectable disease undergo a pancreaticoduodenectomy, which can be performed laparoscopically. Those who have a pancreatic resection have an increased survival in comparison with those receiving oncological treatment only; however, only a quarter of patients have resectable disease at diagnosis. Some centres are now performing venous resections and/or arterial resections in order to increase the number of patients eligible for curative surgery. Innovative techniques using ablation technologies to downstage tumours for resection are also being investigated. After surgery, all patients should be offered adjuvant gemcitabine-based chemotherapy. Those with locally advanced tumours not suitable for surgery should be offered FOLFIRINOX chemotherapy, after which the tumour may be suitable for surgical resection. The use of radiotherapy in this group of patients is controversial but offered by a few centres. Patients with metastatic disease at diagnosis should also be offered FOLFIRINOX chemotherapy, which can improve survival by a few months. As our knowledge of the tumour biology of pancreatic cancer progresses, a number of new agents targeting specific genes and proteins are under investigation and there is hope that median survival will continue to improve over the next decade.

Mini-probe ultrasonography for the staging of colon cancer: a systematic review and meta-analysis

With an increasing array of treatment modalities available for colon cancer, it is increasingly important to stage tumours accurately to allocate the appropriate management. This study evaluated the accuracy of mini‐probe endoscopic ultrasound (EUS) in assigning clinical stage to colon cancer.

Towards a clinical use of miRNAs in pancreatic cancer biopsies

Evaluation of: Ali S, Saleh H, Sethi S, Sarkar FH, Philip PA. MicroRNA profiling of diagnostic needle aspirates from patients with pancreatic cancer. Br. J. Cancer 107(8), 1354–1360 (2012). Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease, despite advances in imaging, surgery and a greater understanding of its molecular biology. Patient outcomes remain poor due to an inability to detect disease early and resistance to anticancer treatments. miRNAs are promised to become ideal cancer biomarkers, as they are tumor and tissue specific and also incredibly stable molecules. So far, large profiling studies of the PDAC miRNome have identified the ‘usual suspects’ known to be deregulated in solid tumors, such as oncomiR-21, as well as others that could be more robust for differentiating malignant from benign pancreatic disease. However, many of these are yet to be validated clinically. The paper under evaluation provides further evidence for the use of miRNAs as diagnostic biomarkers for PDAC. We have reviewed the use of miRNAs as diagnostic analytes for detecting PDAC in biopsies.

Blood-based miRNAs as noninvasive diagnostic and surrogative biomarkers in colorectal cancer

Evaluation of: Kanaan Z, Rai SN, Eichenberger MR et al. Plasma MiR-21: a potential diagnostic marker of colorectal cancer. Ann. Surg. 256(3), 544–551 (2012). Few studies have assessed circulating miRNAs in the blood of colorectal cancer (CRC) patients. In the evaluated article, Kanaan et al. demonstrated that miR-21 may be a promising diagnostic plasma biomarker for CRC. They assessed miRNAs dysregulated in both tissue and blood samples from patients with CRC. A high-throughput microarray was used to first detect miRNAs deregulated in CRC compared with adjacent normal tissue. The three most upregulated and downregulated miRNAs were then measured in blood samples. Plasma miR-21 was able to correctly identify CRC with 90% specificity and sensitivity. In this article, we have considered the use of miRNAs as blood-based biomarkers for CRC.