MicroRNA-155 Controls Exosome Synthesis and Promotes Gemcitabine Resistance in Pancreatic Ductal Adenocarcinoma

Liquid biopsies for management of pancreatic cancer

Pancreatic cancer is one of the main causes of cancer-related deaths worldwide. It is asymptomatic at an early stage, and most diagnosis occurs when the disease is already at a late stage, by which time the tumor is nonresectable. In order to increase the overall survival of patients with pancreatic cancer, as well as to decrease the cancer burden, it is necessary to perform early diagnosis, prognosis stratifications and cancer monitoring using accurate, minimally invasive, and cost-effective methods. Liquid biopsies seek to detect tumor-associated biomarkers in a variety of extractable body fluids and can help to monitor treatment response and disease progression, and even predict patient outcome. In patients with pancreatic cancer, tumor-derived materials, primarily circulating tumor DNA, circulating tumor cells and exosomes, are being studied for inclusion in the management of the disease. This review focuses on describing the biology of these biomarkers, methods for their enrichment and detection, as well as their potential for clinical application. Moreover, we discuss the future direction of liquid biopsies and introduce how they can be exploited toward point of care personalized medicine for the management of pancreatic cancer.

Paclitaxel‑resistant gastric cancer MGC‑803 cells promote epithelial‑to‑mesenchymal transition and chemoresistance in paclitaxel‑sensitive cells via exosomal delivery of miR‑155‑5p

Paclitaxel is a first-line chemotherapeutic agent for gastric cancer; however, resistance limits its effectiveness. Investigation into the underlying mechanisms of paclitaxel resistance is urgently required. In the present study, a paclitaxel-resistant gastric cancer cell line (MGC-803R) was generated with a morphological phenotype of epithelial-to-mesenchymal transition (EMT) and increased expression levels of microRNA (miR)-155-5p. MGC-803R cell-derived exosomes were effectively taken up by paclitaxel-sensitive MGC-803S cells, which exhibited EMT and chemoresistance phenotypes. miR-155-5p was enriched in MGC-803R-exosomes and could be delivered into MGC-803S cells. miR-155-5p overexpression in MGC-803S cells via transfection with mimics resulted in similar phenotypic effects as treatment with MGC-803R exosome and increased miR-155-5p content in MGC-803S exosomes, which then capable of inducing the malignant phenotype in the sensitive cells. GATA binding protein 3 (GATA3) and tumor protein p53-inducible nuclear protein 1 (TP53INP1) were identified as targets of miR-155-5p. Exosomal miR-155-5p inhibited these targets by directly targeting their 3′ untranslated regions. Knockdown of miR-155-5p was observed to reverse the EMT and chemoresistant phenotypes of MGC-803R cells, potentially via GATA3 and TP53INP1 upregulation, which inhibited MGC-803R-exosomes from inducing the malignant phenotype. These results demonstrated that exosomal delivery of miR-155-5p may induce EMT and chemoresistant phenotypes from paclitaxel-resistant gastric cancer cells to the sensitive cells, which may be mediated by GATA3 and TP53INP1 suppression. Targeting miR-155-5p may thus be a promising strategy to overcome paclitaxel resistance in gastric cancer.

MiR-373-3p enhances the chemosensitivity of gemcitabine through cell cycle pathway by targeting CCND2 in pancreatic carcinoma cells

OBJECTIVE

This study aimed to detect the expression of miR-373-3p and CCND2 in gemcitabine-resistance pancreatic carcinoma (PC) cells, investigate the relationship between miR-373-3p and CCND2, and explore their effects on PC propagation, migration, invasion and apoptosis.

METHODS

R software was applied for analyzing differentially expressed genes (DEGs) in cell samples. The potential biological pathway was determined by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, based on R software. The gemcitabine-resistance PC cells were screened out using MTT assay, and they were applied in the next experiments. MiR-373-3p and CCND2 expression in GEM-PANC-1 cells were measured by qRT-PCR. After transfection, the expression of CCND2 protein was examined via western blot assay. Cells viability and apoptosis were confirmed by MTT proliferation assay and Flow cytometry, whereas cells migration and invasion were analyzed by transwell assay. The targeting relationship between miR-373-3p and CCND2 was identified by dual-luciferase reporter assay.

RESULTS

MiR-373-3p was found to be low expressed in GEM-PANC-1 cells while CCND2 was highly expressed in GEM-PANC-1 cells. MiR-373-3p negatively regulated CCND2 expression through KEGG_Cell_Cycle_Signaling_Pathway. The targeted relationship between miR-373-3p and CCND2 could be verified using dual luciferase reporter assay. MTT proliferation assay, transwell assay and Annexin V assay demonstrated that miR-373-3p suppressed GEM-PANC-1 cells propagation and invasion and promoted cell apoptosis, while CCND2 showed totally reverse effects compared with miR-373-3p. All the results suggested that miR-373-3p could enhance the chemosensitivity of GEM-PANC-1 cells by regulating CCND2.

CONCLUSION

MiR-373-3p inhibited cell propagation, migration and invasion and boosted apoptosis in gemcitabine resistance pancreatic carcinoma cells by targeting CCND2.

Hypoxia-Induced PLOD2 is a Key Regulator in Epithelial-Mesenchymal Transition and Chemoresistance in Biliary Tract Cancer

BACKGROUND

The prognosis of biliary tract cancer (BTC) is unfavorable due to its chemoresistance. Hypoxia triggers epithelial-to-mesenchymal transition (EMT), which is closely related to drug resistance. In this study, we focused on the functional roles of procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2), a hypoxia-induced gene, in BTC, and assessed the clinical significance of PLOD2.

METHODS

The expression of PLOD2 under hypoxia was assessed in BTC cell lines. Gemcitabine-resistant (GR) BTC cell lines were transfected with small interfering RNA (siRNA) against PLOD2, and EMT markers and chemoresistance were evaluated. PLOD2 expression was also characterized using immunohistochemistry in BTC clinical specimens following resection. Patient survival was analyzed and the role of PLOD2 expression was examined.

RESULTS

The expression of PLOD2 was induced by hypoxia in vitro and was upregulated in BTC-GR cell lines, which had low expression of epithelial markers and high expression of mesenchymal markers. Downregulation of PLOD2 by siRNA resulted in improved chemoresistance, recovery of epithelial markers, and reduction of mesenchymal markers. In the resected BTC samples, PLOD2 expression was significantly correlated with lymph node metastasis (p = 0.037) and stage (p = 0.001). Recurrence-free survival (p = 0.011) and overall survival (p < 0.001) rates were significantly lower in patients with high expression of PLOD2. PLOD2 expression was an independent prognostic factor for overall survival (p = 0.019).

CONCLUSIONS

The expression of PLOD2 influenced chemoresistance through EMT, and high expression of PLOD2 was a significant unfavorable prognostic factor in BTC patients. PLOD2 might be a potential therapeutic target for overcoming chemoresistance.

miR-125a-3p is responsible for chemosensitivity in PDAC by inhibiting epithelial-mesenchymal transition via Fyn. Biomed Pharmacother. 2018;106:523-531. [PMID: 29990840 DOI: 10.1016/j.biopha.2018.06.114]

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers and resistance to cytotoxic chemotherapy is the major cause of mortality in PDAC patients. miR-125a-3p was found to be down-regulated in PDAC cells; however, the function of miR-125a-3p in PDAC has been elusive. Here, we explored the role of miR-125a-3p in chemosensitivity in PDAC cells.

METHODS

We used qRT-PCR to detect miR-125a-3p expression in two PDAC cell lines. And we measured cell viability and apoptosis by MTT assay and flow cytometry, respectively. Scratch wound healing assay and transwell invasion assay were used to test the effects of miR-125a-3p and Fyn on cell EMT process. In addition, we validated the interaction of miR-125a-3p and Fyn by dual luciferase reporter assay. qRT-PCR and western blot were used to detect the mRNA and protein expressions of E-cadhrein, N-cadhrein, Snail and Fyn.

RESULTS

We found that miR-125a-3p was down-regulated in a time-dependent manner following treatment with gemcitabine in PDAC cells. Meanwhile, we found that overexpression of miR-125a-3p significantly increased chemosensitivity to gemcitabine and suppressed epithelial-mesenchymal transition (EMT) of PDAC cells. Mechanistically, miR-125a-3p directly targeted Fyn and decreased the expression of Fyn that functions to promote EMT process in PDAC. Furthermore, overexpression of Fyn could partially reverse the effects of miR-125a-3p on chemosensitivity to gemcitabine.

CONCLUSION

Our study is the first to show that miR-125a-3p is responsible for chemosensitivity in PDAC and could inhibit epithelial-mesenchymal transition by directly targeting Fyn. This provides a novel potential therapeutic strategy to overcome chemoresistance in PDAC.

Cisplatin induces the release of extracellular vesicles from ovarian cancer cells that can induce invasiveness and drug resistance in bystander cells

Ovarian cancer has a poor overall survival that is partly caused by resistance to drugs such as cisplatin. Resistance can be acquired as a result of changes to the tumour or due to altered interactions within the tumour microenvironment. Extracellular vesicles (EVs), small lipid-bound vesicles that are loaded with macromolecular cargo and released by cells, are emerging as mediators of communication in the tumour microenvironment. We previously showed that EVs mediate the bystander effect, a phenomenon in which stressed cells can communicate with neighbouring naive cells leading to various effects including DNA damage; however, the role of EVs released following cisplatin treatment has not been tested. Here we show that treatment of cells with cisplatin led to the release of EVs that could induce invasion and increased resistance when taken up by bystander cells. This coincided with changes in p38 and JNK signalling, suggesting that these pathways may be involved in mediating the effects. We also show that EV uptake inhibitors could prevent this EV-mediated adaptive response and thus sensitize cells in vitro to the effects of cisplatin. Our results suggest that preventing pro-tumourigenic EV cross-talk during chemotherapy is a potential therapeutic target for improving outcome in ovarian cancer patients.This article is part of the discussion meeting issue 'Extracellular vesicles and the tumour microenvironment'.

Exosomes and regenerative medicine: state of the art and perspectives

Exosomes have attracted the attention of the scientific community in recent years due to their widespread distribution, their possible functions as biomarkers of disease, and their great potential to be applied as therapeutic agents. Exosomes carry proteins and nucleic acids that can facilitate their uptake by distant target cells through endocytosis, such that exosomes could be targeted to a specific cell or cells to enhance or interfere with specific biological processes. This review will mainly focus on their roles in tissue repair and regenerative processes. Exosomal engineering and their potential applications in tissue regeneration are also reviewed here as an outlook for future research.

Liquid biopsy in pancreatic cancer: the beginning of a new era

With dismal survival rate pancreatic cancer remains one of the most aggressive and devastating malignancy. Predominantly, due to the absence of a dependable methodology for early identification and limited therapeutic options for advanced disease. However, it takes over 17 years to develop pancreatic cancer from initiation of mutation to metastatic cancer; therefore, if diagnosed early; it may increase overall survival dramatically, thus, providing a window of opportunity for early detection. Recently, genomic expression analysis defined 4 subtypes of pancreatic cancer based on mutated genes. Hence, we need simple and standard, minimally invasive test that can monitor those altered genes or their associated pathways in time for the success of precision medicine, and liquid biopsy seems to be one answer to all these questions. Again, liquid biopsy has an ability to pair with genomic tests. Additionally, liquid biopsy based development of circulating tumor cells derived xenografts, 3D organoids system, real-time monitoring of genetic mutations by circulating tumor DNA and exosome as the targeted drug delivery vehicle holds lots of potential for the treatment and cure of pancreatic cancer. At present, diagnosis of pancreatic cancer is frantically done on the premise of CA19-9 and radiological features only, which doesn't give a picture of genetic mutations and epigenetic alteration involved. In this manner, the current diagnostic paradigm for pancreatic cancer diagnosis experiences low diagnostic accuracy. This review article discusses the current state of liquid biopsy in pancreatic cancer as diagnostic and therapeutic tools and future perspectives of research in the light of circulating tumor cells, circulating tumor DNA and exosomes.

microRNA based prognostic biomarkers in pancreatic Cancer

Despite tremendous research efforts focused on diagnosis and treatment, pancreatic ductal adenocarcinoma remains the third leading cause of cancer-related death in the United States, with a 5-year overall survival rate of less than 5%. Although resistance is rather complex, emerging evidence has demonstrated that epigenetic alterations (e.g. miRNA) have important roles in PDAC progression as well as resistance to therapy. Certain miRNAs have been identified as potential prognostic biomarkers in PDAC. In this review, we summarize the recent developments in miRNA research related to PDAC therapeutic resistance mechanisms and the potential of miRNAs as prognostic biomarkers for future clinical management of PDAC.

The investigation of the survival time after recurrence in patients with pancreatic ductal adenocarcinoma for individualization of adjuvant chemotherapy

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease; however, the frequency of recurrence can be reduced if curative surgery following adjuvant chemotherapy is applied. At present, adjuvant chemotherapy is uniformly performed in all patients, as it is unclear which tumor types are controlled best or worst. We investigated patients with recurrence to establish the optimum treatment strategy.

METHODS

Of 138 patients who underwent curative surgery for PDAC, 85 developed recurrence. Comprehensive clinicopathological factors were investigated for their association with the survival time after recurrence (SAR).

RESULTS

The median SAR was 12.6 months. Treatments for recurrence included best supportive care, GEM-based therapy and S-1. The performance status [hazard ratio (HR) 0.12, P < 0.001], histological invasion of lymph vessels (HR 0.27, P < 0.001), kind of treatment for recurrence (HR 5.0, P < 0.001) and initial recurrence site (HR 2.9, P < 0.001) were independent significant risk factors for the SAR. The initial recurrence sites were the liver (n = 21, median SAR 8.8 months), lung (n = 10, 14.9 months), peritoneum (n = 6, 1.7 months), lymph nodes (n = 6, 14.7 months), local site (n = 17, 13.9 months) and multiple sites (n = 25, 10.1 months). A shorter recurrence-free survival (< 1 year) and higher postoperative CA19-9 level were significantly associated with critical recurrence (peritoneal/liver).

CONCLUSIONS

Several risk factors for SAR were detected in this study. Further investigations are needed to individualize the adjuvant chemotherapy for each patient with PDAC.

Molecular and cellular mechanisms of chemoresistance in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the most chemoresistant cancers, and current therapies targeting cancer-associated molecular pathways have not given satisfactory results, owing in part to rapid upregulation of alternative compensatory pathways. Most of the available treatments are palliative, focussing on improving the quality of life. At present, available options are surgery, embolization, radiation, chemotherapy, immunotherapy and use of other more targeted drugs. In this review, we describe the cellular and molecular effects of current chemotherapy drugs such as gemcitabine, FOLFIRINOX (5-fluorouracil [5-FU], oxaliplatin, irinotecan, and leucovorin) and ABRAXANE (nab-Paclitaxel), which have shown a survival benefit, although modest, for pancreatic cancer patients. Nevertheless, gemcitabine remains the standard first-line option for advanced-stage pancreatic cancer patients and, as resistance to the drug has attracted an increasing scientific interest, we deliberate on the main intracellular processes and proteins vital in acquired chemoresistance to gemcitabine. Lastly, our review examines various microenvironmental factors capable of instigating PDAC to develop resistance to chemotherapeutic drugs.

Circulating microRNAs as potential cancer biomarkers: the advantage and disadvantage

MicroRNAs are endogenous single-stranded non-coding small RNA molecules that can be secreted into the circulation and exist stably. They usually exhibit aberrant expression under different physiological and pathological conditions. Recently, differentially expressed circulating microRNAs were focused on as potential biomarkers for cancer screening. We herein review the role of circulating microRNAs for cancer diagnosis, tumor subtype classification, chemo- or radio-resistance monitoring, and outcome prognosis. Moreover, circulating microRNAs still have several issues hindering their reliability for the practical clinical application. Future studies need to elucidate further potential application of circulating microRNAs as specific and sensitive markers for clinical diagnosis or prognosis in cancers.

Exosomes in Pancreatic Cancer: from Early Detection to Treatment

BACKGROUND

Pancreatic cancer (PC) remains one of the most fatal forms of cancer worldwide with incidence nearly equal to mortality. This is often attributed to the fact that diagnosis is often not made until later disease stages when treatment proves difficult. Efforts have been made to reduce the mortality of PC through improvements in early screening techniques and treatments of late-stage disease. Exosomes, small extracellular vesicles involved in cellular communication, have shown promise in helping understand PC disease biology.

METHODS

In this review, we discuss current studies of the role of exosomes in PC physiology, and their potential use as diagnostic and treatment tools.

RESULTS

Exosomes have a role in diagnosing pancreatic cancer and in understanding tumor biology including migration, proliferation, chemoresistance, immunosuppression, cachexia and diabetes, and have a potential role in therapy for pancreatic cancer.

CONCLUSIONS

Exosomal analysis is beneficial in demonstrating mechanisms behind PC growth and metastasis, immunosuppression, drug resistance, and paraneoplastic conditions. Furthermore, the use of exosomes can be beneficial in detecting early-stage PC and exosomes have potential applications as therapeutic targets.

Role of exosomes in pancreatic cancer

Pancreatic cancer is one of the most lethal malignancies. Exosomes, which are released by multiple cell types, such as cancer cells, contain functional biomolecules (including proteins, nucleic acids and lipids) that can be horizontally delivered to recipient cells. Exosomes act as the most prominent mediator of intercellular communication and can regulate, instruct and re-educate their surrounding microenvironment and target specific organs. The present review performed an extensive search of multiple databases from 2005 to April 23 2017, for eligible literature relating to exosomes and their role in pancreatic cancer. With a focus on the latest findings for pancreatic cancer exosomes, their role in tumorigenesis was summarized, as well as their aggressive behaviors and their contribution to immunosuppression and therapy resistance in pancreatic cancer. In addition, the potential function of exosomes as novel diagnostic biomarkers is briefly discussed. Finally, we propose potential clinical applications for exosomes in pancreatic cancer.

Functional miRNAs in breast cancer drug resistance

Owing to improved early surveillance and advanced therapy strategies, the current death rate due to breast cancer has decreased; nevertheless, drug resistance and relapse remain obstacles on the path to successful systematic treatment. Multiple mechanisms responsible for drug resistance have been elucidated, and miRNAs seem to play a major part in almost every aspect of cancer progression, including tumorigenesis, metastasis, and drug resistance. In recent years, exosomes have emerged as novel modes of intercellular signaling vehicles, initiating cell–cell communication through their fusion with target cell membranes, delivering functional molecules including miRNAs and proteins. This review particularly focuses on enumerating functional miRNAs involved in breast cancer drug resistance as well as their targets and related mechanisms. Subsequently, we discuss the prospects and challenges of miRNA function in drug resistance and highlight valuable approaches for the investigation of the role of exosomal miRNAs in breast cancer progression and drug resistance.

Five key lncRNAs considered as prognostic targets for predicting pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, and the 5‐year survival rate was only 7.7%. To improve prognosis, a screening biomarker for early diagnosis of pancreatic cancer is in urgent need. Long non‐coding RNA (lncRNA) expression profiles as potential cancer prognostic biomarkers play critical roles in development of tumorigenesis and metastasis of cancer. However, lncRNA signatures in predicting the survival of a patient with PDAC remain unknown. In the current study, we try to identify potential lncRNA biomarkers and their prognostic values in PDAC. LncRNAs expression profiles and corresponding clinical information for 182 cases with PDAC were acquired from The Cancer Genome Atlas (TCGA). A total of 14 470 lncRNA were identified in the cohort, and 175 PDAC patients had clinical variables. We obtained 108 differential expressed lncRNA via R packages. Univariate and multivariate Cox proportional hazards regression, lasso regression was performed to screen the potential prognostic lncRNA. Five lncRNAs have been recognized to significantly correlate with OS. We established a linear prognostic model of five lncRNA (C9orf139, MIR600HG, RP5‐965G21.4, RP11‐436K8.1, and CTC‐327F10.4) and divided patients into high‐ and low‐risk group according to the prognostic index. The five lncRNAs played independent prognostic biomarkers of OS of PDAC patients and the AUC of the ROC curve for the five lncRNAs signatures prediction 5‐year survival was 0.742. In addition, targeted genes of MIR600HG, C9orf139, and CTC‐327F10.4 were explored and functional enrichment was also conducted. These results suggested that this five‐lncRNAs signature could act as potential prognostic biomarkers in the prediction of PDAC patient's survival.

High expression of microRNA-4295 contributes to cell proliferation and invasion of pancreatic ductal adenocarcinoma by the down-regulation of Glypican-5

A growing amount of evidence has documented that Glypican-5 (GPC5) is an important regulator of tumor progression. However, little is known about the role of GPC5 in pancreatic ductal adenocarcinoma (PDAC). In this study, we aimed to investigate the potential function and regulatory mechanism of GPC5 in PDAC. We found that GPC5 expression was significantly down-regulated in PDAC cell lines. The overexpression of GPC5 inhibited cell proliferation and the invasion of PDAC cells. In addition, the overexpression of GPC5 suppressed Wnt/β-catenin signaling in PDAC cells. Bioinformatic analysis predicted that GPC5 was a target gene of microRNA-4295 (miR-4295). The inhibition of miR-4295 significantly up-regulated the expression of GPC5. Moreover, the inhibition of miR-4295 inhibited the proliferation, invasion and Wnt/β-catenin signaling in PDAC cells. Notably, the knockdown of GPC5 partially reversed the anti-tumor effect of miR-4295 inhibition. Taken together, our results suggest GPC5 as a tumor suppressor in PDAC and its expression is possibly regulated by miR-4295. Our study indicates that the miR-4295/GPC5 axis may play an important role in the pathogenesis of PADC and has potential applications for the development of PDAC therapy.

The role of miRNAs in the diagnosis, chemoresistance, and prognosis of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains a very challenging malignancy with late presentation, metastatic potential, chemoresistance, and poor prognosis. Therefore, there is an urgent need for novel diagnostic and prognostic biomarkers. miRNAs are small noncoding RNAs that regulate the expression of multitude number of genes. Aberrant expression of miRNAs has been linked to the development of various malignancies, including PDAC. A series of miRNAs have been defined as holding promise for early diagnostics, as indicators of therapy resistance, and even as markers for prognosis in PDAC patients. In this review, we summarize the current knowledge on the role of miRNAs in diagnosis, chemoresistance, and prognosis in PDAC patients.

Exosome-mediated breast cancer chemoresistance via miR-155 transfer

Breast cancer remains the most prevalent cause of cancer mortality in woman worldwide due to the metastatic process and therapy resistance. Resistance against cancer therapy is partially attributed to cancer stem cells (CSCs). These cells arise from epithelial cells undergoing epithelial-to-mesenchymal transition (EMT) and might be responsible for tumor recurrence. In this study, we reported the relevance of miR-155 upregulation in chemoresistant cells associated with EMT. Notably, we found miR-155 induction in exosomes isolated from CSCs and resistant cells, followed by resistant cells’ exosome transfer to the recipient sensitive cells. Functionally, miR-155 mimic assay showed an enrichment in miR-155 from exosome concomitant with miR-155 exosome transfer to breast cancer cells. In parallel to these effects, we also observed EMT change in miR-155 transfected cells. The chemoresistance phenotype transfer to sensitive cells and the migration capability was analyzed by MTT and scratch assays and our results suggest that exosomes may intermediate resistance and migration capacity to sensitive cells partly through exosome transfer of miR-155. Taken together, our findings establish the significance of exosome-mediate miR-155 chemoresistance in breast cancer cells, with implications for targeting miR-155 signaling as a possible therapeutic strategy.

Extracellular vesicles as mediators of the progression and chemoresistance of pancreatic cancer and their potential clinical applications

Pancreatic cancer is one of the most lethal cancers worldwide due to its insidious symptoms, early metastasis, and chemoresistance. Hence, the underlying mechanisms contributing to pancreatic cancer progression require further exploration. Based on accumulating evidence, extracellular vesicles, including exosomes and microvesicles, play a crucial role in pancreatic cancer progression and chemoresistance. Furthermore, they also possess the potential to be promising biomarkers, therapy targets and tools for treating pancreatic cancer. Therefore, in-depth studies on the role of extracellular vesicles in pancreatic cancer are meaningful. In this review, we focus on the regulatory effects of extracellular vesicles on pancreatic cancer progression, metastasis, cancer-related immunity and chemoresistance, particularly their potential roles as biomarkers and therapeutic targets.

Pancreatic Cancer Diagnosis and Management: Has the Time Come to Prick the Bubble?

Pancreatic cancer (PC) is associated with poor prognosis and very dismal survival rates. The most effective possibility of cure is tumor resection, which is only possible in about 15% of patients diagnosed at early stages of disease progression. Recent whole-genome sequencing studies pointed genetic alterations in 12 core signaling pathways in PC. These observations hint at the possibility that the initial mutation in PC might appear nearly 20 years before any symptoms occur, suggesting that a large window of opportunity may exist for early detection. Biomarkers with the potential to identify pre-neoplastic disease or very early stages of cancer are of great promise to improve patient survival. The concept of liquid biopsy refers to a minimally invasive sampling and analysis of liquid biomarkers that can be isolated from body fluids, primarily blood, urine and saliva. A myriad of circulating molecules may be useful as tumor markers, including cell-free DNA (cfDNA), cell-free RNA (cfRNA), circulating tumor cells (CTC), circulating tumor proteins, and extracellular vesicles, more specifically exosomes. In this review, we discuss with more detail the potential role of exosomes in several aspects related to PC, from initiation to tumor progression and its applicability in early detection and treatment. Exosomes are small circulating extracellular vesicles of 50-150 nm in diameter released from the plasma membrane by almost all cells and exhibit some advantages over other biomarkers. Exosomes are central players of intercellular communication and they have been implicated in a series of biological process, including tumorigenesis, migration and metastasis. Several exosomal microRNAs and proteins have been observed to distinguish PC from benign pancreatic diseases and healthy controls. Besides their possible role in diagnosis, understanding exosomes functions in cancer has clarified the importance of microenvironment in PC progression as well as its influence in proliferation, metastasis and resistance to chemotherapy. Increasing knowledge on cancer exosomes provides valuable insights on new therapeutic targets and can potentially open new strategies to treat this disease. Continuous research is needed to ascertain the reliability of using exosomes and their content as potential biomarkers, so that, hopefully, in the near future, they will provide the opportunity for early diagnosis, treatment intervention and increase survival of PC patients.

Pharmacoepigenetics and pharmacoepigenomics of gastrointestinal cancers

Our understanding of the epigenetic changes occurring in gastrointestinal cancers has gained tremendous advancements in recent years, and some epigenetic biomarkers are already translated into the clinics for cancer diagnostics. In parallel, pharmacoepigenetics and pharmacoepigenomics of solid tumors are relevant novel, but emerging and promising fields. Areas covered: A comprehensive review of the literature to summarize and update the emerging field of pharmacoepigenetics and pharmacoepigenomics of gastrointestinal cancers. Expert commentary: Several epigenetic modifications have been proposed to account for interindividual variations in drug response in gastrointestinal cancers. Similarly, single-agent or combined strategies with high doses of drugs that target epigenetic modifications (epi-drugs) were scarcely tolerated by the patients, and current research has moved to their combination with standard therapies to achieve chemosensitization, radiosensitization, and immune modulation of cancerous cells. In parallel, recent genome-wide technologies are revealing the pathways that are epigenetically deregulated during cancer-acquired resistance, including those targeted by non-coding RNAs. Indeed, novel, less toxic, and more specific molecules are under investigation to specifically target those pathways. The field is rapidly expanding and gathering together information coming from these investigations has the potential to lead to clinical applications in the coming new years.

The role of exosomal non-coding RNAs in cancer metastasis. Oncotarget. 2018;9:12487-12502. [PMID: 29552328 PMCID: PMC5844764 DOI: 10.18632/oncotarget.23552]

An increasing number of studies has confirmed that many cells can secrete vesicles or exosomes in eukaryotes, which contain important nucleic acids, proteins and lipids and play important roles in cell communication and tumor metastasis. This paper summarizes the comprehensive function of exosomal non-coding RNAs. Although some studies have shown that exosomes mediate tumor signal transduction, the functional mechanism of the tumor metastasis remains to be elucidated. In this paper, we reviewed the role of exosomal non-coding RNAs in mediating cancer metastasis in the tumor microenvironment to provide new ideas for the study of tumor pathophysiology.

Secretory microRNAs as biomarkers of cancer

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression predominantly by inhibiting transcription and/or promoting degradation of target mRNAs also in addition to being involved in non-canonical mechanisms regulating transcription, translation and cell signaling processes. Extracellular secretory miRNAs, either in complex with specific proteins or encapsulated in microvesicles called exosomes, are transported between cells as means of intercellular communication. Secretory miRNAs in circulation remain functional after delivery to recipient cells, regulating target genes and their corresponding signaling pathways. Cancer cell secreted miRNA-mediated intercellular communication affects physiological processes associated with the disease, such as, angiogenesis, metabolic reprogramming, immune modulation, metastasis, and chemo-resistance. Given the stability of miRNAs in body fluids and their well-documented roles in deregulating cancer-relevant genetic pathways, there is considerable interest in developing secretory miRNAs as liquid biopsy biomarkers for detection, diagnosis and prognostication of cancer. In this review, we discuss salient features of miRNA biogenesis, secretion and function in cancer as well as the current state of secretory miRNA isolation and profiling methods. Furthermore, we discuss the challenges and opportunities of secretory miRNA biomarker assay development, which need to be addressed for clinical applications.

MicroRNA-410-3p attenuates gemcitabine resistance in pancreatic ductal adenocarcinoma by inhibiting HMGB1-mediated autophagy

Gemcitabine-based chemotherapy is the most common treatment option for pancreatic ductal adenocarcinoma (PDAC). However, it offers little therapeutic value in many cases due to the rapid development of chemoresistance. MicroRNAs (miRNAs) have been found to play pivotal roles in the chemotherapeutic resistance of PDAC. We found that miR-410-3p was significantly down-regulated in human pancreatic cancer xenograft (HPCx) tumor tissues from gemcitabine-treated mice. Low miR-410-3p expression correlated with gemcitabine resistance in HPCx tumors and PDAC cells as well as poor prognosis in PDAC patients. We also found that miR-410-3p attenuated the gemcitabine resistance of PDAC by targeting the 3'-UTR of HMGB1. Moreover, our study clearly demonstrated that miR-410-3p enhanced chemosensitivity to gemcitabine via inhibiting HMGB1-induced autophagy during chemotherapy in PDAC cells. Our study suggests that miR-410-3p expression may be a useful indicator of the potential for chemoresistance to gemcitabine and provide a potential new therapeutic target for chemoresistance in PDAC.

Mechanisms of Drug Resistance in Cancer: The Role of Extracellular Vesicles

Drug resistance remains a major barrier to the successful treatment of cancer. The mechanisms by which therapeutic resistance arises are multifactorial. Recent evidence has shown that extracellular vesicles (EVs) play a role in mediating drug resistance. EVs are small vesicles carrying a variety of macromolecular cargo released by cells into the extracellular space and can be taken up into recipient cells, resulting in transfer of cellular material. EVs can mediate drug resistance by several mechanisms. They can serve as a pathway for sequestration of cytotoxic drugs, reducing the effective concentration at target sites. They can act as decoys carrying membrane proteins and capturing monoclonal antibodies intended to target receptors at the cell surface. EVs from resistant tumor cells can deliver mRNA, miRNA, long noncoding RNA, and protein inducing resistance in sensitive cells. This provides a new model for how resistance that arises can then spread through a heterogeneous tumor. EVs also mediate cross-talk between cancer cells and stromal cells in the tumor microenvironment, leading to tumor progression and acquisition of therapeutic resistance. In this review, we will describe what is known about how EVs can induce drug resistance, and discuss the ways in which EVs could be used as therapeutic targets or diagnostic markers for managing cancer treatment. While further characterization of the vesiculome and the mechanisms of EV function are still required, EVs offer an exciting opportunity in the fight against cancer.

miR-155 mediates arsenic trioxide resistance by activating Nrf2 and suppressing apoptosis in lung cancer cells

Arsenic trioxide (ATO) resistance is a challenging problem in chemotherapy. However, the underlying mechanisms remain to be elucidated. In this study, we identified a high level of expression of miR-155 in a human lung adenocarcinoma A549R cell line that is highly resistant to ATO. We showed that the high level of miR-155 was associated with increased levels of cell survival, colony formation, cell migration and decreased cellular apoptosis, and this was mediated by high levels of Nrf2, NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1) and a high ratio of Bcl-2/Bax. Overexpression of the miR-155 mimic in A549R cells resulted in increased levels of colony formation and cell migration as well as reduced apoptosis along with increased Nrf2, NQO1 and HO-1. In contrast, silencing of miR-155 expression with its inhibitor in the cells, significantly decreased the cellular levels of Nrf2, NQO1 and HO-1 as well as the ratio of Bcl-2/Bax. This subsequently reduced the level of colony formation and cell migration facilitating ATO-induced apoptosis. Our results indicate that miR-155 mediated ATO resistance by upregulating the Nrf2 signaling pathway, but downregulating cellular apoptosis in lung cancer cells. Our study provides new insights into miR-155-mediated ATO resistance in lung cancer cells.

A microRNA cluster (let-7c, miRNA-99a, miRNA-125b, miRNA-155 and miRNA-802) encoded at chr21q21.1-chr21q21.3 and the phenotypic diversity of Down's syndrome (DS; trisomy 21)

Down's syndrome (DS) is the most common genetic cause of intellectual disability and cognitive deficit attributable to a naturally-occurring abnormality of gene dosage. DS is caused by a triplication of all or part of human chromosome 21 (chr21) and currently there are no effective treatments for this incapacitating disorder of neurodevelopment. First described by the English physician John Langdon Down in 1862, propelled by the invention of karyotype analytical techniques in the early 1950s and the discovery in 1959 by the French geneticist Jerome Lejune that DS resulted from an extra copy of chr21, DS was the first neurological disorder linking a chromosome dosage imbalance to a defect in intellectual development with ensuing cognitive disruption. Especially over the last 60 years, it has been repeatedly demonstrated that DS is not an easily defined disease entity but rather possesses a remarkably wide variability in the 'phenotypic spectrum' associated with this trisomic disorder. This commentary describes the presence of a 5 member cluster of chr21-encoded microRNAs (miRNAs) that includes let-7c, miRNA-99a, miRNA-125b, miRNA-155 and miRNA-802 located on the long arm of human chr21, spanning the chr21q21.1-chr21q21.3 region and flanking the beta amyloid precursor (βAPP) gene, and reviews the potential contribution of these 5 miRNAs to the remarkably diverse DS phenotype.

Patients Treated with Preoperative Chemoradiation for Pancreatic Ductal Adenocarcinoma have Impaired Bone Density, a Predictor of Distant Metastasis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a lethal neoplasm that spreads to surrounding tissue or distant sites. This study investigated distant metastases in PDAC patients with or without preoperative chemoradiation therapy (CRT), focusing on vitamin D levels and bone density.

METHODS

This study included 146 patients with PDAC who underwent surgery from 2007 to 2014. Bone density was evaluated using computed tomography, and the preoperative vitamin D level was calculated by enzyme-linked immunosorbent assay (ELISA) for patients with available plasma (48 cases).

RESULTS

When the patients were divided into two groups according to the change in bone density, the group with decreased bone density had a shorter distant metastasis-free survival time (DMFS) after surgery than the other group (p < 0.05). Low vitamin D was a weak predictor of DMFS, but the difference was not significant (p = 0.08), perhaps because of the sample size. Multivariate analysis indicated three significant factors associated with distant metastasis: a decrease in bone density (hazard ratio [HR], 2.17; p = 0.04), normalization of the Dupan-2 value after surgery (hazard ratio [HR], 0.39; p = 0.02), and completion of adjuvant chemotherapy (HR, 0.29; p < 0.01). Univariate analysis showed that a low vitamin D concentration (<20 pg/ml) was a risk factor (p = 0.04) for bone density change. Multivariate analysis found that preoperative CRT was the only factor associated (±, OR, 5.8; p = 0.04) with bone density change, suggesting that preoperative CRT significantly decreases bone density in patients with insufficient vitamin D.

CONCLUSION

Patients treated with preoperative CRT tend to have impaired bone density, which is a predictor of distant metastasis. Thus, vitamin D supplementation may decrease distant metastasis.

Chromosome 21-Encoded microRNAs (mRNAs): Impact on Down's Syndrome and Trisomy-21 Linked Disease

Down's syndrome (DS; also known as trisomy 21; T21) is caused by a triplication of all or part of human chromosome 21 (chr21). DS is the most common genetic cause of intellectual disability attributable to a naturally-occurring imbalance in gene dosage. DS incurs huge medical, healthcare, and socioeconomic costs, and there are as yet no effective treatments for this incapacitating human neurogenetic disorder. There is a remarkably wide variability in the 'phenotypic spectrum' associated with DS; the progression of symptoms and the age of DS onset fluctuate, and there is further variability in the biophysical nature of the chr21 duplication. Besides the cognitive disruptions and dementia in DS patients other serious health problems such as atherosclerosis, altered lipogenesis, Alzheimer's disease, amyotrophic lateral sclerosis (Lou Gehrig's disease), autoimmune disease, various cancers including lymphoma, leukemia, glioma and glioblastoma, status epilepticus, congenital heart disease, hypotonia, manic depression, prostate cancer, Usher syndrome, motor disorders, Hirschsprung disease, and various physical anomalies such as early aging occur at elevated frequencies, and all are part of the DS 'phenotypic spectrum.' This communication will review the genetic link between these fore-mentioned diseases and a small group of just five stress-associated microRNAs (miRNAs)-that include let-7c, miRNA-99a, miRNA-125b, miRNA-155, and miRNA-802-encoded and clustered on the long arm of human chr21 and spanning the chr21q21.1-chr21q21.3 region.