Exosome-Mediated Intercellular Communication Between Stellate Cells and Cancer Cells in Pancreatic Ductal Adenocarcinoma

METTL3 in cancer-associated fibroblasts-derived exosomes promotes the proliferation and metastasis and suppresses ferroptosis in colorectal cancer by eliciting ACSL3 m6A modification

BACKGROUND

Cancer-associated fibroblasts (CAFs) have been reported that can affect cancer cell proliferation, metastasis, ferroptosis, and immune escape. METTL3-mediated N6-methyladenine (m6A) modification is involved in the tumorigenesis of colorectal cancer (CRC). Herein, we investigated whether METTL3-dependent m6A in CAFs-derived exosomes (exo) affected CRC progression.

METHODS

qRT-PCR and western blotting analyses detected levels of mRNAs and proteins. Cell proliferation and metastasis were evaluated using MTT, colony formation, transwell, and wound healing assays, respectively. Cell ferroptosis was assessed by detecting cell viability and the levels of Fe+, reactive oxygen species, and glutathione after erastin treatment. Exosomes were isolated from CAFs by ultracentrifugation. The m6A modification profile was determined by methylated RNA immunoprecipitation assay and the interaction between METTL3 and ACSL3 (acyl-CoA synthetase 3) was verified using dual-luciferase reporter assay. Animal models were established for in vivo analysis.

RESULTS

CAFs promoted CRC cell proliferation and metastasis, and suppressed cell ferroptosis. METTL3 was enriched in CAFs and was packaged into exosomes. The m6A modification and METTL3 expression were increased in CRC samples. Knockdown of METTL3 in CAFs-exo suppressed CRC cell proliferation and metastasis, and induced cell ferroptosis. Mechanistically, METTL3 induced ACSL3 m6A modification and stabilized its expression. The anticancer effects mediated by METTL3-silenced CAFs-exo could be rescued by ACSL3 overexpression. Moreover, in vivo assay also showed that CAFs-exo with decreased METTL3 could hinder CRC growth and metastasis in mice models.

CONCLUSION

CAFs promoted the proliferation and metastasis, and restrained the ferroptosis in CRC by exosomal METTL3-elicited ACSL3 m6A modification.

Pancreatic stellate cells: Key players in pancreatic health and diseases (Review)

As a pluripotent cell, activated pancreatic stellate cells (PSCs) can differentiate into various pancreatic parenchymal cells and participate in the secretion of extracellular matrix and the repair of pancreatic damage. Additionally, PSCs characteristics allow them to contribute to pancreatic inflammation and carcinogenesis. Moreover, a detailed study of the pathogenesis of activated PSCs in pancreatic disease can offer promise for the development of innovative therapeutic strategies and improved patient prognoses. Therefore, the present study review aimed to examine the involvement of activated PSCs in pancreatic diseases and elucidate the underlying mechanisms to provide a viable therapeutic strategy for the management of pancreas‑related diseases.

A Comprehensive Review of the Potential Role of Liquid Biopsy as a Diagnostic, Prognostic, and Predictive Biomarker in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma is one of the most lethal malignant diseases, with a mortality rate being close to incidence. Due to its heterogeneity and plasticity, as well as the lack of distinct symptoms in the early phases, it is very often diagnosed at an advanced stage, resulting in poor prognosis. Traditional tissue biopsies remain the gold standard for making a diagnosis, but have an obvious disadvantage in their inapplicability for frequent sampling. Blood-based biopsies represent a non-invasive method which potentially offers easy and repeated sampling, leading to the early detection and real-time monitoring of the disease and hopefully an accurate prognosis. Given the urgent need for a reliable biomarker that can estimate a patient's condition and response to an assigned treatment, blood-based biopsies are emerging as a potential new tool for improving patients' survival and surveillance. In this article, we discuss the current advances and challenges in using liquid biopsies for pancreatic cancer, focusing on circulating tumour DNA (ctDNA), extracellular vesicles (EVs), and circulating tumour cells (CTCs), and compare the performance and reliability of different biomarkers and combinations of biomarkers.

Mesenchymal Stem Cell-Originated Exosomal Lnc A2M-AS1 Alleviates Hypoxia/Reperfusion-Induced Apoptosis and Oxidative Stress in Cardiomyocytes

BACKGROUND

Mesenchymal stem cell (MSC)-derived exosomes play significant roles in ameliorating cardiac damage after myocardial ischemia-reperfusion (I/R) injury. Long non-coding RNA alpha-2-macroglobulin antisense RNA 1 (Lnc A2M-AS1) was found that might protect against myocardial I/R. However, whether Lnc A2M-AS1 delivery via MSC-derived exosomes could also regulate myocardial I/R injury remains unknown.

METHODS

Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot. Hypoxia/reoxygenation (H/R) treatment in human cardiomyocytes was used to mimic the process of myocardial I/R in vitro. The viability and apoptosis of cardiomyocytes were detected using cell counting kit-8, flow cytometry, and Western blot assays. The contents of lactate dehydrogenase (LDH), malondialdehyde (MDA), and superoxide dismutase (SOD) were evaluated using corresponding commercial kits. The quantitative real-time polymerase chain reaction and Western blot were used to determine the expression levels of Lnc A2M-AS1, microRNA (miR)-556-5p, and X-linked inhibitor of apoptosis protein (XIAP). The binding interaction between miR-556-5p and Lnc A2M-AS1 or XIAP was confirmed by the dual-luciferase reporter, RIP and pull-down assays.

RESULTS

Exosomes isolated from hMSCs (hMSCs-exo) attenuated H/R-induced apoptosis and oxidative stress in cardiomyocytes. Lnc A2M-AS1 was lowly expressed in AMI patients and H/R-induced cardiomyocytes. Besides, Lnc A2M-AS1 was detectable in hMSCs-exo, exosomes derived from Lnc A2M-AS1-transfected hMSCs weakened H/R-induced apoptosis and oxidative stress, and enhanced the protective action of hMSCs-exo on H/R-induced cardiomyocytes. Further mechanism analysis showed that Lnc A2M-AS1 acted as a sponge for miR-556-5p to increase XIAP expression level. Importantly, miR-556-5p overexpression or XIAP knockdown reversed the action of exosomal Lnc A2M-AS1 on H/R-induced cardiomyocytes.

CONCLUSION

Lnc A2M-AS1 delivery via MSC-derived exosomes ameliorated H/R-induced cardiomyocyte apoptosis and oxidative stress via regulating miR-556-5p/XIAP, opening a new window into the pathogenesis of myocardial I/R injury.

Research progress of extracellular vesicles and exosomes derived from mesenchymal stem cells in the treatment of oxidative stress-related diseases

There is growing evidence that mesenchymal stem cell-derived extracellular vesicles and exosomes can significantly improve the curative effect of oxidative stress-related diseases. Mesenchymal stem cell extracellular vesicles and exosomes (MSC-EVs and MSC-Exos) are rich in bioactive molecules and have many biological regulatory functions. In this review, we describe how MSC-EVs and MSC-Exos reduce the related markers of oxidative stress and inflammation in various systemic diseases, and the molecular mechanism of MSC-EVs and MSC-Exos in treating apoptosis and vascular injury induced by oxidative stress. The results of a large number of experimental studies have shown that both local and systemic administration can effectively inhibit the oxidative stress response in diseases and promote the survival and regeneration of damaged parenchymal cells. The mRNA and miRNAs in MSC-EVs and MSC-Exos are the most important bioactive molecules in disease treatment, which can inhibit the apoptosis, necrosis and oxidative stress of lung, heart, kidney, liver, bone, skin and other cells, and promote their survive and regenerate.

CircRNA: A new class of targets for gastric cancer drug resistance therapy

Gastric cancer (GC) is one of the most common malignancies worldwide. Patients with advanced GC need palliative care to ensure survival. This includes the use of chemotherapy agents, such as cisplatin, 5-fluorouracil, oxaliplatin, paclitaxel, and pemetrexed, as well as targeted agents. However, the emergence of drug resistance evidence in poor patient outcomes and poor prognosis is a motivation to determine the specific mechanism of drug resistance. Interestingly, circular RNAs (circRNAs) play an important part in the carcinogenesis and progression of GC and are involved in GC drug resistance. This review systematically summarizes the functions and mechanisms of circRNAs underlying GC drug resistance, especially chemoresistance. It also emphasizes that circRNAs can serve as promising targets for improving drug resistance and therapeutic efficacy.

Exosome-mediated circTTLL5 transfer promotes hepatocellular carcinoma malignant progression through miR-136-5p/KIAA1522 axis

BACKGROUND

Exosomes have been recognized as messengers for intercellular communication in tumor microenvironment. Exosomal circRNAs are reported to be important in tumors. Here, this study identified the potential function of exosomal circular RNA tubulin tyrosine ligase like 5 (circTTLL5) in hepatocellular carcinoma (HCC) progression.

METHODS

The expression of circTTLL5, microRNA (miR)- 136-5p and KIAA1522 was detected using qRT-PCR and Western blot assays. Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy (TEM) and Western blot. Cell proliferation, apoptosis and metastasis were investigated using cell counting kit-8, colony formation, flow cytometry, would healing, transwell and Western blot assays, respectively. The interaction between miR-136-5p and circTTLL5 or KIAA1522 was confirmed by dual-luciferase reporter and pull-down assays. In vivo experiment was performed using Xenograft models.

RESULTS

CircTTLL5 was incorporated into exosomes and highly expressed in HCC tissues and cells. CircTTLL5 knockdown suppressed HCC cell proliferation and metastasis in vitro and impeded tumor growth in mice. CircTTLL5 could be delivered to recipient cells via exosomes, and treatment of circTTLL5-elevated exosomes could attenuate the anticancer effects of circTTLL5 knockdown on HCC in vitro and in vivo. Mechanically, circTTLL5 could sponge miR-136-5p, which controlled its down-stream target KIAA1522. MiR-136-5p inhibition reversed the effects of circTTLL5 knockdown on HCC cells. Besides that, miR-136-5p re-expression inhibited HCC cell growth and metastasis, which was abated by KIAA1522 overexpression.

CONCLUSION

Exosomal circTTLL5 promoted HCC progression through miR-136-5p/KIAA1522 axis, suggesting that blockage of the exosome-mediated transfer of circTTLL5 might be a therapeutic target for HCC.

A comparative Proteomics Analysis Identified Differentially Expressed Proteins in Pancreatic Cancer-Associated Stellate Cell Small Extracellular Vesicles

Human pancreatic stellate cells (HPSCs) are an essential stromal component and mediators of pancreatic ductal adenocarcinoma (PDAC) progression. Small extracellular vesicles (sEVs) are membrane-enclosed nanoparticles involved in cell-to-cell communications and are released from stromal cells within PDAC. A detailed comparison of sEVs from normal pancreatic stellate cells (HPaStec) and from PDAC-associated stellate cells (HPSCs) remains a gap in our current knowledge regarding stellate cells and PDAC. We hypothesized there would be differences in sEVs secretion and protein expression that might contribute to PDAC biology. To test this hypothesis, we isolated sEVs using ultracentrifugation followed by characterization by electron microscopy and Nanoparticle Tracking Analysis. We report here our initial observations. First, HPSC cells derived from PDAC tumors secrete a higher volume of sEVs when compared to normal pancreatic stellate cells (HPaStec). Although our data revealed that both normal and tumor-derived sEVs demonstrated no significant biological effect on cancer cells, we observed efficient uptake of sEVs by both normal and cancer epithelial cells. Additionally, intact membrane-associated proteins on sEVs were essential for efficient uptake. We then compared sEV proteins isolated from HPSCs and HPaStecs cells using liquid chromatography-tandem mass spectrometry. Most of the 1481 protein groups identified were shared with the exosome database, ExoCarta. Eighty-seven protein groups were differentially expressed (selected by 2-fold difference and adjusted p value ≤0.05) between HPSC and HPaStec sEVs. Of note, HPSC sEVs contained dramatically more CSE1L (chromosome segregation 1-like protein), a described marker of poor prognosis in patients with pancreatic cancer. Based on our results, we have demonstrated unique populations of sEVs originating from stromal cells with PDAC and suggest that these are significant to cancer biology. Further studies should be undertaken to gain a deeper understanding that could drive novel therapy.

Exosomes: the key of sophisticated cell-cell communication and targeted metastasis in pancreatic cancer

Pancreatic cancer is one of the most common malignancies. Unfortunately, the lack of effective methods of treatment and diagnosis has led to poor prognosis coupled with a very high mortality rate. So far, the pathogenesis and progression mechanisms of pancreatic cancer have been poorly characterized. Exosomes are small vesicles secreted by most cells, contain lipids, proteins, and nucleic acids, and are involved in diverse functions such as intercellular communications, biological processes, and cell signaling. In pancreatic cancer, exosomes are enriched with multiple signaling molecules that mediate intercellular communication with control of immune suppression, mutual promotion between pancreas stellate cells and pancreatic cancer cells, and reprogramming of normal cells. In addition, exosomes can regulate the pancreatic cancer microenvironment and promote the growth and survival of pancreatic cancer. Exosomes can also build pre-metastatic micro-ecological niches and facilitate the targeting of pancreatic cancer. The ability of exosomes to load cargo and target allows them to be of great clinical value as a biomarker mediator for targeted drugs in pancreatic cancer. Video Abstract.

Small extracellular vesicles: from mediating cancer cell metastasis to therapeutic value in pancreatic cancer

Pancreatic cancer is a highly malignant tumor and, is extremely difficult to diagnose and treat. Metastasis is one of the critical steps in the development of cancer and uses cell to cell communication to mediate changes in the microenvironment. Small extracellular vesicles (sEVs)-carry proteins, nucleic acids and other bioactive substances, and are important medium for communication between cells. There are two primary steps in sVEs-mediated metastasis: communication between pancreatic cancer cells and their surrounding microenvironment; and the communication between primary tumor cells and distant organ cells in distant organs that promotes angiogenesis, reshaping extracellular matrix, forming immunosuppressive environment and other ways to form appropriate pre-metastasis niche. Here, we explore the mechanism of localization and metastasis of pancreatic cancer and use sEVs as early biomarkers for the detection and treatment of pancreatic cancer. Video Abstract.

Pancreatic Cancer and Cellular Senescence: Tumor Microenvironment under the Spotlight

Pancreatic ductal adenocarcinoma (PDAC) has one of the most dismal prognoses of all cancers due to its late manifestation and resistance to current therapies. Accumulating evidence has suggested that the malignant behavior of this cancer is mainly influenced by the associated strongly immunosuppressive, desmoplastic microenvironment and by the relatively low mutational burden. PDAC develops and progresses through a multi-step process. Early in tumorigenesis, cancer cells must evade the effects of cellular senescence, which slows proliferation and promotes the immune-mediated elimination of pre-malignant cells. The role of senescence as a tumor suppressor has been well-established; however, recent evidence has revealed novel pro-tumorigenic paracrine functions of senescent cells towards their microenvironment. Understanding the interactions between tumors and their microenvironment is a growing research field, with evidence having been provided that non-tumoral cells composing the tumor microenvironment (TME) influence tumor proliferation, metabolism, cell death, and therapeutic resistance. Simultaneously, cancer cells shape a tumor-supportive and immunosuppressive environment, influencing both non-tumoral neighboring and distant cells. The overall intention of this review is to provide an overview of the interplay that occurs between senescent and non-senescent cell types and to describe how such interplay may have an impact on PDAC progression. Specifically, the effects and the molecular changes occurring in non-cancerous cells during senescence, and how these may contribute to a tumor-permissive microenvironment, will be discussed. Finally, senescence targeting strategies will be briefly introduced, highlighting their potential in the treatment of PDAC.

Plasma Exosomal CircNEK9 Accelerates the Progression of Gastric Cancer via miR-409-3p/MAP7 Axis

BACKGROUND

Exosome-mediated transfer of circular RNAs (circRNAs) is related to gastric cancer (GC) development. CircRNA NIMA-related kinase 9 (circNEK9; hsa_circ_0032683) was reported to be up-regulated in GC.

AIMS

The biological role of circNEK9 and its underlying mechanisms in GC progression were explored.

METHODS

The levels of RNAs and proteins were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot assay. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, colony formation assay, and flow cytometry. Wound healing assay and transwell assays were conducted to analyze cell motility. Intermolecular interaction was verified by dual-luciferase reporter assay and RNA pull-down assay. Animal experiments were used to evaluate the role of circNEK9 in the growth of xenograft tumors in vivo.

RESULTS

CircNEK9 was up-regulated in GC tissues and cell lines. CircNEK9 interference suppressed the proliferation and motility of GC cells. CircNEK9 silencing enhanced microRNA-409-3p (miR-409-3p) level through direct interaction. CircNEK9 silencing-mediated influences on the proliferation and metastasis of GC cells were partly overturned by the interference of miR-409-3p. MiR-409-3p directly interacted with microtubule-associated protein 7 (MAP7) messenger RNA (mRNA). MiR-409-3p-induced effects in GC cells were largely counteracted by the overexpression of MAP7. CircNEK9 silencing blocked GC tumor growth in vivo. Exosome-mediated transfer of circNEK9 promoted the motility of recipient GC cells.

CONCLUSIONS

CircNEK9 accelerated the proliferation, migration, and invasion of GC cells through targeting miR-409-3p/MAP7 axis. Plasma exosomal circNEK9 promoted the migration and invasion of recipient GC cells.

Circ_0046600 promotes hepatocellular carcinoma progression via up-regulating SERBP1 through sequestering miR-1258

BACKGROUND

Circ_0046600 was reported to promote hepatocellular carcinoma (HCC) cell migratory ability. However, the functional roles and mechanism of circ_0046600 in HCC remain largely unknown.

METHODS

Levels of genes and proteins were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. In vitro experiments were performed using cell counting kit-8 (CCK-8), colony formation, transwell, flow cytometry and Western blot assays, respectively. The direct interactions between miR-1258 and circ_0046600 or SERPINE1 mRNA-binding protein 1 (SERBP1) was verified using dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Xenograft tumor model was established to perform in vivo assay. Exosomes were obtained from culture media by using the commercial kit.

RESULTS

Circ_0046600 was highly expressed in HCC tissues and cells. Silencing of circ_0046600 impaired HCC cell growth and metastasis in vitro, as well as impeded HCC tumor growth in vivo. Mechanistically, circ_0046600 could competitively target miR-1258 to prevent the degradation of its target gene SERBP1. Rescue assay showed that miR-1258 inhibition reversed the inhibitory effects of circ_0046600 silencing on HCC cell. Moreover, ectopic overexpression of miR-1258 suppressed cell growth and metastasis in HCC, which was abolished by SERBP1 up-regulation. Furthermore, circ_0046600 was packaged into exosomes and could be derived from HCC cells.

CONCLUSION

Circ_0046600 promoted HCC progression via up-regulating SERBP1 through sequestering miR-1258; besides that, circ_0046600 was packaged into exosomes and could be released from HCC cells.

Cancer cell-derived exosomal circUSP7 induces CD8+ T cell dysfunction and anti-PD1 resistance by regulating the miR-934/SHP2 axis in NSCLC

Background

CD8⁺ T cells play a critical role in the innate antitumour immune response. Recently, CD8⁺ T cell dysfunction has been verified in various malignant cancers, including non-small cell lung cancer (NSCLC). However, the molecular biological mechanisms of CD8⁺ T cell dysfunction in human NSCLC are still unclear.

Methods

The expression of circular ubiquitin-specific protease-7 (circUSP7) in NSCLC tissues, exosomes, and cell lines was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Exosomes were isolated from the culture medium of NSCLC cells and the plasma of NSCLC patients using an ultracentrifugation method and the ExoQuick Exosome Precipitation Solution kit. The exosomes were then characterized by transmission electronic microscopy (TEM), NanoSight and western blotting. The role of circUSP7 in CD8⁺ T cell dysfunction was assessed by enzyme-linked immunosorbent assay (ELISA). In vivo circular RNA (circRNA) precipitation (circRIP), RNA immunoprecipitation (RIP), and luciferase reporter assays were performed to explore the molecular mechanisms of circUSP7 in CD8⁺ T cells. In a retrospective study, the clinical characteristics and prognostic significance of circUSP7 in NSCLC tissues were determined.

Results

The expression levels of circUSP7 were higher in human NSCLC tissues than in matched adjacent nontumour tissues. Increased levels of circUSP7 indicate poor clinical prognosis and CD8⁺ T cell dysfunction in patients with NSCLC. The circUSP7 found in NSCLC patient plasma is predominantly secreted by NSCLC cells in an exosomal manner, and circUSP7 inhibits IFN-γ, TNF-α, Granzyme-B and Perforin secretion by CD8⁺ T cells. Furthermore, circUSP7 inhibits CD8⁺ T cell function by upregulating the expression of Src homology region 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2) via sponging miR-934. Finally, we show that circUSP7 may promote resistance to anti-PD1 immunotherapy in NSCLC patients.

Conclusions

Exosomal circUSP7 is predominantly secreted by NSCLC cells and contributes to immunosuppression by promoting CD8⁺ T cell dysfunction in NSCLC. CircUSP7 induces resistance to anti-PD1 immunotherapy, providing a potential therapeutic strategy for NSCLC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-021-01448-x.

Exosomes Derived from lncRNA TCTN2-Modified Mesenchymal Stem Cells Improve Spinal Cord Injury by miR-329-3p/IGF1R Axis

Mesenchymal stem cells (MSCs)-derived exosomes play significant roles in alleviating spinal cord injury (SCI). Previous study showed that long non-coding RNA tectonic family member 2 (TCTN2) was able to relieve SCI. Herein, whether TCTN2 exerted its roles in functional recovery after SCI via exosomes derived from MSCs was explored. The SCI model was established in rats, and the neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) scoring. Lipopolysaccharide (LPS)-induced differentiated PC12 cells were used as an in vitro model for neurotoxicity research. The expression of genes and proteins was detected by qRT-PCR and Western blot. Exosomes were isolated by ultracentrifugation and qualified by TEM and Western blot. In vitro assays were performed using CCK-8 assay, EdU assay, and flow cytometry, respectively. Dual-luciferase reporter assay and RIP assay were used to confirm the target relationship between miR-329-3p and TCTN2 or insulin-like growth factor1 receptor (IGF1R). TCTN2 expression was down-regulated in SCI model rat and lipopolysaccharide (LPS)-stimulated PC12 cells. MSCs produced exosomes and could package TCTN2 into secreted exosomes. Tail vein injection of TCTN2 exosomes into rats significantly improved functional recovery of SCI. Meanwhile, TCTN2 exosomes treatment alleviated LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro. Additionally, TCTN2 targeted miR-329-3p and subsequently regulated the expression of its target IGF1R. Rescue assays suggested that miR-329-3p/IGF1R axis mediated the beneficial effects of TCTN2 exosomes on LPS-treated PC12 cells. In all, exosomes derived from TCTN2-modified MSCs could improve functional recovery of SCI in vivo and attenuate LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro via miR-329-3p/IGF1R axis, suggesting a novel insight into the development of MSC-exosomes-based therapy for SCI.

Circ-SKA3 Enhances Doxorubicin Toxicity in AC16 Cells Through miR-1303/TLR4 Axis

Doxorubicin (DOX) is a widely used anticancer drug, but its cardiotoxicity largely limits its clinical utilization. Circular RNA spindle and kinetochore-associated protein 3 (circ-SKA3) were found to be differentially expressed in heart failure patients. In this study, we investigated the role and mechanism of circ-SKA3 in DOX-induced cardiotoxicity.The quantitative real-time polymerase chain reaction and western blot assays were applied to measure the expression of circ-SKA3, microRNA (miR) -1303, and toll-like receptor 4 (TLR4). The viability and apoptosis of AC16 cells were analyzed using cell counting kit-8, flow cytometry, and western blot assays. The interaction between miR-1303 and circ-SKA3 or TLR4 was verified using dual-luciferase reporter and RNA immunoprecipitation assays. Exosomes were collected from culture media by the use of commercial kits and then qualified by transmission electron microscopy.The expression of circ-SKA3 and TLR4 was increased, whereas miR-1303 expression was decreased in DOX-treated AC16 cells. DOX treatment promoted cell apoptosis and inhibited cell viability in AC16 cells in vitro, which was partially reversed by circ-SKA3 knockdown, TLR4 silencing, or miR-1303 overexpression. Mechanistically, circ-SKA3 served as a sponge for miR-1303 to upregulate TLR4, which was confirmed to be a target of miR-1303. Additionally, circ-SKA3 contributed to DOX-induced cardiotoxicity through the miR-1303/TLR4 axis. Further studies suggested that circ-SKA3 was overexpressed in exosomes extracted from DOX-mediated AC16 cells, which could be internalized by surrounding untreated AC16 cells.Circ-SKA3 enhanced DOX-induced toxicity in AC16 cells through the miR-1303/TLR4 axis. Extracellular circ-SKA3 was packaged into exosomes, and exosomal circ-SKA3 could function as a mediator in intercellular communication between AC16 cells.

Pancreatic Cancer Small Extracellular Vesicles (Exosomes): A Tale of Short- and Long-Distance Communication

Simple Summary

Even today, pancreatic cancer still has a dismal prognosis. It is characterized by a lack of early symptoms and thus late diagnosis as well as early metastasis. The majority of patients suffer from pancreatic ductal adenocarcinoma (PDAC). PDACs communicate extensively with cellular components of their microenvironment, but also with distant metastatic niches to facilitate tumor progression and dissemination. This crosstalk is substantially enabled by small extracellular vesicles (sEVs, exosomes) with a size of 30–150 nm that are released from the tumor cells. sEVs carry bioactive cargos that reprogram target cells to promote tumor growth, migration, metastasis, immune evasion, or chemotherapy resistance. Interestingly, sEVs also carry novel diagnostic, prognostic and potentially also predictive biomarkers. Moreover, engineered sEVs may be utilized as therapeutic agents, improving treatment options. The role of sEVs for PDAC development, progression, diagnosis, prognosis, and treatment is the focus of this review.

Abstract

Even with all recent advances in cancer therapy, pancreatic cancer still has a dismal 5-year survival rate of less than 7%. The most prevalent tumor subtype is pancreatic ductal adenocarcinoma (PDAC). PDACs display an extensive crosstalk with their tumor microenvironment (TME), e.g., pancreatic stellate cells, but also immune cells to regulate tumor growth, immune evasion, and metastasis. In addition to crosstalk in the local TME, PDACs were shown to induce the formation of pre-metastatic niches in different organs. Recent advances have attributed many of these interactions to intercellular communication by small extracellular vesicles (sEVs, exosomes). These nanovesicles are derived of endo-lysosomal structures (multivesicular bodies) with a size range of 30–150 nm. sEVs carry various bioactive cargos, such as proteins, lipids, DNA, mRNA, or miRNAs and act in an autocrine or paracrine fashion to educate recipient cells. In addition to tumor formation, progression, and metastasis, sEVs were described as potent biomarker platforms for diagnosis and prognosis of PDAC. Advances in sEV engineering have further indicated that sEVs might once be used as effective drug carriers. Thus, extensive sEV-based communication and applications as platform for biomarker analysis or vehicles for treatment suggest a major impact of sEVs in future PDAC research.

ADSC Exosomes Mediate lncRNA-MIAT Alleviation of Endometrial Fibrosis by Regulating miR-150-5p

Background

Secondary infertility remains a major complication of endometrial fibrosis in women. The use of exosomes from adipose-derived mesenchymal stem cells (ADSCs) has shown promising results for the treatment of endometrial fibrosis. However, the mechanisms of action of ADSC-exosome (ADSC-Exo) therapy remain unclear.

Materials and Methods

An endometrial fibrosis model was established in mice treated with alcohol and endometrial epithelial cells (ESCs) treated with TGF-β1. ADSCs were isolated from Sprague Dawley (SD) rats, and exosomes were isolated from ADSCs using ExoQuick reagent. Exosomes were identified by transmission electron microscopy (TEM), NanoSight, and Western blot analysis. The expression level of lncRNA-MIAT was detected by qPCR analysis. Western blot analysis was carried out to determine the protein levels of fibrosis markers (TGFβR1, α-SMA, and CK19). A dual-luciferase reporter gene assay was used to verify the relationship between target genes. The endometrial tissues of the endometrial fibrosis model were stained with HE and Masson’s trichrome.

Results

ADSCs and ADSC-Exos were successfully isolated, and the expression level of lncRNA-MIAT was significantly down-regulated in endometrial tissue and the TGF-β1-induced ESC injury model, whereas ADSC-Exos increased the expression of lncRNA-MIAT in the TGF-β1-induced ESC model. Functionally, ADSC-Exo treatment repressed endometrial fibrosis in vivo and in vitro by decreasing the expression of hepatic fibrosis markers (α-SMA and TGFβR1) and increasing the expression of CK19. Moreover, miR-150-5p expression was repressed by lncRNA-MIAT in the TGF-β1-induced ESC injury model. The miR-150-5p mimic promoted TGF-β1-induced ESC fibrosis.

Conclusion

ADSC-Exos mediate lncRNA-MIAT alleviation of endometrial fibrosis by regulating miR-150-5p, which suggests that lncRNA-MIAT from ADSC-Exos may be a viable treatment for endometrial fibrosis.

Cyr61 from adipose-derived stem cells promotes colorectal cancer metastasis and vasculogenic mimicry formation via integrin αV β5

Adipose‐derived stem cells (ADSCs) play a vital role in colorectal cancer (CRC) progression, but the mechanism remains largely unknown. Herein, we found that ADSCs isolated from CRC patients produced more cysteine‐rich 61 (Cyr61) than those from healthy donors, and the elevated serum Cyr61 levels were associated with advanced TNM stages. Moreover, serum Cyr61 displayed a better diagnostic value for CRC compared to carcinoembryonic antigen (CEA) and carbohydrate antigen (CA19‐9). Mechanistically, integrin α_Vβ₅ was identified as the functional receptor by which Cyr61 promotes CRC cell metastasis in vitro and in vivo by activating the α_Vβ₅/FAK/NF‐κB signaling pathway. In addition, Cyr61 promotes vasculogenic mimicry (VM) formation, thereby promoting tumor growth and metastasis through a α_Vβ₅/FAK/HIF‐1α/STAT3/MMP2 signaling cascade. Histologically, xenografts and clinical samples of CRC both exhibited VM, which was correlated with HIF‐1α and MMP2 activation. Notably, we demonstrated the synergistic effect of combined anti‐VM therapy (integrin α_Vβ₅ inhibitor) and anti‐VEGF therapy (bevacizumab) in patient‐derived xenograft models. Further investigation showed that CRC cell‐derived exosomal STAT3 promoted Cyr61 transcription in ADSCs. These findings indicate that Cyr61 derived from ADSCs plays a critical role in promoting CRC progression via integrin α_Vβ₅ and provides a novel antitumor strategy by targeting Cyr61/α_Vβ₅.

Hypoxic pancreatic stellate cell-derived exosomal mirnas promote proliferation and invasion of pancreatic cancer through the PTEN/AKT pathway

Pancreatic stellate cells (PSCs) are important components of the tumor microenvironment in pancreatic cancer (PC) and contribute to its development and metastasis through mechanisms that remain incompletely characterized. Tumor hypoxia affects the function and behavior of PC and stromal cells, and can alter exosomal content to modify cell-cell communication. The present study explored the effects of exosomal miRNAs produced by hypoxia-preconditioned PSCs on the growth and metastatic potential of PC cells. Subcutaneous xenografts and liver metastasis mouse models revealed increased tumorigenic potential upon co-implantation of PC cells and PSCs as compared to PC cells alone. Screening miRNA profiles of mouse plasma exosomes and cultured PSCs, followed by miRNA overexpression and inhibition assays, enabled us to identify miR-4465 and miR-616-3p as prominent hypoxia-induced, PSC-derived, exosomal miRNAs promoting PC cell proliferation, migration, and invasion. Proteomics analysis of PC cells incubated with exosomes derived from hypoxic PSCs showed significant downregulation of PTEN. Dual-luciferase reporter assays and western blotting showed that both miR-4465 and miR-616-3p target PTEN and activate AKT signaling in PC cells. We conclude that hypoxia upregulates miR-4465 and miR-616-3p expression in PSC-derived exosomes. Following exosome uptake, these miRNAs promote PC progression and metastasis by suppressing the PTEN/AKT pathway.

Pancreatic Stellate Cells: The Key Orchestrator of The Pancreatic Tumor Microenvironment

Pancreatic cancer is one of the most challenging adenocarcinomas due to its hostile molecular behavior and complex tumor microenvironment. It has been recently postulated that pancreatic stellate cells (PSCs), the resident lipid-storing cells of the pancreas, are important components of the tumor microenvironment as they can transdifferentiate into highly proliferative myofibroblasts in the context of tissue injury. Targeting tumor-stromal crosstalk in the tumor microenvironment has emerged as a promising therapeutic strategy against pancreatic cancer progression and metastasis. This chapter brings a broad view on the biological and pathological role of PSCs in the pancreas, activated stellate cells in the onset of tissue fibrosis, and tumor progression with particular emphasis on the bidirectional interactions between tumor cells and PSCs. Further, potential therapeutic regimens targeting activated PSCs in the pre-clinical and clinical trials are discussed.

Circular RNA circ-RanGAP1 regulates VEGFA expression by targeting miR-877-3p to facilitate gastric cancer invasion and metastasis

The biological functions of circular RNAs (circRNAs) in gastric cancer (GC) remain largely unexplored. Here, we identified that circ-RanGAP1 was significantly upregulated in both GC tissues and exosomes from the plasma of GC patients. High circ-RanGAP1 expression was closely associated with an advanced TNM stage, lymph node metastases, and worse survival. Inhibition of circ-RanGAP1 decreased GC cell invasion and migration in vitro. Overexpression of circ-RanGAP1 had the opposite effect. Additionally, circ-RanGAP1 silencing remarkably suppressed tumor growth and metastasis of GC in vivo. Mechanistically, circ-RanGAP1 sponged miR-877-3p to upregulate VEGFA expression. Overexpression of miR-877-3p reversed the biological functions mediated by circ-RanGAP1 in GC cells. Interestingly, we demonstrated that circ-RanGAP1 was upregulated in plasma exosomes from preoperative GC patients. More importantly, the plasma exosomes derived from these patients enhanced the migration and invasion potential of GC cells. Overall, the circ-RanGAP1-mediated miR-877-3p/VEGFA axis promotes GC progression. Our findings suggest that circ-RanGAP1 might act as a potential prognostic biomarker and therapeutic target for GC treatment.

Exosomes as Carriers for Antitumor Therapy

Exosomes are bilayer vesicles with particle sizes between 50 and 150 nm. Owing to their bilayer membrane structure, cell-to-cell communication, and good absorbability, exosomes are increasingly used as carriers for drug delivery through phospholipid membrane structures to lesion sites with enhanced targeting. Exosome sources and drug-loading methods are important factors affecting their use as drug carriers. There are various ways to pack species in exosomes, and researchers are constantly seeking new and improved approaches. In both in vivo and in vitro evaluations, exosomal vectors have achieved good antitumor efficacies. Despite the importance of exosomes as drug delivery systems with accurate targeting ability and biocompatibility, improvements are needed to facilitate their widespread clinical use. This review focuses on the preparation of exosomes as carriers and their utilization in antitumor research.

Targeting Pancreatic Stellate Cells in Cancer

Pancreatic stellate cells (PSCs) are the major contributor to the aggressive, metastatic, and resilient nature of pancreatic ductal adenocarcinoma (PDAC), which has a poor prognosis with a 5-year survival rate of 8%. PSCs constitute more than 50% of the tumor stroma in PDAC, where they induce extensive desmoplasia by secreting abundant extracellular matrix (ECM) proteins. In addition, they establish dynamic crosstalk with cancer cells and other stromal cells, which collectively supports tumor progression via various inter- and intracellular pathways. These cellular interactions and associated pathways may reveal novel therapeutic opportunities against this unmet clinical problem. In this review article, we discuss the role of PSCs in inducing tumor progression, their crosstalk with other cells, and therapeutic strategies to target PSCs.

Drug-loaded exosomal preparations from different cell types exhibit distinctive loading capability, yield, and antitumor efficacies: a comparative analysis

Background

Despite tremendous advancement, cancer still remains one of the leading causes of death worldwide. Inefficiency of current drug delivery regimens is one important factor that limits the therapeutic efficacy of existing drugs, thus contributing to cancer mortality. To address this limitation, synthetic nanotechnology-based delivery systems have been developed; however, they raise concern of inducing adverse immunogenic reactions. Exosomes (Exos) are nonimmunogenic nanosized vesicles that have received significant attention as efficient drug delivery system.

Methods

Drug loading in Exos were achieved by incubating different cell types viz pancreatic cancer cells (PCCs), pancreatic stellate cells (PSCs), and macrophages (MØs) with Doxorubicin (DOX). Differential ultracentrifugation was performed to isolate exosome and their size was determined by dynamic light scattering analysis. The efficacy of drug packaging into Exos was evaluated by HPLC. Flow cytometry was performed to examine the apoptosis. Cell viability was determined using the WST-1 assay.

Results

PCCs shed the most Exos and were the most efficient in drug loading followed by MØs and PSCs as examined by HPLC quantification. However, when compared for antitumor efficacy, MØ-derived Exos loaded with DOX (MØ-Exo-DOX) showed highest activity followed by PSCs and PCCs.

Conclusion

These varying antitumor activities likely resulted from nondrug contents of Exos since we did not observe any significant differences in their uptake by the cancer cells. Altogether, our data suggest that donor cell-specific differences exist in Exos, which could influence their utility as drug carrier for therapeutic purposes.

Emerging Evidence for the Clinical Relevance of Pancreatic Cancer Exosomes

The last 5 years have seen a dramatic increased interest in the field of exosome biology. Although much is unknown about the role of exosomes in human health and disease, disparate scientific disciplines are recognizing the highly conserved role that exosomes play in fundamental biological processes. Recently, there have been intriguing discoveries defining the role of exosomes in cancer biology. We performed a structured review of the English-language literature using the PubMed database searching for articles relating to exosomes and pancreatic ductal adenocarcinoma (PDAC). Articles were screened for relevance and content to judge for inclusion. Evidence implicates exosomes in the pathogenesis, local progression, metastasis, immune evasion, and intercellular communication of PDAC. Basic science discoveries in exosome biology have the potential to change the clinical management of PDAC, where, despite advances in early detection, diagnosis, staging, chemotherapy, and surgery, survival rates have been stagnant for decades and PDAC remains the most deadly human gastrointestinal malignancy.

AHIF promotes glioblastoma progression and radioresistance via exosomes

Glioblastoma multiforme (GBM) has the highest mortality rate among patients with brain tumors, and radiotherapy forms an important part of its treatment. Thus, there is an urgent requirement to elucidate the mechanisms conferring GBM progression and radioresistance. In the present study, it was identified that antisense transcript of hypoxia‑inducible factor‑1α (AHIF) was significantly upregulated in GBM cancerous tissues, as well as in radioresistant GBM cells. The expression of AHIF was also upregulated in response to radiation. Knockdown of AHIF in GBM cells decreased viability and invasive capacities, and increased the proportion of apoptotic cells. By contrast, overexpression of AHIF in GBM cells increased viability and invasive capacities, and decreased the proportion of apoptotic cells. Furthermore, exosomes derived from AHIF‑knockdown GBM cells inhibited viability, invasion and radioresistance, whereas exosomes derived from AHIF‑overexpressing GBM cells promoted viability, invasion and radioresistance. Further biochemical analysis identified that AHIF regulates factors associated with migration and angiogenesis in exosomes. To the best of our knowledge, the present study is the first to establish that AHIF promotes glioblastoma progression and radioresistance via exosomes, which suggests that AHIF is a potential therapeutic target for GBM.

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.

Pancreatic cancer and associated exosomes

Pancreatic cancers with poor prognosis are highly malignant, readily metastatic and of immune tolerance, mainly due to delayed detection. The metastatic progression and immune tolerance of pancreatic cancer is greatly attributed to the intercellular communication. However, exosomes are deemed to be the most important tool of intercellular communicators. Thus, we present a review of pancreatic cancer and exosomes in this article. We intensively summarize the progress of early pancreatic cancer and the relationship of the proliferation, progression and metastasis of pancreatic cancer and pancreatic cancer-derived exosomes, and propose new ideas of the study of pancreatic cancer.

Metastasis of pancreatic cancer within primary colon cancer by overtaking the stromal microenvironment

We report a unique case of a 74-old man, who presented with double cancers, showing metastasis of pancreatic cancer to colon cancer. Histopathological examination after surgery revealed that the patient had ascending colon cancer, which metastasized to the liver (pT4N0M1), as well as pancreatic cancer (pT2N1M1) that metastasized to the most invasive portion of the colon cancer, namely the serosal to subserosal layers. Although the mechanisms for this scenario have yet to be elucidated, we speculate that the metastatic pancreatic carcinoma overtook the stromal microenvironment of the colon cancer. Namely, the cancer microenvironment enriched by cancer-associated fibroblasts, which supported the colon cancer, might be suitable for the invasion and engraftment by pancreatic carcinoma. The similarity of histological appearance might make it difficult to distinguish metastatic pancreatic carcinoma within colon cancer. Furthermore, the metastasis of pancreatic carcinoma in colon carcinoma might be more common, despite it not having been previously reported.

Tumor-released exosomal circular RNA PDE8A promotes invasive growth via the miR-338/MACC1/MET pathway in pancreatic cancer

Circular RNA (circ-RNA) and exosomes have recently been shown to play important roles in different tumors. However, the functions and regulatory mechanisms of exosomal circ-RNA in pancreatic ductal adenocarcinoma (PDAC) tumor progression remain unclear. Here, we identified a circular RNA (circ-PDE8A) from liver-metastatic PDAC cells by microarray analysis, detected its expression levels in clinical tissues and found that high circ-PDE8A expression was correlated with lymphatic invasion, TNM stage and a poor survival rate of PDAC patients. Further study revealed that circ-PDE8A promotes the invasive growth of PDAC cells via upregulating MET. Circ-PDE8A acts as a ceRNA for miR-338 to regulate MACC1 and stimulates invasive growth via the MACC/MET/ERK or AKT pathways. We further imaged the exosome communication between tumor cells and identified the tumor secreted exosomes in blood circulation. Finally, we analyzed the circ-PDE8A expression in plasma exosomes of PDAC patients and found that exosomal circ-PDE8A was associated with progression and prognosis in PDAC patients. Thus, circ-PDE8A may play an important role in tumor invasion, and exosomal circ-PDE8A may be a useful marker of PDAC diagnosis or progression.

Global scientific trends on exosome research during 2007-2016: a bibliometric analysis

Background

Exosomes are small vesicles of endosomal origin, and they can be used for the diagnosis and the treatment. However, limited data were for the evaluation of the trend of exosome researches. This study aims to investigate the trend of exosome researches and compare the contribution of research from different regions, organizations and authors.

Methods

Exosome related publications from 2007 to 2016 were retrieved from the Web of Science database. Excel, GraphPad Prism 5 and VOSviewer software were used to analyze the research trend.

Results

A total of 1852 papers were identified and were cited 62967 times. The United States accounted for 38.8% of the articles, 42.0% of the citations, and the highest H-index (76). China ranked the second in the number of articles, but the sixth in citation frequency (4337) and the fourth in H-index (36). The journals, PLoS ONE and J Biol Chem had the highest number of publications. The author, Gabrielsson S., has published the most papers in this field (22). The keyword “ribonucleic acid” was mentioned the most at 746 times, and the words, “stem cell”, “drug resistance” and “monocyte cell factor” were the latest hotspots appeared around 2015.

Conclusion

Literature growth related to exosome is expanding rapidly. The quality of the articles from China still requires improvement. Recent studies focus on the relationship with tumor, and “stem cell”, “drug resistance” and “michigan cancer foundation-7” may be the newest topics that should be closely followed in exosome research.

Tumor-derived exosomal lnc-Sox2ot promotes EMT and stemness by acting as a ceRNA in pancreatic ductal adenocarcinoma

Long noncoding RNAs (lncRNAs) or exosomes have recently been shown to play vital regulatory or communication roles in cancer biology. However, the roles and mechanisms of exosomal lncRNAs in tumor invasion or metastasis of pancreatic ductal adenocarcinoma (PDAC) remain unknown. In this study, we aimed to investigate the detailed roles and mechanisms of tumor-generated exosomes in progression and metastasis of PDAC in vitro and in vivo. We identified a lncRNA-Sox2ot from exosomes of highly invasive PDAC cells, and analyzed the expression of Sox2ot in the plasma samples and found that the plasma exosomal Sox2ot expression was high and correlated with TNM stage and overall survival rate of PDAC patients. Further research showed that Sox2ot promotes epithelial-mesenchymal transition (EMT) and stem cell like properties by regulating Sox2 expression. Sox2ot competitively binds to the miR-200 family to regulate the expression of Sox2, thus promoting invasion and metastasis of PDAC. We also confirmed the transmission of the exosomes from producer cells to recipient PDAC cells, exosomal Sox2ot can promote tumor invasion and metastasis in vitro and in vivo. We further confirmed tumor generated exosomes could excrete to tumor cell or blood circulation in vivo condition. Finally, we observed a decreased exosomal Sox2ot expression in postoperative blood samples of PDAC patients. The exosomal lncRNA Sox2ot plays important roles in tumor progression and may be a useful maker for pancreatic cancer prognosis.

The critical roles of activated stellate cells-mediated paracrine signaling, metabolism and onco-immunology in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant diseases worldwide. It is refractory to conventional treatments, and consequently has a documented 5-year survival rate as low as 7%. Increasing evidence indicates that activated pancreatic stellate cells (PSCs), one of the stromal components in tumor microenvironment (TME), play a crucial part in the desmoplasia, carcinogenesis, aggressiveness, metastasis associated with PDAC. Despite the current understanding of PSCs as a "partner in crime" to PDAC, detailed regulatory roles of PSCs and related microenvironment remain obscure. In addition to multiple paracrine signaling pathways, recent research has confirmed that PSCs-mediated tumor microenvironment may influence behaviors of PDAC via diverse mechanisms, such as rewiring metabolic networks, suppressing immune responses. These new activities are closely linked with treatment and prognosis of PDAC. In this review, we discuss the recent advances regarding new functions of activated PSCs, including PSCs-cancer cells interaction, mechanisms involved in immunosuppressive regulation, and metabolic reprogramming. It's clear that these updated experimental or clinical studies of PSCs may provide a promising approach for PDAC treatment in the near future.

MicroRNA-21 as a prognostic biomarker in patients with pancreatic cancer - A systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review and meta-analysis is to summarize the current knowledge regarding microRNA-21 and to evaluate its prognostic impact in patients with pancreatic cancer.

METHODS

We conducted an electronic literature search to identify all published studies in PubMed/MEDLINE, Scopus and Google Scholar databases from 2000 until August 2016.

RESULTS

A total of 17 studies involving 1471 patients met the inclusion criteria for the quantitative synthesis. The microRNA-21 upregulation was significantly associated with poorer overall survival, disease-free survival, and progression-free survival. The subgroup analysis revealed that microRNA-21 overexpression has a significant higher prognostic value for patients who receive adjuvant chemotherapy. Increased microRNA-21 was associated with a statistically significant higher rate of metastatic lymph nodes and poorly differentiated tumors.

CONCLUSIONS

MicroRNA-21 upregulation in pancreatic cancer is associated with a significantly poorer overall survival, disease-free survival, and progression-free survival. MicroRNA-21 may be a useful prognostic biomarker, allowing stratification for chemotherapy administration, and being a component of precision medicine in patients with pancreatic cancer.