Gastric cancer exosomes trigger differentiation of umbilical cord derived mesenchymal stem cells to carcinoma-associated fibroblasts through TGF-β/Smad pathway

Tumor-derived exosomes induce N2 polarization of neutrophils to promote gastric cancer cell migration

Background

Exosomes are extracellular vesicles that mediate cellular communication in health and diseases. Neutrophils could be polarized to a pro-tumor phenotype by tumor. The function of tumor-derived exosomes in neutrophil regulation remains unclear.

Methods

We investigated the effects of gastric cancer cell-derived exosomes (GC-Ex) on the pro-tumor activation of neutrophils and elucidated the underlying mechanisms.

Results

GC-Ex prolonged neutrophil survival and induced expression of inflammatory factors in neutrophils. GC-Ex-activated neutrophils, in turn, promoted gastric cancer cell migration. GC-Ex transported high mobility group box-1 (HMGB1) that activated NF-κB pathway through interaction with TLR4, resulting in an increased autophagic response in neutrophils. Blocking HMGB1/TLR4 interaction, NF-κB pathway, and autophagy reversed GC-Ex-induced neutrophil activation. Silencing HMGB1 in gastric cancer cells confirmed HMGB1 as a key factor for GC-Ex-mediated neutrophil activation. Furthermore, HMGB1 expression was upregulated in gastric cancer tissues. Increased HMGB1 expression was associated with poor prognosis in patients with gastric cancer. Finally, gastric cancer tissue-derived exosomes acted similarly as exosomes derived from gastric cancer cell lines in neutrophil activation.

Conclusion

We demonstrate that gastric cancer cell-derived exosomes induce autophagy and pro-tumor activation of neutrophils via HMGB1/TLR4/NF-κB signaling, which provides new insights into mechanisms for neutrophil regulation in cancer and sheds lights on the multifaceted role of exosomes in reshaping tumor microenvironment.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0898-6) contains supplementary material, which is available to authorized users.

Exosome-mediated cell-cell communication in tumor progression

Exosomes, which are 30-150 nm lipid bilayer vehicles, have been recognized as one of the most crucial components of the tumor microenvironment. Exosomes transfer specific lipid, nucleic acids, proteins and other bioactive molecules from the donor cells to the recipient cells. Accumulating evidence has suggested that cancer cells and the tumor associated stromal cells can release and receive exosomes, inside of which the components and amounts are greatly changed. Pioneering studies have revealed that these exosomes play essential roles in tumor progression. Here we summarize the recent advances in this field, by focusing on the exosome biogenesis in the cancer condition, and their biological function in angiogenesis, metastasis and chemo-resistance of tumor. The review would not only provide a summary of this field, but also insights and perspectives on exosome-based strategies in cancer diagnoses, prevention and therapy.

Cancer-derived exosomes trigger endothelial to mesenchymal transition followed by the induction of cancer-associated fibroblasts

Cancer-associated fibroblasts (CAFs) play a pivotal role in tumor growth, but very little has been known about its characteristics and origin. Recently, cancer-derived exosome has been suggested to transdifferentiate CAFs, by a new mechanism of endothelial to mesenchymal transition (EndMT), initiating angiogenic processes and triggering metastatic evolution. However, an enabling tool in vitro is yet to be developed to investigate complicated procedures of the EndMT and the transdifferentiation under reconstituted tumor microenvironment. Here we proposed an in vitro microfluidic model which enables to monitor a synergetic effect of complex tumor microenvironment in situ, including extracellular matrix (ECM), interstitial flow and environmental exosomes. The number of CAFs differentiated from human umbilical vein endothelial cells (HUVECs) increased with melanoma-derived exosomes, presenting apparent morphological and molecular changes with pronounced motility. Mesenchymal stem cell (MSC)-derived exosomes were found to suppress EndMT, induce angiogenesis and maintain vascular homeostasis, while cancer-derived exosomes promoted EndMT. Capabilities of the new microfluidic model exist in precise regulation of the complex tumor microenvironment and therefore successful reconstitution of 3D microvasculature niches, enabling in situ investigation of EndMT procedure between various cell types.

STATEMENT OF SIGNIFICANCE

This study presents an in vitro 3D EndMT model to understand the progress of the CAF generation by recapitulating the 3D tumor microenvironment in a microfluidic device. Both cancer-derived exosomes and interstitial fluid flow synergetically played a pivotal role in the EndMT and consequent formation of CAFs through a collagen-based ECM. Our approach also enabled the demonstration of a homeostatic capability of MSC-derived exosomes, ultimately leading to the recovery of CAFs back to endothelial cells. The in vitro 3D EndMT model can serve as a powerful tool to validate exosomal components that could be further developed to anti-cancer drugs.

TGF-β and mesenchymal stromal cells in regenerative medicine, autoimmunity and cancer

Multipotent mesenchymal stromal cells (MSCs) represent a promising cell-based therapy in regenerative medicine and for the treatment of inflammatory/autoimmune diseases. Importantly, MSCs have emerged as an important contributor to the tumor stroma with both pro- and anti-tumorigenic effects. However, the successful translation of MSCs to the clinic and the prevention of their tumorigenic and metastatic effect require a greater understanding of factors controlling their proliferation, differentiation, migration and immunomodulation in vitro and in vivo. The transforming growth factor(TGF)-β1, 2 and 3 are involved in almost every aspect of MSC function. The aim of this review is to highlight the roles that TGF-β play in the biology and therapeutic applications of MSCs. We will discuss the how TGF-β modulate MSC function as well as the paracrine effects of MSC-derived TGF-β on other cell types in the context of tissue regeneration, immune responses and cancer. Finally, taking all these aspects into consideration we discuss how modulation of TGF-β signaling/production in MSCs could be of clinical interest.

UBR2 Enriched in p53 Deficient Mouse Bone Marrow Mesenchymal Stem Cell-Exosome Promoted Gastric Cancer Progression via Wnt/β-Catenin Pathway

The deficiency or mutation of p53 has been linked to several types of cancers. The mesenchymal stem cell (MSC) is an important component in the tumor microenvironment, and exosomes secreted by MSCs can transfer bioactive molecules, including proteins and nucleic acid, to other cells in the tumor microenvironment to influence the progress of a tumor. However, whether the state of p53 in MSCs can impact the bioactive molecule secretion of exosomes to promote cancer progression and the regulatory mechanism remains elusive. Our study aimed to investigate the regulation of ubiquitin protein ligase E3 component n-recognin 2 (UBR2) enriched in exosomes secreted by p53 deficient mouse bone marrow MSC (p53^-/- mBMMSC) in gastric cancer progression in vivo and in vitro. We found that the concentration of exosome was significantly higher in p53^-/- mBMMSC than that in p53 wild-type mBMMSC (p53^+/+ mBMMSC). In particular, UBR2 was highly expressed in p53^-/- mBMMSC cells and exosomes. P53^-/- mBMMSC exosomes enriched UBR2 could be internalized into p53^+/+ mBMMSC and murine foregastric carcinoma (MFC) cells and induce the overexpression of UBR2 in these cells which elevated cell proliferation, migration, and the expression of stemness-related genes. Mechanistically, the downregulation of UBR2 in p53^-/- mBMMSC exosomes could reverse these actions. Moreover, a majority of Wnt family members, β-catenin, and its downstream genes (CD44, CyclinD1, CyclinD3, and C-myc) were significantly decreased in MFC knockdown UBR2 and β-catenin depletion, an additional depletion of UBR2 had no significant difference in the expression of Nanog, OCT4, Vimentin, and E-cadherin. Taken together, our findings indicated that p53^-/- mBMMSC exosomes could deliver UBR2 to target cells and promote gastric cancer growth and metastasis by regulating Wnt/β-catenin pathway. Stem Cells 2017;35:2267-2279.

Bone morphogenetic protein and activin membrane-bound inhibitor overexpression inhibits gastric tumor cell invasion via the transforming growth factor-β/epithelial-mesenchymal transition signaling pathway

Gastric carcinoma is one of the most common human malignancies and remains the second leading cause of cancer-associated mortality worldwide. Gastric carcinoma is characterized by early-stage metastasis and is typically diagnosed in the advanced stage. Previous results have indicated that bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) overexpression has been demonstrated to inhibit growth and metastasis of gastric cancer cells. However, the molecular mechanisms of the BAMBI-mediated signaling pathway in the progression of gastric cancer are poorly understood. In the present study, to assess whether BAMBI overexpression inhibited the growth and aggressiveness of gastric carcinoma cells through regulation of transforming growth factor (TGF)-β/epithelial-mesenchymal transition (EMT) signaling pathway, the growth and metastasis of gastric carcinoma cells were analyzed following BAMBI overexpression and knockdown in vitro and in vivo. Molecular changes in the TGF-β/EMT signaling pathway were studied in gastric carcinoma cells following BAMBI overexpression and knockdown. DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway was investigated in gastric carcinoma cells. Tumor growth in tumor-bearing mice was analyzed after mice were subjected to endogenous overexpression of BAMBI. Results indicated that BAMBI overexpression significantly inhibited gastric carcinoma cell growth and aggressiveness, whereas knockdown of BAMBI significantly promoted its growth and metastasis compared with the control (P<0.01). The TGF-β/EMT signaling pathway was downregulated in BAMBI-overexpressed gastric carcinoma cells; however, signaling was promoted following BAMBI knockdown. In addition, it was observed that BAMBI overexpression significantly downregulated the DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway (P<0.01). Furthermore, RNA interference-mediated BAMBI overexpression also promoted apoptosis in gastric cancer cells and significantly inhibited growth of gastric tumors in murine xenografts (P<0.01). In conclusion, the present findings suggest that BAMBI overexpression inhibited the TGF-β/EMT signaling pathway and suppressed the invasiveness of gastric tumors, suggesting BAMBI may be a potential target for the treatment of gastric carcinoma via regulation of the TGF-β/EMT signaling pathway.

Exosomal miR-423-5p targets SUFU to promote cancer growth and metastasis and serves as a novel marker for gastric cancer

Exosomes are critically involved in tumor growth, metastasis, and therapy resistance. Exosomes have the potential to be utilized as cancer biomarkers. In this study, we aimed to explore the roles and clinical values of exosomal miRNAs in gastric cancer. We found that the concentration of exosomes was significantly higher in the serum of gastric cancer patients and the culture supernatants of gastric cancer cells than that in healthy volunteers and gastric mucosa epithelial cells. In particular, miR-423-5p was elevated in the serum exosomes of gastric cancer patients, and the level of exosomal miR-423-5p was remarkably correlated with lymph node metastasis. High level of exosomal miR-423-5p was associated with poor outcome in gastric cancer patients. MiR-423-5p enriched exosomes could be internalized into gastric cancer cells, which enhanced cell proliferation and migration both in vitro and in vivo. Mechanistically, miR-423-5p inhibited the expression of suppressor of fused protein (SUFU) to enhance the proliferation and migration of gastric cancer cells. The expression levels of SUFU were significantly decreased in gastric cancer cells and the tumor tissues of gastric cancer patients. Taken together, our findings indicate that exosomes could deliver miR-423-5p to promote cancer growth and metastasis and serum exosomal miR-423-5p may serve as a potential marker for gastric cancer diagnosis and prognosis.

Ovarian cancer-derived extracellular vesicles affect normal human fibroblast behavior

It has become clear that non-tumor cells in the microenvironment, especially fibroblasts, actively participate in tumor progression. Fibroblasts conditioned by tumor cells become "activated" and, as such, are identified as CAFs (cancer-associated fibroblasts). These CAFs remodel the tumor stroma to make it more favourable for cancer progression. The aim of this work was to verify whether EVs (extracellular vesicles - whose role as mediators of information between tumor and stromal cells is well known) released from human ovarian cancer cells were able to activate fibroblasts. EVs isolated from SKOV3 (more aggressive) and CABA I (less aggressive) cells were administered to fibroblasts. The consequent activation was supported by morphological and molecular changes in treated fibroblasts; XTT assays, zymographies, wound healing tests and invasion assays also highlighted higher proliferation, motility, invasiveness and enzyme expression. The secretome of these "activated" fibroblasts was, in turn, able to modulate the responses (proliferation, motility and invasion) of fibroblasts, and of tumor and endothelial cells. These findings support the idea that ovarian cancer cells can modulate fibroblast behaviour through the release of EVs, activating them to a CAFs-like state; the latter are able, in turn, to stimulate the surrounding cells. EVs from SKOV3 rather than from CABA I seem to be more efficient in some processes.

Emerging role of exosome-derived long non-coding RNAs in tumor microenvironment

Exosomes are extracellular vesicles released by many cell types and have been attributed for their roles in many diseases including cancer. Exosomes secreted by tumor cells and stromal cells are critical mediators of intercellular communication in tumor microenvironments. Long noncoding RNAs (lncRNAs) are selectively sorted into exosomes and can regulate cancer onset and progression in a variety of ways. In this review, we summarize the characteristics of exosomal lncRNAs and their dysregulation in multiple types of cancer. We provide an overview of current research on exosomal lncRNAs in tumor microenvironments, especially the functions of exosomal lncRNAs in regulating tumor biology. A deeper understanding of the role of exosomal lncRNAs in the tumor microenvironment may help provide new diagnostic and prognostic markers for cancer.

Exosomes Released by Gastric Cancer Cells Induce Transition of Pericytes Into Cancer-Associated Fibroblasts

Background

Cancer-associated fibroblasts (CAFs) are functionally and structurally essential for tumor progression. There are 3 main origins of CAFs: mesenchymal stem cells (MSCs), epithelial-to-mesenchymal (EMT) transition cells, and tissue-resident cells. Pericytes retain characteristics of progenitor cells and can differentiate into other cells under normal physiological conditions and into myofibroblasts under pathological conditions. Exosomes play an important role in intercellular communication by transferring membrane components and nucleic acids between different cells. In this study, we evaluated whether cancer cell-derived exosomes are involved in regulating the transition of pericytes to CAFs.

Material/Methods

Exosomes from GES-1 and SGC7901 cells were isolated by serial centrifugation and purified from the supernatant by the 30% sucrose/D₂O cushion method. A transmission electron microscope was used to observe exosome morphologies, and nanoparticle tracking analysis was used to analyze size distribution of exosomes. Western blot analysis, immunofluorescent staining, and qPCR were employed to detect CAFs marker expression and signaling pathways involved in CAFs transition.

Results

Gastric cancer cell-derived exosomes enhanced pericytes proliferation and migration and induced the expression of CAFs marker in pericytes. We then demonstrated that the PI3K/AKT and MEK/ERK pathways were activated by tumor-derived exosomes, and BMP pathway inhibition reverses cancer exosomes-induced CAFs transition.

Conclusions

Our results suggest that gastric cancer cells induce the transition of pericytes to CAFs by exosomes-mediated BMP transfer and PI3K/AKT and MEK/ERK pathway activation, and suggest that pericytes may be an important source of CAFs.

The multifaceted role of exosomes in cancer progression: diagnostic and therapeutic implications [corrected]

BACKGROUND

Recent advances in cancer biology have highlighted the relevance of exosomes and nanovesicles as carriers of genetic and biological messages between cancer cells and their immediate and/or distant environments. It has been found that these molecular cues may play significant roles in cancer progression and metastasis. Cancer cells secrete exosomes containing diverse molecules that can be transferred to recipient cells and/or vice versa to induce a plethora of biological processes, including angiogenesis, metastasis formation, therapeutic resistance, epithelial-mesenchymal transition and epigenetic/stemness (re)programming. While exosomes interact with cells within the tumour microenvironment to promote tumour growth, these vesicles can also facilitate the process of distant metastasis by mediating the formation of pre-metastatic niches. Next to their tumour promoting effects, exosomes have been found to serve as potential tools for cancer diagnosis and therapy. The ease of isolating exosomes and their content from different body fluids has led to the identification of diagnostic and prognostic biomarker signatures, as well as to predictive biomarker signatures for therapeutic responses. Exosomes can also be used as cargos to deliver therapeutic anti-cancer drugs, and they can be engineered to serve as vaccines for immunotherapy. Additionally, it has been found that inhibition of exosome secretion, and thus the transfer of oncogenic molecules, holds promise for inhibiting tumour growth. Here we provide recent information on the diverse roles of exosomes in various cellular and systemic processes governing cancer progression, and discuss novel strategies to halt this progression using exosome-based targeted therapies and methods to inhibit exosome secretion and the transfer of pro-tumorigenic molecules.

CONCLUSIONS

This review highlights the important role of exosomes in cancer progression and its implications for (non-invasive) diagnostics and the development of novel therapeutic strategies, as well as its current and future applications in clinical trials.

Exosomes Induce Fibroblast Differentiation into Cancer-Associated Fibroblasts through TGFβ Signaling

A particularly important tumor microenvironment relationship exists between cancer cells and surrounding stromal cells. Fibroblasts, in response to cancer cells, become activated and exhibit myofibroblastic characteristics that favor invasive growth and metastasis. However, the mechanism by which cancer cells promote activation of healthy fibroblasts into cancer-associated fibroblasts (CAF) is still not well understood. Exosomes are nanometer-sized vesicles that shuttle proteins and nucleic acids between cells to establish intercellular communication. Here, bladder cancer-derived exosomes were investigated to determine their role in the activation of healthy primary vesical fibroblasts. Exosomes released by bladder cancer cells are internalized by fibroblasts and promoted the proliferation and expression of CAF markers. In addition, cancer cell-derived exosomes contain TGFβ and in exosome-induced CAFs SMAD-dependent signaling is activated. Furthermore, TGFβ inhibitors attenuated CAF marker expression in healthy fibroblasts. Therefore, these data demonstrate that bladder cancer cells trigger the differentiation of fibroblasts to CAFs by exosomes-mediated TGFβ transfer and SMAD pathway activation. Finally, exosomal TGFβ localized inside the vesicle and contributes 53.4% to 86.3% of the total TGFβ present in the cancer cell supernatant. This study highlights a new function for bladder cancer exosomes as novel modulators of stromal cell differentiation.Implication: This study identifies exosomal TGFβ as new molecular mechanism involved in cancer-associated fibroblast activation. Mol Cancer Res; 16(7); 1196-204. ©2018 AACR.

Malignant ascites-derived exosomes promote proliferation and induce carcinoma-associated fibroblasts transition in peritoneal mesothelial cells

Malignant ascites-derived exosomes have been demonstrated to participate in tumor metastasis. In peritoneal metastasis, normal mesothelial cells (MCs) can be converted into carcinoma-associated fibroblasts (CAFs) by mesothelial-mesenchymal transition (MMT). Herein, we evaluated the effect of malignant ascites-derived exosomes on peritoneal MCs in vitro and in vivo experiments to determine whether exosomes could educate MCs and contribute to peritoneal metastasis.

Under the treatment of ascites-derived exosomes, peritoneal MCs showed increased ability to proliferate and migrate. Expression of CAFs specific proteins markers in MCs, including fibroblast activation protein (FAP), alpha-smooth muscle actin (α-SMA), and fibronectin, were increased after treatment of exosomes. In clinical samples test, TGF-β1 was found to be overexpressed in both malignant ascites and malignant ascites-derived exosomes, and the high volume of TGF-β1 may be responsible for peritoneum fibrosis. In addition, exosomes can increase xenograft tumor growth by suppressing the inhibitive ability on tumor cells by MCs. Besides, CAFs specific proteins markers including FAP, α-SMA, and vimentin were increased in clinical peritoneal biopsies. The immunohistochemical staining for mice tumor biopsies also revealed increased expression of fibronectin and FAP, along with decreased expression of E-cadherin and VCAM-1 after exosomes treatment.

Thus, malignant ascites-derived exosomes may be of importance in the development of peritoneal metastasis by facilitating MCs to proliferate and convert into CAFs by TGF-β1 induced MMT.

Circulating exosomes potentiate tumor malignant properties in a mouse model of chronic sleep fragmentation

Background

Chronic sleep fragmentation (SF) increases cancer aggressiveness in mice. Exosomes exhibit pleiotropic biological functions, including immune regulatory functions, antigen presentation, intracellular communication and inter-cellular transfer of RNA and proteins. We hypothesized that SF-induced alterations in biosynthesis and cargo of plasma exosomes may affect tumor cell properties.

Results

SF-derived exosomes increased tumor cell proliferation (~13%), migration (~2.3-fold) and extravasation (~10%) when compared to exosomes from SC-exposed mice. Similarly, Pre exosomes from OSA patients significantly enhanced proliferation and migration of human adenocarcinoma cells compared to Post. SF-exosomal cargo revealed 3 discrete differentially expressed miRNAs, and exploration of potential mRNA targets in TC1 tumor cells uncovered 132 differentially expressed genes that encode for multiple cancer-related pathways.

Methods

Plasma-derived exosomes from C57/B6 mice exposed to 6 wks of SF or sleep control (SC), and from adult human patients with obstructive sleep apnea (OSA) before (Pre) and after adherent treatment for 6 wks (Post) were co-cultured with mouse lung TC1 or human adenocarcinoma tumor cell lines, respectively. Proliferation, migration, invasion, endothelial barrier integrity and extravasation assays of tumor cells were performed. Plasma mouse exosomal miRNAs were profiled with arrays, and transcriptomic assessments of TC1 cells exposed to SF or SC exosomes were conducted to identify gene targets.

Conclusions

Chronic SF induces alterations in exosomal miRNA cargo that alter the biological properties of TC1 lung tumor cells to enhance their proliferative, migratory and extravasation properties, and similar findings occur in OSA patients, in whom SF is a constitutive component of their sleep disorder. Thus, exosomes could participate, at least in part, in the adverse cancer outcomes observed in OSA.

Extracellular vesicle cross-talk in the bone marrow microenvironment: implications in multiple myeloma

The bone marrow (BM) represents a complex microenvironment containing stromal cells, immune cells, osteoclasts, osteoblasts, and hematopoietic cells, which are crucial for the immune response, bone formation, and hematopoiesis. Apart from soluble factors and direct cell-cell contact, extracellular vesicles (EVs), including exosomes, were recently identified as a third mediator for cell communication. Solid evidence has already demonstrated the involvement of various BM-derived cells and soluble factors in the regulation of multiple biological processes whereas the EV-mediated message delivery system from the BM has just been explored in recent decades. These EVs not only perform physiological functions but can also play a role in cancer development, including in Multiple Myeloma (MM) which is a plasma cell malignancy predominantly localized in the BM. This review will therefore focus on the multiple functions of EVs derived from BM cells, the manipulation of the BM by cancer-derived EVs, and the role of BM EVs in MM progression.

Prostate stromal cell proteomics analysis discriminates normal from tumour reactive stromal phenotypes

Changes within interstitial stromal compartments often accompany carcinogenesis, and this is true of prostate cancer. Typically, the tissue becomes populated by myofibroblasts that can promote progression. Not all myofibroblasts exhibit the same negative influence, however, and identifying the aggressive form of myofibroblast may provide useful information at diagnosis. A means of molecularly defining such myofibroblasts is unknown. We compared protein profiles of normal and diseased stroma isolated from prostate cancer patients to identify discriminating hallmarks of disease-associated stroma. We included the stimulation of normal stromal cells with known myofibroblast inducers namely soluble TGFβ and exosome-associated-TGFβ and compared the function and protein profiles arising. In all 6-patients examined, diseased stroma exhibited a pro-angiogenic influence on endothelial cells, generating large multicellular vessel-like structures. Identical structures were apparent following stimulation of normal stroma with exosomes (5/6 patients), but TGFβ-stimulation generated a non-angiogenic stroma. Proteomics highlighted disease-related cytoskeleton alterations such as elevated Transgelin (TAGLN). Many of these were also changed following TGFβ or exosome stimulation and did not well discriminate the nature of the stimulus. Soluble TGFβ, however triggered differential expression of proteins related to mitochondrial function including voltage dependent ion channels VDAC1 and 2, and this was not found in the other stromal types studied. Surprisingly, Aldehyde Dehydrogenase (ALDH1A1), a stem-cell associated protein was detected in normal stromal cells and found to decrease in disease. In summary, we have discovered a set of proteins that contribute to defining disease-associated myofibroblasts, and emphasise the similarity between exosome-generated myofibroblasts and those naturally arising in situ.

Multiple Myeloma-Derived Exosomes Regulate the Functions of Mesenchymal Stem Cells Partially via Modulating miR-21 and miR-146a

Exosomes derived from cancer cells can affect various functions of mesenchymal stem cells (MSCs) via conveying microRNAs (miRs). miR-21 and miR-146a have been demonstrated to regulate MSC proliferation and transformation. Interleukin-6 (IL-6) secreted from transformed MSCs in turn favors the survival of multiple myeloma (MM) cells. However, the effects of MM exosomes on MSC functions remain largely unclear. In this study, we investigated the effects of OPM2 (a MM cell line) exosomes (OPM2-exo) on regulating the proliferation, cancer-associated fibroblast (CAF) transformation, and IL-6 secretion of MSCs and determined the role of miR-21 and miR-146a in these effects. We found that OPM2-exo harbored high levels of miR-21 and miR-146a and that OPM2-exo coculture significantly increased MSC proliferation with upregulation of miR-21 and miR-146a. Moreover, OPM2-exo induced CAF transformation of MSCs, which was evidenced by increased fibroblast-activated protein (FAP), α-smooth muscle actin (α-SMA), and stromal-derived factor 1 (SDF-1) expressions and IL-6 secretion. Inhibition of miR-21 or miR-146a reduced these effects of OPM2-exo on MSCs. In conclusion, MM could promote the proliferation, CAF transformation, and IL-6 secretion of MSCs partially through regulating miR21 and miR146a.

Cancer-associated fibroblasts regulate the biological behavior of cancer cells and stroma in gastric cancer

Gastric cancer (GC) is a frequently diagnosed type of cancer in China, and is associated with a high mortality rate. The biological behavior of GC requires investigation in order to provide an evidence base for the development of strategies to prevent and treat GC. For this purpose, the present review outlines the process of tumor microenvironment (TME) evolution, including the dynamic biological behavior of different types of cancer cell and stroma. Cancer-associated fibroblasts (CAFs) serve as prominent stromal cellular components in the GC TME, and exhibit an essential function in GC progression. In the present study, the function of CAFs in cancer cell proliferation, cell migration, invasion, extracellular matrix remodeling, pathological angiogenesis and immune cell infiltration were investigated. The studies discussed in the present review demonstrate that the cross-talk between CAF, cancer cells and tumor stroma promotes GC progression.

Exosomes secreted by stem cells from human exfoliated deciduous teeth contribute to functional recovery after traumatic brain injury by shifting microglia M1/M2 polarization in rats

BACKGROUND

Traumatic brain injury (TBI) is one of the major causes of mortality and disability for all ages worldwide. Mesenchymal stem cells (MSCs)-originated exosomes have provided therapeutic effects. However, as an indispensable component of MSCs, whether odontogenic stem cell-generated exosomes could benefit TBI is still unclear. Thus we aimed to explore the potential of stem cells from human exfoliated deciduous teeth-originated exosomes (SHED-Ex) for the management of TBI.

METHODS

First, a transwell system was used to co-culture activated BV-2 microglia cells with SHED. The secretion levels of neuroinflammatory factors and nitrite were evaluated by enzyme-linked immunosorbent assay (ELISA) and Griess assay. Furthermore, purified SHED-Ex were co-cultured with activated BV-2. ELISA, Griess assay, flow cytometry, immunofluorescence, and qRT-PCR were performed to test the levels of inflammatory factors as well as the microglia phenotype. Finally, SHED and SHED-Ex were locally injected into TBI rat models. Basso, Beattie, and Bresnahan (BBB) scores were chosen to evaluate the motor functional recovery. Histopathology and immunofluorescence were performed to measure the lesion volume and neuroinflammation.

RESULTS

As a result, SHED-Ex could reduce neuroinflammation by shifting microglia polarization. The administration of SHED-Ex improves rat motor functional recovery and reduces cortical lesion compared with the control group 2 weeks post-injury (P < 0.05).

CONCLUSIONS

The current study demonstrates for the first time that SHED-Ex contribute a therapeutic benefit to TBI in rats, at least in part by shifting microglia polarization to reduce neuroinflammation. The use of odontogenic stem cells, and indeed their exosomes, may be expanded for the treatment of TBI or other neurological disorders.

Tumor microenvironment interruption: a novel anti-cancer mechanism of Proton-pump inhibitor in gastric cancer by suppressing the release of microRNA-carrying exosomes

Poor prognosis of gastric cancer is related to not only malignancy of gastric cancer cells, but also the tumor microenvironment. Thus drugs, which can inhibit both of them, are urgently needed to be explored. Studies on effect of Proton-pump inhibitors (PPIs) in anti-neoplasms are increasing, but is rare in gastric in gastric cancer. Here we investigated how the gastric cancer microenvironment is regulated by PPIs. The objective response rate of gastric cancer patients in our hospital treated by PPIs is investigated. PPIs' effects were further explored by observing the change of microRNAs, cytokines, cellular apoptosis. Bioinformatic pathway analysis of microarray was used to discover the pathway involved in PPIs' regulation of gastric cancer microenvironments. Immunoblotting assays and qRT-PCR were used to define molecular events with PPIs treatment. We report here that PPIs can improve the prognosis of advanced gastric cancer patients; and inhibit the progress of gastric cancer both in vivo and in vitro. Moreover, high dose of PPIs can regulate the pathway associated with tumor malignancy and microenvironment via inhibiting the release of exosomes, which packed microRNAs. PPIs can inhibit the transformation of CAFs (cancer associated fibroblasts) and cytokines released from CAFs. In addition, PPIs inhibit the malignancy of gastric cancer through regulating HIF-1α-FOXO1 axis. High dose of PPIs can inhibit malignancy of gastric cancer and regulate its surrounding tumor microenvironment. This finding suggests that PPIs maybe of potential value as a therapeutic tool for treatment of gastric cancer.

Role of exosomal proteins in cancer diagnosis

Exosomes are emerging as a new type of cancer biomarkers. Exosome is a bilayered nano-sized vesicle secreted by various living cells in all body fluids. Based on the expanding albeit incomplete knowledge of their biogenesis, secretion by cells and cancer cell-specific molecular and genetic contents, exosomes are viewed as promising, clinically-relevant surrogates of cancer progression and response to therapy. Preliminary proteomic, genetic and functional profiling of cancer cell-derived or cancer plasma-derived exosomes confirms their unique characteristics. Alterations in protein or nucleic acid profiles of exosomes in plasma correlate with pathological processes of many diseases including cancer. However, previous studies on exosome application in cancer diagnosis and treatment mainly focussed on miRNAs. With the development of rapid large-scale production, purification, extraction and screening of exosomal contents, exosomal protein application can be explored for early stage cancer diagnosis, monitoring and prognosis evaluation. Here, we summarized the recent developments in application of exosomal proteins for cancer diagnosis.

Exosomes from high glucose-treated glomerular endothelial cells trigger the epithelial-mesenchymal transition and dysfunction of podocytes

New data indicate that abnormal glomerular endothelial cell (GEC)-podocyte crosstalk plays a critical role in diabetic nephropathy (DN). The aim of our study is to investigate the role of exosomes from high glucose (HG)-treated GECs in the epithelial-mesenchymal transition (EMT) and dysfunction of podocytes. In this study, exosomes were extracted from GEC culture supernatants and podocytes were incubated with the GEC-derived exosomes. Here, we demonstrate that HG induces the endothelial-mesenchymal transition (EndoMT) of GECs and HG-treated cells undergoing the EndoMT secrete more exosomes than normal glucose (NG)-treated GECs. We show that GEC-derived exosomes can be internalized by podocytes and exosomes from HG-treated cells undergoing an EndoMT-like process can trigger the podocyte EMT and barrier dysfunction. Our study reveals that TGF-β1 mRNA is enriched in exosomes from HG-treated GECs and probably mediates the EMT and dysfunction of podocytes. In addition, our experimental results illustrate that canonical Wnt/β-catenin signaling is involved in the exosome-induced podocyte EMT. Our findings suggest the importance of paracrine communication via exosomes between cells undergoing the EndoMT and podocytes for renal fibrosis in DN. Thus, protecting GECs from the EndoMT and inhibiting TGF-β1-containing exosomes release from GECs is necessary to manage renal fibrosis in DN.

Exosomes participate in the carcinogenesis and the malignant behavior of gastric cancer

OBJECTIVE

In order to summarize the role of exosomes in invasion and metastasis in gastric cancer (GC).

MATERIAL

Exosomes are vesicles of endocytic origin ranging from 30 to 100 nm in size; they are composed of a lipid bilayer and contain DNA, mRNA, miRNA, circular RNA and multiple proteins. Recently, increasing evidence shows that exosomes play a crucial role in the tumorigenesis of GC.

RESULTS

In this review, we focus on the latest findings on GC exosomes, mainly summarizing their role in invasion and metastasis in GC. Then, exosomes? potential functions as novel diagnostic and therapeutic biomarkers for GC are briefly discussed. At last, we prospect the clinical application perspective of exosomes in GC.

CONCLUSIONS

Exosomes play a vital role in gastric cancer carcinogenesis and metastasis.

The role of exosomes in cancer metastasis

Exosomes are small membrane vesicles with a size ranging from 40 to 100nm. They can serve as functional mediators in cell interaction leading to cancer metastasis. Metastasis is a complex multistep process of cancer cell invasion, survival in blood vessels, attachment to and colonization of the host organ. Exosomes influence every step of this cascade and can be targeted by oncological treatment. This review highlights the role of exosomes in the various steps of the metastatic cascade and how exosome dependent pathways can be targeted as therapeutic approach or used for liquid biopsies.

Effects of exosome-like vesicles on cumulus expansion in pigs in vitro

Cell-secreted vesicles, such as exosomes, have recently been recognized as mediators of cell communication. A recent study in cattle showed the involvement of exosome-like vesicles in the control of cumulus expansion, a prerequisite process for normal ovulation; however, whether this is the case in other mammalian species is not known. Therefore, this study aimed to examine the presence of exosome-like vesicles in ovarian follicles and their effects on cumulus expansion in vitro in pigs. The presence of exosome-like vesicles in porcine follicular fluid (pFF) was confirmed by transmission electron microscopic observation, the detection of marker proteins, and RNA profiles specific to exosomes. Fluorescently labeled exosome-like vesicles isolated from pFF were incorporated into both cumulus and mural granulosa cells in vitro. Exosome-like vesicles were not capable of inducing cumulus expansion to a degree comparable to that induced by follicle-stimulating hormone (FSH). Moreover, exosome-like vesicles had no significant effects on the expression levels of transcripts required for the normal expansion process (HAS2, TNFAIP6, and PTGS2). Interestingly, FSH-induced expression of HAS2 and TNFAIP6 mRNA, but not of PTGS2 mRNA, was significantly increased by the presence of exosome-like vesicles; however, the degree of FSH-induced expansion was not affected. In addition, porcine exosome-like vesicles had no significant effects on the expansion of mouse cumulus-oocyte complexes. Collectively, the present results suggest that exosome-like vesicles are present in pFF, but they are not efficient in inducing cumulus expansion in pigs.

Going live with tumor exosomes and microvesicles

Tumor extracellular vesicles (EVs), including exosomes, emerged as key drivers of the pro-tumorigenic dialog between the tumor mass and its microenvironment by mediating long and short distance communication. In vitro studies defined the capacity of tumor EVs to modify the phenotypes of stromal and tumor cells. These studies are now supported by a growing number of functional in vivo experiments. Remarkably, they allowed the identification of a new role for tumor EVs in priming the pre-metastatic niches (PMN). Several molecules transported in tumor EVs (RNAs and proteins) have recently been found to be essential for tumor progression and metastasis in vivo. In parallel, novel EV labeling and tracking strategies have very recently allowed the first descriptions of tumor EVs in vivo and pave the way for a better understanding of their function in realistic pathophysiological contexts. Here, we review the functional approaches and the recent progress in in vivo imaging of EVs, which have refined our understanding of the role played by tumor EVs. Finally, we emphasize the remaining challenges and open questions related to the biology of tumor EVs.

The Multiple Roles of Exosomes in Metastasis

Exosomes are important contributors to cell-cell communication and their role as diagnostic markers for cancer and the pathogenesis for cancer is under intensive investigation. Here, we focus on their role in metastasis-related processes. We discuss their impact regarding promotion of invasion and migration of tumor cells, conditioning of lymph nodes, generation of premetastatic niches and organotropism of metastasis. Furthermore, we highlight interactions of exosomes with bone marrow and stromal components such as fibroblasts, endothelial cells, myeloid- and other immune-related cells in the context of metastases. For all processes as described above, we outline molecular and cellular components for therapeutic intervention with metastatic processes.

Exosomes in human atherosclerosis: An ultrastructural analysis study

Cell-to-cell communication, or signaling, is absolutely essential in orchestrating the activities of cells in multicellular organisms, to grow, develop, detect environmental changes and compensate for them in an internal, coordinated fashion. In the last few years, a considerable amount of new data have demonstrated the occurrence of a sophisticated intercellular signaling pathway based on the release of specialized vesicular structures, called exosomes, whose secretion appears to be regulated by various natural and experimental stimuli, physiological states, and disease processes. In the cardiovascular system, the study of exosomes is still in its infancy. Here, we aim to provide the first ultrastructural evidence for the presence of exosomes in human atherosclerotic plaque. We demonstrate by means of transmission electron microscopy that both lesional smooth muscle cells and endothelial cells are able to generate these membraneous microvesicles within specific compartments of the cell, called multivesicular bodies. Notably, in our series no signs of apoptosis have been detected in vascular cells secreting exosomes and no evidence of calcification has been observed associated with these structures in the extracellular space. Our results suggest the possible existence of a new mechanism of intercellular communication in the plaque milieu.

Growth differentiation factor 15 contributes to cancer-associated fibroblasts-mediated chemo-protection of AML cells

BACKGROUND

Chemo-resistance is still a major obstacle in efforts to overcome acute myeloid leukemia (AML). An emerging concept has proposed that interactions between the bone marrow (BM) microenvironment and leukemia cells reduce the sensitivity of the leukemia cells to chemotherapy. As an important element of the tumor microenvironment, the cancer-associated fibroblasts (CAFs) are considered to be activated modulators in the chemo-resistance of many solid tumors. But their contribution to AML has yet to be fully understood. Here we report a critical role for CAFs which were thought to be a survival and chemo-protective factor for leukemia cells.

METHODS

A retrospective study on the BM biopsies from 63 primary AML patients and 59 normal controls was applied to quantitative analysis the fiber stroma in the BM sections. Then immunohistochemistry on the BM biopsies were used to detect the makers of the CAFs. Their effects on drug resistance of leukemia cells were further to be assessed by co-cultured experiments in vitro. Moreover, the possible mechanisms involved in CAF-mediated chemo-protection of AML cells was investigated by antibody neutralization and siRNA knockdown experiments, with particular emphasis on the role of GDF15.

RESULTS

In our study, excessive reticular fibers in the BM led to higher frequency of relapse and mortality in primary AML patients, bringing the inspiration for us to investigate the functional roles of the fiber-devied cells. We declared that the CAF cells which expressed higher levels of FSP1, α-SMA or FAP protein were widely distributed in the marrow of AML. Then in vitro co-cultured tests showed that these CAFs could protect leukemia cell lines (THP-1/K562) from chemotherapy. Interestingly, this effect could be decreased by either treatment with a neutralizing anti-GDF15 antibody or knockdown GDF15 (with siGDF15) in CAFs. Furthermore, we also confirmed that the GDF15(+) cells mainly co-localized with FAP, which was identified as the typical phenotype of CAFs in the BM stroma.

CONCLUSIONS

We firstly demonstrate that the functional CAFs are widespread within the BM of AML patients and should be a critical chemo-protective element for AML cells by producing amount of GDF15.

How cancer cells dictate their microenvironment: present roles of extracellular vesicles

Intercellular communication plays an important role in cancer initiation and progression through secretory molecules, including growth factors and cytokines. Recent advances have revealed that small membrane vesicles, termed extracellular vesicles (EVs), served as a regulatory agent in the intercellular communication of cancer. EVs enable the transfer of functional molecules, including proteins, mRNA and microRNAs (miRNAs), into recipient cells. Cancer cells utilize EVs to dictate the unique phenotype of surrounding cells, thereby promoting cancer progression. Against such "education" by cancer cells, non-tumoral cells suppress cancer initiation and progression via EVs. Therefore, researchers consider EVs to be important cues to clarify the molecular mechanisms of cancer biology. Understanding the functions of EVs in cancer progression is an important aspect of cancer biology that has not been previously elucidated. In this review, we summarize experimental data that indicate the pivotal roles of EVs in cancer progression.

The Roles of Mesenchymal Stromal/Stem Cells in Tumor Microenvironment Associated with Inflammation

State of tumor microenvironment (TME) is closely linked to regulation of tumor growth and progression affecting the final outcome, refractoriness, and relapse of disease. Interactions of tumor, immune, and mesenchymal stromal/stem cells (MSCs) have been recognized as crucial for understanding tumorigenesis. Due to their outstanding features, stem cell-like properties, capacity to regulate immune response, and dynamic functional phenotype dependent on microenvironmental stimuli, MSCs have been perceived as important players in TME. Signals provided by tumor-associated chronic inflammation educate MSCs to alter their phenotype and immunomodulatory potential in favor of tumor-biased state of MSCs. Adjustment of phenotype to TME and acquisition of tumor-promoting ability by MSCs help tumor cells in maintenance of permissive TME and suppression of antitumor immune response. Potential utilization of MSCs in treatment of tumor is based on their inherent ability to home tumor tissue that makes them suitable delivery vehicles for immune-stimulating factors and vectors for targeted antitumor therapy. Here, we review data regarding intrusive effects of inflammatory TME on MSCs capacity to affect tumor development through modification of their phenotype and interactions with immune system.

Exosomes derived from human mesenchymal stem cells promote gastric cancer cell growth and migration via the activation of the Akt pathway

Mesenchymal stem cells (MSCs) are a component of the tumor microenvironment and can promote the development of gastric cancer through paracrine mechanism. However, the effects of MSC‑exosomes (MSC‑ex) on gastric cancer are less clear. The present study reported that MSC‑ex promoted the proliferative and metastatic potential of gastric cancer cells ex vivo. It was found that MSC‑ex enhanced the migration and invasion of HGC‑27 cells via the induction of the epithelial‑mesenchymal transition. MSC‑ex increased the expression of mesenchymal markers and reduced the expression of epithelial markers in gastric cancer cells. MSC‑ex also enhanced the tumorigenicity of gastric cancer cells ex vivo. MSC‑ex induced the stemness of gastric cancer cells. The expression of octamer‑binding transcription factor 4, ex determining region Y‑box 2 and Lin28B significantly increased in gastric cancer cells treated with MSC‑ex. The present study further demonstrated that MSC‑ex elicited these biological effects predominantly via the activation of the protein kinase B signaling pathway. Taken together, the present findings provided novel evidence for the role of MSC‑ex in gastric cancer and a new opportunity for improving the efficiency of gastric cancer treatment by targeting MSC‑ex.

The roles of tumor- and metastasis-promoting carcinoma-associated fibroblasts in human carcinomas

Carcinoma-associated fibroblasts (CAFs) constitute a substantial proportion of the non-neoplastic mesenchymal cell compartment in various human tumors. These fibroblasts are phenotypically converted from their progenitors via interactions with nearby cancer cells during the course of tumor progression. The resulting CAFs, in turn, support the growth and progression of carcinoma cells. These fibroblasts have a major influence on the hallmarks of carcinoma and promote tumor malignancy through the secretion of tumor-promoting growth factors, cytokines and exosomes, as well as through the remodeling of the extracellular matrix. Coevolution of CAFs and carcinoma cells during tumorigenesis is therefore essential for progression into fully malignant tumors. Recent studies have revealed the molecular mechanisms underlying CAF functions, especially in tumor invasion, metastasis and drug resistance and have highlighted the significant heterogeneity among these cells. In this review, we summarize the impacts of recently identified roles of tumor-promoting CAFs and discuss the therapeutic implications of targeting the heterotypic interactions of these fibroblasts with carcinoma cells. Graphical Abstract ᅟ.

Exosomes in carcinogenesis: molecular palkis carry signals for the regulation of cancer progression and metastasis

Exosomes, which act as biological cargo vessels, are cell-released, phospholipid-enclosed vesicles. In eukaryotic cells, exosomes carry and exchange biological materials or signals for the benefit or detriment to the cells. Thereby, we consider exosomes to be molecular Palkis (carriers). Although exosomes are currently one of the most popularly researched cellular entities, they have remained largely enigmatic and warrant continued investigation into their structure and functions. These membraned vesicles are between 30 and 150 nm in diameter and are actively secreted by all cell types. While initially considered cellular "trash bags," recent years have revealed exosomes to be dynamic and multi-functional vesicles that may play a crucial role in cancer development, progression and metastasis. Thereby, they have the potential to be used in development of therapeutic modalities for cancer and other diseases. As more research studies emerge, it's becoming evident that exosomes are released by cells with a purpose and are representatives of certain cell types and disease conditions. Hence, they may also be used as biomarkers for the detection of cancer initiation, progression and organotropic metastatic growth of cancer cells. This review will focus on the recent developments achieved in identifying the role of exosomes in cancer development and progression as well as therapeutic implications. The review will also discuss the pitfalls of methodologies used for the extraction of exosomes.

Exosomes derived from gastric cancer cells activate NF-κB pathway in macrophages to promote cancer progression

Exosomes are nano-sized membrane vesicles secreted by both normal and cancer cells. Emerging evidence indicates that cancer cells derived exosomes contribute to cancer progression through the modulation of tumor microenvironment. However, the effects of exosomes derived from gastric cancer cells on macrophages are not well understood. In this study, we investigated the biological role of gastric cancer cells derived exosomes in the activation of macrophages. We demonstrated that gastric cancer cells derived exosomes activated macrophages to express increased levels of proinflammatory factors, which in turn promoted tumor cell proliferation and migration. In addition, gastric cancer cells derived exosomes remarkably upregulated the phosphorylation of NF-κB in macrophages. Inhibiting the activation of NF-κB reversed the upregulation of proinflammatory factors in macrophages and blocked their promoting effects on gastric cancer cells. Moreover, we found that gastric cancer cells derived exosomes could also activate macrophages from human peripheral blood monocytes through the activation of NF-κB. In conclusion, our results suggest that gastric cancer cells derived exosomes stimulate the activation of NF-κB pathway in macrophages to promote cancer progression, which provides a potential therapeutic approach for gastric cancer by interfering with the interaction between exosomes and macrophages in tumor microenvironment.

Exosome-mediated transfer from the tumor microenvironment increases TGFβ signaling in squamous cell carcinoma

Transforming growth factor-beta (TGFβ) signaling in cancer is context dependent and acts either as a tumor suppressor or a tumor promoter. Loss of function mutation in TGFβ type II receptor (TβRII) is a frequent event in oral cavity squamous cell carcinoma (SCC). Recently, heterogeneity of TGFβ response has been described at the leading edge of SCC and this heterogeneity has been shown to influence stem cell renewal and drug resistance. Because exosome transfer from stromal to breast cancer cells regulates therapy resistance pathways we investigated whether exosomes contain components of the TGFβ signaling pathway and whether exosome transfer between stromal fibroblasts and tumor cells can influence TGFβ signaling in SCC. We demonstrate that exosomes purified from stromal fibroblasts isolated from patients with oral SCC contains TβRII. We also demonstrate that transfer of fibroblast exosomes increases TGFβ signaling in SCC keratinocytes devoid of TβRII which remain non-responsive to TGFβ ligand in the absence of exosome transfer. Overall our data show that stromal communication with tumor cells can direct TGFβ signaling in SCC.

Exosome-Mediated Metastasis: From Epithelial-Mesenchymal Transition to Escape from Immunosurveillance

Exosomes are extracellular signalosomes that facilitate eukaryotic intercellular communication under a wide range of normal physiological contexts. In malignancies, this regulatory circuit is co-opted to promote cancer cell survival and outgrowth. Tumour-derived exosomes (TDEs) carry a pro-EMT (epithelial-mesenchymal transition) programme including transforming growth factor beta (TGFβ), caveolin-1, hypoxia-inducible factor 1 alpha (HIF1α), and β-catenin that enhances the invasive and migratory capabilities of recipient cells, and contributes to stromal remodelling and premetastatic niche formation. The integrin expression patterns on TDEs appear to dictate their preferential uptake by organ-specific cells, implying a crucial role of this pathway in organotropic metastasis. Through the expression of immunomodulatory molecules such as CD39 and CD73, TDEs modify the immune contexture of the tumour microenvironment, which could have implications for immunotherapy. Hence, targeting TDE dysregulation pathways, such as the heparanase/syndecan-1 axis, could represent novel therapeutic strategies in the quest to conquer cancer.

The emerging roles of exosomes in tumor-stroma interaction

PURPOSE

The tumor-stroma interaction is critical for the development and progression of cancer. Cancer-associated fibroblasts (CAFs), one of the major components of the tumor stroma, can promote tumor growth and metastasis. Exosomes are secreted microvesicles that mediate cell-to-cell communication. Exosomal contents, including proteins, nucleic acids, and lipids, can be shuttled from donor cells to target cells. Recent studies suggest that exosomes play important roles in the tumor-stroma interaction. Herein, we review the multifaceted roles of exosomes in the tumor-stroma interaction and the underlying molecular mechanisms.

METHODS

Literature search for all relevant publications was performed on PubMed databases. The keywords of exosomes, tumor, stroma, CAFs, mesenchymal stem cells (MSCs) and other closely related terms were used for searching.

RESULTS

Tumor cell-derived exosomes induce the differentiation of fibroblasts and MSCs into CAFs. In turn, exosomes secreted by CAFs promote tumor growth, metastasis, and drug resistance through distinct mechanisms. Moreover, exosomes from stromal cells can be used as therapeutic vehicles for the delivery of anticancer drugs.

CONCLUSIONS

Tumor cells communicate with CAFs through exosomes, which establishes a bidirectional cross talk to promote tumor growth, metastasis, and drug resistance. Targeting exosomes in tumor-stroma interaction may have important implications for anticancer therapy.

Emerging molecular basis of hematogenous metastasis in gastric cancer

Lymphatic metastasis is commonly observed in gastric cancer (GC), but hematogenous metastasis is more likely responsible for the cancer-related mortality. Since Stephen Paget first introduced the “seed and soil hypothesis” a century ago, growing evidence recognizes that numerous essential secreted factors and signaling pathway effectors participate in the pre-metastatic niche formation and distant organ metastasis. The cross-talk between GC cells and surrounding microenvironment may consist of a series of interrelated steps, including epithelial mesenchymal transition, intravasation into blood vessels, circulating tumor cell translocation, and secondary organ metastasis. Secreted factors including vascular endothelial growth factor (VEGF), matrix metalloproteinases and cancer-derived extracellular vesicles, especially exosomes, are essential in formation of premetastatic niche. Circulating tumor cells and microRNAs represent as ‘‘metastatic intermediates’’ between primary tumors and sites of dissemination. Many biomarkers have been identified as novel metastatic markers and prognostic effectors. In addition, molecular therapy has been designed to target biomarkers such as growth factors (human epidermal growth factor receptor 2, VEGF) and chemokines, although they have not clearly proven to be effective in inhibiting GC metastasis in clinical trials. In this review, we will systematically discuss the emerging molecules and their microenvironment in hematogenous metastasis of GC, which may help us to find new therapeutic strategies in the future.

Extracellular Vesicles: Evolving Factors in Stem Cell Biology

Stem cells are proposed to continuously secrete trophic factors that potentially serve as mediators of autocrine and paracrine activities, associated with reprogramming of the tumor microenvironment, tissue regeneration, and repair. Hitherto, significant efforts have been made to understand the level of underlying paracrine activities influenced by stem cell secreted trophic factors, as little is known about these interactions. Recent findings, however, elucidate this role by reporting the effects of stem cell derived extracellular vesicles (EVs) that mimic the phenotypes of the cells from which they originate. Exchange of genetic information utilizing persistent bidirectional communication mediated by stem cell-EVs could regulate stemness, self-renewal, and differentiation in stem cells and their subpopulations. This review therefore discusses stem cell-EVs as evolving communication factors in stem cell biology, focusing on how they regulate cell fates by inducing persistent and prolonged genetic reprogramming of resident cells in a paracrine fashion. In addition, we address the role of stem cell-secreted vesicles in shaping the tumor microenvironment and immunomodulation and in their ability to stimulate endogenous repair processes during tissue damage. Collectively, these functions ensure an enormous potential for future therapies.

Cancer exosomes trigger mesenchymal stem cell differentiation into pro-angiogenic and pro-invasive myofibroblasts

Stromal fibroblasts become altered in response to solid cancers, to exhibit myofibroblastic characteristics, with disease promoting influence. Infiltrating mesenchymal stem cells (MSC) may contribute towards these changes, but the factors secreted by cancer cells that impact MSC differentiation are poorly understood.

We investigated the role of nano-metre sized vesicles (exosomes), secreted by prostate cancer cells, on the differentiation of bone-marrow MSC (BM-MSC), and the subsequent functional consequences of such changes. Purified exosomes impaired classical adipogenic differentiation, skewing differentiation towards alpha-smooth muscle actin (αSMA) positive myofibroblastic cells. A single exosomes treatment generated myofibroblasts secreting high levels of VEGF-A, HGF and matrix regulating factors (MMP-1, −3 and −13). Differentiated MSC had pro-angiogenic functions and enhanced tumour proliferation and invasivity assessed in a 3D co-culture model. Differentiation was dependent on exosomal-TGFβ, but soluble TGFβ at matched dose could not generate the same phenotype. Exosomes present in the cancer cell secretome were the principal factors driving this phenotype.

Prostate cancer exosomes dominantly dictate a programme of MSC differentiation generating myofibroblasts with functional properties consistent with disease promotion.

Tumorigenic hybrids between mesenchymal stem cells and gastric cancer cells enhanced cancer proliferation, migration and stemness

BACKGROUND

Emerging evidence indicates that inappropriate cell-cell fusion might contribute to cancer progression. Similarly, mesenchymal stem cells (MSCs) can also fuse with other cells spontaneously and capable of adopting the phenotype of other cells. The aim of our study was to investigate the role of MSCs participated cell fusion in the tumorigenesis of gastric cancer.

METHODS

We fused human umbilical cord mesenchymal stem cells (hucMSCs) with gastric cancer cells in vitro by polyethylene glycol (PEG), the hybrid cells were sorted by flow cytometer. The growth and migration of hybrids were assessed by cell counting, cell colony formation and transwell assays. The proteins and genes related to epithelial- mesenchymal transition and stemness were tested by western blot, immunocytochemistry and real-time RT-PCR. The expression of CD44 and CD133 was examined by immunocytochemistry and flow cytometry. The xenograft assay was used to evaluation the tumorigenesis of the hybrids.

RESULTS

The obtained hybrids exhibited epithelial- mesenchymal transition (EMT) change with down-regulation of E-cadherin and up-regulation of Vimentin, N-cadherin, α-smooth muscle actin (α-SMA), and fibroblast activation protein (FAP). The hybrids also increased expression of stemness factors Oct4, Nanog, Sox2 and Lin28. The expression of CD44 and CD133 on hybrid cells was stronger than parental gastric cancer cells. Moreover, the migration and proliferation of heterotypic hybrids were enhanced. In addition, the heterotypic hybrids promoted the growth abilities of gastric xenograft tumor in vivo.

CONCLUSIONS

Taken together, our results suggest that cell fusion between hucMSCs and gastric cancer cells could contribute to tumorigenic hybrids with EMT and stem cell-like properties, which may provide a flexible tool for investigating the roles of MSCs in gastric cancer.

Paracrine tumor signaling induces transdifferentiation of surrounding fibroblasts

Growth stimuli in cancer growth resemble those exhibited in wound healing. However, the process of nemosis is absent in cancer-associated fibroblasts (CAFs), which remain constitutively active. CAFs are present in almost all solid tumors but are most abundant in breast, prostate and pancreatic cancers. TGF-β1, TGF-β2, PDGF, IL-6, bFGF, reactive oxide species and protein kinase C are considered the key players in tumor-induced transdifferentiation of surrounding fibroblasts. Full-extent transdifferentiation was obtained only when the medium contained TGF-β1 or TGF-β2 (with or without other factors), whereas PDGF, bFGF or IL-6 (each alone) induced only partial transdifferentiation. Recent evidence suggests that the fibroblasts associated with primary cancers differ from those associated with metastases. The metastases-associated fibroblasts are converted by a metastasis-specific spectrum of factors. A large portion of paracrine tumor signaling is mediated by cancer cell-derived vesicles termed exosomes and microvesicles. The cancer cell-derived exosomes contain abundant and diverse proteomes and a number of signaling factors (TGF-ß1, TGF-ß2, IL-6, MMP2 and MMP9), particularly under hypoxic conditions. In contrast to the traditional view, the clonal expansion and selection of neoplastic cells should not be viewed outside the host body context. It is vital for a neoplastic cell to achieve the ability to re-program host body cells into CAFs and by this influence to modulate its microenvironment and receive positive feedback for growth and drug resistance. Neoplastic cells, which fail to develop such capacity, do not pass critical barriers in tumorigenesis and remain dormant and benign.

Stem cell-derived exosomes: roles in stromal remodeling, tumor progression, and cancer immunotherapy

Stem cells are known to maintain stemness at least in part through secreted factors that promote stem-like phenotypes in resident cells. Accumulating evidence has clarified that stem cells release nano-vesicles, known as exosomes, which may serve as mediators of cell-to-cell communication and may potentially transmit stem cell phenotypes to recipient cells, facilitating stem cell maintenance, differentiation, self-renewal, and repair. It has become apparent that stem cell-derived exosomes mediate interactions among stromal elements, promote genetic instability in recipient cells, and induce malignant transformation. This review will therefore discuss the potential of stem cell-derived exosomes in the context of stromal remodeling and their ability to generate cancer-initiating cells in a tumor niche by inducing morphologic and functional differentiation of fibroblasts into tumor-initiating fibroblasts. In addition, the immunosuppressive potential of stem cell-derived exosomes in cancer immunotherapy and their prospective applications in cell-free therapies in future translational medicine is discussed.

Exosomes in cancer: small particle, big player

Exosomes have emerged as a novel mode of intercellular communication. Exosomes can shuttle bioactive molecules including proteins, DNA, mRNA, as well as non-coding RNAs from one cell to another, leading to the exchange of genetic information and reprogramming of the recipient cells. Increasing evidence suggests that tumor cells release excessive amount of exosomes, which may influence tumor initiation, growth, progression, metastasis, and drug resistance. In addition, exosomes transfer message from tumor cells to immune cells and stromal cells, contributing to the escape from immune surveillance and the formation of tumor niche. In this review, we highlight the recent advances in the biology of exosomes as cancer communicasomes. We review the multifaceted roles of exosomes, the small secreted particles, in communicating with other cells within tumor microenvironment. Given that exosomes are cell type specific, stable, and accessible from body fluids, exosomes may provide promising biomarkers for cancer diagnosis and represent new targets for cancer therapy.