Microvesicles secreted by macrophages shuttle invasion-potentiating microRNAs into breast cancer cells

Electroporation-induced siRNA precipitation obscures the efficiency of siRNA loading into extracellular vesicles

Extracellular vesicles (EVs) are specialised endogenous carriers of proteins and nucleic acids and are involved in intercellular communication. EVs are therefore proposed as candidate drug delivery systems for the delivery of nucleic acids and other macromolecules. However, the preparation of EV-based drug delivery systems is hampered by the lack of techniques to load the vesicles with nucleic acids. In this work we have now characterised in detail the use of an electroporation method for this purpose. When EVs were electroporated with fluorescently labelled siRNA, siRNA retention was comparable with previously published results (20-25% based on fluorescence spectroscopy and fluorescence fluctuation spectroscopy), and electroporation with unlabelled siRNA resulted in significant siRNA retention in the EV pellet as measured by RT-PCR. Remarkably, when siRNA was electroporated in the absence of EVs, a similar or even greater siRNA retention was measured. Nanoparticle tracking analysis and confocal microscopy showed extensive formation of insoluble siRNA aggregates after electroporation, which could be dramatically reduced by addition of EDTA. Other strategies to reduce aggregate formation, including the use of cuvettes with conductive polymer electrodes and the use of an acidic citrate electroporation buffer, resulted in a more efficient reduction of siRNA precipitation than EDTA. However, under these conditions, siRNA retention was below 0.05% and no significant differences in siRNA retention could be measured between samples electroporated in the presence or absence of EVs. Our results show that electroporation of EVs with siRNA is accompanied by extensive siRNA aggregate formation, which may cause overestimation of the amount of siRNA actually loaded into EVs. Moreover, our data clearly illustrate that electroporation is far less efficient than previously described, and highlight the necessity for alternative methods to prepare siRNA-loaded EVs.

microRNA-mediated regulation of the tumor microenvironment

The tumor microenvironment includes cells such as fibroblasts, immune cells, endothelial cells, as well as extracellular matrix (ECM), proteases, and cytokines. Together, these components participate in a complex crosstalk with neoplastic tumor cells that affects growth, angiogenesis, and metastasis. MicroRNAs (miRNAs) are small, non-coding RNAs involved in post-transcriptional regulation of gene expression and have recently emerged as important players involved in regulating multiple aspects of cancer biology and the tumor microenvironment. Differential miRNA expression in both the epithelial and stromal compartments of tumors compared with normal tissue suggests that miRNAs are important drivers of tumorigenesis and metastasis. This review article summarizes our current understanding of the diverse roles of miRNAs involved in tumor microenvironment regulation and underscores the importance of miRNAs within multiple cell types that contribute to the hallmarks of cancer.

Exosomal Proteome Profiling: A Potential Multi-Marker Cellular Phenotyping Tool to Characterize Hypoxia-Induced Radiation Resistance in Breast Cancer

Radiation and drug resistance are significant challenges in the treatment of locally advanced, recurrent and metastatic breast cancer that contribute to mortality. Clinically, radiotherapy requires oxygen to generate cytotoxic free radicals that cause DNA damage and allow that damage to become fixed in the genome rather than repaired. However, approximately 40% of all breast cancers have hypoxic tumor microenvironments that render cancer cells significantly more resistant to irradiation. Hypoxic stimuli trigger changes in the cell death/survival pathway that lead to increased cellular radiation resistance. As a result, the development of noninvasive strategies to assess tumor hypoxia in breast cancer has recently received considerable attention. Exosomes are secreted nanovesicles that have roles in paracrine signaling during breast tumor progression, including tumor-stromal interactions, activation of proliferative pathways and immunosuppression. The recent development of protocols to isolate and purify exosomes, as well as advances in mass spectrometry-based proteomics have facilitated the comprehensive analysis of exosome content and function. Using these tools, studies have demonstrated that the proteome profiles of tumor-derived exosomes are indicative of the oxygenation status of patient tumors. They have also demonstrated that exosome signaling pathways are potentially targetable drivers of hypoxia-dependent intercellular signaling during tumorigenesis. This article provides an overview of how proteomic tools can be effectively used to characterize exosomes and elucidate fundamental signaling pathways and survival mechanisms underlying hypoxia-mediated radiation resistance in breast cancer.

Exosomes from retinal astrocytes contain antiangiogenic components that inhibit laser-induced choroidal neovascularization

Exosomes released from different types of host cells have different biological effects. We report that exosomes released from retinal astroglial cells (RACs) suppress retinal vessel leakage and inhibit choroidal neovascularization (CNV) in a laser-induced CNV model, whereas exosomes released from retinal pigmental epithelium do not. RAC exosomes inhibit the migration of macrophages and the tubule forming of mouse retinal microvascular endothelial cells. Further, we analyzed antiangiogenic components in RAC exosomes using an angiogenesis array kit and detected several endogenous inhibitors of angiogenesis exclusively present in RAC exosomes, such as endostatin. Moreover, blockade of matrix metalloproteinases in the cleavage of collagen XVIII to form endostatin using FN-439 reverses RAC exosome-mediated retinal vessel leakage. This study demonstrates that exosomes released from retinal tissue cells have different angiogenic effects, with exosomes from RACs containing antiangiogenic components that might protect the eye from angiogenesis and maintain its functional integrity. In addition, by identifying additional components and their functions of RAC exosomes, we might improve the antiangiogenic therapy for CNV in age-related macular degeneration and diabetic retinopathy.

The origin, function, and diagnostic potential of RNA within extracellular vesicles present in human biological fluids

We have previously demonstrated that tumor cells release membranous structures into their extracellular environment, which are termed exosomes, microvesicles or extracellular vesicles depending on specific characteristics, including size, composition and biogenesis pathway. These cell-derived vesicles can exhibit an array of proteins, lipids and nucleic acids derived from the originating tumor. This review focuses of the transcriptome (RNA) of these extracellular vesicles. Based on current data, these vesicular components play essential roles as conveyers of intercellular communication and mediators of many of the pathological conditions associated with cancer development, progression and therapeutic failures. These extracellular vesicles express components responsible for angiogenesis promotion, stromal remodeling, signal pathway activation through growth factor/receptor transfer, chemoresistance, and genetic exchange. These tumor-derived extracellular vesicles not only to represent a central mediator of the tumor microenvironment, but their presence in the peripheral circulation may serve as a surrogate for tumor biopsies, enabling real-time diagnosis and disease monitoring.

Trichomonas vaginalis exosomes deliver cargo to host cells and mediate host∶parasite interactions

Trichomonas vaginalis is a common sexually transmitted parasite that colonizes the human urogential tract where it remains extracellular and adheres to epithelial cells. Infections range from asymptomatic to highly inflammatory, depending on the host and the parasite strain. Here, we use a combination of methodologies including cell fractionation, immunofluorescence and electron microscopy, RNA, proteomic and cytokine analyses and cell adherence assays to examine pathogenic properties of T. vaginalis. We have found that T.vaginalis produces and secretes microvesicles with physical and biochemical properties similar to mammalian exosomes. The parasite-derived exosomes are characterized by the presence of RNA and core, conserved exosomal proteins as well as parasite-specific proteins. We demonstrate that T. vaginalis exosomes fuse with and deliver their contents to host cells and modulate host cell immune responses. Moreover, exosomes from highly adherent parasite strains increase the adherence of poorly adherent parasites to vaginal and prostate epithelial cells. In contrast, exosomes from poorly adherent strains had no measurable effect on parasite adherence. Exosomes from parasite strains that preferentially bind prostate cells increased binding of parasites to these cells relative to vaginal cells. In addition to establishing that parasite exosomes act to modulate host∶parasite interactions, these studies are the first to reveal a potential role for exosomes in promoting parasite∶parasite communication and host cell colonization.

Trichomoniasis, the most common non-viral sexually transmitted disease worldwide, infects over 275 million people annually. Infection results from the colonization of the human urogenital tract by the parasite Trichomonas vaginalis. To establish and maintain infection the parasite adheres to host cells, a process that is poorly understood. Here, we show that T. vaginalis secretes small vesicles called exosomes that are capable of fusing with and delivering their contents to host cells. Parasite exosomes were found to induce changes in the host cell and to mediate the interaction of T. vaginalis with host by increasing the adherence of the parasite to host cells. Exosomes have been primarily studied in mammalian cells where they have been shown to mediate intercellular communication and have been implicated in processes including development, antigen presentation and cancer metastasis. Our data extend the function of exosomes to mediating host∶parasite interactions, cellular communication between two species and promoting colonization of an extracellular parasite. Research on T. vaginalis exosomes holds the potential for developing applications that would allow exosomes to be used in detecting and diagnosing trichomoniasis and for targeting drugs to the site of infection.

Intercellular communication by exosome-derived microRNAs in cancer

The development of human cancers is a multistep process in which normal cells acquire characteristics that ultimately lead to their conversion into cancer cells. Many obstacles must be overcome for this process to occur; of these obstacles, is the ability to survive an inhospitable microenvironment. It is recognized that the intercommunication between tumor cells and their surrounding microenvironment is essential to overcoming this obstacle and for the tumor to progress, metastasize and establish itself at distant sites. Exosomes are membrane-derived vesicles that have recently been recognized as important mediators of intercellular communication, as they carry lipids, proteins, mRNAs and microRNAs that can be transferred to a recipient cell via fusion of the exosome with the target cell membrane. In the context of cancer cells, this process entails the transfer of cancer-promoting cellular contents to surrounding cells within the tumor microenvironment or into the circulation to act at distant sites, thereby enabling cancer progression. In this process, the transfer of exosomal microRNAs to a recipient cell where they can regulate target gene expression is of particular interest, both in understanding the basic biology of cancer progression and for the development of therapeutic approaches. This review discusses the exosome-mediated intercellular communication via microRNAs within the tumor microenvironment in human cancers, with a particular focus on breast cancer exosomes.

Circulating miRNAs: cell-cell communication function?

Nuclease resistant extracellular miRNAs have been found in all known biological fluids. The biological function of extracellular miRNAs remains questionable; however, strong evidence suggests that these miRNAs can be more than just byproducts of cellular activity. Some extracellular miRNA species might carry cell-cell signaling function during various physiological and pathological processes. In this review, we discuss the state-of-the-art in the field of intercellular miRNA transport and highlight current theories regarding the origin and the biological function of extracellular miRNAs.

MicroRNA transport: a new way in cell communication

MicroRNAs (miRNAs) can efficiently regulate gene expression by targeting mRNA to cause mRNA cleavage or translational repression. Growing evidence indicates that miRNAs exist not only in cells but also in a variety of body fluids, which stimulates substantial interest in the transport mechanism and regulating process of extracellular miRNAs. This article reviews the basic biogenesis of miRNAs in detail to explore the origin of extracellular miRNAs. Different miRNA transporters have been summarized (e.g., exosomes, microvesicles, apoptosis bodies, and RNA-binding proteins). In addition, we discuss the regulators affecting miRNA transport (e.g., ATP and ceramide) and the selection mechanism for different miRNA transporters. Studies about miRNA transporters and the transport mechanism are new and developing. With the progress of the research, new functions of extracellular miRNAs may be uncovered in the future.

The complexity, function and applications of RNA in circulation

Blood carries a wide array of biomolecules, including nutrients, hormones, and molecules that are secreted by cells for specific biological functions. The recent finding of stable RNA of both endogenous and exogenous origin in circulation raises a number of questions and opens a broad, new field: exploring the origins, functions, and applications of these extracellular RNA molecules. These findings raise many important questions, including: what are the mechanisms of export and cellular uptake, what is the nature and source of their stability, what molecules do they interact with in the blood, and what are the possible biological functions of the circulating RNA? This review summarizes some key recent developments in circulating RNA research and discusses some of the open questions in the field.

MicroRNA-containing microvesicles regulating inflammation in association with atherosclerotic disease

In addition to intracellular organelles, eukaryotic cells contain extracellular organelles which are released, or shed, into the microenvironment. In practice, most human studies have examined mixed populations containing both exosomes and shedding microvesicles (also called ectosomes or microparticles); only a few studies have rigorously distinguished between the two. Accordingly, in this review, exosomes and shedding microvesicles are collectively called microvesicles. The first aim of this review was to discuss the role of microvesicles in cell-to-cell communication in general and in specific interactions between cells in chronic inflammation associated with atherosclerotic disease. Hereby, we focused on cell-specific microvesicles derived from platelets, endothelial cells and monocyte and monocyte-derived cells. The latter were also found to be associated with inflammation in obesity and type 2 diabetes prior to atherosclerotic disease, and cancer. Our second aim was to discuss specific changes in microvesicle content in relation with inflammation associated with metabolic and atherosclerotic disease, and cancer. Because many studies supported the putative diagnostic value of microRNAs, we emphasized therein changes in microRNA content rather than protein or lipid content. The most interesting microRNAs in inflammatory microvesicles in association with metabolic and cardiovascular diseases were found to be the let-7 family, miR-17/92 family, miR-21, miR-29, miR-126, miR-133, miR-146, and miR-155. These data warrant further investigation of the potential of microvesicles as putative biomarkers and as novel carriers for the cell-specific transfer of microRNAs and other therapeutic agents.

Stromal cells in tumor microenvironment and breast cancer

Cancer is a systemic disease encompassing multiple components of both tumor cells themselves and host stromal cells. It is now clear that stromal cells in the tumor microenvironment play an important role in cancer development. Molecular events through which reactive stromal cells affect cancer cells can be defined so that biomarkers and therapeutic targets can be identified. Cancer-associated fibroblasts (CAFs) make up the bulk of cancer stroma and affect the tumor microenvironment such that they promote cancer initiation, angiogenesis, invasion, and metastasis. In breast cancer, CAFs not only promote tumor progression but also induce therapeutic resistance. Accordingly, targeting CAFs provides a novel way to control tumors with therapeutic resistance. This review summarizes the current understandings of tumor stroma in breast cancer with a particular emphasis on the role of CAFs and the therapeutic implications of CAFs. In addition, the effects of other stromal components such as endothelial cells, macrophages, and adipocytes in breast cancer are also discussed. Finally, we describe the biologic markers to categorize patients into a specific and confirmed subtype for personalized treatment.

Extracellular vesicles: biology and emerging therapeutic opportunities

Within the past decade, extracellular vesicles have emerged as important mediators of intercellular communication, being involved in the transmission of biological signals between cells in both prokaryotes and higher eukaryotes to regulate a diverse range of biological processes. In addition, pathophysiological roles for extracellular vesicles are beginning to be recognized in diseases including cancer, infectious diseases and neurodegenerative disorders, highlighting potential novel targets for therapeutic intervention. Moreover, both unmodified and engineered extracellular vesicles are likely to have applications in macromolecular drug delivery. Here, we review recent progress in understanding extracellular vesicle biology and the role of extracellular vesicles in disease, discuss emerging therapeutic opportunities and consider the associated challenges.

Signaling pathways in exosomes biogenesis, secretion and fate

Exosomes are small extracellular vesicles (30–100 nm) derived from the endosomal system, which have raised considerable interest in the last decade. Several studies have shown that they mediate cell-to-cell communication in a variety of biological processes. Thus, in addition to cell-to-cell direct interaction or secretion of active molecules, they are now considered another class of signal mediators. Exosomes can be secreted by several cell types and retrieved in many body fluids, such as blood, urine, saliva and cerebrospinal fluid. In addition to proteins and lipids, they also contain nucleic acids, namely mRNA and miRNA. These features have prompted extensive research to exploit them as a source of biomarkers for several pathologies, such as cancer and neurodegenerative disorders. In this context, exosomes also appear attractive as gene delivery vehicles. Furthermore, exosome immunomodulatory and regenerative properties are also encouraging their application for further therapeutic purposes. Nevertheless, several issues remain to be addressed: exosome biogenesis and secretion mechanisms have not been clearly understood, and physiological functions, as well as pathological roles, are far from being satisfactorily elucidated.

Reciprocal interactions between endothelial cells and macrophages in angiogenic vascular niches

The ability of macrophages to promote vascular growth has been associated with the secretion and local delivery of classic proangiogenic factors (e.g., VEGF-A and proteases). More recently, a series of studies have also revealed that physical contact of macrophages with growing blood vessels coordinates vascular fusion of emerging sprouts. Interestingly, the interactions between macrophages and vascular endothelial cells (ECs) appear to be bidirectional, such that activated ECs also support the expansion and differentiation of proangiogenic macrophages from myeloid progenitors. Here, we discuss recent findings suggesting that dynamic angiogenic vascular niches might also exist in vivo, e.g. in tumors, where sprouting blood vessels and immature myeloid cells like monocytes engage in heterotypic interactions that are required for angiogenesis. Finally, we provide an account of emerging mechanisms of cell-to-cell communication that rely on secreted microvesicles, such as exosomes, which can offer a vehicle for the rapid exchange of molecules and genetic information between macrophages and ECs engaged in angiogenesis.

MicroRNA-mediated control of macrophages and its implications for cancer

Deregulation of microRNAs (miRNAs) can drive oncogenesis, tumor progression, and metastasis by acting cell-autonomously in cancer cells. However, solid tumors are also infiltrated by large amounts of non-neoplastic stromal cells, including macrophages, which express several active miRNAs. Tumor-associated macrophages (TAMs) enhance angiogenic, immunosuppressive, invasive, and metastatic programming of neoplastic tissue and reduce host survival. Here, we review the role of miRNAs (including miR-155, miR-146, and miR-511) in the control of macrophage production and activation, and examine whether reprogramming miRNA activity in TAMs and/or their precursors might be effective for controlling tumor progression.

Proteomics, transcriptomics and lipidomics of exosomes and ectosomes

Mammalian cells secrete two types of extracellular vesicles either constitutively or in a regulated manner: exosomes (50-100 nm in diameter) released from the intracellular compartment and ectosomes (also called microvesicles, 100-1000 nm in diameter) shed directly from the plasma membrane. Extracellular vesicles are bilayered proteolipids enriched with proteins, mRNAs, microRNAs, and lipids. In recent years, much data have been collected regarding the specific components of extracellular vesicles from various cell types and body fluids using proteomic, transcriptomic, and lipidomic methods. These studies have revealed that extracellular vesicles harbor specific types of proteins, mRNAs, miRNAs, and lipids rather than random cellular components. These results provide valuable information on the molecular mechanisms involved in vesicular cargo-sorting and biogenesis. Furthermore, studies of these complex extracellular organelles have facilitated conceptual advancements in the field of intercellular communication under physiological and pathological conditions as well as for disease-specific biomarker discovery. This review focuses on the proteomic, transcriptomic, and lipidomic profiles of extracellular vesicles, and will briefly summarize recent advances in the biology, function, and diagnostic potential of vesicle-specific components.

Exosomes as nano-theranostic delivery platforms for gene therapy

Exosomes are biological membrane vesicles measuring 30 to 100 nm. They contain an abundance of small molecules like tetraspanins, receptors for targeting and adhesion, lipids, and RNA. They are secreted by most biological cells, and are involved in a plethora of physiological functions including, but not limited to, transport of genetic material, modulation of the immune system, and cell-to-cell communication. It has been further reported that exosomes utilize a mechanism similar to that of viruses for gaining entry into cells. Due to their viral-like transfection efficiency and inherent biological function, compelling evidence indicates that exosomes can be used as novel delivery platforms for gene therapy. Furthermore, RNA-containing exosomes derived from cells can serve as functional genetic biomarkers for diseases. This twin modality of therapeutic and diagnostic is termed theranostics in the emerging field of nanomedicine. Hence in this review, we seek to expound on the various facets of exosomes, highlighting their significance in and relevance to nano-theranostic platforms for gene therapy.

Exosomal tumor-suppressive microRNAs as novel cancer therapy: "exocure" is another choice for cancer treatment

MicroRNAs (miRNAs) act to fine-tune cellular responses in a variety of biological circumstances such as development, organogenesis, and homeostasis. The dysregulation of miRNA expression accelerates disease progression, including metabolic disease, immunological disease and cancer, through the gene network disorder. Therefore, understanding the miRNA maturation process may unravel the mechanisms of cancer malignancy; however, the life of miRNA has not been clarified. In this article, we summarize the recent findings regarding the novel forms of miRNA, especially secretory miRNAs, focusing on exosomal miRNAs. Recent research has revealed that exosomal miRNAs affect many aspects of physiological and pathological conditions, and may be useful as novel therapy. Here, we propose a method for the delivery of tumor-suppressive miRNAs to desired sites using exosomes, and we named this method "exocure".

The role of exosomes and microRNAs in senescence and aging

Senescence is viewed as a cellular counterpart to aging of tissues and organisms, characterized by an irreversible growth arrest and a combination of changes in cell morphology, function and behavior. microRNAs (miRNAs), the most studied small non-coding RNAs, play an important role in many biological processes by the regulation of gene expression. Recent evidence has shown that miRNAs are contained in exosomes that are tiny vesicles of endocytic origin and released by a variety of different cells as a means for cell-to-cell contact and information transfer. Exosomes and miRNAs have been found to participate in the complex networks of cellular senescence and contribute to aging. Here, we will give an overview on the involvement of secretory factors including exosomes and miRNA in the regulation of cellular senescence, demonstrating the potential role of exosomes and miRNAs in biological processes and signaling pathways of senescence and aging.

Neutral sphingomyelinase 2 (nSMase2)-dependent exosomal transfer of angiogenic microRNAs regulate cancer cell metastasis

The release of humoral factors between cancer cells and the microenvironmental cells is critical for metastasis; however, the roles of secreted miRNAs in non-cell autonomous cancer progression against microenvironmental cells remain largely unknown. Here, we demonstrate that the neutral sphyngomyelinase 2 (nSMase2) regulates exosomal microRNA (miRNA) secretion and promotes angiogenesis within the tumor microenvironment as well as metastasis. We demonstrate a requirement for nSMase2-mediated cancer cell exosomal miRNAs in the regulation of metastasis through the induction of angiogenesis in inoculated tumors. In addition, miR-210, released by metastatic cancer cells, was shown to transport to endothelial cells and suppress the expression of specific target genes, which resulted in enhanced angiogenesis. These findings suggest that the horizontal transfer of exosomal miRNAs from cancer cells can dictate the microenviromental niche for the benefit of the cancer cell, like “on demand system” for cancer cells.

Expression and Genetic Analysis of MicroRNAs Involved in Multiple Sclerosis

Evidence underlines the importance of microRNAs (miRNAs) in the pathogenesis of multiple sclerosis (MS). Based on the fact that miRNAs are present in human biological fluids, we previously showed that miR-223, miR-23a and miR-15b levels were downregulated in the sera of MS patients versus controls. Here, the expression levels of these candidate miRNAs were determined in peripheral blood mononuclear cells (PBMCs) and the serum of MS patients, in addition to three genotyped single nucleotide polymorphisms (SNPs). Mapping in the genomic regions of miR-223, miR-23a and miR-15b genes, 399 cases and 420 controls were tested. Expression levels of miR-223 and miR-23a were altered in PBMCs from MS patients versus controls. Conversely, there were no differences in the expression levels of miR-15b. A significantly decreased genotypic frequency of miR-223 rs1044165 T/T genotype was observed in MS patients. Moreover, the allelic frequency of miR-23a rs3745453 C allele was significantly increased in patients versus controls. In contrast, there were no differences in the distribution of miR-15b SNP. In conclusion, our results suggest that miR-223 and miR-23a could play a role in the pathogenesis of MS. Moreover, miR-223 rs1044165 polymorphism likely acts as a protective factor, while miR-23a rs3745453 variant seems to act as a risk factor for MS.

Complex role of microRNAs in HTLV-1 infections

Human T-lymphotropic virus 1 (HTLV-1) was the first human retrovirus to be discovered and is the causative agent of adult T-cell leukemia/lymphoma (ATL) and the neurodegenerative disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The importance of microRNA (miRNA) in the replicative cycle of several other viruses, as well as in the progression of associated pathologies, has been well established in the past decade. Moreover, involvement of miRNA alteration in the HTLV-1 life cycle, and in the progression of its related oncogenic and neurodegenerative diseases, has recently come to light. Several HTLV-1 derived proteins alter transcription factor functionalities, interact with chromatin remodelers, or manipulate components of the RNA interference (RNAi) machinery, thereby establishing various routes by which miRNA expression can be up- or down-regulated in the host cell. Furthermore, the mechanism of action through which dysregulation of host miRNAs affects HTLV-1 infected cells can vary substantially and include mRNA silencing via the RNA-induced silencing complex (RISC), transcriptional gene silencing, inhibition of RNAi components, and chromatin remodeling. These miRNA-induced changes can lead to increased cell survival, invasiveness, proliferation, and differentiation, as well as allow for viral latency. While many recent studies have successfully implicated miRNAs in the life cycle and pathogenesis of HTLV-1 infections, there are still significant outstanding questions to be addressed. Here we will review recent discoveries elucidating HTLV-1 mediated manipulation of host cell miRNA profiles and examine the impact on pathogenesis, as well as explore future lines of inquiry that could increase understanding in this field of study.

Cell-free microRNAs as diagnostic, prognostic, and predictive biomarkers for lung cancer

Lung cancer is the most common cancer worldwide, accounting for over 1.37 million deaths annually. The clinical outcome and management of lung cancer patients could be substantially improved by the implementation of non-invasive biomarker assays for the early detection, prognosis as well as prediction and monitoring of treatment response. MicroRNAs (miRNAs) have been implicated in the regulation of virtually all signaling circuits within a cell and their dysregulation has been shown to play an essential role in the development and progression of cancer. Recently, miRNAs were found to be released into the circulation and to exist there in a remarkably stable form. Furthermore, various cancers were shown to leave specific miRNA fingerprints in the blood of patients suggesting that cell-free miRNAs could serve as non-invasive biomarkers for the detection or monitoring of cancer and putative therapeutic targets. Since that, a considerable effort has been devoted to decode the information carried by circulating miRNAs. In the current review, we give an insight into the mechanisms of miRNA release into the bloodstream, their putative functional significance and systematically review the studies focused on the identification of cell-free miRNAs with the diagnostic, prognostic, and predictive significance in lung cancer and discuss their potential clinical utility.

Tumor-derived microvesicles: the metastasomes

Metastasis is the leading cause of cancer death, yet it is mechanistically considered a very inefficient process suggesting the presence of some sort of (e.g. systemic) routes for fuelling the process. The pre-metastatic niche formation is described as one such metastasis promoting route. Now, the emerging potentials of tumor-derived microvesicles (TDMVs), not only in formulating the pre-metastatic niche, but also conferring neoplastic phenotypes onto normal cells, has integrated new concepts into the field. Here, we note as an ancillary proposition that, exerting functional disturbances in other sites, TDMVs (we have termed them metastasomes) may aid foundation of the secondary lesions via two seemingly interrelated models: (i) tumor-organ-training (TOTr), training a proper niche for the growth of the disseminated tumor cells; (ii) tumor-organ-targeting (TOTa), contribution to the propagation of the transformed phenotype via direct or indirect (TOTr-mediated disturbed stroma) transformation and/or heightened growth/survival states of the normal resident cells in the secondary organs. Respecting the high content of the RNA molecules (particularly microRNAs) identified in the secretory MVs, they may play crucial parts in such "malignant trait" spreading system. That is, the interactions between tumor tissue-specific RNA signatures, being transferred via metastasomes, and the cell-type/tissue-specific RNA stockrooms in other areas may settle a unique outcome in each organ. Thus, serving as tumor-organ matchmakers, the RNA molecules may also play substantial roles in the seeding and tropism of the process.

Exosome-mediated transfer of miR-133b from multipotent mesenchymal stromal cells to neural cells contributes to neurite outgrowth

Multipotent mesenchymal stromal cells (MSCs) have potential therapeutic benefit for the treatment of neurological diseases and injury. MSCs interact with and alter brain parenchymal cells by direct cell-cell communication and/or by indirect secretion of factors and thereby promote functional recovery. In this study, we found that MSC treatment of rats subjected to middle cerebral artery occlusion (MCAo) significantly increased microRNA 133b (miR-133b) level in the ipsilateral hemisphere. In vitro, miR-133b levels in MSCs and in their exosomes increased after MSCs were exposed to ipsilateral ischemic tissue extracts from rats subjected to MCAo. miR-133b levels were also increased in primary cultured neurons and astrocytes treated with the exosome-enriched fractions released from these MSCs. Knockdown of miR-133b in MSCs confirmed that the increased miR-133b level in astrocytes is attributed to their transfer from MSCs. Further verification of this exosome-mediated intercellular communication was performed using a cel-miR-67 luciferase reporter system and an MSC-astrocyte coculture model. Cel-miR-67 in MSCs was transferred to astrocytes via exosomes between 50 and 100 nm in diameter. Our data suggest that the cel-miR-67 released from MSCs was primarily contained in exosomes. A gap junction intercellular communication inhibitor arrested the exosomal microRNA communication by inhibiting exosome release. Cultured neurons treated with exosome-enriched fractions from MSCs exposed to 72 hours post-MCAo brain extracts significantly increased the neurite branch number and total neurite length. This study provides the first demonstration that MSCs communicate with brain parenchymal cells and may regulate neurite outgrowth by transfer of miR-133b to neural cells via exosomes.

Circulating microRNAs: new biomarkers in diagnosis, prognosis and treatment of cancer (review)

MicroRNAs (miRNAs) are small non-coding, endogenous, single-stranded RNAs. MiRNAs have been implicated in different areas such as the immune response, neural development, DNA repair, apoptosis, oxidative stress response and cancer. However, while the majority of miRNAs are found intracellularly, a significant number of miRNAs have been observed outside of cells, including various body fluids. Circulating miRNAs function as 'extracellular communication RNAs' that play an important role in cell proliferation and differentiation. MiRNA regulation is essential to many cellular processes, and escape from this regulatory network seems to be a common characteristic of several disease processes and malignant transformation. The interest in circulating miRNAs reflects in fact their central role in regulation of gene expression and the implication of miRNA-specific aberrant expression in the pathogenesis of cancer, cardiac, metabolic, neurologic, immune-related diseases as well as others. In our review we aimed to summarize the data related to the action of cellular miRNAs on the onset of various diseases, thus bringing together some of the latest information available on the role of circulating miRNAs. Additionally, the role of circulating miRNAs could be particularly relevant in the context of neoplastic diseases. At least 79 miRNAs have been reported as plasma or serum miRNA biomarkers of solid and hematologic tumors. Circulating miRNA profiling could improve the diagnosis of cancer, and could predict outcome for cancer patients, while the profiling of alterations in circulating miRNA that may signal a predisposition to cancer, could also be a therapeutic target in these patients.

Small RNA deep sequencing reveals a distinct miRNA signature released in exosomes from prion-infected neuronal cells

Prion diseases are transmissible neurodegenerative disorders affecting both humans and animals. The cellular prion protein, PrP^C, and the abnormal infectious form, PrP^Sc, are found associated with exosomes, which are small 50–130 nm vesicles released from cells. Exosomes also contain microRNAs (miRNAs), a class of non-coding RNA, and have been utilized to identify miRNA signatures for diagnosis of disease. While some miRNAs are deregulated in prion-infected brain tissue, the role of miRNA in circulating exosomes released during prion disease is unknown. Here, we investigated the miRNA profile in exosomes released from prion-infected neuronal cells. We performed the first small RNA deep sequencing study of exosomes and demonstrated that neuronal exosomes contain a diverse range of RNA species including retroviral RNA repeat regions, messenger RNA fragments, transfer RNA fragments, non-coding RNA, small nuclear RNA, small nucleolar RNA, small cytoplasmic RNA, silencing RNA as well as known and novel candidate miRNA. Significantly, we show that exosomes released by prion-infected neuronal cells have increased let-7b, let-7i, miR-128a, miR-21, miR-222, miR-29b, miR-342-3p and miR-424 levels with decreased miR-146 a levels compared to non-infected exosomes. Overall, these results demonstrate that circulating exosomes released during prion infection have a distinct miRNA signature that can be utilized for diagnosis and understanding pathogenic mechanisms in prion disease.

Extracellular miRNAs: the mystery of their origin and function

Mature miRNAs are 19-24 nucleotide noncoding RNAs that post-transcriptionally regulate gene expression in living cells by mediating targeted hydrolysis and translation inhibition of mRNAs. In recent years, miRNAs have been detected in a variety of biological fluids as extracellular nuclease-resistant entities. Importantly, extracellular circulating miRNAs are aberrantly expressed in blood plasma or serum during the course of many diseases, including cancer, and are promising noninvasive biomarkers. However, the biological function of extracellular miRNAs remains questionable. In this article, we summarise the current theories regarding extracellular miRNA origin and function, and suggest that these miRNAs are mostly byproducts of cellular activity. Nevertheless, some extracellular miRNA species might also carry cell-cell signaling function.

Exosomes: new players in cell-cell communication

Exosomes are small membrane vesicles of endosomal origin, which are secreted from a variety of cell types. During the 1980s exosomes were first described as organelles to remove cell debris and unwanted molecules. The discovery that exosomes contain proteins, messenger and microRNAs suggests a role as mediators in cell-to-cell communication. Exosomes can be transported between different cells and influence physiological pathways in the recipient cells. In the present review, we will summarize the biological function of exosomes and their involvement in physiological and pathological processes. Moreover, the potential clinical application of exosomes as biomarkers and therapeutic tools will be discussed.

Cell-to-cell miRNA transfer: from body homeostasis to therapy

The role of non-protein coding RNAs (ncRNAs), microRNAs (miRNAs) in particular, as fine-tuners of both pathological and physiological processes is no longer a matter of debate. With the recent discovery of miRNAs in a wide variety of body fluids and considering them as tools employed in horizontal gene transfer between cells, a new horizon opens in the field of diagnosis and therapeutics. Circulating miRNAs not only enable the communication among cells, but also provide insight into the pathological and physiological state of the originating cells. In this review we summarize the recent advances made in this field, arguing for compelling translation of miRNAs into clinical practice. Moreover, we provide overview of their characteristics and how they impact the evolution of tumor microenvironment and cell-to-cell communication, advancing the idea that miRNAs may function as hormones.

Microvesicles/exosomes as potential novel biomarkers of metabolic diseases

Biomarkers are of tremendous importance for the prediction, diagnosis, and observation of the therapeutic success of common complex multifactorial metabolic diseases, such as type II diabetes and obesity. However, the predictive power of the traditional biomarkers used (eg, plasma metabolites and cytokines, body parameters) is apparently not sufficient for reliable monitoring of stage-dependent pathogenesis starting with the healthy state via its initiation and development to the established disease and further progression to late clinical outcomes. Moreover, the elucidation of putative considerable differences in the underlying pathogenetic pathways (eg, related to cellular/tissue origin, epigenetic and environmental effects) within the patient population and, consequently, the differentiation between individual options for disease prevention and therapy - hallmarks of personalized medicine - plays only a minor role in the traditional biomarker concept of metabolic diseases. In contrast, multidimensional and interdependent patterns of genetic, epigenetic, and phenotypic markers presumably will add a novel quality to predictive values, provided they can be followed routinely along the complete individual disease pathway with sufficient precision. These requirements may be fulfilled by small membrane vesicles, which are so-called exosomes and microvesicles (EMVs) that are released via two distinct molecular mechanisms from a wide variety of tissue and blood cells into the circulation in response to normal and stress/pathogenic conditions and are equipped with a multitude of transmembrane, soluble and glycosylphosphatidylinositol-anchored proteins, mRNAs, and microRNAs. Based on the currently available data, EMVs seem to reflect the diverse functional and dysfunctional states of the releasing cells and tissues along the complete individual pathogenetic pathways underlying metabolic diseases. A critical step in further validation of EMVs as biomarkers will rely on the identification of unequivocal correlations between critical disease states and specific EMV signatures, which in future may be determined in rapid and convenient fashion using nanoparticle-driven biosensors.

Exosomes and microvesicles: extracellular vesicles for genetic information transfer and gene therapy

Exosomes and microvesicles are extracellular nanovesicles released by most but not all cells. They are specifically equipped to mediate intercellular communication via the transfer of genetic information, including the transfer of both coding and non-coding RNAs, to recipient cells. As a result, both exosomes and microvesicles play a fundamental biological role in the regulation of normal physiological as well as aberrant pathological processes, via altered gene regulatory networks and/or via epigenetic programming. For example, microvesicle-mediated genetic transfer can regulate the maintenance of stem cell plasticity and induce beneficial cell phenotype modulation. Alternatively, such vesicles play a role in tumor pathogenesis and the spread of neurodegenerative diseases via the transfer of specific microRNAs and pathogenic proteins. Given this natural property for genetic information transfer, the possibility of exploiting these vesicles for therapeutic purposes is now being investigated. Stem cell-derived microvesicles appear to be naturally equipped to mediate tissue regeneration under certain conditions, while recent evidence suggests that exosomes might be harnessed for the targeted delivery of human genetic therapies via the introduction of exogenous genetic cargoes such as siRNA. Thus, extracellular vesicles are emerging as potent genetic information transfer agents underpinning a range of biological processes and with therapeutic potential.

Possible role of exosomes containing RNA in mediating nontargeted effect of ionizing radiation

Communication between irradiated and un-irradiated (bystander) cells can cause damage in cells that are not directly targeted by ionizing radiation, a process known as the bystander effect. Bystander effects can also lead to chromosomal/genomic instability within the progeny of bystander cells, similar to the progeny of directly irradiated cells. The factors that mediate this cellular communication can be transferred between cells via gap junctions or released into the extracellular media following irradiation, but their nature has not been fully characterized. In this study we tested the hypothesis that the bystander effect mediator contains an RNA molecule that may be carried by exosomes. MCF7 cells were irradiated with 2 Gy of X rays and the extracellular media was harvested. RNase treatment abrogated the ability of the media to induce early and late chromosomal damage in bystander cells. Furthermore, treatment of bystander cells with exosomes isolated from this media increased the levels of genomic damage. These results suggest that the bystander effect, and genomic instability, are at least in part mediated by exosomes and implicate a role for RNA.

Plasma microRNAs, miR-223, miR-21 and miR-218, as novel potential biomarkers for gastric cancer detection

Background

MicroRNAs (miRNAs), endogenous small non-coding RNAs, are stably detected in human plasma. Early diagnosis of gastric cancer (GC) is very important to improve the therapy effect and prolong the survival of patients. We aimed to identify whether four miRNAs (miR-223, miR-21, miR-218 and miR-25) closely associated with the tumorigenesis or metastasis of GC can serve as novel potential biomarkers for GC detection.

Methodology

We initially measured the plasma levels of the four miRNAs in 10 GC patients and 10 healthy control subjects by quantitative reverse transcription polymerase chain reaction (qRT-PCR), and then compared plasma miRNA results with the expressions in cancer tissues from eight GC patients. Finally, the presence of miR-223, miR-21 and miR-218 in the plasma was validated in 60 GC patients and 60 healthy control subjects, and the areas under the receiver operating characteristic (ROC) curves of these miRNAs were analyzed.

Results

We found that the plasma levels of miR-223 (P<0.001) and miR-21 (P<0.001) were significantly higher in GC patients than in healthy controls, while miR-218 (P<0.001) was significantly lower. The ROC analyses yielded the AUC values of 0.9089 for miR-223, 0.7944 for miR-21 and 0.7432 for miR-218, and combined ROC analysis revealed the highest AUC value of 0.9531 in discriminating GC patients from healthy controls. Moreover, the plasma levels of miR-223 (P<0.001) and miR-21 (P = 0.003) were significantly higher in GC patients with stage I than in healthy controls. Furthermore, the plasma levels of miR-223 were significantly higher in GC patients with helicobacter pylori (Hp) infection than those without (P = 0.014), and significantly higher in healthy control subjects with Hp infection than those without (P = 0.016).

Conclusions

Plasma miR-223, miR-21 and miR-218 are novel potential biomarkers for GC detection.

Role of exosomes/microvesicles in the nervous system and use in emerging therapies

Extracellular membrane vesicles (EMVs) are nanometer sized vesicles, including exosomes and microvesicles capable of transferring DNAs, mRNAs, microRNAs, non-coding RNAs, proteins, and lipids among cells without direct cell-to-cell contact, thereby representing a novel form of intercellular communication. Many cells in the nervous system have been shown to release EMVs, implicating their active roles in development, function, and pathologies of this system. While substantial progress has been made in understanding the biogenesis, biophysical properties, and involvement of EMVs in diseases, relatively less information is known about their biological function in the normal nervous system. In addition, since EMVs are endogenous vehicles with low immunogenicity, they have also been actively investigated for the delivery of therapeutic genes/molecules in treatment of cancer and neurological diseases. The present review summarizes current knowledge about EMV functions in the nervous system under both physiological and pathological conditions, as well as emerging EMV-based therapies that could be applied to the nervous system in the foreseeable future.

Macrophages in tumor microenvironments and the progression of tumors

Macrophages are widely distributed innate immune cells that play indispensable roles in the innate and adaptive immune response to pathogens and in-tissue homeostasis. Macrophages can be activated by a variety of stimuli and polarized to functionally different phenotypes. Two distinct subsets of macrophages have been proposed, including classically activated (M1) and alternatively activated (M2) macrophages. M1 macrophages express a series of proinflammatory cytokines, chemokines, and effector molecules, such as IL-12, IL-23, TNF-α, iNOS and MHCI/II. In contrast, M2 macrophages express a wide array of anti-inflammatory molecules, such as IL-10, TGF-β, and arginase1. In most tumors, the infiltrated macrophages are considered to be of the M2 phenotype, which provides an immunosuppressive microenvironment for tumor growth. Furthermore, tumor-associated macrophages secrete many cytokines, chemokines, and proteases, which promote tumor angiogenesis, growth, metastasis, and immunosuppression. Recently, it was also found that tumor-associated macrophages interact with cancer stem cells. This interaction leads to tumorigenesis, metastasis, and drug resistance. So mediating macrophage to resist tumors is considered to be potential therapy.

Dynamic education of macrophages in different areas of human tumors

Human tumor tissues can often be anatomically classified into areas of cancer nest, invading edge, and peritumoral stroma, each with distinct compositions and functional properties. Macrophages (Mφ) constitute a major component of the leukocyte infiltrate in tumors. These cells are derived from circulating monocytes, and in response to environmental signals, they exhibit distinct phenotypes with diverse functions. Soluble factors derived from cancer cells can alter the normal developmental process of Mφ that is intended to trigger transient early activation of monocytes in the peritumoral region, which in turn induces formation of suppressive Mφ in cancer nests. The activated monocytes in the peritumoral region attenuated the T-cell response by expressing B7-H1, and were superior to the suppressive tumor Mφ in inducing Th17 expansion, and thus repurpose the inflammatory response away from anti-tumor immunity (the sword) and towards tissue remodeling and proangiogenic pathways (a plowshare). In contrast, the suppressive Mφ can induce the production of Tregs in cancer nest. Accordingly, angiogenesis was most active at the invading edge, which was situated close to the peritumoral stroma with activated Mφ and the density of these activated monocytes is selectively associated with vascular invasion and metastasis in patients with hepatocellular carcinoma. These data reveal an intriguing mechanism in which human Th17 cells are generated and regulated by a fine-tuned collaborative action between different types of immune cells in distinct tumor microenvironments. These results give important new insights into the distinct role of macrophages in human tumor progression which would be helpful for the rational design of novel immune-based anticancer therapies.

Microparticle conferred microRNA profiles--implications in the transfer and dominance of cancer traits

BACKGROUND

Microparticles (MPs) are membrane vesicles which are released from normal and malignant cells following a process of budding and detachment from donor cells. MPs contain surface antigens, proteins and genetic material and serve as vectors of intercellular communication. MPs comprise the major source of systemic RNA including microRNA (miRNA), the aberrant expression of which appears to be associated with stage, progression and spread of many cancers. Our previous study showed that MPs carry both transcripts and miRNAs associated with the acquisition of multidrug resistance in cancer.

RESULTS

Herein, we expand on our previous finding and demonstrate that MPs carry the transcripts of the membrane vesiculation machinery (floppase and scramblase) as well as nucleic acids encoding the enzymes essential for microRNA biogenesis (Drosha, Dicer and Argonaute). We also demonstrate using microarray miRNA profiling analysis, the selective packaging of miRNAs (miR-1228*, miR-1246, miR-1308, miR-149*, miR-455-3p, miR-638 and miR-923) within the MP cargo upon release from the donor cells.

CONCLUSIONS

These miRNAs are present in both haematological and non-haematological cancer cells and are involved in pathways implicated in cancer pathogenesis, membrane vesiculation and cascades regulated by ABC transporters. Our recent findings reinforce our earlier reports that MP transfer 're-templates' recipient cells so as to reflect donor cell traits. We now demonstrate that this process is likely to occur via a process of selective packaging of nucleic acid species, including regulatory nucleic acids upon MP vesiculation. These findings have significant implications in understanding the cellular basis governing the intercellular acquisition and dominance of deleterious traits in cancers.

MicroRNAs are universal regulators of differentiation, activation, and polarization of microglia and macrophages in normal and diseased CNS

MicroRNAs (miRNAs) are a class of small (∼22 nucleotides) noncoding RNAs involved in the regulation of gene expression at the post-translational level. It is estimated that 30-90% of human genes are regulated by miRNAs, which makes these molecules of great importance for cell growth, activation, and differentiation. Microglia is CNS-resident cells of a myeloid lineage that play an important role in immune surveillance and are actively involved in many neurologic pathologies. Although the exact origin of microglia remains enigmatic, it is established that primitive macrophages from a yolk sac populate the brain and spinal cord in normal conditions throughout development. During various pathological events such as neuroinflammation, bone marrow derived myeloid cells also migrate into the CNS. Within the CNS, both primitive macrophages from the yolk sac and bone marrow derived myeloid cells acquire a specific phenotype upon interaction with other cell types within the CNS microenvironment. The factors that drive differentiation of progenitors into microglia and control the state of activation of microglia and bone marrow-derived myeloid cells within the CNS are not well understood. In this review we will summarize the role of miRNAs during activation and differentiation of myeloid cells. The role of miR-124 in the adaptation of microglia and macrophages to the CNS microenvironment will be further discussed. We will also summarize the role of miRNAs as modulators of activation of microglia and microphages. Finally, we will describe the role of miR-155 and miR-124 in the polarization of macrophages towards classically and alternatively activated phenotypes.

Impact of biofluid viscosity on size and sedimentation efficiency of the isolated microvesicles

Microvesicles are nano-sized lipid vesicles released by all cells in vivo and in vitro. They are released physiologically under normal conditions but their rate of release is higher under pathological conditions such as tumors. Once released they end up in the systemic circulation and have been found and characterized in all biofluids such as plasma, serum, cerebrospinal fluid, breast milk, ascites, and urine. Microvesicles represent the status of the donor cell they are released from and they are currently under intense investigation as a potential source for disease biomarkers. Currently, the “gold standard” for isolating microvesicles is ultracentrifugation, although alternative techniques such as affinity purification have been explored. Viscosity is the resistance of a fluid to a deforming force by either shear or tensile stress. The different chemical and molecular compositions of biofluids have an effect on its viscosity and this could affect movements of the particles inside the fluid. In this manuscript we addressed the issue of whether viscosity has an effect on sedimentation efficiency of microvesicles using ultracentrifugation. We used different biofluids and spiked them with polystyrene beads and assessed their recovery using the Nanoparticle Tracking Analysis. We demonstrate that MVs recovery inversely correlates with viscosity and as a result, sample dilutions should be considered prior to ultracentrifugation when processing any biofluids.

Exosomes: vehicles for the transfer of toxic proteins associated with neurodegenerative diseases?

Exosomes are small membranous vesicles secreted by a number of cell types including neurons and can be isolated from conditioned cell media or bodily fluids such as urine and plasma. Exosome biogenesis involves the inward budding of endosomes to form multivesicular bodies (MVB). When fused with the plasma membrane, the MVB releases the vesicles into the extracellular environment as exosomes. Proposed functions of these vesicles include roles in cell–cell signaling, removal of unwanted proteins, and the transfer of pathogens between cells. One such pathogen which exploits this pathway is the prion, the infectious particle responsible for the transmissible neurodegenerative diseases such as Creutzfeldt–Jakob disease (CJD) of humans or bovine spongiform encephalopathy (BSE) of cattle. Similarly, exosomes are also involved in the processing of the amyloid precursor protein (APP) which is associated with Alzheimer’s disease. Exosomes have been shown to contain full-length APP and several distinct proteolytically cleaved products of APP, including Aβ. In addition, these fragments can be modulated using inhibitors of the proteases involved in APP cleavage. These observations provide further evidence for a novel pathway in which PrP and APP fragments are released from cells. Other proteins such as superoxide dismutase I and alpha-synuclein (involved in amyotrophic lateral sclerosis and Parkinson’s disease, respectively) are also found associated with exosomes. This review will focus on the role of exosomes in neurodegenerative disorders and discuss the potential of these vesicles for the spread of neurotoxicity, therapeutics, and diagnostics for these diseases.

Myeloma as a model for the process of metastasis: implications for therapy

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by the presence of multiple myelomatous "omas" throughout the skeleton, indicating that there is continuous trafficking of tumor cells to multiple areas in the bone marrow niches. MM may therefore represent one of the best models to study cell trafficking or cell metastasis. The process of cell metastasis is described as a multistep process, the invasion-metastasis cascade. This involves cell invasion, intravasation into nearby blood vessels, passage into the circulation, followed by homing into predetermined distant tissues, the formation of new foci of micrometastases, and finally the growth of micrometastasis into macroscopic tumors. This review discusses the significant advances that have been discovered in the complex process of invasion-metastasis in epithelial carcinomas and cell trafficking in hematopoietic stem cells and how this process relates to progression in MM. This progression is mediated by clonal intrinsic factors that mediate tumor invasiveness as well as factors present in the tumor microenvironment that are permissive to oncogenic proliferation. Therapeutic agents that target the different steps of cell dissemination and progression are discussed. Despite the significant advances in the treatment of MM, better therapeutic agents that target this metastatic cascade are urgently needed.

Exosomal miRNAs: Biological Properties and Therapeutic Potential

MicroRNAs (miRNAs), small non-coding regulatory RNAs that regulate gene expression at the post-transcriptional level, are master regulators of a wide array of cellular processes. Altered miRNA expression could be a determinant of disease development and/or progression and manipulation of miRNA expression represents a potential avenue of therapy. Exosomes are cell-derived extracellular vesicles that promote cell–cell communication and immunoregulatory functions. These “bioactive vesicles” shuttle various molecules, including miRNAs, to recipient cells. Inappropriate release of miRNAs from exosomes may cause significant alterations in biological pathways that affect disease development, supporting the concept that miRNA-containing exosomes could serve as targeted therapies for particular diseases. This review briefly summarizes recent advances in the biology, function, and therapeutic potential of exosomal miRNAs.

The biology of personalized cancer medicine: facing individual complexities underlying hallmark capabilities

It is a time of great promise and expectation for the applications of knowledge about mechanisms of cancer toward more effective and enduring therapies for human disease. Conceptualizations such as the hallmarks of cancer are providing an organizing principle with which to distill and rationalize the abject complexities of cancer phenotypes and genotypes across the spectrum of the human disease. A countervailing reality, however, involves the variable and often transitory responses to most mechanism-based targeted therapies, returning full circle to the complexity, arguing that the unique biology and genetics of a patient's tumor will in the future necessarily need to be incorporated into the decisions about optimal treatment strategies, the frontier of personalized cancer medicine. This perspective highlights considerations, metrics, and methods that may prove instrumental in charting the landscape of evaluating individual tumors so to better inform diagnosis, prognosis, and therapy. Integral to the consideration is remarkable heterogeneity and variability, evidently embedded in cancer cells, but likely also in the cell types composing the supportive and interactive stroma of the tumor microenvironment (e.g., leukocytes and fibroblasts), whose diversity in form, regulation, function, and abundance may prove to rival that of the cancer cells themselves. By comprehensively interrogating both parenchyma and stroma of patients' cancers with a suite of parametric tools, the promise of mechanism-based therapy may truly be realized.

Lipid-based carriers of microRNAs and intercellular communication

PURPOSE OF REVIEW

Extracellular microRNAs (miRNAs) are uniquely stable in plasma, and the levels of specific circulating miRNAs can differ with disease. Extracellular miRNAs are associated with lipid-based carriers and lipid-free proteins. miRNAs can be transferred from cell-to-cell by lipid-based carriers and affect gene expression. This review summarizes recent studies that demonstrate the transfer of miRNA between cells and their potential role in intercellular communication.

RECENT FINDINGS

Microvesicles, exosomes, apoptotic bodies, lipoproteins, and large microparticles contain miRNAs. Recent studies have demonstrated that miRNAs are transferred between dendritic cells, hepatocellular carcinoma cells, and adipocytes in lipid-based carriers. miRNAs are also transferred from T cells to antigen-presenting cells, from stem cells to endothelial cells and fibroblasts, from macrophages to breast cancer cells, and from epithelial cells to hepatocytes in lipid-based carriers. The cellular export of miRNAs in lipid-based carriers is regulated by the ceramide pathway, and the delivery of lipid-associated miRNAs to recipient cells is achieved by various routes, including endocytotic uptake, membrane-fusion, and scavenger receptors.

SUMMARY

Cellular miRNAs are exported in and to lipid-based carriers (vesicles and lipoprotein particles) and transferred to recipient cells with gene expression changes as intercellular communication.