The role of exosomes and miRNAs in drug‐resistance of cancer cells

Chemotherapy, one of the principal approaches for cancer patients, plays a crucial role in controlling tumor progression. Clinically, tumors reveal a satisfactory response following the first exposure to the chemotherapeutic drugs in treatment. However, most tumors sooner or later become resistant to even chemically unrelated anticancer agents after repeated treatment. The reduced drug accumulation in tumor cells is considered one of the significant mechanisms by decreasing drug permeability and/or increasing active efflux (pumping out) of the drugs across the cell membrane. The mechanisms of treatment failure of chemotherapeutic drugs have been investigated, including drug efflux, which is mediated by extracellular vesicles (EVs). Exosomes, a subset of EVs with a size range of 40–150 nm and a lipid bilayer membrane, can be released by all cell types. They mediate specific cell‐to‐cell interactions and activate signaling pathways in cells they either fuse with or interact with, including cancer cells. Exosomal RNAs are heterogeneous in size but enriched in small RNAs, such as miRNAs. In the primary tumor microenvironment, cancer‐secreted exosomes and miRNAs can be internalized by other cell types. MiRNAs loaded in these exosomes might be transferred to recipient niche cells to exert genome‐wide regulation of gene expression. How exosomal miRNAs contribute to the development of drug resistance in the context of the tumor microenvironment has not been fully described. In this review, we will highlight recent studies regarding EV‐mediated microRNA delivery in formatting drug resistance. We also suggest the use of EVs as an advancing method in antiresistance treatment.     

Exosome Mediated Cancer Therapeutic Approach:Present Status and Future Prospectives

The unique extracellular vesicles (EVs) or exosomes formed by the sequential invagination of the plasma membrane are diverse and encompass important constituents with biological functions. Speculations on its cell independent biological functions are significant and pose them as vital biomarkers and as drug delivery vehicles especially in cancer. EVs possess theragnostic values and are known to elicit specific immune response. Exosomes can also serve as potential nanocarriers for delivering miRNA, siRNA, anti-cancer drugs and membrane-associated proteins. Exosomes play a crucial role in regulating tumour progression, metastasis, and angiogenesis. This review thus portrays the multiple facets of exosomes, in concert with the source for exosomes production and further on its regulation and intercellular communication. The review also explores the recent advances, present status and the future prospective in the application of exosomes in cancer therapeutics and cancer diagnostics.     

Exosomes in development,metastasis and drug resistance of breast cancer

Transport through the cell membrane can be divided into active, passive and vesicular types (exosomes). Exosomes are nano‐sized vesicles released by a variety of cells. Emerging evidence shows that exosomes play a critical role in cancers. Exosomes mediate communication between stroma and cancer cells through the transfer of nucleic acid and proteins. It is demonstrated that the contents and the quantity of exosomes will change after occurrence of cancers. Over the last decade, growing attention has been paid to the role of exosomes in the development of breast cancer, the most life‐threatening cancer in women. Breast cancer could induce salivary glands to secret specific exosomes, which could be used as biomarkers in the diagnosis of early breast cancer. Exosome‐delivered nucleic acid and proteins partly facilitate the tumorigenesis, metastasis and resistance of breast cancer. Exosomes could also transmit anti‐cancer drugs outside breast cancer cells, therefore leading to drug resistance. However, exosomes are effective tools for transportation of anti‐cancer drugs with lower immunogenicity and toxicity. This is a promising way to establish a drug delivery system.     

MicroRNAs delivered by extracellular vesicles: an emerging resistance mechanism for breast cancer

Resistance to chemotherapy and endocrine therapy as well as targeted drugs is a major problem in treatment of breast cancer. Over the last decades, emerging studies have revealed that extracellular vesicles, which are chronically released by breast cancer cells and surrounding stromal cells, influence the action of most commonly used therapeutics. Such modulatory effects have been related to the transport of biologically active molecules including proteins and functional microRNAs. In this review, we highlight recent studies regarding extracellular vesicle-mediated microRNA delivery in formatting drug resistance. We also suggest the use of extracellular vesicles as a promising method in antiresistance treatment.     

Extracellular vesicle-encapsulated microRNA-296-3p from cancer-associated fibroblasts promotes ovarian cancer development through regulation of the PTEN/AKT and SOCS6/STAT3 pathways

Cancer-associated fibroblasts (CAFs), as important components of the tumor microenvironment, can regulate intercellular communication and tumor development by secreting extracellular vesicles (EVs). However, the role of CAF-derived EVs in ovarian cancer has not been fully elucidated. Here, using an EV-microRNA sequencing analysis, we reveal specific overexpression of microRNA (miR)-296-3p in activated CAF-derived EVs, which can be transferred to tumor cells to regulate the malignant phenotypes of ovarian cancer cells. Moreover, overexpression of miR-296-3p significantly promotes the proliferation, migration, invasion, and drug resistance of ovarian cancer cells in vitro, as well as tumor growth in vivo, while its inhibition has the opposite effects. Further mechanistic studies reveal that miR-296-3p promotes ovarian cancer progression by directly targeting PTEN and SOCS6 and activating AKT and STAT3 signaling pathways. Importantly, increased expression of miR-296-3p encapsulated in plasma EVs is closely correlated with tumorigenesis and chemoresistance in patients with ovarian cancer. Our results highlight the cancer-promoting role of CAF-derived EVs carrying miR-296-3p in ovarian cancer progression for the first time, and suggest that miR-296-3p encapsulated in CAF-derived EVs could be a diagnostic biomarker and therapeutic target for ovarian cancer.     

Extracellular vesicles: General features and usefulness in diagnosis and therapeutic management of colorectal cancer

In the world, among all type of cancers, colorectal cancer (CRC) is the third most commonly diagnosed in males and the second in females. In most of cases, (RP1) patients’ prognosis limitation with malignant tumors can be attributed to delayed diagnosis of the disease. Identification of patients with early-stage disease leads to more effective therapeutic interventions. Therefore, new screening methods and further innovative treatment approaches are mandatory as they may lead to an increase in progression-free and overall survival rates. For the last decade, the interest in extracellular vesicles (EVs) research has exponentially increased as EVs generation appears to be a universal feature of every cell that is strongly involved in many mechanisms of cell-cell communication either in physiological or pathological situations. EVs can cargo biomolecules, such as lipids, proteins, nucleic acids and generate transmission signal through the intercellular transfer of their content. By this mechanism, tumor cells can recruit and modify the adjacent and systemic microenvironment to support further invasion and dissemination. This review intends to cover the most recent literature on the role of EVs production in colorectal normal and cancer tissues. Specific attention is paid to the use of EVs for early CRC diagnosis, follow-up, and prognosis as EVs have come into the spotlight of research as a high potential source of ‘liquid biopsies’. The use of EVs as new targets or nanovectors as drug delivery systems for CRC therapy is also summarized.     

Chemotherapy-Resistant Metastatic Breast Cancer

OPINION STATEMENT: Remaining the most common cancer in women through the 21(st) century, breast cancer and the development of treatment strategies continue to highlight advances made in our understanding of the pathogenesis of cancer development and resistance to therapies. Despite significant progress in the treatment of breast cancer, resistance to chemotherapeutic agents remains a consistent obstacle in terms of treatment success. Anthracyclines, first used over 30?years ago, and the more recent addition of taxanes to the treatment armamentarium are integral components for both newly diagnosed and recurrent breast cancer. Unfortunately, along with other constituents of combination chemotherapy for metastatic breast cancer, these agents ultimately become ineffective in controlling disease. With the emergence of a resistant phenotype, tumors are deemed to be drug resistant - frequently multidrug resistant (MDR). A number of processes have been identified that can underlie clinical drug resistance; observations stemming largely from in vitro laboratory-based studies in human cancer cell lines. Recognized mechanisms of resistance include altered expression of the adenosine triphosphate-binding cassette (ABC) superfamily of transporters, alteration in DNA repair pathways, mutations in cellular targets, resistance to initiation of the apoptotic pathway and the development of constitutively activated signaling pathways. As our understanding of mechanisms of resistance expands, the ability to select specific drugs or drug combinations specific to the phenotype of the cancer will become more specific. Illustrative of these advancements are the reported benefits from the use of newer microtubule-targeting agents in triple negative breast cancer, such as eribulin and ixabepilone; drugs which may be less susceptible to common pathways of drug resistance. Likewise, the combination usage of agents which intersect in receptor crosstalk, such as between the estrogen receptor and the mammalian target of rapamycin (mTOR), have demonstrated synergy in antitumor effects. The recent report of exemestane used in combination with everolimus, have shown great promise in this regard. For patients with HER2 positive disease, a combination approach with trastuzumab and investigational agents such as pertuzumab appear to result in a more complete blockage of HER2 signaling, and improved progression free survival. Thus, as our understanding of the interconnectedness of signaling pathways in breast cancer improves, the ability to rationally design appropriate chemotherapy regimens and delay emerging resistance will improve.     

Understanding Drug Resistance in Breast Cancer with Mathematical Oncology

Chemotherapy is the mainstay of treatment for the majority of patients with breast cancer but results in only 26 % of patients with distant metastasis living 5 years past treatment in the United States, largely because of drug resistance. The complexity of drug resistance calls for an integrated approach of mathematical modeling and experimental investigation to develop quantitative tools that reveal insights into drug resistance mechanisms, predict chemotherapy efficacy, and identify novel treatment approaches. This paper reviews recent modeling work for understanding cancer drug resistance through the use of computer simulations of molecular signaling networks and cancerous tissues, with a particular focus on breast cancer. These mathematical models are developed by drawing on current advances in molecular biology, physical characterization of tumors, and emerging drug delivery methods (eg, nanotherapeutics). We focus our discussion on representative modeling works that have provided quantitative insight into chemotherapy resistance in breast cancer and how drug resistance can be overcome or minimized to optimize chemotherapy treatment. We also discuss future directions of mathematical modeling in understanding drug resistance.     

Advances in Breast Cancer Management and Extracellular Vesicle Research,a Bibliometric Analysis

Extracellular vesicles transport variable content and have crucial functions in cell–cell communication. The role of extracellular vesicles in cancer is a current hot topic, and no bibliometric study has ever analyzed research production regarding their role in breast cancer and indicated the trends in the field. In this way, we aimed to investigate the trends in breast cancer management involved with extracellular vesicle research. Articles were retrieved from Scopus, including all the documents published concerning breast cancer and extracellular vesicles. We analyzed authors, journals, citations, affiliations, and keywords, besides other bibliometric analyses, using R Studio version 3.6.2. and VOSviewer version 1.6.0. A total of 1151 articles were retrieved, and as the main result, our analysis revealed trending topics on biomarkers of liquid biopsy, drug delivery, chemotherapy, autophagy, and microRNA. Additionally, research related to extracellular vesicles in breast cancer has been focused on diagnosis, treatment, and mechanisms of action of breast tumor-derived vesicles. Future studies are expected to explore the role of extracellular vesicles on autophagy and microRNA, besides investigating the application of extracellular vesicles from liquid biopsies for biomarkers and drug delivery, enabling the development and validation of therapeutic strategies for specific cancers.     

miR-134 in extracellular vesicles reduces triple-negative breast cancer aggression and increases drug sensitivity

Exosomes (EVs) have relevance in cell-to-cell communication carrying pro-tumorigenic factors that participate in oncogenesis and drug resistance and are proposed to have potential as self-delivery systems. Advancing on our studies of EVs in triple-negative breast cancer, here we more comprehensively analysed isogenic cell line variants and their EV populations, tissues cell line variants and their EV populations, as well as breast tumour and normal tissues. Profiling 384 miRNAs showed EV miRNA content to be highly representative of their cells of origin. miRNAs most substantially down-regulated in aggressive cells and their EVs originated from 14q32. Analysis of miR-134, the most substantially down-regulated miRNA, supported its clinical relevance in breast tumours compared to matched normal breast tissue. Functional studies indicated that miR-134 controls STAT5B which, in turn, controls Hsp90. miR-134 delivered by direct transfection into Hs578Ts(i)₈ cells (in which it was greatly down-regulated) reduced STAT5B, Hsp90, and Bcl-2 levels, reduced cellular proliferation, and enhanced cisplatin-induced apoptosis. Delivery via miR-134-enriched EVs also reduced STAT5B and Hsp90, reduced cellular migration and invasion, and enhanced sensitivity to anti-Hsp90 drugs. While the differing effects achieved by transfection or EV delivery are likely to be, at least partly, due to specific amounts of miR-134 delivered by these routes, these EV-based studies identified miRNA-134 as a potential biomarker and therapeutic for breast cancer.     

Mechanisms and strategies to overcome chemotherapy resistance in metastatic breast cancer

Resistance to chemotherapeutic agents is a significant issue in the management of patients with breast cancer. Anthracyclines, although first used over 30 years ago, are still part of the standard chemotherapy for this disease. Subsequently, the taxanes heralded a new era in chemotherapy and have been used extensively in the treatment of metastatic breast cancer. Unfortunately, along with other constituents of combination chemotherapy for metastatic breast cancer such as cyclophosphamide, these agents become increasingly ineffective in progressive disease and tumours are then deemed to be drug resistant - frequently multidrug resistant. A number of processes have been identified that can underlie clinical drug resistance, and these largely stem from in vitro laboratory-based studies in human cancer cell lines. A large proportion of these studies have focused on multidrug resistance associated with resistance to natural product anticancer agents due to the presence of putative drug transporter proteins such as P-glycoprotein, MRP1, and BCRP. Other studies have highlighted mechanisms whereby breast cancer cells show resistance to chemotherapeutic agents by altered regulation of DNA repair processes, with many other factors influencing drug detoxification processes and altering drug targets. New developmental agents with improved specificity for tumour cells, such as trastuzumab, and those with low susceptibility to common tumour-resistance mechanisms, such as ixabepilone, have provided new hope for effective treatment of breast cancer. Ixabepilone is the first in a new class of neoplastics, the epothilones. With these developments in therapy, and the technology of gene expression profiling, the future holds more promise for the development of more effective treatment for metastatic breast cancer.     

miRNA在乳腺癌化疗耐药中的作用

总结近期国内外有关miRNA在乳腺癌化疗耐药中作用的研究进展。应用Pubmed和CNKI期刊全文数据库检索系统以“miRNA、乳腺癌和化疗耐药”为关键词,检索2000年1月至2012年10月有关在乳腺癌化疗耐药中作用的文献。从乳腺癌化疗耐药入手,阐述乳腺癌化疗耐药的特点、机制,并着重对miRNA在乳腺癌化疗耐药中的作用进行分析。miRNA通过多种途径参与乳腺癌的化疗耐药。本文具体综述了一些以不同机制参与肿瘤耐药的miRNA,及其具体参与耐药的途径。探讨了血清miRNA作为肿瘤标记物的潜在临床利用性。结论:深入研究血清miRNA在乳腺癌耐药中的作用和机制,必将为乳腺癌的靶向治疗掀起一个新的篇章。      

Extracellular vesicles transmitted miR-31-5p promotes sorafenib resistance by targeting MLH1 in renal cell carcinoma

Sorafenib provides survival benefits in patients with advanced renal cell carcinoma (RCC), but its use is hampered by acquired drug resistance. It is important to fully clarify the molecular mechanisms of sorafenib resistance, which can help to avoid, delay or reverse drug resistance. Extracellular vesicles (EVs) can mediate intercellular communication by delivering effector molecules between cells. Here, we studied whether EVs are involved in sorafenib resistance of RCC and its possible molecular mechanisms. Using differential centrifugation, EVs were isolated from established sorafenib-resistant RCC cells (786-0 and ACHN), and EVs derived from sorafenib-resistant cells were uptaken by sensitive parental RCC cells and thus promoted drug resistance. Elevated exogenous miR-31-5p within EVs effectively downregulated MutL homolog 1 (MLH1) expression and thus promoted sorafenib resistance in vitro. Mice experiments also confirmed that miR-31-5p could mediate drug sensitivity in vivo. In addition, low expression of MLH1 was observed in sorafenib-resistant RCC cells and upregulation of MLH1 expression restored the sensitivity of resistant cell lines to sorafenib. Finally, miR-31-5p level in circulating EVs of RCC patients with progressive disease (PD) during sorafenib therapy was higher when compared to that in the pretherapy status. In conclusion, EVs shuttled miR-31-5p can transfer resistance information from sorafenib-resistant cells to sensitive cells by directly targeting MLH1, and thus magnify the drug resistance information to the whole tumor. Furthermore, miR-31-5p and MLH1 could be promising predictive biomarkers and therapeutic targets to prevent sorafenib resistance.     

microRNA在乳腺癌耐药中的作用

乳腺癌是危害全球女性健康的主要疾病,而乳腺癌患者对现有治疗方法产生获得性耐药成为目前乳腺癌临床治疗所面临的难题.微小RNA (miRNA)是一种内源性的非编码RNA,它参与调控多种生物学过程,包括细胞增殖、侵袭、转移、上皮间质转化和耐药等.获得性耐药包含多种复杂机制,可通过特定miRNA的异常表达影响细胞相关蛋白的表达、抗肿瘤药物与相应靶点的结合以及凋亡相关途径引起乳腺癌耐药.本文将重点关注在乳腺癌内分泌治疗、化疗、分子靶向治疗发生获得性耐药中表达异常的miRNA.相信miRNA能够成为乳腺癌临床诊断与治疗以及对抗获得性耐药的生物标志物和新的治疗靶点.     

Impact,mechanisms, and novel chemotherapy strategies for overcoming resistance to anthracyclines and taxanes in metastatic breast cancer

Despite advances in treatment of patients with metastatic breast cancer (MBC), prognosis remains poor and median survival is 2–3 years. Resistance to antineoplastics mediated by many factors, potentially including overexpression of drug efflux proteins or altered β-tubulin isotype expression limits the effectiveness of MBC chemotherapy. Capecitabine, approved for anthracycline- and taxane-resistant MBC, has produced modest responses, highlighting the need for more effective treatments for MBC resistant to multiple chemotherapeutic agents. Agents with potential to reverse drug resistance have not proven effective. Albumin-bound paclitaxel is a formulation that may enhance delivery to tumor tissues. Conversely, ixabepilone, an epothilone analog, has been reported to have lower susceptibility to at least some mechanisms of tumor resistance and clinical activity in resistant/refractory MBC. The topoisomerase-I inhibitor irinotecan also has low cross-resistance with other antineoplastics, and has shown some activity against refractory MBC. Development of new agents and identification of genetic biomarkers in translational studies promise to improve management of patients with resistant/refractory breast cancer.     

The forces driving cancer extracellular vesicle secretion

The discovery that cancer cells discharge vast quantities of extracellular vesicles (EVs), underscored the explosion of the EV field. A large body of evidence now supports their onco-functionality in an array of contexts; stromal crosstalk, immune evasion, metastatic site priming, and drug resistance - justifying therapeutic intervention. The current bottleneck is a lack of clear understanding of why and how EV biogenesis ramps up in cancer cells, and hence where exactly avenues for intervention may reside. We know that EVs also play an array of physiological roles, therefore effective anticancer inhibition requires a target distinct enough from physiology to achieve efficacy. Taking the perspective that EV upregulation may be a consequence of the tumor landscape, we examine classic mutational events and tumor characteristics for EV regulators. All the while, aiming to illuminate topics worth further research in therapeutic development.     

Extracellular vesicles from bone marrow mesenchymal stem/stromal cells transport tumor regulatory microRNA,proteins, and metabolites

Human mesenchymal stem/stromal cells (hMSCs) have been shown to support breast cancer cell proliferation and metastasis, partly through their secretome. hMSCs have a remarkable ability to survive for long periods under stress, and their secretome is tumor supportive. In this study, we have characterized the cargo of extracellular vesicular (EV) fraction (that is in the size range of 40-150nm) of serum deprived hMSCs (SD-MSCs). Next Generation Sequencing assays were used to identify small RNA secreted in the EVs, which indicated presence of tumor supportive miRNA. Further assays demonstrated the role of miRNA-21 and 34a as tumor supportive miRNAs. Next, proteomic assays revealed the presence of ≈150 different proteins, most of which are known tumor supportive factors such as PDGFR-β, TIMP-1, and TIMP-2. Lipidomic assays verified presence of bioactive lipids such as sphingomyelin. Furthermore, metabolite assays identified the presence of lactic acid and glutamic acid in EVs. The co-injection xenograft assays using MCF-7 breast cancer cells demonstrated the tumor supportive function of these EVs. To our knowledge this is the first comprehensive -omics based study that characterized the complex cargo of extracellular vesicles secreted by hMSCs and their role in supporting breast cancers.     

Advances in the treatment of non-small cell lung cancer

While there have been advances in the treatment of lung cancer, they have been marginal in comparison with recent advances in the chemotherapy and molecularly targeted treatment of breast cancer, colorectal cancer and genitourinary cancer. Lung cancer is an extremely difficult disease to treat, and to obtain positive results and to develop new standard treatment. The results of clinical trial on gefitinib and erlotinib suggest that the evaluation of molecular target drugs seems to be quite difficult in unselected patient population and may be different from cytotoxic drugs. We need to find out specific molecular biomarkers for each drug. With global studies in view, it will be essential to obtain even more significant results by sophisticated clinical trials in selected patient populations and contribute to improving the treatment outcome of lung cancer patients.     

Extracellular Vesicles As miRNA Nano-Shuttles: Dual Role in Tumor Progression

Tumor-derived extracellular vesicles (EVs) have a pleiotropic role in cancer, interacting with target cells of the tumor microenvironment, such as fibroblasts, immune and endothelial cells. EVs can modulate tumor progression, angiogenic switch, metastasis, and immune escape. These vesicles are nano-shuttles containing a wide spectrum of miRNAs that contribute to tumor progression. MiRNAs contained in extracellular vesicles (EV-miRNAs) are disseminated in the extracellular space and are able to influence the expression of target genes with either tumor suppressor or oncogenic functions, depending on both parental and target cells. Metastatic cancer cells can balance their oncogenic potential by expressing miRNAs with oncogenic function, whilst exporting miRNAs with tumor suppressor roles out of the cells. Importantly, treatment of cancer cells with specific natural and chemical compounds could induce the elimination of miRNAs with oncogenic function, thereby reducing their aggressiveness. In this review, we discuss the mechanisms by which EV-miRNAs, acting as miRNAs with oncogenic or tumor suppressor functions, could contribute to cancer progression.