Elevated Concentration of Microvesicles Isolated from Peripheral Blood in Breast Cancer Patients

Extracellular vesicles from women with breast cancer promote an epithelial-mesenchymal transition-like process in mammary epithelial cells MCF10A

Extracellular vesicles (EVs) mediate many stages of tumor progression including angiogenesis, escape from immune surveillance, and extracellular matrix degradation. We studied whether EVs from plasma of women with breast cancer are able to induce an epithelial-mesenchymal transition (EMT) process in mammary epithelial cells MCF10A. Our findings demonstrate that EVs from plasma of breast cancer patients induce a downregulation of E-cadherin expression and an increase of vimentin and N-cadherin expression. Moreover, EVs induce migration and invasion, as well as an increase of NFκB-DNA binding activity and MMP-2 and MMP-9 secretions. In summary, our findings demonstrate, for the first time, that EVs from breast cancer patients induce an EMT-like process in human mammary non-tumorigenic epithelial cells MCF10A.

The hypoxic tumor microenvironment: A driving force for breast cancer progression

Intratumoral hypoxia is a common finding in breast cancer and is associated with a significantly increased risk of metastasis and patient mortality. Hypoxia-inducible factors activate the transcription of a large battery of genes encoding proteins that promote primary tumor vascularization and growth, stromal cell recruitment, extracellular matrix remodeling, premetastatic niche formation, cell motility, local tissue invasion, extravasation at sites of metastasis, and maintenance of the cancer stem cell phenotype that is required to generate secondary tumors. Recent preclinical studies suggest that the combination of cytotoxic chemotherapy with drugs that inhibit hypoxia-inducible factors may improve outcome for women with triple-negative breast cancer. This article is part of a Special Issue entitled: Tumor Microenvironment Regulation of Cancer Cell Survival, Metastasis, Inflammation, and Immune Surveillance edited by Peter Ruvolo and Gregg L. Semenza.

Avoiding false positive antigen detection by flow cytometry on blood cell derived microparticles: the importance of an appropriate negative control

BACKGROUND

Microparticles (MPs), also called microvesicles (MVs) are plasma membrane-derived fragments with sizes ranging from 0.1 to 1μm. Characterization of these MPs is often performed by flow cytometry but there is no consensus on the appropriate negative control to use that can lead to false positive results.

MATERIALS AND METHODS

We analyzed MPs from platelets, B-cells, T-cells, NK-cells, monocytes, and chronic lymphocytic leukemia (CLL) B-cells. Cells were purified by positive magnetic-separation and cultured for 48h. Cells and MPs were characterized using the following monoclonal antibodies (CD19,20 for B-cells, CD3,8,5,27 for T-cells, CD16,56 for NK-cells, CD14,11c for monocytes, CD41,61 for platelets). Isolated MPs were stained with annexin-V-FITC and gated between 300nm and 900nm. The latex bead technique was then performed for easy detection of MPs. Samples were analyzed by Transmission (TEM) and Scanning Electron microscopy (SEM).

RESULTS

Annexin-V positive events within a gate of 300-900nm were detected and defined as MPs. Our results confirmed that the characteristic antigens CD41/CD61 were found on platelet-derived-MPs validating our technique. However, for MPs derived from other cell types, we were unable to detect any antigen, although they were clearly expressed on the MP-producing cells in the contrary of several data published in the literature. Using the latex bead technique, we confirmed detection of CD41,61. However, the apparent expression of other antigens (already deemed positive in several studies) was determined to be false positive, indicated by negative controls (same labeling was used on MPs from different origins).

CONCLUSION

We observed that mother cell antigens were not always detected on corresponding MPs by direct flow cytometry or latex bead cytometry. Our data highlighted that false positive results could be generated due to antibody aspecificity and that phenotypic characterization of MPs is a difficult field requiring the use of several negative controls.

Hyaluronan-coated extracellular vesicles--a novel link between hyaluronan and cancer

The synthesis of hyaluronan (HA) on the plasma membrane is a unique and still partly mysterious way of macromolecular biosynthesis. HA forms pericellular coats around many cell types and accumulates in the extracellular matrix (ECM) of growing and renewing tissues. It is secreted to high concentrations in body fluids with antifriction properties like pleural, peritoneal, and synovial fluids, but is also detectable in plasma, saliva, and urine. In pathological states, like cancer and inflammation, the amount of HA is increased around cells, in the ECM, and in the body fluids. HA is an indicator of poor prognosis for cancer patients and creates a favorable environment for cellular growth and motility. The recent finding that HA-coated extracellular vesicles act both as a product of HA synthase activity and as special vehicles for HA, and perhaps carry signals important for malignant growth, provides a novel link between HA and cancer. HA could be carried on the surface of these vesicles in tissues and body fluids, creating beneficial environments by itself, or by associated molecules, for the invasion and metastasis of cancer cells. The HA-coated plasma membrane protrusions and vesicles shed from them are potential biomarkers in cancer and other HA-associated disease states.

Extracellular vesicles: potential applications in cancer diagnosis, prognosis, and epidemiology

Both normal and diseased cells continuously shed extracellular vesicles (EVs) into extracellular space, and the EVs carry molecular signatures and effectors of both health and disease. EVs reflect dynamic changes that are occurring in cells and tissue microenvironment in health and at a different stage of a disease. EVs are capable of altering the function of the recipient cells. Trafficking and reciprocal exchange of molecular information by EVs among different organs and cell types have been shown to contribute to horizontal cellular transformation, cellular reprogramming, functional alterations, and metastasis. EV contents may include tumor suppressors, phosphoproteins, proteases, growth factors, bioactive lipids, mutant oncoproteins, oncogenic transcripts, microRNAs, and DNA sequences. Therefore, the EVs present in biofluids offer unprecedented, remote, and non-invasive access to crucial molecular information about the health status of cells, including their driver mutations, classifiers, molecular subtypes, therapeutic targets, and biomarkers of drug resistance. In addition, EVs may offer a non-invasive means to assess cancer initiation, progression, risk, survival, and treatment outcomes. The goal of this review is to highlight the current status of information on the role of EVs in cancer, and to explore the utility of EVs for cancer diagnosis, prognosis, and epidemiology.

Extracellular vesicles from MDA-MB-231 breast cancer cells stimulated with linoleic acid promote an EMT-like process in MCF10A cells

Extracellular vesicles (EVs) are membrane-limited vesicles secreted by normal and malignant cells and their function is dependent on the cargo they carry and the cell type from which they originate. Moreover, EVs mediate many stages of tumor progression including angiogenesis, escape from immune surveillance and extracellular matrix degradation. Linoleic acid (LA) is an essential polyunsaturated fatty acid that induces expression of plasminogen activator inhibitor-1, proliferation, migration and invasion in breast cancer cells. However the role of secreted EVs from MDA-MB-231 cells stimulated with LA like mediator of the epithelial-mesenchymal-transition (EMT) process in mammary non-tumorigenic epithelial cells MCF10A remains to be studied. In the present study, we demonstrate that treatment of MDA-MB-231 cells for 48 h with 90 µM LA does not induce an increase in the number of secreted EVs. In addition, EVs isolated from supernatants of MDA-MB-231 stimulated for 48 h with 90 µM LA induce a transient down-regulation of E-cadherin expression, and an increase of Snail1 and 2, Twist1 and 2, Sip1, vimentin and N-cadherin expression in MCF10A cells. EVs also promote an increase of MMP-2 and -9 secretions, an increase of NFκB-DNA binding activity, migration and invasion in MCF10A cells. In summary, our findings demonstrate, for the first time, that EVs isolated from supernatants of MDA-MB-231 stimulated for 48 h with 90 µM LA induce an EMT-like process in MCF10A cells.

Hypoxia-inducible factors and RAB22A mediate formation of microvesicles that stimulate breast cancer invasion and metastasis

Extracellular vesicles such as exosomes and microvesicles (MVs) are shed by cancer cells, are detected in the plasma of cancer patients, and promote cancer progression, but the molecular mechanisms regulating their production are not well understood. Intratumoral hypoxia is common in advanced breast cancers and is associated with an increased risk of metastasis and patient mortality that is mediated in part by the activation of hypoxia-inducible factors (HIFs). In this paper, we report that exposure of human breast cancer cells to hypoxia augments MV shedding that is mediated by the HIF-dependent expression of the small GTPase RAB22A, which colocalizes with budding MVs at the cell surface. Incubation of naïve breast cancer cells with MVs shed by hypoxic breast cancer cells promotes focal adhesion formation, invasion, and metastasis. In breast cancer patients, RAB22A mRNA overexpression in the primary tumor is associated with decreased overall and metastasis-free survival and, in an orthotopic mouse model, RAB22A knockdown impairs breast cancer metastasis.

Microvesicles mediate transfer of P-glycoprotein to paclitaxel-sensitive A2780 human ovarian cancer cells, conferring paclitaxel-resistance

The overexpression of P-glycoprotein (P-gp) causes resistance to chemotherapy in human ovarian cancer. However, the underlying mechanism remains unclear. In the present study, we showed that, at membrane-bound protein level, P-gp was 'shared' between human ovarian cancer cells by the intercellular transfer of microvesicles (MVs). Paclitaxel-resistant human ovarian cancer cells (A2780/PTX) readily formed and released P-gp-containing MVs into the extracellular space compared with the wild-type parental line (A2780/WT). Shedding MVs bound to the chemosensitive A2780/WT cells in a time- and dose-dependent manner, transferring P-gp via the microenvironment. MV-mediated transfer of P-gp led to redistribution of the chemotherapeutic drug adriamycin in recipient cells (A2780/WT), which displayed 5- and 5-fold higher resistance to adriamycin and paclitaxel, respectively. Thus, these findings demonstrate a new mechanism of drug-resistance acquisition via MVs.

Glioblastoma extracellular vesicles: reservoirs of potential biomarkers

Glioblastoma multiforme (GBM) is the most frequent and most devastating of the primary central nervous system tumors, with few patients living beyond 2 years postdiagnosis. The damage caused by the disease and our treatments for the patients often leave them physically and cognitively debilitated. Generally, GBMs appear after very short clinical histories and are discovered by imaging (using magnetic resonance imaging [MRI]), and the diagnosis is validated by pathology, following surgical resection. The treatment response and diagnosis of tumor recurrence are also tracked by MRI, but there are numerous problems encountered with these monitoring modalities, such as ambiguous interpretation and forms of pseudoprogression. Diagnostic, prognostic, and predictive biomarkers would be an immense boon in following treatment schemes and in determining recurrence, which often requires an invasive intracranial biopsy to verify imaging data. Extracellular vesicles (EVs) are stable, membrane-enclosed, virus-sized particles released from either the cell surface or from endosomal pathways that lead to the systemic release of EVs into accessible biofluids, such as serum/plasma, urine, cerebrospinal fluid, and saliva. EVs carry a wide variety of proteins, nucleic acids, lipids, and other metabolites, with many common features but with enough individuality to be able to identify the cell of origin of the vesicles. These components, if properly interrogated, could allow for the identification of tumor-derived EVs in biofluids, indicating tumor progression, relapse, or treatment failure. That knowledge would allow clinicians to continue with treatment regimens that were actually effective or to change course if the therapies were failing. Here, we review the features of GBM EVs, in terms of EV content and activities that may lead to the use of EVs as serially accessible biomarkers for diagnosis and treatment response in neuro-oncology.

Microparticles mediated cross-talk between tumoral and endothelial cells promote the constitution of a pro-metastatic vascular niche through Arf6 up regulation

The tumor stroma plays an essential role in tumor growth, resistance to therapy and occurrence of metastatic phenotype. Tumor vessels have been considered as passive conducts for nutrients but several studies have demonstrated secretion of pro-tumoral factors by endothelial cells. The failure of anti-angiogenic therapies to meet expectations raised by pre-clinical studies prompt us to better study the cross-talk between endothelial and cancer cells. Here, we hypothesized that tumor cells and the endothelium secrete bio-active microparticles (MPs) participating to a functional cross-talk. We characterized the cancer cells MPs, using breast and ovarian cancer cell lines (MCF7, MDA-MB231, SKOV3, OVCAR3 and a primary cell lines, APOCC). Our data show that MPs from mesenchymal-like cell lines (MDA-MB231, SKOV3 and APOCC) were able to promote an activation of endothelial cells through Akt phosphorylation, compared to MPs from epithelial-like cell lines (OVCAR3 and MCF7). The MPs from mesenchymal-like cells contained increased angiogenic molecules including PDGF, IL8 and angiogenin. The endothelial activation was associated to increased Arf6 expression and MPs secretion. Endothelial activation functionalized an MP dependent pro-tumoral vascular niche promoting cancer cells proliferation, invasiveness, stem cell phenotype and chemoresistance. MPs from cancer and endothelial cells displayed phenotypic heterogeneity, and participated to a functional cross-talk where endothelial activation by cancer MPs resulted in increased secretion of EC-MPs sustaining tumor cells. Such cross-talk may play a role in perfusion independent role of the endothelium.