Methods of isolating extracellular vesicles impact down-stream analyses of their cargoes.

Viable tumor cells actively release vesicles into the peripheral circulation and other biologic fluids, which exhibit proteins and RNAs characteristic of that cell. Our group demonstrated the presence of these extracellular vesicles of tumor origin within the peripheral circulation of cancer patients and proposed their utility for diagnosing the presence of tumors and monitoring their response to therapy in the 1970s. However, it has only been in the past 10 years that these vesicles have garnered interest based on the recognition that they serve as essential vehicles for intercellular communication, are key determinants of the immunosuppressive microenvironment observed in cancer and provide stability to tumor-derived components that can serve as diagnostic biomarkers. To date, the clinical utility of extracellular vesicles has been hampered by issues with nomenclature and methods of isolation. The term "exosomes" was introduced in 1981 to denote any nanometer-sized vesicles released outside the cell and to differentiate them from intracellular vesicles. Based on this original definition, we use "exosomes" as synonymous with "extracellular vesicles." While our original studies used ultracentrifugation to isolate these vesicles, we immediately became aware of the significant impact of the isolation method on the number, type, content and integrity of the vesicles isolated. In this review, we discuss and compare the most commonly utilized methods for purifying exosomes for post-isolation analyses. The exosomes derived from these approaches have been assessed for quantity and quality of specific RNA populations and specific marker proteins. These results suggest that, while each method purifies exosomal material, there are pros and cons of each and there are critical issues linked with centrifugation-based methods, including co-isolation of non-exosomal materials, damage to the vesicle's membrane structure and non-standardized parameters leading to qualitative and quantitative variability. The down-stream analyses of these resulting varying exosomes can yield misleading results and conclusions.

Nanoparticle analysis of circulating cell-derived vesicles in ovarian cancer patients.

Cell-derived vesicles are recognized as essential components of intercellular communication, and many disease processes are associated with their aberrant composition and release. Circulating tumor-derived vesicles have major potential as biomarkers; however, the diagnostic use of exosomes is limited by the technology available for their objective characterization and measurement. In this study, we compare nanoparticle tracking analysis (NTA) with submicron particle analysis (SPA), dynamic light scattering (DLS), and electron microscopy (EM) to objectively define size distribution, number, and phenotype of circulating cell-derived vesicles from ovarian cancer patients. Using the NanoSight LM10 instrument, cell-derived vesicles were visualized by laser light scattering and analyzing Brownian motion of these vesicles captured by video. The NTA software calculates the size and total concentration of the vesicles in solution. Using vesicles isolated from ovarian cancer patients, we demonstrate that NTA can measure the size distributions of cell-derived vesicles comparable to other analysis instrumentation. Size determinations by NTA, SPA, and DLS were more objective and complete than that obtained with the commonly used EM approach. NTA can also define the total vesicle concentration. Furthermore, the use of fluorescent-labeled antibodies against specific markers with NTA allows the determination of the "phenotype" of the cell-derived vesicles.

Morphologic and proteomic characterization of exosomes released by cultured extravillous trophoblast cells.

Exosomes represent an important intercellular communication vehicle, mediating events essential for the decidual microenvironment. While we have demonstrated exosome induction of pro-inflammatory cytokines, to date, no extensive characterization of trophoblast-derived exosomes has been provided. Our objective was to provide a morphologic and proteomic characterization of these exosomes. Exosomes were isolated from the conditioned media of Swan71 human trophoblast cells by ultrafiltration and ultracentrifugation. These were analyzed for density (sucrose density gradient centrifugation), morphology (electron microscopy), size (dynamic light scattering) and protein composition (Ion Trap mass spectrometry and western immunoblotting). Based on density gradient centrifugation, microvesicles from Sw71 cells exhibit a density between 1.134 and 1.173g/ml. Electron microscopy demonstrated that microvesicles from Sw71 cells exhibit the characteristic cup-shaped morphology of exosomes. Dynamic light scattering showed a bell-shaped curve, indicating a homogeneous population with a mean size of 165nm ± 0.5nm. Ion Trap mass spectrometry demonstrated the presence of exosome marker proteins (including CD81, Alix, cytoskeleton related proteins, and Rab family). The MS results were confirmed by western immunoblotting. Based on morphology, density, size and protein composition, we defined the release of exosomes from extravillous trophoblast cells and provide their first extensive characterization. This characterization is essential in furthering our understanding of "normal" early pregnancy.

TLR2-mediated expansion of MDSCs is dependent on the source of tumor exosomes.

Exosomes released from tumor cells having been shown to induce interleukin-6 release from myeloid-derived suppressor cells in a Toll-like receptor 2/Stat3-dependent manner. In this study, we show that exosomes released from tumor cells re-isolated from syngeneic mice are capable of inducing interleukin-6 in a Toll-like receptor 2-independent manner, whereas the data generated from exosomes of tumor cells having undergone numerous in vitro passages induce interleukin-6 in a Toll-like receptor 2-dependent manner. This discrepancy may be due to the source of tumor cells used to generate the exosomes for this study. These results suggest that exosomes released from tumor cells that are not within a tumor microenvironment may not realistically represent the role of tumor exosomes in vivo. This is an important consideration since frequently passing tumor cells in vivo is an accepted practice for studying tumor exosome-mediated inflammatory responses.

Nucleophosmin is recognized by a cytotoxic T cell line derived from a rectal carcinoma patient.

Immunotherapy of colorectal carcinoma (CRC) has great promise as the presence of T lymphocytes in CRC tissues in situ is correlated with reduced recurrence and increased survival. Thus, identification of the antigens recognized by T cells of CRC patients may permit development of vaccines with potential benefit for these patients. Using expression cloning, we identified the antigen, nucleophosmin (Npm), recognized by an HLA-A1 restricted cytotoxic T lymphocyte (CTL) line derived from the peripheral blood mononuclear cells (PBMC) of a rectal cancer patient. A decamer peptide derived from the Npm sequence sensitized peptide-pulsed HLA-A1 positive cells to lysis by the CTL line. The peptide also induced proliferative and cytotoxic T lymphocytes in the PBMC of 4 of 6 CRC patients, which lysed HLA-A1 positive peptide-pulsed target cells and CRC cells endogenously expressing Npm. Overexpression of Npm by tumors of various histological types, recognition of the antigen by T cells derived from different CRC patients and association of the antigen with poor prognostic outcome make it a promising target for immunotherapeutic intervention in cancer patients.

Characterization of humoral responses of ovarian cancer patients: antibody subclasses and antigenic components.

OBJECTIVES: Current antigen-based diagnostic assays for ovarian cancers rely on intravasation of specific aberrantly expressed proteins and their achieving detectable steady-state concentrations, resulting in their inability to truly detect small early lesions. In contrast, tumor antigen immunorecognition is observed following initial transformation events. Our objective was to characterize humoral antitumor responses in terms of IgG subclasses generated and tumor antigens recognized. METHODS: For patients with benign and malignant ovarian disease, tumor-reactive IgG subclasses were characterized by Western immunoblotting. Antigen recognition patterns were analyzed by 2-dimensional electrophoresis and proteins exhibiting shared or stage-specific recognition were defined by mass spectrometry (MS) sequencing. RESULTS: Sera from ovarian cancer patients exhibited significantly greater immunoreactivities than either controls or women with benign disease. While late-stage patients recognized more proteins at greater intensity, stage-specific differential recognition patterns were observed in the IgG subclasses, with the greatest recognition appearing in IgG2 subclasses. Immunoreactivity in IgG2 and IgG3 from stage I and II patients appears to be most intense with nuclear antigens >40 kDa, while, in stage III patients, additional immunoreactivity was present in the <40 kDa components. Stage III patients also exhibited similar reaction with membrane antigens <40 kDa. Two-dimensional electrophoresis revealed 32 stage-linked antigenic differences with 11 in early-stage and 21 in late-stage ovarian cancer. CONCLUSIONS: Owing to the timing and stability of humoral responses, quantitation of IgG subclasses recognizing specific tumor antigens provides superior biomarkers for early cancer identification and allows for differentiation of benign versus malignant ovarian masses and early- and late-stage cancers.

Patient-derived tumor-reactive antibodies as diagnostic markers for ovarian cancer.

OBJECTIVE: Most ovarian cancers are diagnosed at advanced stage (67%) and prospects for significant improvement in survival reside in early diagnosis. Our objective was to validate our array assay for the identification of ovarian cancer based on quantitation of tumor-reactive IgG. METHODS: The diagnostic array utilizes specific exosome-derived antigens to detect reactive IgG in patients' sera. Specific protein targets were isolated by immunoaffinity from exosomes derived from ovarian tumor cell lines. Sera were obtained from age-matched female volunteers, women with benign ovarian disease and with ovarian cancer. Immunoreactivity was also compared between exosomal proteins and their recombinant counterparts. RESULTS: Sera from ovarian cancer patients exhibited significantly greater immunoreactivities than either normal controls or women with benign disease (both considered negative to all antigens tested). Reactivities with nucleophosmin, cathepsin D, p53, and SSX common antigen for patients with all stages of ovarian cancer were significantly higher than for controls and women with benign ovarian disease. Reactivity with placental type alkaline phosphatase, TAG 72, survivin, NY-ESO-1, GRP78, and Muc16 (CA125) allowed the differentiation between Stage III/IV and early stage ovarian cancer. CONCLUSIONS: The quantitation of circulating tumor-reactive IgG can be used to identify the presence of ovarian cancer. The analyses of IgG recognition of specific exosomal antigens allows for the differentiation of women with benign ovarian masses from ovarian cancer, as well as distinguishing early and late stage ovarian cancers. Thus, the quantitative assessment of IgG reactive with specific tumor-derived exosomal proteins can be used as diagnostic markers for ovarian cancer.

Exosomal microRNA: a diagnostic marker for lung cancer.

PURPOSE: To date, there is no screening test for lung cancer shown to affect overall mortality. MicroRNAs (miRNAs) are a class of small noncoding RNA genes found to be abnormally expressed in several types of cancer, suggesting a role in the pathogenesis of human cancer. PATIENTS AND METHODS: We evaluated the circulating levels of tumor exosomes, exosomal small RNA, and specific exosomal miRNAs in patients with and without lung adenocarcinoma, correlating the levels with the American Joint Committee on Cancer (AJCC) disease stage to validate it as an acceptable marker for diagnosis and prognosis in patients with adenocarcinoma of the lung. RESULTS: To date, 27 patients with lung adenocarcinoma AJCC stages I-IV and 9 controls, all aged 21-80 years, were enrolled in the study. Small RNA was detected in the circulating exosomes. The mean exosome concentration was 2.85 mg/mL (95% CI, 1.94-3.76) for the lung adenocarcinoma group versus 0.77 mg/mL (95% CI, 0.68-0.86) for the control group (P < .001). The mean miRNA concentration was 158.6 ng/mL (95% CI, 145.7-171.5) for the lung adenocarcinoma group versus 68.1 ng/mL (95% CI, 57.2-78.9) for the control group (P < .001). Comparisons between peripheral circulation miRNA-derived exosomes and miRNA-derived tumors indicated that the miRNA signatures were not significantly different. CONCLUSION: The significant difference in total exosome and miRNA levels between lung cancer patients and controls, and the similarity between the circulating exosomal miRNA and the tumor-derived miRNA patterns, suggest that circulating exosomal miRNA might be useful as a screening test for lung adenocarcinoma. No correlation between the exosomal miRNA levels and the stage of disease can be made at this point.

Alterations of T cell activation signalling and cytokine production by postmenopausal estrogen levels.

BACKGROUND: Immunosenescence is an age-associated disorder occurring primarily in T cell compartments, including altered subset composition, functions, and activation. In women, evidence implicates diminished estrogen in the postmenopausal period as a contributing factor to diminished T cell responsiveness. Since hypoestrogenism is present in postmenopausal women, our objective focused on whether T cell activation, defined as signalling molecule expressions and activation, and function, identified as IL-2 production, were affected by low estrogen. METHODS: Using Jurkat 6.1 T cells, consequences of 4 pg/ml (corresponding to postmenopausal levels) or 40 pg/ml (premenopausal levels) of estradiol (E(2)) were analyzed on signalling proteins, CD3-zeta, JAK2, and JAK3, determined by Western immunoblotting. These consequences were correlated with corresponding gene expressions, quantified by real time-polymerase chain reaction. Tyrosine phosphorylation of CD3-zeta was defined by immunoprecipitation and western immunoblotting following activation by T cell receptor (TcR) cross-linking. CD3-zeta expression and modulation was also confirmed in T cells from pre- and postmenopausal women. To assess functional consequences, IL-2 production, induced by PMA and ionomycin, was determined using enzyme-linked immunosorbent spot assay (ELISpot). RESULTS: At 40 pg/ml E(2), the level of signalling protein CD3-zeta was elevated 1.57-fold, compared with cells exposed to 4 pg/ml E(2). The CD3-zeta proteins also exhibited altered levels of activation-induced phosphorylation in the presence of 40 pg/ml E(2) versus 4 pg/ml: 23 kD phosphorylated form increased 2.64-fold and the 21 kD form was elevated 2.95-fold. Examination of kinases associated with activation signalling also demonstrated that, in the presence of 40 pg/ml E(2), JAK2 protein expression was increased 1.64-fold (p < 0.001) and JAK3 enhanced 1.79-fold (p < 0.001) compared to 4 pg/ml. mRNA levels for CD3-zeta, JAK2, and JAK3 were significantly increased following exposure to 40 pg/ml E(2) (2.39, 2.01, and 2.21 fold, respectively) versus 4 pg/ml. These findings were confirmed in vivo, since T cells from postmenopausal women exhibited 7.2-fold diminished CD3-zeta expression, compared to pre-menopausal controls and this expression was elevated 3.8-fold by addition of 40 pg/ml E(2). Functionally, Jurkat cells exposed to 40 pg/ml E(2) and activated exhibited significantly elevated numbers of IL-2 producing colonies compared to 4 pg/ml (75.3 +/- 2.2 versus 55.7 +/- 2.1 colonies, p < 0.0001). CONCLUSION: Jurkat T cells exposed to 4 pg/ml E(2) expressed significantly diminished activation signalling proteins, correlating with reduced IL-2 production. Lower signalling protein levels appear to result from decreased CD3-zeta, JAK2, and JAK3 gene expressions. These findings may provide a molecular basis for immunosenescence associated with the postmenopausal state.

Gene expression profiling in response to estradiol and genistein in ovarian cancer cells.

BACKGROUND: Despite optimal primary treatment of ovarian cancer, overall prognosis is poor due to recurrences. While steroid hormone receptors are frequently expressed, the role of estrogen receptor (ER) in ovarian carcinogenesis, response to treatment or prognosis has not been established. We analyzed the gene-expression in response to estradiol (E2) and genistein (Gen) in ovarian cancer cells. MATERIALS AND METHODS: Cell lines (Br-1, UL-1; Oy-1), treated with E2 (10 nM) or Gen (5 microM), were used for gene expression profiling. RT-PCR and Western immunoblotting were used to further analyze gene expression data. RESULTS: Twenty-four genes were differentially regulated in ovarian cancer cell lines. C3, CLU, COL6A1, DLC1, NME1, NRIP1, PTEN, RAC2, S100A2 were down-regulated with E2 in Br-1 and UL-1 cells. MK167, SERPINB5, SLC7A5, CDK1NA, LCN2, PLAU, PHB2, CTSB, EGLN2, ERBB2, HMGB1, ID2, ITGB4, TOP2A were up-regulated in Oy-1 cells with E2 and/or genistein. ERBB2 and ID2 (E2 and Gen), LCN2, PHB2 and HMGB1 (Gen) were down-regulated in Br-1 cells. ERalpha and ERbeta were detected in all cell lines at different levels. CONCLUSION: Variable response of ovarian cancer cells to E2 and Gen was observed. Study of ERs including splice variants, co-regulatory molecules are necessary to understand the relevance of receptors.

MicroRNA signatures of tumor-derived exosomes as diagnostic biomarkers of ovarian cancer.

OBJECTIVES: Most ovarian cancer patients are diagnosed at an advanced stage (67%) and prospects for significant improvement in survival reside in early diagnosis. While expression patterns of a recently identified biomarker family, microRNA, appear to be characteristic of tumor type and developmental origin, microRNA profiling has been limited to tissue specimens. Tumors actively release exosomes into the peripheral circulation and we now demonstrate the association of microRNAs with circulating tumor-derived exosomes. METHODS: Circulating tumor exosomes were isolated using a modified MACS procedure with anti-EpCAM. Initially, microRNA profiles of ovarian tumors were compared to those of tumor exosomes isolated from the same patients. Levels of 8 microRNAs (miR-21, miR-141, miR-200a, miR-200c, miR-200b, miR-203, miR-205 and miR-214) previously demonstrated as diagnostic, were compared in exosomes isolated from sera specimens of women with benign disease and various stages of ovarian cancer. RESULTS: MicroRNA from ovarian tumor cells and exosomes from the same patients were positive for 218 of 467 mature microRNAs analyzed. The levels of the 8 specific microRNAs were similar between cellular and exosomal microRNAs (exhibiting correlations from 0.71 to 0.90). While EpCAM-positive exosomes were detectable in both patients with benign ovarian disease and ovarian cancer, exosomal microRNA from ovarian cancer patients exhibited similar profiles, which were significantly distinct from profiles observed in benign disease. Exosomal microRNA could not be detected in normal controls. CONCLUSIONS: These results suggest that microRNA profiling of circulating tumor exosomes could potentially be used as surrogate diagnostic markers for biopsy profiling, extending its utility to screening asymptomatic populations.

Application of Bayesian modeling of autologous antibody responses against ovarian tumor-associated antigens to cancer detection.

Biomarkers for early detection of epithelial ovarian cancer (EOC) are urgently needed. Patients can generate antibodies to tumor-associated antigens (TAAs). We tested multiplex detection of antibodies to candidate ovarian TAAs and statistical modeling for discrimination of sera of EOC patients and controls. Binding of serum antibody of women with EOC or healthy controls to candidate TAA-coated microspheres was assayed in parallel. A Bayesian model/variable selection approach using Markov Chain Monte Carlo computations was applied to these data, and serum CA125 values, to determine the best predictive model. The selected model was subjected to area under the receiver-operator curve (AUC) analysis. The best model generated an AUC of 0.86 [95% confidence interval (95% CI), 0.78-0.90] for discrimination between sera of EOC patients and healthy patients using antibody specific to p53, NY-CO-8, and HOXB7. Inclusion of CA125 in the model provided an AUC of 0.89 (95% CI, 0.84-0.92) compared with an AUC of 0.83 (95% CI, 0.81-0.85) using CA125 alone. However, using TAA responses alone, the model discriminated between independent sera of women with nonmalignant gynecologic conditions and those with advanced-stage or early-stage EOC with AUCs of 0.71 (95% CI, 0.67-0.76) and 0.70 (95% CI, 0.48-0.75), respectively. Serum antibody to p53 and HOXB7 is positively associated with EOC, whereas NY-CO-8-specific antibody shows negative association. Bayesian modeling of these TAA-specific serum antibody responses exhibits similar discrimination of patients with early-stage and advanced-stage EOC from women with nonmalignant gynecologic conditions and may be complementary to CA125.

Pregnancy-linked suppression of TcR signaling pathways by a circulating factor absent in recurrent spontaneous pregnancy loss (RPL).

Evidence suggests that maternal cell-mediated immunity is suppressed during pregnancy and that failure to suppress immune responses can result in partial or total rejection of the fetus. The molecular events associated with suppression of maternal T-cell activation mediated by circulating pregnancy-associated 14 kDa zeta inhibitor protein (ZIP) were defined in women with and without histories of recurrent pregnancy loss (RPL). Using cDNA microarray analysis, ZIP modulations of specific genes associated with T-cell activation signaling were defined. Alterations of defined components were confirmed at the protein level using chromatographically purified ZIP from normal pregnancies versus analogous material from women experiencing RPL. Based on microarray analyses, ZIP from normal pregnancies induced an increase (> or =2-fold) in the expression of 19 genes and a decrease (> or =2-fold) in 15 genes, when incubated with cultured T-cells. In contrast, when T-cells were incubated with analogous material from RPL or non-pregnant controls, no significant differences were observed in the expression of these genes. At the protein level, ZIP from normal pregnancies induced decreases in CD3-zeta (2.36-fold), JAK3 (2.41-fold), STAT5 (1.85-fold), and NF-kappaB (4.24-fold) and a 2.05-fold increase in SOCS2 (all at p<0.001 compared to RPL and non-pregnant controls). The suppressive effects of Zip can lead to the failure of T-cell production of Th1 cytokines, such as IL-2. The 14 kDa circulating ZIP from normal pregnancies suppressed components within the JAK/STAT pathway and induced suppressors of cytokine stimulation, SOCS2.

Primary tumor cells resected from cancer patients and decorated with a novel form of CD80 protein serve as effective antigen-presenting cells for the induction of autologous T cell immune responses ex vivo.

Vaccination with autologous tumor cells genetically modified to express costimulatory molecules has shown utility for cancer immunotherapy in preclinical and limited clinical settings. Given the complicated nature of gene therapy, a practical alternative approach has been designed that relies on modification of the cell membrane with biotin and its "decoration" with a chimeric protein composed of the functional portion of human CD80 and core streptavidin (CD80-SA). We tested whether primary tumor cells resected from cancer patients can be decorated with CD80-SA and whether such cells serve as antigen-presenting cells (APCs) to generate autologous T cell responses ex vivo. Tumors and peripheral blood lymphocytes (PBLs) were collected from 14 lung, 9 colon, and 2 breast "treatment-naive" cancer patients presenting various clinical stages of the disease. Tumors were mechanically processed, irradiated, decorated with CD80-SA or control streptavidin (SA) protein, and used as APCs in ex vivo autologous T cell-proliferative and cytotoxicity assays. All tumor samples were modified with CD80-SA, albeit with various degrees of decoration ranging from 21.8 to 100%. CD80- SA-decorated cells generated significant proliferative responses in autologous T cells from 9 of 16 evaluable patients (p < 0.05). Proliferative responses were CD80-SA specific and heterogeneous, with stimulation indices ranging from 0.25 to 45. In 15 of 15 evaluable patients, CD80-SA-specific cytotoxic T cell responses against autologous tumors were generated, 11 of which were significant, with specific killing ranging from 5 to 70%. Taken together, these data demonstrate that primary tumor cells can be effectively decorated with CD80-SA and that such cells serve as APCs to induce autologous antitumor T cell responses.

Induction of p53 and drug resistance following treatment with cisplatin or paclitaxel in ovarian cancer cell lines.

Treatment failures result from resistance to chemotherapy in ovarian cancer. The effect of cisplatin and paclitaxel treatments on chemosensitivity was studied in ovarian cancer cells developed from a patient with stage IIIC disease. Cells (UL-3A, UL-3B) that recovered from cisplatin (Cis) and paclitaxel (Tax) treatments showed higher levels of p53, mdr-1 and chemoresistance than untreated controls. EC50 values of Cis and Tax for UL-3A clones were 7.2-34.6, average 20.9 microg/ml, while UL-3B clones ranged from 11.8-252.0 microg/ml, with a mean value of 73.2 microg/ml for Cis, and 260.0-4400.0 nM (mean 2555.0 nM) for Tax. Selection pressures during treatment may contribute to drug resistance.