Ovarian cancer remains the most lethal type of cancer among all gynecological malignancies. The majority of patients are diagnosed with ovarian cancer at the late stages of the disease. Therefore, there exists an imperative need for the development of early ovarian cancer diagnostic techniques. Exosomes, secreted by various cell types, play pivotal roles in intercellular communication, which emerge as promising diagnostic and prognostic biomarkers for ovarian cancer. In this study, we present for the first time, at least to the best of our knowledge, the proteomics profiling of exosomes derived from the plasma of patients with ovarian cancer via liquid chromatography tandem mass spectrometry (LC‑MS/MS) with tandem mass tagging (TMT). The exosomes enriched from patient plasma samples were characterized by nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), transmission electron microscopy (TEM) and western blot analysis. The size of the plasma exosomes fell into the range of 30 to 100 nm in diameter. The exosomal marker proteins, CD81 and TSG101, were clearly stained in the exosome samples; however, there was no staining for the endoplasmic reticulum protein, calnexin. A total of 294 proteins were identified with all exosome samples. Among these, 225 proteins were detected in both the cancerous and non‑cancerous samples. Apart from universal exosomal proteins, exosomes derived from ovarian cancer patient plasma also contained tumor‑specific proteins relevant to tumorigenesis and metastasis, particularly in epithelial ovarian carcinoma (EOC). Patients with EOC often suffer from coagulation dysfunction. The function of exosomes in coagulation was also examined. Several genes relevant to the coagulation cascade were screened out as promising diagnostic and prognostic factors that may play important roles in ovarian cancer progression and metastasis. On the whole, in this study, we successfully isolated and purified exosomes from plasma of patients with EOC, and identified a potential role of these exosomes in the coagulation cascade, as well as in the diagnosis and prognosis of patients.

Objective: The tumor susceptibility gene 101 (TSG101) is closely associated with various tumor types, but its role in the pathogenesis of renal cell carcinoma (RCC) is still unknown. This study used RNA interference to silence the expression of TSG101 in RCC cell lines and explore the role of TSG101 in RCC.
Methods: Immunohistochemistry and western blot were performed to detect the expression of TSG101 in 15 paired renal tumor samples. A small interfering RNA (siRNA) targeting TSG101 was transfected into A498 and 786-O cell lines. The Cell Counting Kit-8 (CCK-8) assay and colony formation assay were used to observe the changes in cell proliferation after transfection. Flow cytometry was used to detect the effect on the cell cycle. Western blot was conducted to study the changes of related functional proteins.
Results: The expression of TSG101 was higher in RCC tissues than in adjacent normal tissues. The CCK-8 assay showed that the proliferation and colony formation of the A498 and 786-O cell lines were attenuated after suppression of TSG101. Flow cytometry showed that silencing of TSG101 induced G0/G1 arrest. The western blot results revealed that the levels of cell cycle-related proteins (c-myc, cyclin E1 and cyclin-dependent kinase 2 (CDK2)) were markedly decreased in the siRNA groups.
Conclusions: TSG101 promotes proliferation of RCC cells. This positive effect on tumor growth involves activation of c-myc and cyclin E1/CDK2 and their effect on cell cycle distribution.

BACKGROUND/AIM: Resistance to anoikis is a pre-requisite step in metastasis, a major cause of death in patients with cancer, including thyroid cancer. Impairing anoikis resistance is a possible strategy for therapy of metastatic cancer. We, therefore, we aimed to investigate the key players of anoikis resistance.
MATERIALS AND METHODS: Papillary-type (BCPAP), follicular-type (FTC133), and anaplastic-type (ARO) thyroid carcinoma cells, cultured in poly(2-hydroxyethyl methacrylate)-coated plates to mimic circulating cells, were used as model systems in this study. Flow cytometry and soft-agar assays were used to determine cells exhibiting anoikis resistance. Proteomics was used to identify candidate proteins and validated using western blot and siRNA knockdown.
RESULTS: Only ARO cells showed both anoikis resistance potential and anchorage-independent growth ability. Tumor susceptibility gene 101 protein (TSG101) was identified to be potentially important in anoikis resistance, which was confirmed by an increase in anoikis and expression of a pro-apoptotic protein (BCL-2 like protein 4) and an apoptotic marker (cleaved poly-ADP ribose polymerase) in floating siTSG101-knockdown cells.
CONCLUSION: To our knowledge, this is the first study that implicates the importance of TSG101 in anoikis resistance of thyroid cancer.

BACKGROUND: Exosomes are small vesicles containing a wide range of functional proteins, mRNA and miRNA. Exosomal miRNAs from cancer cells play crucial roles in mediating cell-cell communication and tumor-microenvironment cross talk, specifically in enabling metastasis and promoting angiogenesis. We focused on miR-9 that was identified as a tumor suppressor previously in nasopharyngeal carcinoma (NPC) tumorigenesis.
METHODS: Differential centrifugation, transmission electron microscopy and nanoparticle tracking analysis were used to isolate and identify exosomes. Quantitative PCR and western blotting analysis were used to detect miR-9, pri-miR-9, CD63, TSG101, MDK, P70S6K P-Ser424 and PDK1 P-Ser241 expression. Laser confocal microscopy was used to trace exosomal miR-9 secreted by NPC cells into HUVECs. The effect of exosomal miR-9 on cell migration and tube formation of HUVECs in vivo and vitro was assessed by using migration assay, tube formation assay and matrigel plug assay, respectively. Bioinformatics analysis and luciferase reporter assay were utilized to confirm the binding of exosomal miR-9 to the 3'untranslated region (3'-UTR) of MDK, while Phosphorylation Array was performed to identify AKT Pathway in HUVECs treated with exosomal miR-9. Furthermore, Immunohistochemistry (IHC) and in situ hybridization (ISH) was used to detected miR-9, CD31 and MDK expression in human NPC tumor samples.
RESULTS: NPC cells transfected with miR-9-overexpressing lentivirus, released miR-9 in exosomes. Exosomal miR-9 directly suppressed its target gene - MDK in endothelial cells. Mechanistic analyses revealed that exosomal miR-9 from NPC cells inhibited endothelial tube formation and migration by targeting MDK and regulating PDK/AKT signaling pathway. Additionally, the level of MDK was upregulated in NPC tumor samples and was positively correlated with microvessel density. Notably, the level of exosomal miR-9 was positively correlated with overall survival, and MDK overexpression was positively associated with poor prognosis in NPC patients, suggesting the clinical relevance and prognostic value of exosomal miR-9 and MDK.
CONCLUSIONS: Taken together, our data identify an extracellular anti-angiogenic role for tumor-derived, exosome-associated miR-9 in NPC tumorigenesis and prompt further investigation into exosome-based therapies for cancer treatment.

The androgen receptor (AR) signaling pathway plays a vital role in the normal development and function of the male reproductive organs. Dysregulation of the androgen-AR signaling pathway has been linked to prostate cancer. Here, we demonstrate that tumor susceptibility gene 101 (TSG101) regulates AR expression level via the endosome/lysosome degradation pathway. In LNCaP cells, TSG101 overexpression recruits the AR to TSG101-containing cytoplasmic vesicles resulting in reduced AR protein level and AR transactivation activity downregulation. Immunofluorescence microscopy demonstrated that TSG101-decorated cytoplasmic vesicles are associated with late endosomes/lysosomes and the AR could be found within the Lamp2 positive TSG101 vesicles upon lysosomal protease inhibitor treatment. Furthermore, chloroquine or bafilomycin A1 treatment was able to restore TSG101-mediated AR expression reduction. Based on these data, we conclude that the interaction of the AR and TSG101 leads to AR recruitment to TSG101-containing cytoplasmic vesicles and induces AR-attenuated expression through the late endosome/lysosome degradation pathway.

Anthracycline/taxane-based chemotherapy regimens are usually used as neoadjuvant chemotherapies to decrease tumour size and prevent metastasis of advanced breast cancer. However, patients have a high risk of developing chemo-resistance during treatment through still unknown mechanisms. Glutathione S-transferase P1 (GSTP1), which belongs to the family of phase II metabolic enzymes, has been reported to function in detoxifying several anti-cancer drugs by conjugating them with glutathione. Previous studies have identified GSTP1 as a predictor of prognosis and chemo-resistance in breast cancer patients, but the mechanisms governing GSTP1-dependent drug resistance are still unclear. We have found that GSTP1 expression is much higher in adriamycin-resistant cells and their corresponding exosomes. The role of GSTP1-containing exosomes in conferring drug resistance was analysed through cell apoptosis and immunofluorescence staining assays. Furthermore, we analysed 42 cases of paired breast cancer tissues collected before and after anthracycline/taxane-based neoadjuvant chemotherapy by immunohistochemistry. Higher GSTP1 expression was shown in the progressive disease (PD)/stable disease (SD) group than in the partial response (PR)/complete response (CR) group both in the samples collected before and after the chemotherapy treatment. Interestingly, GSTP1 partly re-localized from the cell nucleus to the cytoplasm upon treatment, and similar results were obtained for the exosomal marker Tumour susceptibility gene 101 protein (TSG101), which also increased in the cytoplasm after chemotherapy. After analysing the serum exosomes of 30 patients treated with anthracycline/taxane-based neoadjuvant chemotherapy, we discovered that the levels of GSTP1 in exosomes from patients in the PD/SD group were significantly higher than those in the PR/CR group. Here, for the first time, we investigated a novel role for GSTP1-containing exosomes and their capability to transfer drug resistance and evaluated their clinical use in predicting chemo-resistance.

OBJECTIVE: Angiogenesis is a key event in the progression of gliomas, and emerging evidence suggests that exosomes are signaling extracellular organelles that modulate the tumor microenvironment and promote angiogenesis and tumor progression. This study aimed to explore the mechanism by which glioma-derived exosomes affect angiogenesis.
MATERIALS AND METHODS: qRT-PCR was used to determine the expression level of linc-POU3F3 in glioma tissue as well as glioma cell lines. Ultrafiltration combined with a purification method was used to isolate exosomes derived from A172 cells (A172-Exo) and linc-POU3F3 shRNA-treated A172 cells (shA172-Exo). Transmission electron microscopy, Western blot and tunable resistive pulse sensing (TRPS) were used to identify exosomes. In vitro migration, proliferation, and tube formation experiments, as well as in vivo CAM assays, were used to analyze the pro-angiogenesis ability of exosomes. qRT-PCR and Western blot were used to identify expression levels of angiogenesis-related genes and proteins in human brain microvascular endothelial cells (HBMECs) after being cultured with exosomes.
RESULTS: The levels of linc-POU3F3 were upregulated in glioma tissue and significantly correlated with the advanced tumor stage. A172 cells exhibited the highest expression level. A172-Exo was similar to shA172-Exo (50-100 nm in diameter) and expressed Alix, Tsg101 and CD9, while the expression level of linc-POU3F3 in A172-Exo was significantly higher than that in shA172-Exo. HBMECs rapidly internalized A172-Exo and shA172-Exo, and the linc-POU3F3 expression level in HBMECs treated with A172-Exo was significantly higher than the level in HBMECs treated with shA172-Exo. A172-Exo exhibited better function in promoting HBMECs migration, proliferation, tubular-like structure formation in vitro and arteriole formation in vivo. The gene and protein expression level of bFGF, bFGFR, VEGFA, and Angio in HBMECs treated with A172-Exo was much higher than that of HBMECs treated with shA172-Exo.
CONCLUSIONS: These results indicated that gliomas can induce angiogenesis by secreting exosomes enriched in linc-POU3F3. Exosomes and lncRNA-POU3F3 may, therefore, function as a putative therapeutic target in glioma.

Signals derived from the microenvironment contribute greatly to tumorigenesis . The underlying mechanism requires thorough investigation. Here, we use

BACKGROUND: Cancer-derived exosomes are involved in metastasis. YKT6 is a SNARE protein that participates in the regulation of exosome production and release, but its role in non-small cell lung cancer (NSCLC) has not been examined.
MATERIALS AND METHODS: Ultracentrifugation-purified exosomes from the A549 cell line were studied by CRYO-TEM, nanoparticle tracking analysis and western blot (TSG101 marker). YKT6 was inhibited using a DsiRNA and selected pre-microRNAs. MicroRNAs targeting YKT6 were validated by Renilla/Luciferase assay and western blot. YKT6 expression and its prognostic impact were analyzed in 98 tissue specimens from resected NSCLC patients.
RESULTS: Membranous nanosized vesicles (mode size: 128nm) with TSG101 protein were purified from A549 cells. YKT6 inhibition reduced exosome release by 80.9%. We validated miR-134 and miR-135b as miRNAs targeting YKT6, and transfection with the pre-miRNAs also produced a significant reduction in exosome release. The analysis of YKT6 in tumor samples showed that patients with high levels had shorter disease-free and overall survival.
CONCLUSIONS: YKT6 is a key molecule in the regulation of exosome release in lung cancer cells and is in turn precisely regulated by miR-134 and miR-135b. Moreover, YKT6 levels impact prognosis of resected NSCLC patients.

The discovery of alterations in the EGFR and ALK genes, amongst others, in NSCLC has driven the development of targeted-drug therapy using selective tyrosine kinase inhibitors (TKIs). To optimize the use of these TKIs, the discovery of new biomarkers for early detection and disease progression is mandatory. These plasma-isolated exosomes can be used as a non-invasive and repeatable way for the detection and follow-up of these biomarkers. One ml of plasma from 12 NSCLC patients, with different mutations and treatments (and 6 healthy donors as controls), were used as exosome sources. After RNAse treatment, in order to degrade circulating miRNAs, the exosomes were isolated with a commercial kit and resuspended in specific buffers for further analysis. The exosomes were characterized by western blotting for ALIX and TSG101 and by transmission electron microscopy (TEM) analysis, the standard techniques to obtain biochemical and dimensional data of these nanovesicles. Total RNA extraction was performed with a high yield commercial kit. Due to the limited miRNA-content in exosomes, we decided to perform retro-transcription PCR using an individual assay for each selected miRNA. A panel of miRNAs (30b, 30c, 103, 122, 195, 203, 221, 222), all correlated with NSCLC disease, were analyzed taking advantage of the remarkable sensitivity and specificity of Real-Time PCR analysis; mir-1228-3p was used as endogenous control and data were processed according to the formula 2(-) (ΔΔct) (13). Control values were used as baseline and results are shown in logarithmic scale.

Diagnostic strategies, particularly non-invasive blood-based screening approaches, are gaining increased attention for the early detection and attenuation of mortality associated with colorectal cancer (CRC). However, the majority of current screening approaches are inadequate at replacing the conventional CRC diagnostic procedures. Yet, due to technological advances and better understanding of molecular events underlying human cancer, a new category of biomarkers are on the horizon. Recent evidence indicates that cells release a distinct class of small vesicles called 'exosomes', which contain nucleic acids and proteins that reflect and typify host-cell molecular architecture. Intriguingly, exosomes released from cancer cells have a distinct genetic and epigenetic makeup, which allows them to undertake their tumorigenic function. From a clinical standpoint, these unique cancer-specific fingerprints present in exosomes appear to be detectable in a small amount of blood, making them very attractive substrates for developing cancer biomarkers, particularly noninvasive diagnostic approaches.

Tumor susceptibility gene 101 (TSG101) elicits an array of cellular functions, including promoting cytokinesis, cell cycle progression and proliferation, as well as facilitating endosomal trafficking and viral budding. TSG101 protein is highly and aberrantly expressed in various human cancers. Specifically, a TSG101 splicing variant missing nucleotides 154 to 1054 (TSGΔ154-1054), which is linked to progressive tumor-stage and metastasis, has puzzled investigators for more than a decade. TSG101-associated E3 ligase (Tal)- and MDM2-mediated proteasomal degradation are the two major routes for posttranslational regulation of the total amount of TSG101. We reveal that overabundance of TSG101 results from TSGΔ154-1054 stabilizing the TSG101 protein by competitively binding to Tal, but not MDM2, thereby perturbing the Tal interaction with TSG101 and impeding subsequent polyubiquitination and proteasomal degradation of TSG101. TSGΔ154-1054 therefore specifically enhances TSG101-stimulated cell proliferation, clonogenicity, and tumor growth in nude mice. This finding shows the functional significance of TSGΔ154-1054 in preventing the ubiquitin-proteasome proteolysis of TSG101, which increases tumor malignancy and hints at its potential as a therapeutic target in cancer treatment.

Tumor susceptibility gene 101 (TSG101) and activating transcription factor 2 (ATF2) have been suggested to involve in the reactivation of EBV which has implications in the development and progression of breast cancer. Therefore, the polymorphisms of TSG101 and ATF2 may associate with breast cancer risk and prognosis. A case-control study with 1551 breast cancer cases and 1605 age-matched controls were conducted in Guangzhou, China. We have also successfully followed up 1168 cases until December 31, 2014. The variant allele of TSG101 rs2292179 was associated with a non-significant reduced risk of breast cancer, particularly among women with BMI < 24 (kg/m(2)) (P for interaction <0.05). For ATF2 rs3845744, the variant allele was also associated with a significantly reduced breast cancer risk [odds ratio (OR) (95 % confidence interval (CI)) 0.86 (0.74∼1.00)], and the association occurred among only postmenopausal women [OR (95 % CI) 0.69 (0.54∼0.88)] (P for interaction <0.05). Breast cancer risk was further reduced with the increasing numbers of the variant G alleles of the two polymorphisms (P for trend <0.05). We did not find an overall association of the two loci with breast cancer prognosis, while the hazard ratios of the two loci (AG/GG vs. AA) were significantly higher among postmenopausal women than premenopausal women (P = 0.046, 0.016 for TSG101 rs2292179 and ATF2 rs3845744, respectively). In summary, the variant alleles of TSG101 rs2292179 and ATF2 rs3845744 were associated with a reduced risk of breast cancer, particularly for subjects with BMI <24 (kg/m(2)) and postmenopausal women, respectively. The two SNPs and menopausal status may have a significant interaction on breast cancer progression.

BACKGROUND: Tumor susceptibility gene 101 (TSG101) was initially identified in fibroblasts as a tumor suppressor gene but subsequent studies show that TSG101 also functions as a tumor-enhancing gene in some epithelial tumor cells. Although previous studies have unraveled diverse biological functions of TSG101, the precise mechanism by which TSG101 is involved in carcinogenesis and tumor progression in a bidirectional and multifaceted manner remains unclear.
METHODS: To reveal the mechanism underlying bidirectional modulation of cell invasion by TSG101, we used RNA interference to examine whether TSG101 depletion bidirectionally modulated matrix metalloproteinase (MMP)-9 expression in different cell types.
RESULTS: TSG101 depletion promoted cell invasion of HT1080 cells but contrarily reduced cell invasion of HeLaS3 cells. In HT1080 cells, TSG101 depletion increased both baseline and phorbol 12-myristate 13-acetate (PMA)-induced MMP-9 secretion through enhancing MMP-9 mRNA expression, but did not affect the expression or activation of MMP-2. In contrast, TSG101 depletion decreased PMA-induced MMP-9 secretion through reducing MMP-9 mRNA expression in HeLaS3 cells. TSG101 depletion had little impact on the signaling pathways required for the activation of transcription of MMP-9 or MMP-9 mRNA stability in either cell line.
CONCLUSION: TSG101 bidirectionally modulates cell invasion through regulating MMP-9 mRNA expression in different cell types. Our results provide a mechanistic context for the role of TSG101 in cell invasion as a multifaceted gene.

BACKGROUND: The tumor susceptibility gene 101 (TSG101) was originally identified as a tumor-suppressor gene that mediates many molecular and biological processes, such as ubiquitination, endosomal trafficking, cell survival, and virus budding, but its role in hepatocellular carcinoma (HCC) is currently unknown.
MATERIAL AND METHODS: We assessed the expression of TSG101 in HCC and paracancerous tissues using qPCR. Then, we used the TSG101-specific siRNA mix to disrupt the expression of TSG101 to investigate the subsequent effect on human hepatoma-7 (Huh7) cells. Western blot was used to detect the protein expression of TSG101 and other molecules. Cell growth assay was performed using CCK8. Transwell assay was used to investigate the migration and invasion ability of Huh7 cells after transfection with of TSG101 siRNA. Flow cytometry was used to estimate the effect of TSG101 knockdown on cell cycle and apoptosis. Confocal laser scanning microscopy was used to observe the actin filaments change and the formation of autophagy.
RESULTS: TSG101 was over-expressed in HCC tissues. TSG101 silence was able to suppress Huh7 cell proliferation, migration, and invasion. Furthermore, silencing of TSG101 could induce cell cycle arrest at G1 phase and inhibit the expression of cyclin A and cyclin D, while up-regulating the expression of CDK2. The mechanism might be induction of autophagic cell death and inactivation of Akt and ERK1/2.
CONCLUSIONS: TSG101 plays an important role in the development of HCC and may be a target for molecular therapy.

Oxaliplatin (L-OHP) is one of the most commonly used anticancer drugs in adjuvant treatment of colon cancer after complete resection of the primary tumor and treatment of metastatic colorectal cancer. Cancer cells eventually become resistant to L-OHP, which diminishes its curative effect. However, the mechanism of action of L-OHP remains unknown. In this study, an L-OHP-resistant human colon cancer cell line, HT29/L-OHP, was established by gradually increasing the dose of L-OHP in culture. The expression levels of the tumor susceptibility gene 101 (tsg101) and the TSG101 protein in HT29 and HT29/L-OHP cell lines were examined by reverse transcription-polymerase chain reaction and western blot analysis. In addition, the expression levels of several apoptosis-regulating protein markers were determined using immunohistochemistry-staining assays. We found that the expression of tsg101 mRNA and of TSG101 protein were significantly higher in the HT29/L-OHP cell line than in its parent, HT29 (P < 0.05). In addition, the expression of multiple apoptosis-regulating protein markers were significantly increased (P < 0.05) in the HT29/L-OHP cell line. These data suggest that these markers could be useful as predictive markers for evaluating and comparing the efficacy and molecular pharmacology of chemotherapeutics.

Cancer recognized as one of the leading irrepressible health issues is contributing to increasing mortality-rate day-by-day. The tumor microenvironment is an important field of cancer to understand the detection, treatment and prevention of cancer. Recently, cancer stem cell (CSC) research has shown promising results aiming towards cancer diagnostics and treatment. Here, we found that prostate and breast cancer stem cells secreted vesicles of endosomal origin, called exosomes showed strong connection between autophagy and exosomes released from CSCs. Exosomes may serve as vesicles to communicate with neoplastic cells (autocrine and paracrine manner) and normal cells (paracrine and endocrine manner) and thereby suppress immune systems and regulate neoplastic growth, and metastasis. They can also be used as biomarkers for various cancers. We detected tetraspanin proteins (CD9, CD63, CD81), Alix and tumor susceptibility gene-101 (TSG101) of exosomal markers from rotenone treated CSCs. We have also detected the induction of autophagy genes, Atg7 and conversion of autophagy marker (LC3-I to LC3-II), and tetraspanin proteins (CD9, CD63, CD81) in rotenone treated CSCs by western blotting. The mRNA expression of CD9, CD63, CD81 and TSG101 analyzed by qRT-PCR showed that the rotenone induced the expression of CD9, CD63, CD81 and TSG101 in CSCs. Electron microscopy of rotenone treated CSCs showed the mitochondrial damage of CSCs as confirmed by the release of exosomes from CSCs. The constituents of exosomes may be useful to understand the mechanism of exosomes formation, release and function, and also serve as a useful biomarker and provide novel therapeutic strategies for the treatment and prevention of cancer.

Mechanisms of unassisted delivery of RNA therapeutics, including inhibitors of microRNAs, remain poorly understood. We observed that the hepatocellular carcinoma cell line SKHEP1 retains productive free uptake of a miR-21 inhibitor (anti-miR-21). Uptake of anti-miR-21, but not a mismatch (MM) control, induces expression of known miR-21 targets (DDAH1, ANKRD46) and leads to dose-dependent inhibition of cell growth. To elucidate mechanisms of SKHEP1 sensitivity to anti-miR-21, we conducted an unbiased shRNA screen that revealed tumor susceptibility gene 101 (TSG101), a component of the endosomal sorting complex required for transport (ESCRT-I), as an important determinant of anti-proliferative effects of anti-miR-21. RNA interference-mediated knockdown of TSG101 and another ESCRT-I protein, VPS28, improved uptake of anti-miR-21 in parental SKHEP1 cells and restored productive uptake to SKHEP1 clones with acquired resistance to anti-miR-21. Depletion of ESCRT-I in several additional cancer cell lines with inherently poor uptake resulted in improved activity of anti-miR-21. Finally, knockdown of TSG101 increased uptake of anti-miR-21 by cancer cells in vivo following systemic delivery. Collectively, these data support an important role for the ESCRT-I complex in the regulation of productive free uptake of anti-miRs and reveal potential avenues for improving oligonucleotide free uptake by cancer cells.

Developing simple and effective approaches to detect tumor markers will be critical for early diagnosis or prognostic evaluation of prostate cancer treatment. Prostate‑specific membrane antigen (PSMA) has been validated as an important tumor marker for prostate cancer progression including angiogenesis and metastasis. As a type II membrane protein, PSMA can be constitutively internalized from the cell surface into endosomes. Early endosomes can fuse with multivesicular bodies (MVB) to form and secrete exosomes (40-100 nm) into the extracellular environment. Herein, we tested whether some of the endosomal PSMA could be transferred to exosomes as an extracellular resource for PSMA. Using PSMA-positive LNCaP cells, the secreted exosomes were collected and isolated from the cultured media. The vesicular structures of exosomes were identified by electron microscopy, and exosomal marker protein CD9 and tumor susceptibility gene (TSG 101) were confirmed by western blot analysis. Our present data demonstrate that PSMA can be enriched in exosomes, exhibiting a higher content of glycosylation and partial proteolysis in comparison to cellular PSMA. An in vitro enzyme assay further confirmed that exosomal PSMA retains functional enzymatic activity. Therefore, our data may suggest a new role for PSMA in prostate cancer progression, and provide opportunities for developing non-invasive approaches for diagnosis or prognosis of prostate cancer.

BACKGROUND & AIMS: α-taxilin was identified as binding partner of syntaxins and is supposed to regulate vesicular trafficking. However, the physiological functions of α-taxilin and its potential relevance for the life cycle of hepatitis B virus (HBV) are still poorly understood.
METHODS: Transfected hepatoma cells, infected primary human hepatocytes, and liver tissue of HBV-infected patients were used to study the expression of α-taxilin. Subcellular localization and colocalization were analyzed by confocal laser scanning microscopy (CLSM). Protein-protein interactions were further investigated by co-immunoprecipitations. Silencing of α-taxilin expression was performed by lentiviral gene transfer.
RESULTS: HBV producing cells show a significant higher level of α-taxilin. HBV induces α-taxilin expression, by its regulatory proteins HBx and LHBs via c-Raf. This indicates that α-taxilin is essential for the release of HBV particles. CLSM and co-immunoprecipitations demonstrated that the PreS1PreS2 domain of LHBs interacts with α-taxilin. α-taxilin harbors a YXXL motif that represents a classic late domain. In accordance with this, it was found by co-immunoprecipitations that α-taxilin interacts with the ESCRT I component tsg101. CLSM revealed that a fraction of α-taxilin colocalizes with LHBs and tsg101.
CONCLUSIONS: α-taxilin plays an essential role for release of HBV-DNA containing particles. It might act as an adapter that binds, on the one hand, to LHBs and, on the other hand, to tsg101 and thereby helps recruit the ESCRT machinery to the viral envelope proteins.

Ovarian cancer is the most lethal type of cancer among all frequent gynecologic malignancies, because most patients present with advanced disease at diagnosis. Exosomes are important intercellular communication vehicles, released by various cell types. Here we presented firstly the protein profile of highly purified exosomes derived from two ovarian cancer cell lines, OVCAR-3 and IGROV1. The exosomes derived from ovarian cancer cell lines were round and mostly 30-100 nm in diameter when viewed under an electron microscope. The exosomal marker proteins TSG101 and Alix were detected in exosome preparations. The range of density was between 1.09 g/ml and 1.15 g/ml. A total of 2230 proteins were identified from two ovarian cell-derived exosomes. Among them, 1017 proteins were identified in both exosomes including all of the major exosomal protein markers. There were 380 proteins that are not reported in the ExoCarta database. In addition to common proteins from exosomes of various origins, our results showed that ovarian cancer-derived exosomes also carried tissue specific proteins associated with tumorigenesis and metastasis, especially in ovarian carcinoma. Based on the known roles of exosomes in cellular communication, these data indicate that exosomes released by ovarian cancer cells may play important roles in ovarian cancer progression and provide a potential source of blood-based protein biomarkers.

The tumor susceptibility gene 101 (TSG101) encodes a multidomain protein that contains a UEV (ubiquitin e2 variant) domain at is N-terminus and a putative DNA-binding motif at its C-terminus. In addition to being a bona fide component of the ESCRT (endosomal sorting complexes required for transport) complex 1 and playing a critical role in endosomal sorting and trafficking, TSG101 has also been implicated in an array of cellular functions including, cytokinesis, protein ubiquitination, transcriptional regulation, cell cycle and proliferation, as well as viral budding. The major focus of this article is on the role of TSG101 in tumorigenesis.

Tumor susceptibility gene 101 (TSG101), a mammalian homologue of yeast vps23, is involved in protein sorting, vesicular trafficking and maintenance of genomic integrity. Upregulation of the TSG101 gene was found in human thyroid papillary and breast tumors. Here, we define the proximal promoter of human TSG101 at -1 to -436 by reporter assay. Intact Sp1 and MAZ binding sequences within this region are essential, and mutation of both sites eliminates proximal promoter activity implying cooperation between these two cis-elements. Chromatin immunoprecipitation and DNA affinity precipitation assay confirmed in vivo Sp1 binding on the GGGGCGGGTT sequence. MAZ protein was essential for TSG101 promoter activity because its knockdown using siRNA decreased reporter activity. An upstream regulatory element (URE) at the -1280 to -1757 region was identified to confer the orientation-independent enhancement of the promoter activity in transformed COS-1, ARO and WRO cell lines but not in a normal thyroid FRTL cell line. The sequence of this URE region contains putative binding sites for thyroid transcription factor 2 (TTF-2) and thyroid hormone receptor (T3R), which might be relevant to differential regulation of TSG101 promoter activity in transformed and primary cells.

Integrative genomics approaches associating DNA structure and transcriptomic analysis should allow the identification of cascades of events relating to tumor aggressiveness. While different genome alterations have been identified in pituitary tumors, none have ever been correlated with the aggressiveness. This study focused on one subtype of pituitary tumor, the prolactin (PRL) pituitary tumors, to identify molecular events associated with the aggressive and malignant phenotypes. We combined a comparative genomic hybridization and transcriptomic analysis of 13 PRL tumors classified as nonaggressive or aggressive. Allelic loss within the p arm region of chromosome 11 was detected in five of the aggressive tumors. Allelic loss in the 11q arm was observed in three of these five tumors, all three of which were considered as malignant based on the occurrence of metastases. Comparison of genomic and transcriptomic data showed that allelic loss impacted upon the expression of genes located in the imbalanced region. Data filtering allowed us to highlight five deregulated genes (DGKZ, CD44, TSG101, GTF2H1, HTATIP2), within the missing 11p region, potentially responsible for triggering the aggressive and malignant phenotypes of PRL tumors. Our combined genomic and transcriptomic analysis underlines the importance of chromosome allelic loss in determining the aggressiveness and malignancy of tumors.

We designed to investigate the effects of down-regulating the tumor susceptibility gene 101 (TSG101) on the proliferation and apoptosis of the human breast cancer MCF-7 cell line, and the role of the MAPK/ERK signal pathway in this process. The siRNA against TSG101 was transfected into the breast cancer MCF-7 cell line using Lipofectamine 2000. After TSG101 knockdown, the proliferation of MCF-7 cells was measured by the MTT assay. The cell cycle distribution and apoptosis were examined by using flow cytometry while cell migration was measured using a transwell assay. The protein level of p-ERK was further assessed by immunofluorescence and western blotting. Our results are as following, the MCF-7 cells transfected with TSG101 siRNA proliferated significantly slower and exhibited significantly increased rates of apoptosis compared to the control cells. In the TSG101 siRNA transfected cells, the percentage of cells in the G₀/G₁ and S phase of the cell cycle was significantly higher and lower, respectively, compared to the control cells. Moreover, the migration ability of TSG101 siRNA transfected cells was lower than the control groups. Lastly, the level of p-ERK protein in TSG101 siRNA transfected cells was significantly decreased compared with the control cells. In conclusion, TSG101 knockdown in breast cancer cells induces apoptosis and inhibits proliferation. The TSG101 depleted cells are arrested at the G₁/S transition of the cell cycle. The migration of breast cancer cells is also impaired by TSG101 siRNA. TSG101 may play a biological role through modulation of the MAPK/ERK signaling pathway in breast cancer.

Human papillomavirus (HPV)-mediated transformation of human epithelial cells has been recognized as a multi-step process in which additional unknown factors and (epi)genetic events are required. The tumor susceptibility gene 101 (TSG101) was discovered in mouse NIH3T3 fibroblast cells as a gene whose functional knockout leads to transformation. TSG101 protein is involved in a variety of important biological functions, such as ubiquitination, transcriptional regulation, endosomal trafficking, virus budding, proliferation and cell survival. It is suggested that TSG101 is an important factor for maintaining cellular homeostasis and that perturbation of TSG101 functions leads to cell transformation. Interestingly, a recent report showed up- or down-regulation of TSG101 in several human malignancies. At present, the role of TSG101 in cervical tumorigenesis is unexplained. TSG101 expression in tumors, where carcinogenesis is connected with viral infection, and a mechanism of TSG101 expression regulation in cancer cells are also unknown. The aim of our study was to estimate the TSG101 mRNA and protein level in cervical cancer and non-tumor epithelial cells. We also analyzed the TSG101 coding and promoter sequence using the PCR-SSCP technique and methylation pattern of the TSG101 promoter. Our real-time PCR and Western blot analysis showed decreased TSG101 mRNA and protein level in cervical cancer tissue in comparison to normal (non-tumor) HPV(-) and HPV16(+) epithelial cells. Our results suggest that TSG101 down-regulation in cervical cancer cells is not regulated by genetic or epigenetic events. However, we detected novel single nucleotide polymorphisms in the promoter of this gene.

Understanding the genesis and development of tumors is an essential component in cancer research. It is of interest to discover unknown genes that are responsible for cellular transformation. A cDNA library of a highly metastatic lung adenocarcinoma cell line was constructed. This library was introduced into the NIH3T3 mouse embryonic fibroblast cell line to screen for cDNAs that increase anchorage-independent colony formation in soft agar. The expression of TSG101 in lung cancer cell lines and specimens was confirmed using reverse transcription-polymerase chain reaction. The level of TSG101 protein in transfected A549 cells was determined by western blotting. Cell-cycle distribution was analyzed using a FACStar Plus flow cytometer. One of the candidate cDNAs that increases anchorage-independent colony formation was shown to correspond to the TSG101 cDNA sequence. Levels of TSG101 mRNA were higher in lung cancer cell lines and specimens compared to matched normal lung tissues. Ectopic expression of TSG101 in the A549 lung adenocarcinoma cell line increased the numbers of cells in S phase, suggesting an increased cell proliferation rate. These results indicate that TSG101 may induce the malignant phenotype of cells.

Cells can exchange information not only by means of chemical and/or electrical signals, but also via microvesicles released into the intercellular space. The present paper, for the first time, provides evidence that Glioblastoma and Astrocyte cells release microvesicles, which carry mitochondrial DNA (mtDNA). These microvesicles have been characterised as exosomes in view of the presence of some protein markers of exosomes, such as Tsg101, CD9 and Alix. Thus, the important finding has been obtained that bonafide exosomes, constitutively released by Glioblastoma cells and Astrocytes, can carry mtDNA, which can be, therefore, transferred between cells. This datum may help the understanding of some diseases due to mitochondrial alterations.

Class E Vps (vacuolar protein sorting) proteins are components of the ESCRTs (endosomal sorting complexes required for transport) which are required for protein sorting at the early endosome. Most of these genes have been identified and genetically characterized in yeast. Recent genetic studies in Drosophila have revealed the phenotypic consequences of loss of vps function in multicellular organisms. In the present paper, we review these studies and discuss a mechanism which may explain how loss of the human Tsg101 (tumour susceptibility gene 101), a vps23 orthologue, causes tumours.