Overexpression of tumor susceptibility gene TSG101 in human papillary thyroid carcinomas

HRS mediates tumor immune evasion by regulating proteostasis-associated interferon pathway activation

By sorting receptor tyrosine kinases into endolysosomes, the endosomal sorting complexes required for transport (ESCRTs) are thought to attenuate oncogenic signaling in tumor cells. Paradoxically, ESCRT members are upregulated in tumors. Here, we show that disruption of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), a pivotal ESCRT component, inhibited tumor growth by promoting CD8+ T cell infiltration in melanoma and colon cancer mouse models. HRS ablation led to misfolded protein accumulation and triggered endoplasmic reticulum (ER) stress, resulting in the activation of the type I interferon pathway in an inositol-requiring enzyme-1α (IRE1α)/X-box binding protein 1 (XBP1)-dependent manner. HRS was upregulated in tumor cells with high tumor mutational burden (TMB). HRS expression associates with the response to PD-L1/PD-1 blockade therapy in melanoma patients with high TMB tumors. HRS ablation sensitized anti-PD-1 treatment in mouse melanoma models. Our study shows a mechanism by which tumor cells with high TMB evade immune surveillance and suggests HRS as a promising target to improve immunotherapy.

The Contribution of Tumor Derived Exosomes to Cancer Cachexia

Cancer cachexia is defined as unintentional weight loss secondary to neoplasia and is associated with poor prognosis and outcomes. Cancer cachexia associated weight loss affects both lean tissue (i.e., skeletal muscle) and adipose tissue. Exosomes are extracellular vesicles that originate from multivesicular bodies that contain intentionally loaded biomolecular cargo. Exosome cargo includes proteins, lipids, mitochondrial components, and nucleic acids. The cargo carried in exosomes is thought to alter cell signaling when it enters into recipient cells. Virtually every cell type secretes exosomes and exosomes are known to be present in nearly every biofluid. Exosomes alter muscle and adipose tissue metabolism and biological processes, including macrophage polarization and apoptosis which contribute to the development of the cachexia phenotype. This has led to an interest in the role of tumor cell derived exosomes and their potential role as biomarkers of cancer cell development as well as their contribution to cachexia and disease progression. In this review, we highlight published findings that have studied the effects of tumor derived exosomes (and extracellular vesicles) and their cargo on the progression of cancer cachexia. We will focus on the direct effects of tumor derived exosomes and their cellular cross talk on skeletal muscle and adipose tissue, the primary sites of weight loss due to cancer cachexia.

Extracellular Vesicle-Mediated Mitochondrial Reprogramming in Cancer

Simple Summary

Mitochondria are important organelles involved in several key cellular processes including energy production and cell death regulation. For this reason, it is unsurprising that mitochondrial function and structure are altered in several pathological states including cancer. Cancer cells present variate strategies to generate sufficient energy to sustain their high proliferation rates. These adaptative strategies can be mediated by extracellular signals such as extracellular vesicles. These vesicles can alter recipient cellular behavior by delivering their molecular cargo. This review explores the different EV-mediated mitochondrial reprogramming mechanisms supporting cancer survival and progression.

Abstract

Altered metabolism is a defining hallmark of cancer. Metabolic adaptations are often linked to a reprogramming of the mitochondria due to the importance of these organelles in energy production and biosynthesis. Cancer cells present heterogeneous metabolic phenotypes that can be modulated by signals originating from the tumor microenvironment. Extracellular vesicles (EVs) are recognized as key players in intercellular communications and mediate many of the hallmarks of cancer via the delivery of their diverse biological cargo molecules. Firstly, this review introduces the most characteristic changes that the EV-biogenesis machinery and mitochondria undergo in the context of cancer. Then, it focuses on the EV-driven processes which alter mitochondrial structure, composition, and function to provide a survival advantage to cancer cells in the context of the hallmarks of cancers, such as altered metabolic strategies, migration and invasiveness, immune surveillance escape, and evasion of apoptosis. Finally, it explores the as yet untapped potential of targeting mitochondria using EVs as delivery vectors as a promising cancer therapeutic strategy.

Multidimensional Analysis of the Role of Charged Multivesicular Body Protein 7 in Pan-Cancer

Background

Charged multivesicular body protein 7 is briefly referred to as CHMP7, and it plays a significant role in the endosomal sorting pathway. CHMP7 can form a complex with ESCRTIII to jointly complete the process of contraction, shear bud neck and final membrane shedding.

Methods

TCGA, GEO and CPTAC were chosen for the analysis of the role of CHMP7 in pan-cancer. Role of CHMP7 in pan-cancer was analyzed using R software and tools such as TIMER, GEPIA, UALCAN, String and DiseaseMeth. It includes differential expression analysis of CHMP7, survival analysis, genetic variation analysis, DNA methylation analysis, post-translationally modified protein phosphorylation analysis and functional enrichment analysis.

Results

CHMP7 presents low expression in the majority of tumor tissues and the prognosis is poor in the low expression group. The common gene mutation in CHMP7 is deep deletion, which may lead to frameshift mutations, resulting in a poor prognosis. Functional alterations due to DNA methylation and post-transcriptional protein modifications may be closely associated with tumors. GO analysis revealed that CHMP7-related genes are involved in the composition of the various ESCRT complexes. In terms of molecular function, they mainly bind to GTP, exert GTPase activity and promote multivesicular bodies assembly. In the KEGG enrichment analysis, the main pathways expressed by CHMP7 and related genes were endocytosis, gap junction and phagosome.

Conclusion

Pan-cancer analysis showed that CHMP7 expression was statistically correlated with clinical prognosis, DNA methylation, protein phosphorylation and immune cell infiltration, which may provide new ideas or targets for the diagnosis or treatment.

Nanoplasmonic Sensor Approaches for Sensitive Detection of Disease-Associated Exosomes

Exosomes are abundantly secreted by most cells that carry membrane and cytosolic factors that can reflect the physiologic state of their source cells and thus have strong potential to serve as biomarkers for early diagnosis, disease staging, and treatment monitoring. However, traditional diagnostic or prognostic applications that might use exosomes are hindered by the lack of rapid and sensitive assays that can exploit their biological information. An array of assay approaches have been developed to address this deficit, including those that integrate immunoassays with nanoplasmonic sensors to measure changes in optical refractive indexes in response to the binding of low concentrations of their targeted molecules. These sensors take advantage of enhanced and tunable interactions between the electron clouds of nanoplasmonic particles and structures and incident electromagnetic radiation to enable isolation-free and ultrasensitive quantification of disease-associated exosome biomarkers present in complex biological samples. These unique advantages make nanoplasmonic sensing one of the most competitive approaches available for clinical applications and point-of-care tests that evaluate exosome-based biomarkers. This review will briefly summarize the origin and clinical utility of exosomes and the limitations of current isolation and analysis approaches before reviewing the specific advantages and limitations of nanoplasmonic sensing devices and indicating what additional developments are necessary to allow the translation of these approaches into clinical applications.

Knockdown of ANXA10 inhibits proliferation and promotes apoptosis of papillary thyroid carcinoma cells by down-regulating TSG101 thereby inactivating the MAPK/ERK signaling pathway

Annexin A10 (ANXA10) is a member of annexin A and has been reported to highly express in papillary thyroid carcinoma (PTC) tissues. Tumor susceptibility gene 101 (TSG101) also plays a role in PTC and is predicted to bind to ANXA10. This study intended to investigate whether ANXA10 could regulate PTC via binding to ANXA10. The expression of ANXA10 and TSG101 in normal thyroid follicular epithelial cell line and several PTC cell lines was analyzed using RT-qPCR and western blotting assays. Subsequently, PTC cell line BCPAP was silenced with ANXA10 followed by TSG101 overexpression or not, and then cell proliferation, apoptosis and mitogen-activated protein kinase (MAPK) signaling expression were assessed via MTT, colony formation, immunofluorescence staining, Tunel staining and western blotting assays. Besides, the interaction between ANXA10 and TSG101 was validated using Co-immunoprecipitation assay. ANXA10 and TSG101 expressions were up-regulated in PTC cell lines. ANXA10 silence inhibited proliferation, promoted apoptosis and inactivated MAPK/ extracellular regulated protein kinases (ERK) signaling pathway of BCPAP cells. Additionally, ANXA10 could bind to TSG101 and regulate its expression. However, the above effects of ANXA10 silence on BCPAP cells were all blocked by TSG101 overexpression. ANXA10 inhibited proliferation and promoted apoptosis of PTC cells via binding to TSG101, and these actions may depend on down-regulating MAPK/ERK pathway expression.

High expression of tumor susceptibility gene 101 (TSG101) is associated with more aggressive behavior in colorectal carcinoma

INTRODUCTION

Identification of genetic determinants such as exosomal content that drives progression and metastasis of colorectal cancer (CRC) has received considerable attention. The present study aims to identify a suitable biomarker in CRC tissues and exosomes based on bioinformatics data to evaluate its expression patterns in CRC tissues as well as its clinicopathological significance.

MATERIALS AND METHODS

Protein-protein interaction (PPI) network and enrichment analysis were applied to identify up-regulated genes that contributed in CRC exosomes to select the marker. The expression patterns and clinical significance of selected exosomal marker were evaluated in tissue microarrays (TMAs) of 445 CRC tumors and 39 adjacent normal tissues using immunohistochemistry method.

RESULTS

Based on bioinformatics data, TSG101 gene was prominent amongst the tumor tissues and exosomes. Expression of TSG101 was significantly up-regulated in tumor cells compared to adjacent normal tissues (p-value = 0.04). Moreover, higher expressions of TSG101 (cytoplasmic and nuclear) were significantly associated with tumor differentiation (p-value = 0.042) and distant metastasis (p-value = 0.027). A significant association was found in the cytoplasmic expression of TSG101 between well and moderate tumor differentiation (p-value = 0.005) as well as moderate and poor differentiation (p-value = 0.050).

CONCLUSION

These findings indicate that the exploration of crosstalk between exosome content and CRC may be valuable for the development of novel exosomal biomarkers. Increased expression of TSG101, as a promising exosome marker, is more associated with more aggressive tumor behaviors, metastasis, and progression of CRC, which paves the way for therapeutic strategies and CRC management. However, further investigations are warranted to clarify the molecular mechanisms of TSG101 in CRC.

Exosomes and Cell Communication: From Tumour-Derived Exosomes and Their Role in Tumour Progression to the Use of Exosomal Cargo for Cancer Treatment

Simple Summary

Recently, within the research community, exosomes, transporters of bioactive molecules involved in many signalling pathways and cell-to-cell communication with the capacity to alter the tumour microenvironment, have been attracting increasing interest among oncologists. These molecules can play multiple roles, e.g., as useful biomarkers in diagnosis, modulators of the immune system, promoters of the formation of the pre-metastatic niches and cancer metastasis and carriers of substances or factors with anticancer properties. This review focuses on the use of exosomes as a novel therapeutic strategy for cancer treatment. Particularly, it highlights the potential of exosomes as carriers of stem cell differentiation stage factors (SCDSFs) for “cell reprogramming” therapy, a promising research field on which we have reported previously. Here, the main characteristics of this treatment and the advantages that can be obtained using mesenchymal stem cell-derived exosomes up-loaded with the SCDSFs as carriers of these factors are also discussed.

Abstract

Exosomes are nano-vesicle-shaped particles secreted by various cells, including cancer cells. Recently, the interest in exosomes among cancer researchers has grown enormously for their many potential roles, and many studies have focused on the bioactive molecules that they export as exosomal cargo. These molecules can function as biomarkers in diagnosis or play a relevant role in modulating the immune system and in promoting apoptosis, cancer development and progression. Others, considering exosomes potentially helpful for cancer treatment, have started to investigate them in experimental therapeutic trials. In this review, first, the biogenesis of exosomes and their main characteristics was briefly described. Then, the capability of tumour-derived exosomes and oncosomes in tumour microenvironments (TMEs) remodelling and pre-metastatic niche formation, as well as their interference with the immune system during cancer development, was examined. Finally, the potential role of exosomes for cancer therapy was discussed. Particularly, in addition, their use as carriers of natural substances and drugs with anticancer properties or carriers of boron neutron capture therapy (BNCT) and anticancer vaccines for immunotherapy, exosomes as biological reprogrammers of cancer cells have gained increased consensus. The principal aspects and the rationale of this intriguing therapeutic proposal are briefly considered.

TSG101 Promotes the Proliferation, Migration, and Invasion of Human Glioma Cells by Regulating the AKT/GSK3β/β-Catenin and RhoC/Cofilin Pathways

The tumor susceptibility gene 101 (TSG101) has been reported to play important roles in the development and progression of several human cancers, such as pancreatic cancer, prostate cancer, and hepatocellular carcinoma. However, its potential roles and underlined mechanisms in human glioma are still needed to be further clarified. This study was designed to assess the expression of TSG101 in glioma patients and its effects on glioma cell proliferation, migration, and invasion. Publicly available data revealed that TSG101 mRNA was significantly upregulated in glioma tissues, and high levels of TSG101 were associated with poor prognosis in glioma patients. Western blot and immunohistochemistry experiments further showed that the expression level of TSG101 protein was significantly upregulated in glioma patients, especially in the patients with high-grade glioma. The functional studies showed that knockdown of TSG101 suppressed the proliferation, migration, and invasion of glioma cells, while overexpression of TSG101 facilitated them. Mechanistic studies indicated that the proliferation, migration, and invasion induced by TSG101 in human glioma were related to AKT/GSK3β/β-catenin and RhoC/Cofilin signaling pathways. In conclusion, the above results suggest that the expression of TSG101 is elevated in glioma patients, which accelerates the proliferation, migration, and invasion of glioma cells by regulating the AKT/GSK3β/β-catenin and RhoC/Cofilin pathways.

Exosomes are the Driving Force in Preparing the Soil for the Metastatic Seeds: Lessons from the Prostate Cancer

Exosomes are nano-membrane vesicles that various cell types secrete during physiological and pathophysiological conditions. By shuttling bioactive molecules such as nucleic acids, proteins, and lipids to target cells, exosomes serve as key regulators for multiple cellular processes, including cancer metastasis. Recently, microvesicles have emerged as a challenge in the treatment of prostate cancer (PCa), encountered either when the number of vesicles increases or when the vesicles move into circulation, potentially with an ability to induce drug resistance, angiogenesis, and metastasis. Notably, the exosomal cargo can induce the desmoplastic response of PCa-associated cells in a tumor microenvironment (TME) to promote PCa metastasis. However, the crosstalk between PCa-derived exosomes and the TME remains only partially understood. In this review, we provide new insights into the metabolic and molecular signatures of PCa-associated exosomes in reprogramming the TME, and the subsequent promotion of aggressive phenotypes of PCa cells. Elucidating the molecular mechanisms of TME reprogramming by exosomes draws more practical and universal conclusions for the development of new therapeutic interventions when considering TME in the treatment of PCa patients.

The Multifaceted Roles of the Tumor Susceptibility Gene 101 (TSG101) in Normal Development and Disease

The multidomain protein encoded by the Tumor Susceptibility Gene 101 (TSG101) is ubiquitously expressed and is suggested to function in diverse intracellular processes. In this review, we provide a succinct overview of the main structural features of the protein and their suggested roles in molecular and cellular functions. We then summarize, in more detail, key findings from studies using genetically engineered animal models that demonstrate essential functions of TSG101 in cell proliferation and survival, normal tissue homeostasis, and tumorigenesis. Despite studies on cell lines that provide insight into the molecular underpinnings by which TSG101 might function as a negative growth regulator, a biologically significant role of TSG101 as a tumor suppressor has yet to be confirmed using genuine in vivo cancer models. More recent observations from several cancer research teams suggest that TSG101 might function as an oncoprotein. A potential role of post-translational mechanisms that control the expression of the TSG101 protein in cancer is being discussed. In the final section of the review, we summarize critical issues that need to be addressed to gain a better understanding of biologically significant roles of TSG101 in cancer.

Cancer-Derived Extracellular Vesicle-Associated MicroRNAs in Intercellular Communication: One Cell's Trash Is Another Cell's Treasure

Several non-protein-coding genomic regions, previously marked as "junk DNA", have been reported to be transcriptionally active, giving rise to non-coding RNA species implicated in fundamental biological and pathological processes. In particular, microRNAs (miRNAs), a class of small non-coding RNAs mediating post-transcriptional gene silencing, are causally involved in several human diseases, including various cancer types. Extracellular vesicles (EVs) are membranous structures physiologically released by most cell types. Initially, they were considered a "waste-removal" mechanism, through which cells could dispose unnecessary material and organelles. It is now widely demonstrated that EVs also play a critical role in intercellular communication, mediating the horizontal transfer of lipids, proteins, and genetic material. A paradigm shift in the biology of miRNAs was represented by the discovery that EVs, especially from cancer cells, contain miRs. EV-associated miRs act as autocrine, paracrine and endocrine factors, participating in cancer pathogenesis by modulating intercellular communication. Noteworthy, these formerly neglected molecules are now considered the next generation of cancer "theranostic" tools, with strong clinical relevance. In this review, we aim to summarize the most recent findings regarding EV-associated miRs in cancer pathogenesis and in the development of novel anti-neoplastic diagnostic and therapeutic approaches.

Tumor-derived exosomes, myeloid-derived suppressor cells, and tumor microenvironment

Plenty of immune cells infiltrate into the tumor microenvironment (TME) during tumor progression, in which myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells with immunosuppressive activity. Tumor cells and stromal cells facilitate the activation and expansion of MDSCs in TME via intercellular communication, and expanded MDSCs suppress anti-tumor immune responses through direct and indirect mechanisms. Currently, exosomes, which are a kind of extracellular vesicles (EVs) that can convey functional components, are demonstrated to participate in the local and distal intercellular communication between cells. Numerous studies have supposed that tumor-derived exosomes (TEXs), whose assembly and release can be modulated by TME, are capable of modulating the cell biology of MDSCs, including facilitating their activation, promoting the expansion, and enhancing the immunosuppressive function. Therefore, in this review, we mainly focus on the role of TEXs in the cell-cell communication between tumor cells and MDSCs, and discuss their clinical applications.

Tumor-derived exosomes (TDEs): How to avoid the sting in the tail

Exosomes are abundantly secreted extracellular vesicles that accumulate in the circulation and are of great interest for disease diagnosis and evaluation since their contents reflects the phenotype of their cell of origin. Tumor‐derived exosomes (TDEs) are of particular interest for cancer diagnosis and therapy, since most tumor demonstrate highly elevated exosome secretion rates and provide specific information about the genotype of a tumor and its response to treatment. TDEs also contain regulatory factors that can alter the phenotypes of local and distant tissue sites and alter immune cell functions to promote tumor progression. The abundance, information content, regulatory potential, in vivo half‐life, and physical durability of exosomes suggest that TDEs may represent a superior source of diagnostic biomarkers and treatment targets than other materials currently under investigation. This review will summarize current information on mechanisms that may differentially regulate TDE biogenesis, TDE effects on the immune system that promote tumor survival, growth, and metastasis, and new approaches understudy to counteract or utilize TDE properties in cancer therapies.

Extracellular vesicles in onco-nephrology

Extracellular vesicles (EVs) are important mediators of intercellular communication in cancer and in normal tissues. EVs transfer biologically active molecules from the cell of origin to recipient cells. This review summarizes the studies on EVs derived from renal cell carcinoma and from a subpopulation of CD105-positive renal cancer stem cells. While EVs from renal cell carcinoma show mild biological activity, EVs from renal cancer stem cells enhance tumor angiogenesis and metastasis formation. The effect is probably due to the transfer of proangiogenic RNA cargo to endothelial cells, which acquire an activated angiogenic phenotype. In vivo, treatment with EVs favors the formation of a premetastatic niche in the lungs. Moreover, EVs derived from renal cancer stem cells modify gene expression in mesenchymal stromal cells, enhancing the expression of genes involved in matrix remodeling, cell migration, and tumor growth. Mesenchymal stromal cells preconditioned with tumor EVs and then coinjected in vivo with renal cancer cells support tumor growth and vessel formation. Finally, tumor EVs promote tumor immune escape by inhibiting the differentiation process of dendritic cells and the activation of T cells. Thus, tumor-derived EVs act on the microenvironment favoring tumor aggressiveness, may contribute to angiogenesis through both direct and indirect mechanisms and are involved in tumor immune escape.

Membrane-bound packages called extracellular vesicles (EVs) released by kidney cancer stem cells can make tumors more aggressive, promote the onset of cancer at other sites, and help tumors escape the anti-cancer immune response. Giovanni Camussi and colleagues at the University of Turin, Italy, review understanding of EVs from kidney cancer cells. EVs from cancer stem cells are especially effective in promoting cancer, unlike those from mature cancer cells. This is partly due to their ability to promote the formation of new blood vessels to sustain tumor growth. Some of the vesicles’ effects are mediated by transferring small molecules of ribonucleic acid (RNA) into other cells. These RNAs can regulate the activity of specific genes, promoting cancer. Studying patients’ EVs may assist cancer diagnosis and help predict the likely progression of the disease.

Cancer-Specifically Re-Spliced TSG101 mRNA Promotes Invasion and Metastasis of Nasopharyngeal Carcinoma

TSG101 (Tumor susceptibility 101) gene and its aberrantly spliced isoform, termed TSG101∆154-1054, are tightly linked to tumorigenesis in various cancers. The aberrant TSG101∆154-1054 mRNA is generated from cancer-specific re-splicing of mature TSG101 mRNA. The TSG101∆154-1054 protein protects the full-length TSG101 protein from ubiquitin-mediated degradation, implicating TSG101∆154-1054 protein in the progression of cancer. Here, we confirmed that the presence of TSG101∆154-1054 mRNA indeed caused an accumulation of the TSG101 protein in biopsies of human nasopharyngeal carcinoma (NPC), which was recapitulated by the overexpression of TSG101∆154-1054 in the NPC cell line TW01. We demonstrate the potential function of the TSG101∆154-1054 protein in the malignancy of human NPC with scratch-wound healing and transwell invasion assays. By increasing the stability of the TSG101 protein, TSG101∆154-1054 specifically enhanced TSG101-mediated TW01 cell migration and invasion, suggesting the involvement in NPC metastasis in vivo. This finding sheds light on the functional significance of TSG101∆154-1054 generation via re-splicing of TSG101 mRNA in NPC metastasis and hints at its potential importance as a therapeutic target.

siRNA against TSG101 reduces proliferation and induces G0/G1 arrest in renal cell carcinoma - involvement of c-myc, cyclin E1, and CDK2

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.

TSG101 promotes the proliferation, migration and invasion of hepatocellular carcinoma cells by regulating the PEG10

The tumour susceptibility gene 101 (TSG101) is reported to play important roles in the development and progression of several human cancers. However, its potential roles and underlined mechanisms in human hepatocellular carcinoma (HCC) are still needed to be further clarified. In the present study, we reported that knock down of TSG101 suppressed the proliferation, migration and invasion of HCC cells, while overexpression of TSG101 facilitated them. Molecularly, the results revealed that knock down of TSG101 significantly decreased the cell cycle related regulatory factor p53 and p21. In another point, knock down of TSG101 also obviously decreased the level of metallopeptidase inhibitor TIMP1 (Tissue inhibitors of metalloproteinases 1), which results in inhibition of MMP2, MMP7 and MMP9. In contrast, overexpression of TSG101 had opposite effects. The iTRAQ proteomics analysis identified that oncogenic protein PEG10 (Paternally expressed gene 10) might be a potential downstream target of TSG101. Further investigation showed that TSG101 interacted with PEG10 and protected it from proteasomal degradation thereby regulating the expression of p53, p21 and MMPs. Finally, we found that both TSG101 and PEG10 proteins are up-regulated and presented a direct correlation in HCC patients. In conclusion, these results suggest that TSG101 is up-regulated in human HCC patients, which may accelerate the proliferation, migration and invasion of HCC cells through regulating PEG10.

Biogenesis and function of extracellular vesicles in cancer

Extracellular vesicles (EVs) are heterogeneous multi-signal messengers that support cancer growth and dissemination by mediating the tumor-stroma crosstalk. Exosomes are a subtype of EVs that originate from the limiting membrane of late endosomes, and as such contain information linked to both the intrinsic cell "state" and the extracellular signals cells received from their environment. Resolving the signals affecting exosome biogenesis, cargo sorting and release will increase our understanding of tumorigenesis. In this review we highlight key cell biological processes that couple exosome biogenesis to cargo sorting in cancer cells. Moreover, we discuss how the bidirectional communication between tumor and non-malignant cells affect cancer growth and metastatic behavior.

Exploration of the platelet proteome in patients with early-stage cancer

Platelets play an important role in tumor growth and, at the same time, platelet characteristics are affected by cancer presence. Therefore, we investigated whether the platelet proteome harbors differentially expressed proteins associated with early-stage cancer. For this proof-of-concept study, patients with early-stage lung (n = 8) or head of pancreas cancer (n = 4) were included, as were healthy sex- and age-matched controls for both subgroups. Blood samples were collected from controls and from patients before surgery. Furthermore, from six of the patients, a second sample was collected two months after surgery. NanoLC-MS/MS-based proteomics of gel-fractionated platelet proteins was used for comparative spectral count analyses of patients to controls and before to after surgery samples. The total platelet proteome dataset included 4384 unique proteins of which 85 were significantly (criteria Fc > 1.5 and p < 0.05) changed in early-stage cancer compared to controls. In addition, the levels of 81 platelet proteins normalized after tumor resection. When filtering for the most discriminatory proteins, we identified seven promising platelet proteins associated with early-stage cancer. In conclusion, this pioneering study on the platelet proteome in cancer patients clearly identifies platelets as a new source of candidate protein biomarkers of early-stage cancer.

BIOLOGICAL SIGNIFICANCE

Currently, most blood-based diagnostics/biomarker research is performed in serum or plasma, while the content of blood cells is usually neglected. It is known that especially blood platelets, which are the main circulating pool of many bioactive proteins, such as growth factors, chemokines, and cytokines, are a potentially rich source of biomarkers. The current study is the first to measure the effect of early-stage cancer on the platelet proteome of patients. Our study demonstrates that the platelet proteome of patients with early-stage lung or head of pancreas cancer differs considerably compared to that of healthy individuals of matched sex and age. In addition, the platelet proteome of cancer patients normalized after surgical resection of the tumor. Exploiting platelet proteome differences linked to both tumor presence and disease status, we were able to demonstrate that the platelet proteome can be mined for potential biomarkers of cancer.

Role of ESCRT component HD-PTP/PTPN23 in cancer

Sustained cellular signalling originated from the receptors located at the plasma membrane is widely associated with cancer susceptibility. Endosomal sorting and degradation of the cell surface receptors is therefore crucial to preventing chronic downstream signalling and tumorigenesis. Since the Endosomal Sorting Complexes Required for Transport (ESCRT) controls these processes, ESCRT components were proposed to act as tumour suppressor genes. However, the bona fide role of ESCRT components in tumorigenesis has not been clearly demonstrated. The ESCRT member HD-PTP/PTPN23 was recently identified as a novel haplo-insufficient tumour suppressor in vitro and in vivo, in mice and humans. In this mini-review, we outline the role of the ESCRT components in cancer and summarize the functions of HD-PTP/PTPN23 in tumorigenesis.

TSGΔ154-1054 splice variant increases TSG101 oncogenicity by inhibiting its E3-ligase-mediated proteasomal degradation

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.

TSG101 Silencing Suppresses Hepatocellular Carcinoma Cell Growth by Inducing Cell Cycle Arrest and Autophagic Cell Death

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/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.

ESCRT proteins: Double-edged regulators of cellular signaling

ESCRT pathway proteins play a key role in sorting ubiquitinated membrane receptors towards lysosomes providing an important mechanism for attenuating cell surface receptor signaling. However, recent studies point to a positive role of ESCRT proteins in signal transduction in multiple species studied under physiological and pathological conditions. ESCRT components such as Tsg101 and Hrs are overexpressed in human cancers and Tsg101 depletion is detrimental for cell proliferation, survival and transformed phenotype of tumor cells. However, the mechanisms underlying the positive contributions of ESCRT pathway to surface receptor signaling have remained unclear. In a recent study, we showed that Tsg101 and Vps4 are essential for translocation of active Src from endosomes to focal adhesion and invadopodia, thereby revealing a role of ESCRT pathway in promoting Src-mediated migration and invasion. We discuss the implications of these and other recent studies which together suggest a role for the ESCRT pathway in recycling of endocytic cargo proteins, aside from its role in lysosomal targeting, potentially explaining the positive roles of ESCRT proteins in signal transduction.

The role of the endosomal sorting complexes required for transport (ESCRT) in tumorigenesis

The endosomal sorting complexes required for transport (ESCRT) are needed for three distinct cellular functions in higher eukaryotes: (i) Multivesicular body formation for the degradation of transmembrane proteins in lysosomes, (ii) midbody abscission during cytokinesis and (iii) retroviral budding. Not surprisingly, loss of ESCRT function has severe consequences, which include the failure to down-regulate growth factor receptors leading to deregulated mitogenic signaling. While it is clear that the function of the ESCRT machinery is important for embryonic development, its role in cancer is more controversial. Various experimental approaches in different model organisms arrive at partially divergent conclusions regarding the contribution of ESCRTs to tumorigenesis. Therefore the aim of this review is to provide an overview on different model systems used to study the role of the ESCRT machinery in cancer development, to highlight common grounds and present certain controversies in the field.

Engineering a synthetic cell panel to identify signalling components reprogrammed by the cell growth regulator anterior gradient-2

AGR2 forms an ER-resident signalling axis in cell development, limb regeneration, and in human diseases like asthma and cancer, yet molecular mechanisms underlying its effects remain largely undefined. A single integrated Flippase recombination target (FRT) site was engineered within the AGR2-non expressing A375 cell line to allow integration of a constitutively expressed AGR2 alleles. This allows an analysis of how AGR2 protein expression reprogrammes intracellular signalling. The engineered expression of AGR2 had marginal impact on global transcription signalling, compared to its paralogue AGR3. However, expression of AGR2 had a significant impact on remodelling the cellular proteome using a triple-labelled SILAC protocol. 29 045 peptides were detected for the identification and relative quantitation of 3003 proteins across the experimental conditions. Ingenuity Pathway annotation highlighted the dominant pathway suppressed by wt-AGR2 was the p53-signalling axis. DNA damage induced p53 stabilization and p21 induction by cisplatin treatment confirmed that wt-AGR2 expression suppressed the p53 pathway. The furthest outlying SILAC protein expression change induced by AGR2 was the anti-viral and cell cycle regulator tumour susceptibility gene 101 (TSG101), confirmed by immunoblotting. Transfection of TSG101 into MCF7 (AGR2+, oestrogen dependent), A549 (AGR2+, oestrogen independent) or A375 (AGR2-) cells confirmed that TSG101 attenuates p53 signalling. These systems wide screens suggest that the most dominant landscape reprogrammed by low levels of AGR2 protein is the cellular proteome, rather than the transcriptome, and provide focus for evaluating its role in proteostasis.

Altered trafficking of mutated growth factor receptors and their associated molecules: implication for human cancers

Ligand-stimulated receptor tyrosine kinases (RTKs) are phosphorylated/ubiquitinated, endocytosed and transported to the lysosomes via endosomes/multivesicular bodies, resulting in the attenuation of signal transmission. If this physiological mechanism of RTK signal downregulation is perturbed, signal transduction persists and may contribute to cellular transformation. This article presents several such examples. In some cases, endocytosis is impaired, and the activated RTK remains on the plasma membrane. In other cases, the activated RTK is endocytosed into endosomes/multivesicular bodies, but not subsequently sorted to the lysosomes for degradation. The latter cases indicate that even endocytosed RTKs can transmit signals. Transport of RTKs is accomplished via the formation and movement of membrane vesicles. Blockage or delay of endocytosis/trafficking can be caused by genetic alterations in the RTK itself or by mutations in CBL, Arf GAPs, or other components involved in internalization and vesicle transport. A survey of the literature indicates that, in some cases, even RTKs synthesized de novo can initiate signaling at the endoplasmic reticulum/Golgi before reaching the plasma membrane. The spectrum of molecules targeted by the signal is likely to be different between cell surface- and endoplasmic reticulum/Golgi-localized RTKs.

Expression of TSG101 protein and LSF transcription factor in HPV-positive cervical cancer cells

Our previous study demonstrated a decreased expression of tumor susceptibility gene 101 (TSG101) in cervical cancer cells. To identify the mechanism responsible for TSG101 downregulation during cervical cancer development, we analyzed the TSG101 promoter using cis-element cluster finder software. One of the transcription factors whose binding site was detected in the TSG101 promoter was late SV40 factor (LSF). The aim of this study was to analyze the TSG101 protein and LSF expression levels during cervical cancer development. Immunohistochemical analysis confirmed a previously observed decreased expression of TSG101, whereas quantitative polymerase chain reaction (qPCR) and immunohistochemistry analysis revealed high expression of LSF in cervical, precancer and cancer cells compared with human papillomavirus (HPV)-negative non-cancer samples. High expression of LSF in cervical cancer HPV-positive cells suggests that this protein may be important in the regulation of TSG101 expression, as well as in cervical carcinogenesis. The role of LSF as a mediator in cervical cancer development must be confirmed in future studies.

TSG101 and PEG10 are prognostic markers in squamous cell/adenosquamous carcinomas and adenocarcinoma of the gallbladder

The clinicopathological characteristics of squamous cell/adenosquamous carcinoma (SC/ASC) are currently not well documented, and as the prevalence of SC/ASC is uncommon in gallbladder cancers, a prognostic marker has not yet been found. In the present study, the expression of tumor susceptibility gene (TSG) 101 and paternally expressed gene (PEG) 10 was assessed in 46 SC/ASCs and 80 adenocarcinomas (ACs) using immunohistochemistry, and the samples were further analyzed to examine correlations with the clinicopathological characteristics. It was demonstrated that positive TSG101 and PEG10 expression were significantly associated with large tumor size, high tumor-node-metastasis (TNM) stage, lymph node metastasis, invasion and no resection (only biopsy) of SC/ASC and AC. The univariate Kaplan-Meier analysis showed that positive TSG101 and PEG10 expression, and differentiation, tumor size, TNM stage, lymph node metastasis, invasion and surgical curability, is closely associated with a decreased overall survival in SC/ASC and AC patients (P<0.05 or P<0.001). The multivariate Cox regression analysis identified that positive TSG101 and PEG10 expression are independent factors for a poor-prognosis in SC/ASC and AC patients. The present study indicates that positive TSG101 and PEG10 expression are closely associated with the clinical, pathological and biological behaviors, and a poor prognosis in gallbladder cancer.

Endosomal signaling and oncogenesis

The endosomal system provides a route whereby nutrients, viruses, and receptors are internalized. During the course of endocytosis, activated receptors can accumulate within endosomal structures and certain signal-transducing molecules can be recruited to endosomal membranes. In the context of signaling and cancer, they provide platforms within the cell from which signals can be potentiated or attenuated. Regulation of the duration of receptor signaling is a pivotal means of refining growth responses in cells. In cancers, this is often considered in terms of mutations that affect receptor tyrosine kinases and maintain them in hyperactivated states of dimerization and/or phosphorylation. However, disruption to the regulatory control exerted by the assembly of protein complexes within the endosomal network can also contribute to disease among which oncogenesis is characterized in part by dysregulated growth, enhanced cell survival, and changes in the expression of markers of differentiation. In this chapter, we will discuss the role of proteins that regulate in endocytosis as tumor suppressors or oncogenes and how changing the fate of internalized receptors and concomitant endosomal signaling can contribute to cancer.

Identification of TSG101 functional domains and p21 loci required for TSG101-mediated p21 gene regulation

TSG101 (tumor susceptibility gene 101) is a multi-domain protein known to act in the cell nucleus, cytoplasm, and periplasmic membrane. Remarkably, TSG101, whose location within cells varies with the stage of the cell cycle, affects biological events as diverse as cell growth and proliferation, gene expression, cytokinesis, and endosomal trafficking. The functions of TSG101 additionally are recruited for viral and microvesicle budding and for intracellular survival of invading bacteria. Here we report that the TSG101 protein also interacts with and down-regulates the promoter of the p21^CIP1/WAF1tumor suppressor gene, and identify a p21 locus and TSG101 domains that mediate this interaction. TSG101 deficiency in Saos-2 human osteosarcoma cells was accompanied by an increased abundance of p21 mRNA and protein and the retardation of cell proliferation. A cis-acting element in the p21 promoter that interacts with TSG101 and is required for promoter repression was located using chromatin immunoprecipitation (ChIP) analysis and p21-driven luciferase reporter gene expression, respectively. Additional analysis of TSG101 deletion mutants lacking specific domains established the role of the central TSG101 domains in binding to the p21 promoter and demonstrated the additional essentiality of the TSG101 C-terminal steadiness box (SB) in the repression of p21 promoter activity. Neither binding of TSG101 to the p21 promoter nor repression of this promoter required the TSG101 N-terminal UEV domain, which mediates the ubiquitin-recognition functions of TSG101 and its actions as a member of ESCRT endocytic trafficking complexes, indicating that regulation of the p21 promoter by TSG101 is independent of its role in such trafficking.

Membrane fission reactions of the mammalian ESCRT pathway

The endosomal sorting complexes required for transport (ESCRT) pathway was initially defined in yeast genetic screens that identified the factors necessary to sort membrane proteins into intraluminal endosomal vesicles. Subsequent studies have revealed that the mammalian ESCRT pathway also functions in a series of other key cellular processes, including formation of extracellular microvesicles, enveloped virus budding, and the abscission stage of cytokinesis. The core ESCRT machinery comprises Bro1 family proteins and ESCRT-I, ESCRT-II, ESCRT-III, and VPS4 complexes. Site-specific adaptors recruit these soluble factors to assemble on different cellular membranes, where they carry out membrane fission reactions. ESCRT-III proteins form filaments that draw membranes together from the cytoplasmic face, and mechanistic models have been advanced to explain how ESCRT-III filaments and the VPS4 ATPase can work together to catalyze membrane fission.

De-regulation of JNK and JAK/STAT signaling in ESCRT-II mutant tissues cooperatively contributes to neoplastic tumorigenesis

Multiple genes involved in endocytosis and endosomal protein trafficking in Drosophila have been shown to function as neoplastic tumor suppressor genes (nTSGs), including Endosomal Sorting Complex Required for Transport-II (ESCRT-II) components vacuolar protein sorting 22 (vps22), vps25, and vps36. However, most studies of endocytic nTSGs have been done in mosaic tissues containing both mutant and non-mutant populations of cells, and interactions among mutant and non-mutant cells greatly influence the final phenotype. Thus, the true autonomous phenotype of tissues mutant for endocytic nTSGs remains unclear. Here, we show that tissues predominantly mutant for ESCRT-II components display characteristics of neoplastic transformation and then undergo apoptosis. These neoplastic tissues show upregulation of c-Jun N-terminal Kinase (JNK), Notch, and Janus Kinase (JAK)/Signal Transducer and Activator of Transcription (STAT) signaling. Significantly, while inhibition of JNK signaling in mutant tissues partially inhibits proliferation, inhibition of JAK/STAT signaling rescues other aspects of the neoplastic phenotype. This is the first rigorous study of tissues predominantly mutant for endocytic nTSGs and provides clear evidence for cooperation among de-regulated signaling pathways leading to tumorigenesis.

Re-splicing of mature mRNA in cancer cells promotes activation of distant weak alternative splice sites

Transcripts of the human tumor susceptibility gene 101 (TSG101) are aberrantly spliced in many cancers. A major aberrant splicing event on the TSG101 pre-mRNA involves joining of distant alternative 5′ and 3′ splice sites within exon 2 and exon 9, respectively, resulting in the extensive elimination of the mRNA. The estimated strengths of the alternative splice sites are much lower than those of authentic splice sites. We observed that the equivalent aberrant mRNA could be generated from an intron-less TSG101 gene expressed ectopically in breast cancer cells. Remarkably, we identified a pathway-specific endogenous lariat RNA consisting solely of exonic sequences, predicted to be generated by a re-splicing between exon 2 and exon 9 on the spliced mRNA. Our results provide evidence for a two-step splicing pathway in which the initial constitutive splicing removes all 14 authentic splice sites, thereby bringing the weak alternative splice sites into close proximity. We also demonstrate that aberrant multiple-exon skipping of the fragile histidine triad (FHIT) pre-mRNA in cancer cells occurs via re-splicing of spliced FHIT mRNA. The re-splicing of mature mRNA can potentially generate mutation-independent diversity in cancer transcriptomes. Conversely, a mechanism may exist in normal cells to prevent potentially deleterious mRNA re-splicing events.

A knockout of the Tsg101 gene leads to decreased expression of ErbB receptor tyrosine kinases and induction of autophagy prior to cell death

The Tumor Susceptibility Gene 101 (Tsg101) encodes a multi-domain protein that mediates a variety of molecular and biological processes including the trafficking and lysosomal degradation of cell surface receptors. Conventional and conditional knockout models have demonstrated an essential requirement of this gene for cell cycle progression and cell viability, but the consequences of a complete ablation of Tsg101 on intracellular processes have not been examined to date. In this study, we employed mouse embryonic fibroblasts that carry two Tsg101 conditional knockout alleles to investigate the expression of ErbB receptor tyrosine kinases as well as stress-induced intracellular processes that are known to be associated with a defect in growth and cell survival. The conditional deletion of the Tsg101 gene in this well-controlled experimental model resulted in a significant reduction in the steady-state levels of the EGFR and ErbB2 but a stress-induced elevation in the phosphorylation of mitogen activated protein (MAP) kinases independent of growth factor stimulation. As part of an integrated stress response, Tsg101-deficient cells exhibited extensive remodeling of actin filaments and greatly enlarged lysosomes that were enriched with the autophagy-related protein LC3. The increase in the transcriptional activation and expression of LC3 and its association with Lamp1-positive lysosomes in a PI3K-dependent manner suggest that Tsg101 knockout cells utilize autophagy as a survival mechanism prior to their ultimate death. Collectively, this study shows that a knockout of the Tsg101 gene causes complex intracellular changes associated with stress response and cell death. These multifaceted alterations need to be recognized as they have an impact on defining particular functions for Tsg101 in processes such as signal transduction and lysosomal/endosomal trafficking.

Endocytic control of growth factor signalling: multivesicular bodies as signalling organelles

Signal transduction and endocytosis are intertwined processes. The internalization of ligand-activated receptors by endocytosis has classically been thought to attenuate signals by targeting receptors for degradation in lysosomes, but it can also maintain signals in early signalling endosomes. In both cases, localization to multivesicular endosomesen route to lysosomes is thought to terminate signalling. However, during WNT signal transduction, sequestration of the enzyme glycogen synthase kinase 3 (GSK3) inside multivesicular endosomes results in the stabilization of many cytosolic proteins. Thus, the role of endocytosis during signal transduction may be more diverse than anticipated, and multivesicular endosomes may constitute a crucial signalling organelle.

Cell polarity and migration: emerging role for the endosomal sorting machinery

The endosomal sorting complex required for transport (ESCRT) machinery has been implicated in the regulation of endosomal sorting, cell division, viral budding, autophagy, and cell signaling. Here, we review recent evidence that implicates ESCRTs in cell polarity and cell migration, and discuss the potential role of ESCRTs as tumor suppressors.

Functional ESCRT machinery is required for constitutive recycling of claudin-1 and maintenance of polarity in vertebrate epithelial cells

Drosophila ESCRT mutants lose epithelial polarity and show increased proliferation, suggesting that ESCRT proteins act as tumor suppressors. In this study, we show for the first time to our knowledge that ESCRT proteins are required to maintain polarity in mammalian epithelial cells, supporting the idea that ESCRT proteins are tumor suppressors.

Genetic screens in Drosophila have identified regulators of endocytic trafficking as neoplastic tumor suppressor genes. For example, Drosophila endosomal sorting complex required for transport (ESCRT) mutants lose epithelial polarity and show increased cell proliferation, suggesting that ESCRT proteins could function as tumor suppressors. In this study, we show for the for the first time to our knowledge that ESCRT proteins are required to maintain polarity in mammalian epithelial cells. Inhibition of ESCRT function caused the tight junction protein claudin-1 to accumulate in intracellular vesicles. In contrast E-cadherin and occludin localization was unaffected. We investigated the cause of this accumulation and show that claudin-1 is constitutively recycled in kidney, colon, and lung epithelial cells, identifying claudin-1 recycling as a newly described feature of diverse epithelial cell types. This recycling requires ESCRT function, explaining the accumulation of intracellular claudin-1 when ESCRT function is inhibited. We further demonstrate that small interfering RNA knockdown of the ESCRT protein Tsg101 causes epithelial monolayers to lose their polarized organization and interferes with the establishment of a normal epithelial permeability barrier. ESCRT knockdown also reduces the formation of correctly polarized three-dimensional cysts. Thus, in mammalian epithelial cells, ESCRT function is required for claudin-1 trafficking and for epithelial cell polarity, supporting the hypothesis that ESCRT proteins function as tumor suppressors.

Identification of PEG10 and TSG101 as carcinogenesis, progression, and poor-prognosis related biomarkers for gallbladder adenocarcinoma

PEG10 is a transcriptional factor while TSG101 is involved in numerous cellular processes, including apoptotic resistance. Overexpression of PEG10 and TSG101 were observed in a variety of human cancers. However, their expression and clinical significance in gallbladder cancer (GBC) have not yet been identified. To understand the tumor biology of GBC at the molecular level, we examined PEG10 and TSG101 expression in 108 adenocarcinomas, 15 gallbladder polyps, 35 chronic cholecystitis tissues, and 46 peritumoral tissues by using immunohistochemistry. Overexpression of PEG10 and TSG101 was detected in gallbladder adenocarcinoma (48.1% and 47.2%, respectively). Conversely, there was less expression detected in the peritumoral tissues (19.6%), adenomatous polyps (13.3%), and gallbladder epithelium with chronic cholecystitis (5.1%) (p < 0.01, p < 0.05, and p < 0.01, respectively). Notably, the benign lesions with positive PEG10 and/or TSG101 expression showed moderately or severely atypical hyperplasia in gallbladder epithelium. The overexpression of PEG10 and TSG101 was significantly associated with differentiation, tumor mass, lymph node metastasis and invasion of adenocarcinoma. Univariate Kaplan-Meier analysis showed that overexpression of PEG10 (p = 0.041) and TSG101 (p = 0.025) was closely associated with decreased overall survival. Multivariate Cox regression analysis revealed that positive expression of PEG10 (p = 0.036) or TSG101 (p = 0.022) is a predictor of poor prognosis in gallbladder adenocarcinoma. Our study suggested that overexpression of PEG10 and TSG101 might be closely related to the carcinogenesis, progression, clinical biological behaviors, and prognosis of gallbladder adenocarcinoma.

TSG101, identified by screening a cancer cDNA library and soft agar assay, promotes cell proliferation in human lung cancer

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.

ESCRT proteins in physiology and disease

As a mechanism of signal attenuation, receptors for growth factors, peptide hormones and cytokines are internalized in response to ligand binding, followed by degradation in lysosomes. Receptor ubiquitination is a key signal for such downregulation, and four protein complexes known as endosomal sorting complex required for transport (ESCRT)-0, -I, -II and -III have been identified as the machinery required for degradative endosomal sorting of ubiquitinated membrane proteins in yeast and metazoans. Three of these complexes contain ubiquitin-binding domains whereas ESCRT-III instead recruits deubiquitinating enzymes. The concerted action of the ESCRTs not only serves to sort ubiquitinated cargo but is also thought to cause inward vesiculation of endosomal membranes, thereby mediating biogenesis of multivesicular endosomes (MVEs). Because ligand-mediated receptor downregulation plays an important role in signal attenuation, it is not surprising that dysfunction of ESCRT components is associated with disease. In this review we discuss the possible roles of ESCRTs in protection against cancer, neurodegenerative diseases and bacterial infections, and we highlight the fact that many RNA viruses exploit the ESCRT machinery for the final abscission step of their budding from cells. We also review the additional functions of ESCRT proteins in cytokinesis and discuss how these may be related to ESCRT-associated pathologies.

TIMP1 and SERPIN-A overexpression and TFF3 and CRABP1 underexpression as biomarkers for papillary thyroid carcinoma

BACKGROUND

No molecular pathways or specific genes are consistently associated with sporadic cases of papillary thyroid carcinoma (PTC), despite that it is the most common thyroid malignancy. Nodular goiter is an enlargement of the thyroid that is a compensatory response to a perturbation in normal thyroid homeostasis. It has been disputed in the literature that patients presenting with goiter have a higher incidence of PTC. The identification of molecular events that are common to both goiter and PTC could explain the overlap of these two disorders.

METHODS

We used high-density oligonuleotide arrays to perform molecular profiling of PTC and nodular goiter with paired normal samples.

RESULTS

Specifically, increased expression of SERPIN-A (proteinase inhibitor-alpha antitrypsin) and TIMP 1 (tissue inhibitor of metalloproteinase 1) identified these as candidate molecular biomarkers for PTC. Decreases in the CRABP1 (cellular retinoic acid binding protein 1) and TFF3 (trefoil factor 3) expression levels identified these as candidate molecular biomarkers as well. The same analysis was performed to identify genes showing specific alterations in goiter tissues.

CONCLUSIONS

This is the first report to our knowledge that compares the gene expression profiles of PTC and goiter. Our results suggest that PTC and goiter share very limited overlap in transcript expression.

Regulation of Tsg101 expression by the steadiness box: a role of Tsg101-associated ligase

As part of the endosomal sorting complex required for transport (ESCRT) machinery, Tsg101 is essential for endosomal sorting, membrane receptor degradation and the final stages of cytokinesis. Depletion or overproduction of the protein can cause disruption of these vital processes and results in severe consequences for the cell. Tsg101 expression is thus controlled posttranslationally within a narrow range and this autoregulation has been mapped to the C-terminus of the protein. Here we elucidate further the mechanisms of this regulation and describe a novel function of Tsg101-associated ligase (Tal) in mediating this control. We show that Tal polyubiquitinates lysine residues in the C-terminus of uncomplexed Tsg101, resulting in proteasomal degradation. However, accessibility to these lysines is prevented by the presence of the other ESCRT-I proteins. We show that VPS28 is a limiting factor, and consequently Tsg101 expression surplus to ESCRT-I function is vulnerable to degradation. The role of Tal in the regulation of Tsg101 steady-state control is highlighted when Tsg101 is overexpressed; however, our data also suggest that additional ligases regulate Tsg101 expression under normal conditions. Lastly, we demonstrate that while the C-terminal lysines are targets for polyubiquitination, they are not required for any additional function necessary for ESCRT activity.

Up-regulation of tumor susceptibility gene 101 conveys poor prognosis through suppression of p21 expression in ovarian cancer

PURPOSE

The function of tumor susceptibility gene 101 (TSG101) in ovarian carcinogenesis is largely unexplored. The aim of this study is to investigate the role of TSG101 in human ovarian cancer development, to examine the expression levels of TSG101 in ovarian carcinomas, and to correlate the results with clinicopathologic variables and survival.

EXPERIMENTAL DESIGN

Human ovarian cancer tissue arrays that contain duplicates of 422 cases of primary ovarian carcinoma were used to probe the expression levels of TSG101 and p21 in epithelial ovarian cancer. In vitro studies in ovarian cancer cells using TSG101-specific small interfering RNA (siRNA) were done to further elucidate the mechanism of TSG101-mediated p21 regulation.

RESULTS

We show that TSG101 is increasingly overexpressed in borderline tumors and low-grade and high-grade carcinomas. Patients with low expression of TSG101 survive longer than those with high expression. Suppressing TSG101 by siRNA in ovarian cancer cells led to growth inhibition, cell cycle arrest, and apoptosis with concurrent increases in p21 mRNA and protein. Consistent with this negative association between TSG101 and p21, expression levels of these two markers are inversely correlated in ovarian cancer.

CONCLUSIONS

TSG101 negatively regulates p21 levels, and up-regulation of TSG101 is associated with poor prognosis in ovarian cancer.

A PKC-Sp1 signaling pathway induces early differentiation of human keratinocytes through upregulation of TSG101

The TSG101 protein has been implicated in multiple biological functions including regulation of gene transcription, vesicular trafficking, cellular growth and differentiation. However, the cellular signals that control TSG101 functions are unclear. Here, we demonstrate that TSG101 is upregulated during keratinocyte differentiation in both human foreskin tissue and reconstructed organotypic skin cultures. In addition, we found that TSG101 siRNA inhibits calcium-induced early differentiation of human foreskin keratinocytes, indicating an essential and downstream role for TSG101 in this process. Furthermore, the PKC agonist TPA promotes expression of TSG101 and keratin 10 in keratinocytes under low calcium conditions, while co-treatment with the PKC inhibitor GF 109203X blocks TPA-induced TSG101 and keratin 10 upregulation. Previous work has established that the TSG101 gene is controlled by a TATA-less promoter that harbors a Sp1-binding site. Here we show that both calcium and TPA activate PKC, stimulate phosphorylation of Sp1, and augment the activity of the TSG101 promoter in a manner dependent on its Sp1-binding site. Release of calcium from intracellular stores with thapsigargin, an endoplasmic reticulum Ca2+-ATPase inhibitor that elevates intracellular free Ca2+ without activating PKC, does not affect Sp1 phosphorylation and TSG101 promoter activity. Taken together, these data suggest that an intracellular calcium store independent PKC-Sp1 signaling pathway induces early keratinocyte differentiation through upregulation of TSG101.

Tsg101 is upregulated in a subset of invasive human breast cancers and its targeted overexpression in transgenic mice reveals weak oncogenic properties for mammary cancer initiation

Previous studies reported that the Tumor Susceptibility Gene 101 (TSG101) is upregulated in selected human malignancies, and the expression of exogenous Tsg101 was suggested to transform immortalized fibroblasts in culture. To date, the potential oncogenic properties of Tsg101 have not been examined in vivo owing to the lack of appropriate model systems. In this study, we show that Tsg101 is highly expressed in a subset of invasive human breast cancers. Based on this observation, we generated the first transgenic mouse model with a targeted overexpression of Tsg101 in the developing mammary gland to test whether exogenous Tsg101 is capable of initiating tumorigenesis. Normal functionality of exogenous Tsg101 was tested by rescuing the survival of Tsg101-deficient mammary epithelial cells in conditional knockout mice. The overexpression of Tsg101 resulted in increased phosphorylation of the epidermal growth factor receptor and downstream activation of MAP kinases. Despite an increase in the activation of these signal transducers, the mammary gland of females expressing exogenous Tsg101 developed normally throughout the reproductive cycle. In aging females, the overexpression of Tsg101 seemed to increase the susceptibility of mammary epithelia toward malignant transformation. However, owing to the long latency of tumor formation and the sporadic occurrence of bona fide mammary cancers, we conclude that the Tsg101 protein has only weak oncogenic properties. Instead of cancer initiation, it is therefore likely that Tsg101 plays a more predominant role in the progression of a subset of spontaneously arising breast cancers.

Role of the TSG101 gene in Epstein-Barr virus late gene transcription

Rta, an Epstein-Barr virus (EBV)-encoded immediate-early protein, governs the reactivation of the viral lytic program by transactivating a cascade of lytic gene expression. Cellular transcription factors such as Sp1, ATF2, E2F, and Akt have been demonstrated to mediate Rta transactivation of lytic genes. We report herein that Rta associates with another potent transcription factor, tumor susceptibility gene 101 (TSG101), to promote the activation of EBV late genes. Results from an EBV cDNA array reveal that depletion of TSG101 by siRNA potently inhibits the transcription of five Rta-responsive EBV late genes, BcLF1, BDLF3, BILF2, BLLF1, and BLRF2. Depletion of TSG101 impairs the Rta transactivation of these late promoters severely. Moreover, a concordant augmentation of Rta transactivating activity is observed when TSG101 is overexpressed following ectopic transfection. Mechanistically, Rta interaction with TSG101 causes the latter to accumulate principally in the nuclei, wherein the proteins colocalize and are recruited to the viral promoters. Of note, TSG101 is crucial for the efficient binding of Rta to these late promoters. As a result, cells with defective TSG101 fail to express late viral proteins, leading to a decrease in the yield of virus particles. Thus, the contribution of TSG101 to Rta-mediated late gene activation is of great importance for completion of the EBV productive lytic cycle. These observations consolidate a role for TSG101 in the replication of EBV, a DNA virus, that differs from what is observed for RNA viruses, where TSG101 aids mainly in the endosomal sorting of enveloped late viral proteins for assembly at the plasma membrane.

Up-regulation of tumor susceptibility gene 101 protein in ovarian carcinomas revealed by proteomics analyses

Small GTPase RAS plays a critical role in cellular signaling and oncogenic transformation. Proteomics analysis of genetically defined human ovarian cancer models identified the tumor susceptibility gene 101 (TSG101) as a downstream target of RAS oncogene. Mechanistic studies revealed a novel post-translational regulation of TSG101 through the RAS/RAF/MEK/MAPK signaling pathway and downstream molecules p14(ARF)/HDM2. Immunoanalysis using ovarian cancer samples and microtissue array revealed elevated TSG101 levels in human ovarian carcinomas. Silencing of TSG101 by short interfering RNA in ovarian cancer cells led to growth inhibition and cell death. Concurrent with the apparent growth-inhibitory effect, the levels of the CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2) and hypoxia-inducible factor 1alpha (HIF-1alpha), as well as its cellular activity, were markedly reduced after TSG101 knockdown. These results demonstrate that TSG101 is important for CITED2- and HIF-1alpha-mediated cellular regulation in ovarian carcinomas.

Altered gene expression profiles by sodium/iodide symporter gene transfection in a human anaplastic thyroid carcinoma cell line using a radioactive complementary DNA microarray

BACKGROUND

The sodium/iodide symporter (NIS) is a membrane glycoprotein that mediates active 131I uptake during the treatment of cancer of the thyroid gland and extrathyroidal tissues. NIS gene transfection, a gene-therapy modality, has been introduced in many types of cancer, such as prostate cancer and breast cancer, and has demonstrated a high potential for the treatment of non-thyroidal cancers.

AIM

To investigate the pattern of NIS gene expression and provide evidence of its beneficial effects in human anaplastic cancer ARO cells by using a radioactive complementary DNA (cDNA) microarray.

METHODS

For cDNA microarray data analysis, superimposed images and clustergrams were prepared from basic radioactivity data obtained using a phosphoimager system. Gene expression profiles were constructed using the Z-transformed values of genes related to cancer biology.

RESULTS

Radioactive cDNA microarray studies showed that 11 genes were upregulated (Z ratio > 1.5) and 31 genes were downregulated (Z ratio < -1.5) in response to NIS gene transfection. Of these differentially expressed genes, 33% were related to cell proliferation and apoptosis. Moreover, NIS gene transfection into an anaplastic thyroid cancer cell line affected the expression of the protein tyrosine phosphatase (PTP) family and Ras oncogene family, including Ras, Rac and Rab.

CONCLUSION

The identification of changes in the patterns of gene expression may provide a better understanding of the response of molecular mechanisms to NIS gene transfection.