Gene Summary

Gene:TSG101; tumor susceptibility 101
Aliases: TSG10, VPS23
Summary:The protein encoded by this gene belongs to a group of apparently inactive homologs of ubiquitin-conjugating enzymes. The gene product contains a coiled-coil domain that interacts with stathmin, a cytosolic phosphoprotein implicated in tumorigenesis. The protein may play a role in cell growth and differentiation and act as a negative growth regulator. In vitro steady-state expression of this tumor susceptibility gene appears to be important for maintenance of genomic stability and cell cycle regulation. Mutations and alternative splicing in this gene occur in high frequency in breast cancer and suggest that defects occur during breast cancer tumorigenesis and/or progression. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:tumor susceptibility gene 101 protein
Source:NCBIAccessed: 27 February, 2015


What does this gene/protein do?
Show (31)
Pathways:What pathways are this gene/protein implicaed in?
Show (1)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 27 February 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Breast Cancer
  • Chromosome 11
  • Polymerase Chain Reaction
  • Mutation
  • Cancer RNA
  • Cancer Gene Expression Regulation
  • Endosomal Sorting Complexes Required for Transport
  • RNA Splicing
  • Prostate Cancer
  • Messenger RNA
  • Molecular Sequence Data
  • Transfection
  • Neoplasm Proteins
  • Cancer DNA
  • siRNA
  • Sequence Deletion
  • Gene Deletion
  • Acid Anhydride Hydrolases
  • Southern Blotting
  • Tumor Suppressor Gene
  • Base Sequence
  • Species Specificity
  • DNA-Binding Proteins
  • Lung Cancer
  • PTEN
  • DNA Mutational Analysis
  • Alternative Splicing
  • Neoplastic Cell Transformation
  • Neoplasm Invasiveness
  • Loss of Heterozygosity
  • Leucine Zippers
  • Ovarian Cancer
  • Northern Blotting
  • DNA Sequence Analysis
  • Immunohistochemistry
  • Tumor Suppressor Proteins
  • Phosphoric Monoester Hydrolases
  • Proteins
Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: TSG101 (cancer-related)

Liu T, Mendes DE, Berkman CE
Functional prostate-specific membrane antigen is enriched in exosomes from prostate cancer cells.
Int J Oncol. 2014; 44(3):918-22 [PubMed] Free Access to Full Article Related Publications
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.

Hoffmann J, Boehm C, Himmelsbach K, et al.
Identification of α-taxilin as an essential factor for the life cycle of hepatitis B virus.
J Hepatol. 2013; 59(5):934-41 [PubMed] Related Publications
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.

Jiang Y, Ou Y, Cheng X
Role of TSG101 in cancer.
Front Biosci (Landmark Ed). 2013; 18:279-88 [PubMed] Related Publications
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.

Hsu SF, Goan YG, Tsai HY, et al.
An upstream regulatory element confers orientation-independent enhancement of the TSG101 promoter activity in transformed cells.
Mol Biol Rep. 2012; 39(1):517-25 [PubMed] Related Publications
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.

Wierinckx A, Roche M, Raverot G, et al.
Integrated genomic profiling identifies loss of chromosome 11p impacting transcriptomic activity in aggressive pituitary PRL tumors.
Brain Pathol. 2011; 21(5):533-43 [PubMed] Related Publications
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.

Zhang Y, Song M, Cui ZS, et al.
Down-regulation of TSG101 by small interfering RNA inhibits the proliferation of breast cancer cells through the MAPK/ERK signal pathway.
Histol Histopathol. 2011; 26(1):87-94 [PubMed] Related Publications
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.

Broniarczyk J, Olejnik-Schmidt AK, Luczak MW, et al.
Analysis of expression and structure of the TSG101 gene in cervical cancer cells.
Int J Mol Med. 2010; 25(5):777-83 [PubMed] Related Publications
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.

Liu F, Yu Y, Jin Y, Fu S
TSG101, identified by screening a cancer cDNA library and soft agar assay, promotes cell proliferation in human lung cancer.
Mol Biol Rep. 2010; 37(6):2829-38 [PubMed] Related Publications
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.

Guescini M, Genedani S, Stocchi V, Agnati LF
Astrocytes and Glioblastoma cells release exosomes carrying mtDNA.
J Neural Transm. 2010; 117(1):1-4 [PubMed] Related Publications
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.

Herz HM, Bergmann A
Genetic analysis of ESCRT function in Drosophila: a tumour model for human Tsg101.
Biochem Soc Trans. 2009; 37(Pt 1):204-7 [PubMed] Related Publications
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.

Ma XR, Edmund Sim UH, Pauline B, et al.
Overexpression of WNT2 and TSG101 genes in colorectal carcinoma.
Trop Biomed. 2008; 25(1):46-57 [PubMed] Related Publications
Colorectal carcinoma (CRC) arises as a result of mutational activation of oncogenes coupled with inactivation of tumour suppressor genes. Mutations in APC, K-ras and p53 have been commonly reported. In a previous study by our group, the tumour susceptibility gene 101 (TSG101) were found to be persistently upregulated in CRC cases. TSG101 was reported to be closely related to cancers of the breast, brain and colon, and its overexpression in human papillary thyroid carcinomas and ovarian carcinomas had previously been reported. The wingless-type MMTV integration site family member 2 (WNT2) is potentially important in the Wnt/beta-catenin pathway and upregulation of WNT2 is not uncommon in human cancers. In this study, we report the investigation for mutation(s) and expression pattern(s) of WNT2 and TSG101, in an effort to further understand their role(s) in CRC tumourigenesis. Our results revealed no mutation in these genes, despite their persistent upregulation in CRC cases studied.

Tanaka N, Kyuuma M, Sugamura K
Endosomal sorting complex required for transport proteins in cancer pathogenesis, vesicular transport, and non-endosomal functions.
Cancer Sci. 2008; 99(7):1293-303 [PubMed] Related Publications
Endosomal sorting complex required for transport (ESCRT) proteins form a multicomplex sorting machinery that controls multivesicular body (MVB) formation and the sorting of ubiquitinated membrane proteins to the endosomes. Being sorted to the MVB generally results in the lysosome-dependent degradation of cell-surface receptors, and defects in this machinery induce dysregulated receptor traffic and turnover. Recent lessons from gene targeting and silencing methodologies have implicated the ESCRT in normal development, cell differentiation, and growth, as well as in the budding of certain enveloped viruses. Furthermore, it is becoming apparent that the dysregulation of ESCRT proteins is involved in the development of various human diseases, including many types of cancers and neurodegenerative disorders. Here, we summarize the roles of ESCRT proteins in MVB sorting processes and the regulation of tumor cells, and we discuss some of their other functions that are unrelated to vesicular transport.

Young TW, Rosen DG, Mei FC, et al.
Up-regulation of tumor susceptibility gene 101 conveys poor prognosis through suppression of p21 expression in ovarian cancer.
Clin Cancer Res. 2007; 13(13):3848-54 [PubMed] Related Publications
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.

Oh KB, Stanton MJ, West WW, et al.
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.
Oncogene. 2007; 26(40):5950-9 [PubMed] Related Publications
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.

Chua HH, Lee HH, Chang SS, et al.
Role of the TSG101 gene in Epstein-Barr virus late gene transcription.
J Virol. 2007; 81(5):2459-71 [PubMed] Free Access to Full Article Related Publications
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.

Young TW, Mei FC, Rosen DG, et al.
Up-regulation of tumor susceptibility gene 101 protein in ovarian carcinomas revealed by proteomics analyses.
Mol Cell Proteomics. 2007; 6(2):294-304 [PubMed] Related Publications
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.

Surjit M, Oberoi R, Kumar R, Lal SK
Enhanced alpha1 microglobulin secretion from Hepatitis E virus ORF3-expressing human hepatoma cells is mediated by the tumor susceptibility gene 101.
J Biol Chem. 2006; 281(12):8135-42 [PubMed] Related Publications
Viruses are known to exploit the host cell machinery for their benefit during different stages of their life cycle within the infected host. One of the major challenges for a virus during the early stages of infection is to escape recognition by the host immune system. Viruses have adopted many novel strategies to evade the host immune response or to create an immune suppressed environment. An earlier study in our laboratory has demonstrated that the ORF3 protein of the hepatitis E virus expedites the secretion of alpha1 microglobulin, an immunosuppressant molecule. Based on this observation, we proposed that enhanced secretion of alpha1 microglobulin may help maintain an immunosuppressed milieu around the infected hepatocyte (Tyagi, S., Surjit, M., Roy, A. K., Jameel, S., and Lal, S. K. (2004) J. Biol. Chem. 279, 29308-29319). In the present study, we discovered that the ability of the ORF3 protein to expedite alpha1 microglobulin secretion is attributed to the PSAP motif present at the C terminus of the former. The ORF3 protein was able to associate with the tumor susceptibility gene 101 (TSG101) through the PSAP motif. Further, a PSAP motif-mutated ORF3 protein was unable to associate with TSG101 and also lost its ability to enhance the secretion of alpha1 microglobulin. In addition, the ORF3 protein was found to associate simultaneously with TSG101 and alpha1 microglobulin because all three of them were co-precipitated as a ternary complex. Finally, a dominant negative mutant of the VPS4 protein was shown to block the enhanced alpha1 microglobulin secretion in ORF3-expressing hepatocytes. These results suggest a mechanism by which the ORF3 protein exploits the endosomal sorting machinery to enhance the secretion of an immunosuppressant molecule (alpha1 microglobulin) from the cultured hepatocytes.

Sakai M, Shimokawa T, Kobayashi T, et al.
Elevated expression of C10orf3 (chromosome 10 open reading frame 3) is involved in the growth of human colon tumor.
Oncogene. 2006; 25(3):480-6 [PubMed] Related Publications
After analysing gene-expression profiles of colon cancers on a cDNA microarray containing cDNAs corresponding to 23 040 human genes, we focused on a gene annotated as C10orf3 (chromosome 10 open reading frame 3), whose expression was elevated in colorectal cancers (CRC) as well as in tumors arising in the stomach, lung, pancreas, and breast. The gene encodes a putative 464-amino-acid protein containing a domain known as AAA (ATPases associated with a variety of cellular activities). Western blot analysis using an antibody to the gene product confirmed that the protein was overexpressed in nine of the 15 clinical cancer tissues examined, compared to corresponding noncancerous epithelial cells. A subsequent proteomics analysis revealed that C10orf3 product associated with the product of tumor susceptibility gene 101 (TSG101), and that C10orf3 downregulated TSG101 in a post-transcriptional manner. Expression of short interfering RNA in cells derived from CRC caused significant decreases in C10orf3 expression and inhibited growth of the transfected cells, which was associated with increased apoptotic cells. These data suggest that elevated C10orf3 expression might play an essential role in the growth of cancer cells, and that suppression of C10orf3-mediated signal transduction may be a novel therapeutic strategy to a wide range of human tumors.

Agou F, Courtois G, Chiaravalli J, et al.
Inhibition of NF-kappa B activation by peptides targeting NF-kappa B essential modulator (nemo) oligomerization.
J Biol Chem. 2004; 279(52):54248-57 [PubMed] Related Publications
NF-kappa B essential modulator/IKK-gamma (NEMO/IKK-gamma) plays a key role in the activation of the NF-kappa B pathway in response to proinflammatory stimuli. Previous studies suggested that the signal-dependent activation of the IKK complex involves the trimerization of NEMO. The minimal oligomerization domain of this protein consists of two coiled-coil subdomains named Coiled-coil 2 (CC2) and leucine zipper (LZ) (Agou, F., Traincard, F., Vinolo, E., Courtois, G., Yamaoka, S., Israel, A., and Veron, M. (2004) J. Biol. Chem. 279, 27861-27869). To search for drugs inhibiting NF-kappa B activation, we have rationally designed cell-permeable peptides corresponding to the CC2 and LZ subdomains that mimic the contact areas between NEMO subunits. The peptides were tagged with the Antennapedia/Penetratin motif and delivered to cells prior to stimulation with lipopolysaccharide. Peptide transduction was monitored by fluorescence-activated cell sorter, and their effect on lipopolysaccharide-induced NF-kappa B activation was quantified using an NF-kappa B-dependent beta-galactosidase assay in stably transfected pre-B 70Z/3 lymphocytes. We show that the peptides corresponding to the LZ and CC2 subdomains inhibit NF-kappa B activation with an IC(50) in the mum range. Control peptides, including mutated CC2 and LZ peptides and a heterologous coiled-coil peptide, had no inhibitory effect. The designed peptides are able to induce cell death in human retinoblastoma Y79 cells exhibiting constitutive NF-kappa B activity. Our results provide the "proof of concept" for a new and promising strategy for the inhibition of NF-kappa B pathway activation through targeting the oligomerization state of the NEMO protein.

Zhu G, Gilchrist R, Borley N, et al.
Reduction of TSG101 protein has a negative impact on tumor cell growth.
Int J Cancer. 2004; 109(4):541-7 [PubMed] Related Publications
TSG101 was defined originally as a tumor-suppressor gene, raising the expectation that absence of the encoded protein should lead to increased tumor cell growth and, perhaps, increased tumor cell aggressiveness. We have used the RNA interference (RNAi) technique to downregulate TSG101 in PC3 (prostate cancer) and MDA-MB-231 (breast cancer) cells. An approximately 85% selective downregulation at the protein level was achieved in both cell lines over a period of 12 days as detected by Western blotting. This treatment resulted in inhibition of tumor cell growth, with a decreased level of TSG101 causing partial cell cycle arrest at the G(1)/S boundary and a reduction in the rate at which cells passed from G(2) through mitosis and back into G(1). In both cell lines, the percentage of cells in S-phase was reduced significantly at day 4 after the TSG101 siRNA transfection (27% vs. 41% in MDA-MB-231 cells; 22% vs. 39% in PC3 cells). Additionally, RNAi-mediated downregulation of TSG101 reduced the colony formation capacities of both cancer cell lines. Rather more surprisingly, TSG101 downregulation affected the migratory activity of the MDA-MB-231 cells, independent of any effect on proliferation. Thus, in a Transwell assay, after 4-hr incubation, 36.0% of control MDA-MB-231 cells had migrated to the lower chamber vs. 7.3% of TSG101-downregulated cells (p < 0.001; scrambled control, 36.5%). These results show that the TSG101 gene does not comply with the usual characteristics of a tumor-suppressor gene; rather, its expression may be necessary for activities associated with aspects of tumor progression.

Koon N, Schneider-Stock R, Sarlomo-Rikala M, et al.
Molecular targets for tumour progression in gastrointestinal stromal tumours.
Gut. 2004; 53(2):235-40 [PubMed] Free Access to Full Article Related Publications
BACKGROUND AND AIMS: The distinction between benign and malignant gastrointestinal stromal tumours (GISTs) is often unclear at the clinical and histopathology levels. GISTs are believed to arise from the stem cells of Cajal. In order to define genetic biomarkers and identify target genes related to GIST progression, we analysed and compared benign and malignant GISTs with verified follow up data using cDNA expression arrays.
METHODS: Eight genes were frequently overexpressed in malignant GISTs and their overexpression was confirmed using quantitative real time reverse transcription-polymerase chain reaction. These genes included ezrin (villin 2 (VIL2)), collagen 8 alpha 1 subunit (COL8A1), G2/mitotic specific cyclin B1 (CCNB1), high mobility group protein (HMG2), TSG101 tumour susceptibility protein, CENP-F kinetochore protein, protein tyrosine kinase 2 (FAK), and protein kinase DYRK2. To test these genes in a clinical setting, we obtained diagnostic samples of 16 additional GISTs that were classified at diagnosis as benign, malignant, and uncertain malignant potential (UMP).
RESULTS: There was remarkable gene overexpression in all malignant GISTs. Statistical analyses revealed significant correlations between overexpression of several gene pairs in malignant GISTs. We found the strongest correlations (rho>0.70) among the significant correlations (p<0.01) between CCNB1-CENP-F (rho = 0.87) and CCNB1-FAK (rho = 0.73). Gene expression of the UMP GISTs suggested two different groups. Three UMP GISTs had gene expression consistent with malignant tumours and their follow up data revealed that indeed these patients had recurrences later on. On the other hand, UMP GISTs that had low gene expression levels continued free of disease for several years.
CONCLUSIONS: These results provide insight into the oncogenesis of GISTs and suggest that testing the expression profile of a number of genes may segregate GISTs into groups of different tumour behaviour.

Zhu G, Reynolds L, Crnogorac-Jurcevic T, et al.
Combination of microdissection and microarray analysis to identify gene expression changes between differentially located tumour cells in breast cancer.
Oncogene. 2003; 22(24):3742-8 [PubMed] Related Publications
Comparison of gene expression changes between cancer cells at the periphery and in the centre of breast cancers was performed using a combination of microdissection and microarray analysis. Cancer cells from the two areas were pooled separately from five patients with ductal carcinoma in situ and separately from five patients with frankly invasive cancer. Limited total RNA, 100-200 ng, from this microdissected tissue required use of the Atlas SMART trade mark Probe Amplification Kit to synthesize and amplify cDNA and make (33)P-labelled probes. Probes were then hybridized to Atlas Human Cancer 1.2 Arrays containing 1176 known genes. Triplicate analysis revealed that 22 genes changed their expression levels in the periphery relative to the central region: 15 upregulated and seven downregulated (arbitrary threshold of 1.5-fold or greater). Differences in RNA levels were confirmed by quantitative real-time PCR for two of the genes and by changes in protein levels, detected by immunohistochemistry, for a couple of representative gene products. Thus, changes in gene expression associated with variation in microanatomical location of neoplastic cells can be detected within even small developing tumour masses.

Balz V, Prisack HB, Bier H, Bojar H
Analysis of BRCA1, TP53, and TSG101 germline mutations in German breast and/or ovarian cancer families.
Cancer Genet Cytogenet. 2002; 138(2):120-7 [PubMed] Related Publications
About 5%-10% of breast cancers are considered to be hereditary and associated with germline mutations of specific genes. As yet, the most frequently affected genes identified are BRCA1 and BRCA2, but also other genes such as TP53 are supposed to influence the predisposition toward breast cancer. In the present study, we analyzed patients of 19 German families with early onset breast cancer and/or a family history of breast and/or ovarian cancer for the presence of mutations in BRCA1 and TP53. In addition, we screened for germline mutations in the putative tumor suppressor gene TSG101. For this purpose we used direct sequence analysis of the entire coding regions for all three genes and, in the case of BRCA1, single-strand conformation polymorphism analysis and protein transcription-translation assays. We identified eight previously described polymorphisms and several aberrations in BRCA1: 1 unclassified missense mutation, 3 small protein truncating mutations, 1 novel pseudoexon, and 5 splicing variants. No mutation was detected in TP53. Analysis of TSG101 transcripts revealed an aberrant transcript in two breast cancer patients belonging to the same family, suggesting TSG101 as a predisposing gene in hereditary breast cancer.

Liu RT, Huang CC, You HL, et al.
Overexpression of tumor susceptibility gene TSG101 in human papillary thyroid carcinomas.
Oncogene. 2002; 21(31):4830-7 [PubMed] Related Publications
Functional inactivation of tumor susceptibility gene tsg101 leads to cellular transformation and tumorigenesis in mice. While human TSG101 is located in a region where frequent loss of heterozygosity can be detected in a variety of cancers, no genomic deletion in TSG101 gene has been reported, casting a doubt on the role of TSG101 as a classical tumor suppressor. Some studies have revealed that TSG101 is a frequent target of splicing defects, which correlate with cellular stress and p53 status. Furthermore, recent reports have identified TSG101 as a part of the MDM2/p53 regulatory circuitry, a well-recognized circuitry that upon deregulation results in tumorigenesis. Interestingly, overexpression of tsg101 from an adventitious promoter also leads to neoplastic transformation. On the basis of this information, we have analysed TSG101 gene expression in 20 human papillary thyroid carcinomas (PTCs) by immunohistochemistry and demonstrated that the overexpression of TSG101 protein is closely associated with human PTCs. Further sequence analysis reveals no mutation in cDNA region encoding steadiness box in these PTC specimens, indicating that the upregulation of TSG101 protein is not caused by the alteration of this region. In situ hybridization analysis confirms that overexpression of TSG101 also occurs at the transcriptional level. In addition, semi-quantitative RT-PCR and subsequent Southern hybridization verify that the amounts of TSG101 transcripts are indeed lower in three normal thyroid tissues than in PTC specimens. Here we report the upregulation of TSG101 expression in PTC cells, providing the first evidence of the association of TSG101 overexpression with human tumors and suggesting that upregulation of TSG101 steady-state level might play a role in mediating tumorigenesis of human PTC.

Bennett NA, Pattillo RA, Lin RS, et al.
TSG101 expression in gynecological tumors: relationship to cyclin D1, cyclin E, p53 and p16 proteins.
Cell Mol Biol (Noisy-le-grand). 2001; 47(7):1187-93 [PubMed] Related Publications
Recent studies have shown that in vitro steady-state expression of the tumor susceptibility gene TSG101 is important for maintenance of genomic stability and cell cycle regulation. To determine the contribution of TSG101 expression in neoplastic formation, expression of TSG101 protein levels were evaluated in primary ovarian and endometrial adenocarcinoma tumors. Expression of TSG101 was also examined in various tumor cell lines (PA-1, AN3CA, HeLa, HS578T, HCT116). Full-length TSG101 protein was detected in these tumors and cell lines indicating that intragenic deletions were not characteristic of TSG101. In addition, TSG101 protein levels were compared with aberrations of prominent cell cycle regulatory molecules such as cyclin D1, cyclin E, p16 and p53. Reduced TSG101 protein was observed in 36% (8/22) of ovarian and 17% (1/6) of endometrial adenocarcinoma. Aberrant levels of p53, p16, cyclin D or E were comparable to published studies indicating that the clinicopathological distribution of these cases did not favor advanced stage tumors. Altogether, these findings suggest that a down-regulation of TSG101 is associated with tumorigenesis in a subgroup of gynecological tumors.

Lo YF, Chen TC, Chen SC, Chao CC
Aberrant expression of TSG101 in Taiwan Chinese breast cancer.
Breast Cancer Res Treat. 2000; 60(3):259-66 [PubMed] Related Publications
Functional inactivation of the tsg101 gene in mouse fibroblasts results in cell transformation and the ability to form metastatic tumors in nude mice. The human tsg101 gene was mapped to chromosome 11q15.1-2 and found to mutate in some cancer patients. To test the expression pattern of the tsg 101 gene in Chinese breast cancer patients, we analyzed the mRNA by RT-PCR in 51 breast cancer patients. The full-length tsg101 and 7 truncated transcripts were detected in both normal and matched tumor tissues. A short transcript with a deletion of nucleotides 154-1054 is frequently presented in late-stage breast cancers. TSG101 protein expression was also detected by Western blot analysis in 30 breast cancer patients. A predicted full-length 46 kDa and three proteins with smaller molecular weight were detected. The full-length 46 kDa protein was less expressed in tumor specimens. Immunohistochemical stains from 10 patients of each stage 0-4 revealed that TSG101 protein was predominantly present in the cytoplasm. Cell nuclei were occasionally immunopositive and the chromosomes were deeply stained during cell division. The intracellular location and the expression of TSG101 protein were both not stage-dependent in primary breast cancers. In addition, normal mammary glands were more homogenously immunopositive than invasive ductal carcinoma. These results support the notion that the aberrant expression of TSG101 in breast cancer is associated with altered cell growth.

McIver B, Grebe SK, Wang L, et al.
FHIT and TSG101 in thyroid tumours: aberrant transcripts reflect rare abnormal RNA processing events of uncertain pathogenetic or clinical significance.
Clin Endocrinol (Oxf). 2000; 52(6):749-57 [PubMed] Related Publications
OBJECTIVE: The chromosomal regions containing the two putative tumour suppressors, fragile histidine triad gene (FHIT) and tumour suppressor gene 101 (TSG101), are deleted frequently in thyroid tumours. We therefore analysed FHIT and TSG101 transcripts in a group of advanced thyroid tumours to establish their role in thyroid tumorigenesis.
DESIGN: Retrospective analysis of FHIT and TSG101 mRNA transcripts and genomic DNA from cryo-preserved thyroid tumours. TP53, previously shown at the genomic level not to be mutated in this cohort of tumours, served as a control.
PATIENTS: We analysed nine follicular thyroid carcinomas (FTC), six papillary thyroid carcinomas and six follicular adenomas (FA) and histologically normal thyroid tissue from four of the FA patients.
MEASUREMENTS: Single stage and nested reverse transcription polymerase chain reaction (RT-PCR) products of FHIT, TSG101, and TP53 were analysed by agarose or polyacrylamide gel electrophoresis and sequenced. Genomic DNA was also analysed by polymerase chain reaction and sequencing (FHIT) or by Southern blotting (TSG101). Clinical data were correlated with the results of the mutation analysis.
RESULTS: Truncated FHIT transcripts were observed frequently alongside full length transcripts with nested RT-PCR, most often in FTC, while single stage RT-PCR revealed only normal length transcripts in all tumours. Similar results were obtained for TP53, while abnormal TSG101 transcripts were detectable by single stage RT-PCR. Sequence analysis of the truncated FHIT and TSG101 transcripts revealed mainly exon skipping and alternate RNA processing events. Only a single point mutation (of TSG101) was found. Southern blotting for the TSG101 gene, and PCR amplification and sequencing of the FHIT gene showed no evidence of genomic abnormalities in either case, and there was no evidence of splice site mutations in the FHIT gene, suggesting that the truncated transcripts result from altered RNA processing. There was no relationship between tumour stage, grade or survival and the presence of FHIT or TSG101 abnormalities.
CONCLUSIONS: Truncated FHIT and TSG101 transcripts in thyroid tumours reflect alternate mRNA splicing events, rather than genomic deletions. Such abnormal RNA processing seems to be common and widespread in thyroid neoplasms, as similar results were obtained by analysis of transcripts of TP53, which we had previously shown not to be mutated in these specimens. Although a pathogenetic role for these aberrant transcripts remains possible, no correlation was found with stage, histological grade or outcome in this small group of advanced thyroid malignancies. Relaxation of mRNA splice control appears to be a feature of follicular cell-derived thyroid neoplasms.

Lin SF, Lin PM, Liu TC, et al.
Clinical implications of aberrant TSG101 transcripts in acute myeloblastic leukemia.
Leuk Lymphoma. 2000; 36(5-6):463-6 [PubMed] Related Publications
Tsg101 is a mouse tumor suppressor gene whose homozygous deletion produces transformation of NIH3T3 cells and leads to metastases in nude mice. The human homologue of the gene, TSG101, is localized in chromosome 11p15.1-p15.2. Reduced TSG101 expression may cause the defect of the cell cycle checkpoint that leads to genetic instability and consequently to the progression of neoplasia. Aberrant TSG101 transcript have been identified in many types of cancers, and the relaxation of RNA splicing fidelity may be an onco-developmental marker in cancers and could play a general role in tumorigenesis. In our previous study, smaller TSG101 transcripts were found in AML specimens, hematopoietic cell lines and normal controls. The aberrant transcripts occurred more frequently in the AML cases and cell lines. The patients with aberrant TSG101 transcripts had higher initial white cell count, lower LDH level, and lower complete remission rate after induction chemotherapy. However, further multivariate analysis of clinical data revealed that there was no relationship to the TSG101 aberrant transcripts. The clinical significance of TSG101 aberrant transcript in AML needs further evaluation.

Liu TC, Lin PM, Chang JG, et al.
Mutation analysis of PTEN/MMAC1 in acute myeloid leukemia.
Am J Hematol. 2000; 63(4):170-5 [PubMed] Related Publications
Recently, a putative tumor suppressor gene, PTEN/MMAC1, has been identified at chromosome 10q23.3, which encodes a 403 amino acid dual-specificity phosphatase containing a region of homology to tensin and auxillin. Somatic mutations of the PTEN/MMAC1 gene have been identified in a number of cancer cell lines and primary cancers. Mutations in PTEN/MMAC1 are most frequently found in advanced cancers. To evaluate the role of the PTEN/MMAC1 gene in leukemia, bone marrow and/or peripheral blood from 62 acute myeloid leukemia (AML) patients, 5 hemopoietic cell lines (HL60, U937, Raji, KG-1, K562), and 30 normal controls were analyzed. The results showed aberrant PTEN/MMAC1 transcripts in 15 of the 62 (24%) AML patients, 4 of the 5 cell lines (80%), and 4 of the 30 (13%) normal controls. As in our previous study of TSG101, the abnormal transcripts may result from aberrant RNA splicing as evidenced by the presence of both these aberrant transcripts and normal full length transcripts in all specimens examined. Loss of heterozygosity (LOH) analysis and PCR-SSCP of the entire coding region showed that none of the AML cases had LOH or mutation. Only one frameshift mutation at codon 130 (insertion of CCCG) with premature termination of coding sequence was observed in the U937 cell line. Our results indicate that the PTEN/MMAC1 gene may play a role in a small percentage of AML, but its significance needs to be further evaluated.

Yeh KT, Chang JG, Chen YJ, et al.
Mutation analysis of the putative tumor suppressor gene PTEN/MMAC1 in hepatocellular carcinoma.
Cancer Invest. 2000; 18(2):123-9 [PubMed] Related Publications
Loss of heterozygosity of chromosome 10q has been reported in hepatoma. Areas with a high rate of loss of genetic material could harbor putative tumor suppressor genes. PTEN/MMAC1, a candidate tumor suppressor gene located at chromosome 10q23.3, has recently been identified and found to be homozygously deleted or mutated in several different types of human tumors. To determine whether the PTEN/MMAC1 gene is a target of 10q loss of heterozygosity in hepatoma, we examined 42 primary hepatomas for mutations in PTEN/MMAC1 by using nested reverse transcriptase polymerase chain reaction (RT-PCR) of the RNA and single-stranded conformation polymorphism (SSCP) analysis of all genomic exons. Although 2 of 42 hepatoma tissues had aberrant transcripts, 5 matched noncancerous liver tissues also had aberrant transcripts. Southern blot analysis of the entire genomic DNA revealed no genomic change. Therefore, like the TSG101 or FHIT gene, aberrant transcripts of PTEN/MMAC1 using the nested RT-PCR method were a common phenomenon for both cancerous and noncancerous liver tissues, which may not be related to oncogenesis. None of the 42 cases had small deletions, point mutations, or insertions. Our results suggest that the PTEN/MMAC1 gene may not play a role in the pathogenesis of hepatoma.

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