All Publications

  • Gold Nanoclusters for NIR-II Fluorescence Imaging of Bones. Small (Weinheim an der Bergstrasse, Germany) Li, D., Liu, Q., Qi, Q., Shi, H., Hsu, E. C., Chen, W., Yuan, W., Wu, Y., Lin, S., Zeng, Y., Xiao, Z., Xu, L., Zhang, Y., Stoyanova, T., Jia, W., Cheng, Z. 2020: e2003851


    Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for deep tissue visualization. Development of novel clinical translatable NIR-II probes is crucial for realizing the medical applications of NIR-II fluorescence imaging. Herein, the glutathione-capped gold nanoclusters (AuNCs, specifically Au25 (SG)18 ) demonstrate highly efficient binding capability to hydroxyapatite in vitro for the first time. Further in vivo NIR-II fluorescence imaging of AuNCs indicate that they accumulate in bone tissues with high contrast and signal-background ratio. AuNCs are also mainly and quickly excreted from body through renal system, showing excellent ribs and thoracic vertebra imaging because of no background signal in liver and spleen. The deep tissue penetration capability and high resolution of AuNCs in NIR-II imaging render their great potential for fluorescence-guided surgery like spinal pedicle screw implantation. Overall, AuNCs are highly promising and clinical translatable NIR-II imaging probe for visualizing bone and bone related abnormalities.

    View details for DOI 10.1002/smll.202003851

    View details for PubMedID 33000882

  • Trop2 is a driver of metastatic prostate cancer with neuroendocrine phenotype via PARP1. Proceedings of the National Academy of Sciences of the United States of America Hsu, E. C., Rice, M. A., Bermudez, A., Marques, F. J., Aslan, M., Liu, S., Ghoochani, A., Zhang, C. A., Chen, Y. S., Zlitni, A., Kumar, S., Nolley, R., Habte, F., Shen, M., Koul, K., Peehl, D. M., Zoubeidi, A., Gambhir, S. S., Kunder, C. A., Pitteri, S. J., Brooks, J. D., Stoyanova, T. 2020


    Resistance to androgen deprivation therapy, or castration-resistant prostate cancer (CRPC), is often accompanied by metastasis and is currently the ultimate cause of prostate cancer-associated deaths in men. Recently, secondary hormonal therapies have led to an increase of neuroendocrine prostate cancer (NEPC), a highly aggressive variant of CRPC. Here, we identify that high levels of cell surface receptor Trop2 are predictive of recurrence of localized prostate cancer. Moreover, Trop2 is significantly elevated in CRPC and NEPC, drives prostate cancer growth, and induces neuroendocrine phenotype. Overexpression of Trop2 induces tumor growth and metastasis while loss of Trop2 suppresses these abilities in vivo. Trop2-driven NEPC displays a significant up-regulation of PARP1, and PARP inhibitors significantly delay tumor growth and metastatic colonization and reverse neuroendocrine features in Trop2-driven NEPC. Our findings establish Trop2 as a driver and therapeutic target for metastatic prostate cancer with neuroendocrine phenotype and suggest that high Trop2 levels could identify cancers that are sensitive to Trop2-targeting therapies and PARP1 inhibition.

    View details for DOI 10.1073/pnas.1905384117

    View details for PubMedID 31932422

  • Loss of Notch1 Activity Inhibits Prostate Cancer Growth and Metastasis and Sensitizes Prostate Cancer Cells to Antiandrogen Therapies MOLECULAR CANCER THERAPEUTICS Rice, M. A., Hsu, E., Aslan, M., Ghoochani, A., Su, A., Stoyanova, T. 2019; 18 (7): 1230?42
  • PSPC1-interchanged interactions with PTK6 and ?-catenin synergize oncogenic subcellular translocations and tumor progression. Nature communications Lang, Y. D., Chen, H. Y., Ho, C. M., Shih, J. H., Hsu, E. C., Shen, R., Lee, Y. C., Chen, J. W., Wu, C. Y., Yeh, H. W., Chen, R. H., Jou, Y. S. 2019; 10 (1): 5716


    Hepatocellular carcinoma (HCC) is one of the most lethal cancers worldwide due to metastasis. Paraspeckle component 1 (PSPC1) upregulation has been identified as an HCC pro-metastatic activator associated with poor patient prognosis, but with a lack of targeting strategy. Here, we report that PSPC1, a nuclear substrate of PTK6, sequesters PTK6 in the nucleus and loses its metastasis driving capability. Conversely, PSPC1 upregulation or PSPC1-Y523F mutation promotes epithelial-mesenchymal transition, stemness, and metastasis via cytoplasmic translocation of active PTK6 and nuclear translocation of ?-catenin, which interacts with PSPC1 to augment Wnt3a autocrine signaling. The aberrant nucleocytoplasmic shuttling of active PTK6/?-catenin is reversed by expressing the PSPC1 C-terminal interacting domain (PSPC1-CT131), thereby suppressing PSPC1/PTK6/?-catenin-activated metastasis to prolong the survival of HCC orthotopic mice. Thus, PSPC1 is the contextual determinant of the oncogenic switch of PTK6/?-catenin subcellular localizations, and PSPC1-CT131 functions as a dual inhibitor of PSPC1 and PTK6 with potential for improving cancer therapy.

    View details for DOI 10.1038/s41467-019-13665-6

    View details for PubMedID 31844057

    View details for PubMedCentralID PMC6914800

  • Defining new drivers of castration- resistant prostate cancer Hsu, E., Rice, M., Nolley, R., Bermudez, A., Huang, J., Peehl, D., Kunder, C., Pitteri, S., Brooks, J., Stoyanova, T. AMER ASSOC CANCER RESEARCH. 2018: 90
  • PSPC1 mediates TGF-?1 autocrine signalling and Smad2/3 target switching to promote EMT, stemness and metastasis. Nature cell biology Yeh, H. W., Hsu, E. C., Lee, S. S., Lang, Y. D., Lin, Y. C., Chang, C. Y., Lee, S. Y., Gu, D. L., Shih, J. H., Ho, C. M., Chen, C. F., Chen, C. T., Tu, P. H., Cheng, C. F., Chen, R. H., Yang, R. B., Jou, Y. S. 2018; 20 (4): 479?91


    Activation of metastatic reprogramming is critical for tumour metastasis. However, more detailed knowledge of the underlying mechanism is needed to enable targeted intervention. Here, we show that paraspeckle component 1 (PSPC1), identified in an aberrant 13q12.11 locus, is upregulated and associated with poor survival in patients with cancer. PSPC1 promotes tumorigenesis, epithelial-to-mesenchymal transition (EMT), stemness and metastasis in multiple cell types and in spontaneous mouse cancer models. PSPC1 is the master activator for transcription factors of EMT and stemness and accompanies c-Myc activation to facilitate tumour growth. PSPC1 increases transforming growth factor-?1 (TGF-?1) secretion through an interaction with phosphorylated and nuclear Smad2/3 to potentiate TGF-?1 autocrine signalling. Moreover, PSPC1 acts as a contextual determinant of the TGF-?1 pro-metastatic switch to alter Smad2/3 binding preference from tumour-suppressor to pro-metastatic genes. Having validated the PSPC1-Smads-TGF-?1 axis in various cancers, we conclude that PSPC1 is a master activator of pro-metastatic switches and a potential target for anti-metastasis drugs.

    View details for DOI 10.1038/s41556-018-0062-y

    View details for PubMedID 29593326

  • The Exosome Total Isolation Chip. ACS nano Liu, F., Vermesh, O., Mani, V., Ge, T. J., Madsen, S. J., Sabour, A., Hsu, E. C., Gowrishankar, G., Kanada, M., Jokerst, J. V., Sierra, R. G., Chang, E., Lau, K., Sridhar, K., Bermudez, A., Pitteri, S. J., Stoyanova, T., Sinclair, R., Nair, V. S., Gambhir, S. S., Demirci, U. 2017


    Circulating tumor-derived extracellular vesicles (EVs) have emerged as a promising source for identifying cancer biomarkers for early cancer detection. However, the clinical utility of EVs has thus far been limited by the fact that most EV isolation methods are tedious, nonstandardized, and require bulky instrumentation such as ultracentrifugation (UC). Here, we report a size-based EV isolation tool called ExoTIC (exosome total isolation chip), which is simple, easy-to-use, modular, and facilitates high-yield and high-purity EV isolation from biofluids. ExoTIC achieves an EV yield ?4-1000-fold higher than that with UC, and EV-derived protein and microRNA levels are well-correlated between the two methods. Moreover, we demonstrate that ExoTIC is a modular platform that can sort a heterogeneous population of cancer cell line EVs based on size. Further, we utilize ExoTIC to isolate EVs from cancer patient clinical samples, including plasma, urine, and lavage, demonstrating the device's broad applicability to cancers and other diseases. Finally, the ability of ExoTIC to efficiently isolate EVs from small sample volumes opens up avenues for preclinical studies in small animal tumor models and for point-of-care EV-based clinical testing from fingerprick quantities (10-100 ?L) of blood.

    View details for DOI 10.1021/acsnano.7b04878

    View details for PubMedID 29090896

  • Activation of Notch1 synergizes with multiple pathways in promoting castration-resistant prostate cancer PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Stoyanova, T., Riedinger, M., Lin, S., Faltermeier, C. M., Smith, B. A., Zhang, K. X., Going, C. C., Goldstein, A. S., Lee, J. K., Drake, J. M., Rice, M. A., Hsu, E., Nowroozizadeh, B., Castor, B., Orellana, S. Y., Blum, S. M., Cheng, D., Pienta, K. J., Reiter, R. E., Pitteri, S. J., Huang, J., Witte, O. N. 2016; 113 (42): E6457-E6466


    Metastatic castration-resistant prostate cancer (CRPC) is the primary cause of prostate cancer-specific mortality. Defining new mechanisms that can predict recurrence and drive lethal CRPC is critical. Here, we demonstrate that localized high-risk prostate cancer and metastatic CRPC, but not benign prostate tissues or low/intermediate-risk prostate cancer, express high levels of nuclear Notch homolog 1, translocation-associated (Notch1) receptor intracellular domain. Chronic activation of Notch1 synergizes with multiple oncogenic pathways altered in early disease to promote the development of prostate adenocarcinoma. These tumors display features of epithelial-to-mesenchymal transition, a cellular state associated with increased tumor aggressiveness. Consistent with its activation in clinical CRPC, tumors driven by Notch1 intracellular domain in combination with multiple pathways altered in prostate cancer are metastatic and resistant to androgen deprivation. Our study provides functional evidence that the Notch1 signaling axis synergizes with alternative pathways in promoting metastatic CRPC and may represent a new therapeutic target for advanced prostate cancer.

    View details for DOI 10.1073/pnas.1614529113

    View details for PubMedID 27694579

  • Integrin-linked kinase as a novel molecular switch of the IL-6-NF-?B signaling loop in breast cancer. Carcinogenesis Hsu, E. C., Kulp, S. K., Huang, H. L., Tu, H. J., Chao, M. W., Tseng, Y. C., Yang, M. C., Salunke, S. B., Sullivan, N. J., Chen, W. C., Zhang, J., Teng, C. M., Fu, W. M., Sun, D., Wicha, M. S., Shapiro, C. L., Chen, C. S. 2016


    Substantial evidence has clearly demonstrated the role of the IL-6-NF-?B signaling loop in promoting aggressive phenotypes in breast cancer. However, the exact mechanism by which this inflammatory loop is regulated remains to be defined. Here, we report that integrin-linked kinase (ILK) acts as a molecular switch for this feedback loop. Specifically, we show that IL-6 induces ILK expression via E2F1 upregulation, which, in turn, activates NF-?B signaling to facilitate IL-6 production. shRNA-mediated knockdown or pharmacological inhibition of ILK disrupted this IL-6-NF-?B signaling loop, and blocked IL-6-induced cancer stem cells in vitro and estrogen independent tumor growth in vivo. Together, these findings establish ILK as an intermediary effector of the IL-6-NF-?B feedback loop and a promising therapeutic target for breast cancer.

    View details for DOI 10.1093/carcin/bgw020

    View details for PubMedID 26905583

  • Preclinical Investigation of the Novel Histone Deacetylase Inhibitor AR-42 in the Treatment of Cancer-Induced Cachexia. Journal of the National Cancer Institute Tseng, Y., Kulp, S. K., Lai, I., Hsu, E., He, W. A., Frankhouser, D. E., Yan, P. S., Mo, X., Bloomston, M., Lesinski, G. B., Marcucci, G., Guttridge, D. C., Bekaii-Saab, T., Chen, C. 2015; 107 (12)


    Cancer cachexia is a debilitating condition that impacts patient morbidity, mortality, and quality of life and for which effective therapies are lacking. The anticachectic activity of the novel HDAC inhibitor AR-42 was investigated in murine models of cancer cachexia.The effects of AR-42 on classic features of cachexia were evaluated in the C-26 colon adenocarcinoma and Lewis lung carcinoma (LLC) models. Effects on survival in comparison with approved HDAC inhibitors (vorinostat, romidepsin) were determined. The muscle metabolome and transcriptome (by RNA-seq), as well as serum cytokine profile, were evaluated. Data were analyzed using mixed effects models, analysis of variance, or log-rank tests. All statistical tests were two-sided.In the C-26 model, orally administered AR-42 preserved body weight (23.9±2.6 grams, AR-42-treated; 20.8±1.3 grams, vehicle-treated; P = .005), prolonged survival (P < .001), prevented reductions in muscle and adipose tissue mass, muscle fiber size, and muscle strength and restored intramuscular mRNA expression of the E3 ligases MuRF1 and Atrogin-1 to basal levels (n = 8). This anticachectic effect, confirmed in the LLC model, was not observed after treatment with vorinostat and romidepsin. AR-42 suppressed tumor-induced changes in inflammatory cytokine production and multiple procachexia drivers (IL-6, IL-6R?, leukemia inhibitory factor, Foxo1, Atrogin-1, MuRF1, adipose triglyceride lipase, uncoupling protein 3, and myocyte enhancer factor 2c). Metabolomic analysis revealed cachexia-associated changes in glycolysis, glycogen synthesis, and protein degradation in muscle, which were restored by AR-42 to a state characteristic of tumor-free mice.These findings support further investigation of AR-42 as part of a comprehensive therapeutic strategy for cancer cachexia.

    View details for DOI 10.1093/jnci/djv274

    View details for PubMedID 26464423

  • Function of Integrin-Linked Kinase in Modulating the Stemness of IL-6-Abundant Breast Cancer Cells by Regulating ?-Secretase-Mediated Notch1 Activation in Caveolae. Neoplasia Hsu, E., Kulp, S. K., Huang, H., Tu, H., Salunke, S. B., Sullivan, N. J., Sun, D., Wicha, M. S., Shapiro, C. L., Chen, C. 2015; 17 (6): 497-508


    Interleukin-6 (IL-6) and Notch signaling are important regulators of breast cancer stem cells (CSCs), which drive the malignant phenotype through self-renewal, differentiation, and development of therapeutic resistance. We investigated the role of integrin-linked kinase (ILK) in regulating IL-6-driven Notch1 activation and the ability to target breast CSCs through ILK inhibition. Ectopic expression/short hairpin RNA-mediated knockdown of ILK, pharmacological inhibition of ILK with the small molecule T315, Western blot analysis, immunofluorescence, and luciferase reporter assays were used to evaluate the regulation of IL-6-driven Notch1 activation by ILK in IL-6-producing triple-negative breast cancer cell lines (MDA-MB-231, SUM-159) and in MCF-7 and MCF-7(IL-6) cells. The effects of ILK on ?-secretase complex assembly and cellular localization were determined by immunofluorescence, Western blots of membrane fractions, and immunoprecipitation. In vivo effects of T315-induced ILK inhibition on CSCs in SUM-159 xenograft models were assessed by mammosphere assays, flow cytometry, and tumorigenicity assays. Results show that the genetic knockdown or pharmacological inhibition of ILK suppressed Notch1 activation and the abundance of the ?-secretase components presenilin-1, nicastrin, and presenilin enhancer 2 at the posttranscriptional level via inhibition of caveolin-1-dependent membrane assembly of the ?-secretase complex. Accordingly, knockdown of ILK inhibited breast CSC-like properties in vitro and the breast CSC subpopulation in vivo in xenograft tumor models. Based on these findings, we propose a novel function of ILK in regulating ?-secretase-mediated Notch1 activation, which suggests the targeting of ILK as a therapeutic approach to suppress IL-6-induced breast CSCs.

    View details for DOI 10.1016/j.neo.2015.06.001

    View details for PubMedID 26152358

  • Targeting Energy Metabolic and Oncogenic Signaling Pathways in Triple-negative Breast Cancer by a Novel Adenosine Monophosphate-activated Protein Kinase (AMPK) Activator JOURNAL OF BIOLOGICAL CHEMISTRY Lee, K., Hsu, E., Guh, J., Yang, H., Wang, D., Kulp, S. K., Shapiro, C. L., Chen, C. 2011; 286 (45): 39247-39258


    The antitumor activities of the novel adenosine monophosphate-activated protein kinase (AMPK) activator, OSU-53, were assessed in in vitro and in vivo models of triple-negative breast cancer. OSU-53 directly stimulated recombinant AMPK kinase activity (EC(50), 0.3 ?M) and inhibited the viability and clonogenic growth of MDA-MB-231 and MDA-MB-468 cells with equal potency (IC(50), 5 and 2 ?M, respectively) despite lack of LKB1 expression in MDA-MB-231 cells. Nonmalignant MCF-10A cells, however, were unaffected. Beyond AMPK-mediated effects on mammalian target of rapamycin signaling and lipogenesis, OSU-53 also targeted multiple AMPK downstream pathways. Among these, the protein phosphatase 2A-dependent dephosphorylation of Akt is noteworthy because it circumvents the feedback activation of Akt that results from mammalian target of rapamycin inhibition. OSU-53 also modulated energy homeostasis by suppressing fatty acid biosynthesis and shifting the metabolism to oxidation by up-regulating the expression of key regulators of mitochondrial biogenesis, such as a peroxisome proliferator-activated receptor ? coactivator 1? and the transcription factor nuclear respiratory factor 1. Moreover, OSU-53 suppressed LPS-induced IL-6 production, thereby blocking subsequent Stat3 activation, and inhibited hypoxia-induced epithelial-mesenchymal transition in association with the silencing of hypoxia-inducible factor 1a and the E-cadherin repressor Snail. In MDA-MB-231 tumor-bearing mice, daily oral administration of OSU-53 (50 and 100 mg/kg) suppressed tumor growth by 47-49% and modulated relevant intratumoral biomarkers of drug activity. However, OSU-53 also induced protective autophagy that attenuated its antiproliferative potency. Accordingly, cotreatment with the autophagy inhibitor chloroquine increased the in vivo tumor-suppressive activity of OSU-53. OSU-53 is a potent, orally bioavailable AMPK activator that acts through a broad spectrum of antitumor activities.

    View details for DOI 10.1074/jbc.M111.264598

    View details for Web of Science ID 000296759800043

    View details for PubMedID 21917926

  • Identification and Characterization of a Novel Integrin-Linked Kinase Inhibitor JOURNAL OF MEDICINAL CHEMISTRY Lee, S., Hsu, E., Chou, C., Chuang, H., Bai, L., Kulp, S. K., Chen, C. 2011; 54 (18): 6364-6374


    Integrin-linked kinase (ILK) represents a relevant target for cancer therapy in light of its role in promoting oncogenesis and tumor progression. Through the screening of an in-house focused compound library, we identified N-methyl-3-(1-(4-(piperazin-1-yl)phenyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-3-yl)propanamide (22) as a novel ILK inhibitor (IC(50), 0.6 ?M), which exhibited high in vitro potency against a panel of prostate and breast cancer cell lines (IC(50), 1-2.5 ?M), while normal epithelial cells were unaffected. Compound 22 facilitated the dephosphorylation of Akt at Ser-473 and other ILK targets, including glycogen synthase kinase-3? and myosin light chain. Moreover, 22 suppressed the expression of the transcription/translation factor YB-1 and its targets HER2 and EGFR in PC-3 cells, which could be rescued by the stable expression of constitutively active ILK. Evidence indicates that 22 induced autophagy and apoptosis, both of which were integral to its antiproliferative activity. Together, this broad spectrum of mechanisms underlies the therapeutic potential of 22 in cancer treatment, which is manifested by its in vivo efficacy as a single oral agent in suppressing PC-3 xenograft tumor growth.

    View details for DOI 10.1021/jm2007744

    View details for Web of Science ID 000294875300017

    View details for PubMedID 21823616

  • Overlapping High-Resolution Copy Number Alterations in Cancer Genomes Identified Putative Cancer Genes in Hepatocellular Carcinoma HEPATOLOGY Chen, C., Hsu, E., Lin, K., Tu, P., Chang, H., Lin, C., Chen, Y., Gu, D., Lin, C., Wu, J., Chen, Y., Hsu, M., Jou, Y. 2010; 52 (5): 1690-1701


    Recurrent cancer genome aberrations are indicators of residing crucial cancer genes. Although recent advances in genomic technologies have led to a global view of cancer genome aberrations, the identification of target genes and biomarkers from the aberrant loci remains difficult. To facilitate searches of cancer genes in human hepatocellular carcinoma (HCC), we established a comprehensive protocol to analyze copy number alterations (CNAs) in cancer genomes using high-density single nucleotide polymorphism arrays with unpaired reference genomes. We identified common HCC genes by overlapping the shared aberrant loci in multiple cell lines with functional validation and clinical implications. A total of 653 amplicons and 57 homozygous deletions (HDs) were revealed in 23 cell lines. To search for novel HCC genes, we overlapped aberrant loci to uncover 6 HDs and 126 amplicons shared by at least two cell lines. We selected two novel genes, fibronectin type III domain containing 3B (FNDC3B) at the 3q26.3 overlapped amplicon and solute carrier family 29 member 2 (SLC29A2) at the 11q13.2 overlapped amplicon, to investigate their aberrations in HCC tumorigenesis. Aberrant up-regulation of FNDC3B and SLC29A2 occurred in multiple HCC data sets. Knockdown of these genes in amplified cells decreased cell proliferation, anchorage-independent growth, and tumor formation in xenograft models. Importantly, up-regulation of SLC29A2 in HCC tissues was significantly associated with advanced stages (P = 0.0031), vascular invasion (P = 0.0353), and poor patient survival (P = 0.0325). Overexpression of FNDC3B or SLC29A2 in unamplified HCC cells promoted cell proliferation through activation of the signal transducer and activator of transcription 3 signaling pathway.A standardized genome-wide CNA analysis protocol using data from user-generated or public domains normalized with unpaired reference genomes has been established to facilitate high-throughput detection of cancer genes as significant target genes and biomarkers for cancer diagnosis and therapy.

    View details for DOI 10.1002/hep.23847

    View details for Web of Science ID 000283764800019

    View details for PubMedID 20799341

  • Repression of hepatitis B viral gene expression by transcription factor nuclear factor-kappaB CELLULAR MICROBIOLOGY Lin, Y., Hsu, E., Ting, L. 2009; 11 (4): 645-660


    Infection of human hepatitis B virus (HBV) causes acute hepatitis. Its persistent infection leads to a high risk of developing chronic hepatitis, cirrhosis and hepatocellular carcinoma. The levels of HBV 3.5 kb and 2.4/2.1 kb RNAs transcribed from a replicating HBV expression plasmid in human hepatoma HuH-7 cells are repressed by tumour necrosis factor alpha treatment or overexpressed p65 in a dose-dependent manner. The diminished expression of endogenous p65 by a p65-specific siRNA or IkappaB-alpha overexpression enhances the HBV gene expression. The protein bound to the Specificity protein 1 (Sp1) binding sites (nt 1733-1753) of HBV core promoter is reduced by either tumour necrosis factor alpha treatment or overexpressed p65. The N-terminal 43-amino-acid region of p65, which is required to interact with Sp1, is essential to repress the Sp1-mediated transactivation. The binding of Sp1 to Sp1 site and the Sp1-dependent reporter expression are inhibited by p65 in a dose-dependent manner. Furthermore, nuclear factor-kappa B-mediated repression of HBV gene expression is abolished by deletion of Sp1 sites of HBV gene promoter. Together, these results demonstrate that nuclear factor-kappa B represses the HBV gene expression through its interaction with Sp1 and repression of Sp1-mediated transcriptional activation.

    View details for DOI 10.1111/j.1462-5822.2008.01280.x

    View details for Web of Science ID 000263855300009

    View details for PubMedID 19141126

  • Suppression of hepatitis B viral gene expression by protein-tyrosine phosphatase PTPN3 JOURNAL OF BIOMEDICAL SCIENCE Hsu, E., Lin, Y., Hung, C., Huang, C., Lee, M., Yang, S., Ting, L. 2007; 14 (6): 731-744


    Protein-tyrosine phosphatase PTPN3 is a membrane-associated non-receptor protein-tyrosine phosphatase. PTPN3 contains a N-terminal FERM domain, a middle PDZ domain, and a C-terminal phosphatase domain. Upon co-expression of PTPN3, the level of human hepatitis B viral (HBV) RNAs, 3.5 kb, 2.4/2.1 kb, and 0.7 kb transcribed from a replicating HBV expression plasmid is significantly reduced in human hepatoma HuH-7 cells. When the expression of endogenous PTPN3 protein is diminished by specific small interfering RNA, the expression of HBV genes is enhanced, indicating that the endogenous PTPN3 indeed plays a suppressive role on HBV gene expression. PTPN3 can interact with HBV core protein. The interaction is mediated via the PDZ domain of PTPN3 and the carboxyl-terminal last four amino acids of core. Either deletion of PDZ domain of PTPN3 or substitution of PDZ ligand in core has no effect on PTPN3-mediated suppression. These results clearly show that the interaction of PTPN3 with core is not required for PTPN3 suppressive effect. Mutation of (359)serine and (835)serine of 14-3-3beta binding sites to alanine, which slightly reduces the interaction with 14-3-3beta, does not influence the PTPN3 effect. In contrast, mutation of the invariant (842)cysteine residue in phosphatase domain to serine, which makes the phosphatase activity inactive, does not change its subcellular localization and interaction with core or 14-3-3beta, but completely abolishes PTPN3-mediated suppression. Furthermore, deletion of FERM domain does not affect the phosphatase activity or interaction with 14-3-3beta, but changes the subcellular localization from cytoskeleton-membrane interface to cytoplasm and nucleus, abolishes binding to core, and diminishes the PTPN3 effect on HBV gene expression. Taken together, these results demonstrate that the phosphatase activity and FERM domain of PTPN3 are essential for its suppression of HBV gene expression.

    View details for DOI 10.1007/s11373-007-9187-x

    View details for Web of Science ID 000250119200003

    View details for PubMedID 17588219

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