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  • 1
    Keywords: CANCER ; CANCER CELLS ; CELLS ; EXPRESSION ; tumor ; carcinoma ; CELL ; Germany ; human ; INHIBITION ; GENE ; PROTEIN ; TISSUE ; CARCINOGENESIS ; DOWN-REGULATION ; E7 ; papillomavirus ; TARGET ; virus ; ELEMENT ; LESIONS ; PROMOTER ; cervical cancer ; CERVICAL-CANCER ; p53 ; GROWTH-INHIBITION ; human papillomavirus ; CANCER-CELLS ; HPV ; E6 ; ONCOGENE ; HPV16 ; HUMAN-PAPILLOMAVIRUS ; CARCINOMAS ; POSITIVE CANCER-CELLS ; TRANSLOCATION ; OVEREXPRESSION ; REPRESSION ; RETINOIC ACID ; E6 ONCOPROTEIN ; TUMOR-SUPPRESSOR ; papillomaviruses ; LEVEL ; tumor suppressor gene ; EPITHELIUM ; USA ; oncogenes ; B-CELL ; HUMAN PAPILLOMAVIRUSES ; tumor suppressor genes ; NOV ; tumor suppressor ; Luciferase reporter ; BTG2 ; cervical cancers ; viral carcinogenesis
    Abstract: Human papillomavirus (HPV)-induced carcinogenesis is critically dependent on the activities of the viral E6 and E7 oncogenes. Here, we demonstrate that expression of the putative tumor suppressor gene B-cell translocation gene-2 (BTG2) is reinduced in HPV16- and HPV18-positive cancer cells on silencing of viral oncogene expression, indicating that BTG2 is repressed by oncogenic HPVs. Inhibition of BTG2 expression was mediated by the HPV E6 oncogene and occurred in a p53-dependent manner. Luciferase reporter gene analyses revealed that BTG2 repression takes place at the transcriptional level and is dependent on the integrity of the major p53-response element within the BTG2 promoter. Ectopic expression of BTG2 acted antiproliferative in cervical cancer cells. Tissue specimens commonly exhibited reduced BTG2 protein levels in HPV-positive high-grade lesions (CIN2/3) and cervical carcinomas, when compared with normal cervical epithelium. These findings identify the antiproliferative BTG2 gene as a novel cellular target blocked by the HPV E6 oncoprotein. (C) 2009 UICC
    Type of Publication: Journal article published
    PubMed ID: 19551855
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  • 2
    Keywords: APOPTOSIS ; PROTEIN ; INDUCTION ; ASSOCIATION ; CERVICAL-CANCER ; p53 ; POSITIVE CANCER-CELLS ; NUCLEAR-LOCALIZATION ; E6-MEDIATED DEGRADATION ; AGGRESOMES
    Abstract: Oncogenic types of human papillomaviruses (HPVs) cause cervical cancer and other malignancies in humans. The HPV E6 oncoprotein is considered to be an attractive therapeutic target since its inhibition can lead to the apoptotic cell death of HPV-positive cancer cells. The HPV type 16 (HPV16) E6-binding peptide pep11, and variants thereof, induce cell death specifically in HPV16-positive cancer cells. Although they do not encompass the LxxLL binding motif found in cellular HPV16 E6 interaction partners, such as E6AP, the pep11 variants strongly bind to HPV16 E6 by contacting the recently identified E6AP binding pocket. Thus, these peptides can serve as prototype E6-inhibitory molecules which target the E6AP pocket. We here analyzed their intracellular interaction with HPV16 E6. By comprehensive intracellular binding studies and GST pull-down assays, we show that E6-binding competent pep11 variants induce the formation of a trimeric complex, consisting of pep11, HPV16 E6 and p53. These findings indicate that peptides, which do not contain the LxxLL motif, can reshape E6 to enable its interaction with p53. The formation of the trimeric HPV16 E6 / peptide / p53 complex was associated with an increase of endogenous HPV16 E6 protein amounts. Yet, total cellular p53 amounts were also increased, indicating that the E6 / E6AP-mediated degradation of p53 is blocked. These findings suggest that inhibition of oncogenic activities by targeting the E6AP pocket on HPV16 E6 could be a strategy for therapeutic intervention.
    Type of Publication: Journal article published
    PubMed ID: 26151636
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  • 3
    Keywords: CANCER ; CANCER CELLS ; CELLS ; EXPRESSION ; proliferation ; tumor ; TUMOR-CELLS ; CELL ; CELL-PROLIFERATION ; Germany ; human ; IN-VIVO ; VIVO ; GENE ; GENES ; PROTEIN ; PROTEINS ; RNA ; RELEASE ; ACTIVATION ; cell cycle ; CELL-CYCLE ; E7 ; papillomavirus ; BREAST-CANCER ; TARGET ; virus ; LESIONS ; PROGRESSION ; resistance ; cervical cancer ; CERVICAL-CANCER ; PROSTATE-CANCER ; human papillomavirus ; TYPE-16 ; CANCER-CELLS ; HPV ; E6 ; ONCOGENE ; HPV16 ; HUMAN-PAPILLOMAVIRUS ; PHENOTYPE ; ONCOPROTEIN ; METHYLTRANSFERASE ACTIVITY ; E6 ONCOPROTEIN ; ONCOLOGY ; ENHANCER ; RE ; INTERFERENCE ; RNA INTERFERENCE ; LEVEL ; USA ; oncogenes ; cancer research ; viral ; transformed cell ; GROUP PROTEIN EZH2 ; POLYCOMB REPRESSION
    Abstract: The malignant phenotype of human papillomavirus (HPV)-positive cancer cells is maintained by the activity of the viral E6 and E7 genes. Here, we identified the polycomb group gene enhancer of zeste homologue 2 (EZH2) as a novel downstream target for the viral oncogenes in HPV transformed cells. EZH2 expression was activated by HPV16 E7 at the transcriptional level via E7-mediated release of E2F from pocket proteins. RNA interference analyses showed that continuous EZH2 expression is required for the proliferation of HPV-positive tumor cells by stimulating cell cycle progression at the G(1)-S boundary. In addition to its growth-promoting activity, EZH2 also contributed to the apoptotic resistance of cervical cancer cells. Furthermore, we found that HPV-positive dysplastic and tumorigenic cervical lesions were characterized by high levels of EZH2 protein in vivo. We conclude that the E7 target gene EZH2 is a major determinant for the proliferation of HPV-positive cancer cells and contributes to their apoptotic resistance. Moreover, EZH2 may serve as a novel therapeutic target for the treatment of cervical cancer. [Cancer Res 2008;68(23):9964-72]
    Type of Publication: Journal article published
    PubMed ID: 19047178
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  • 4
    Keywords: APOPTOSIS ; CANCER ; CANCER CELLS ; CELLS ; EXPRESSION ; CELL ; Germany ; INHIBITION ; THERAPY ; PROTEIN ; BINDING ; papillomavirus ; FORM ; IDENTIFICATION ; genetics ; cervical cancer ; CERVICAL-CANCER ; p53 ; human papillomavirus ; CERVICAL-CARCINOMA CELLS ; E6 ; DEGRADATION ; POSITIVE CANCER-CELLS ; AFFINITY ; VARIANT ; THERAPIES ; cancer therapy ; LIBRARIES ; TYPE-16 E6 ; development ; P53 ACTIVITY ; oncogenes ; E6-AP
    Abstract: Specific types of human papillomaviruses (HPVs) cause cervical cancer. The viral E6 oncogene is a critical factor for maintaining the malignant phenotype of HPV-positive tumour cells. By yeast two-hybrid screening of a randomised peptide expression library, we isolated linear short peptides, which specifically bind to the HPV16 E6 oncoprotein. Sequence alignments and mutational analyses of the peptides identified a hitherto undiscovered E6-binding motif. Intracellular expression of a peptide containing the novel E6-binding motif resulted in inhibition of colony formation capacity, specifically of HPV16-positive cancer cells. A solubility-optimised variant of the peptide was created, which binds to HPV16 E6 with high affinity. Its intracellular expression efficiently induced apoptosis in HPV16-positive cancer cells. This was linked to restoration of intracellular p53 activities. Thus, this newly identified E6-binding motif could form a novel basis for the development of rational strategies for the treatment of HPV16-positive preneoplastic and neoplastic lesions
    Type of Publication: Journal article published
    PubMed ID: 19099279
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