title: Simultaneous human papilloma virus type 16 E7 and cdk inhibitor p21 expression induces apoptosis and cathepsin B activation.
abstract: Human papillomavirus type 16 (HPV-16) is the major risk factor for development of cervical cancer. The major oncoprotein E7 enhances cell growth control. However, E7 has in some reports been shown to induce apoptosis suggesting that there is a delicate balance between cell proliferation and induction of cell death. We have used the osteosarcoma cell line U2OS cells provided with E7 and the cdk2 inhibitor p21 (cip1/waf1) under inducible control, as a model system for the analysis of E7-mediated apoptosis. Our data shows that simultaneous expression of E7 and p21 proteins induces cell death, possibly because of conflicting growth control. Interestingly, E7/p21-induced cell death is associated with the activation of a newly identified mediator of apoptosis, namely cathepsin B. Activation of the cellular caspases is undetectable in cells undergoing E7/p21-induced apoptosis. To our knowledge, this is the first time a role for cathepsin B is reported in HPV-induced apoptotic signalling.
authors.affiliation: The DNA Tumour Virus Group, Institute of Molecular Pathology, The Protein Laboratory, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200, Copenhagen, Denmark.
authors.forename: Dorte Wissing
authors.initials: DW
authors.lastname: Kaznelson
authors.forename: Silas
authors.initials: S
authors.lastname: Bruun
authors.forename: Astrid
authors.initials: A
authors.lastname: Monrad
authors.forename: Simon
authors.initials: S
authors.lastname: Gjerløv
authors.forename: Jesper
authors.initials: J
authors.lastname: Birk
authors.forename: Carsten
authors.initials: C
authors.lastname: Röpke
authors.forename: Bodil
authors.initials: B
authors.lastname: Norrild
mesh_terms: D017209:Apoptosis; D002401:Cathepsin B / Q000378:metabolism*; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D027383:Papillomaviridae / Q000378:metabolism; D050725:Papillomavirus E7 Proteins; D019076:Transgenes
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D002401:Cathepsin B