Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Research Article Tumor Biol 2009;30:61–72 DOI: 10.1159/000214438 HPV 16 E2 Protein Induces Apoptosis in Human and Murine HPV 16 Transformed Epithelial Cells and Has Antitumoral Effects in vivo V.H. Bermúdez-Morales a, d O. Peralta-Zaragoza a E. Guzmán-Olea b A. García-Carrancá c M. Bahena-Román a J.M. Alcocer-González e V. Madrid-Marina a a Chronic Infection and Cancer, National Institute of Public Health, Cuernavaca, b Polytechnic University of Morelos State, Jiutepec, c Unit of Biomedical Research in Cancer, National Cancer Institute/Biomedical Research Institute, and d Medicine School, National Autonomous University of Mexico, Mexico City, and e School of Biological Science, Autonomous University of Nuevo Leon, Monterrey, Mexico Introduction Human papillomaviruses (HPVs) are members of a DNA tumor virus family that infect epithelial cells and generally induce benign hyperproliferative lesions. How- ever, high-risk HPV, such as types 16 and 18, induce pre- cancerous genital lesions and carcinomas [1–3]. Malignant transformation depends on the continuous expression of the HPV E6 and E7 oncogenes, which modulate and per- turb cellular proteins that regulate the cell cycle and the function of tumor suppressor genes such as p53 and p105 Rb [4–7]. It is thought that this process is important for the viral life cycle and HPV-induced tumorigenesis [4]. The HPV E2 protein plays an important role in the transcriptional regulation of viral genes and in viral DNA replication [8–10]. In HPV-infected cells, the HPV ge- nome exists as an episomal DNA, where the HPV E2 pro- tein binds to specific sites in the long control region to regulate the transcription of the viral genes, such as the HPV E6 and E7 oncogenes. However, in HPV-trans- formed cervical cancer cells the HPV genome often be- comes integrated into the host genome [11–13], which may result in inactivation of E2 gene expression, thereby leading to deregulation of viral gene expression and in- creased levels of HPV E6 and E7 oncoproteins [4, 14–16] , Key Words HPV 16 E2  Apoptosis  Cell death  Epithelial cells Abstract Objective: Our aims were to examine the ability of the hu- man papillomaviruse (HPV) 16 E2 protein to induce apopto- sis in a murine HPV-transformed cell line, and to evaluate its antitumor properties on HPV-associated tumors in vivo in immunocompetent mice. Methods: HPV-transformed mu- rine BMK-16/myc cells and human SiHa cells were transfect- ed with the HPV 16 E2 gene to examine the effects of the E2 protein on cell growth and on the E6 and E7 oncogenes as well as DNA fragmentation and activation of the extrinsic pathway of apoptosis. Finally, to test the antitumor effect of the E2 protein on an experimental mouse tumor model, we generated a recombinant adenovirus expressing the E2 pro- tein. Results: The E2 protein inhibited the growth of SiHa and BMK-16/myc cell lines, and repressed the E6 and E7 on- cogenes. Moreover, the E2 protein induced DNA fragmenta- tion and apoptosis through activation of caspases 8 and 3 in BMK-16/myc cells. On the other hand, E2 also showed antitu- mor effects in vivo. Conclusions: Our findings indicate that E2 exerts pro-apoptotic activity in a murine HPV-trans- formed cell line as well as an antitumor effect in vivo. Copyright © 2009 S. Karger AG, Basel Received: September 9, 2008 Accepted after revision: February 10, 2009 Published online: April 22, 2009 Vicente Madrid-Marina Chronic Infection and Cancer, National Institute of Public Health Av. Universidad 655 Santa María Ahuacatitlán, Cuernavaca Morelos (Mexico) 62508 Tel. +52 777 329 3056, Fax +52 777 317 5485, E-Mail vmarina@correo.insp.mx © 2009 S. Karger AG, Basel 1010–4283/09/0302–0061$26.00/0 Accessible online at: www.karger.com/tbi