A novel intracellular antibody against the E6 oncoprotein impairs growth of human papillomavirus 16-positive tumor cells in mouse models
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Carla Amici1, Michela Visintin2, Francesca Verachi1,3, Francesca Paolini4, Zulema Percario5, Paola Di Bonito3, Angela Mandarino3, Elisabetta Affabris5, Aldo Venuti4 and Luisa Accardi3
1 University of Rome Tor Vergata, Department of Biology, Via della Ricerca Scientifica, Rome, Italy
2 Rottapharm Biotech Srl, Biotherapeutics Discovery, Area Science Park – Basovizza, Trieste, Italy
3 Istituto Superiore di Sanità, Department of Infectious, Parasitic and Immunomediated Diseases, Viale Regina Elena, Rome, Italy
4 Regina Elena National Cancer Institute, Laboratory of Virology and HPV-Unit, via delle Messi d’Oro, Rome, Italy
5 University Roma Tre, Department of Science, Viale G. Marconi, Rome, Italy
Luisa Accardi, email:
Keywords: E6 oncoprotein, human papillomaviruses, cancer therapy, scFv, intracellular antibodies
Received: September 03, 2015 Accepted: January 04, 2016 Published: January 15, 2016
Single-chain variable fragments (scFvs) expressed as “intracellular antibodies” (intrabodies) can target intracellular antigens to hamper their function efficaciously and specifically. Here we use an intrabody targeting the E6 oncoprotein of Human papillomavirus 16 (HPV16) to address the issue of a non-invasive therapy for HPV cancer patients.
A scFv against the HPV16 E6 was selected by Intracellular Antibody Capture Technology and expressed as I7nuc in the nucleus of HPV16-positive SiHa, HPV-negative C33A and 293T cells. Colocalization of I7nuc and recombinant E6 was observed in different cell compartments, obtaining evidence of E6 delocalization ascribable to I7nuc. In SiHa cells, I7nuc expressed by pLNCX retroviral vector was able to partially inhibit degradation of the main E6 target p53, and induced p53 accumulation in nucleus. When analyzing in vitro activity on cell proliferation and survival, I7nuc was able to decrease growth inducing late apoptosis and necrosis of SiHa cells.
Finally, I7nuc antitumor activity was demonstrated in two pre-clinical models of HPV tumors. C57BL/6 mice were injected subcutaneously with HPV16-positive TC-1 or C3 tumor cells, infected with pLNCX retroviral vector expressing or non-expressing I7nuc. All the mice injected with I7nuc-expressing cells showed a clear delay in tumor onset; 60% and 40% of mice receiving TC-1 and C3 cells, respectively, remained tumor-free for 17 weeks of follow-up, whereas 100% of the controls were tumor-bearing 20 days post-inoculum. Our data support the therapeutic potential of E6-targeted I7nuc against HPV tumors.
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