OncoImmunology 1:3, 316–325; May/June 2012; G 2012 Landes Bioscience DNA vaccination against oncoantigens A promise Manuela Iezzi,1 Elena Quaglino,2 Augusto Amici,3 Pier-Luigi Lollini,4 Guido Forni2 and Federica Cavallo2,* 1Aging Research Centre; G. d’Annunzio University; Chieti, Italy; 2Molecular Biotechnology Center; University of Turin; Turin, Italy; 3Department of Molecular Cellular and Animal Biology; University of Camerino; Camerino, Italy; 4Department of Hematology and Oncologic Sciences “L. & A. Seragnoli”; Alma Mater Studiorum University of Bologna; Cancer Research Section; Bologna, Italy Keywords: oncoantigens, DNA vaccination, mammary cancer, immunotherapy, ErbB-2, in vivo electroporation The emerging evidence that DNA vaccines elicit a protective immune response in rodents, dogs and cancer patients, coupled with the US Food and Drug Administration (FDA) approval of an initial DNA vaccine to treat canine tumors is beginning to close the gap between the optimistic experimental data and their difficult application in a clinical setting. Here we review a series of conceptual and biotechno- logical advances that are working together to make DNA vaccines targeting molecules that play important roles during cancer progression (oncoantigens) a promise with near-term clinical impact. Once we made a promise we swore we’d always remember No retreat, baby, no surrender Blood brothers in a stormy night With a vow to defend No retreat, baby, no surrender No Surrender, Bruce Springsteen Introduction The promise of antitumor vaccines rests on their ability to trigger a long-lasting protection against a tumor with virtually no side effects. This promise is underpinned by data from countless vaccination-tumor challenge experiments.1-3 It must be admitted that these vaccines have generated both waves of enthusiasm and total disillusionment. Even so, the fascinating possibility of controlling tumor spread through a vaccine-elicited adaptive immune response is such as to continue to spur the search for better tumor antigens and more efficient vaccination modalities.4 DNA vaccines are a precision tool for activating effective immunity against cancer.5 Their potential impact is illustrated by the first one approved by FDA in the January 2010 for the treatment of advanced canine melanoma, namely OnceptTM (Merial, Duluth, GA), a plasmid coding for human tyrosinase.6 The emerging information should also speed up the translation of new immunotherapies to patients since initiation and *Correspondence to: Federica Cavallo; Email: federica.cavallo@unito.it Submitted: 12/20/11; Accepted: 12/20/11 http://dx.doi.org/10.4161/onci.19127 progression of canine and human cancers are influenced by similar factors. However, DNA vaccines are still a promise that may appear far from being an established cancer therapy. Here we are teasing apart a few of the technological and conceptual advances working together to make DNA vaccines targeting oncoantigens, i.e., molecules that play important roles during cancer progression and that can be attached by immune reactivity, a promise with near- term clinical impact. DNA Vaccines: What are They? In DNA vaccines the antigen is replaced by its blueprint. When administered, DNA causes the expression of the protein that induce the immune response. Recombinant DNA technologies have facilitated the preparation of plasmids as compared with conventional vaccines. Adjuvant sequences can be embedded in the plasmid. These reasons make DNA vaccination popular in preclinical experiments involving rodents where it elicits cell and antibody-mediated responses to a variety of antigens. The amount of protein expressed, its persistence and the kind of antigen presentation are key variables that determine the efficacy of the protection thus elicited. See references 5 and 7 for excellent reviews on DNA vaccination in cancer. Basically, a DNA vaccine consists in a circular double strand bacterial DNA (the plasmid) in which a few eukaryotic and synthetic sequences has been inserted. To minimize the possibility of plasmid integration into host chromosomes, these are limited to the antigen sequence, an ubiquitary enhancer-promoter driving its expression and a transcription termination site. To permit insertion of the sequence coding for the antigen, the plasmid should also contain a synthetic 100 base pairs DNA sequence (the multiple cloning site). The presence of a “relaxed origin of replication” and an antibiotic-resistance gene allows efficient plasmid replication in bacterial cells and their selection, two key aspects for high-scale plasmid production. When employment of a plasmid in clinical trials is envisaged, the antibiotic-resistance should not involve antibiotics commonly used in human infections and should be less likely to elicit allergic reactions. The pVAX1 plasmid (Invitrogen) containing the Kanamycin resistance gene meets the FDA’s requirements for vectors to be used in patients. 316 OncoImmunology Volume 1 Issue 3