Chimeric DNA Vaccines against ErbB2+ Carcinomas: From Mice to Humans

Abstract

DNA vaccination exploits a relatively simple and flexible technique to generate an immune response against microbial and tumor-associated antigens (TAAs). Its effectiveness is enhanced by the application of an electrical shock in the area of plasmid injection (electroporation). In our studies we exploited a sophisticated electroporation device approved for clinical use (Cliniporator, IGEA, Carpi, Italy). As the target antigen is an additional factor that dramatically modulates the efficacy of a vaccine, we selected ErbB2 receptor as a target since it is an ideal oncoantigen. It is overexpressed on the cell membrane by several carcinomas for which it plays an essential role in driving their progression. Most oncoantigens are self-tolerated molecules. To circumvent immune tolerance we generated two plasmids (RHuT and HuRT) coding for chimeric rat/human ErbB2 proteins. Their immunogenicity was compared in wild type mice naturally tolerant for mouse ErbB2, and in transgenic mice that are also tolerant for rat or human ErbB2. In several of these mice, RHuT and HuRT elicited a stronger anti-tumor response than plasmids coding for fully human or fully rat ErbB2. The ability of heterologous moiety to blunt immune tolerance could be exploited to elicit a significant immune response in patients. A clinical trial to delay the recurrence of ErbB2+ carcinomas of the oral cavity, oropharynx and hypopharynx is awaiting the approval of the Italian authorities.

Immunization against ROS1 by DNA Electroporation Impairs K-Ras-Driven Lung Adenocarcinomas

“…In order to increase plasmid immunogenicity, two 25-ms transcutaneous low-voltage electric pulses (amplitude 150 V; interval 300 ms) were applied to the site of injection using the Cliniporator device, which is an instrument that has already been approved for human use, and that has provided striking results in several clinical trials of electrochemotherapy [93][94][95][96][97][98]. The DNA dose, the schedule of administration, and the electroporation protocol were derived from those successfully used to immunize mice against ErbB2 and other antigens [53,54,[74][75][76]. The impossibility of predicting whether the electrovaccination using the murine homologous sequence of ROS1 would be able to break immune tolerance, leading to a detectable and effective anti-tumor immune response, spurred us to test the efficacy of both the murine and the human ROS1-coding plasmids (80% homology between human and murine ROS1 sequences).…”

The Promise of Preventive Cancer Vaccines

“…The discrepancy between the efficacy of vaccines in preclinical experiments and clinical trials is actually deceptive, as a careful analysis of preclinical data would have predicted clinical failure in most cases. In retrospect, we now know that the experimental results that have led to the enthusiastic clinical application of many anti-cancer vaccines showed bias, since most of these experiments were performed by injecting transplantable cancer cell lines into young and healthy syngeneic mice that did not present the cancer-induced constraints on immune response and the central and peripheral mechanisms of tumor antigen tolerance [ 29 , 30 , 31 ]. Moreover, the high proliferation rate of transplantable tumor cells does not reproduce the architectural and cellular complexity of real cancers and thus minimizes the consequences of tumor genetic instability, immune editing, and tumor escape ability [ 32 , 33 , 34 ].…”

“…These mice are transgenic for the mutated form of the rat ortholog of the human epidermal growth factor receptor 2 (Her2) oncogene under the transcriptional control of the mouse mammary tumor virus promoter and develop mammary carcinomas with well-defined progression, which resembles that of human breast tumors in many aspects [ 37 , 38 , 39 ]. When BALB-neuT mice are vaccinated against Her2, using either cell- [ 40 , 41 , 42 , 43 ] or gene-based vaccines [ 27 , 30 , 35 , 44 , 45 , 46 , 47 , 48 ], the intensity and effectiveness of the induced immune response are inversely proportional to the stage of carcinogenesis progression at which vaccination is started. Mice bearing precancerous lesions were successfully protected with anti-Her2 vaccination alone.…”

Tailoring DNA Vaccines: Designing Strategies Against HER2-Positive Cancers

“…To further improve the elicited protection, two new chimeric DNA vaccines (RHuT and HuRT) were constructed by combining the two advantages of specificity, ensured by syngeneic portions, and tolerance break, ensured by xenogeneic portions, all in one molecule (Jacob et al, 2010; Quaglino et al, 2010, 2011). In particular, HuRT was derived by cloning the human cDNA fragment that encodes the first 390 NH 2 -terminal residues into the rat EC5-TM cut-down plasmid to regenerate the whole EC domain.…”

“…Almost symmetrically, RHuT (Figure 1C) encodes a protein in which the 410 NH 2 -terminal residues are from the rat HER2 and the remaining residues from human HER2. Chimeric vaccines displayed superior performance in tolerant BALB-neuT mice (Jacob et al, 2010; Quaglino et al, 2010, 2011). While control mice vaccinated with empty pVAX plasmid developed rat HER2-positive mammary tumors within 27 weeks of age, all mice that had been electroporated at 10 and 12 weeks of age with RHuT or fully rat EC-TM remained tumor-free at 40 weeks.…”