Xenogeneic Human p53 DNA Vaccination by Electroporation Breaks Immune Tolerance to Control Murine Tumors Expressing Mouse p53

Abstract

The pivotal role of p53 as a tumor suppressor protein is illustrated by the fact that this protein is found mutated in more than 50% of human cancers. In most cases, mutations in p53 greatly increase the otherwise short half-life of this protein in normal tissue and cause it to accumulate in the cytoplasm of tumors. The overexpression of mutated p53 in tumor cells makes p53 a potentially desirable target for the development of cancer immunotherapy. However, p53 protein represents an endogenous tumor-associated antigen (TAA). Immunization against a self-antigen is challenging because an antigen-specific immune response likely generates only low affinity antigen-specific CD8+ T-cells. This represents a bottleneck of tumor immunotherapy when targeting endogenous TAAs expressed by tumors. The objective of the current study is to develop a safe cancer immunotherapy using a naked DNA vaccine. The vaccine employs a xenogeneic p53 gene to break immune tolerance resulting in a potent therapeutic antitumor effect against tumors expressing mutated p53. Our study assessed the therapeutic antitumor effect after immunization with DNA encoding human p53 (hp53) or mouse p53 (mp53). Mice immunized with xenogeneic full length hp53 DNA plasmid intramuscularly followed by electroporation were protected against challenge with murine colon cancer MC38 while those immunized with mp53 DNA were not. In a therapeutic model, established MC38 tumors were also well controlled by treatment with hp53 DNA therapy in tumor bearing mice compared to mp53 DNA. Mice vaccinated with hp53 DNA plasmid also exhibited an increase in mp53-specific CD8+ T-cell precursors compared to vaccination with mp53 DNA. Antibody depletion experiments also demonstrated that CD8+ T-cells play crucial roles in the antitumor effects. This study showed intramuscular vaccination with xenogeneic p53 DNA vaccine followed by electroporation is capable of inducing potent antitumor effects against tumors expressing mutated p53 through CD8+ T cells.

Toll-like Receptor Agonist Imiquimod Facilitates Antigen-Specific CD8+ T-cell Accumulation in the Genital Tract Leading to Tumor Control through IFNγ

“…Cell surface marker staining for anti-mouse PE CD8 (BD RPA-T8) and intracellular cytokine staining for anti-mouse FITC IFN-γ (BD XMG1.2) as well as FACScan analysis were performed in the same conditions as those previously described (43). Lymphocytes extracted from tumor fragments were collected and incubated with 1 μg/ml of E7 peptide (RAHYNIVTF) as previously described (44) in 24-well plates for 8 hours.…”

Using the E4orf6-Based E3 Ubiquitin Ligase as a Tool To Analyze the Evolution of Adenoviruses

“…Plasmids expressing FLAG-tagged HAdV-5 and HAdV-12 E4orf6 (34), HA-tagged Cul2 and Cul5 (14), HSV-tagged Elongin C (40), mouse p53 (41), and mouse DNA ligase IV have been described previously. The corresponding genes from AdVs belonging to two different genera were studied.…”

DNA vaccines, electroporation and their applications in cancer treatment

“…114,115 In cancer cells, p53 is often mutated, 116 and is thus thought to be a potential target for cancer immunotherapy. In an animal model, IM-EP of a DNA vaccine encoding mutated human p53 displayed mouse p53 cross-reactive CD8+ T cell responses and antitumor protective and therapeutic activities in a CD8+ T cell-dependent manner, 117 suggesting that mutated p53 might also represent a useful target for cancer immune therapy.…”