Recently, many efforts have been made to treat
cancer using recombinant
bacterial toxins and this strategy has been used in clinical trials of various
cancers. Therapeutic
DNA cancer vaccines are now considered as a promising strategy to activate the immune system against
cancer.
Cancer vaccines could induce specific and long-lasting immune responses against
tumors. This study aimed to evaluate the antitumor potency of the SEB
DNA vaccine as a new antitumor candidate against
breast tumors in vivo. To determine the effect of the SEB construct on inhibiting
tumor cell growth in vivo, the synthetic SEB gene, subsequent
codon optimization, and embedding the cleavage sites were sub-cloned to an expression vector. Then, SEB construct, SEB, and PBS were injected into the mice. After being vaccinated, 4T1
cancer cells were injected subcutaneously into the right flank of mice. Then, the
cytokine levels of
IL-4 and IFN-γ were estimated by the ELISA method to evaluate the antitumor activity. The spleen lymphocyte proliferation,
tumor size, and survival time were assessed. The concentration of IFN-γ in the SEB-Vac group showed a significant increase compared to other groups. The production of
IL-4 in the group that received the
DNA vaccine did not change significantly compared to the control group. The lymphocyte proliferation increased significantly in the mice group that received SEB construct than PBS control group (p < 0.001). While there was a meaningful decrease in
tumor size (p < 0.001), a significant increase in
tumor tissue
necrosis (p < 0.01) and also in survival time of the animal model receiving the recombinant construct was observed. The designed SEB gene construct can be a new model
vaccine for
breast cancer because it effectively induces
necrosis and produces specific immune responses. This structure does not hurt normal cells and is a safer treatment than
chemotherapy and
radiation therapy. Its slow and long-term release gently stimulates the immune system and cellular memory. It could be applied as a new model for inducing apoptosis and antitumor immunity to treat
cancer.