Immunotherapy for Bladder Cancer Using Recombinant Bacillus Calmette-Guerin DNA Vaccines and Interleukin-12 DNA Vaccine

Abstract

We investigated the efficacy of recombinant bacillus Calmette-Guerin (BCG) DNA (poly-rBCG) and murine interleukin (IL)-12 (mIL-12) vaccines in inducing T helper 1 polarized cytokines and suppressing bladder tumor growth in mice. Four mycobacteria candidate genes (Ag85A, Ag85B, Mpt64 and PstS3) were cloned, fused with ESAT6 and ligated into eukaryotic expression vectors. Combined poly-rBCG and mIL-12 vaccines were transferred into a murine bladder tumor model. The efficiency of gene expression was detected using Western blotting, flow cytometry and semiquantitative reverse transcriptase-polymerase chain reaction. Systemic cytokine responses, tumor growth and cumulative survival rates were monitored. Transfected bladder cancer cells showed high in vitro and in vivo expression of the recombinant subcomponents. Mice with tumors injected with poly-rBCG plus mIL-12 produced serum interferon-gamma significantly within 21 days but no significant elevations in tumor necrosis factor-alpha, IL-2, IL-4 or IL-5 were found. On day 28 after electroporation the growth of MBT-2 implants treated with poly-rBCG, mIL-12 or poly-rBCG plus mIL-12 was significantly inhibited. The cumulative survival of mice treated with poly-rBCG plus mIL-12 was significantly higher than that of the other 3 groups. Highly immunopotent recombinant vaccines of bacillus Calmette-Guerin DNA were produced that elicited T helper 1 immune responses with a high serum interferon-gamma level, inhibited tumor growth and prolonged the survival of tumor bearing mice. Thus, electroporation immunogene therapy using poly-rBCG plus mIL-12 may be an attractive regimen for the treatment of bladder cancer.