Immunotherapy for Orthotopic Murine Bladder Cancer Using Bacillus Calmette-Guerin Recombinant Protein Mpt-64

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Abstract

Purpose

We investigated the efficacy of the recombinant bacillus Calmette-Guerin subunit protein vaccine Mpt-64 for inducing cytokine production and suppressing orthotopic bladder tumor growth in mice.

Materials and Methods

One mycobacteria candidate gene (Mpt-64) was cloned and ligated into eukaryotic expression vectors. The induction and efficiency of Mpt-64 protein expression were detected using Western blotting. Various doses of Mpt-64 proteins were instilled intravesically 6 times in 2 weeks after intravesical implantation of MBT-2 tumor cells in chemical injured urothelium. Systemic cytokine responses, tumor growth and cumulative survival rates were monitored.

Results

In vitro expression of recombinant Mpt-64 subunit protein was efficient in our system. Mice treated with 100 and 200 μg Mpt-64 subunit proteins significantly inhibited orthotopic MBT-2 tumor growth in C3H/HeN mice compared with that in control and 50 μg treatment groups in terms of the tumor taking rate, bladder tumor burden and mortality rate. Meanwhile, marked increased serum interferon-γ with a limited but significant increase in serum interleukin-2 was observed in mice treated with 100 and 200 μg Mpt-64 proteins compared with control and 50 μg treated groups.

Conclusions

A highly immunopotent recombinant Mpt-64 subunit protein of bacillus Calmette-Guerin was produced and it elicited immune responses with a high serum interferon-γ level, inhibited orthotopic tumor growth and prolonged survival in tumor bearing mice. Thus, intravesical immunogenic therapy using recombinant Mpt-64 protein may be an alternative bacillus Calmette-Guerin regimen for superficial bladder cancer.

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