Antitumor effects of human interferon-alpha 2b secreted by recombinant bacillus Calmette-Guérin vaccine on bladder cancer cells

Objective：Our objective was to construct a recombinant bacillus Calmette-Guérin vaccine（rBCG） that secretes human interferon-alpha 2b（IFNα-2b） and to study its immunogenicity and in vitro antitumor activity against human bladder cancer cell lines T24 and T5637.Methods：The signal sequence BCG Ag85B and the gene IFNα-2b were amplified from the genome of BCG and human peripheral blood,respectively,by polymerase chain reaction（PCR）.The two genes were cloned in Escherichia coli-BCG shuttle-vector pMV261 to obtain a new recombinant plasmid pMV261-Ag85B-IFNα-2b.BCG was transformed with the recombinant plasmid by electroporation and designated rBCG-IFNα-2b.Mononuclear cells were isolated from human peripheral blood（PBMCs） and stimulated with rBCG-IFNα-2b or wild type BCG for 3 d,and then cultured with human bladder cancer cell lines T24 and T5637.Their cytotoxicities were measured by 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide（MTT） assay.Results：BCG was successfully transformed with the recombinant plasmid pMV261-Ag85B-IFNα-2b by electroporation and the recombinant BCG（rBCG-IFNα-2b） was capable of synthesizing and secreting cytokine IFNα-2b.PBMC proliferation was enhanced significantly by rBCG-IFNα-2b,and the cytotoxicity of PBMCs stimulated by rBCG-IFNα-2b to T24 and T5627 was significantly stronger in comparison to wild type BCG.Conclusions：A recombinant BCG,secreting human IFNα-2b（rBCG-IFNα-2b）,was constructed successfully and was superior to control wild type BCG in inducing immune responses and enhancing cytotoxicity to human bladder cancer cell lines T24 and T5637.This suggests that rBCG-IFNα-2b could be a promising agent for bladder cancer patients in terms of possible reductions in both clinical dosage and side effects of BCG immunotherapy.