Recombinant Mycobacterium bovis BCG for immunotherapy in nonmuscle invasive bladder cancer
OBJECTIVE To investigate the antitumor effect of recombinant IFN-alpha-2b-BCG on mouse bladder cancer MB49 cells in vitro, and to explore its antitumor mechanisms. METHODS MB49 cells were co-cultured with recombinant BCG or wild BCG, and than were examined by light and transmission electron microscopy. The cell growth was assessed by MTT assay, and apoptosis rate and MHC-I of the MB49 cells was detected by flow cytometry using AO and Hoechst33258 fluorescence immunostaining. RESULTS The hIFN-alpha-2b-BCG-treated tumor cells showed slow growth, detachment of some cells, and various degree of degeneration. Light microscopy revealed organelle disorganization, chromatin aggregation, nuclear pyknosis, and cytolysis in some cells. Cellular membrane bulged and some bubbles were seen under fluorescence microscope using AO staining. Hoechst33258 assay also depicted frequent apoptosis in the tumor cells. The MTT assay showed that rBCG more actively than the wild BCG inhibited the proliferation of MB49 cells. The apoptosis rate of the recombinant BCG group was 19.7% and 46.6% at the time point of 24 h and 48 h, respectively, significantly higher than 10.8% and 20.9%, respectively, in the wild BCG group. The results of flow cytometry indicated that both types of BCG enhanced the expression of MHC-I in the MB49 cells, but more effective in the recombinant BCG group. CONCLUSION The recombinant hIFN-alpha-2b-BCG has more strong immuno-modulatory properties, anti-tumor effect on MB49 cells and induces apparent cytotoxicity in the bladder cancer cells in vitro.