Construction of recombinant human IFNα-2b BCG and its antitumor effects on bladder cancer cells in vitro

We constructed recombinant Bacille Calmette-Guérin (rBCG) that secreted human interferon alpha 2b (hIFNα-2b), and investigated its antitumor effects on bladder cancer cells in vitro. The recombinant plasmid phIFN-α-2b was constructed using pMAO-4 and transformed into BCG. The supernatant was collected at various times and IFN-γ, interleukin (IL)-12, and tumor necrosis factor (TNF)-α were detected using an enzyme-linked immunosorbent assay. EJ cells were cultivated for 24, 48, and 72 h, together with rBCG, wild-type BCG (wBCG), or wBCG+IFN-α-2b. rBCG capable of secreting cytokine IFNα-2b was constructed. On the 4th day of culture, the IFNα-2b secreted by rBCG reached a maximum. wBCG and rBCG showed no significant difference on cell growth rate over 7 days of incubation in 7H9 medium. wBCG and rBCG were both positive for acid-fast staining, and showed mycobacterial characteristics of intercellular connection in clusters with no clear abnormalities. Higher levels of IFN-γ, TNF-α, and IL-12 were induced by rBCG compared with wBCG or MAO4-rBCG (P < 0.05). rBCG may induce lymphocyte proliferation; the proliferation ratio was higher than those induced by wBCG and wBCG+IFN. rBCG had direct anti-proliferative effects on EJ cells. An MTT assay showed that rBCG inhibited the proliferation of bladder cancer cells and had more activity compared with wBCG (P < 0.05). The highest anti-tumor activity of lymphocytes was stimulated by rBCG (20.31-51.22%). rBCG-IFNα-2b induces enhanced cytotoxicity against bladder cancer cells in vitro and may be used as an alternative to BCG for bladder cancer patients.