Human β-defensin 2 may inhibit internalisation of bacillus Calmette-Guerin (BCG) in bladder cancer cells

Objective To investigate whether secretion of human beta-defensin 2 (HBD-2) is induced by bacillus Calmette-Guerin (BCG) and to determine whether HBD-2 affects BCG internalisation in bladder cancer cells. Materials and Methods Reverse transcription-polymerase chain reaction analysis was used to determine whether HBD-2 mRNA increases after incubation with BCG. HBD-2 proteins in 5637 and T24 human bladder cancer cell lines were assayed by enzyme-linked immunosorbent assay. The internalisation rate was evaluated by double immunofluorescence assay and confocal microscopy to test the optimal dose of HBD-2 for BCG internalisation. We also investigated the difference in internalisation rates and cell viability between recombinant HBD-2 protein, anti-HBD-2 antibody, and HBD-2 plus anti-HBD-2 antibody pretreatments. Results BCG induced HBD-2 mRNA expression and HBD-2 production dose and time-dependently in bladder cancer cells and affected BCG internalisation. Pretreatment with recombinant HBD-2 protein lowered internalisation of BCG dose-dependently. Moreover, anti-HBD-2 antibody prevented the effect of HBD-2 on BCG internalisation in bladder cancer cells. The internalisation rate of BCG pretreated with anti-HBD-2 antibody was higher than that in the control in 5637 (P < 0.01) and T24 cells (P < 0.05). The BCG internalisation rate in cells pretreated with anti-HBD-2 antibody plus recombinant HBD-2 protein was higher than that in the control in 5637 (P < 0.01) and T24 cells (P < 0.05). Mycobacterium bovis BCG decreased bladder cancer cell viability, and anti-HBD-2 antibody prevented the inhibitory role of HBD-2 on the anti-proliferative effects of M. bovis BCG in bladder cancer cells Conclusion Bladder cancer cells produce HBD-2 when they are infected by BCG to defend themselves against BCG internalisation, which plays an important role during the initiation and propagation of the immunotherapeutic response in bladder cancer cells.