Fig. 1. Modulation of cancer-immune system interaction and cancer prevention by Bacillus Calmette-Guérin (BCG). Available data suggests that BCG effectuates primary cancer prevention by mitigating chronic inflammation and by bolstering the immune system to eliminate tumor cells. Also, BCG can tilt the balance towards elimination of tumor cells by the immune system during the equilibrium phase. BCG can reactivate the immune system in cancers with an immunosuppressive microenvironment. Containment of tumor cells by the reactivated immune system results in tertiary cancer prevention as observed in the case of non-muscle invasive bladder cancer. NK, natural killer.

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