MECHANISMS OF ACTION OF BACILLUS-CALMETTE-GUERIN IN THE TREATMENT OF SUPERFICIAL BLADDER-CANCER

Local immunotherapy with bacillus Calmette-Guerin (BCG) is an effectiv e treatment to prevent recurrence and progression of superficial bladd er cancer, but the antitumor mechanism of action of BCG remains unclea r. There are some experimental and clinical data suggesting that BCG a ntigens are processed not only by immunocompetent cells but also by ur othelial cells and tumor cells. The foreign antigen may be presented a t the cell curface by major histocompatibility complex (MHC) class II molecules and recognized by CD4 cells. The cytotoxic effect could resu lt from the direct activity of CD4 cells or from the cytotoxic effect of released cytokines and the activation of other cytotoxic cells [cyt olytic T-lymphocytes CTLs; CD8 cells), macrophages, natural killer (NK ) or lymphokine-activated killer (LAK) cells]. These mechanisms are al so involved in tumorrejection, and the identification of some specific tumor rejection antigens presented to specific CTLs could provide new therapeutic approaches.