EXPRESSION OF ANTITUMOR RESPONSE - ROLE OF ATTACHMENT AND VIABILITY OF BACILLUS-CALMETTE-GUERIN TO BLADDER-CANCER CELLS

Background. Antitumor effects of Bacillus Calmette-Guerin (BCG) agains t superficial urinary bladder cancer is known to be strong when BCG is directly infused into the bladder cavity. For expression of that effe ct, attachment of BCG to tumor cells is reported to be essential as th e first step. Our study was conducted to elucidate the significance of attachment of BCG to tumor cells in inducing the antitumor effect. Me thods. BCG, Tokyo 172 strain, in the form of live bacilli, lyophilized bacilli, or autoclaved bacilli was co-cultured with MBT-2, mouse-orig in transitional cell cancer cells. Various preparations of BCG were mi xed with MBT-2 cells and transplanted to male C3H/He mice to see tumor growth-inhibiting effect. Results. Both live and lyophilized BCG atta ched strongly to MBT-2 cells. The maximal attachment to the cells with live BCG occurred 24 hours earlier than with lyophilized BCG. When BC G was autoclaved, it lost the ability to attach to the cells. Lyophili zed or autoclaved BCG exerted a marked tumor growth-inhibiting effects . This effect was equal to the Tokyo 172 strain and the Armand Frappie r Canada strain. Histotogically, a high degree of infiltration by macr ophages was seen. Conclusions. The results indicated that coexistence of BCG, even as killed by autoclaving, with tumor cells activates loca l immunity. Accordingly, the significance of the attachment of BCG to tumor cells in intravesical infusion therapy is surmised to lie in the fact that it results in retention of the BCG at the reaction site. Th is may provide a clue on how to approach future development of safer a nd more stable BCG-derived antitumor drugs.