Experimental study on immunochemotherapy (PSK, CQ) in rat bladder cancer (BC-47)

Cancer of the urinary bladder is a tumor with the highest frequency among urogenital cancers, and more-over, its recurrence rate is high. It is considered important and urgently necessary to conduct studies into the prevention of recurrence of this cancer. We have started a Study Group on Postoperative Maintenance Therapy for Bladder Tumor (Tokyo), and conducted group studies on the prevention of recurrence. Fundamental experiments have been performed, and the following results obtained. Antitumor effects of PSK in combination with CQ for bladder carcinoma were studied using male ACI rats. An established bladder carcinoma cell line, BC47 was transplanted into the backs of rats subcutaneously prior to the administration of PSK and CQ. Inhibitory effect on tumor growth and prolongation of survival period were examined. Although single-agent PSK or CQ both had inhibitory effects on transplanted tumors as well as on metastatic tumors in the lung, more remarkable effects were noticed as a result of combination treatment. Prolongation of lifespan using combination therapy was superior to that using single treatment and the rats of decrease in body weight was also lower. These results do not necessarily clarify the antitumor mechanisms, but the immune system, probably non-specifically, may take part in the mechanism judged from the accumulated results obtained from in vivo systems. We think that the combinational effects of these two drugs on general condition are probably originated from inhibition of tumor growth since the inhibition, prolongation of lifespan, change of body weight and so on were closely correlated with each other. However, the direct effect of these drugs may also be counted. The combination therapy of PSK and CQ seemed to be useful against rat bladder carcinoma, BC47. We therefore intend to proceed with group study trials of Postoperative Maintenance Therapy for Bladder Tumor.