Studies on the treatment of malignant tumors with fibroblast-inhibiting agent. II. Effects of chloro­quine on animal tumors

Based on our original concept, a fibroblast-inhibiting agent, chloroquine, was used against various animal tumors. Among transplanted animal tumors, the drug was most effective on relatively connective tissue-rich Bashford and Brown-Pearce tumors, as reflected by prolongation of life span, inhibition of tumor growth, inhibition of lowering of liver catalase activity, improvement of iron metabolism, increase of tumor necrosis, inhibition of connective tissue formation, and decrease of acid mucopolysaccharide. On the other hand, it was of little advantage in Ehrlich, Yoshida and MH134 tumors which contain little connective tissue, except for a decrease of the amount of ascites and ascites tumor cells in the former two tumors. These results indicate that chloroquine suppress the growth of the tumors relatively rich in connective tissue. This effect of chloroquine appears to be due to the primary attack of the stromal connective tissue of tumors being followed by the degeneration of tumor cells, though its probable anti-tumor activity by the indirect effects through its anti-inflammatory and systemic humoral activities should be taken into consideration.