Reduction of serum X-prolyl dipeptidyl-aminopeptidase activity in tumour-bearing mice and reversal of reduced enzyme activity by lentinan, an anti-tumour polysaccharide.

Serum X-prolyl dipeptidyl-aminopeptidase activity which had been shown to be depressed in cancer patients was clearly reduced in mice with Ehrlich carcinoma and Sarcoma 180, and slightly reduced in mice with methylcholanthrene-induced sarcomas. The reduced enzyme activity was completely reversed during tumour regression of sarcoma 180 by administration of lentinan, which causes regression of sarcoma 180.