Effects of lentinan on colorectal carcinogenesis in mice with ulcerative colitis

Lentinan; i.e., polysaccharides extracted from a kind of black mushroom shi itake, has been clinically applied as an antitumor and antimetastatic drug, and has been reported to prevent both chemical and viral carcinogenesis. I t is known that lentinan affects the tumorous vascular system resulting in the induction of hemorrhagic necrosis which is dependent on T-cells in the tumor. Repeated mucosal necrosis-regeneration sequence in chronic ulcerativ e colitis induced with 3% dextran sulfate sodium led to colorectal carcinog enesis in azoxymethane-pretreated mice. In the present study, the additive treatment with lentinan in the azoxymethane-dextran sulfate sodium treated mice enhanced the colorectal high-grade dysplasia, though not significantly , and the splenic weight. This may show the proliferation of pathogenic spl enic T cells resulting in a change for the worse of ulcerative colitis, ane mia induced with hemorrhage and colorectal carcinogenesis; i.e., high-grade dysplasia of the mucosa and/or invasive adenocarcinomas of the colorectum. The present results may recommend chemoimmunotherapy while using lentinan, but not immunotherapy using lentinan alone, is indicated for the managemen t of cancer patients.