Effects of lentinan on colorectal carcinogenesis in mice with ulcerative colitis

Lentinan; i.e., polysaccharides extracted from a kind of black mushroom shiitake, has been clinically applied as an antitumor and antimetastatic drug, and has been reported to prevent both chemical and viral carcinogenesis. It 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 ulcerative colitis induced with 3% dextran sulfate sodium led to colorectal carcinogenesis 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 splenic T cells resulting in a change for the worse of ulcerative colitis, anemia 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 management of cancer patients.