Effects of PSK on T and dendritic cells differentiation in gastric or colorectal cancer patients.

Background: Vaccine therapy targeting tumor antigens recognized by cytotoxic T cells (CTL) has been tried extensively. However, in a cancer-bearing state, the Th1/Th2 balance shifts to Th2 dominance, and this has been the obstacle to vaccine therapy to induce the CTL. DC1/DC2 subsets have also been reported to control the differentiation of Th subsets. The key to tumor immunotherapy is how to activate the DC1-Th1 lineage. Patients and Methods: Six normal adults and 14 patients with gastric or colorectal cancers, who gave informed consent, were studied. The Th1/Th2 and DC1/DC2 ratios were determined by FACS. IL- 12 and IL-10 production from PBMC were measured by ELISA. Results: The Th1/Th2 and DC1/DC2 ratios were all significantly lower in the patients with gastric or colorectal cancers compared to normal adults. After protein-bound polysaccharide K (PSK) therapy in cancer patients, the Th1/Th2 balance shifted to Th1 dominance and the DC1/DC2 balance to DC1 dominance. IL-10 production was significantly decreased by PSK therapy. Conclusion: In the cancer-bearing state, the Th1/Th2 and DC/1/DC2 balance becomes Th2- and DC2-dominant. PSK therapy results in a shift of the Th1/Th2 and DC1/DC2 balance towards Th1 and DC1 dominance. We plan to examine whether combining dendritic cells (DC) vaccination therapy with oral PSK enhances the induction of T cell and DC differentiation in cancer patients. In tumor immunology, cytotoxic T cells (CTL) are considered to be the major effector cells against tumor cells. Many trials of vaccine therapies targeting tumor antigens recognized by CTL have been conducted. CTL are activated