Active Chinese mistletoe lectin-55 enhances colon cancer surveillance through regulating innate and adaptive immune responses.

AIM To investigate the potential role of active Chinese mistletoe lectin-55 (ACML-55) in tumor immune surveillance. METHODS In this study, an experimental model was established by hypodermic inoculating the colon cancer cell line CT26 (5 x 10(5) cells) into BALB/c mice. The experimental treatment was orally administered with ACML-55 or PBS, followed by the inoculation of colon cancer cell line CT26. Intracellular cytokine staining was used to detect IFN-gamma production by tumor antigen specific CD8+ T cells. FACS analysis was employed to profile composition and activation of CD4+, CD8+, gammadelta T and NK cells. RESULTS Our results showed, compared to PBS treated mice, ACML-55 treatment significantly delayed colon cancer development in colon cancer-bearing Balb/c mice in vivo. Treatment with ACML-55 enhanced both Ag specific activation and proliferation of CD4+ and CD8+ T cells, and increased the number of tumor Ag specific CD8+ T cells. It was more important to increase the frequency of tumor Ag specific IFN-gamma producing-CD8+ T cells. Interestingly, ACML-55 treatment also showed increased cell number of NK, and gammadeltaT cells, indicating the role of ACML-55 in activation of innate lymphocytes. CONCLUSION Our results demonstrate that ACML-55 therapy can enhance function in immune surveillance in colon cancer-bearing mice through regulating both innate and adaptive immune responses.