Immune responses to tumor-associated antigens are often detectable in tumor-bearing hosts, but they fail to eliminate malignant cells or prevent development of metastases. Tumor cells produce factors such as interleukin-10, transforming growth factor-β1 and vascular endothelial growth factor (VEGF) that suppress the function of immune cells or induce apoptosis of immune cells. Culture supernatant of tumor cells may contain these immunosuppressive factors which suppress lymphocyte activation. CD71 and FasL are two important molecules that are expressed upon lymphocyte activation. Counteraction against suppression CD71 and FasL expression upon lymphocyte activation may benefit tumor control. A potential component with this effect is Ganoderma lucidum polysaccharides (Gl-PS). In this study, Gl-PS was used on lymphocytes incubating with culture supernatant of B16F10 melanoma cells (B16F10-CS) in the presence of phytohemagglutinin. Following induction with phytohemagglutinin, B16F10-CS suppressed CD71 expression in lymphocytes (as detected by immunofluorescence and flow cytometry), proliferation in lymphocytes (as detected by MTT assay), and FasL expression in lymphocytes (as detected by immunocytochemistry and western blot analysis), while Gl-PS fully or partially counteracted these suppressions. Gl-PS showed counteractive effects against suppression induced by B16F10-CS on CD71 and FasL expression upon lymphocyte activation, suggesting the potential of Gl-PS to facilitate cancer immunotherapy.
Keywords: CD71; FasL; Ganoderma lucidum; lymphocyte activation; polysaccharides; tumor.