The medicinal mushroom Ganoderma lucidum attenuates UV-induced skin carcinogenesis and immunosuppression

The medicinal mushroom Ganoderma lucidum is traditionally used for treating multiple diseases, including cancer. This study examined skin cancer preventive activity of a commercial product containing spore and fruiting body in 30:8 ratio (GLSF). Extracts of GLSF and spore component (GLS) were prepared using artificial gastrointestinal juice and examined on JB6 cells. GLSF and GLS dose-dependently inhibited epidermal growth factor-induced JB6 transformation at non-toxic concentrations. SKH-1 mice which were fed with diets containing GLSF (1.25%), GLS (0.99%) or the fruiting body (GLF) (0.26%) were exposed to chronic low-dose ultraviolet (UV) radiation to assess their effects on skin carcinogenesis. GLSF, but not GLS or GLF, reduced skin tumor incidence and multiplicity. In non-tumor skin tissues of mice, GLSF attenuated UV-induced epidermal thickening, expression of Ki-67, COX-2 and NF-κB, while in tumor tissues, GLSF increased expression of CD8 and Granzyme B. To examine the effects of GLSF on UV-induced immunosuppression, mice which were fed with GLSF were evaluated for the contact hypersensitivity (CHS) response to dinitrofluorobenzene (DNFB). GLSF significantly reversed UV-mediated suppression of DNFB-induced CHS by increasing CD8+ and decreasing CD4+ and FoxP3+ T-cells in mouse ears. Therefore, GLSF prevents skin cancer probably via attenuating UV-induced immunosuppression.