Continuous Ingestion of a Standardized Extract of Cultured <i>Lentinula edodes</i> Mycelia Suppresses Spontaneous Carcinogenesis in a Murine Model

AHCC^®, a standardized extract of cultured Lentinula edodes mycelia, suppresses the proliferation of both cancer cell line-derived and patient-derived xenografts transplanted into mice. However, the mechanism of action underlying the suppressive effect of AHCC on spontaneous carcinogenesis remains unclear. This study investigated the effects of long-term AHCC ingestion on spontaneous carcinogenesis and the health of C3H/HeJ mice. The mice were divided into three groups: A (2% AHCC ingestion continuously 2 d a week), B (2% AHCC ingestion daily), and C (water ingestion). The ingestion of AHCC or water was started when mice were 5 weeks old and were observed until 24 months of age. The occurrence of the first death was delayed in the AHCC-ingestion groups, and the survival rates were significantly higher in the AHCC-ingestion groups than in the control group. The proportion of "healthy mice" with no morphological abnormalities in their organs was also significantly higher in the AHCC-ingestion groups than in the control group. Furthermore, the incidence of cancer-bearing mice, particularly breast cancer and liver cancer, was significantly reduced in the AHCC-ingestion groups. The reduced rates of breast cancer were particularly higher among females of the AHCC-ingestion groups, whereas the reduced rates of liver cancer were higher among males of the AHCC-ingestion groups. These results suggest that continuous AHCC ingestion maintains health and prevents spontaneous carcinogenesis.