RESUMO
BACKGROUND: The antitumor growth and antimetastatic activity of panaxanthone (approximately 80% alpha-mangostin and 20% gamma-mangostin) were studied in a mouse metastatic mammary cancer model that produces a metastatic spectrum similar to that seen in human breast cancer. MATERIALS AND METHODS: Mammary tumors, induced by inoculation of syngeneic BALB/c mice with BJMC3879 cells, were subsequently treated with panaxanthone at 0, 2,500, or 5,000 ppm in their diet. In vitro studies were also conducted to evaluate the effects of alpha-mangostin, the main component of panaxanthone, on BJMC3879 cells. RESULTS: In the in vivo study, tumor volumes were significantly suppressed in mice treated with 2,500 and 5,000 ppm panaxanthone in their diet. The multiplicity of lung metastasis was significantly lower in the 5,000 ppm group. Lymph node metastasis also tended to decrease in the 5,000 ppm group but not significantly. The antitumor effects of panaxanthone were associated with elevation of apoptotic cell death, antiproliferation (inhibition of PCNA) and antiangiogenesis (inhibition of microvessel density). The in vitro study demonstrated that alpha-mangostin induced apoptosis, as evidenced by increased numbers of TUNEL-positive cells, elevated activities of caspases and a decrease in mitochondrial membrane potential, cell cycle arrest in the G(1)-phase and decreases in the cell population in the S- and G(2)/M-phases. CONCLUSION: These results suggest that the observed antimetastatic activity of panaxanthone may be of clinical significance as adjuvant therapy in metastatic human breast cancer, and may also be useful as a chemopreventative of breast cancer development.