The anti-tumor activity of Morinda citrifolia fruit juice (Noni) has been previously reported. However, the mechanism behind this activity remains unknown. In the present study, we studied the anti-tumor activity of fermented Noni exudate (fNE) and demonstrated that intraperitoneal injection of this material significantly increased the percentages of granulocytes and NK cells in the peripheral blood, peritoneum, and spleen. Furthermore, in preventive and treatment settings, fNE injection induced complete tumor rejection in normal C57BL/6J mice, partial tumor rejection in C57 nude mice lacking functional lymphocytes, and no tumor rejection in NK cell deficient beige mice. Over 85% of the C57BL/6J mice that received fNE survived the first tumor injection and rejected up to 5x106 tumor cells when re-challenged. The anti-tumor activity remains in the heat-inactivated and filtrated supernatant of fNE. These data demonstrate that fNE appears to be able to stimulate the innate immune system and the adaptive immune system to reject tumor cells. NK cells respond quickly and appear to be among the major players of the innate immune system, while the adaptive immune system reacts later with a retained memory.

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