Hideaki Ichihara, Masaki Okumura, Takashi Doi, Tatsuro Inano, Koichi Goto and Yoko Matsumoto*
The application of active ingredients in biomass in pharmaceutical products is eagerly anticipated, such as the use of dried seaweed (nori, Porphyra yezoensis) currently discarded as biomass. In this study, we used mice subcutaneously transplanted with malignant melanoma and lymphoma cells as models to examine the cancer-preventive and therapeutic effects of dried seaweed extract mediated by the immuno-stimulatory effects of components of the extract. The 15-day oral administration of seaweed extract resulted in lower tumor (melanoma) weight in the model mice. Time-dependent increases in IgA and IgG levels were observed in the serum of melanoma model mice following oral administration of seaweed extract. We observed an increase in IgA levels in a solution of the supernatant from homogenized ileal tissue from the melanoma model mice following the administration of seaweed extract. Furthermore, immunostaining revealed multiple IgA-positive cells in the ileal tissue sections of the melanoma model mice that were orally administered seaweed extract. In addition, when the model mice were orally administered seaweed extract for 7 days, the size of the subcutaneous lymphoma tumors tended to decrease, suggesting the therapeutic effect of the extract. When the mice were administered seaweed extract as a pre-treatment for 7 days before lymphoma tumor transplantation, significant shrinkage of the tumor was observed in the seaweed extract-treated mice compared with the control mice, which suggested the preventive effect of seaweed extract.
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