Antitumor potential of low-dose chemotherapy manifested in combination with immunotherapy of Viva-Natural, a dietary seaweed extract, on Lewis lung carcinoma.

Beneficial antitumor effects of low-dose chemotherapy (Adriamycin, BCNU, cisplatin, 5-fluorouracil, methotrexate, 6-thioguanine or vincristine) combined with an immunotherapy with a partially purified polysaccharide of Viva-Natural, an edible seaweed extract, have been demonstrated against intraperitoneally implanted Lewis lung carcinoma in syngeneic mice. Adriamycin, cisplatin, 5-fluorouracil and vincristine at low doses, that were not effective when given alone, manifested antitumor activity when combined with the polysaccharide fraction of Viva-Natural. Other three drugs (BCNU, methotrexate and 6-thioguanine) at the noneffective low doses exhibited no further antitumor activity when combined with Viva-Natural. Cytotoxic activation of peritoneal macrophages in mice has been induced by single administration of the polysaccharide fraction of Viva-Natural, but the combined regimen of low dose drugs plus viva-Natural was no more effective than Viva-Natural alone. Therefore, the mechanism of action of the beneficial combination is not clear yet.