Inhibition of tumor metastasis by carrageenan-induced granulomas

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Abstract
At −1, 0, +1 weeks from tumor inoculation, carrageenan-impregnated cotton sponges were subcutaneously implanted. Tumor BN472, a malignant adenocarcinoma, was transplanted in syngeneic Brown Norway female rats, either subcutaneously or intravenously. Plasma eicosanoid values (prostaglandin-E2, thromboxane-B2 and 6-keto-prostaglandin-F1α) were determined as well as the cellular immune response (natural killer activity, concanavalin-A and phytohemagglutinin stimulation of spleen lymphocytes). Primary tumor growth and the number of tumor foci in the lungs were measured as parameters of tumor growth and dissemination. No statistically significant differences were observed in primary tumor growth. However, the number of metastatic foci in the lungs of rats in which the tumor was implanted subcutaneously, as well as those in which the tumor was inoculated intravenously, was significantly reduced in those that had carrageenan implanted one week after tumor inoculation. In all other carrageenan-treated groups only slightly reduced numbers of metastatic foci were seen. In those rats with a decreased number of tumor metastatic foci in the lungs, no correlation could be shown with either altered plasma prostaglandin levels, or cellular immune response.