Divergent effects of macrophage toxins on growth of primary tumors and lung metastases in mice

The effects of silica and carrageenan on primary tumor growth and metastases were evaluated in C57BL/6 and BALB/c mice transplanted with the poorly immunogenic Lewis lung (3LL) carcinoma, mFS6 sarcoma and Madison 109 carcinoma spontaneously metastasizing to the lungs. Silica and carrageenan significantly enhanced lung metastases and decreased primary tumor weight in all three experimental models. A similar augmentation of lung secondaries was found after i.v. inoculation of 3LL tumor cells. The effects of carrageenan on primary 3LL tumor growth and metastases were observed also in thymus-deprived animals. The effect of macrophage toxins was studied also in C57BL/6 mice transplanted with the M5076/73A ovarian carcinoma. This tumor spontaneously metastasizes to various abdominal organs, but not to the lung. After treatment with carrageenan, lung metastases were observed, but no effect on secondaries at other anatomical sites or on the primary tumor was detectable. It is suggested that host defense mechanisms impaired by silica and carrageenan may have divergent effects in the regulation of growth of some primary tumors and spontaneous lung metastases.