Abstract
The mechanisms of non-specific resistance to syngeneic methylcholanthrene-induced fibrosarcomas of mice were investigated. Results showed that a small tumour graft of 0.05 X 10(5) cells is greatly enhanced in growth when admixed with large numbers of cell fragments, killed cells or viable non-replicating cells. The enhancement of small tumour grafts in cell mixtures was found to be non-specific. Carrageenan, a known anti-macrophage agent, significantly increased tumour growth in normal mice. However, it did not enhance the increased tumour growth of 0.05 X 10(5) cells mixed with 10(6) viable, non-replicating mitomycin C-treated tumour cells. The latter observation indicates that carrageenan and admixed cells interfere with the same tumour-inhibitory mechanism and therefore cannot produce additive effects. The results give support to the concept of a non-specific macrophage "surveillance" system which appears crucial in controlling tumour growth, since it determines the establishment of small numbers of tumour cells while they can still be easily destroyed.
Highlights
Carrageenan, a known anti-macrophage agent, significantly increased tumour growth in normal mice
The following investigation was undertaken to determine whether carrageenan, a product of marine algae selectively cytotoxic for macrophages (Allison et al, 1966; Schwartz & Leskowitz, 1969; Catanzaro et al, 1971), would cause the establishment of small numbers of viable tumour cells which would not normally grow
The following study involved mitomycin C-treated syngeneic fibrosarcoma cells as a source of non-replicating cells, to see whether they would cause the establishment of small numbers of tumour cells in mixtures and, if so, to determine whether such growth was enhanced by carrageenan
Summary
Carrageenan, a known anti-macrophage agent, significantly increased tumour growth in normal mice It did not enhance the increased tumour growth of 0 05 x cells mixed with viable, non-replicating mitomycin C-treated tumour cells. The following investigation was undertaken to determine whether carrageenan, a product of marine algae selectively cytotoxic for macrophages (Allison et al, 1966; Schwartz & Leskowitz, 1969; Catanzaro et al, 1971), would cause the establishment of small numbers of viable tumour cells which would not normally grow. The following study involved mitomycin C-treated syngeneic fibrosarcoma cells as a source of non-replicating cells, to see whether they would cause the establishment of small numbers of tumour cells in mixtures and, if so, to determine whether such growth was enhanced by carrageenan
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