OppositeEffectsof DextransSubstitutedwith Sulfhydrylsor Mercury on TumorGrowth

Macromoleculan dextrans carrying substituents termi nated by sulfhydryl groups on terminated by aromatic amines effectively inhibit the growth of a fibrosancoma and of a mammary adenocarcinoma in a syngeneic mouse model. These compounds have no or very low toxicity to animals and are nontoxic to fibrosancoma cells in vitro. Small-molecular-weight compounds carrying the same sub stituents as the above dextrans are without any effect on the growth of these tumors. A dextran substituted with mercury-containing side chains is growth promoting for the same fibrosancoma in mice at doses which are nontoxic for these animals. However, the mercury-containing compound is toxic to fibrosarcoma cells in vitro. It is hypothesized that these nonpermeating macromolecules do not directly influ ence the tumor cells in animals but modulate the natural system of defense against tumors; cells of that system are stimulated on poisoned by the substituted dextrans.