Effect of fibronectin on macrophage-induced tumor cell cytostasis.
Purified fibronectin (Fn) mediated attachment of MCG-T14 cells, a mouse adenocarcinoma, to culture vessel surfaces. Concentrations of Fn less than 30 micrograms/ml enhanced the growth rate of these cells as judged by 3H-thymidine incorporation, whereas higher levels of Fn were inhibitory. Concentrations of Fn and macrophages, which had little or no effect on the growth rate of the T14 cells when added individually, mediated a 64% decrease in the rate of growth of these cells when cultured together. Free Fn was not required for this effect since target cells pretreated with Fn and then washed also were susceptible to growth inhibition by macrophages. These results indicate that Fn is able to mediate an enhancement of macrophage antitumor activity, probably by supporting the binding of target cells to the macrophage effector cells.