INDUCTION OF PROTEIN-TYROSINE PHOSPHORYLATION IN MACROPHAGES INCUBATED WITH TUMOR-CELLS

The cellular and molecular interaction between monocyte/macrophage and tumor cells leading to macrophage activation is not clearly understoo d. Since protein tyrosine phosphorylation appears to be a major intrac ellular signalling event, we checked whether the tumor cells alter tyr osine phosphorylation of proteins in macrophages. We found that both L 929 and Yac-1 tumor cells induced increased tyrosine phosphorylation o f several polypeptides in peritoneal as well as P388D-1 and IC-21 macr ophages. Macrophages co-cultured with tumor cells also showed increase d fluorescence with anti-phosphotyrosine-FITC antibody. These observat ions suggest that increased tyrosine phosphorylation plays a role in t umor cell-induced activation of macrophages.