Passive acquisition of leukocyte proteins is associated with changes in phosphorylation of cellular proteins and cell-cell adhesion properties.

In this report, we show that interaction of neoplastic epithelial cells with vesicles derived from leukocytes results in passive acquisition by tumor cells of a diverse group of leukocyte proteins. Vesicles shed from leukocytes were heterogeneous and exhibited the specific proteins expressed on leukocyte subsets. Accordingly, epithelial cells differentially acquired leukocyte proteins associated with vesicles. Ultrastructural localization demonstrated that acquired proteins were associated with the plasma membranes of the epithelial cells. The binding of tumor cells that passively acquired leukocyte proteins to immobilized intercellular adhesion molecule-1 and to endothelial cells was significantly increased. Furthermore, passive acquisition of proteins on the plasma membranes of epithelial cells was associated with modulation of overall phosphorylation of proteins in the range of 20-65 kd and consisted of both increased as well as decreased phosphorylation of specific protein species in the cells. These findings demonstrate that leukocyte proteins that are shed in association with vesicles passively coat the plasma membranes of target epithelial cells. Passive acquisition of proteins by cells modulates the constitutive properties endowed upon cells by their native plasma membranes and is associated with changes in phosphorylation of cell proteins.