Alpha-2-macroglobulin in normal and malignant human cells

Using the indirect immunofluorescence technique we have studied the cellular distribution of the protease inhibitor alpha-2-macroglobulin (α₂M) in normal and malignant cultured human fibroblasts. Normal fibroblasts take up from the culture medium and accumulate into the cytoplasm large amounts of bovine α₂M. We did not detect any human α₂M synthesized by the fibroblasts. SV40 transformed human fibroblasts and two cell lines originating from a human fibrosarcoma (HT1080) and from a human rhabdomyosarcoma (RD-2) showed a reduced amount of intracellular α₂M. The α₂M, controlling the activity of cellular proteases, could play an important role in normal cellular behaviour.