Inhibition of a human fibroblast cell-surface proteinase with alpha-1-antitrypsin also inhibited cell proliferation, confirming earlier observations. 2. Although a similar proteinase inhibition could be observed with human tumour cells, the growth of these cells was unaffected. 3. Plasminogen activators on the cell surface and in culture media could be inhibited with specific antibodies, but there was no corresponding effect on the growth of any of the cell types tested.
