Lysosomal Stimulation and Inhibition of the Growth of Cells in Tissue Culture. ∗

Summary

These experiments provide evidence for the presence of a non-dialyzable, thermolabile, protein(s) in lysosomes which inhibits the growth of Strain L and Detroit 6 cells. This protein is not bound to the lysosomal membrane but is released upon rupture of the lysosome. The study tends to confirm the conclusions of other investigators, who have used a less direct approach to the problem, that lysosomes cause cell damage and inhibit cell growth. However, it has not been previously observed that the lysosomes may also stimulate cell growth when present at low concentrations. Since practically any type of cell damage may result in the rupture of the lysosomal membrane, it is of interest that the contents of the lysosome may either stimulate or inhibit the growth of the neighboring cells depending upon the number of injured cells or ruptured lysosomes.