Quantity of nucleolar silver-stained proteins is related to proliferating activity in cancer cells

The relationship between the silver-stained proteins of interphase nucleolar organizer regions (NORs) and proliferative activity was studied in 12 established cell lines derived from different tumor types. Quantitative evaluation of NOR proteins was carried out on silver-stained cells, by means of an automated image analyzer and the cell proliferation rate was measured with [3H] thymidine labeling. A linear relationship was found between cell duplication activity and the amount of silver-stained NOR proteins independently of the type of cancer cells (r = 0.94, p less than 0.001). Measurement of silver-stained NOR protein could thus be used as a simple estimate of cancer cell proliferation rate.