p120 is a nucleolar protein that has been immunocytochemically detected in rapidly proliferating cells of a variety of human malignancies. In the present study, the relationship between p120 expression and the rapidity of cell proliferation was evaluated in 48 human tumours of different origins. The cell proliferation rate of cancer cells was determined by quantitative analysis of AgNOR proteins. p120 immunostaining and AgNOR protein quantity were measured by image cytometry and a highly significant correlation was found between the two variables, as evaluated by linear regression analysis (r=0.98, p<0.0001). The relationship between p120 expression and the rapidity of cell duplication was also studied in vitro, in six human cancer cell lines derived from different tumour types, characterized by various doubling times (ranging from 20 to 77 h). p120 expression was determined on western blots using specific anti-p120 monoclonal antibodies. Densitometric analysis revealed a highly significant inverse correlation between the integrated optical density values of the chemoluminescence bands at 120 kD and the cell line doubling times (r=-0.93; p=0.007). The same result was obtained in situ by correlating p120 immunostaining of the cytological preparations obtained from the six cancer cell lines with the corresponding doubling time (r=-0.98, p<0.0001). These results indicate that in cancer cells, the quantitative expression of p120 is directly related to the rapidity of cell duplication, independently of the tumour origin.
Copyright 2000 John Wiley & Sons, Ltd.