PROPORTIONALLY CONSTANT QUANTITATIVE TRANSMISSION OF NUCLEOLIN AND PROTEIN B23 IN CYCLING CANCER-CELLS

Objective-To investigate whether and to what extent the two major AgNO R proteins, nucleolin and protein B23, are maintained after one cell d ivision in proliferating cells. Design-Using three asynchronously grow ing human cancer cell lines, TG, SJNKP, and CHF 212 cells, nucleolin a nd protein B23 were first identified on SDS-polyacrylamide separated n ucleolar proteins, transferred to nitrocellulose and silver stained fo r AgNOR proteins. Measurement of doubling time indicated a period very close to 24 h for each of the cell lines. To quantify the percentage of nucleolin and protein B23 maintained in daughter cells after duplic ation, cells were labelled with [S-35]-methionine and a 24 h cold chas e performed. Nucleolin and protein B23 labelling was evaluated by dens itometric analysis on nitrocellulose autoradiograms. Results-The radio activity relative to nucleolin and protein B23 bands maintained in the daughter cells was a constant fraction of that present before cell du plication. In the three cell lines the percentage of residual radioact ivity measured in the nucleolin bands was 42.2, 40.6, and 41.2 and in protein B23 bands 48.0, 46.2, and 44.1. Conclusions-After one cell div ision the nucleolin and protein B23 quantity present in cells may be h ighly variable, depending on the amount of the two proteins present in the mother cell. This is important in relation to the correct utilisa tion of AgNOR protein quantity as an index for evaluating cell kinetic s.