[Relationship between the Ki-67 nuclear antigen content and cell-cycle perturbation on WiDr cells treated with 5-FU]

The profile of Ki-67 nuclear antigen content according to the change in the cell-cycle of WiDr cells affected by 5-fluorouracil (5-FU) was studied by flow cytometry. The cases who received 10 micrograms/ml for 1 hr and showed reproliferation in the growth curve presented significant accumulation at G2M phases. However, significant increase of Ki-67 antigen content was not observed in G2M phases. Meanwhile, the cases who continuously received 10 micrograms/ml for 72 hr and showed the suppression of cellular proliferation without reproliferation presented gradual accumulation into S phase and Ki-67 antigen content was found to be significantly increased. This increase occurred in G1 phase, and the cells with Ki-67 antigen content of the largest increase in G1 phase shifted to S phase. It indicates a possibility that Ki-67 nuclear antigen content is destined to be controlled specifically in G1 phase of the cell-cycle. 5-FU seems to damage this regulation system and, as a result, increase Ki-67 nuclear antigen.