Cell cycle-related expression and ligand binding of peripheral benzodiazepine receptor in human breast cancer cell lines

The aim of this study was to measure the expression of peripheral benzodiaz epine receptors (PBR) as well as mitochondria content in different phases o f the cell cycle of BT-20 and MCF-7 breast cancer cell lints, using two-par ameter flow cytometric analyses. The PER expression as well as mitochondria mass, were found to increase as cells pass through different stages of the cell cycle, whereas the amount of PER in quiescent cells was very low. Bin ding capacity for the PER ligand [H-3]-Ro5-4864 was strongly related to the phase of the cell cycle with a positive correlation (r = 0.98) with a high percentage of cells in S phase. Incubation of BT-20 cells in serum-deprive d medium with nanomolar concentrations of Ro5-4864 caused an increase in S phase cells. This effect was not observed in MCF-7 cells. Using micromolar concentrations of Ro5-4864, both BT-20 and MCF-7 cells were reversibly arre sted in the G(0.1) phase. (C) 2000 Elsevier Science Ltd. All rights reserve d.