Figure 6.

Transient mimosine treatment neither alters the increased numbers of irradiated/MAPK-inhibited cells found in G₂/M nor modifies the ability of MAPK inhibition to potentiate radiation-induced apoptosis. A431-TR25-EGFR-AS cells were pretreated for 30 min before irradiation with a MEK1/2 inhibitor (PD98059, 10 μM) or DMSO control as indicated. Cells were irradiated (2 Gy), and 3 h after irradiation, 2.0 mM mimosine (final concentration) was added to the medium. At 6 h, mimosine was removed by washing with warm medium three times. The cell cycle profiles under each condition were determined 6 and 24 h after irradiation by flow cytometry. Apoptosis determination at 24 h was by TUNEL staining. (A) Cell cycle profiles of A431-TR25-EGFR-AS cells 6 h after irradiation. (B) Cell cycle profiles of A431-TR25-EGFR-AS cells 24 h after irradiation. (C) Determination of apoptosis by TUNEL assay in A431-TR25-EGFR-AS cells 24 h after irradiation. Data are the means of three separate experiments (±SEM).