Effects of tRA pretreatment on As₂O₃-induced apoptosis.

(A) Apoptosis. NB4 and R4 cells were treated with 1 μM tRA for indicated times and washed with PBS to remove tRA; then the cells were treated with 2 μM As₂O₃ for 24 hours. Apoptotic cells were measured by morphologic changes using fluorescence microscopy. The values were mean plus SE of 3 independent experiments. (B) Western blot analysis of Bcl-2 levels after treatment with 1 μM tRA for indicated times. (C) Northern blot analysis of Bfl-1/A1 expression after treatment with tRA for indicated times.