Protection of RARα and PML-RARα from ATRA-induced degradation by SERCA inhibition in ATRA-sensitive and ATRA-resistant cells.
(A) ATRA-sensitive wild-type HL-60 cells were treated for one day with vehicle, ATRA alone at concentrations indicated on the top of the figure, or with 3 μM tBHQ alone or in combination with ATRA; and RARα protein was detected by immunoblotting using the C-20 antibody. Immunoblotting of the same samples for β-actin was used as an internal control. (B) ATRA-sensitive wild-type NB4, as well as ATRA-resistant primed NB4-R1, NB4-R2, NB4-306, and NB4-007/6 cells were treated for one day with vehicle, 10−7 M ATRA (not shown for NB4-R2 and NB4-306 cells), or with a combination of 8 μM tBHQ and 10−7 M ATRA; and RARα, as well as PML-RARα protein was detected by immunoblotting using the RPαF′ antibody. Immunoblotting of the same samples for β-actin was used as an internal control. ΔPML-RARα corresponds to the degradation products of PML-RARα. Numbers on the right side correspond to the apparent molecular weight of the proteins in kDa. Western blots were performed 3 times.
