Ethacrynic Acid Oxadiazole Analogs Induce Apoptosis in Malignant Hematologic Cells through Downregulation of Mcl-1 and c-FLIP, Which Was Attenuated by GSTP1-1

Abstract

Ethacrynic acid, a diuretic, inhibits glutathione S-transferase P1-1 (GSTP1-1) activity and induces cell death in malignant cells at high concentrations. To improve ethacrynic acid activity, ethacrynic acid oxadiazole analogs 6s and 6u were synthesized. Although both compounds have greater antiproliferative effects than ethacrynic acid in human HL-60 cells, 6u has a reduced ability to inhibit GSTP1-1 activity. The mechanisms of both 6s-and 6u-induced cell death as well as the role of GSTP1-1 in their actions were studied. Both 6s and 6u equally induced apoptosis in HL-60 cells due to the activation of caspase-3, -9, and -8, which was correlated with the downregulation of antiapoptotic proteins c-FLIP, Mcl-1, and XIAP. The caspase inhibitor Z-VAD-FMK blocked the reduction of XIAP, but not of c-FLIP and Mcl-1, in 6s-treated cells. The reduction of c-FLIP and Mcl-1 by 6s was not blocked by the proteasomal inhibitor MG132, but was correlated with inhibition of the phosphorylation of extracellular signal-regulated kinase (ERK) and eIF4E. Both 6s and 6u decreased the intracellular glutathione (GSH) levels. N-acetylcysteine blocked reduction in the levels of Mcl-1, c-FLIP, and intracellular GSH as well as apoptosis in HL-60 cells treated by either compound. Silencing of GSTP1-1 in K562 cells sensitized, but overexpression of GSTP1-1 in Raji cells blocked, apoptosis induction by either compound. GSH conjugation at the methylene group abrogated the ability of inducing apoptosis. These data suggest that the methylene group plays an important role in the downregulation of c-FLIP and Mcl-1 proteins and apoptosis induction, which is inactivated by GSTP1-1 by forming GSH conjugates.

Involvement of AMP-activated protein kinase in mediating pyrrolo-1,5-benzoxazepine–induced apoptosis in neuroblastoma cells

“…Pretreatment with NAC was found to abrogate the effects of PBOX-6 on Mcl-1 expression. This was in agreement with previous reports of the inhibition of the mTOR pathway by the diuretic, ethacrynic acid, leading to a block in translation of Mcl-1, which could be blocked by pretreatment with NAC in HL-60 cells [59]. It is likely that PBOX-6 induced mTOR inhibition is an early event (up to 6 h) which precedes PBOX-6 induced cell cycle arrest and apoptosis in SHSY5Y cells.…”

Dihydroartemisinin and its derivative induce apoptosis in acute myeloid leukemia through Noxa-mediated pathway requiring iron and endoperoxide moiety

“…The levels of those proteins were measured in HL-60 cells treated with DHA and X-11. Previously we reported that HL-60 cells did not express Bcl-xL and that decreasing the Mcl-1 protein level could induce apoptosis in HL-60 cells [21, 22]. Neither Mcl-1 level, nor Bcl-2, Bax or Bak were changed after treatment with DHA and X-11 (Fig.…”

GSTP1 as a novel target in radiation induced lung injury

“…GSTP1 also could inhibit the interaction between tumor necrosis factor-related receptor 2 (TRAF2) and apoptosis signal-regulating kinase 1 (ASK1) by binding to TRAF2, negatively regulated the ASK1–MEK–JNK/p38 pathway induced by tumor necrosis factor α (TNFα), which inhibited cell apoptosis [ 30 ]. However, Guyue Liu showed that GSTP1 could induce apoptosis in malignant hematologic cells via downregulation of myeloid cell leukemia-1 (Mcl-1) and cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP) [ 49 ]. GSTP1 also could induce apoptosis through the Fas-ASK1-JNK/p38 pathway by amplifying Fas ligand [ 50 ].…”