Blockade of MEK signaling potentiates 5‐Aza‐2′‐deoxycytidine‐induced apoptosis and upregulation of p21^waf1 in acute myelogenous leukemia cells

Abstract

We have recently reported that the mitogen-activated protein kinase/ERK kinase (MEK) inhibitor AZD6244 (ARRY-142886) strikingly potentiated the effects of histone deacetylase inhibitor to induce growth arrest and apoptosis of acute myelogeneous leukemia (AML) cells in association with enhanced upregulation of p21waf1 . This study examined the effects of the MEK inhibitor on the action of DNA methyltransferase inhibitor 5-Aza-2 0 -deoxycytidine (5-AzadC), another epigenetic agent in AML cells. AZD6244 significantly potentiated the ability of 5-AzadC to induce growth arrest and apoptosis of NB4, and freshly isolated AML cells. In parallel, 5-AzadC induced expression of p21 waf1 in AML cells, which was potently enhanced in the presence of AZD6244. Further studies explored the molecular mechanisms by which 5-AzadC induced expression of p21 waf1 and found that a low dose of 5-AzadC (1 lM) induced acetylation of histone H3 on the p21 waf1 gene promoter; however, higher dose of this compound (3 or 5 lM) potently induced DNA damage as assessed by expression of cH2AX, in NB4 cells. These effects were strikingly enhanced by concomitant blockade of MEK signaling. Furthermore, knockdown of p21waf1 by the siRNA rescued NB4 cells from 5-AzadCmediated growth inhibition. Taken together, combination of 5-AzadC and the MEK inhibitor may be useful for treatment of individuals with a subset of AML. ' 2009 UICC

ERK inhibition enhances TSA-induced gastric cancer cell apoptosis via NF-κB-dependent and Notch-independent mechanism

“…Chromatin immunoprecipitation assay was performed as described previously (Nishioka et al, 2009). SGC7901 cells (5×10 5 /ml) were cultured with TSA (800 nM) and/or PD98059 (50 μM) for 24 h. Untreated cells were used as controls.…”

“…Western blot analysis was performed as described previously (Nishioka et al, 2009). Protein concentrations were quantitated using a Bio-Rad assay (Bio-Rad Laboratories, Hercules, CA, USA).…”

The heterogeneity of pediatric MLL-rearranged acute myeloid leukemia

“…117,118 Inhibitors of MEK have been developed that sensitize leukemic blast cells to other drugs, for example, arsenic trioxide and demethylating agents. [119][120][121] Current RAS pathway inhibitors probably will not fully block leukemic transformation in MLL-rearranged AML, but may have an additive effect with current treatment strategies by targeting the proliferative advantage of these leukemic cells. 122 Another possibility is to directly target the MLL complex.…”

Long-term exposure of leukemia cells to multi-targeted tyrosine kinase inhibitor induces activations of AKT, ERK and STAT5 signaling via epigenetic silencing of the PTEN gene

“…Real-time PCR was performed by using the Power SYBR Green PCR Master Mix (Applied Biosystems), as described earlier. 36 The amplified sequences were normalized to those from input (cross-linked DNA/protein complexes), which were not immunoprecipitated with the anti-acetylated histone H3 antibody, as described earlier. 36 …”