Targeting MEK/MAPK signal transduction module potentiates ATO-induced apoptosis in multiple myeloma cells through multiple signaling pathways

Abstract

IntroductionMultiple myeloma (MM) is a clonal B-cell malignancy characterized by the accumulation of malignant plasma cells within the bone marrow (BM). Despite treatment with alkylating agents, anthracyclines, corticosteroids, 1,2 and bortezomib 3 as well as high-dose therapy and stem cell transplantation, 4-6 MM remains an incurable disease because of the high resistance to apoptosis and both intrinsic and acquired drug resistance. [7][8][9][10][11][12] Therefore, new therapeutic strategies are needed to improve patient outcome.Preclinical in vitro and in vivo studies showed that arsenic trioxide (ATO) has antimyeloma effects both as a single agent [13][14][15][16] and in combination with glutathione-depleting agents [17][18][19] and/or other antimyeloma agents. 15,20,21 Moreover, the combined results of 3 phase 2 studies in patients with relapsed MM refractory to conventional chemotherapy showed only modest efficacy of ATO as single agent, [22][23][24][25][26][27][28] but combination therapies with ascorbic acid, melphalan, steroids, thalidomide, and bortezomib have shown promising results. [29][30][31][32][33][34] We have previously demonstrated that PD184352 (PD), a highly selective inhibitor of MEK phosphorylation and activation, strikingly enhances ATO-mediated apoptosis in acute myelogenous leukemia (AML) via multiple intrinsic apoptotic pathways activation. [35][36][37] MEK blockade efficiently and selectively sensitizes tumor cells to suboptimal doses of other apoptotic stimuli, including classic cytotoxic treatment (nucleoside analogs, microtubule-targeted drugs, ␥-irradiation), 38-43 biologicals (retinoids, interferons), 44,45 steroids, [46][47][48] and other signal transduction/apoptosis modulators (UCN-01, STI571, Bcl-2 antagonists, Bcl-2 antisense oligonucleotides). [49][50][51][52][53] In this study, we tested the apoptotic activity of ATO combined with MEK inhibitors in MM cells, and we were able to demonstrate that PD enhances ATO-induced cytotoxicity both in vitro and in vivo in a human plasmacytoma xenograft model, through a multiple modulation of apoptotic regulatory proteins, including p53 family proteins, TRAIL receptors, several Bcl-2 family proteins, and caspases, that depend on the functionality of the p53 pathway. MethodsApproval for the study was obtained from the Institutional Review Board of the Department of Clinical Sciences, University of Parma (Parma, Italy). ReagentsATO was purchased from Sigma-Aldrich (St Louis, MO). A 1 mM stock solution was obtained by dissolving ATO in phosphate-buffered saline.Submitted October 3, 2007; accepted June 12, 2008. Prepublished online as Blood First Edition paper, June 26, 2008; DOI 10.1182 DOI 10. /blood-2007 The online version of this article contains a data supplement.The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. For personal use only. on April 27, 2019. by guest www.bloodj...

Arsenic trioxide-mediated growth inhibition of myeloma cells is associated with an extrinsic or intrinsic signaling pathway through activation of TRAIL or TRAIL receptor 2

“…In this regard, it is noteworthy that TRAIL, a TNF superfamily member, ligates two types of receptors: death receptors triggering TRAIL-induced apoptosis (TRAIL R1 and TRAIL R2) and decoy receptors that act as sinks for TRAIL and administering ATO to MM patients. More studies showed a synergic effect when ATO is administered in combination with other anti-MM drugs, such as bortezomib, the DNA methylation inhibitor 5-azacytidine and melphalan et al [31][32][33][34] The findings in this study offer a promising and novel strategy, using ATO to activate TRAIL, in the treatment of myelomas, especially those aggressive myeloma subtypes with low expression of TRAIL, such as MS subgroup with reciprocal translocation (4:14) and MF subgroup with reciprocal translocations (14:16) and (14:20).…”

E3 ubiquitin ligase Cbl-b potentiates the apoptotic action of arsenic trioxide by inhibiting the PI3K/Akt pathway

“…ATO is also a potent inducer of apoptosis in a number of other cell types such as acute myeloid leukemia (AML) (3), multiple myeloma (4), and lymphocytic leukemia (5) cells. Several mechanisms have been proposed to explain ATO-induced apoptosis, including the down-regulation of the PML-RARα fusion protein (6), the involvement of a mitochondrial pathway (7)(8)(9), production of superoxides (8,10), triggering of apoptosis-associated factors (3), and signal transduction (4,10). However, the sensitivity of different types of cells to ATO differs, and the low sensitivity of some cells has restricted its clinical application.…”

A mechanistic rationale for MEK inhibitor therapy in myeloma based on blockade of MAF oncogene expression

“…Previous preclinical studies have documented activity of MEK inhibitors against myeloma cell lines and osteoclasts. [8][9][10] A novel, potent inhibitor of MEK1/2 affected MAF protein levels in the MM cell line H929. 11 We now extend these findings to a larger panel of MM cell lines to investigate whether particular myeloma subtypes would be especially sensitive to MEK inhibition.…”