HDAC Inhibitors Potentiate the Activity of the BCR/ABL Kinase Inhibitor KW-2449 in Imatinib-Sensitive or -Resistant BCR/ABL+ Leukemia Cells In Vitro and In Vivo

Abstract

Purpose The purpose of this study was to determine whether HDAC inhibitors (HDACIs) such as vorinostat or entinostat (SNDX-275) could increase the lethality of the dual Bcr/Abl-aurora kinase inhibitor KW-2449 in various Bcr/Abl+ human leukemia cells, including those resistant to imatinib mesylate (IM). Experimental Design Bcr/Abl+ CML and ALL cells, including those resistant to IM (T315I, E255K) were exposed to KW-2449 in the presence or absence of vorinostat or SNDX-275, after which apoptosis and effects on signaling pathways were examined. In vivo studies combining HDACIs and KW2449 were performed using a systemic IM-resistant ALL xenograft model. Results Co-administration of HDACIs synergistically increased KW-2449 lethality in vitro in multiple CML and Ph+ ALL cell types including human IM resistant cells (e.g. BV-173/E255K, Adult/T315I). Combined treatment resulted in inactivation of Bcr/Abl and downstream targets (e.g. STAT5 and CRKL), as well as increased ROS generation and DNA damage (γH2A.X). The latter events and cell death were significantly attenuated by free radical scavengers (TBAP). Increased lethality was also observed in primary CD34+ cells from patients with CML, but not in normal CD34+ cells. Finally, minimally active vorinostat or SNDX275 doses markedly increased KW2449 anti-tumor effects and significantly prolonged the survival of murine xenografts bearing IM-resistant ALL cells (BV173/E255K). Conclusions HDACIs increase KW-2449 lethality in Bcr/Abl+ cells in association with inhibition of Bcr/Abl, generation of ROS, and induction of DNA damage. This strategy preferentially targets primary Bcr/Abl+ hematopoietic cells and exhibits enhanced in vivo activity. Combining KW-2449 with HDACIs warrants attention in IM-resistant Bcr/Abl+ leukemias.

Inhibition of Aurora kinases enhances chemosensitivity to temozolomide and causes radiosensitization in glioblastoma cells

“…Our data showed the synergistic eVects of concomitant treatment with ZM and TMZ on glioblastoma cell lines and primary cultures, as observed in proliferation assays. This agrees with the Wndings of previous studies in which the inhibition of Aurora kinases by ZM augmented the antiproliferative eVects of other chemotherapeutic agents in human cancer cell lines (Georgieva et al 2010;Nguyen et al 2011;Zhang and Zhang 2011). We also found that ZM sensitized glioblastoma cells to radiation and this eVect was enhanced when ZM was associated with TMZ.…”

“…al. 2009;Nguyen et al 2011;Niermann et al 2011;Santo et al 2011). Our data showed the synergistic eVects of concomitant treatment with ZM and TMZ on glioblastoma cell lines and primary cultures, as observed in proliferation assays.…”

Proteasome inhibitor MG-132 enhances histone deacetylase inhibitor SAHA-induced cell death of chronic myeloid leukemia cells by an ROS-mediated mechanism and downregulation of the Bcr-Abl fusion protein

“…A number of reports have suggested that the increases in ROS generation may stem from Bcr-Abl kinase inhibition and that ROS levels are increased downstream of Bcr-Abl (24,25). However, in the present study, NAC reversed the cell death and Bcr-Abl downregulation induced by combined treatment of SAHA and MG-132, which indicates that the increase in ROS is upstream of Bcr-Abl downregulation and mediates the synergistic effect of SAHA and MG-132 in CML cells.…”

Analysis of BCR/ABL transcripts in healthy individuals

“…Although the detection of low levels of BCR/ABL transcripts in CML patients is used in disease control strategies, new observations have demonstrated that malignant cell persistence is not necessarily dependent on higher activity in BCR/ABL signaling pathways (Jilani et al, 2008;Corbin et al, 2011;Nguyen et al, 2011). The reverse transcription-PCR technique is extremely sensitive, and can detect primary transcripts even at low levels of expression.…”