Phenethyl isothiocyanate exhibits antileukemic activity in vitro and in vivo by inactivation of Akt and activation of JNK pathways

N Gao,D Chen,E-H Liu,J Chen,Z Zhang,X Shi,A Budhraja,Z Yang,S Cheng

doi:10.1038/cddis.2011.22

Abstract

Effects of phenethyl isothiocyanate (PEITC) have been investigated in human leukemia cells (U937, Jurkat, and HL-60) as well as in primary human acute myeloid leukemia (AML) cells in relation to apoptosis and cell signaling events. Exposure of cells to PEITC resulted in pronounced increase in the activation of caspase-3, -8, -9, cleavage/degradation of PARP, and apoptosis in dose- and time-dependent manners. These events were accompanied by the caspase-independent downregulation of Mcl-1, inactivation of Akt, as well as activation of Jun N-terminal kinase (JNK). Inhibition of PI3K/Akt by LY294002 significantly enhanced PEITC-induced apoptosis. Conversely, enforced activation of Akt by a constitutively active Akt construct markedly abrogated PEITC-mediated JNK activation, Mcl-1 downregulation, caspase activation, and apoptosis, and also interruption of the JNK pathway by pharmacological or genetically (e.g., siRNA) attenuated PEITC-induced apoptosis. Finally, administration of PEITC markedly inhibited tumor growth and induced apoptosis in U937 xenograft model in association with inactivation of Akt, activation of JNK, as well as downregulation of Mcl-1. Taken together, these findings represent a novel mechanism by which agents targeting Akt/JNK/Mcl-1 pathway potentiate PEITC lethality in transformed and primary human leukemia cells and inhibitory activity of tumor growth of U937 xenograft model.

Highlights

(PEITC) is one of the ITC family of compounds that has attracted a great deal of attention owing to its remarkable cancer chemopreventive activity.[2]
This study provides experimental evidence to indicate, for the first time, that the cell death caused by PEITC is initiated by the inactivation of Akt, leading, in turn, to Jun N-terminal kinase (JNK) activation, and culminating in Mcl-1 downregulation
A dose-dependent study of U937 cells exposed to various concentrations of PEITC for 3 and 6 h was shown in Figure 1a; modest degrees of apoptosis were noted at 4 mM PEITC concentration, which increased substantially at concentration of 6 mM

Summary

Introduction

(PEITC) is one of the ITC family of compounds that has attracted a great deal of attention owing to its remarkable cancer chemopreventive activity.[2]. Chen et al.[9] have reported that apoptosis induction by PEITC is in association with sustained activation of c-Jun NH2-terminal kinase in Jurkat cells. This study provides experimental evidence to indicate, for the first time, that the cell death caused by PEITC is initiated by the inactivation of Akt, leading, in turn, to Jun N-terminal kinase (JNK) activation, and culminating in Mcl-1 downregulation. We show that administration of PEITC significantly inhibits the tumor growth of U937 xenografts in SCID mice in association with inactivation of Akt, activation of JNK, as well as induction of apoptosis

Methods

Results

Conclusion