3, 3′-Diindolylmethane Exhibits Antileukemic Activity In Vitro and In Vivo through a Akt-Dependent Process

Ning Gao,Jieping Chen,Zailin Yang,Senping Cheng,E-Hu Liu,Deying Chen,Xianglin Shi,Zhuo Zhang,Amit Budhraja,Jia Luo,Kevin D Bunting

doi:10.1371/journal.pone.0031783

Ning Gao, Jieping Chen + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0031783

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Journal: PloS one	Publication Date: Feb 21, 2012
Citations: 59	License type: CC BY 4.0

Affiliation: Southern Medical University, University of Kentucky

Abstract

3,3′-diindolylmethane (DIM), one of the active products derived from Brassica plants, is a promising antitumor agent. The present study indicated that DIM significantly induced apoptosis in U937 human leukemia cells in dose- and time-dependent manners. These events were also noted in other human leukemia cells (Jurkat and HL-60) and primary human leukemia cells (AML) but not in normal bone marrow mononuclear cells. We also found that DIM-induced lethality is associated with caspases activation, myeloid cell leukemia-1 (Mcl-1) down-regulation, p21cip1/waf1 up-regulation, and Akt inactivation accompanied by c-jun NH2-terminal kinase (JNK) activation. Enforced activation of Akt by a constitutively active Akt construct prevented DIM-mediated caspase activation, Mcl-1 down-regulation, JNK activation, and apoptosis. Conversely, DIM lethality was potentiated by the PI3K inhibitor LY294002. Interruption of the JNK pathway by pharmacologic or genetic approaches attenuated DIM-induced caspases activation, Mcl-1 down-regulation, and apoptosis. Lastly, DIM inhibits tumor growth of mouse U937 xenograft, which was related to induction of apoptosis and inactivation of Akt, as well as activation of JNK. Collectively, these findings suggest that DIM induces apoptosis in human leukemia cell lines and primary human leukemia cells, and exhibits antileukemic activity in vivo through Akt inactivation and JNK activation.

Highlights

Epidemiological studies have revealed an association between high dietary intake of cruciferous vegetables and decreased cancer risk [1]
The present study shows that exposure of U937 human leukemia cells resulted in increase in apoptosis in dose- and time-dependent manners
Our results provide mechanistic information, for the first time, how DIM exerts its proapoptotic effects on human leukemia cells

Summary

Introduction

Epidemiological studies have revealed an association between high dietary intake of cruciferous vegetables and decreased cancer risk [1]. In MCF-7 human breast cancer cells, DIM induced G1 cell cycle arrest through up-regulation of p21, and the oxidative stress and stress-activated signaling cascades including p38 MAPK and JNK play the key roles in these events [21]. It has been shown that DIM induced apoptosis through inactivation of NF-kB in human breast cancer cells [22]. In human prostate cancer cells, DIM inhibited cell proliferation and induced apoptosis through down-regulation of AR, Akt, and NFkB signaling [24]. Our results indicate that inactivation of Akt and activation of JNK play important roles in DIM-mediated apoptosis in these cells. Our results indicate that DIM inhibits growth of mouse U937 xenograft tumors, and the interruptions of the Akt and JNK pathways are involved in DIM-mediated antileukemic activity in vivo

Results

Discussion

Materials and Methods