Z-Ligustilide Selectively Targets AML by Restoring Nuclear Receptors Nur77 and NOR-1-mediated Apoptosis and Differentiation

Abstract

Background: Acute myeloid leukemia (AML) is a devastating hematologic malignancy with a high mortality. The nuclear receptors Nur77 and NOR-1 are commonly downregulated in human AML blasts and have emerged as key therapeutic targets for AML.

Methods: This study aimed to identify Z-ligustilide (Z-LIG), the main phthalide of Rhizoma Chuanxiong, as a potential agent that can selectively target AML. The anti-AML activity of Z-LIG was evaluated in vitro and in vivo, and the effect and underlying mechanisms of Z-LIG on the restoration of Nur77 and NOR-1 was determined. Moreover, the role of Nur77 and NOR-1 in the regulation of Z-LIG-induced apoptosis and differentiation of AML cells was explored.

Results: Z-LIG preferentially inhibited the viability of human AML cells, as well as suppressed the proliferation and colony formation ability. Notably, a concentration-dependent dual effect of Z-LIG was observed in AML cells: inducing apoptosis at relatively high concentrations (25 μM to 100 μM) and promoting differentiation at relatively low concentrations (10 μM and 25 μM). Importantly, Z-LIG restored Nur77 and NOR-1 expression in AML cells by increasing Ace-H3 (lys9/14) enrichment in their promoters. Meanwhile, Z-LIG enhanced the recruitment of p300 and reduced the recruitment of HDAC1, HDAC4/5/7, and MTA1 in the Nur77 promoter and enhanced the recruitment of p-CREB and reduced HDAC1 and HDAC3 in the NOR-1 promoter. Furthermore, Z-LIG-induced apoptosis was shown to be correlated with the mitochondria localization of Nur77/NOR-1 and subsequent Bcl-2 conformational change, converting Bcl-2 from a cyto-protective phenotype into a cyto-destructive phenotype. Z-LIG-promoted differentiation was found to be related to Nur77/NOR-1-mediated myeloid differentiation-associated transcription factors Jun B, c-Jun, and C/EBPβ. Finally, silencing of Nur77 and NOR-1 attenuated anti-AML activity of Z-LIG in NOD/SCID mice.

Conclusions: Our study suggests that Z-LIG may serve as a novel bifunctional agent for AML by restoring Nur77/NOR-1-mediated apoptosis and differentiation.

Keywords: Acute myeloid leukemia; Apoptosis; Differentiation; NOR-1; Nur77; Z-ligustilide.