Circadian clock protein Bmal1 accelerates acute myeloid leukemia by inhibiting ferroptosis through the EBF3/ALOX15 axis

Abstract

Acute myeloid leukemia (AML) is a major leukemia with high mortality. Ferroptosis is an important regulator of cancers. However, the role of ferroptosis and its regulatory mechanisms in AML remain largely unknown. In this study, we reported elevated brain and muscle ARNT-Like protein-1 (Bmal1) expression in AML patients and cell lines, and its upregulation indicated the poor survival of patients. The correlation analysis showed that Bmal1 expression was closely correlated with cytogenetics and the French-American-British subtypes, but was not correlated with age, gender and white blood cells. RSL3 reduced Bmal1 expression in HL-60 and NB4 cells. Malondialdehyde, total iron, Fe²⁺ , glutathione and lipid peroxidation were examined to evaluate ferroptosis. Overexpression of Bmal1 repressed RSL3-induced ferroptosis in AML cells. Bmal1 recruited Enhancer of zeste homolog 2 (EZH2) to the Early B cell factor 3 (EBF3) promoter and enhanced its methylation, thus suppressing EBF3 expression. Moreover, the knockdown of Bmal1 sensitized AML cells to RSL3-induced ferroptosis, and it was counteracted by EBF3 knockdown. Furthermore, EBF3 bound to the Arachidonate 15-pipoxygenase (ALOX15) promoter to enhance its expression, and overexpression of EBF3 enhanced RSL3-induced ferroptosis dependent on ALOX5. We established a subcutaneous AML xenograft tumor model and reported that knockdown of Bmal1 and overexpression of EBF3 restrained AML growth by promoting ALOX15-mediated ferroptosis in vivo. Collectively, Bmal1 inhibits RSL3-induced ferroptosis by promoting EZH2-mediated EBF3 methylation and suppressing the expression of EBF3 and ALOX15, thus accelerating AML.

Keywords: ALOX15; Bmal1; EBF3; acute myeloid leukemia; ferroptosis.