A novel AML1-ETO/FTO positive feedback loop promotes leukemogenesis and Ara-C resistance via stabilizing IGFBP2 in t(8;21) acute myeloid leukemia.

Background: t(8;21)(q22;q22) is one of the most frequent chromosomal abnormalities in acute myeloid leukemia (AML), leading to the generation of the fusion protein AML1-ETO. Despite t(8;21) AML being considered as a subtype with a favorable prognosis, approximately 30-50% of patients experience drug resistance and subsequent relapse. N-methyladenosine (mA) is demonstrated to be involved in the development of AML. However, the regulatory mechanisms between AML1-ETO and mA-related enzymes and the roles of dysregulated mA modifications in the t(8;21)-leukemogenesis and chemoresistance remain elusive.

Methods: Chromatin immunoprecipitation, dual-luciferase reporter assay, mA-qPCR, RNA immunoprecipitation, and RNA stability assay were used to investigate a regulatory loop between AML1-ETO and FTO, an mA demethylase. Gain- and loss-of-function experiments both in vitro and in vivo were further performed. Transcriptome-wide RNA sequencing and mA sequencing were conducted to identify the potential targets of FTO.

Results: Here we show that FTO is highly expressed in t(8;21) AML, especially in patients with primary refractory disease. The expression of FTO is positively correlated with AML1-ETO, which is attributed to a positive regulatory loop between the AML1-ETO and FTO. Mechanistically, AML1-ETO upregulates FTO expression through inhibiting the transcriptional repression of FTO mediated by PU.1. Meanwhile, FTO promotes the expression of AML1-ETO by inhibiting YTHDF2-mediated AML1-ETO mRNA decay. Inactivation of FTO significantly suppresses cell proliferation, promotes cell differentiation and renders resistant t(8;21) AML cells sensitive to Ara-C. FTO exerts functions by regulating its mRNA targets, especially IGFBP2, in an mA-dependent manner. Regain of Ara-C tolerance is observed when IGFBP2 is overexpressed in FTO-knockdown t(8;21) AML cells.

Conclusion: Our work reveals a therapeutic potential of targeting AML1-ETO/FTO/IGFBP2 minicircuitry in the treatment for t(8;21) patients with resistance to Ara-C.