Fat Mass and Obesity-Associated Protein-Mediated Adipogenic Differentiation of Bone Marrow Mesenchymal Stem Cells Promotes Chemotherapy Resistance in Acute Myeloid Leukemia.

BACKGROUND: Chemotherapy resistance and relapse in acute myeloid leukemia (AML) are associated with poor prognosis. Bone marrow mesenchymal stem cells (MSCs) show enhanced adipogenic differentiation in AML, which may contribute to chemoresistance; however, the underlying mechanisms remain incompletely understood. AIMS: To investigate how adipogenic differentiation of MSCs from chemotherapy-resistant AML patients (CR-AML-MSCs) promotes chemoresistance, focusing on the roles of the fat mass and obesity-associated protein (FTO) and the mTORC1 pathway. STUDY DESIGN: Experimental study. METHODS: This study compared bone marrow MSCs from chemotherapy-sensitive (CS) and CR AML patients. Adipogenic differentiation was assessed using Oil Red O staining. RNA sequencing, Quantitative real-time PCR (qPCR), and western blotting were employed to analyze expression of FTO, Raptor, and PPARγ. Global N6-methyladenosin (m6A) levels were measured, and co-culture models with AML cell lines (U937, HL-60, THP-1) were established to evaluate chemoresistance. Gain- and loss-of-function experiments for FTO were performed using lentiviral overexpression and shRNA knockdown. mTORC1 pathway involvement was tested using rapamycin. Statistical analyses included t-tests and ANOVA, with significance set at (p < 0.05). MSCs from CS and resistant AML patients were compared. Adipogenic differentiation was induced and assessed by Oil Red O staining. RNA sequencing, qPCR, and western blotting were used to analyze the expression of FTO, Raptor, and PPARγ. Global m6A levels were measured, and co-culture models with AML cell lines (U937, HL-60, THP-1) were established to evaluate chemoresistance. Gain- and loss-of-function experiments for FTO were performed. RESULTS: CR-AML-MSCs exhibited significantly enhanced adipogenic differentiation (p < 0.01) and elevated PPARγ expression. Co-culture with adipocyte-differentiated CR-AML-MSCs markedly increased resistance to daunorubicin and cytarabine in AML cells (p < 0.01). RNA-Seq analysis revealed enrichment of the mTORC1 signaling pathway and upregulation of raptor. Inhibition of mTORC1 with rapamycin suppressed adipogenic differentiation. Total m(6)A levels were reduced in CR-AML-MSCs, whereas FTO expression was increased. Overexpression of FTO further promoted adipogenesis, upregulated raptor and PPARγ, and enhanced chemoresistance, whereas FTO knockdown attenuated these effects. CONCLUSION: FTO enhances adipogenic differentiation of CR-AML-MSCs through m(6)A demethylation of raptor, leading to mTORC1 pathway activation and subsequent chemoresistance. These findings reveal a novel mechanism underlying AML chemoresistance and suggest potential therapeutic targets.