Mutant C/EBPα p30 alleviates immunosuppression of CD8+ T cells by inhibiting autophagy-associated secretion of IL-1ß in AML.

OBJECTIVES: Mutant C/EBPα p30 (mp30), the product of C/EBPα double mutations (DM), lacks transactivation domain 1 and has C-terminal loss-of-function mutation. Acute myeloid leukaemia (AML) patients harbouring C/EBPα DM could be classified as a distinct subgroup with favourable prognosis. However, the underlying mechanism remains elusive. MATERIALS AND METHODS: Autophagy regulated by mp30 was detected by western blot and immunofluorescence. Immune infiltration analysis and GSEA were performed to investigate autophagic and inflammatory status of AML patients from the GSE14468 cohort. Flow cytometry was applied to analyse T cell activation. RESULTS: Mp30 inhibited autophagy by suppressing nucleus translocation of NF-κB. Autophagy-associated secretion of IL-1ß was decreased in mp30-overexpressed AML cells. Bioinformatic analysis revealed that inflammatory status was attenuated, while CD8+ T cell infiltration was upregulated in C/EBPα DM AML patients. Consistently, the proportion of CD8+ CD69+ T cells in peripheral blood mononuclear cells (PBMCs) was upregulated after co-culture with mp30 AML cell conditional culture medium. Knock-out of IL-1ß in AML cells also enhanced CD8+ T cell activation. Accordingly, IL-1ß expression was significantly reduced in the bone marrow (BM) cells of C/EBPα DM AML patients compared to the wildtype, while the CD8+ CD69+ T cell proportion was specifically elevated. CONCLUSIONS: C/EBPα DM alleviates immunosuppression of CD8+ T cells by inhibiting the autophagy-associated secretion of IL-1ß, which elucidated that repression of autophagy-related inflammatory response in AML patients might achieve a favourable clinical benefit.

Aurora kinase inhibitor restrains STAT5-activated leukemic cell proliferation by inducing mitochondrial impairment.

Current chemotherapy regimens on acute myeloid leukemia (AML) still have some drawbacks, such as intolerance and drug resistance, which calls need for the development of targeted therapy. Signal transducer and activator of transcription 5 (STAT5) is often overexpressed or abnormally activated in leukemia and involved in cell self-renewal, proliferation, and stress adaptation. Overexpressed Aurora A (AURKA) is associated with poor prognosis in tumors, and inhibitors against AURKA are already in clinical trials. However, it has rarely been reported whether AURKA inhibitors restrain STAT5-activated leukemia cells. In this study, we constructed STAT5 constitutively activated (cS5) cells and found that STAT5 promoted cell proliferation and colony formation. Moreover, cS5 cells showed elevated reactive oxygen species (ROS) and adenosine triphosphate (ATP) levels, which indicated higher mitochondrial metabolism in cS5 cells. A novel AURKA inhibitor AKI604 was synthesized and showed significant inhibitory effects to the proliferation and colony formation in both STAT5 constitutively activated and nonactivated AML cells. AKI604 induced mitochondrial impairment, leading to the disruption of mitochondrial membrane potential and the elevation of ROS as well as cellular calcium (Ca2+ ) levels. AKI604 could also decline basal oxygen consumption rate and ATP biosynthesis, indicating the damage of oxidative phosphorylation. Furthermore, AKI604 exhibited significant antitumor effect in the HL-60 cS5 xenograft model of the BALB/c nude mice without an obvious influence on mice body weight and other healthy indicators. This study suggested that AKI604 was a potential strategy to overcome STAT5-induced leukemic proliferation in AML treatment by inducing mitochondrial impairment.