Let-7b inhibits the development of AML through inducing repolarization of leukemia-associated macrophages

JIANG Tianyou; LI Min; SUN Biwen; LI Yueyang; XING Lijing; TIAN Chen

doi:10.11958/20252591

Abstract：Objective To study the mechanism of let-7b regulating acute myeloid leukemia(AML)by leukemia-associated macrophages(LAMs).Methods Bone marrow cells were collected from AML patients prior to any treatment and cryopreserved.Patients subsequently received induction chemotherapy with the"DA 3+7"regimen,and therapeutic responses were evaluated post-treatment.According to the efficacy assessment results,patients were stratified into two groups:the complete remission(CR)group and the non-complete remission(refractory)group.AML blasts of pre-cryopreserved patients were then respectively transplanted into NOD/SCID mice to establish AML xenograft mouse model corresponding to the CR group and the refractory group.After miRNA sequencing and polymerase chain reaction(PCR)verification,let-7b was selected as the target gene to investigate its role in MLL-AF9-induced AML.Transfection of LAMs in MLL-AF9-induced AML mice with let-7b shRNA or scramble control was validated by quantitative real-time PCR(RT-qPCR),Western blot assay and enzyme-linked immunosorbent assay(ELISA)in vitro and in vivo experiments.Results Compared with the AML CR group,the apoptosis rate of LAM cells was lower in the AML refractory group.Furthermore,let-7b was a potentially aberrant gene in LAMs contributing to M2-subtype characteristics.Knockdown of let-7b in LAMs could inhibit the development of AML by repolarizing LAMs toward M1-subtype characteristics through the activation of Toll-like receptor and NF-κB pathway.The results of in vivo experiments showed that knockdown of let-7b in LAMs inhibited the proliferation of leukemia cells and decreased infiltration into spleen,thereby inhibiting the progression of AML.Conclusion Let-7b interference in LAMs can activate Toll-like receptors(TLRs)and NF-κB pathway,promote the repolarization of LAMs to M1 macrophages,thereby inhibiting the development of AML.