The cell-nonautonomous function of ID1 supports AML progression from the microenvironment via ANGPLT7

Bone marrow microenvironment (BMM) can maintain and regulate HSC and LSC via secreted components or direct interaction. Increasing evidence indicates that dissecting and targeting BMM-driven mechanisms of LSC might provide key adjuvant therapies to eradicate leukemia. ID1, a key transcriptional regulator in LSC previously identified by us, controls cytokine/chemokine production in the BMM, but the role of ID1 in AML-BMM remains obscure. Here, we report that ID1 is highly expressed in AML-BMM, especially in bone marrow mesenchymal stem cell (BMSC), and deletion of Id1 in BMM resulted in impaired AML progression in AML mouse model. Mechanistically, we found that Id1 deficiency markedly reduced the protein level of SP1 in mesenchymal cells co-cultured with AML cells. Through Id1-interactome analysis, we discovered Id1 interacts with Rnf4, the ubiquitin E3 ligase, and led to decreased Sp1 degradation. Disrupting ID1-RNF4 interaction by truncates in mesenchymal cells significantly decreased SP1 protein level and retarded the AML cell proliferation. We identified the target of Sp1, Angptl7, was the primary differentially expression protein factor in Id1-/- bone marrow supernatant fluid (BMSF) to regulate AML progression in mice. Taken together, our study highlights the critical role of ID1 in AML-BMM and assists development of diagnostic/therapeutic strategies for AML. To evaluate the non-cell-autonomous function of Id1 on LICs in vivo, we employed an AML1-ETO9a(AE9a)/MLL-AF9 driven AML mouse transplantation model. After 6 weeks transplantation, Id1+/+ and Id1-/- mouse BMSC were harvested and cultured in a-MEM supplemented with 10% FBS. After the adherent MSCs are seen under the microscope, the total RNA is extracted. RNA-seq library prepared and sequenced by novogene, Beijing, China.