CLPs-miR-103a-2-5p inhibits proliferation and promotes cell apoptosis in AML cells by targeting LILRB3 and Nrf2/HO-1 axis, regulating CD8 + T cell response.

BACKGROUND: LILRB3, a member of the leukocyte immunoglobulin-like receptor B (LILRB) family, has immunosuppressive functions and directly regulates cancer development, which indicates that LILRB3 is an attractive target for cancer diagnosis and therapy. Novel therapeutic treatments for acute myeloid leukemia (AML) are urgent and important, and RNA therapeutics including microRNAs (miRNAs) could be an effective option. Here, we investigate the role of dysregulated miRNA targeting LILRB3 in the AML microenvironment.

METHODS: Potential miRNAs binding to the 3'-untranslated region (3'-UTR) of the LILRB3 mRNA were predicted by bioinformatics websites. Then, we screened miRNAs targeting LILRB3 by quantitative real-time PCR, and the dual luciferase reporter assay. The expression of LILRB3 and microRNA (miR)-103a-2-5p in AML were determined and then their interactions were also analyzed. In vitro, the effects of miR-103a-2-5p were determined by CCK8, colony formation assay, and transwell assay, while cell apoptosis and cell cycle were analyzed by flow cytometry. Cationic liposomes (CLPs) were used for the delivery of miR-103a-2-5p in the AML mouse model, which was to validate the potential roles of miR-103a-2-5p in vivo.

RESULTS: LILRB3 was upregulated in AML cells while miR-103a-2-5p was dramatically downregulated. Thus, a negative correlation was found between them. MiR-103a-2-5p directly targeted LILRB3 in AML cells. Overexpressed miR-103a-2-5p significantly suppressed the mRNA and protein levels of LILRB3, thereby inhibiting AML cell growth and reducing CD8 + T cell apoptosis. In addition, overexpressed miR-103a-2-5p reduced both the relative expression of Nrf2/HO-1 pathway-related proteins and the ratio of GSH/ROS, leading to the excessive intracellular ROS that may promote AML cell apoptosis. In the mouse model, the delivery of miR-103a-2-5p through CLPs could inhibit tumor growth.

CONCLUSIONS: MiR-103a-2-5p serves as a tumor suppressor that could inhibit AML cell proliferation and promote their apoptosis by downregulating LILRB3 expression, suppressing the Nrf2/HO-1 axis, and reducing the ratio of GSH/ROS. Besides, our findings indicate that miR-103a-2-5p may enhance the CD8 + T cell response by inhibiting LILRB3 expression. Therefore, the delivery of miR-103a-2-5p through CLPs could be useful for the treatment of AML.