MicroRNA-9 suppresses cancer proliferation and cell cycle progression in acute lymphoblastic leukemia with inverse association of neuropilin-1

Acute lymphoblastic leukemia (ALL) is one of the most common and most malign childhood cancers. In this work, we investigated the expression and function of human mature microRNA-9 (miR-9) in ALL. In ALL in vitro cell lines and in situ clinical specimens, gene expression of miR-9 was tested by qRT-PCR. MiR-9 was overexpressed in CEM/C1 and Molt-3 cells to investigate its possible anti-cancer effects on ALL in vitro proliferation, cell-cycle progression, and in vivo explant growth. The possible downstream target of miR-9, neuropilin-1 (NRP1), was examined by dual-luciferase activity assay, qRT-PCR, and Western blot. NRP1was upregulated in miR-9-overexpressed CEM/C1 and Molt-3 cells to investigate the functional involvement of NRP1 in miR-9-mediated regulation on ALL in vitro proliferation and cell-cycle progression. MiR-9 was downregulated in ALL cell lines and leukemic T-cells of ALL patients. Lentivirus-mediated miR-9 overexpression inhibited ALL in vitro proliferation, cell-cycle progression, and in vivo explant growth. NRP1 was confirmed be the downstream target of miR-9, and inversely modulated by miR-9 in ALL. NRP1 upregulation reversed the anti-cancer regulations of miR-9 on ALL in vitro proliferation and cell-cycle progression. MiR-9 is downregulated in ALL. Overexpressing miR-9 may inhibit ALL development, possible through its downstream target of NRP1.