ABSTRACT: Purpose:Pediatric acute promyelocytic leukemia (APL) accounts for 10% of pediatric acute myelogenous leukemia (AML) case and is accompanied by a tendency to hemorrhage. miR-188-5p plays an important role in adult AML. Therefore, the purpose of this study was to explore the effects of miR-188-5p on cell proliferation and apoptosis and tumor growth, and its mechanism in pediatric APL patients. Materials and Methods:Survival-associated miRNAs or mRNAs from TCGA database associated with AML were identified via using the "survival R" package in R language. CCK8, clone formation, flow cytometry, RT-PCR, immunohistochemistry and Western blot assays were used to detect the viability, proliferation, apoptosis, cell cycle, and related gene expression in APL cell lines. The prognostic value of miR-188-5p was evaluated using a ROC curve. The tumorigenic ability of APL cell lines was determined using a nude mouse transplantation tumor experiment. Tumor cell apoptosis was determined by TUNEL assay in vivo. The target genes of miR-188-5p were predicted using the miRDB, miRTarBase, and TargetScan databases. A PPI network was constructed using STRING database and the hub gene was identified using the MCODE plug-in of the Cytoscape software. The DAVID database was used to perform GO and KEGG pathway enrichment analyses. A luciferase reporter assay was used to demonstrate the binding of miR-188-5p to CD2AP. Results:miR-188-5p overexpression or CD2 associated protein (CD2AP) inhibition was significantly associated with poor survival in pediatric APL patients. Upregulation of miR-188-5p was identified in the blood of pediatric APL patients and cell lines. Increased expression of miR-188-5p also promoted the viability, proliferation, and cell cycle progression, and reduced the apoptosis of APL cells. Additionally, upregulation of miR-188-5p regulated the expressions of cyclinD1, p53, Bax, Bcl-2 and cleaved caspase-3. The area under the ROC curve (AUC) of miR-188-5p was 0.661. miR-188-5p overexpression increased the tumorigenic ability of APL and Ki67 expression, and reduced cell apoptosis in vivo. CD2AP was identified as the only overlapping gene from the list of miR-188-5p target genes and survival-related mRNAs of the TCGA database. It was mainly enriched in the "biological process (BP)" and "cellular component (CC)" terms, and was downregulated in the blood of pediatric APL patients and cell lines. The luciferase reporter, RT-PCR, and Western blot assays demonstrated that the binding of miR-188-5p to CD2AP. CD2AP inhibition promoted the proliferation and inhibited the apoptosis of APL cells. Rescue experiments showed that inhibition of miR-188-5p inhibited cell proliferation, activated the PI3K/AKT/mTOR signaling pathway, induced G0/G1 phase arrest, regulated gene expression, and promoted cell apoptosis, which were reversed by CD2AP inhibition. Conclusion:miR-188-5p, an oncogene, promoted tumor growth and progression of pediatric APL in vitro and in vivo via targeting CD2AP and activating the PI3K/AKT/mTOR signaling pathway.
