The Long Noncoding RNA MALAT1/microRNA-598-3p Axis Regulates the Proliferation and Apoptosis of Retinoblastoma Cells Through the PI3K/AKT Pathway

Purpose: This study was designed to dissect the role of long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in retinoblastoma (RB) and its underlying mechanism.

Methods: Gain- and loss-of-function experiments were adopted to explore the effects of MALAT1 and microRNA (miR)-598-3p on the biologic behaviors of RB cells. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to assess the expression of MALAT1 and miR-598-3p in Y79 and HXO-RB44 cells. The proliferation of RB cells was determined with the cell counting kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) staining. Flow cytometry was employed for the measurement of the apoptotic rate, western blotting for examination of the expression of apoptosis-related proteins (Bax and Bcl-2) and phosphoinositide 3-kinase/protein kinase-B (PI3K/AKT) pathway-related factors (PI3K, AKT, p-PI3K, and p-AKT), and the luciferase reporter assay for assessment of the interaction between MALAT1 and miR-598-3p.

Results: High expression of MALAT1 and low expression of miR-598-3p were noticed in Y79 and HXO-RB44 cells. MALAT1 upregulation or miR-598-3p downregulation facilitated RB cell proliferation and inhibited cell apoptosis, as evidenced by the increased proliferation rate and Bcl-2 expression, as well as diminished Bax expression and apoptotic rate, in the RB cells after transfection with pcDNA3.1-MALAT1 or miR-598-3p inhibitor. MALAT1 bound to and negatively regulated miR-598-3p. The PI3K/AKT pathway activation occurred with MALAT1 overexpression. MALAT1 promoted RB cell proliferation and repressed cell apoptosis by repressing miR-598-3p to activate the PI3K/AKT pathway.

Conclusions: MALAT1 repressed miR-598-3p to activate the PI3K/AKT pathway, thus facilitating cell proliferation and inhibiting cell apoptosis in RB.