Downregulation of circular RNA hsa_circ_0001649 indicates poor prognosis for retinoblastoma and regulates cell proliferation and apoptosis via AKT/mTOR signaling pathway

Retinoblastoma (RB) is the most common intraocular malignancy in infants and children with high mortality rate in developing countries. Emerging evidence demonstrated that abnormally expressed circular RNAs (circRNAs) are involved in tumorigenesis and progression in several malignancies. However, their clinical values, biological functions and mechanisms in RB has not been reported before. Recently, hsa_circ_0001649 was found to play imperative roles in cholangiocarcinoma, gastric cancer, and hepatocellular carcinoma. In the current study, qRT-PCR was performed to detect the expression of hsa_circ_0001649 in RB samples and cells. The correlations between hsa_circ_0001649 expression and clinicopathologic characteristics were further analyzed. In addition, we up-regulated hsa_circ_0001649 in Y79 cells and knocked down hsa_circ_0001649 in WERI-Rbl cells to explore its effect on cell proliferation and apoptosis. The animal study was performed to confirm the in vitro results. Furthermore, AKT/mTOR signaling pathway was detected to clarify the molecular mechanisms of hsa_circ_0001649 exerts in RB cell growth. The results indicated that hsa_circ_0001649 was decreased in RB tissues and cells, and this downregulation was associated with larger tumor size and advanced intraocular international retinoblastoma classify (IIRC) stage in RB patients. Additionally, hsa_circ_0001649 could act as an independent prognostic predictor for overall survival in patients with RB. Moreover, hsa_circ_0001649 inhibits cell growth and promotes cell apoptosis in RB cells. AKT/mTOR signaling pathway is involved in the cell growth alteration affected by hsa_circ_0001649. Overall, hsa_circ_0001649 might be a potentially useful prognostic biomarker and therapeutic target for RB.