Purpose: Circular RNAs (circRNAs) are essential regulators in tumorigenesis and development. In this study, we focused on the functions of circRNA muskelin 1 (circMKLN1) in retinoblastoma (RB) progression.Materials and Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) assay was conducted to determine the levels of circMKLN1, microRNA-425-5p (miR-425-5p) and programmed cell death 4 (PDCD4). The characteristic of circMKLN1 was analyzed using RNase R assay. Cell Counting Kit-8 (CCK-8) assay and colony formation assay were employed to explore cell proliferation ability. The transwell assay was utilized for cell migration and invasion. A Western blot assay was performed for protein levels. The dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to demonstrate the relationships among circMKLN1, miR-425-5p and PDCD4. Murine xenograft model assay was adopted to investigate the role of circMKLN1 in vivo.Results: CircMKLN1 was downregulated in RB tissues and cells. High levels of circMKLN1 were related to a favorable outcome of RB patients. CircMKLN1 was resistant to RNase R digestion and circMKLN1 overexpression repressed RB cell proliferation, migration and invasion in vitro. MiR-425-5p was identified as the target of circMKLN1 and miR-425-5p elevation reversed the effects of circMKLN1 overexpression on RB cell malignant behaviors. Furthermore, as the target gene of miR-425-5p, PDCD4 silencing could ameliorate the suppressive roles of circMKLN1 in RB cell growth and metastasis. Additionally, circMKLN1 overexpression hampered tumor growth in vivo.Conclusions: CircMKLN1 overexpression decelerated the progression of RB through sponging miR-425-5p and elevating PDCD4.
Keywords: PDCD4; RB; circMKLN1; miR-425-5p.