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Introduction
Retinoblastoma (RB) is the most common malignant neural retinal intraocular tumor of childhood, affecting one out of 16,000-18,000 neonates (Mansoor et al., 2016; Villegas et al., 2013). RB is curable at the early stage, and the survival rates of the patients with early stage RB are nearly 100% (Broaddus et al., 2009). However, the survival rates are dramatically declined in undeveloped countries or regions, only 20-46% in Africa (Bowman et al., 2008) due to delayed diagnosis and treatment (Dimaras et al., 2010). The advanced RB can grow into the periocular tissues and finally into the brain, and even metastases to distant organs leading to death (Villegas et al., 2013). Although some treatments have been developed to benefit RB patients, the prognosis in the advanced RB is still poor (Sengupta et al., 2016). Thus, it is urgent to discover new effective therapeutic targets.
Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) are two classes of important RNA regulators engaged in cancer development (Ayers and Vandesompele, 2017). LncRNAs are a kind of RNAs more than 200 nucleotides in length that do not encode proteins (Quinn and Chang, 2016). LncRNAs regulate multiple biological processes, including cell proliferation, tumorigenesis and metastasis (Wang and Chang, 2011). For instance, lncRNA BANCR is involved in RB cell growth and metastasis, and its higher levels are related to poor prognosis in RB (Su et al., 2015). RB development is regulated by lncRNA BDNF-AS (Shang et al., 2018). MiRNAs are small RNAs with a length of 21-25 nucleotides and inhibit gene expression by either degrading the targeted transcripts or inhibiting translation of the targeted mRNAs. One approach of lncRNA exerting its functions is to sponge miRNAs and down-regulate their levels, that in turn up-regulates the expression levels of miRNA-targeted genes (Quinn and Chang, 2016). For example, lncRNA MALAT1 elevates Slug expression via miR-124 to modulate RB cell proliferation, migration and invasion (Liu et al., 2017). H19 directly binds miR-17-92 to de-suppress p21 expression, and consequently prevents RB progression (Zhang et al., 2018a). LINC00202 is a lncRNA related to poor prognosis in RB. It has been reported that it is also associated with overall survival (OS) time in patients with renal cancer (Liu et...