Long noncoding RNA LINC00324 promotes retinoblastoma progression by acting as a competing endogenous RNA for microRNA-769-5p, thereby increasing STAT3 expression

Long intergenic non-protein-coding RNA 324 (LINC00324) is abnormally expressed in multiple human cancer types and plays an important role in cancer initiation and progression. This study showed that LINC00324 was expressed at higher levels in retinoblastoma (RB) tumors and cell lines than in control samples. Increased LINC00324 expression closely correlated with the TNM stage, optic nerve invasion, and shorter overall survival among patients with RB. The knockdown of LINC00324 decreased RB cell proliferation, colony formation, migration, and invasion, and promoted apoptosis and cell cycle arrest in vitro as well as hindered tumor growth in vivo. With respect to the mechanism, LINC00324 acted as a competing endogenous RNA for microRNA-769-5p (miR-769-5p) in RB cells. The mRNA of signal transducer and activator of transcription 3 (STAT3) was identified as a direct target of miR-769-5p in RB cells. Rescue experiments indicated that restoration of STAT3 expression attenuated the tumor-suppressive actions of miR-769-5p in RB cells. Downregulation of miR-769-5p or restoration of STAT3 almost completely reversed the effects of LINC00324 knockdown on RB cells. Our findings describe a novel RB-related LINC00324-miR-769-5p-STAT3 axis that is implicated in the malignancy of RB in vitro and in vivo. This study may point to innovative therapeutic targets in RB.