Objective: This study aims to elucidate the regulatory effect of long non-coding RNA (lncRNA) FAL1 on the tumorigenesis of oral squamous cell carcinoma (OSCC), and to explore its underlying mechanism.
Materials and methods: Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed to detect the expression levels of lncRNA FAL1, microRNA-761 and CRKL in 20 pairs of OSCC tissues and adjacent normal oral tissues. Meanwhile, their expressions in OSCC cell lines were also determined by qRT-PCR. The protein expression of CRKL in OSCC tissues was detected by Western blot. The cell counting kit-8 (CCK-8) assay was performed to access the proliferation of SCC25 and HN4 cells transfected with si-FAL1. The binding conditions between lncRNA FAL1 with microRNA-761, and microRNA-761 with CRKL were tested by the Dual-Luciferase reporter gene assay. Gain-of-function experiments were conducted to determine the proliferation of OSCC cells co-transfected with si-FAL1 and microRNA-761 inhibitor. Furthermore, the proliferative potential of OSCC cells was evaluated after co-transfection of si-FAL1 and CRKL overexpression plasmid.
Results: LncRNA FAL1 was highly expressed in OSCC tissues and cell lines. The proliferative capacity of OSCC cells was significantly inhibited by lncRNA FAL1 knockdown. The mRNA expression of microRNA-761 was lowly expressed in OSCC tissues and cell lines. Dual-Luciferase reporter gene assay showed that lncRNA FAL1 directly bound to microRNA-761. Meanwhile, microRNA-761 expression was negatively regulated by FAL1. CRKL was verified as the target gene of microRNA-761. Both the mRNA and protein levels of CRKL were remarkably upregulated in OSCC tissues and cell lines. CRKL expression was found to be negatively regulated by microRNA-761 in OSCC cells. Lowly expressed microRNA-761 reversed the inhibitory effect of lncRNA FAL1 knockdown on the proliferative potential of OSCC cells. In addition, the overexpression of CRKL reversed the inhibitory effect of lncRNA FAL1 down-regulation on the proliferative potential of OSCC cells as well.
Conclusions: LncRNA FAL1 is highly expressed in OSCC. Moreover, it promotes the development of OSCC by regulating CRKL expression as a sponge of microRNA-761.