LncRNA FAL1 promotes the development of oral squamous cell carcinoma through regulating the microRNA-761/CRKL pathway.

Abstract

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. 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. 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. LncRNA FAL1 is highly expressed in OSCC. Moreover, it promotes the development of OSCC by regulating CRKL expression as a sponge of microRNA-761.