LncRNA H19 Activates the RAS-MAPK Signaling Pathway via miR-140-5p/SOS1 Axis in Malignant Liver Tumors.

Objective: To study the influences of LncRNA H19 (H19) on malignant liver tumor cells and elucidate the underlying molecular mechanisms.

Methods: H19 expression in liver tumor tissues, matched normal liver tissues, human liver malignant tumor cell lines and the human hepatocyte line LO2 was assessed via quantitative RT-PCR. Cell viability analysis and Matrigel invasion analysis were performed to evaluate the effects of H19 on cell proliferation and invasion. Luciferase reporter analysis was carried out to assess the interaction between miR-140-5p and SOS Ras/Rac guanine nucleotide exchange factor 1 (SOS1). The influence of H19 on the Ras-MAPK signalling pathway was evaluated by detecting key protein levels via active Ras pull-down analysis and Western blot analysis.

Results: H19 expression was lower in liver cancer samples than in matched normal liver tissue samples. H19 overexpression enhanced the proliferation and invasion of HepG2 and SMMC-7721 cells. H19 overexpression increased the level of activated Ras. The expression levels of phosphorylated Raf, phosphorylated ERK and phosphorylated MEK were increased by H19 overexpression. H19 knockdown had the opposite effect. Treatment with a MAPK inhibitor significantly reversed the influence of H19 overexpression on liver malignant tumor cell growth and invasion. The MAPK activator reversed the opposing effects of H19 silencing. H19 overexpression increased the protein level of SOS1, and miR-140-5p directly targeted SOS1.

Conclusion: H19 can activate the Ras-MAPK signalling pathway via the miR-140-5p/SOS1 axis in malignant liver tumour cells.