Background: Gallbladder cancer (GBC) is the most common cancer of the biliary tract, but molecularly targeted therapies are not available for GBC. Loss of microRNA (miR)-335 expression may be a useful predictor of clinical outcomes and the reversal of its loss of expression may be a useful treatment strategy for GBC. In this study, we investigated whether a long noncoding RNA, nuclear paraspeckle assembly transcript 1 (NEAT1 ) sponges miR-335  in GBC cells.
Materials and Methods: Quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemistry were used to determine the expression of miR-335; NEAT1; survivin; and Ki67  in GBC cell lines (GBC-SD and SGC-996) and tissue samples from patients (n = 25). Cell Counting Kit-8, colony-formation, and Transwell migration and invasion assays were performed to measure cell proliferation, migration, and invasion. Bioinformatic analysis and dual-luciferase reporter assays were utilized to analyze correlativity.
Results: miR-335  overexpression resulted in inhibition of GBC cell proliferation and invasion. In addition, knockdown of NEAT1  resulted in downregulation of survivin expression. As NEAT1  competitively “sponges” miR-335, NEAT1  knockdown resulted in inhibited GBC cell proliferation and invasion in vitro and GBC tumor growth in vivo. Furthermore, NEAT1  was found to be upregulated in GBC samples, and its expression was inversely correlated with miR-335  levels, but positively correlated with survivin levels.
Conclusion: These findings indicate that NEAT1  promotes survivin expression by functioning as a competitive endogenous RNA for miR-335  in GBC cells; thus, we have identified a potential biomarker and target for GBC diagnosis and therapy.
Keywords: long noncoding RNA, NEAT1 , miR-335-5p , competitive endogenous RNA, survivin, gallbladder cancer