Background: Esophageal carcinoma is one of the most common malignancies with high cancer-related morbidity and mortality worldwide. MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate a wide variety of cellular processes, and also play an important role in the development and progression of cancers. In a previous microarray study, we demonstrated that miR-130b was upregulated in esophageal squamous cell carcinoma (ESCC) tissues. However, the biologic functions and the molecular mechanism of miR-130b in ESCC remain to be elucidated.
Methods: qRT-PCR assays were used to quantify miR-130b expression levels in ESCC samples. Novel targets of miR-130b were identified via a bioinformatics search and confirmed using a dual-luciferase reporter system. Western blotting and qRT-PCR assays were used to quantify the expression of the target gene PTEN (phosphatase and tensin homolog) and the downstream effector, Akt. ESCC cells over- or underexpressing miR-130b were analyzed for in vitro biologic functions.
Results: High levels of miR-130b were identified in 20 ESCC samples following comparison with adjacent non-neoplastic tissues. We confirmed that miR-130b interacted with the 3'-untranslated region of PTEN, and that an increase in the expression level of miR-130b negatively affected the protein level of PTEN. However, the dysregulation of miR-130b had no obvious impact on PTEN mRNA. As Akt is a downstream effector of PTEN, we explored if miR-130b affected Akt expression, and found that miR-130b indirectly regulated the level of phosphorylated Akt, while total Akt protein remained unchanged. Overexpression of miR-130b increased the proliferation of ESCC cells and enhanced their ability to migrate and invade. In contrast, the proliferation, migration, and invasion of ESCC cells were weakened when miR-130b expression was suppressed, which was reversed by PTEN-targeted siRNA.
Conclusion: The results indicate that miR-130b plays an oncogenic role in ESCC cells by repressing PTEN expression and Akt phosphorylation, which would be helpful in developing miRNA-based treatments for ESCC.