Background and purpose: An increasing number of studies have revealed that microRNAs (miRNAs) are the main drivers of hepatocarcinogenesis including progression to later stages of liver cancer. Recently, miR-548b was identified as a cancer-related miRNA in glioma and tongue squamous cell carcinoma. Nonetheless, the expression pattern and specific roles of miR-548b in hepatocellular carcinoma (HCC) have not yet been clarified.
Methods: Expression levels of miR-548b in HCC tissues and cell lines were measured by reverse-transcription quantitative PCR. In vitro and in vivo functional assays were performed to determine the effects of miR-548b on the malignant phenotypes of HCC cells. In addition, the molecular mechanisms by which miR-548b regulates the initiation and progression of HCC were investigated in detail.
Results: miR-548b expression was weak in HCC tissues and cell lines. The low miR-548b expression significantly correlated with tumor size, TNM stage, and venous infiltration of HCC. In addition, exogenous miR-548b expression suppressed HCC cell proliferation, colony formation, and metastasis and induced apoptosis in vitro. Silencing of miR-548b exerted an opposite effect on these characteristics of HCC cells. Furthermore, miR-548b overexpression hindered tumor growth in vivo. Mechanistic analysis identified high-mobility group box 1 (HMGB1) as a direct target gene of miR-548b in HCC cells. Moreover, an HMGB1 knockdown reproduced the effects of miR-548b upregulation on HCC cells. Recovered HMGB1 expression reversed the effects of miR-548b on HCC cells. Notably, miR-548b overexpression deactivated the PI3K–AKT pathway in HCC cells in vitro and in vivo.
Conclusion: Our findings provide the first evidence that miR-548b restrains HCC progression, at least partially, by downregulating HMGB1 and deactivating the PI3K–AKT pathway. Thus, miR-548b might be a novel target for the development of new therapies for HCC.
Keywords: microRNA-548b, hepatocellular carcinoma, PI3K–AKT pathway, high-mobility group box 1, HMGB1