Conclusion
GNA14 could be regulated by HBx by modulating the methylation status of its promoter. We identified GNA14 as a potential biomarker and therapeutic target for HCC.
Methods
Combined analysis of TCGA and GEO databases was performed to obtain potential methylation-related tumor suppressors in HCC. Methyl-target sequencing was performed to analyze the methylation level of the GNA14 promoter. The diagnostic value of GNA14 as a predictor of HCC was evaluated in HCC tumor samples and compared with normal tissues. The functional role of GNA14 and its upstream and downstream regulatory factors were investigated by gain-of-function and loss-of-function assays in vitro. Subcutaneous tumorigenesis, lung colonization, and orthotopic liver tumor model were performed to analyze the role of GNA14 in vivo.
Results
The expression of GNA14 was found to be downregulated in HCC and it was negatively correlated with hepatitis B virus (HBV) infection, vascular invasion, and prognosis of HCC. DNA methylation was demonstrated to be responsible for the altered expression of GNA14 and was regulated by HBV-encoded X protein (HBx). GNA14 regulated the RB pathway by promoting Notch1 cleavage to inhibit tumor proliferation, and might inhibit tumor metastasis by inhibiting the expression of JMJD6.