Crispr-Cas9-based lncRNA interference and activation identified aberrant expression of MYC- regulated ST8SIA6-AS1 promotes tumorigenesis and metastasis in hepatocellular carcinoma

Abstract

Abstract Background Long noncoding RNAs (lncRNAs) participate in the formation, progression, and metastasis of cancer. This study aimed to explore the roles of lncRNA ST8SIA6-AS1 in the initiation and progression of hepatocellular carcinoma (HCC) and elucidate the underlying regulatory mechanisms. Methods Fifty-six in-house pairs of HCC tissues were included in this study and the ST8SIA6-AS1 RNA level were determined by real‑time PCR. The knockdown and overexpression of ST8SIA6-AS1 in HCC cell lines were performed by Crispr-Cas9-based gene repression and activation. The effects of LncRNA ST8SIA6-AS1 on the biological behavior of HCC cells were determined in vitro and in vivo. Luciferase reporter assays, ChIP qPCR, and co-IP assays were performed to detect the binding sites and biological behavior of MYC and FOXA1 on chromatin. In this study, databases ENCODE and GEPIA were invoked to analyze the regulatory mechanisms of ST8SIA6-AS1 expression. Results Here, the results showed that the expression of ST8SIA6-AS1 is limited to the testes and prostate, but not liver tissue, in physiological states, significantly increased in HCC. This finding was validated in multiple HCC cell lines and 56 in-house pairs of HCC tissues. Functionally, high-efficiency Crispr-Cas9-based knockdown of ST8SIA6-AS1 revealed that ST8SIA6-AS1 knockdown attenuated the proliferation, and decreased the migration and infiltration of HCC cells. ST8SIA6-AS1 knockdown also significantly reduced the growth rate of subcutaneous and orthotopic HCC tumors. Conversely, Crispr-Cas9-based ST8SIA6-AS1 overexpression significantly improved the oncogenic characteristics of HCC cells. These results suggest that aberrant ST8SIA6-AS1 expression enhances the oncogenic characteristics in the liver. Further analysis showed that ST8SIA6-AS1 upregulation was regulated by the direct binding of transcription factor MYC to the − 260 bp to + 155 bp and + 1003 bp to + 1312 bp region of the ST8SIA6-AS1 transcription start site, a segment with high H3K27 acetylation. MYC knockdown or treatment with the BET bromodomain inhibitor JQ-1 significantly reduced ST8SIA6-AS1 RNA expression in HCC cells. Conclusion Aberrant ST8SIA6-AS1 expression in HCC is mediated by MYC and FOXA1, which plays an oncogenic role in HCC. And ST8SIA6-AS1 could serve as a molecular marker for HCC diagnosis.