Background N6-methyladenosine (m6A) methylation, a well-known modification with new epigenetic functions, has been reported to participate in the tumorigenesis of hepatocellular carcinoma (HCC), providing novel insights into the molecular pathogenesis of this disease. However, as the key component of m6A methylation, Wilms tumor 1-associated protein (WTAP) has not been well studied in HCC. Here we investigated the biological role and underlying mechanism of WTAP in liver cancer. Methods We determined the expression of WTAP and its correlation with clinicopathological features using tissue microarrays and the Cancer Genome Atlas (TCGA) dataset. And we clarified the effects of WTAP on HCC cells using cell proliferation assay, colony formation, Edu assay and subcutaneous xenograft experiments. We then applied RNA sequencing combined with gene expression omnibus (GEO) data to screen candidate targets of WTAP. Finally, we investigated the regulatory mechanism of WTAP in HCC by m6A dot blot assay, methylated RNA immunoprecipitation (MeRIP) assay, dual luciferase reporter assay, RNA immunoprecipitation (RIP) assay and Chromatin immunoprecipitation (ChIP) assay. Results We demonstrated that WTAP was highly expressed in HCC which indicated the poor prognosis, and that WTAP expression served as an independent predictor of HCC survival. Functionally, WTAP promoted the proliferation capability and tumor growth of HCC cells in vitro and in vivo. Furthermore, ETS proto-oncogene 1 (ETS1) was identified as the downstream effector of WTAP. The m6A modification regulated by WTAP led to post-transcriptional suppression of ETS1, with the implication of Hu-Antigen R (HuR) as an RNA stabilizer. Then ETS1 was found to inhibit the progression of HCC and could rescue the phenotype induced by WTAP deficiency. Moreover, WTAP modulated the G2/M phase of HCC cells through a p21/p27-dependent pattern mediated by ETS1. Conclusion We have identified that WTAP is significantly up-regulated in HCC and promotes liver cancer development. WTAP-guided m6A modification contributes to the progression of HCC via the HuR-ETS1-p21/p27 axis. Our study is the first to report that WTAP-mediated m6A methylation has a crucial role in HCC oncogenesis, and highlights WTAP as a potential therapeutic target of HCC treatment. Electronic supplementary material The online version of this article (10.1186/s12943-019-1053-8) contains supplementary material, which is available to authorized users.
Hepatocellular carcinoma (HCC) is a highly heterogeneous, multigene-driven malignant tumor. Long chain acyl-CoA synthetase 4 (ACSL4), an enzyme has pivotal roles in arachidonic acid (AA) metabolism. However, its function and the underlying molecular mechanisms in HCC are still not fully elucidated. Here, we identified ACSL4 as a novel marker for AFP high subtype HCC through transcriptome profiling. ACSL4 was frequently upregulated in HCC samples and associated with poor prognosis. Functionally, ACSL4 knockdown resulted in decreased cell growth, whereas ectopic ACSL4 expression facilitated tumor formation in vitro and in vivo. Mechanistically, ACSL4 stabilized the oncoprotein c-Myc through ubiquitin-proteasome system in an ERK/FBW7-dependent manner. Cell growth ability mediated by ACSL4 elevation was partly attenuated by c-Myc depletion using siRNA or its inhibitor 10058-F4. In contrast, the effects of ACSL4 silencing were partially reversed by c-Myc overexpression via FBW7 knockdown. Clinically, ACSL4 expression was positively correlated with c-Myc in HCC. In conclusion, ACSL4 is a novel marker for AFP high subtype HCC. Our data uncovered a new mechanism by which ACSL4 promotes HCC progression via c-Myc stability mediated by ERK/ FBW7/c-Myc axis and could be a valuable prognostic biomarker and a potential therapeutic target in HCC.
BackgroundHypoxia is a common feature of solid tumors, including HCC. And hypoxia has been reported to play an important role in HCC progression. However, the potential mechanism of miRNAs in hypoxia mediating HCC progression still remains unclear.MethodsThe HCC cells were cultured in the atmosphere of 1 % oxygen to induce hypoxia. The microRNA microarray was employed to search for the hypoxia-inducible miRNAs. RT-PCR, western blot and immunohistochemistry were used to detect the RNA and protein levels. HUVEC were applied to explore the angiogenesis level.ResultsWe found that miR-182 was upregulated in the hypoxia-based microarray. We then revealed that miR-182 was also significantly increased in the HCC tissues compared to the corresponding normal tissues. In vitro capilliary tube formation assays showed that the miR-182 promoted angiogenesis. RASA1 was demonstrated as the direct target of miR-182. In addition, the suppression of RASA1 phenocopied the pro-angiogenesis effects of miR-182. Besides, RASA1 was also decreased in the hypoxia HCC cells while the inhibition of miR-182 partially restored the level of RASA1.ConclusionsOur data showed that hypoxia regulated the expression of miR-182 and RASA1 to promote HCC angiogenesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-015-0182-1) contains supplementary material, which is available to authorized users.
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