M6A mRNA Methylation Regulates LKB1 to Promote Autophagy of Hepatoblastoma Cells through Upregulated Phosphorylation of AMPK.

Guohui Li,Zhongqi Cui,Nan Huang,Fenyong Sun,Ji Ma,Liang Deng,Qi Wu,Qiuhui Pan

doi:10.3390/genes12111747

Abstract

The N6-methyladenosine (m6A) RNA modification can regulate autophagy to modulate the growth and development of tumors, but the mechanism of m6A modification for the regulation of autophagy in hepatocellular carcinoma cells (HCC) remains unclear. In the study, the knockdown of the Wilms’ tumor 1-associating protein (WTAP) was made in HCC to study the correlation between m6A modification and autophagy. A fluorescent confocal microscopy analysis showed that the knockdown of WTAP could facilitate the autophagy of HCC. A Western blot analysis showed that the level of p-AMPK was decreased in WTAP-knockdown HCC cells. Additionally, LKB1, the upstream kinase of AMPK, was regulated by WTAP and it could mediate the phosphorylation of AMPK in an m6A-dependent manner. Further studies revealed that the knockdown of WTAP could reduce the level of LKB1 mRNA with m6A. This could result in the increased stability of LKB1 mRNA to promote its expression. The knockdown of WTAP could upregulate the level of autophagy and inhibit HCC proliferation. However, the overexpression of WTAP could resist autophagic cell death.

Highlights

Liver cancer is a frequently occurring malignancy, and it ranks among the highest in the world in terms of cancer-related death
The results indicated that the expression level of Wilms’ tumor 1-associating protein (WTAP) was higher in the hepatocellular carcinoma cells (HCC) cell lines than that in the normal hepatic cell line (Figure 1A)
The results showed that the expression levels of some autophagy-related proteins, including Beclin1, ULK, p-ULK, mTOR, and p-mTOR did not vary significantly in the stable strains of shWTAP BEL-7404 and shWTAP SMMC-7721 cell lines

Summary

Introduction

Liver cancer is a frequently occurring malignancy, and it ranks among the highest in the world in terms of cancer-related death. The incidence of liver cancer in China is ranked first in the world, and the situation of liver cancer prevention and treatment is still very serious [1,2]. It is very important to develop a more effective treatment for patients of liver cancer. Autophagy is an evolutionarily conserved intracellular degradation and metabolism process and it plays important roles in maintaining cell metabolism, genome integrity, and the self-renewal of organelles [3,4]. Autophagy is a doubleedged sword in tumor cells. The inhibition of autophagy can increase the sensitivity of cancer cells to anti-cancer therapy, but excessive autophagy can cause autophagic cell death

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Conclusion