EM-2 inhibited autophagy and promoted G2/M phase arrest and apoptosis by activating the JNK pathway in hepatocellular carcinoma cells

• Published in: Acta pharmacologica Sinica 2021-07, Vol.42 (7), p.1139-1149
• Main Authors: Yang, Jie, Li, Zhen-dong, Hou, Chang-yan, Li, Zi-yu, Li, Qiang, Miao, Shen-yu, Zhang, Qing, Zhang, Xiao-ying, Zhu, Xiao-feng, Jiang, Jian-wei
• Format: Article
• Language: English
• Subjects: Antitumor activity; Apoptosis; Autophagy; Biomedical and Life Sciences; Biomedicine; Cell proliferation; Cell viability; Cytotoxicity; Endoplasmic reticulum; Epithelial cells; Hepatocellular carcinoma; Hepatocytes; Immunology; Internal Medicine; Liver cancer; MAP kinase; Medical Microbiology; Phagocytosis; Pharmacology/Toxicology; Vaccine; Western blotting
• ISSN: 1671-4083; 1745-7254
• DOI: 10.1038/s41401-020-00564-6

This study aimed to investigate the inhibitory effect of EM-2, a natural active monomer purified from Elephantopusmollis H.B.K., on the proliferation of human hepatocellular carcinoma cells and the molecular mechanism involved. The results from the MTT assay revealed that EM-2 significantly inhibited the proliferation of human hepatocellular carcinoma (HCC) cells in a dose-dependent manner but exhibited less cytotoxicity to the normal liver epithelial cell line LO2. EdU staining and colony formation assays further confirmed the inhibitory effect of EM-2 on the proliferation of Huh-7 hepatocellular carcinoma cells. According to the RNA sequencing and KEGG enrichment analysis results, EM-2 markedly activated the MAPK pathway in Huh-7 cells, and the results of Western blotting further indicated that EM-2 could activate the ERK and JNK pathways. Meanwhile, EM-2 induced apoptosis in a dose-dependent manner and G 2 /M phase arrest in Huh-7 cells, which could be partially reversed when treated with SP600125, a JNK inhibitor. Further study indicated that EM-2 induced endoplasmic reticulum stress and blocked autophagic flux in Huh-7 cells by inhibiting autophagy-induced lysosome maturation. Inhibition of autophagy by bafilomycin A1 could reduce cell viability and increase the sensitivity of Huh-7 cells to EM-2. In conclusion, our findings revealed that EM-2 not only promoted G 2 /M phase arrest and activated ER stress but also induced apoptosis by activating the JNK pathway and blocked autophagic flux by inhibiting autolysosome maturation in Huh-7 hepatocellular carcinoma cells. Therefore, EM-2 is a potential therapeutic drug with promising antitumor effects against hepatocellular carcinoma and fewer side effects.