Histone methylatic modification mediates the tumor-suppressive activity of curcumol in hepatocellular carcinoma via an Hotair/EZH2 regulatory axis

Ethnopharmacological relevance: Curcuma kwangsiensis S. G. Lee & C. F. Liang (Guangxi ezhu, in Chinese) has been used as a traditional Chinese medicine (TCM) for approximately 2000 years. Curcumol is one of the major bioactive components of this herb, which has been demonstrated possesses anti-cancer properties, and was recorded in the Chinese Pharmacopoeia 2020 edition. However, most studies mainly focused on the superficial anti-cancer activity, the underlying mechanism remains poorly understood. Aim of the study: In the present study, we aimed to investigate the anti-tumor effect of Curcumol on hepatocellular carcinoma (HCC), and elucidate its underlying mechanism from the perspective of epigenetic modification. Materials and methods: The potential anti-cancer properties of Curcumol were evaluated in HepG2 and SMMC7721 cells. Its effects on cell growth, cell cycle, apoptosis and migration were examined in these HCC cells. Moreover, the lncRNA HOX transcript antisense intergenic RNA (Hotair) and histone methylatic modification were detected by qPCR and Western blotting assays. Results: In the present study, Curcumol was illustrated to suppress cell growth in HCC cells via inducing apoptosis and cell cycle arrest. And it was also found that Curcumol inhibited the invasion and metastasis of HCC as well. As for the mechanism investigation, it was showed that lncRNA Hotair was significantly downregulated by Curcumol in HCC cells. As is well known, Hotair recruited histone methyltransferase enhancer of zeste homolog 2 (EZH2) to exert transcriptional regulation. Our results showed that EZH2 were downregulated by Curcumol in HCC cells, and thus disrupted the trimethylation of H3K9 and H3K27 which were specifically catalyzed by EZH2. Conclusions: In conclude, our results demonstrated that Curcumol suppressed tumor growth and metastasis via an Hotair/EZH2/histone modification regulatory axis.