Huaier Restrains Proliferative and Migratory Potential of Hepatocellular Carcinoma Cells Partially Through Decreased Yes-Associated Protein 1

In China, Trametes robiniophila Murr (Huaier), a traditional Chinese herbal medicine, has been widely used in adjuvant therapies of hepatocellular carcinoma (HCC). However, the molecular mechanisms have not been fully understood. The aims of this study are to investigate the functions and mechanisms of Huaier on inhibiting proliferation and migration of HCC cells. Firstly, cell counting kit-8 (CCK-8) and colony formation shown Huaier inhibited proliferation of HCC Bel-7404, Bel-7402 and SMMC-7721 cells in a dose-dependent manner, and this inhibition might be due to Huaier decreased the expressions of the proliferating cell nuclear antigen (PCNA), the nuclear proliferation related antigen (Ki-67) and CyclinD1 detected by western blotting analysis. Notably, we also found Huaier treatment did not cause any cytotoxicity to normal human hepatocyte L-02 cells. Next, we found Huaier dose-dependently decreased Bcl-2 expression and increased Bax expression in Bel-7404 cells. The activities of cleaved caspase substrates had also been enhanced after Huaier treatment, suggesting Huaier treatment could induce HCC cell apoptosis. Then, the inhibitory effects of Huaier on migration of Bel-7404, Bel-7402 and SMMC-7721 cells via inhibiting Epithelial mesenchymal transition (EMT) had also been proved. Moreover, we confirmed yes-associated protein 1 (YAP1) was up-regulated in HCC cells and tissues, and overexpression of YAP1 promoted HCC cell proliferation and migration. Then, western blot and immunefluorescence shown Huaier had the inhibitory effects on YAP1 in HCC cells. On the other hand, human liver cancer tissue microarray (TMA) shown YAP1 expression was closely to clinic. Our study also confirmed Huaier had the inhibitory effects on YAP1 in xenograft mice models, it could be because Huaier treatment translocated YAP1 from nucleus to cytoplasm, and further promoted phosphorylation of YAP1 to be degraded by ubiquitination. Hence, we conclude that Huaier may restrain the proliferation and migration of HCC cells via down-regulation of YAP1. In summary, our study reveals the potential mechanisms of Huaier on inhibiting proliferation and migration of HCC cells. Importantly, for the first time, we found that Huaier can inhibit YAP1 expression in this anti-tumor process. We believe this finding is beneficial for the clinical applications of Huaier and the targeted therapies for HCC.