Cepharanthine-mediated endoplasmic reticulum stress inhibits Notch1 via binding GRP78 for suppressing hepatocellular carcinoma metastasis

Background

The metastasis of hepatocellular carcinoma (HCC) leads to a poor prognosis, wherein the activation of Notch1 is an essential contributor. Cepharanthine (Cep) has been identified for its effective antiviral function and versatile intracellular targets. Our previous study has only reported the anti-cancer efficacy of Cep in lung cancer, without an in-depth exploration. Herein, the present study aims to investigate the anti-metastasis effect in HCC, the target involved, and the molecular mechanism of Cep.

Methods

Stable over-expression of Notch1-N1ICD yielded C5WN1 cells compared with C5WBF344 cells. The C5WN1 cells and C5WN1 cell-bearing mice were applied as the HCC model. The bioinformatics analysis, RNA sequencing, molecular docking, cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS), microscale thermophoresis (MST), and transient knockdown techniques were carried out to identify the underlying target. The apoptosis assay, immunofluorescent staining, qRT-PCR, Western blots, Elisa, flow cytometry, migration and scratching experiments, Transmission electron microscopy (TEM), laser scanning confocal microscopy (LSCM), micro-computed tomography (micro-CT), and histopathological experiments were conducted to assay the anti-HCC efficacy, functions, and mechanism.

Results

Notch1 had an increased expression in HCC and contributed to metastasis thereupon. Surprisingly, Cep (2 μg/ml in vitro, 5 mg kg^-1 in vivo) presented potent Notch1 signaling pathway inhibitory effect and anti-metastasis efficacy in C5WN1 cells and in situ mice models as evidenced by reduced Notch1/MMP-2/MMP-9 expression, TGF-β release, decreased cell migration, diminished pulmonary metastases, and prolonged survival. RNA sequencing showed that the differential gene of Cep-treated HCC cells was positioned in the endoplasmic reticulum (ER). Molecular docking, CETSA, DARTS, and MST further identified that the possible target of Cep was GRP78, which was distributed in the ER. As expected, Cep (2 μg/ml) up-regulated the critical molecules of ER stress such as GRP78, induced β-amyloid accumulation, and promoted calcium burst in HCC. In contrast, suppression of GRP78 attenuated Cep-induced ER stress. Furthermore, inhibition of ER stress abated Cep-induced Notch1 inactivation and HCC cells’ migration.

Conclusions

Taken together, the present study finds that Cep possesses excellent anti-metastasis of HCC, wherein the GRP78 could be directly bound and activated by Cep, leading to ER stress and Notch1 blockage. This study reveals for the first time the effect, critical target, and mechanism of the Cep-mediated anti-cancer effect, providing novel insights into the molecular target therapy by phytomedicine.