Xihuang pills induce apoptosis in hepatocellular carcinoma by suppressing phosphoinositide 3-kinase/protein kinase-B/mechanistic target of rapamycin pathway

BACKGROUND The phosphoinositide 3-kinase/protein kinase-B/mechanistic target of rapamycin (PI3K/Akt/mTOR) signalling pathway is crucial for cell survival, differentiation, apoptosis and metabolism. Xihuang pills (XHP) are a traditional Chinese preparation with antitumour properties. They inhibit the growth of breast cancer, glioma, and other tumours by regulating the PI3K/Akt/mTOR signalling pathway. However, the effects and mechanisms of action of XHP in hepatocellular carcinoma (HCC) remain unclear. Regulation of the PI3K/Akt/mTOR signalling pathway effectively inhibits the progression of HCC. However, no study has focused on the XHP-associated PI3K/Akt/mTOR signalling pathway. Therefore, we hypothesized that XHP might play a role in inhibiting HCC through the PI3K/Akt/mTOR signalling pathway. AIM To confirm the effect of XHP on HCC and the possible mechanisms involved. METHODS The chemical constituents and active components of XHP were analysed using ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS). Cell-based experiments and in vivo xenograft tumour experiments were utilized to evaluate the effect of XHP on HCC tumorigenesis. First, SMMC-7721 cells were incubated with different concentrations of XHP (0, 0.3125, 0.625, 1.25, and 2.5 mg/mL) for 12 h, 24 h and 48 h. Cell viability was assessed using the CCK-8 assay, followed by an assessment of cell migration using a wound healing assay. Second, the effect of XHP on the apoptosis of SMMC-7721 cells was evaluated. SMMC-7721 cells were stained with fluorescein isothiocyanate and annexin V/propidium iodide. The number of apoptotic cells and cell cycle distribution were measured using flow cytometry. The cleaved protein and mRNA expression levels of caspase-3 and caspase-9 were detected using Western blotting and quantitative reverse-transcription polymerase chain reaction (RT-qPCR), respectively. Third, Western blotting and RT-qPCR were performed to confirm the effects of XHP on the protein and mRNA expression of components of the PI3K/Akt/mTOR signalling pathway. Finally, the effects of XHP on the tumorigenesis of subcutaneous hepatocellular tumours in nude mice were assessed. RESULTS The following 12 compounds were identified in XHP using high-resolution mass spectrometry: Valine, 4-gingerol, myrrhone, ricinoleic acid, glycocholic acid, curzerenone, 11-keto-beta-boswellic acid, oleic acid, germacrone, 3-acetyl-9,11-dehydro-beta-boswellic acid, 5 beta-androstane-3,17-dione, and 3-acetyl-11-keto-beta-boswellic acid. The cell viability assay results showed that treatment with 0.625 mg/mL XHP extract decreased HCC cell viability after 12 h, and the effects were dose- and time-dependent. The results of the cell scratch assay showed that the migration of HCC cells was significantly inhibited in a time-dependent manner by the administration of XHP extract (0.625 mg/mL). Moreover, XHP significantly inhibited cell migration and resulted in cell cycle arrest and apoptosis. Furthermore, XHP downregulated the PI3K/Akt/mTOR signalling pathway, which activated apoptosis executioner proteins (e.g., caspase-9 and caspase-3). The inhibitory effects of XHP on HCC cell growth were determined in vivo by analysing the tumour xenograft volumes and weights. CONCLUSION XHP inhibited HCC cell growth and migration by stimulating apoptosis via the downregulation of the PI3K/Akt/mTOR signalling pathway, followed by the activation of caspase-9 and caspase-3.