The natural medicinal fungus Huaier promotes the anti-hepatoma efficacy of sorafenib through the mammalian target of rapamycin-mediated autophagic cell death.

ABSTRACT

Sorafenib (SOR) is currently the first line molecular targeting agent for advanced liver cancer therapy. Unfortunately, the insensitivity of liver cancer patients to SOR relatively limits its effectiveness. Huaier (HUA), a natural medicinal parasitic fungus found on the Sophora japonica Linn., has been widely employed as an adjuvant medication for numerous malignancies due to its potent anti-tumoral properties. This study aims to elucidate the enhancing therapeutic efficacy of HUA on SOR treatment in hepatocellular carcinoma (HCC) cells and mouse models. The CCK-8, clone formation, flow cytometry, immunofluorescence, transmission electron microscopy, western blot, bioinformatic analysis, and xenograft tumor assays were performed to evaluate the synergistic anti-hepatoma efficacy and mechanisms of HUA-SOR combination treatment on HCC cells. The results revealed combination treatment further inhibited proliferation, promoted apoptosis, enhanced autophagy of HCC cells, and suppressed the growth of transplanted tumors in mice, compared with either HUA or SOR treatment alone. For Hep3B and Huh7 cells, the optimal synergistic doses of HUA in combination with SOR were 8 mg/mL + 4 µM and 4 mg/mL + 2 µM, with combination index values of 0.646 and 0.588, respectively. Additionally, the underlying mechanisms might be related to biological processes that are mediated by mammalian target of rapamycin (mTOR). The combination treatment downregulated the protein expression levels of p-mTOR, p-p70S6K, p62, and upregulated the protein expression levels of Beclin-1 and LC3B-II. The mTOR activator MHY1485 attenuated the effect of HUA-SOR combination by inhibiting autophagy, suggesting HUA may potentiate the sensitivity of HCC cells to SOR by partially inducing mTOR-mediated autophagic cell death. These findings might provide a rationale experimental foundation for clinical applications of HUA with SOR.