Atractylenolide II sensitizes hepatocellular carcinoma to sorafenib and reduces sorafenib-induced hepatotoxicity: a preclinical pharmacological study

Hepatocellular carcinoma (HCC) is the most common primary liver tumor with a high mortality rate. Sorafenib is a first-line systemic therapy for advanced HCC, but drug resistance usually occurs within six months. Although combined therapies have shown improved efficacy of sorafenib in treating HCC, the clinical outcomes remain unsatisfactory due to high toxicity or unimproved drug resistance.
Through screening Chinese medicinal herb-derived compounds in several cell viability systems, we identified atractylenolide II (AT-II), a natural sesquiterpene, as a potential adjuvant candidate to sorafenib. Atractylenolides have safely alleviated cancer cachexia in gastric cancer patients in a clinical trial and have good oral bioavailability. We found that AT-II enhanced the pro-apoptotic effects of sorafenib in Hepa1-6 (mouse) and HepG2 (human) sorafenib-sensitive HCC cells, as well as in HepG2-SR sorafenibresistant HCC cells. Using an in situ HCC allograft (Hepa1-6) mouse model, we observed that the combination of AT-II and sorafenib (AT-II 25 mg/kg/d + sorafenib 30 mg/kg/d) synergistically inhibited tumor growth in mouse livers compared to individual AT-II (25 mg/kg/d) or sorafenib (30 mg/kg/d) treatments. Sorafenib alone significantly increased the serum ALT level, a marker of liver injury. In contrast, AT-II alone did not affect the ALT level, and the sorafenib-induced ALT level was counterbalanced in the combination (AT-II-plus-sorafenib)-treated mice. In a subcutaneous sorafenibresistant human HCC (HepG2-SR) xenograft-bearing mouse model, as expected, sorafenib had little impact on tumor growth. Importantly, the combination of sorafenib and AT-II displayed synergistic effects in suppressing tumor growth. Again, while the serum ALT level was elevated in sorafenib-treated mice, it remained unchanged in the combination treatment group compared to the vehicle control group. We therefore hypothesize that AT-II is a safe and effective adjuvant to sorafenib for treating HCC. To prove this hypothesis, we propose the following objectives:

1) To investigate the effects of AT-II in sensitizing HCC to sorafenib and its protective effects on sorafenib-induced hepatotoxicity.
2) To explore the mechanisms by which AT-II sensitizes HCC cells to sorafenib and protects sorafenib-impaired liver function.
We expect to demonstrate that AT-II effectively and safely prevents resistance to sorafenib and sensitizes cancer cells to sorafenib treatment in HCC models. We also expect to elucidate the underlying mechanisms of action of AT-II. If successful, this study will lay the groundwork for developing AT-II as an adjuvant to sorafenib for treating HCC.