Ent-8(14),15-Pimaradiene-2β,19-diol, a Diterpene from Aleuritopteris Albofusca, Inhibits Growth and Induces Protective Autophagy in Hepatocellular Carcinoma Cells

A new pimarane-type diterpene, ent-8(14),15-pimaradiene-2β,19-diol (JXE-23), was isolated from the fern plant Aleuritopteris albofusca by our previous work; however, the biological activity of this diterpene remains unclear. In the present study, the anti-cancer potential of JXE-23 in various cancer cells was investigated. Among MCF-7 breast cancer cells, A549 lung cancer cells, and HepG2 liver cancer cells, JXE-23 displayed significant cytotoxicity to HepG2 cells with an IC value of 17.20 ± 1.73 µM, while showing no obvious toxicity in normal hepatocytes HL7702. JXE-23 inhibited cell growth and colony formation in HepG2 cells. A cell cycle distribution analysis showed that JXE-23 caused G2/M cell cycle arrest. Besides, JXE-23 also suppressed the migration of HepG2 cells. Interestingly, an increase of light chain 3 II (LC3II) and Beclin 1 and a decrease of P62 have occurred in JXE-23-treated cells, as well as the formation of GFP-LC3 dots, indicative of autophagy induction by JXE-23. When combined with autophagy inhibitor 3-methyladenine and chloroquine, the cell viability was significantly reduced, suggesting that JXE-23 triggered protective autophagy in hepatoma cells. Further study showed that JXE-23 inactivated the CIP2A/p-AKT/c-Myc signaling axis in HepG2 cells. Our data provided evidence that JXE-23 inhibited cell growth, arrested cells at the G2/M phase, and induced protective autophagy in HepG2 hepatocellular carcinoma cells. JXE-23 may be a potential lead compound for anti-cancer drug development, and autophagy inhibitor treatment may provide an effective strategy for improving its anti-cancer effect.