Objective: Daphnegiravone D (DGD), a prenylated flavonoid from Daphne giraldii Nitsche, a plant whose roots and stem are used in Chinese medicine, exerts an inhibitory effect on liver cancer cells. The protein kinase ataxia telangiectasia-mutated and Rad3-related (ATR) is an important component of the DNA damage response, and its inhibition enhances the sensitivity of some cancer cells to DNA-damaging drugs. Oxaliplatin (OXA) is a third-generation, platinum-based anticancer drug that exerts its inhibitory effects on liver cancer cells by inhibiting DNA synthesis. Owing to the fact that most patients develop drug resistance, finding novel treatments for liver cancer is urgent. In a previous study, DGD was shown to exert anti-tumor effects as a potential ATR kinase inhibitor. This study investigated the mechanism of action of DGD and its combination with OXA in liver cancer. Methods: HepG2 and Hep3B cells were used to evaluate the inhibitory effects of DGD on liver cancer. Cellular thermal shift assay, co-immunoprecipitation, and western blotting (WB) were used to confirm the impact of DGD on DNA damage. The methyl thiazolyl tetrazolium colorimetric method and the results were used to calculate the drug synergy score. Acridine orange/ethidium bromide staining, Annexin V/Propidium iodide staining, reactive oxygen species-related staining, and WB were performed to assess the efficacy of the combination of DGD and OXA. In vivo tumor xenograft model in nude mice was used to investigate the efficacy of this combination. Hematoxylin-eosin staining and immunohistochemistry were performed to observe the condition of tissues in vivo . Results: DGD inhibited liver cancer cells by affecting the formation of the ATR-ATRIP complex and downregulating the activator protein TopBP1. We found that the combination of DGD and OXA synergistically inhibited the growth of liver cancer cells and reduced the toxicity of OXA to normal hepatocytes. This synergistic effect was mediated by the induction of apoptosis, mitochondrial dysfunction, and oxidative stress. Further experiments suggested that DGD may suppress the DNA damage response by inhibiting the ATR pathway, which, in turn, enhances the effect of OXA on DNA damage. Consistent with the above results, DGD enhanced the anticancer effect and moderated the side effects of OXA in vivo . Conclusion: Our results showed that DGD greatly enhanced the anti-tumor effect of the chemotherapeutic drug OXA via the ATR pathway in liver cancer, both in vitro and in vivo . Graphical Abstract: http://links.lww.com/AHM/A231
Wang et al. (Tue,) studied this question.