SC-III3, a novel scopoletin derivative, induces cytotoxicity in hepatocellular cancer cells through oxidative DNA damage and ataxia telangiectasia-mutated nuclear protein kinase activation.
Parole chiave
Astratto
BACKGROUND
Natural products from plants have been proven to be important resources of antitumor agents. In this study, we exploited the antitumor activity of (E)-3-(4-chlorophenyl)-N-(7-hydroxy-6-methoxy-2-oxo-2H-chromen-3-yl) acrylamide (SC-III3), a newly synthesized derivative of scopoletin, by in vitro and in vivo experiments.
METHODS
Human hepatocellular carcinoma cell line HepG2 cells and xenograft of HepG2 cells in BALB/c nude mice were used to investigate the effects of SC-III3 on hepatocellular cancers. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Cell cycle arrest, apoptosis and ATM-Chk pathway-related proteins were characterized by western blot.
RESULTS
SC-III3 selectively inhibited the viability of HepG2 cells without significant cytotoxicity against human normal liver cells LO2. In mouse xenograft model of HepG2 cells, SC-III3 showed a marked inhibition of tumor growth in a dose-dependent manner. Cell cycle analysis revealed that SC-III3 induced cells to accumulate in S phase, which was accompanied by a marked decrease of the expressions of cyclin A, cyclin B, cyclin E and Cdk2 proteins, the crucial regulators of S phase cell cycle. SC-III3 treatment resulted in DNA breaks in HepG2 cells, which might contribute to its S phase arrest. The S arrest and the activation of ATM-Chk1/Chk2-Cdc25A-Cdk2 pathways induced by SC-III3 in HepG2 cells could be efficiently abrogated by pretreatments of either Ku55933 (an inhibitor of ATM) or UCN-01 (an inhibitor of Chk1/Chk2). The activation of p53-p21 pathway by SC-III3 was also reversed by Ku55933 treatment. SC-III3 led to significant accumulation of intracellular reactive oxygen species (ROS), a breaker of DNA strand, in HepG2 cells but not LO2 cells. Pretreatment with N-acetyl-l-cysteine (NAC), a ROS scavenger, could reverse SC-III3-caused ROS accumulation, DNA damage, activation of signal pathways relevant to DNA damage, S phase arrest and cell viability decrease in HepG2 cells.
CONCLUSIONS
SC-III3 is able to efficiently inhibit the growth of hepatocellular carcinoma through inducing the generation of intracellular ROS, DNA damage and consequent S phase arrest, but lack of significant cytotoxicity against normal liver cells. This compound deserves further studies as a candidate of anticancer drugs.