LYG-202 Augments Tumor Necrosis Factor-α-Induced Apoptosis via Attenuating Casein Kinase 2-Dependent Nuclear Factor-κB Pathway in HepG2 Cells

Tumor necrosis factor-alpha (TNF-alpha) is being used as an antineoplastic agent in treatment regimens of patients with locally advanced solid tumors, but TNF-alpha alone is only marginally active. In clinical use, it is usually combined with other chemical agents to increase its tumor response rate. Our previous studies reported that LYG-202 (5-hydroxy-8-methoxy-7-(4-(4-methylpiperazin-1-yl)butoxy)-2-phenyl-4H-chromen-4-one), a synthesized flavonoid with a piperazine substitution, has antiproliferative, antiangiogenic, and proapoptotic activities in multiple cancer cell lines. Here we evaluated the antineoplastic effect of TNF-alpha and analyzed the mechanism underlying its combination with LYG-202. Our results indicated that LYG-202 significantly increased the cytostatic and proapoptotic activity of TNF-alpha in HepG2 cells and heightened the protein level of apoptosis-related genes including caspase-3, caspase-8/9, cleaved poly(ADP-ribose) polymerase, and Bid. The fact that LYG-202 had a fitness score similar to that of the casein kinase 2 (CK2) inhibitor naphthyridine-8-carboxylate (CX-4945) implied to us that it may serve as a potential candidate for CK2 inhibitor, and the kinase activity assay suggested that LYG-202 significantly inhibited CK2 activity. Moreover, the electrophoretic mobility shift assay and luciferase assay showed that LYG-202 blocked the TNF-alpha-induced nuclear factor-kappa B (NF-kappa B) survival signaling pathway primarily by inactivating protein kinase CK2. In murine xenograft models, we also found that LYG-202 enhanced TNF-alpha antineoplastic activity and inhibited CK2 activity and NF-kappa B-regulated antiapoptotic gene expression. All these results showed that LYG-202 enhanced TNF-alpha-induced apoptosis by attenuating the CK2-dependent NF-kappa B pathway and probably is a promising agent in combination with TNF-alpha.