273 - The Flavonoid Isoliquiritigenin Is Toxic to Neuroblastoma Cells and Promotes Necroptosis

Abstract

Neuroblastoma is the most common childhood cancer diagnosed in the first year of life that shows high mortality. The flavonoid, isoliquiritigenin (4,2’,4’-trihydroxychalcone; ISL), exhibits significant anti-tumor activities, including inhibition of proliferation and cell cycle progression. In the present work we evaluated the capacity of ISL to inhibit cellular proliferation and migration, and examined the anti-tumor activity of ISL in the human neuroblastoma cell line SH-SY5Y. Neuroblastoma cells were exposed to 10-200 µM ISL or vehicle (control) for 24h. Incubation with ISL decreased the number of viable cells, cell confluence and intracellular ATP concentration. There were no significant differences in caspase 3/7 activation between control and ISL groups and ISL did not appear to induce release of extracellular TNF and IL-1β from SH-SY5Y cells indicating that ISL did not induce cell death via apoptosis. An inhibitor of necroptosis, necrostatin-1, induced significant increases in ATP concentration in ISL treated neuroblastoma cells indicating involvement of this programmed cell death pathway. ISL treatment inhibited migration and proliferation of SH-SY5Y cells and also affected the cell cycle by decreasing the proportion cells in G0/G1 phase and increasing cells in S and G2/M phases. These findings suggest that ISL can influence proliferation by arresting SH-SY5Y cell growth cycle. Using ELISA the ratio of phosphorylated/total p38 and ERK 1/2 in cells treated with ISL was higher than in the control cells. Western blot assay confirmed increased expression of pERK1/2 after ISL treatment. The ratio of phosphorylated/total Akt in neuroblastoma cells incubated with ISL also increased significantly. Together the results suggest that ISL can induce cell cycle arrest and neuroblastoma cell death by necroptosis.