The dietary flavonoid isoliquiritigenin is a potent cytotoxin for human neuroblastoma cells

Abstract

Neuroblastoma (NB) is the most common extracranial solid tumor of early childhood; it accounts for approximately 8-10% of all childhood cancers and is the most common cancer in children in the first year of life. Patients in the high-risk group have a poor prognosis, with relapses being common and often refractory to drug treatment in those that survive. Moreover, the drug treatment itself can lead to a range of long-term sequelae. Therefore, there is a critical need to identify new therapeutics for NB. Isoliquiritigenin (ISLQ) is a naturally-occurring, dietary chalcone-type flavonoid with a range of biological effects that depend on the cell type and context. ISLQ has potential as an anticancer agent. Here we show that ISLQ has potent cytotoxic effects on SK-N-BE(2) and IMR-32 human NB cells, which carry amplification of the MYCN gene, the main prognostic marker of poor survival in NB. ISLQ was found to increase cellular reactive oxygen species (ROS). The cytotoxic effect of ISLQ was blocked by small molecule inhibitors of oxidative stress-induced cell death, and by the antioxidant N-acetyl-L-cysteine (NAC). Combined treatment of either SK-N-B-E(2) or IMR-32 cells with ISLQ and the anticancer agent cisplatin resulted in loss of cell viability that was greater than that induced by cisplatin alone. This study provides proof-of-principle that ISLQ is a potent cytotoxin for MYCN-amplified human NB cells. This is an important first step in rationalizing the further study of ISLQ as a potential adjunct therapy for high-risk NB.

4-Hydroxychalcone Induces Cell Death via Oxidative Stress in MYCN-Amplified Human Neuroblastoma Cells

“…All of these findings confirm that 4HC treatment leads to ROS-induced cell death in MYCN -amplified NB cells. This is consistent with our previous study showing that another chalcone, ISLQ, induced cell death in MYCN -amplified NB cells through the elevation of ROS levels, which was fully prevented by pretreatment with NAC [40]. This is an important finding, as the ability of ROS to chemosensitize cancer cells depends on the basal ROS levels in these cells.…”

“…In the current study, we found that 4HC exerted potent cytotoxic effects on MYCN -amplified SK-N-BE (2) and IMR-32 human NB cells at low concentrations, in comparison to other non- MYCN -amplified NB cells, kidney embryonic cells, or healthy murine primary neuronal cultures. We also found that the cytotoxicity induced in MYCN- amplified NB cell lines by 4HC was higher than that induced by ISLQ, another chalcone which we had investigated in a previous study [40]. The cytotoxic effect of 4HC treatment was found to be both time- and concentration-dependent and to be accompanied by decreases in both somal and nuclear area.…”

“…To further confirm this, we examined the effects of 4HC on primary cultures of E14 rat midbrain and found that 4HC treatment for 3 DIV was not toxic to these cells at concentrations of less than 25 μ M (Figures 1(i) and 1(j)). Comparison of the effects of 4HC treatment on cell viability in SK-N-BE (2) and IMR-32 cells with our previous study on the chalcone ISLQ in these cell lines [40] showed that 10 μ M 4HC treatment for 24 h induced a significantly greater reduction in cell viability than the same dose of ISLQ, in both of these cell types (Supplementary Figures ). This suggests that MYCN-amplified NB cells have differential sensitivity to distinct chalcones.…”

“…These cytotoxic effects of 4HC on NB cells are also consistent with our previous work on the chalcone-derived flavonoid, ISLQ. In that study, we found that treatment with ≥5 μ M ISLQ for 24 h had potent cytotoxic effects on both SK-N-BE (2) and IMR-32 cells [40]. 4HC had a greater cytotoxic effect on MYCN -amplified NB cells than the related chalcone, ISLQ.…”

“…A study that compared the cytotoxic effects of thirteen hydroxychalcones on melanoma cells confirmed that the number of hydroxyl groups in the molecule affects the strength of their cytotoxic activity [39]. Our previous work found that the chalcone isoliquiritigenin (ISLQ) had cytotoxic effects on NB cells, which were induced through elevation of reactive oxygen species (ROS), leading to activation of necroptotic cell death [40].…”