Discovery of Sulforaphane as an Inducer of Ferroptosis in U-937 Leukemia Cells: Expanding Its Anticancer Potential

SIMPLE SUMMARY: Ferroptosis and necroptosis are two non-apoptotic programmed cell death pathways with increasing therapeutic potential. The isothiocyanate sulforaphane (SFN) is a well-known naturally derived anticancer compound with remarkable pro-apoptotic activity. Its ability to promote non-apoptotic cell death mechanisms remains poorly investigated. This work discovered that SFN activates apoptosis and ferroptosis dose-dependently in acute myeloid leukemia cells. At lower concentrations, SFN induces caspase-dependent apoptosis. At higher concentrations, ferroptosis is activated and accompanied by the depletion of intracellular glutathione (GSH) and decreased GSH peroxidase 4 protein expression levels. Necroptosis, instead, is not involved in SFN-induced cell death. Considering that cancer cells resist pro-apoptotic treatments, SFN’s ability to induce different types of cell death delineates it as a promising anticancer agent. ABSTRACT: In recent years, natural compounds have emerged as inducers of non-canonical cell death. The isothiocyanate sulforaphane (SFN) is a well-known natural anticancer compound with remarkable pro-apoptotic activity. Its ability to promote non-apoptotic cell-death mechanisms remains poorly investigated. This work aimed to explore the capacity of SFN to induce non-apoptotic cell death modalities. SFN was tested on different acute myeloid leukemia cell lines. The mechanism of cell death was investigated using a multi-parametric approach including fluorescence microscopy, western blotting, and flow cytometry. SFN triggered different cell-death modalities in a dose-dependent manner. At 25 μM, SFN induced caspase-dependent apoptosis and at 50 μM ferroptosis was induced through depletion of glutathione (GSH), decreased GSH peroxidase 4 protein expression, and lipid peroxidation. In contrast, necroptosis was not involved in SFN-induced cell death, as demonstrated by the non-significant increase in phosphorylation of receptor-interacting protein kinase 3 and phosphorylation of the necroptotic effector mixed lineage kinase domain-like pseudokinase. Taken together, our results suggest that the antileukemic activity of SFN can be mediated via both ferroptotic and apoptotic cell death modalities.