Sulforaphane Potentiates the Efficacy of Imatinib against Chronic Leukemia Cancer Stem Cells through Enhanced Abrogation of Wnt/β-Catenin Function

Sulforaphane (SFN) has been indicated for the prevention and suppression of tumorigenesis in solid tumors. Herein, we evaluated SFN's effects on imatinib (IM)-resistant leukemia stem cells (LSCs). CD34(+)/CD38(-) and CD34(+)/CD38(+) LSCs were isolated from KU812 cell line flowcytometrically. Isolated LSCs showed high expression of Oct4, CD133, β-catenin, and Sox2 and IM resistance. Differentially, CD34(+)/CD38(-) LSCs demonstrated higher BCR-ABL and β-catenin expression and imatinib (IM) resistance than CD34(+)/CD38(+) counterparts. IM and SFN combined treatment sensitized CD34(+)/CD38(-) LSCs and induced apoptosis, shown by increased caspase 3, PARP, and Bax while decreased Bcl-2 expression. Additionally, the combined treatment reduced BCR-ABL and β-catenin and MDR-1 protein expression. Mechanistically, IM and SFN combined treatment resensitized LSCs by inducing intracellular reactive oxygen species (ROS). Importantly, β-catenin-silenced LSCs exhibited reduced glutathione S-transferase pi 1 (GSTP1) expression and intracellular GSH level, which led to increased sensitivity toward IM and SFN. We demonstrated that IM and SFN combined treatment effectively eliminated CD34(+)/CD38(-) LSCs. Since SFN has been shown well tolerated in both animals and human, this regimen could be considered for clinical trials.