Cancer chemoprevention by
benzyl isothiocyanate (BITC), which is derived from cruciferous vegetables like garden cress, in a transgenic mouse model of
breast cancer is associated with inhibition of
breast cancer stem-like cells (bCSC), but the molecular regulators of this effect remain elusive. This study demonstrates a protective effect of Krüppel-like factor 4 (KLF4)-p21CIP1 axis in bCSC inhibition by BITC. Exposure of human
breast cancer cells (MCF-7, MDA-MB-231, and SUM159) to plasma-achievable concentrations of BITC resulted in a robust induction of KLF4
mRNA and its
protein expression as determined by qRT-PCR and Western blotting or confocal microscopy. BITC-mediated suppression of bCSC markers, including
aldehyde dehydrogenase 1 activity and mammosphere frequency, was significantly augmented by transient or stable knockdown of KLF4. Western blotting and IHC revealed relatively higher levels of
KLF4 protein in mammary
tumor sections from BITC-treated mice in comparison with controls, but the difference was insignificant. Analysis of the
breast cancer RNA-Seq data from The
Cancer Genome Atlas indicated significant positive correlation between expression of KLF4 and that of p21CIP1 (CDKN1A) but not β-
Catenin (CTNNB1). Knockdown of p21CIP1
protein also amplified BITC-mediated suppression of bCSC. Finally, KLF4 was recruited to the promoter of p21CIP1 as indicated by
chromatin immunoprecipitation assay. These results indicate that induction of KLF4-p21CIP1 axis attenuates inhibitory effect of BITC on bCSC self-renewal. Translational implication of these findings is that
breast cancer chemoprevention by BITC may be augmented with a combination regimen involving BITC and an inhibitor of KLF4.