Breast cancer is a leading cause of cancer-related deaths among women in the United States. Over the last decade, breast cancer stem cells (bCSC) have been identified and characterized as a key player in breast cancer progression and recurrence. Benzyl isothiocyanate (BITC) is a highly promising cancer chemopreventive constituent of edible cruciferous vegetables such as garden cress. We have shown previously that BITC inhibits bCSC in cultured breast cancer cells (MCF-7 and SUM159 cells) and in spontaneous tumors of mouse mammary tumor virus-neu (MMTV-neu) mice in vivo. Krüppel-like factor 4 (KLF4), a zinc finger transcription factor, is known as both oncogene and tumor suppressor in various types of human cancers and plays an important role in reprogramming differentiated somatic cells into induced pluripotent stem cells. The present study demonstrates that KLF4 impedes bCSC inhibition by BITC. Exposure of breast cancer cells (MCF-7, MDA-MB-231, and SUM159) to pharmacological concentrations of BITC (2.5 and 5 µM) resulted in induction of KLF4 protein, which was accompanied by increase of its transcription. In addition, BITC treatment increased nuclear level of KLF4 in breast cancer cells. KLF4 protein expression was also higher in tumors form BITC-treated MMTV-neu mice compared with the control group. Ectopic expression of KLF4 in MCF-7 cells conferred marked protection against BITC-mediated inhibition of bCSC as evidenced by aldehyde dehydrogenase 1 (ALDH1) activity. Consistent with these observations, BITC-mediated inhibition of bCSC in MCF-7, MDA-MB-231 and SUM159 cells was significantly augmented by RNA interference of KLF4 as evidenced by ALDH1 activity and frequency of mammospheres. KLF4 overexpression also increased cell migration capacity of MCF-7 cells. Furthermore knockdown of KLF4 augmented BITC-mediated inhibition of cell migration in SUM159 cells. These results suggest that anticancer activity of BITC may be enhanced by KLF4 inhibition or knockdown in breast cancer cells. This study was supported by the grant RO1 CA129347-09 awarded by the National Cancer Institute.

Citation Format: Su-Hyeong Kim, Yong Wan, Shivendra V. Singh. Breast cancer stem cell inhibition by benzyl isothiocyanate is hampered by induction of Kruppel-like factor 4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5265. doi:10.1158/1538-7445.AM2017-5265