Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Cancer Prev Res (Phila). 2019 Mar;12(3):125-134. doi: 10.1158/1940-6207.CAPR-18-0393. Epub 2019 Feb 5.
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)-p21 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 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 and that of () but not (). Knockdown of p21 protein also amplified BITC-mediated suppression of bCSC. Finally, KLF4 was recruited to the promoter of as indicated by chromatin immunoprecipitation assay. These results indicate that induction of KLF4-p21 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.
苯乙基异硫氰酸酯（BITC）可抑制乳腺癌干细胞样细胞（bCSC），从而实现癌症化学预防，这种作用源自十字花科蔬菜，如荠蓝。然而，调控这种作用的分子机制仍不清楚。本研究表明，Krüppel 样因子 4（KLF4）-p21 轴在 BITC 抑制 bCSC 中发挥保护作用。用可达到血浆浓度的 BITC 处理人乳腺癌细胞（MCF-7、MDA-MB-231 和 SUM159），通过 qRT-PCR、Western blot 或共聚焦显微镜确定，可显著诱导 mRNA 及其蛋白表达。瞬时或稳定敲低 KLF4 可显著增强 BITC 对 bCSC 标志物的抑制作用，包括醛脱氢酶 1 活性和类乳腺球体形成频率。Western blot 和免疫组化显示，与对照组相比，BITC 处理组小鼠乳腺肿瘤组织中 KLF4 蛋白水平相对较高，但差异无统计学意义。对癌症基因组图谱中的乳腺癌 RNA-Seq 数据进行分析表明，在表达水平上，与 呈显著正相关（），但与 （）不相关。p21 蛋白的敲低也放大了 BITC 对 bCSC 的抑制作用。最后，染色质免疫沉淀试验表明 KLF4 被募集到 基因的启动子上。这些结果表明，KLF4-p21 轴的诱导减弱了 BITC 对 bCSC 自我更新的抑制作用。这些发现的转化意义在于，BITC 可增强乳腺癌化学预防，其联合方案包括 BITC 和 KLF4 抑制剂。
