Sulphoraphane, a Dietary Component of Broccoli/Broccoli Sprouts,Inhibits Breast Cancer Stem Cells Yanyan Lia,b, Tao Zhanga, Hasan Korkayac, Suling Liuc, Hsiu-Fang Leea, Bryan Newmana,Yanke Yua, Shawn G. Clouthierc, Steven J. Schwartzb,*, Max S. Wichac,*, and Duxin Suna,*
a Department of Pharmaceutical Sciences, College of Pharmacy, University of Michigan, USA b Department of Food Science and Technology, The Ohio State University, USA c Comprehensive Cancer Center, Department of Internal Medicine, University of Michigan, USA
Abstract Purpose—The existence of cancer stem cells (CSCs) in breast cancer has profound implications for cancer prevention. In this study, we evaluated sulforaphane, a natural compound derived frombroccoli/broccoli sprouts, for its efficacy to inhibit breast CSCs and its potential mechanism.
Experimental Design—Aldefluor assay and mammosphere formation assay were used to evaluate the effect of sulforaphane on breast CSCs in vitro. A NOD/SCID xenograft model was employed to determine whether sulforaphane could target breast CSCs in vivo, as assessed by Aldefluor assay and tumor growth upon cell re-implantation in secondary mice. The potential mechanism was investigated utilizing Western blotting analysis and β-catenin reporter assay.
Results--Sulforaphane (1~5 μM) decreased aldehyde dehydrogenase (ALDH)-positive cellpopulation by 65%~80% in human breast cancer cells (P < 0.01), and reduced the size and number of primary mammospheres by 8~125-fold and 45%~75% (P < 0.01), respectively. Daily injection with 50 mg/kg sulforaphane for two weeks reduced ALDH-positive cells by more than 50% in NOD/SCID xenograft tumors (P = 0.003). Sulforaphane eliminated breast CSCs in vivo, thereby abrogating tumor growth after re-implantation of primary tumor cells into the secondary mice (P < 0.01).Western blotting analysis and β-catenin reporter assay showed that sulforaphane down-regulated Wnt/β-catenin self-renewal pathway.
Conclusions—Sulforaphane inhibits breast CSCs and down-regulates Wnt/β-catenin self-renewal pathway. These findings support the use of sulforaphane for chemoprevention of breast cancer stem cells and warrant further clinical evaluation.
Source : Cancer Res. 2010 May 1; 16(9): 2580–2590. doi:10.1158/1078-0432.CCR-09-2937. Link to Full Study
Sulforaphane inhibits histone deacetylase activity in BPH-1, LnCaP, and PC-3 prostate epithelial cells Melinda C. Myzak 1, Karin Hardin 2, Rong Wang 3, Roderick H. Dashwood 4, and Emily Ho 5 *
1 Linus Pauling Institute, Oregon State University, Corvallis, OR 97331; Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331 2 Department of Nutrition and Exercise Sciences, Oregon State University, Corvallis, OR 97331 3 Linus Pauling Institute, Oregon State University, Corvallis, OR 97331 4 Linus Pauling Institute, Oregon State University, Corvallis, OR 97331; Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331 5 Linus Pauling Institute, Oregon State University, Corvallis, OR 97331; Department of Nutrition and Exercise Sciences, Oregon State University, Corvallis, OR 97331
Sulforaphane (SFN), an isothiocyanate first isolated from broccoli,exhibits chemopreventive properties in prostate cancer cellsthrough mechanisms that are poorly understood. We recently reportedon a novel mechanism of chemoprotection by SFN in human coloncancer cells, namely the inhibition of histone deacetylase (HDAC).Here, we show that addition of 15 µM SFN also inhibitedHDAC activity by 40%, 30% and 40% in BPH-1, LnCaP, and PC-3prostate epithelial cells, respectively. The inhibition of HDACwas accompanied by a 50-100% increase in acetylated histonesin all three prostate cell lines, and in BPH-1 cells treatedwith SFN there was enhanced interaction of acetylated histoneH4 with the promoter region of the P21 gene and the bax gene.A corresponding 1.5 to 2-fold increase was seen for p21Cip1/Waf1and Bax protein expression, consistent with previous studiesusing HDAC inhibitors such as trichostatin A. The downstreamevents included cell cycle arrest and activation of apoptosis,as evidenced by changes in cell cycle kinetics and inductionof multi-caspase activity. These findings provide new insightinto the mechanisms of SFN action in benign prostate hyperplasia,androgen-dependent prostate cancer, and androgen-independentprostate cancer cells, and they suggest a novel approach tochemoprotection and chemotherapy of prostate cancer throughthe inhibition of HDAC
In summary, the present investigation has established an association between inhibition of HDAC activity, increased histone acetylation on bax and P21 promoters, elevated bax RNA and protein expression, and concomitant increase in cell cycle arrest and apoptotic markers after SFN treatment (Figure 7). These results suggest that SFN may be effective against benign prostate hyperplasia, androgen-dependent prostate cancer and androgen-independent prostate cancer potentially through the inhibition of HDAC activity. The present work focused on p21 and Bax, which are well-established targets of HDAC inhibitors and key regulators of cell cycle kinetics and apoptosis, but additional targets of HDAC inhibition warrant further investigation. Collectively, the results suggest that, in addition to its well-recognized effects on Phase 2 pathways, an alterative mechanism by which SFN can modulate gene expression is through the inhibition of HDAC activity, leading to apoptosis induction in cancer cells. The convergence of multiple mechanisms has many advantages; the present results and published data clearly indicate that SFN should be useful both as a chemopreventive agent and as a chemotherapeutic agent in the prostate