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Anti-cancer effect of broccoli and broccoli sprouts |
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Brook and co-workers at Department of Urology, Stanford University, concluded that sulforaphane, a phytochemical of broccoli, is a potent inducer of phase-2-enzymes in human prostate cells, but the exact mechanism by which sulforaphane acts on prostate cancer cells is still unclear and more studies are required [1]. They studied the effect of sulforaphane and extracts from broccoli sprouts on different human prostate cell lines and found that all 5 prostate cancer cell lines tested, sulforaphane increased phase-2-enzyme activation. Scientists at The Johns Hopkins University School of Medicine, Baltimore, investigate the inhibitory action of sulforaphane against Helicobacter pylori, a main risk factor for the development of stomach ulcers and stomach cancer [2]. They found that sulforaphane had significantly more bacteriostatic activity than other phytochemicals such as resveratrol, allix and epigallocatechin. They also found that sulforaphane halted the development of stomach tumours in mice, which were treated with the carcinogen benzo-a-pyrene. The scientists concluded that the sulforaphane could eradicate resistant strains of Helicobacter pylori.
Li and co-workers at University of Michigan evaluated sulforaphane for its efficacy to inhibit breast cancer stem cells, using an immunodeficient xenograft mice model [3]. Injection of sulforaphane eliminated breast cancer stem cells and stopped tumor growth after the reimplantation of primary tumor cells into the secondary mice. The scientists concluded that thier findings support the use of sulforaphane for the chemoprevention of breast cancer stem cells and warrant more clinical studies.
A Japanese study conducted by Kenji Niwa and co-workers at the Gifu University School of Medicine, Japan, tested the protective effects of indole-3-carbinol, another typical phytochemical of broccoli, against the carcinogens N-methyl-N-nitrosourea and 17 beta-estradiol [4]. They concluded that indole-3-carbinol can act as a chemopreventive agent on estrogen mediated endometrial tumorigenesis and that the ingestion of cruciferous vegetables could help to reduce the risk of human endometrial cancer.
Gasper and co-workers at the Institute of Food Research, Colney, UK, were the first to investigate the effect of the consumption of broccoli and a high sulforaphane broccoli (a special cultivar containing about 3 times more sulforaphane than standard broccoli) on the expression of anti-cancer genes in gastric mucosal tissue [5]. Previous studies have demonstrated that sulforaphane induces xenobiotic metabolizing genes and induces genes associated with cell cycle arrest and apoptosis. The scientists tested the intake of broccoli, in the form of soup, on sixteen persons in crossover dietary trial. They found that the consumption of high sulforaphane broccoli resulted in up-regulation of a small number of xenobiotic metabolizing genes, whereas standard broccoli only up-regulated 1 such gene. The sulforaphane concentrations in the standard broccoli soup were probably too low to induce change in gene expression. The broccoli soups were prepared in such a way to obtain maximum sulforaphane, meaning that in any domestic situation the effects will even be lower. The authors also mentioned that habitual consumption of broccoli and other cruciferous vegetables may result in long term changes in gene expressions, different from those observed in their study.
[1] Potent induction of phase-2-enzymes in human prostate cells by sulforaphane. Cancer Epidemiology Biomarkers and Prevention, Vol. 10, 949-954, September 2001.
[2] Sulforaphane inhibits extracellular, intracellular, and antibiotic-resistant strains of Helicobacter pylori and prevents benzo-a-pyrene-induced stomach tumors. PNAS,May 28, 2002;99(11):7610-7615.
[3] Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells. Clin Cancer Res. 2010 May 1;16(9):2580-90.
[4] Preventive Effects of Indole-3-Carbinol on Endometrial Carcinogenesis in Mice. Japanese Journal of Reproductive Endocrinology, 2004.
[5] Consuming broccoli does not induce genes associated with xenobiotic metabolism and cell cycle control in human gastric mucosa. J Nutr. 2007 Jul;137(7):1718-24.
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