The present study was designed to investigate the mechanism by which the cruciferous vegetable compound benzyl isothiocyanate suppresses the viability of human breast cancer cells. Benzyl isothiocyanate has been shown to inhibit the growth of both hormone receptor positive MCF-7 and hormone receptor negative MDA-MB-231 human breast cancer cells and also to retard mammary cancer development in MMTV-neu mice by causing apoptosis. However, but the mechanism of cell death is not fully understood. The authors show that whereas p53 is not required for benzyl isothiocyanate-induced cell death, proapoptotic response to benzyl isothiocyanate is mediated by suppression of X-linked inhibitor of apoptosis (XIAP) protein expression. Benzyl isothiocyanate treatment heightened levels of total and Ser15-phosphorylated p53 protein in MCF-7 breast cancer cells, but the proapoptotic response to benzyl isothiocyanate remained even after knockdown of the p53 protein level. In both MCF-7 and MDA-MB-231 cells, exposure to benzyl isothiocyanate caused in a marked decrease in protein level of XIAP as soon as eight hours after treatment. Ectopic expression of XIAP was found to confer statistically significant protection against benzyl isothiocyanate-mediated cytoplasmic histone-associated apoptotic DNA fragmentation in both breast cancer cell types. In addition, inhibition of implanted MDA-MB-231 cell growth in female athymic mice by benzyl isothiocyanate administration was related to a modest but statistically significant decrease in XIAP protein level. The benzyl isothiocyanate treatment also was found to cause induction as well as nuclear translocation of survivin only in the MCF-7 cells. Furthermore, the benzyl isothiocyanate-induced apoptosis was modestly but statistically significantly augmented by RNA interference of survivin in MCF-7 breast cancer cells. The authors comment that their study provides new insight into the molecular mechanism of benzyl isothiocyanate-induced apoptosis. In particular, suppression of XIAP expression is a critical mediator of this process.

The present study was designed to investigate how histone deacetylase (HDAC) inhibition affects tamoxifen-induced autophagy in breast cancer cells. Autophagy is a type of cell self-digestion which can stop normal cells from developing into cancer cells and lead to cell death. However, autophagy can also protect breast cancer cells by neutralizing the effectiveness of anticancer drugs. Most patients with estrogen receptor-positive (ER+) breast cancer who experience an initial response to tamoxifen or aromatase inhibitors eventually develop resistance. In fact, many breast tumors are resistant to anti-estrogens from the outset of treatment. One of the known survival strategies of breast cancer cells treated with hormone therapy is the induction of autophagy. During autophagy, cellular components are catabolized in autophagic lysosomes, enabling the removal of damaged organelles and recycling of nutrients during periods of starvation. Treatment with both aromatase inhibitors and tamoxifen has been shown to be associated with upregulating expression of the essential autophagy protein beclin-1. Reduction of autophagy in breast cancer cells increases the cytotoxicity of tamoxifen, suggesting that autophagy in such cells is oncogenic and that autophagy is a potential contributor to tamoxifen resistance. The authors have demonstrated that the cytotoxicity of tamoxifen in breast cancer cells is enhanced by HDAC inhibitors, raising the possibility that HDAC inhibitors achieve synergy with tamoxifen by inhibiting autophagy. In the current study, several HDAC inhibitors were found to cause a synergistic increase in apoptosis and cell death in combination with tamoxifen. Adding an HDAC inhibitor to tamoxifen resulted in enhanced autophagy, in a time- and dose-dependent manner. However, HDAC inhibition promotes transition from autophagic cell preservation to apoptotic cell death. Functional estrogen-mediated signaling was found to be required for such increased autophagy; depletion of ER by siRNA or treatment with fulvestrant did not result in increased autophagy. The authors note that breast cancer cells react with an autophagic survival response as a result of nutrient starvation, tamoxifen treatment, and exposure to DNA damaging agents. The study findings further suggest that HDAC inhibitors act in synergy with tamoxifen to prevent the excess of autophagic lysosomes from sustaining self-preservation, thereby triggering elimination of cells by apoptotic cell death in a fatal switch. The authors conclude that combining tamoxifen with an HDAC inhibitor may represent a new therapeutic approach to overcome hormone therapy resistance.

Sulforaphane [1-isothiocyanato-4-(methylsulfinyl)butane] is an isothiocyanate in cruciferous vegetables with a number of potential chemopreventive actions. The current study examined the effects of sulforaphane on the proliferation of human MCF-7 breast cancer cells and on the expression of estrogen receptor α (ERα) protein and mRNA in the cells. Sulforaphane was found to inhibit cell proliferation and ERα protein expression. Lowered ERα expression was also found to be accompanied by decreased progesterone receptor expression. MCF-7 cell mRNA expression was inhibited by sulforaphane at relatively high doses, but not at low sulforaphane concentrations. The authors conclude that sulforaphane can inhibit proliferation of MCF-7 breast cancer cells and down-regulation of hormone receptor expression.

The active estrogens important to the proliferation of breast cancer are formed from inactive precursors by the action of aromatase encoded by the CYP19 gene. Epidemiological studies have shown that consumption of raw or short-cooked cabbage and sauerkraut is associated with a significant reduction in breast cancer. The aim of the present study was to investigate the effect of indole-3-carbinol (I3C), 3,3'-diindolylmethane (DIM) — a major in vivo acid-catalyzed condensation product of I3C, and sulforaphane (SUL) on CYP19 expression in human breast cancer estrogen-dependent MCF-7 cells. MCF-7 cells were treated with these three compounds at the concentrations relevant to those observed in human plasma. It was found that I3C in the dose of 30 µM reduced the expression of CYP19 in MCF-7 cells. In contrast, higher doses of I3C (50 µM) actually induced its expression. SUL in doses of 5µM and 20µM reduced the level of CYP19 mRNA. Similar results were observed after treatment with 5 µM and 10 µM of DIM.

In the present study, the levels of vitamin C, total phenolics, anthocyanins, hydroxybenzoic and hydroxycinnamic acids, and radical scavenging activity were assessed in two varieties of red cabbage before and after conventional boiling and steam cooking. After conventional cooking, 32.7-64.5% of vitamin C and 45.7-66.9% of total phenolics were retained in the cooked cabbage. Reducing cooking water volume by half led to more favorable retention of both phenolics (by 2.7-14.5%) and vitamin C (by 14.2-18.4%). However, cutting the cooking time in half affected the retention of phenolics and vitamin C by only 3.8-6.7% and 0-2.2%, respectively. Steam-cooking was recommended to prevent significant loss of antioxidant activity, because when steamed, the antioxidant capacity of red cabbage was reduced by only 5-20%.

The present case-control population study investigated the independent and combined effects of Brassica vegetable intake and the GSTP1 Ile105Val genetic polymorphism on breast cancer risk. The study included 3,035 cases and 3,037 controls in the Shanghai Breast Cancer Study for whom diet and genetic data were available (87% of cases and 85% of controls). Cruciferous vegetables are the main dietary source of isothiocyanates and other glucosinolate derivatives that are known to induce phase II detoxifying enzymes, including glutathione S-transferases (GSTs). The GSTP1 Val/Val genotype was found to be significantly associated with greater risk of breast cancer (OR = 1.50; 95% CI: 1.12 - 1.99). The association was significantly higher in premenopausal women (OR = 1.69; 95% CI: 1.17- 2.43) than in postmenopausal women (OR = 1.20; 95% CI: 0.74-1.92). While total overall cruciferous vegetable consumption was not significantly associated with breast cancer risk, women reporting greater turnip and Chinese cabbage intakes were found to have a significantly lower postmenopausal breast cancer risk. Women with the GSTP1 Val/Val genotype and low cruciferous vegetable intake had a 1.74-times higher breast cancer risk than that of women with the Ile/Ile or Ile/Val genotype (95% CI: 1.13, 2.67). This association between low cruciferous vegetable intake and the Val/Val genotype was found predominantly among premenopausal women (OR = 2.08; 95% CI = 1.20, 3.59). The authors conclude that cruciferous vegetable intake may reduce breast cancer risk through high isothiocyanate exposure. Cruciferous vegetable consumption may also ameliorate the effects of the GSTP1 genotype.

Based on epidemiologic evidence, high dietary intake of brassica vegetables such as broccoli, cabbage, and brussels sprouts protects against tumorigenesis in multiple organs. Previously, the authors showed that 3,3'-Diindolylmethane, one of the active compounds derived from brassica vegetables, induced cell cycle arrest in human breast cancer MCF-7 cells by a mechanism that included increased expression of p21. In the present study, the events leading to p21 overexpression were further investigated. The study establishes the critical role of enhanced mitochondrial ROS release in 3,3'-diindolylmethane-induced p21 up-regulation in human breast cancer cells.

Brassica vegetable (e.g., Chinese cabbage) consumption provides isothiocyanates (ITC) and other glucosinolate derivatives capable of inducing apoptosis, changing steroid hormone metabolism, regulating estrogen receptor response, and attenuating cellular proliferation. The present study investigated the rates of breast cancer in Shanghai, China, using urinary isothiocyanate (ITC) levels as a biological measure of glucosinolate intake. A representative subgroup of 337 cases providing presurgery, fasting, and first-morning urine specimens was matched by age, menopausal status, date of urine collection, and day of laboratory assay to population controls. Urinary ITC levels were found to be inversely related to breast cancer adjusted for age, menopausal status, soy protein, fibroadenoma history, family breast cancer, physical activity, waist-to-hip ratio, body mass index, age at menarche, and parity. This protective association was found in both premenopausal and postmenopausal women. In contrast, total brassica vegetable intake estimated from a food questionnaire was not found to be associated with breast cancer. The authors conclude that greater brassica vegetable consumption was associated with significantly reduced breast cancer risk among Chinese women.

The present study evaluated the effects of sauerkraut fermentation. Cabbage was fermented with a starter culture and compared to the results of spontaneous fermentation. Of 20 different flavonoids tested, only kaempferol was found. The content of kaempferol remained constant in the cabbage over the fermentation process. The total glucosinolate content in the raw material was 3.71 micro mol/g DW, dry weight, whereas glucosinolates were totally decomposed in both fermentations during two weeks. Isothiocyanates, indole-3-carbinol, goitrin, allyl cyanide, and nitriles were found in the fermented cabbage. Isothiocyanates and allyl cyanide were the predominant breakdown products in both fermentations. Sulforaphane nitrile and goitrin were found only in small quantities in the sauerkraut.

Cruciferous vegetable extracts from freeze-dried cabbage, freeze-dried fermented cabbage, and acidified brussels sprouts were prepared by exhaustive extraction with ethyl acetate. Estrogenic and antiestrogenic effects of these extracts were analyzed. To determine whether the extracts are potential estrogen receptor (ER) ligands that can act as agonists or antagonists, the binding affinity of extracts for the ER was measured. The extracts were found to bind with low affinity to the ER, and the relative binding affinity ranking was estradiol > freeze-dried fermented cabbage > freeze-dried cabbage > acidified brussels sprouts. The extracts were then evaluated for their estrogenic and antiestrogenic activities in estrogen-dependent human breast cancer (MCF-7) cells. At low concentrations, all of the extracts reduced estradiol-induced MCF-7 cell proliferation. At higher extract concentrations, however, the extracts increased proliferation in MCF-7 cells. Similarly, expression of the pS2 gene was induced by higher extract concentrations. The pure estrogen antagonist ICI 182,780 suppressed the cell proliferation induced by the extracts as well as by estradiol and also the induction of pS2 expression by the extracts. Growth of the ER-negative MDA-231 breast cancer cells was not affected by the extracts or by estradiol. The authors conclude that cruciferous vegetable extracts act bifunctionally, like an antiestrogen at low concentrations and an estrogen agonist at high concentrations.

Previous studies indicate that the estrogen metabolite 16alpha-hydroxyestrone acts as a breast cancer promoter. The alternative product of estrogen metabolism, 2-hydroxyestrone, does not exhibit estrogenic properties in breast tissue. Therefore, low values of the ratio 2-hydroxyestrone to 16alpha-hydroxyestrone (2:16) in urine may be a marker for greater breast cancer risk. Brassica vegetables such as broccoli may shift estrogen metabolism and increase the 2:16 ratio. In the current study, 34 healthy postmenopausal women participated in an intensive intervention designed to facilitate the addition of brassica vegetables to the daily diet. With adjustment for other dietary parameters, brassica vegetable consumption was associated with a statistically significant increase in 2:16 values. The authors conclude that to the extent that the 2:16 ratio is associated with breast cancer risk, future research should consider brassica vegetable consumption as a potentially effective dietary strategy to prevent breast cancer.

Mammary cancer was induced in female Sprague-Dawley rats by a single injection of N-methyl-N-nitrosourea (MNU) and rats were randomized to control fat (5%) and high fat (24.6%) diets. un addition, dried cabbage (5 and 10%) and collards (5%) were included in the diets of some animals. No statistically significant differences were observed in food consumption, body wt gain and caloric intake between the MNU-treated and control groups in the rats fed the low-fat diet. However, the groups fed the high-fat diet consumed more than the rats maintained on the control diet. The rats on the control fat diet containing cabbage exhibited a significantly lower incidence of mammary cancer than rats that were fed the control-fat diet without cabbage. This effect was not observed in comparable rats on the high-fat diet. The inhibitory effect on mammary tumorigenesis was demonstrated using a residue obtained from cabbage by exhaustive extraction with methanol, methylene chloride and petroleum ether. These studies reinforce the efficacy of cabbage as a ‘suppressor’ of cancer in experimental model systems under control-fat dietary conditions.