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 nested case-control study was designed to investigate whether the association between carotenoid consumption and risk of breast cancer is related to mammographic density. High breast density as measured by mammography has been reported to be a powerful indicator of increased breast cancer risk. The study included 604 breast cancer cases and 626 cancer-free controls in the Nurses' Health Study for whom circulating carotenoid (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin) levels had been measured and mammograms obtained prospectively. Using a computer-assisted method to determine mammographic density, circulating carotenoids were not found to be associated with mammographic density. However, mammographic density significantly influenced the association between total circulating carotenoids and risk of breast cancer (P heterogeneity = 0.008). Total circulating carotenoid levels were found to be inversely associated with overall breast cancer risk (P trend = 0.01). Among women in the highest third of mammographic density, total circulating carotenoids were associated with a 50% lower risk of breast cancer (odds ratio = 0.5; 95% confidence interval = 0.3 - 0.8). Similarly, among these women, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were found to be associated with a significant 40% to 50% reduction in risk of breast cancer (P trend < 0.05). On the other hand, no such inverse association was observed between circulating carotenoids and breast cancer risk among study participants with low mammographic density. The authors conclude that plasma levels of carotenoids may play a role in reducing risk of breast cancer, especially among women with high breast density.

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.

Indole-3-carbinol, a phytochemical derived from cruciferous vegetables such as broccoli and brussels sprouts, is a powerful antiproliferative in human breast cancer cells and can decrease metastatic spread of tumors in experimental animals. The current study demonstrated that indole-3-carbinol significantly decreased the in vitro migration of MDA-MB-231 breast cancer cells, a highly invasive cell line. The data demonstrated that indole-3-carbinol induces stress fibers and peripheral focal adhesions and that this leads to a reduction in motility of human breast cancer cells.

The present study determined how cooking influenced in vitro bile acid binding of various vegetables using a mixture of bile acids secreted in human bile under physiological conditions. Greater bile acid binding potential has been associated with lower risk of heart disease and cancer. The bile acid binding capacity of food and food components has been related to their cholesterol-lowering potential. Lowered recirculation of bile acids results in the use of cholesterol in the body to synthesize bile acid and reduced fat absorption. Secondary bile acids have been related to increased risk of cancer. Incubations were conducted for each treatment simulating gastric and intestinal digestion. Cholestyramine (a cholesterol-lowering, bile acid binding drug) was used as the positive control treatment and cellulose as the negative control. Relative to cholestyramine, in vitro bile acid binding on dry matter basis was 13% for the collard greens, mustard greens, and kale; 10% for broccoli; 8% for Brussels sprouts and spinach; 7% for green bell pepper; and 5% for cabbage. These results point to the significantly different (P ≤ .05) health-promoting potential of the vegetables, with collard greens, mustard greens and kale in the top group. Steam cooking was found to significantly improve the in vitro bile acid binding of collard greens, mustard greens, kale, broccoli, green bell pepper, and cabbage compared to the bile acid binding values for these vegetables in raw form. The authors conclude that when consumed regularly after steam cooking, including more of these green and leafy green vegetables would lower the risk of cardiovascular disease and cancer.

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.

Oral administration of either the isothiocyanate, sulforaphane, or its glucosinolate precursor, glucoraphanin, has been found to inhibit mammary carcinogenesis in rats treated with 7,12-dimethylbenz[a]anthracene. The present study was designed to determine whether sulforaphane exerts a direct chemopreventive action on animal and human breast tissue. The pharmacokinetics and pharmacodynamics of a single oral dose of sulforaphane were studied in the rat mammary gland. Sulforaphane metabolites were detected at concentrations sufficient to alter gene expression in cell culture. In a small pilot study, eight healthy women undergoing breast reduction were given a single oral dose of a broccoli sprout preparation containing 200 µmol of sulforaphane. Following the dosing, sulforaphane metabolites were readily measurable in human breast tissue.

The current case-control study was designed to compare the diets of a group of Korean breast cancer patients with a healthy control group. The cases included 97 women with newly confirmed diagnoses of breast cancer at the inpatient or outpatient clinic of Yeouido St. Mary’s Hospital in Seoul, and excluded women with any history of liver diseases, diabetes mellitus, respiratory disorders and cardiovascular diseases. The 97-person control group also excluded women with known malignant, hormonal, gynecological or endocrine diseases. Intake of nutrients in 117 food items were estimated in the breast cancer patients and age-matched healthy controls using a quantitative food frequency questionnaire administered by a trained dietitian. The questionnaire also included general information (age, sex and marital status), age at menarche, and pregnancy history. It was found that the average caloric intake of the breast cancer patients and the healthy controls did not differ significantly. However, the breast cancer patients consumed significantly less fat and antioxidant nutrients such as vitamin A, retinol, beta-carotene, vitamin C and vitamin E than did the controls. Consumption of eggs (p<0.01), legumes (p<0.05), vegetables (p<0.05), seasonings (p<0.001), and oils and fats (p<0.01) was significantly lower in the breast cancer patients. However, the level of energy from fat is relatively low in Korean patients compared to their Western counterparts, and fat consumption may not be an independent risk factor at this level of intake. With respect to particular foods, in addition to eggs, the breast cancer patients consumed a significantly lower quantity of bean curd (tofu), onion, garlic, green pepper, sweet pepper, kale, cucumber, seasoned bean sprouts, sesame leaf, zucchini, radish, mushroom, crown daisy, red pepper paste, bean paste, spicy bean paste, orange juice, grape juice, and tomato juice than the controls. On the other hand, the breast cancer patients consumed significantly greater quantities of cooked rice, noodles, deep fried chicken, satsuma mandarin, Korean melon, kimchi and coffee than the controls. The authors conclude that since the breast cancer patients consumed less soy and vegetables, they had a lower intake than the controls of rich sources of antioxidant nutrients, phytosterols, fiber and non-nutritional components that may reduce the risk of cancer. In addition, the breast cancer patients in this study consumed lower quantities of red pepper paste, bean paste and spicy bean paste, causing their intake of pepper flavonols (which may have a protective effect on breast cancer risk) to be lower than that of the controls.

Isothiocyanates are important anticarcinogenic phytochemicals abundant in broccoli sprouts. Recent studies have indicated that some isothiocyanates might act selectively exclusively against cancer cells. The current study compared the effects of major isothiocyanates, sulforaphane and its sulfide analog erucin, on breast cancer (MCF7) and normal human mammary epithelial cells (HMEpC). It was found that sulforaphane and erucin inhibited cell proliferation approximately two times more potently in breast cancer than in normal cells. It was also determined that isothiocyanates blocked breast cancer cells in prometaphase stage of mitosis by disrupting spindle formation and preventing proper chromosome segregation. Interestingly, sulforaphane and erucin did not induce mitotic arrest in normal cells at the same concentrations. However, some aberrant mitotic spindles with abnormal chromosome segregation were observed in the normal cells. Furthermore, both sulforaphane and erucin induced microtubule depolymerization in interphase breast cancer and normal cells in a concentration dependent manner. Breast cancer cell growth inhibition was accompanied by a significant time- and dose-dependent induction of apoptosis by both isothiocyanates. High concentrations of sulforaphane and erucin also induced significant killing of normal cells. The authors conclude that isothiocyanates are active in both normal and cancerous cells and that there remain important questions regarding the proper implementation and suitability of isothiocyanates in cancer prevention.

The phytochemical indole-3-carbinol (I3C) (present in broccoli and other cruciferous vegetables) and its major acid-catalyzed reaction product 3,3'-diindolylmethane (DIM) have been shown to inhibit carcinogenesis. The present study investigated the effect of DIM on angiogenesis and tumorigenesis in a mouse model. DIM effected a concentration-dependent decrease in proliferation, migration, invasion and capillary tube formation of cultured human umbilical vein endothelial cells. DIM also inhibited the growth of human MCF-7 breast cancer cell tumor xenografts by up to 64% in female mice, compared to the controls.

740 Caucasian women with breast cancer from Erie and Niagara counties were frequency matched to 810 community controls by age and county. An in-depth interview was given in person. Consumption of cruciferous vegetables, particularly broccoli, was marginally inversely associated with breast cancer risk in premenopausal women. Associations were weaker or non-existent among postmenopausal women.

The current study used in vitro and in vivo experiments to examine the inhibition of nitrosation by strawberry, garlic, and kale. Strawberry, garlic, and kale extracts were all found to inhibit chemical nitrosation in vitro. However, garlic extract showed the greatest ability to inhibit the nitrosation. A garlic methanol-soluble fraction of the garlic extract was fractionated into G1-G4 fractions. Fraction G1 was found to inhibit the formation of N-nitrosodimethylamine (NDMA), a human carcinogen, by 84%. The formation of NDMA in humans after administration of nitrate (400 mg/day) in combination with an amine-rich diet was also studied. Whole strawberries (300 g), garlic juice (200 g: 75 g garlic juice in drinking water), or kale juice (200 g) were administered to 27 males and 13 females. Nitrate intake caused a significant rise in salivary and urinary nitrate concentrations and salivary nitrite concentrations. When whole strawberries, garlic juice, or kale juice were provided immediately after an amine-rich diet with a nitrate, NDMA excretion was found to decrease by 70%, 71%, and 44%, respectively. The authors conclude that consumption of whole strawberries, garlic juice, or kale juice can reduce endogenous NDMA formation.

Animal studies have shown that intake of the carcinogen benzo[a]pyrene, a polycyclic aromatic hydrocarbon, causes increases in tumor levels, particularly in the upper gastrointestinal tract. However, the role of benzo[a]pyrene in food and cancer in humans is unclear. The authors created a benzo[a]pyrene database of selected foods that could be used in combination with a food frequency questionnaire to estimate benzo[a]pyrene intake. Meat samples were prepared by different cooking techniques in controlled conditions, and by several restaurants and fast-food chains. Other foods were purchased from major national supermarket chains. Benzo[a]pyrene levels were measured for each food. The database was linked to the results from the food frequency questionnaire to estimate the daily benzo[a]pyrene intake through food in 228 subjects in Washington, DC. The highest concentrations of benzo[a]pyrene (up to approximately 4 ng benzo[a]pyrene/g of cooked meat) were found in grilled or barbecued very well done steaks and hamburgers and in grilled or barbecued well done chicken with skin. Benzo[a]pyrene levels were found to be lower in meats that were grilled or barbecued to medium done and in all broiled or pan-fried meat samples independent of doneness level. The benzo[a]pyrene levels in non-meat items generally were low. However, some cereals and greens (e.g. kale, collard greens) had levels of benzo[a]pyrene up to 0.5 ng/g. In the study population, the bread/cereal/grain and grilled/barbecued meat, respectively, contributed 29 and 21 percent to the average daily intake of benzo[a]pyrene.

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.