Phenethyl isothiocyanate and sulforaphane have been shown to exhibit tumor preventive activity in lung, prostate, breast and colon cancers. The present study was designed to assess the effect of these two isothiocyanates on estrogen receptor-related genes, as well as genes related to apoptosis in estrogen-dependent MCF7 breast cancer cells and normal human epithelial breast cells. The two types of cells were treated with 0.3 然 or 3.0 然 concentrations of phenethyl isothiocyanate or sulforaphane. In the normal breast cells, gene expression was significantly altered for 23 genes by phenethyl isothiocyanate at 0.3 然 and four genes at 3.0 然. Sulforaphane changed the expression of 16 genes at 0.3 然 and 2 genes at 3.0 然. In the normal breast cells, the genes altered by both substances exhibited changes in gene expression that were similar in extent as well as in direction of change. In the MCF-7 breast cancer cells, treatment with phenethyl isothiocyanate did not result in any significant changes in the gene expression at either treatment level. Sulforaphane treatment produced significant changes in seven genes, but only at the higher concentration level of 3.0 然. Normal breast cells had more changes in the expression of estrogen receptor-related genes than did breast cancer cells, and, importantly, these changes occurred predominantly at the low concentration level of 0.3 然, a concentration achievable by dietary input of isothiocyanates. New findings were the upregulation of the pro-apoptotic gene BAD and estrogen receptor beta gene in normal human mammary cells. The authors conclude that the observed gene alterations, along with upregulation of tumor suppressors p21 and p27, may provide a protective effect against breast cancer in mammary cells.

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.

Sulforaphane, an important isothiocyanate present in cruciferous vegetables, is believed to be partially responsible for the chemopreventive activity of such vegetables. Sulforaphane arrests mitosis, possibly by altering spindle microtubule function. A critical property of microtubules is their rapid growth and shortening dynamics (dynamic instability). Suppression of dynamics by antimitotic anticancer drugs such as the taxanes and vinca alkaloids is central to the anticancer mechanisms of the drugs. It was found that sulforaphane significantly changed microtubule organization in arrested spindles without modulating the spindle microtubule mass at concentrations that inhibited proliferation and mitosis of MCF7-green fluorescent protein--tubulin breast tumor cells by 50% (i.e.,15 然), in a manner similar to that of much stronger antimitotic drugs. By using quantitative fluorescence video microscopy, it was determined that at this concentration, sulforaphane suppressed dynamic instability with a direct effect on the microtubules. The authors conclude that sulforaphane arrests proliferation and mitosis of breast cancer cells in a manner weaker than but similar to more powerful clinically used antimitotic chemotherapy drugs.

Cisplatin is one of the first-line chemotherapy drugs in the treatment of many human cancers. Allyl isothiocyanate occurs abundantly in many cruciferous vegetables such as mustard and horseradish and inhibits cancer cell proliferation through inducing G2/M arrest and apoptosis. The present study was designed to determine the combined effects of cisplatin and allyl isothiocyanate cancer cell growth and death. Three cancer cell lines were studied, including a highly invasive human ovarian cancer cell line, the HCT116 colon cancer cell line and the MCF-7 breast cancer cell line. It was found that combining allyl isothiocyanate with cisplatin significantly increased cancer cell death and decreased cell viability in all three human cancer cell lines compared with each substance used alone. The combination significantly increased caspase-3 activation and reduced the expression of antiapoptotic protein Bcl-2. More interestingly, the combination appeared to neutralize the increase in the antiapoptotic protein survivin expression resulting from treatment with either substance alone. Note that both Bcl-2 and survivin are involved in cancer cell survival and chemotherapy drug resistance. In addition, the combination of allyl isothiocyanate and cisplatin was found to alter cell cycle distribution. The authors conclude that combining allyl isothiocyanate and cisplatin significantly increases cancer cell death as compared with using each compound alone, thus potentially providing a new strategy for cancer treatment.

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.

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.