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Sulforaphane (SFN), a prominent isothiocyanate present in cruciferous vegetables, is believed to be responsible along with other isothiocyanates for the cancer preventive activity of such vegetables. SFN arrests mitosis, possibly by affecting spindle microtubule function. A critical property of microtubules is their rapid and time-sensitive growth and shortening dynamics (dynamic instability), and suppression of dynamics by antimitotic anticancer drugs (e.g. taxanes and the vinca alkaloids) is central to the anticancer mechanisms of such drugs. We found that at concentrations that inhibited proliferation and mitosis of MCF7-green fluorescent protein-alpha-tubulin breast tumor cells by approximately 50% (~15 microM), SFN significantly modified microtubule organization in arrested spindles without modulating the spindle microtubule mass, in a manner similar to that of much more powerful antimitotic drugs. By using quantitative fluorescence video microscopy, we determined that at its mitotic concentration required to inhibit mitosis by 50%, SFN suppressed the dynamic instability of the interphase microtubules in these cells, strongly reducing the rate and extent of growth and shortening and decreasing microtubule turnover, without affecting the polymer mass. SFN suppressed the dynamics of purified microtubules in a similar fashion at concentrations well below those required to depolymerize microtubules, indicating that the suppression of dynamic instability by SFN in cells is due to a direct effect on the microtubules. The results indicate that SFN arrests proliferation and mitosis by stabilizing microtubules in a manner weaker than but similar to more powerful clinically used antimitotic anticancer drugs and strongly support the hypothesis that inhibition of mitosis by microtubule stabilization is important for SFN's chemopreventive activity.

Sulforaphane (SUL), an isothiocyanate derived from hydrolysis of glucoraphanin in broccoli and other cruciferous vegetables, was shown to induce phase II detoxification enzymes, inhibit chemically induced mammary tumors in rodents, and more recently, to induce cell cycle arrest and apoptosis in colon cancer cells. In the present study, we demonstrate that SUL also acts to inhibit proliferation of MCF-7 adenocarcinoma cells from the human breast. Treatment of synchronized MCF-7 cells with 15 micromol/L SUL resulted in significant (P < 0.05) G(2)/M cell cycle arrest (167% of control) and elevated cyclin B1 protein (175% of control) within 24 h. Moreover, 15 micromol/L SUL significantly (P < 0.05) induced phosphorylation of histone H1 (167% of control), blocked cells in early mitosis ( approximately 10-fold increase over control), and disrupted polymerization of mitotic microtubules in vivo. Subsequent exposure of purified bovine brain tubulin to relatively high doses of SUL significantly (P < 0.05) inhibited both tubulin polymerization rate (51% of control) and total tubulin polymerization (78% of control) in vitro. Additionally, polymerization of purified tubulin exposed to isothiocyanate-containing analogs of SUL was similarly inhibited. Taken together, these findings indicate that SUL has mammary cancer suppressive actions involving mitotic cell cycle arrest and suggest a mechanism linked to the disruption of normal tubulin polymerization and/or more subtle effects on microtubule dynamics.

Diagnostic trends in medicine are being directed toward cellular and molecular processes, where treatment regimens are more amenable for cure. Optical imaging is capable of performing cellular and molecular imaging using the short wavelengths and spectroscopic properties of light. Diffuse optical tomography is an optical imaging technique that has been pursued as an alternative to X-ray mammography. While this technique permits non-invasive optical imaging of the whole breast, to date it is incapable of resolving features at the cellular level. Optical coherence tomography (OCT) is an emerging high-resolution biomedical imaging technology that for larger and undifferentiated cells can perform cellular-level imaging at the expense of imaging depth. OCT performs optical ranging in tissue and is analogous to ultrasound except reflections of near-infrared light are detected rather than sound. In this paper, an overview of the OCT technology is provided, followed by images demonstrating the feasibility of using OCT to image cellular features indicative of breast cancer. OCT images of a well-established carcinogen-induced rat mammary tumor model were acquired. Images from this common experimental model show strong correlation with corresponding histopathology. These results illustrate the potential of OCT for a wide range of basic research studies and for intra-operative image-guidance to identify foci of tumor cells within surgical margins during the surgical treatment of breast cancer.

The effects of the soybean isoflavone genistein and a commercially-available isoflavone-containing soy extract on the growth of F3II mouse mammary adenocarcinoma cells were investigated. Female Balb/c mice injected (s.c.) with F3II cells and fed diets supplemented with 0.6% soy extract (containing genistein at 750 ppm) exhibited a significant 90% reduction in tumor weight compared to controls, whereas female mice fed diets supplemented with 750 ppm genistein alone exhibited a significant 40% reduction in tumor weight compared to controls. Tumor samples from animals fed the 0.6% soy extract, but not from those animals fed the 750 ppm genistein diet alone, exhibited significantly higher protein levels of the cyclin-dependent kinase inhibitor p21(waf1/cip1) compared to controls. Neither of the two experimental diets altered tumor estrogen receptor-alpha or progesterone receptor protein levels. In vitro, genistein significantly inhibited F3II cell proliferation (IC(50) approximately 2-3 microM) and caused a G2/M block in cell cycle progression at concentrations as low as 5 microM. This genistein-induced G2/M arrest in vitro was associated with a significant increase in the protein expression of phosphorylated p34(cdc2) and of cyclin B1. These results indicate that genistein is an inhibitor of F3II mouse mammary adenocarcinoma cell growth in vivo and in vitro, in part due to its effect on specific cell cycle regulatory proteins. In addition, genistein fed to mice as part of the soy extract resulted in a greater magnitude of inhibition of mouse mammary adenocarcinoma tumor growth, compared to tumor growth of animals fed an equivalent amount of genistein alone. This suggests that genistein along with other constituent(s) in the soy extract may also contribute to suppression of F3II tumor growth.

The association of alcohol consumption with increased risk for breast cancer has been a consistent finding in a majority of epidemiologic studies during the past 2 decades. Herein, we summarize information on this association from human and animal investigations, with particular reference to epidemiologic data published since 1995. increased estrogen and androgen levels in women consuming alcohol appear to be important mechanisms underlying the association. Other plausible mechanisms include enhanced mammary gland susceptibility to carcinogenesis, increased mammary carcinogen dna damage, and greater metastatic potential of breast cancer cells, processes for which the magnitude likely depends on the amount of alcohol consumed. Susceptibility to the breast cancer-enhancing effect of alcohol may also be affected by other dietary factors (such as low folate intake), lifestyle habits (such as use of hormone replacement therapy), or biological characteristics (such as tumor hormone receptor status). Additional progress in understanding alcohol's enhancing effect on breast cancer will depend on a better understanding of the interactions between alcohol and other risk factors and on additional insights into the multiple biological mechanisms involved.

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chair was Dipak K. Sarkar. The presentations were (1) Dual role of estrogen as hormone and carcinogen in mammary carcinogenesis, by Joachim G. Liehr; (2) Alcohol and breast cancer: Studies using animals, by Keith W. Singletary; and (3) Evaluation of the role of estrogen in mediation of ethanol effect on prolactinoma: Studies using animals, by Dipak K. Sarkar.

There is substantial epidemiological evidence suggesting that alcohol consumption is associated with increased risk for breast cancer. However, possible biological mechanisms have not been clearly established. In the present studies, a direct effect of ethanol on the proliferation and intracellular content of cyclic AMP (cAMP) in two estrogen receptor-positive (ER+) and two estrogen receptor-negative (ER-) human breast cancer cell lines was examined. Treatment of ER+ human breast cancer cells (MCF-7 and ZR75.1) with ethanol at concentrations between 10 and 100 mM was associated with increased cell numbers compared to controls. The ERalpha content and the amount of intracellular cAMP also increased in ER+ cells exposed to ethanol, compared to controls. On the other hand, ethanol treatment did not increase cell proliferation or cAMP levels in the ER- (BT-20 and MDA-MB-231) human breast cancer cells. Therefore, ethanol added at physiologically relevant concentrations to ER+ human breast cancer cell cultures can enhance cell proliferation and increase the content of ERalpha.