Sulforaphane Inhibits Mammary Cancer Cell Mitotic Progression and Tubulin Polymerization
Jackson, Steven Jac Todd
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Permalink
https://hdl.handle.net/2142/83689
Description
Title
Sulforaphane Inhibits Mammary Cancer Cell Mitotic Progression and Tubulin Polymerization
Author(s)
Jackson, Steven Jac Todd
Issue Date
2004
Doctoral Committee Chair(s)
Singletary, Keith W.
Department of Study
Food Science and Human Nutrition
Discipline
Food Science and Human Nutrition
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Oncology
Language
eng
Abstract
Sulforaphane (SUL), an isothiocyanate derived from hydrolysis of glucoraphanin in broccoli and other cruciferous vegetables, has been 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. Here, we provide evidence that SUL also acts as a breast cancer antiproliferative agent. The BALB/c mouse mammary carcinoma cell line F3II was treated with SUL at concentrations up to 15 muM and examined for markers of cell cycle arrest and programmed cell death. Treatment of asynchronous F3II cells with 15 muM SUL resulted in G2/M cell cycle arrest, elevated p34 cdc2 (cdc2) kinase activity, Bcl-2 downregulation, evidence of caspase activation, and aggregation of condensed nuclear chromatin. Subsequent exposure of synchronized cells to 15 muM SUL resulted in elevated numbers of prophase/prometaphase mitotic figures, indicating cell cycle progression beyond G2 and arrest early within mitosis. Moreover, cells treated with 15 muM SUL displayed aberrant mitotic spindles, and higher doses of SUL inhibited tubulin polymerization in vitro. In addition, BALB/c mice injected s.c. with F3II cells and subsequently injected daily i.v. with SUL (15 nmol/day for 13 days) developed significantly smaller tumors (∼60% less in mass) than vehicle-treated controls. Western blot analysis of tumor proteins demonstrated significantly (P < 0.05) reduced PCNA and elevated PARP fragmentation in samples from animals dosed with SUL. We also demonstrate that SUL acts to inhibit proliferation of MCF-7 adenocarcinoma cells from the human breast. Treatment of synchronized MCF-7 cells with 15 muM SUL resulted in significant (P < 0.05) G 2/M cell cycle arrest and elevated cyclin B1 protein within 24 h. Moreover, 15 muM SUL was found to significantly (P < 0.05) induce phosphorylation of histone H1, block cells in early mitosis, and disrupt polymerization of mitotic microtubules in vivo. Taken together, these findings indicate that SUL has mammary cancer suppressive actions involving mitotic cell cycle arrest and suggest a mechanism linked to disruption of normal tubulin polymerization and/or more subtle effects on microtubule dynamics.
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