Indole-3-carbinol inhibits the expression of cyclin-dependent kinase-6 and induces a G1 cell cycle arrest of human breast cancer cells independent of estrogen receptor signaling

Carolyn M. Cover, S. Jean Hsieh, Susan H. Tran, Gunnell Hallden, Gloria S. Kim, Leonard F. Bjeldanes, Gary L. Firestone

Research output: Contribution to journalArticle

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Abstract

Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables such as cabbage, broccoli, and Brussels sprouts, has been shown to reduce the incidence of spontaneous and carcinogen-induced mammary tumors. Treatment of cultured human MCF7 breast cancer cells with I3C reversibly suppresses the incorporation of [3H]thymidine without affecting cell viability or estrogen receptor (ER) responsiveness. Flow cytometry of propidium iodide-stained cells revealed that I3C induces a G1 cell cycle arrest. Concurrent with the I3C-induced growth inhibition, Northern blot and Western blot analyses demonstrated that I3C selectively abolished the expression of cyclin-dependent kinase 6 (CDK6) in a dose- and time-dependent manner. Furthermore, I3C inhibited the endogenous retinoblastoma protein phosphorylation and CDK6 phosphorylation of retinoblastoma in vitro to the same extent. After the MCF7 cells reached their maximal growth arrest, the levels of the p21 and p27 CDK inhibitors increased by 50%. The antiestrogen tamoxifen also suppressed MCF7 cell DNA synthesis but had no effect on CDK6 expression, while a combination of I3C and tamoxifen inhibited MCF7 cell growth more stringently than either agent alone. The I3C-mediated cell cycle arrest and repression of CDK6 production were also observed in estrogen receptor-deficient MDA-MB-231 human breast cancer cells, which demonstrates that this indole can suppress the growth of mammary tumor cells independent of estrogen receptor signaling. Thus, our observations have uncovered a previously undefined antiproliferative pathway for I3C that implicates CDK6 as a target for cell cycle control in human breast cancer cells. Moreover, our results establish for the first time that CDK6 gene expression can be inhibited in response to an extracellular antiproliferative signal.

Original languageEnglish (US)
Pages (from-to)3838-3847
Number of pages10
JournalJournal of Biological Chemistry
Volume273
Issue number7
DOIs
StatePublished - Feb 13 1998
Externally publishedYes

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Cyclin-Dependent Kinase 6
G1 Phase Cell Cycle Checkpoints
Estrogen Receptors
Cells
Breast Neoplasms
Brassica
MCF-7 Cells
Phosphorylation
Tamoxifen
Growth
Cell Cycle Checkpoints
Tumors
Cyclin-Dependent Kinase Inhibitor p27
indole-3-carbinol
Retinoblastoma Protein
Estrogen Receptor Modulators
Flow cytometry
Retinoblastoma
Propidium
Vegetables

ASJC Scopus subject areas

  • Biochemistry

Cite this

Indole-3-carbinol inhibits the expression of cyclin-dependent kinase-6 and induces a G1 cell cycle arrest of human breast cancer cells independent of estrogen receptor signaling. / Cover, Carolyn M.; Hsieh, S. Jean; Tran, Susan H.; Hallden, Gunnell; Kim, Gloria S.; Bjeldanes, Leonard F.; Firestone, Gary L.

In: Journal of Biological Chemistry, Vol. 273, No. 7, 13.02.1998, p. 3838-3847.

Research output: Contribution to journalArticle

Cover, Carolyn M. ; Hsieh, S. Jean ; Tran, Susan H. ; Hallden, Gunnell ; Kim, Gloria S. ; Bjeldanes, Leonard F. ; Firestone, Gary L. / Indole-3-carbinol inhibits the expression of cyclin-dependent kinase-6 and induces a G1 cell cycle arrest of human breast cancer cells independent of estrogen receptor signaling. In: Journal of Biological Chemistry. 1998 ; Vol. 273, No. 7. pp. 3838-3847.
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abstract = "Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables such as cabbage, broccoli, and Brussels sprouts, has been shown to reduce the incidence of spontaneous and carcinogen-induced mammary tumors. Treatment of cultured human MCF7 breast cancer cells with I3C reversibly suppresses the incorporation of [3H]thymidine without affecting cell viability or estrogen receptor (ER) responsiveness. Flow cytometry of propidium iodide-stained cells revealed that I3C induces a G1 cell cycle arrest. Concurrent with the I3C-induced growth inhibition, Northern blot and Western blot analyses demonstrated that I3C selectively abolished the expression of cyclin-dependent kinase 6 (CDK6) in a dose- and time-dependent manner. Furthermore, I3C inhibited the endogenous retinoblastoma protein phosphorylation and CDK6 phosphorylation of retinoblastoma in vitro to the same extent. After the MCF7 cells reached their maximal growth arrest, the levels of the p21 and p27 CDK inhibitors increased by 50{\%}. The antiestrogen tamoxifen also suppressed MCF7 cell DNA synthesis but had no effect on CDK6 expression, while a combination of I3C and tamoxifen inhibited MCF7 cell growth more stringently than either agent alone. The I3C-mediated cell cycle arrest and repression of CDK6 production were also observed in estrogen receptor-deficient MDA-MB-231 human breast cancer cells, which demonstrates that this indole can suppress the growth of mammary tumor cells independent of estrogen receptor signaling. Thus, our observations have uncovered a previously undefined antiproliferative pathway for I3C that implicates CDK6 as a target for cell cycle control in human breast cancer cells. Moreover, our results establish for the first time that CDK6 gene expression can be inhibited in response to an extracellular antiproliferative signal.",
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AU - Tran, Susan H.

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AU - Kim, Gloria S.

AU - Bjeldanes, Leonard F.

AU - Firestone, Gary L.

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