Novel I3C Regulated Cell Cycle Factor in Breast Cancer Cells

Institution: University of California, Berkeley
Investigator(s): Gary Firestone, Ph.D. -
Award Cycle: 2003 (Cycle IX) Grant #: 9WB-0148 Award: $150,000
Award Type: STEP Award
Research Priorities
Detection, Prognosis and Treatment>Innovative Treatment Modalities: search for a cure



Initial Award Abstract (2003)
A critical problem in treating breast cancer is the lack of effective therapeutics directed against estrogen-independent forms of the disease, which respond less favorably to the anti-estrogens (e.g., tamoxifen). In addition, there has been less research directed at the identification of active ingredients and molecular mechanism of action for dietary components in breast cancer prevention and treatment. Our interest is focused on a compound called indole-3-carbinol (I3C), which is found in Brassica-type vegetables (e.g., cabbage, broccoli, and Brussels sprouts). We have discovered that direct treatment of breast cancer cells with I3C stops cell growth. Secondly, we have found a novel I3C regulated factor that may be the key mediator of the I3C-induced growth inhibitory response. We propose to identify and characterize this protein and evaluate its role in the I3C growth inhibitory pathway with the aim of developing novel therapeutic strategies to control breast cancer using I3C-based compounds.

Nothing is known about the cellular proteins that determine the ability of I3C to arrest the growth of human breast cancer cells independent of the estrogen receptor. Our hypothesis is that the novel I3C regulated factor disrupts the function of key proteins involved in breast cancer cell growth. We further propose that the presence of this I3C regulated factor and its relative abundance will determine how well different types of breast cancer cells respond to I3C in terms of growth inhibition.

We plan to use proteomic and molecular approaches to isolate and identify the I3C regulated factor from human breast cancer cells. A key step in this strategy will be clone the I3C-regulated factor through techniques that exploit its binding to a cell cycle protein that is associate with the I3C-regulatd factor. Using a highly sensitive mass spectrometry technique, only very small quantities of the I3C-regulated factor will be needed to determine its amino acid sequence, and the information then used to clone the gene. Breast cancer cells will be generated that produce either unaltered or amplified forms of the I3C-regulated factors to characterize its cellular functions.

Given the limited information about the role of indole-type compounds produced in vegetables in the treatment of breast cancer, our study will provide the necessary first experimental information needed for a detailed understanding of how the highly potent I3C molecule can stop breast cancer cell growth. An innovative experimental aspect of the project is the identification and characterization of novel a I3C-regulated factor which can potentially be the I3C target. Identification of the I3C target protein will provide new approaches to design more effective I3C-based compounds for chemo-therapeutic strategies. Our collaborative project is unique in that it combines laboratory research on molecular mechanisms of breast tumor biology with drug development and chemical expertise.


Final Report (2005)
A critical problem in treating breast cancer is the lack of effective therapeutics directed against estrogen-independent forms of the disease, which respond less favorably to the anti-estrogens (e.g., tamoxifen). In addition, there has been relatively little research directed at the identification of active ingredients and molecular mechanism of action for dietary components in breast cancer prevention and treatment. We have discovered that direct treatment of estrogen responsive and estrogen independent human breast cancer cells with indole-3-carbinol (I3C), which is found in Brassica-type vegetables (e.g., cabbage, broccoli, and Brussels sprouts), inhibits cell growth by inducing a cell cycle arrest. Secondly, we have found a novel I3C regulated factor that may be one of the key mediators of this I3C-induced growth inhibitory response. We proposed to identify and characterize this protein and evaluate its role in the I3C growth inhibitory pathway with the eventual aim of developing novel therapeutic strategies to control breast cancer using I3C-based compounds.

The novel I3C regulated factor was found to be a larger sized form of cyclin E. Growing breast cancer cells, not treated with I3C, produce smaller forms of cyclin E, which helps control cell growth by forming a protein complex with other cell cycle proteins in the nucleus. We further showed that the larger sized form of cyclin E and its associated protein complex is detected in the cell cytoplasm after I3C treatment, which is a cell compartment that would prevent its function, and thereby inhibit cell growth. This novel observation suggests a new pathway by which natural plant compounds can control the growth of human breast cancer cells.

Given the limited information about the role of indole-type compounds produced in vegetables in the treatment of breast cancer, our study provides the necessary first experimental information needed for a detailed understanding of how the highly potent I3C molecule can stop breast cancer cell growth. Characterization of the function and mechanism by which I3C induces the larger form of Cyclin E will potentially provide new approaches to design more effective I3C-based compounds for chemo-therapeutic strategies.

Indole-3-Carbionl (I3C) Inhibits Cyclin Dependent Kinase-2 Function in Human Breast Cancer Cells by Regulating the Size Distribution, Associated Cyclin E Forms and Subcellular Localization of the CDK2 Protein Complex
Periodical:Journal of Biological Chemistry
Index Medicus: J Biol Chem
Authors: Garcia H.H., Brar G.A., Nguyen D.H.H., Bjeldanes, L.F., and Firestone G.L.
Yr: 2005 Vol: 280 Nbr: Abs: Pg:8756-64