Home Faculty and Research Faculty by Name Gary Firestone

Gary Firestone

Professor of Cell and Developmental Biology

Lab Homepage: http://socrates.berkeley.edu/~firelab/

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Research Interests

Our overall goal is to characterize the cell signaling pathways that inhibit the uncontrolled growth of epithelial-derived tumor cells, the cell type of most human cancers. Molecular, genetic and cell biological experimental strategies are being utilized to explore the mechanisms by which extracellular signals (such as steroid hormones, growth factors and certain dietary and nondietary phytochemicals) coordinately regulate the proliferation and cell-cell interactions of reproductive tumor cells.

Current Projects

Glucocorticoids have potent anti-proliferative and differentiation effects on steroid-responsive mammary tumor cells by regulating the expression and activity of cell signaling molecules.  One focus of the laboratory is to investigate the steroid-induced cellular cascade that controls cell-cell interactions.  We have discovered that glucocorticoids induce tight junction formation and apical junction organization by a multistep process under conditions in which the cells undergo a stringent growth arrest. The early events include the steroid-stimulated expression of the Id-1 transcriptional regulator, an inhibition of RhoA production and the regulation of cellular factors that interact with several junctional complex components.  Glucocorticoids induce a reorganization of the apical junctional complex that causes a redistribution of the major cytoplasmic and membrane associated tight junction proteins leading to tight junction assembly.  The steroid regulation of membrane organization and tight junction functionality are distinct cellular steps that can be distinguished by their dependence on Ras and RhoA signaling pathways as well as by their targeting by growth factors.  We have established that a key convergence point in this multi-step cascade is beta-catenin, an essential component of the adherens junction, that provides a direct molecular link between steroid hormone signaling and the regulation of cell-cell interactions.  In the absence of steroid treatment, beta-catenin resides primarily in the nucleus and unaccessible to the apical junction complex.  In glucocorticoid treated cells, a stabilized form of beta-catenin is produced in the cytoplasmic compartment that is not phosphorylated and is accessible for localization to the adherens junction at the cell periphery.  We have recently shown that Sgk (a novel serum and glucocorticoid-inducible Ser/Thr protein kinase that is unique in its transcriptional control by several distinct signal transduction pathways, including glucocorticoids, serum, environmental stress, and the p53 tumor suppressor protein) and Akt (a protein kinase that is related to Sgk with similar substrate specificity) trigger the glucocorticoid regulated phosphorylation, ubiquitination and degradation of GSK3 (glycogen synthase kinase-3), which prevents beta-catenin phosphorylation and its subsequent degradation.  We plan to continue to functionally define the steroid regulated components in the glucocorticoid induced cascade that control tight junction formation and adherens junction organization in order to dissect the signaling pathways that mediate cell-cell interactions and to test their potential roles in epithelial cell tumorigenesis.

In a second major area of research, we are investigating, the anti-proliferative effects of phytochemicals in human breast cancer, endometrial cancer and prostate cancer cells. In collaboration with Prof. Bjeldanes' laboratory (Dept. Nutritional Sciences and Toxicology), we are establishing key features of the mechanism by which indole-3-carbinol (I3C), a compound produced in Brassica plants such as broccoli, induces a cell cycle arrest and change the phenotype of human reproductive cancer cells.  In both estrogen responsive and nonresponsive breast cancer cells, the I3C G1 cell cycle arrest involves the selectively inhibition of CDK6 (cyclin dependent kinase-6) gene expression by disrupting the function of the Ets and Sp1 transcription factors at an Ets-Sp1 composite element in the CDK6 promoter.  We have shown that I3C ablates transcription of the estrogen receptor-alpha gene (which is highly associated with proliferation breast cancer cells) while at the same time activating estrogen receptor beta function (which is associated with anti-proliferative pathways in breast cancer cells).  In prostate cancer cells, I3C down-regulated androgen receptor transcription and ablated the androgen dependent induction of prostate specific antigen, a biomarker indicative of prostate cancer.  In human reproductive cancer cell lines producing wild type p53 (a tumor suppressor protein), I3C activates upstream regulators of p53, thereby functionally inducing this tumor suppressor protein.  We have also shown that I3C alters the subcellular distribution and composition of the CDK2 protein complex.  One of our key goals is to identify the I3C target proteins that mediate the indole signaling pathway in human productive cancer cells. We are also attempting to develop more potent synthetic derivatives of I3C and investigate the in vivo tumor effects of I3C to design novel classes of I3C-based anti-breast cancer and anti-prostate cancer agents.  As part of this work, we have collaborated with clinicians to complete the first clinical study in Marin county (CA) of a natural dimer of I3C (called DIM).  The following sites have more information on the use of DIM:  http://www.diindolylmethane.org/
http://www.activamune.com/diindolylmethane_dim_immune_activation_data_center.htm

We have recently been investigating the anti-cancer properties and signaling pathway of other natural compounds such as the natural anti-malaria drug artemisinin which is found in the sweet wormwood plant.  Artemisinin induces a G1 arrest of human breast cancer cells and human prostate cancer cells through a mechanism that is distinct from that of the indole compounds.  In prostate cancer cells, artemisinin strongly down regulates the stability of the androgen receptor, and in breast cancer cells artemisinin down regulates transcription of estrogen receptor-alpha with no effects on estrogen receptor-beta expression.  We are currently focusing on identifying the target proteins and determining the in vivo effects of this natural phytochemical.

Selected Publications

Failor, K.L., Desyatnikov, Y, Finger, L.A. and Firestone, G.L. (2007) Glucocorticoid-induced degradation of GSK3 protein is triggered by Sgk and Akt signaling and controls beta-catenin dynamics and tight junction formation in mammary epithelial tumor cells. Molecular Endocrinology, 21: In Press. 

Sundar, S.N., Kerekatte, V., Equinozio, C.N., Doan, V.B., Bjeldanes, L. F., and Firestone, G.L.  (2006) Indole-3-Carbinol (I3C) selectively uncouples expression and activity of estrogen receptor subtypes in human breast cancer cells.  Molecular Endocrinology, 20: 3070-3082.

Hsu, J.C., Dev, A., Wing, A., Brew, C., Bjeldanes, L.F., and Firestone, G.L. (2006)  Indole-3-carbinol mediated cell cycle arrest of LNCaP human prostate cancer cells requires the induced production of activated p53 tumor suppressor protein.  Biochemical Pharmacology, 72: 1714-1723.

Brew, C.T., Aronchik, I., Hsu, J.C., Sheen, J-H., Dickson, R.B, Bjeldanes, L.F. and Firestone, G.L. (2006) Indole-3-carbinol activates the ATM signaling pathway independent of DNA damage to stabilize p53 and induce G1 arrest of human mammary epithelial cells. Int. J. Cancer, 118: 857-868.

Hsu, J.C., Zhang, J., Dev, A., Wing, A., Bjeldanes, L.F., and Firestone, G.L. (2005) Indole-3-carbinol inhibition of androgen receptor expression and downregulation of androgen responsiveness in human prostate cancer cells.  Carcinogenesis, 26: 1896-1904.

Garcia, H. H., Brar, G. A., Nguyen D.H.H., Bjeldanes, L. F., and Firestone, G. L. (2005) Indole-3-Carbinol (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.  J. Biological Chemistry, 280: 8756-8764.

Rubenstein, N.M., Chan, J. F., Kim, J.Y., Hansen, S.H. and Firestone, G. L. (2005) Rnd3/RhoE induces Tight Junction Formation in Mammary Epithelial Tumor Cells.  Experimental Cell Research, 305: 74-82.

Dalessandri, K. D., Firestone, G. L., Fitch, M.D., Bradlow, L., and Bjeldanes, L.F. (2004) Pilot study:  Effect of 3,3'-diindolylmethane supplements on urinary hormone metabolites in Postmenopausal women with a history of early-stage breast cancer.  Nutrition and Cancer, 50: 161-167.

Guan, Y., Rubenstein, N.M., Failor, K.L., Woo, P.L., and Firestone, G. L. (2004) Glucocorticoids control β-catenin protein expression and localization through distinct pathways that can be uncoupled by disruption of signaling events required for tight junction formation in rat mammary epithelial tumor cells. Molecular Endocrinol., 18: 214-227. 

Firestone G. L. and Bjeldanes, L. F. (2003) Indole-3-Carbinol (I3C) and 3-3'-Diindolylmethane (DIM) Anti-Proliferative Signaling Pathways Control Cell Cycle Gene Transcription in Human Breast Cancer Cells by Regulating Promoter-Sp1 Transcription Factor Interactions.  J. Nutrition. 133: 2448S-2455S.  

Maiyar, A.C., Leong, M.L.L, and Firestone, G. L. (2003) Importin-alpha mediates the regulated nuclear targeting of Serum and Glucocorticoid inducible protein kinase (Sgk) by recognition of a nuclear localization signal in the kinase central domain.  Molecular Biology of the Cell, 14: 1221-1229.

Last Updated 2007-08-15