Lalage Wakefield, D. Phil

wakefiel@dce41.nci.nih.gov

Tumor Suppressor Group Members


BIOGRAPHY: Dr. Wakefield is a Principal Investigator in the Laboratory of Cell Regulation and Carcinogenesis, CCR, NCI. She obtained her D.Phil. in Biochemistry at Oxford University, UK, for studies on the bioenergetics of the chromaffin granule. In 1983 she joined Michael Sporn's laboratory at the NCI, to work on the biology of transforming growth factor-ßs (TGF-ßs), and she was tenured in 1989. She now heads the "Tumor Suppressor" Group. Dr Wakefield is a member of the NCI Breast Cancer Faculty , the NCI Molecular Targets Faculty, and the national Mouse Models of Human Cancer Consortium. In 2001, she received an "Outstanding Mentor Award" from the NCI.

RESEARCH INTERESTS:

    The objectives of my research group are to analyze the complex roles that TGF-ßs play in tumorigenesis, particularly in the mammary gland/breast. TGF-ßs have both tumor suppressor activities, (eg.inhibition of proliferation, induction of apoptosis, maintenance of genomic stability) and pro-oncogenic activities (eg. suppression of immunesurveillance, enhancement of invasion and migration, promotion of angiogenesis). We are particularly interested in what determines whether the suppressor or oncogenic activities are expressed. Understanding this problem will be critical if the TGF-ß system is to be exploited effectively in novel approaches to the prevention or treatment of breast cancer.
    Our general approach is to experimentally compromise the TGF-ß system in various ways and determine the effect on mammary epithelial homeostasis and tumorigenesis. We have complementary research programs using genetically modified mice and cell culture model systems. My group is also part of a larger multidisciplinary effort to generate and validate improved mouse models of human cancer, through our membership of the nationwide Mouse Models of Human Cancers Consortium. Currently, our research is focussed in three main areas:
1. Generation of mouse models to analyze the roles of the TGF-ß system in tumorigenesis in vivo. Expression of the type II TGF-ß receptor (TßRII) decreases in human breast cancers, while expression of the TGF-ß1 ligand tends to increase in advanced metastatic disease. We are generating mouse models that allow us to independently regulate (i) epithelial responsiveness to TGF-ß and (ii) effective levels of TGF-ß ligand, so that we may determine the functional significance of these changes in vivo . We have modeled the decreased receptor levels seen in human breast cancer by transgenically overexpressing a dominant negative type II TGF-ß receptor (DNR) in the mouse mammary gland, and we showed that these mice are more susceptible to breast cancer when challenged with carcinogens (Ref. 6). This study was the first prospective demonstration of the tumor suppressor function of epithelial TßRII in an intact animal. It showed that endogenous TGF-ß in the mammary gland provides important protection against tumorigenesis, at least in the early stages of the disease process. More recently we have developed the ability to manipulate endogenous TGF-ß ligand levels in vivo, by generating transgenic mice overexpressing a soluble TGF-ß antagonist. These mice show a greatly decreased incidence of metastases, suggesting that pro-oncogenic activities of TGF-ß may dominate in late stage disease (Ref. 1). Furthermore, this TGF-ß antagonist appears to selectively neutralize the prometastatic effect of TGF-ß while sparing its important regulatory effects in normal tissues. These results suggest that soluble protein antagonists of TGF-ß might be useful for long-term clinical use of the prevention of metastasis following diagnosis of a primary tumor. The animal models are being refined and exploited so that we may look at underlying biological and molecular mechanisms.

2. Use of cell culture model systems to analyze the dose- and stage-dependence of the tumor suppressor function of TGF-ßs. We have previously shown that the tumor suppressor effects of TGF-ß are highly dose-dependent (Ref. 5). We are currently testing the hypothesis that the tumor suppressor activities of TGF-ß require a higher level of activation of the TGF-ß response system than do the oncogenic activities. Using human breast-derived cell lines, we are correlating TGF-ß receptor activation status with biological and molecular responses. Approaches include large-scale analysis of gene-expression using cDNA microarrays. If pro-oncogenic activities of TGF-ß are selectively retained at low levels of receptor activation, this could explain why human breast cancers frequently show decreased expression of TGF-ß receptors, but almost never show total genetic inactivation.

    We and others have previously hypothesized that TGF-ß may function primarily as a tumor suppressor in the early stages of tumorigenesis, but as an oncogene in late-stage disease. In collaboration with Dr. Fred Miller and colleagues at the Barbara Karmanos Cancer Institute, we are working with a staged series of human breast-derived cells lines to look at the effect on tumorigenesis of knocking out TGF-ß responsiveness at different stages of tumor development. Genetically modified cells are xenografted into nude mice to test their tumorigenicity. We have previously used this approach successfully in a prostate model system to show that loss of TGF-ß responsiveness causes transformation and tumorigenicity of apparently normal prostatic epithelial cells (Ref. 4), confirming a tumor suppressor role in early stage disease.
 
3. Analysis of signal transduction pathways underlying the tumor suppressor and oncogenic activities of the TGF-ßs. We are exploring the possibility that the tumor suppressor and oncogenic activities of TGF-ßs may use different signal transduction pathways. The signal transduction components Smads1,2,3 and 4 have all been implicated downstream of TGF-ß in breast cancer cell lines. We are using Smad knockout and conditional knockout mice to look at the specific Smad requirements for different TGF-ß functions during mammary gland development and tumorigenesis. Our preliminary work suggests that Smad3 may not be important for tumor suppression in mammary gland (Ref. 2). We hope that an understanding of which signal transduction components are responsible for the tumor suppressor vs. the oncogenic activities of TGF-ß will facilitate the design of new pharmacological agents that can selectively enhance the tumor suppressor activities.

 

Representative Publications:

Research Articles:

  1. Yang, Y. et al. Lifetime exposure to a soluble TGF-ß antagonist protects mice against metastasis without adverse side-effects. J. Clin. Invest. 2002;109:1607-1615
  2. Yang, Y. et al. Smad3 in the mammary epithelium has a non-redundant role in the induction of apopotsis, but not in the regulation of proliferation or differentiation by TGF-ß. Cell Growth & Differentiation, 2002; 13:123-130.
  3. Zujewski, J. et al.: Transforming growth factors-ß are not good biomarkers of chemopreventive efficacy in a preclinical breast cancer model system. Breast Can. Res., 3:66-75, 2001.
  4. Tang B. et al. Loss of responsiveness to transforming growth factor ß induces malignant transformation of non-tumorigenic rat prostate epithelial cells. Cancer Res. 1999; 59: 4834-4842
  5. Tang B et al. Transforming growth factor-ß1 is a new form of tumor suppressor with true haploid insufficiency. Nature Medicine 1998; 4: 802-807
  6. Bottinger EP et al. Transgenic mice overexpressing a dominant-negative mutant type II transforming growth factor-ß receptor show enhanced tumorigenesis in the mammary gland and lung in response to the carcinogen 7,12-dimethylbenz-[a]-anthracene. Cancer Res. 1997; 57: 5564-5570
  7. Bottinger EP et al. Expression of a dominant-negative mutant TGF-ß type II receptor in transgenic mice reveals essential roles for TGF-ß in regulation of growth and differentiation in the exocrine pancreas. EMBO J. 1997; 16: 2621-2633

Reviews:

  1. Wakefield, L.M. et al. TGF-ß signaling: Positive and Negative Effects on Tumorigenesis. Curr. Op. Genet. & Dev., 2002; 12:22-29
  2. Wakefield LM et al. TGF-ß signaling in mammary gland development and tumorigenesis. J. Mammary Gl. Biol. & Neoplasia, 2001; 6:67-82
  3. Wakefield LM et al. Transforming growth factor-ß and breast cancer: lessons learned from genetically altered mouse models. Breast Cancer Res. 2000; 2: 100-106
Last revised on July 1st, 2001, by Sintha Huff

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