Pathogenesis
CBCRP's priority issue of Pathogenesis focuses on basic science and exploratory research into the initial development and progression of breast cancer. We have divided this priority issue into five sub-topics, which define major areas of scientific inquiry. The spread of breast cancer in the body continues to be the biggest problem in diagnosis and effective therapy, and there is slow progress towards new strategies. Fortunately, major advances are being made in understanding the process of angiogenesis (development of the tumor's blood supply), and prospects of attacking breast cancer at this level for both primary and metastatic tumors look very promising. For the topic of cell growth, in 1998 there was the first clinical introduction of an effective therapy against the Her-2 growth factor receptor to combat breast cancer. Her-2 continues to be a prime research interest. Associated with cell growth is the topic of intracellular signaling pathways that cause breast cancer cells to multiply, accumulate genetic mutations, and survive when attacked by the immune system or current therapies. The CBCRP has funded important research on apoptosis, which is programmed cell death. Next, we are accumulating more information at the genetic level to discover how specific genes and their protein products serve to differentiate a breast cancer cell from a normal cell. At present, we have an incomplete understanding of these genetic differences. A related topic to cancer genes is the area of gene regulation, which involves the proteins and chromosomal regions where gene activity is controlled. One direction of this research effort is to devise ways to shut down cancer-causing genes within cells. Finally, more information is emerging on the topic of tumor progression, which are the events causing normal and pre-malignant cells to transform into full-fledged cancer cells. Several CBCRP—funded projects examine the microenvironment of normal and breast cancer cells. Both through human aging and from factors produced by altered cells, these environmental interactions become defective and this creates a permissive opportunity for breast cancer. By understanding the causes of tumor progression, we will be able to influence these factors in normal breast cells to develop ways of preventing the disease.
Conclusions
Outbreak — how cancer spreads: angiogenesis, invasion, and metastasis
Jeffrey Smith, Ph.D., at The Burnham Institute, finished a 3-year Research Project on Prevention of Breast Cancer by Blocking Integrin Function. Breast cancer cells are able to move in the body because of certain cell surface receptors that serve to attach them to the extracellular matrix. In this project, breast cancer cells were mutated to delete a critical adhesion receptor (avb3). In all respects, except metastasis and adhesion, the cells appeared to be normal. This receptor is an excellent target for therapeutic intervention, since inhibitory drugs are far along in development for diseases other than breast cancer. Dr. Smith has expanded this work to examine the proteins inside of breast cancer and other cells that regulate the binding function of these integrin adhesion receptors.
Andre Lochter, Ph.D., at the Lawrence Berkeley National Laboratory, was funded in a 2-year Postdoctoral Fellowship to study the Cell Microenvironment and Progression of Breast Cancer. He examined the process of “epigenetic programming” of breast cancer cells caused by factors outside the cell, a protein meshwork called the ‘extracellular matrix.’ An enzyme secreted by breast cancer cells, stromelysin-1, causes degradation of a key cell surface receptor that leads to both cellular and environmental changes associated with the invasive potential of the cells. This invasive behavior was inhibited through blockage of certain ‘integrin’ receptors on breast cancer cells. These observations are key to understanding changes in cell behavior that are independent of DNA mutations in breast cancer. If these microenvironmental perturbations could be reversed, then the early events of certain breast cancers could be prevented.
Too much cell growth: defective messages and internal signaling
Daniel Donoghue, Ph.D., at the University of California, San Diego, investigated Mechanisms of Aberrant Cell Growth during a 3-year Research Project. He examined the part of the protein sequence of the oncogene, Her-2, that crosses the cell membrane. This region is critical for relaying the growth signals from outside the cell, primarily by allowing Her-2 to self-associate as homodimers. Dr. Donoghue was able to determine the locations of the critical amino acids in the transmem-brane domain that permit receptor dimeriza-tion, and he also determined that Her-2 association alone is not sufficient for growth promoting activity. Apparently, the internal portion of Her-2, the kinase domain, requires a specific type of ‘rotational coupling’ to function properly. These studies increase our understanding of growth regulation in breast cancer.
John Reed, M.D., Ph.D., at The Burnham Institute, completed a Research Project aimed at understanding Immune Responses to Breast Cancers: Function of TRAF Protein. The aim was to uncover ways to make tumor cells more vulnerable to immune attack. This study identified a group of tumor proteins called IAPs that bind to apoptosis proteins and prevent immune-mediated tumor destruction. Additionally, Dr. Reed found that breast cancers sometimes alter their levels of proteins called TRAFs, which are involved in making the cells more sensitive to the signals given by the immune cells. Improper levels of IAPs and TRAFs are at least partially the reason why some breast cancer cells are able to escape killing by the immune system.
Jamil Momand, Ph.D., at the Beckman Research Institute of the City of Hope, finished a 3-year New Investigator project to study the Loss of p53 Tumor Suppressor Function in Breast Cancer. In this project the relationship between the cellular location of p53 and proteins that p53 interacts with were examined. The tumor suppressor p53 is mutated in some breast cancers and in other cancers it fails to respond to either DNA/ cellular damaging chemicals or radiation even when it is not mutated. Dr. Momand first determined that a natural inhibitor of p53, called MDM2, did not appear to function in blocking p53 in certain breast cancer cell lines. It was found that ionizing radiation would cause p53 protein to increase without causing its accumulation in the nucleus of cells. Thus, some functions of p53 appear to be retained under conditions of nuclear exclusion. These results indicate that p53 works in a more complex way in breast cancer than previously believed, and that the cellular location and functionality of its partner proteins will require more study.
Zheng-gang Liu, Ph.D., at the University of California, San Diego, finished a Postdoctoral Fellowship to answer the question—Why Does Normal Cell Death Not Occur in Breast Cancer? It is known that breast cancer cells do not respond normally to signals that cause normal cells to die—a process called apoptosis. Dr. Liu examined how normal and breast cancer cells respond to the cyto-toxic protein, tumor necrosis factor (TNF). The key findings were that c-Jun kinase signaling inside cells is not involved in TNF-induced apoptosis, while in breast cancer cells the activation of the transcription/signaling factor NF-kB will allow the cells to avoid cell death. This information gives tremendous insight into potential ways to restore the normal apoptosis function in breast cancer, which could both block their natural resistance to TNF and make existing chemotherapy work more effectively.
Mistakes on the master blueprint: molecular genetics and gene regulation
Helene Baribault, Ph.D., of The Burnham Institute, was funded for a 2-year Research Project to study The Role of Bax Gene in Breast Cancer Pathogenesis. A mouse model system was developed, such that specific genes could be deleted or ‘knocked-out’ specifically in the mammary gland. This approach is called the Cre-loxP technology, and Dr. Baribault showed that her gene expression (Cre) was restricted to the mammary gland, and all the technical hurdles needed to validate this revolutionary method were developed. Thus, genes that are either known or suspected to be important for mammary cell development, differentiation in pregnancy, and development of breast cancer can be studied in a manner restricted to the mammary gland using this powerful ‘knockout’ method. This project is being continued to study the apoptosis (cell death) regulator, Bax. In addition, Dr. Baribault and her postdoctoral fellow were funded in 1998 to apply her Cre-LoxP technology to additional breast cancer genes of interest.
Elizabeth Blackburn, Ph.D., of the University of California, San Francisco, completed an IDEA grant to examine ways of Altering Telomerase to Prevent Breast Cancer Progression. Telomerase is an enzyme that is responsible for maintaining the integrity of chromosomes, thereby allowing the cells to become immortal. Normal cells lack telomerase and can only divide a limited number of times. However, in cancer cells, telomerase expression is one mechanism for a cell to gain unlimited potential for division. This grant explored two strategies for taking advantage of telomerase activity to kill tumor cells by a) using compounds such as AZT to stop telomerase activity, or b) designing compounds that cells with active telomerase would turn into poisons. Dr. Blackburn was able to show that these approaches show promise in test tubes and lower organisms. The long-term goal is to find out whether these approaches are effective in women.
Utha Hellmann-Blumberg, Ph.D., of the University of California, Davis, has completed a Postdoctoral Fellowship for Studies Of Tamoxifen/Toremifene DNA Interactions in Monkeys. Drugs that interfere with estrogen-stimulated tumor growth have shown great promise for treating and preventing the growth of breast tumors. Physicians already use them for treating breast cancer and are likely to expand their use to reduce breast cancer risk, so it is especially important to identify any toxic effects these drugs might have. These drugs could produce metabolites that bind to DNA and cause uterine tumors. Dr. Hellmann-Blumberg found evidence of DNA binding when tamoxifen metabolites were examined in the test tube, but this was less for toremifene (an alternative to tamoxifen) metabolites. This correlated with the observation that toremifene is less likely to cause uterine tumors in humans than tamoxifen. The animal studies examining DNA damage by these antiestrogens were not conclusive, probably because they required longer exposure to the drugs. These studies indicate that tamoxifen, and possibly toremifene, can cause DNA damage during long-term treatment (chemoprevention), but toremifene may to be safer.
John Reed, M.D., Ph.D., from The Burnham Institute, was funded to investigate Bax Gene Expression in Breast Cancer. In this project some of the critical relationships between a cell death (apoptosis) regulatory protein, Bax, and two other proteins, bcl-2 and p53 were established. It was found that Bax was not a good independent prognostic marker for breast cancer. However, the amount of Bax did appear to be increased following chemotherapy. This demonstrates that apoptosis pathways inside breast cancer cells can become initiated, and future research must resolve why these processes are not effective in limiting cell growth.
Dieter Wolf, M.D., at Stanford University, completed one year of a Postdoctoral Fellowship to study the Control of DNA Replication in Breast Cancer. This project focused on the role of a cell cycle protein, called Cdc6, which activates DNA replication. Defects in DNA replication play a significant role in increased growth potential and for the incorporation of genetic mutations and rearrangements characteristic of breast cancer. Dr. Wolf prepared antibodies to Cdc6, cloned a human gene (hPOP) that regulates Cdc6 stability, and determined the pathway of Cdc6 degradation within human cells. This work has great potential to address the molecular issues associated with changes in ploidy (i.e., abnormal chromosomal duplications).
Searching the unknown: novel breast cancer genes
John Groffen, Ph.D., at the Children's Hospital, Los Angeles, completed a 3-year Research Project to investigate Two Candidate Breast Cancer Genes on Chromosome 17. The development of breast cancer is associated with severe alteration in chromosome structure and numbers. Dr. Groffen's initial work was performed on the genes called Crk and Abl. He expanded the study to include another gene called Rac3, which was cloned and analyzed for chromosomal location. For Crk and Abl there was no clear correlation in cell expression, chromosome deletion, and breast cancer samples. Interestingly, Rac3 is still expressed in breast cancer despite the apparent absence of a normal chromosome 17 location. This work is being continued with a focus on signaling proteins/genes, such as Rac3, and their relationship to breast cancer.
David Schott, Ph.D., from the California Pacific Medical Research Center, completed a Research Project to identify A Candidate Breast Tumor Suppressor Gene on Chromosome 13. This gene called Brush-1, is involved in breast cancer development and is lacking in breast cancer cells. When Brush-1 was placed back into breast cancer cells grown in culture, they appeared and behaved like normal cells. Dr. Schott was also able to identify the portion of the Brush-1 gene that was responsible for this activity. The next step was to test whether the presence or absence of Brush-1 affected breast cancer growth in organisms. He found that breast cancer cells with Brush-1 were somewhat less capable of forming tumors, but once tumors did form, they were just as aggressive as tumors without Brush-1.
Claudia Lin, Ph.D., at the Lawrence Berkeley National Laboratory, completed a 2-year Postdoctoral Fellowship for the Targeted Search for New Transcription Factors in Breast Cells. In this project the nuclear factors in cells that regulate genes for mammary growth and differentiation were studied. Using a technique of yeast 2-hybrid screening, Dr. Lin found a potential transcription factor, ITF-2, and detailed the relationship between the amounts of this protein and mammary growth and differentiation. Since normal breast cell functions are lost in breast cancer, this information could be used to limit the disease by activating normal cell growth limiting and cell death pathways.
Michael Lewis, Ph.D., at the University of California, Santa Cruz, was funded for a 2-year Postdoctoral Fellowship to answer the question: Homeobox Genes: A New Class of Human Breast Oncogenes? These genes from fruit flies have counterparts in humans that act to regulate cellular differentiation and body organization. Dr. Lewis' initial work pointed to a family of genes called IRX, which could represent undiscovered examples of either tumor suppressors or oncogenes. His studies that disrupt IRX genes in cells led to cellular changes that resemble neoplastic transformation. This work is being continued to examine expression and amounts of these homeobox genes in breast cancer samples.
Manuel Perucho, Ph.D., from The Burnham Institute, completed a 1-year IDEA project aimed at Identifying Novel Breast Cancer Tumor Suppressor Genes. He performed pilot studies using peptide sequences displayed on bacteriophage to demonstrate the feasibility of detecting caspase-3 (an apoptotic enzyme) and the retinoblastoma tumor suppressor. The eventual goal is to introduce phage into cells to block unknown endogenous tumor suppressors in order to identify them. Tumor suppressors are poorly understood, since their loss in many experiments does not lead to carcinogenesis as directly as the presence of oncogenes. This project is a first step in developing the technology to identify novel tumor suppressors.
Janis Jackson, M.D., at the Scripps Research Institute, was funded through a 1-year IDEA for the Analysis of Rac Mutations in Breast Cancer. This gene is a key player for intracellular signaling that leads to changes in gene expression, growth, and adhesion properties when defects occur. Using a PCR approach Dr. Jackson was able to confirm that a large percentage (17 out of 37) of ductal breast carcinoma samples had detectable mutations in a specific codon of the rac1 gene. These signaling genes and their mutations in breast cancer are becoming the key links between growth factor receptors (such as Her-2), changes in gene expression, and the lack of a cellular response to the accumulation of genetic mutations.
Unraveling the path to breast cancer: tumor progression
Satyabrata Nandi, Ph.D., at the University of California, Berkeley, completed a 3-year Research Project to develop a Model of Human Breast Cancer Development and Progression. His group was able to grow human breast cancer samples in a mouse model and maintain their unique hormonal and growth factor receptor status through several generations of mice. This is called a ‘surrogate human breast’ model. These animals then become experimental platforms for the study of gene transfer and therapy, drug studies, and hormonal modification. Such issues as pregnancy, contraceptive use, and hormonal replacement therapy can studied in this mouse model. This system has better relevance to human cancer, compared to the more commonly used laboratory breast cancer cell lines.
Steven Frisch, Ph.D., from The Burnham Institute, investigated Reprogramming Breast Cancer Epithelial Cells. In this 1-year IDEA project he examined the mechanism by which the adenovirus E1a gene could revert cancer cells to normal cells. E1a is a nuclear gene regulatory protein. Dr. Frisch identified the critical regions of a partner protein, called p300/CBP, that appears to mediate the E1a effects. The eventual goal is to better understand and use this system to overcome the ‘silencing’ of normal adhesive functions present in epithelial cells, but lost in cancer cells. The ability to ‘activate’ these latent functions would serve to limit the invasiveness of breast cancer and restore normal functions.
Robert Ochs, Ph.D., at The Scripps Research Institute, was funded through a 1-year IDEA award to investigate Autoantibodies in Breast Cancer. He found that about 50% of breast cancer patients appear to develop autoantibodies, which are directed at breast cancer proteins. This observation was consistent in the three samples of patients analyzed. However, at present there appears no definite relationship between the presence of autoanti-bodies and various clinical parameters associated with diagnosis and disease progression. Dr. Ochs plans to continue this work by a more detailed analysis of the specific proteins recognized by the autoantibodies. Continued efforts to understand the immune response to breast cancer and make it more effective in combating the disease remains a major interest of CBCRP.
Valerie Weaver, Ph.D., at the Lawrence Berkeley National Laboratory, finished a Postdoctoral Fellowship to study Vitamin D and Breast Cancer Prevention: Cell Death vs. Growth. The focus of this study was the relationship between breast cancer cells and their immediate microenvironment, called the extracellular matrix. This association becomes perturbed in cancer, and understanding how this can be restored could reverse the early stages of breast cancer. Vitamin D treatment serves to arrest the growth of breast cancer cells and enhance their attachment to the extracellular matrix. Interestingly, treatment of cancer cells with antibodies to the b 1 -integrin adhesion receptors caused them to revert to a more normal phenotype. Maintaining the connection between breast epithelial cells and the extracellular matrix appears to be critical to limiting both their growth potential and the ability of cells to accumulate mutations that eventually lead to cancer.
Research in Progress
Outbreak — how cancer spreads
In order to become life threatening, a breast tumor has to acquire the ability to invade the tissues surrounding it. Pierre-Yves Desprez, Ph.D., of the California Pacific Medical Research Institute, has two CBCRP-funded projects to study the enzymes, called metalloproteinases (MMPs), which cause invasiveness. First, he has confirmed that a protein found in some tumor cells, Id-1, correlates with cellular invasiveness. This observation holds in cell lines and in humans. Secondly, he has discovered novel pro-teinases that could be utilized for both diagnosis and treatment. Enzymes present outside of the cell can be critical in determining a tumor's degree of invasiveness, in terms of not only their presence or absence, but also the form they take. Alex Strongin, Ph.D., of the La Jolla Institute for Experimental Medicine, has shown that MMP2 controls tumor migration, invasion and metastatic potential when it is in a form that is bound to the outside of the tumor cells. Finally, David Rose, D.V.M., Ph.D., at the Scripps Research Institute, has found that intracellular signaling proteins can modulate the affinity of a cell surface integrin receptor, and these results are being extended to breast cancer.
Too much cell growth: defective messages and internal signaling
Breast cancer cells must pass critical checkpoints in order to divide, and the proteins that regulate this process (called cyclins) are potential targets for breast cancer therapy. Kevin Sato, Ph.D. at the Scripps Research Institute has reported success in being able to block the activity of the DNA replication cyclin E by using of an ‘antisense’ technique. This caused the delay of DNA synthesis, but did not entirely block cell division. Still, cyclin E is elevated in breast cancer, and this technique is a novel approach for selective inhibition. Juan Zapata, Ph.D., at The Burnham Institute, finds that a Tumor Necrosis Factor signaling protein, called TRAF-4, is reduced in breast cancer, and this loss is permissive for continued growth. This work is being extended to the study of an inhibitor of TRAF-4, called I-TRAF, which will be studied in an animal model.
The pathogenesis of a tumor can provide clues regarding why treatments are effective, or ineffective. With the recent interest in anti-estrogen therapy as a risk reducing agent in addition to a therapeutic one, it is especially important to learn about the underlying mechanisms for its action. Ruth Lupu, Ph.D., at the Lawrence Berkeley National Laboratory, is concentrating on the function of the newly discovered estrogen receptor, ER-b. She is using antibodies to determine whether ER-b is regulated differently by estrogen and tamoxifen than traditional estrogen receptors. Studying the pathogenesis of tumors can also lead to the discovery of new agents to use in the fight against breast cancer. Michael Stallcup, Ph.D., of the University of Southern California, has been studying peptides, GRIP1, GRIP2 and GRIP3, that mediate the action of estrogen. He determined that although two of these peptides (GRIP 2 and 3) are not found in nature, they provide promising starting points for novel peptides that could inhibit estrogen receptor action.
The epidermal growth factor and members of the epidermal growth factor receptor family play a significant role in breast cancer development, therefore it is important to understand how the receptors are regulated. Gordon Gill, M.D., of the University of California, San Diego, finds specific proteins (SNX1, but not SNX2) that guide EGF receptors to the part of the cell where they are destroyed. Dr. Gill has identified the function of distinct regions of SNX, for example the SNX of a specific receptor. Ichiro Maruyama, Ph.D., of the Scripps Research Institute, is examining the structure of the EGF receptor and how it moves in the cell membrane in order to determine how the receptor is turned on. Dr. Maruyama has preliminary evidence that upon binding to EGF the receptor molecules rotate or twist around the axis perpendicular to the plane of the cell membrane and become active. Finally, Wanda Reynolds, Ph.D., of the Sidney Kimmel Cancer Center, is investigating the regulation of Her-2, another receptor in the EGF receptor family. She is specifically looking at areas on the Her-2 gene, called Alu repeats, where hormone receptors can bind and possibly affect their expression. The Alu repeats could also be sites of DNA mutations.
Mistakes on the master blueprint: molecular genetics and gene regulation
It is appreciated that breast cancer cells are genetically different from normal cells. One iimportant aspect of this is due to the expression of different genes. Philippe Pujuguet, Ph.D., at the Lawrence Berkeley National Laboratory, is determining how the immediate microenvironment of breast cancer cells becomes defective and sends the wrong signals inside the cell. He is finding that his-tones, which package DNA into chromatin, are one important level of transcriptional control in breast cells and breast cancer. Robert Oshima, Ph.D., at The Burnham Institute, is studying a mutant form of a protein, called Ets2, which regulates gene expression. David Zarling, Ph.D., at the Pangene Corporation, is developing a novel method for detecting mutant genes in cancer cells using circularized DNA probes. In addition, he is examining a protein called Rad51, which is involved in DNA repair and can interact with the tumor suppressors, p53 and BRCA1. Finally, Mark Chapman, Ph.D., of The Salk Institute for Biological Studies, is trying to determine how BRCA1 functions in cells. One hypothesis is that BRCA1 interacts with other proteins to regulate the production of growth stimulating factors. He has identified several proteins that bind to BRCA1 and BRCA2 and provide clues to how these genes protect normal cells from becoming tumor cells.
Searching the unknown: novel breast cancer genes
Breast cancer appears to always involve genetic differences between adnormal and normal cells. One research goal is to find and catalog these changes. Sergei Malkhoysan, Ph.D., at The Burnham Institute, is using a technique called AP-PCR to identify chromo-somal regions that both unmask tumor-causing genes (oncogenes) and cause the loss of tumor-inhibitory genes (tumor suppressors). In a more defined manner, Terumi Kohwi-Shigematsu, Ph.D., at the Lawrence Berkeley National Laboratory is studying the global ways DNA is organized in breast cancer. There exist specific DNA segments and associated proteins that attach the chromosomes to the supporting matrix in the cell's nucleus. She is focusing on a protein called p114, which is selectively present in breast cancer cells. This protein could modulate gene expression through its function of regulating DNA structure.
Heregulin is a protein that binds to and stimulates the HER-2/neu growth factor receptor. Fabiana Guerra-Vladusic, Ph.D., of the Lawrence Berkeley National Laboratory, is identifying genes that are regulated by heregulin. She caused a cell line that normally does not produce heregulin to make it and found that the cells were growth-inhibited, had lost their capacity to spread in culture, had increased cell size, and showed signs of apoptosis of (cell death). She is now looking for the genes that mediate this effect.
Unraveling the path to breast cancer: tumor progression
Judith Campisi, Ph.D., at the Lawrence Berkeley National Laboratory, is investigating the nature of the critical changes, both genetic and environmental, that allow breast cancers to become established. She is creating breast cells that contain subtle mutations, but still appear normal. The idea is to expose these minimally altered cells to factors known to cause cancer. Her key interest is cell senescence that causes changes in the microenvironment of breast cells, and this could stimulate cancer when cells have already accumulated otherwise ‘silent’ mutations. Anissa Agadir, Ph.D., of The Burnham Institute, is determining which molecular events are responsible for the physiological effect of retinoids, which are derivatives of retinoic acid that inhibit tumor progression. She is also investigating the mechanism of synthetic retinoids such as retinyl methyl ether (RME) in inhibiting tumor growth and progression. She has found that RME-activated retinoid receptors specifically interfere with AP-1 (factors that turn on growth genes) activity in the cell and inhibit cell invasion induced by a tumor promoter.
Recently Initiated Research
Outbreak — how cancer spreads: angiogenesis, invasion, and metastasis
Five new grants were awarded in this topic area. Sonoko Narisawa, Ph.D., at The Burnham Institute, will examine how breast cancer spreads to the bone, the most common site of metastasis. Her plan is to discover new cell receptor proteins for breast cancer cells that are on the endothelial cells in bone, and these methods should directly indicate the active protein regions where metastasis inhibitors might be developed. Pragada Sriramarao, Ph.D., at the La Jolla Institute of Experimental Medicine, will investigate the properties of newly formed tumor blood vessels with respect to binding circulating lymphocytes. These potentially tumor-fighting lymphocytes circulate adjacent to breast tumors, but for unknown reasons they fail to recognize the regions of tumor growth. Earl Sawai, Ph.D., from the University of California, Davis, is funded to study the molecular linkage between uncontrolled breast cancer cell growth and metastasis. A key intracellular protein, phosphotidylinositol 3-kinase, will be studied in a unique animal model. Closely related to metastasis is the process of cell-cell adhesion that links the normal breast epithelial cells together and limits their growth. Karin Zeh, Ph.D. is a Postdoctoral Fellow working with her mentor, Helene Baribault, Ph.D., at The Burnham Institute, to produce transgenic mice to study cell surface adhesion receptor-associated intracellular proteins. They plan to make whole animal mutations in these cytoskeletal proteins, called g-catenin and plakoglobin, to study their role as regulators of mammary development and cancer.
Too much cell growth: defective messages and internal signaling
The CBCRP continues to support innovative and career development grants in this topic. Glenn Rosen, M.D. at Stanford University is funded to investigate the molecular mechanism of action for a compound derived from a traditional Chinese herb, which sensitizes breast cancer cells to apoptosis. Koji Itahana, Ph.D. from the Lawrence Berkeley National Laboratory will be examining mutant p53 (a tumor suppressor protein) for its possible role in promoting breast cancer, beyond the loss of its normal function. Another tumor suppressor protein, retinoblastoma, will be investigated for its interaction with associated proteins using the technique x-ray crystallography by Kathryn Ely, Ph.D. from The Burnham Institute. Finally, Cary Lai, Ph.D. from the Scripps Research Institute will study a possible regulatory binding protein, related to neuregulin, which could activate the Her family of breast cancer growth receptors.
Mistakes on the master blueprint: molecular genetics and gene regulation
Research funded in this topic includes some of the same proteins as described earlier, but the focus is more on gene regulation. Shu-ichi Matsuzawa, Ph.D. from The Burnham Institute will investigate a family of p53 target proteins, called Siah, as downstream mediators of tumor suppressor function and apoptosis. p53 mutations are common in breast cancer, and some of these mutations could serve to disrupt other pathways inside the cell. Heinz Ruffner, Ph.D. at the Salk Institute for Biological Studies is funded to study the modification (phosphorylation) of BRCA1 by looking for specific intracellular kinases.
Searching the unknown: novel breast cancer genes
FumiichiroYamamoto,Ph.D., at The Burnham Institute, will examine a novel set of genes that are believed to be associated with breast cancer development because they have a different number of methyl groups attached when compared to normal genes. Another aspect of chromosomal structure will be investigated by Paul Kaufman, Ph.D., from the Lawrence Berkeley National Laboratory, who will study the association of Chromatin Assembly Factor (CAF)-I with breast cell senescence (aging).
Unraveling the path to breast cancer: tumor progression
Studies of tumor progression are providing an important link between Pathogenesis and another CBCRP priority issue, the Biology of the Normal Breast. Martha Stampfer, Ph.D., at the Lawrence Berkeley National Laboratory, will be using a novel molecular approach to look for genes showing loss-of-function (tumor suppressor genes) and also permissive for cell immortalization. Kunxin Luo, Ph.D., also at the Lawrence Berkeley National Laboratory, plans to study a portion of a normal growth factor in mammary cells that could have a tumor suppressor function. Henrik Ditzel, M.D., Ph.D., at the Scripps Research Institute, is funded to examine a breast cancer protein that stimulates this ‘medullary breast tumor’ T-lymphocyte infiltration, and could serve as the future basis for a vaccine. Finally, G. Shyamala, Ph.D. at Lawrence Berkeley National Laboratory will be investigating the relationship of the progesterone receptor with the activity of matrix metalloproteinases, presence of a matrix protein called laminin, and a cell surface adhesion receptor called E-cadherin.
