The Willner Family Center for Vascular Biology

Hadassa Degani, Director
Fred and Andrea Fallek Professorial Chair in Breast Cancer Research  

The Willner Family Center for Vascular Biology was officially inaugurated on November 3rd, 1999. The Center was designed to focus on the regulation of key biological processes in vascular systems such as blood, and on the identification of signaling molecules, their receptors, their target cells, and the mechanisms involved in the transduction of these signals. Since de-regulation of such processes are a cause for many human diseases (e.g., heart failure, stroke, and cancer), an effort is made to use our results to develop tools for early diagnosis of these ailments, and for the design of new drugs for pharmacological intervention.

Designed by Prof. Shmuel Shaltiel, who was the first Director of the Center, the long-range goals of the Center are: (i) to support innovative ideas, while still in their seeding stage, when it is not yet possible to obtain financial support from conventional funding agencies; (ii) to nurture budding research of young outstanding investigators before their reputation is established; (iii) to finance research that requires an inter-disciplinary effort; (iv) to encourage collaboration with hospitals and with other centers of excellence in Israel and abroad; (v) to train doctoral and post-doctoral students in bioregulation and vascular biology.

The Center supported this year the scientific work of the following groups: Prof. Hadassa Degani ($30,000) - "Angiogenesis in Breast Cancer - from Molecular Biology to diagnostic MRI and MRS": The onset, growth and spread of cancer have been characterized by molecular and cellular methods based mostly on extraction and cell-free analyses. Magnetic Resonance Imaging (MRI) and spectroscopy (MRS) allow to further explore, noninvasively, the anatomic, physiologic and metabolic characteristics of malignancy. We have performed studies aimed to elucidate the mechanisms involved in the regulation of tumor progression, invasion and metastasis. New methodologies and algorithms to map tumor vasculature architecture and perfusion capacity were developed, using tracers (HDO), contrast agents and difffusion MRI. In addition, a method to measure the perfusion and metabolic fate of glucose and its main product, lactate, was refined. These multiple techniques were applied to monitor progression and metastasis of human breast cancer and prostate cancer implanted orthtopically in mice. The results revealed large inter- and intra- tumoral heterogeneity of the vasculature and highlighted the necessity to image cancer at high spatial resolution. We also demonstrated that the vascular volume and flow show poor correlation in tumors, indicating an irregular structure of the capillary walls. Hormonal modulation of tumor progression using antiestrogens altered the vasculature properties, increasing the capillary permeability and affecting flow, presumably by modulating specific vascular growth and permeability factors. This treatment also modulated the metabolic fate of glucose and suppressed the rate of glycolysis. The clinical testing of the method that we have developed for breast cancer diagnosis (termed the 3TP MRI method), which is based on mapping the vasculature permeability and cell density, has been extended to additional medical centers. In the Hospital of Boca Raton, Florida, the protocol was improved to include imaging of both breasts at the same time. Even in the presence of complex breast enhancement, the 3TP method permitted accurate diagnosis of malignant and benign lesions. The 3TP method has been recently adapted for prostate cancer diagnosis and clinical trials have been initiated in Israel.

Prof. Yosef Yarden ($30,000) Cell-to-cell interactions are essential for embryonic development and for a plethora of physiological processes in adulthood (e.g., wound healing).Along with hormones and neurotransmitters, growth factors are the major messengers of intercellular communication in mammals. Many growth factors bind trans-membrane receptors whose cytoplasmic domain initiates signaling by means of an intrinsic tyrosine kinase activity, and oncogenic processes often exploit growth factor signaling for malignant transformation. An example is provided by the ErbB family of receptors for the epidermal growth factor (EGF) and neuregulins: self-production of ligands (autocrine loops), truncated ErbB-1 variants and over-expression of ErbB-2 are frequently associated with virulent tumors, such as carcinomas and glioblastomas. Our past studies concentrated on understanding the layered structure of the ErbB network of signaling and its positive regulators-- a group of adaptors and enzymes. Interestingly, a significant portion of the network is devoted to tuning of signals, a process accomplished by a fine balance between positive and negative signaling pathways. Genetic evidence derived from worms and flies suggests that negative circuits were added to the network relatively late in evolution, and they exhibit unexpected variation and complexity. Concentrating on negative mechanisms, we found that ligand-induced endocytosis and degradation of active receptors is a major regulatory pathway involving not only phopshorylation, but also ubiquitination of receptors and associated molecules. Alongside, constitutive endocytosis and chaperone-mediated stabilization of kinase B9s conformation are essential for network maintenance. In addition, because ErbB proteins are asymmetrically expressed on the surface of neuronal and epithelial cells, multi-molecular complexes regulating post-synthesis sorting are important for signaling. In-depth understanding of network B9s desensitization may facilitate development of new cancer therapies. For example, antibody-induced endocytic removal of ErbB proteins is already in clinical use and drugs interfering with kinase activity or chaperone B9s function are being tested on cancer patients. Identification of still unknown mechanisms that shut down oncogenic signal transduction will eventually expand the arsenal of therapeutic strategies.

Prof. Moti Liscovitch ($20,000) - "Rafts and Caveolae: Platforms for Launching Signaling Cascades and Plasma Membrane Terminals for Drug Transport": Our work is directed towards understanding the cell and molecular biology of phospholipase D and its role(s) in control of cell growth, differentiation and function. We have been studying the cellular and molecular physiology of eukaryotic phospholipase D isozymes, including their localization, mechanisms of activation and possible functions. Currently, we are engaged in identification and cloning of a second yeast phospholipase D gene; we study the differential localization of mammalian phospholipase D isozymes in specific membrane microdomains; we investigate the possible role of phospholipase D2 in caveolae-mediated endocytosis and signaling; and we explore the action(s) and target(s) of phosphatidic acid as a mediator of specific cellular events.

A second, related subject involves the role of caveolin in cancer multidrug resistance. Multidrug resistance severely impairs the efficacy of cancer chemotherapy. Several protein transporters that mediate drug export have been identified, but additional adaptations appear to be necessary for a full-fledged drug resistance. We have recently shown that caveolae and the caveolar coat protein caveolin are dramatically up-regulated in multidrug resistant cancer cells and that the multidrug transporter P-glycoprotein is localized in caveolae-like domains. We are studying the possible involvement of caveolin-dependent mechanisms in mediating drug resistance and the impact of high caveolin expression on the phenotypic transformation of multidrug resistant cancer cells. In addition, studies are underway aimed to elucidate the molecular basis for targeting P-glycoprotein, a multispan integral membrane protein, to caveolae-like domains.

Prof. Michal Neeman ($20,000) - "Magnetic resonance imaging of angiogenesis": Remodeling of blood vessels is an integral and essential component of reproduction, development, wound healing and cancer. The goal of our group is to define the regulation of specific elements involved in the control of angiogenesis and their integration in vivo. For that end we develop non invasive MRI methods for mapping vascular expansion and regression, stabilization of vessels by their maturation, adjustment of vessel permeability and the role of blood vessels and proangiogenic factors in modification of the extracellular matrix and lymphatic function. Using these tools we monitor the kinetics of vascular remodeling in the live animal, during normal development, wound repair and cancer, and study the response to defined molecular, pharmacological or physical intervention aimed to suppress or stimulate angiogenesis. Over the last year our effort included evaluation of the role of neovasculature in dormancy of ovarian carcinoma tumors, analysis of the role of hyaluronan in mediating adhesion and angiogenesis in the normal ovary and ovarian cancer and a study of the acute response to VEGF and the role of VEGF in lymphatic function.