Prominent angiopathologic events associated with ischemia and hypertrophy, including tumorigenesis, are accompanied by secretion of growth factors from transformed cells which induce localized proliferation of normal tissue. Growth responses associated with endothelial structural integrity quantitatively reflects metastatic potential of tumors and the importance of angiogenesis. The direct stimulation of endothelial cell proliferation is the presumed responsibility of the heparin-binding growth factor (HBGF) family of polypeptides. HBGF-1, both a potent mitogen for mesoderm-derived cells in vitro and a hormonal inducer of angiogenesis in vivo, does not contain a recognizable signal peptide for secretion. The biological significance of this feature is related to HBGF-1 signal transduction processes: (a) interaction with a high affinity receptor, and (b) nuclear localization following receptor-mediated internalization. Localization within the nucleus anticipates that HBGF-1 may induce and sustain gene expression events that define the transformation potential of this growth factor. Deletion of the nuclear translocation sequence has generated a mutated form of HBGF-1 that is capable of receptor binding but unable to signal DNA synthesis or cell division, thereby suggesting natural antiangiogenic behavior. We hypothesize that HBGF-1 mediates its transforming potential through an extracellular pathway, which can be inhibited in vivo by receptor-competent, mitogenically inactive mutant forms of this growth factor. To rigorously define the biological properties of these polypeptides, the gene for different structural forms of HBGF-1 will be transduced into cells associated with vascular structure using retrovirally-mediated techniques. The interrelationship between the signal peptide and nuclear translocation sequence and their responding biological cascades will be evaluated to define molecular indicators of angiogenic responses during experimental tumorigenesis. Furthermore, the molecular mechanisms underlying the association between angiogenesis and perpetuation of proliferative lesions will be characterized in the complex environment of the living organism. Transplantation of transduced cells into a well-defined fiber implant model will be used to experimentally perturb and modulate a localized, site-specific biological process, thereby serving as a window to angiopathic phenomena and mechanisms to inhibit these processes. The availability of well-defined antibody and nucleic acid probes permits the dissection of responding genetic events at the molecular level using in situ analysis of mRNA and protein expression by transduced cell in vitro and in vivo. While the precise involvement of cytokines, growth factors and other gene products are not known, the cumulative resources, reagents and techniques within this application will elucidate detailed characteristics reflective of pathological angiogenesis and provide a rational design for therapeutic intervention.
Showing the most recent 10 out of 51 publications
