Untersuchungen zu einem tumorrelevanten, FGF-bindenden Protein (FGF-BP)

The nearly ubiquitous growth factors FGF-1 and FGF-2 play next to their physiological functions also a important role in the growth of many neoplastic diseases. Upon secretion though, FGF-1 and FGF-2 are immobilized in the extracellular matrix (ECM) and are thus kept from activation of their high-affinity FGF receptors. A secreted FGF-binding protein (FGF-BP) binds non-covalently and reversible to FGF-1 and FGF-2, releases them from the ECM and makes thus an interaction with their receptors possible. This process of growth factor bioactivation seems to play a pivotal role in the growth of certain neoplastic diseases especially through induction of tumor angiogenesis. This central regulative role of FGF-BP in malignant diseases makes it a promising aim of therapeutic and diagnostic means. In the first part of this thesis the biologic activity of exogenous applied recombinant FGF-BP on tumor and endothelial cell lines was defined more closely. To accomplish this recombinant purified FGF-BP was produced through a baculovirus expression system in insect cells and a suspension culture for this system was established. The paracrine, FGF-2-dependend bioactivity of the recombinant Bv-(FGF-BP) was shown using a softagar assay with SW-13 and DU-145 cells. By adding (FGF-BP) a significant enhancement in growth was induced which was completely blockable by FGF-2 antibodies. The growhts of HUVECs in proliferation assays was also sped up by Bv-(FGF-BP). These results indicate a dual growth-supporting role of FGF-BP in tumors: Direct by stimulation of tumor cells and indirect by induction of angiogenesis. In the second part of this thesis a previously detected pattern of specific FGF-BP-immunoreactive high molecular weight forms, which presumably represent stable covalent complexes of FGF-BP, were examined. After ruling out a possible glycation as a reason for the occurence of these high molecular bands, FGF-BP and FGF-2 were coexpressed in insect cells to gain clues about intracellular complex formation. Despite succesful coexpression a complex formation was not seen under the chosen conditions. In the third part for the first time endogenous expressed FGF-BP was shown through immunhistochemistry in prostate carcinomas. In all 129 samples of 88 patients a positive immunhistochemical reaction was seen. These findings give further insight about the biological effect of FGF-BP, show its FGF-2-mediated, dual growth inducing action on tumors and its expression in prostate cancer. These results emphasize the possible relevance of this protein as a therapeutic target molecule.The nearly ubiquitous growth factors FGF-1 and FGF-2 play next to their physiological functions also a important role in the growth of many neoplastic diseases. Upon secretion though, FGF-1 and FGF-2 are immobilized in the extracellular matrix (ECM) and are thus kept from activation of their high-affinity FGF receptors. A secreted FGF-binding protein (FGF-BP) binds non-covalently and reversible to FGF-1 and FGF-2, releases them from the ECM and makes thus an interaction with their receptors possible. This process of growth factor bioactivation seems to play a pivotal role in the growth of certain neoplastic diseases especially through induction of tumor angiogenesis. This central regulative role of FGF-BP in malignant diseases makes it a promising aim of therapeutic and diagnostic means. In the first part of this thesis the biologic activity of exogenous applied recombinant FGF-BP on tumor and endothelial cell lines was defined more closely. To accomplish this recombinant purified FGF-BP was produced through a baculovirus expression system in insect cells and a suspension culture for this system was established. The paracrine, FGF-2-dependend bioactivity of the recombinant Bv-(FGF-BP) was shown using a softagar assay with SW-13 and DU-145 cells. By adding (FGF-BP) a significant enhancement in growth was induced which was completely blockable by FGF-2 antibodies. The growhts of HUVECs in proliferation assays was also sped up by Bv-(FGF-BP). These results indicate a dual growth-supporting role of FGF-BP in tumors: Direct by stimulation of tumor cells and indirect by induction of angiogenesis. In the second part of this thesis a previously detected pattern of specific FGF-BP-immunoreactive high molecular weight forms, which presumably represent stable covalent complexes of FGF-BP, were examined. After ruling out a possible glycation as a reason for the occurence of these high molecular bands, FGF-BP and FGF-2 were coexpressed in insect cells to gain clues about intracellular complex formation. Despite succesful coexpression a complex formation was not seen under the chosen conditions. In the third part for the first time endogenous expressed FGF-BP was shown through immunhistochemistry in prostate carcinomas. In all 129 samples of 88 patients a positive immunhistochemical reaction was seen. These findings give further insight about the biological effect of FGF-BP, show its FGF-2-mediated, dual growth inducing action on tumors and its expression in prostate cancer. These results emphasize the possible relevance of this protein as a therapeutic target molecule.