Angiogenic potential of normal and neurofibromin-deficient human Schwann cells.

摘要

Peripheral nerve sheath tumors from patients with Neurofibromatosis Type 1 (NF1) are highly vascular providing evidence that new blood vessel growth, or angiogenesis, is involved in the growth and progression of these tumors. Schwann cells derived from NF1 tumors are deficient for the protein neurofibromin which results in increased Ras activation. These neurofibromin-deficient Schwann cells have an angiogenesis-promoting phenotype. However, a comprehensive analysis of the angiogenic profile of neurofibromin-deficient human Schwann cells has not been reported and is a focus of this study. We found that conditioned media from neurofibromin-deficient Schwann cells is a stimulus for endothelial cell proliferation and migration. Using gene array and protein array analysis, we found increased expression of several pro-angiogenic factors and decreased expression of several anti-angiogenic factors in neurofibromin-deficient Schwann cells. We studied the angiogenic profile of neurofibromin-deficient Schwann cells derived from both a benign dermal neurofibroma and malignant peripheral nerve sheath tumors and found that the angiogenic expression profile is different for Schwann cells from these two types of tumors. Furthermore, gene expression analysis revealed that several growth factor receptors have increased expression in neurofibromin-deficient Schwann cells, whereas an integrin has decreased expression in neurofibromin-deficient Schwann cells. These results demonstrate that neurofibromin-deficient Schwann cells have dysregulated expression of pro-angiogenic factors, anti-angiogenic factors, growth factor receptors, and an integrin, all of which may contribute to the growth and progression of NF1 peripheral nerve sheath tumors.; Another focus of this dissertation involves the regulation of the angiogenic expression profile in neurofibromin-deficient Schwann cells by restoring the GTPase activating function of the protein neurofibromin. We have reconstituted the NF1-GRD in neurofibromin-deficient Schwann cells using stable retroviral transduction. The NF1-GRD reconstituted neurofibromin-deficient Schwann cells have decreased Ras activation and morphologic changes. However, reconstitution of the NF1-GRD was not sufficient to decrease the angiogenic potential of the cells as measured by the in vitro induction of endothelial cell proliferation and migration. Thus, this study provides evidence that reconstitution of the NFl-GRD alone cannot fully revert the transformation of NF1 tumor-derived Schwann cells and points to the importance of other aberrant genetic or epigenetic changes in these cells.