gms | German Medical Science

Neural progenitor cells (NPC) have been used to track solid brain tumors in vivo as well as to express a therapeutic molecule intratumorally. In addition to their antitumoral properties, a restorative potential of these NPC is hoped for. We have investigated the use of local expression of the angiogenic inhibitor endostatin in a model of hematogenous cerebral melanoma metastases using neural progenitor cells as therapeutic vehicles. Concomitantly, we have investigated the effects of endostatin and of additional angiogenesis inhibitors (angiostatin, Su5416, Su5614, and Cox2-inhibitor) on in vivo migration and differentiation. In a second step, the therapeutic potential of Endostatin-transfected NPCs was investigated.

Migration of NPCs was tested with a modified Boyden-chamber assay and a modified wounding assay. Endostatin levels were measured by ELISA. Proliferation and differentiation pattern were analyzed by immunohistochemistry using antibodies against GFAP, NeuN, Huc, MBP, GalC, nestin, vimentin, and Ki67. The primary NPC from GFP-transgene mice as well as the myc-immortalized C17.2 NPC line were exposed to murine recombinant endostatin and angiostatin, and the tyrosine kinase inhibitors Su5416 and Su5614. In a cerebral metastasis model using murine melanoma cells either injected into the internal carotid artery of mice or placed stereotactically into the frontal lobe, concomitant injection of NPCs with/without transgenic endostatin secretion. Survival was recorded and the brains were subjected to immunohistochemical analysis.

Endostatin and Su5614 led to a significant reduction in migration, whereas angiostatin and Su5416 did not alter migration. Phenotypic and proliferative changes compared to control cells were not observed. Endostatin-transfection of NPCs did not result in prolonged survival, although endogenous endostatin expression by tumor cells demonstrated survival advantage. Upon inspection of tumors, a reduced migration of NPCs into metastases were noted if compared to non-endostatin transfected NPCs.

Endostatin inhibited NPC migration. This observation concurs with the in vivo findings of reduced NPC homing towards the tumor and, therefore, abolishing the therapeutic properties of NPCs.