KDR and Flt-1 were expressed in the tumor vasculature, with particularly high levels seen in coiled young proliferating vessels, especially those in the cyst wall.
The VEGF receptors, kinase domain region (KDR) and Fms-like-tyrosine kinase (Flt-1), also were upregulated in the tumor vasculature of glioblastoma multiforme, anaplastic oligodendrogliomas, and ependymomas with necrosis, whereas the astrocytomas grade II, anaplastic astrocytomas, and oligodendroglioma tumors tended to express a weak to nondetectable signal.
Flt-1, a receptor for vascular endothelial growth factor, is known to display dysregulated expression in both tumor vasculature and tumor cells per se, suggesting that the flt-1 promoter might be a useful candidate to achieve tumor-specific transgene expression.