RGS-5 expression correlates with the degree of vascular remodeling in hypoxia-responsive and nonresponsive astrocytomas. (A) WT-AST (original magnification × 10; insert, original magnification × 25) and (B) HIFko-AST (original magnification × 10) were probed with a RGS-5–specific antisense riboprobe to demonstrate differential RGS-5 expression in the tumor vasculature. (C) Tumor samples from untreated 26-week-old RIP1-Tag5 mice with a hemorrhagic “red” appearance and enlarged tumor vessels were stained with anti-CD31 (red) and antidesmin (green) antibodies and the merge is shown (original magnification × 16). (D) Littermates were irradiated with 1000 rad, followed by bone marrow reconstitution and 3 adoptive transfers. At 26 weeks of age, “white” tumors were isolated, which display capillary-like vessels with no signs of hemorrhaging. Costaining for CD31 (red) and desmin (green) is shown (original magnification × 16). Differential expression of RGS-5, assessed by in situ hybridization, is shown for untreated tumors (E) and for regressing tumors after therapy (F). Original magnifications × 16 (E-F). (G) Histologic analyses were complemented by quantitative RT-PCR. Expression levels were normalized to HPRT.