(A) Summary of IHC results. γH2AX and Chk2 pT68 were quantified as described in Experimental Procedures. 53BP1 staining was scored as follow: weak (+), moderate (++) and strong (+++). n/a = not applicable (absence of pseudopalisades necrosis). (B) Plot of the % of total γH2AX and Chk2 pT68 positive cells. (C-H) Micrographs of pseudopalisading necrosis of GBMs stained with H&E, anti-HIF1α, anti Ki-67, anti-γH2AX, anti-Chk2 pT68 and anti-53bp1, respectively (see also Figure S3). Inlet in (E) shows nuclear accumulation of HIF1α in cells of the pseudopalisades rim. Scale bars, 100 µm. (I) Plot of the % of positive cells in tumor bulk and pseudopalisades for γH2AX (top panel) and for Chk2 pT68 (bottom panel).** p< 0.01 and * p< 0.05 (see text for more details).