A–C) H&E stained sections of representative, radiated M-Smo;Baxfloxed tumors at (A) 48 hours after 10 Gy, (B) 5 days after 10 Gy, and (C) after 5 daily doses of 2Gy consistently do not demonstrate tumor regression typical of medulloblastoma with intact Bax. D–I) cC3 and TUNEL staining do not demonstrate widespread apoptosis at the indicated interval after treatment. J,K) IHC for cC3 shows apoptosis in an M-Smo tumor 8 hours after etoposide treatment. Markedly less apoptosis is induced by etoposide in a representative M-Smo;Baxfloxed tumor. Scale bars: 500 µm (A–C and J,K), 50 µm (D–I).