Figure 5.

Immunohistochemistry of lung cancers shows an intact radiation-induced G1 cell-cycle arrest in lung cancers from LSL-Kras; Ink4a/ARF^FL/FL mice, but not from LSL-Kras; p53^FL/FL mice. Immunohistochemistry of sections of lung from mice with lung cancer with the indicated genotype was performed for: (A) Bromodeoxyuridine (BrdU). (B) Phospho-Histone H3. (C) Cleaved-Caspase 3. Top Panels show representative immunohistochemistry for lung tumors in LSL-Kras; Ink4a/ARF^FL/FL and LSL-Kras; p53^FL/FL mice 4 h after radiation treatment with 11.6 Gy (200×, brown-antibody immunostaining, blue – hematoxylin). Inserts show positive control staining for each antibody within unirradiated (BrdU or phospho-histone H3) and irradiated (cleaved-caspase 3) thymus. Bottom panels show quantification of immunohistochemical staining which was performed by counting the number of positively stained cells/random 400× powered field within the lung tumor parenchyma. All analysis was done in a blinded fashion to treatment group and genotype. Error bars – SEM.