Apoptosis; Cell Cycle Proteins/physiology; DNA-Binding Proteins/physiology; Neoplasms/pathology; Protein Serine-Threonine Kinases/physiology; Proto-Oncogene Proteins c-myc/metabolism; Tumor Suppressor Proteins/physiology; Animals; Ataxia Telangiectasia/metabolism; Ataxia Telangiectasia Mutated Proteins; Blotting, Western; Caspase 3; Caspases/metabolism; Cell Cycle Proteins/metabolism; Cell Line; Cell Line, Tumor; Cells, Cultured; Chromosomal Proteins, Non-Histone/metabolism; Comet Assay; DNA Damage; DNA-Binding Proteins/metabolism; Female; Fibroblasts/metabolism; Genotype; Histones/chemistry; Humans; Immunoblotting; Immunohistochemistry; Keratinocytes/cytology; Keratinocytes/metabolism; Lymphoma/metabolism; Male; Mice; Mice, Knockout; Mice, Transgenic; Microscopy, Fluorescence; Neoplasms/metabolism; Oncogenes; Phosphorylation; Protein Serine-Threonine Kinases/metabolism; Thymus Gland/pathology; Time Factors; Tumor Suppressor Proteins/metabolism