Genotypic characteristics of resistant tumors to pre-operative ionizing radiation in rectal cancer

Figure 8 Schematic representation of molecular events following the cellular response to ionizing radiation-induced damage. Ionizing radiation causes an up-regulation of p53. p53 then directly activates the cyclin dependent kinase inhibitor p21. Cell cycle progression stops until the cell repairs the damaged induced by ionizing radiation. If the cell is unable to repair itself, it undergoes apoptosis. Bcl-2 inhibits p53 up-regulation, while p53 inhibits the inhibitor of apoptosis: survivin.