Given the facts that DNA-PKcs is a DNA damage sensing protein in responding to environmental genotoxic or oxidative stresses in cells and overexpression of DNA-PKcs frequently occurs in human cancers, long-term exposure of cells to genotoxins or oxidative stress, e.g. TCDD which produces oxidative stress in cells [48], may lead to constitutive overexpression of DNA-PKcs as the consequence of persistently stressing reactions. Here, PRKDC is linked to cancer.