For example, investigation of cell cycle and surviving fraction after low dose rate irradiation (0,025 Gy/h) in p53 wt human colon carcinoma cells engineered to express E6 and E7 showed increased levels of p53 and p21 and enhanced cell cycle arrest at G1 and G2 but no difference in clonogenic survival [41]. Here, TP53 is linked to colon carcinoma.