We selected ten G2/M DNA damage checkpoint- and cell cycle-related regulators: Cdc25, Plk1, Cdc20, Cdc20P, APC/CT:Cdh1, ATM/ATR, Mad2:Cdc20P, p53, Cyclin B, and APC/CP:Cdc20 for which parameter variations produce different values of logarithmic intensities in p53-wt and p53-null cancer cells (Fig. 6) under condition of Plk1 depletion that activates DNA damage checkpoint. The gene discussed is ATM; the disease is cancer.