MDM2 and lung cancer: However, the limitations of this retrospective work should be recognized: (a) in the original paper, the researchers assumed that the MDM2 rs2279744 polymorphism increases the risk of lung cancer among nonsmokers but not among smokers [3], without considering the false interaction due to the confounding caused by the stronger effect of tobacco smoking; and (b) the original study was not able to control for this confounding variable and uncover the real effect of the MDM2 rs2279744 polymorphism at the level of the overall population.