Rb1 was chosen for further studies based on the following two criteria: (1) Rb1 was predicted to be a target gene of miR-155 (Fig. 3a) and plays a critical role in cellular proliferation [23, 24]; and (2) Rb1 protein levels were negatively correlated with miR-155 levels in lung cancer tissues (Fig. 3b). This evidence concerns the gene RB1 and lung cancer.