RB1 and small cell lung carcinoma: This pattern of early metastases is recapitulated in experimental models of SCLC, including GEMMs, which often feature very few initiating mutations: the RP model has only conditional loss of Rb1 and Trp53, the RPR2 model has additional deletion of Rbl2 (also known as p130), and the RPM model additionally features a hyperactive form of MYC11,13.