In human small cell lung cancer RB1 loss nearly always occurs in combination with genetic alterations in other known oncogenes and tumor suppressor genes, particularly TP53. Rb1 and Trp53 deletion in the mouse lung causes development of tumors highly reminiscent of human small cell lung cancer with relatively long latency (Meuwissen et al., 2003). This evidence concerns the gene RB1 and small cell lung carcinoma.