Somatic inactivation of Rb1 and p53 using intratracheal injection or intubation of mice with adenovirus-Cre leads to the development of SCLC-like tumors34, whereas mice carrying germline deletion of one Rb1 allele and both p53 alleles (Rb1 + /−p53 − /−) develop a variety of primary tumors of neuroendocrine origin as well as focal bronchial neuroendocrine cell hyperplasia51, showing the critical importance of these factors in preventing transformation and growth of neuroendocrine cells. This evidence concerns the gene RB1 and small cell lung carcinoma.