TP53 and small cell lung carcinoma: To evaluate the cell of origin of SCLC, inactivation of Rb1 and p53 in different cellular compartments of the lung using cell-specific promoter (CC10-cre, SP-C-cre and CGRP-cre) adenoviral cre administration in Rb1f/f;p53f/f mice was performed [100] (figure 2b).