Loss of Pten, a gene frequently mutated in human SCLC, accelerated tumor progression as described by two groups: McFadden et al. [51] reported SCLC tumor development when using the neuroendocrine-specific CGRP promoter; meanwhile, Cui et al. [70] observed a mixture of SCLC/LCNEC/ADC when using the CMV promoter. This evidence concerns the gene PTEN and large cell neuroendocrine carcinoma.