ASCL1 and small cell lung carcinoma: While ATOH1 can be co-expressed with NEUROD1 (Figure 1A), we confirmed and extended principal-component analysis (PCA) of transcriptomic data from 39 CDXs (including SCLC-A CDX31P18) that separated ATOH1 models from NEUROD1-only models and from models expressing ASCL1 or POU2F3 (Figure 1B).