The transcriptomic analysis of both these cell lines and SCLC tumors has enabled the categorization of SCLC into four molecular subtypes, determined by the expression of a range of transcription factors that specify cell lineage: ASCL1, NEUROD1 (Neuronal Differentiation 1), POU2F3 (POU Class 2 Homeobox 3), or YAP1 (Yes1 Associated Transcriptional Regulator). Here, NEUROD1 is linked to small cell lung carcinoma.