ASCL1 and small cell lung carcinoma: One recent preclinical classification of SCLC is based on the transcription regulators achaete-scute homologue 1 (ASCL1), neurogenic differentiation factor 1 (NEUROD1), POU class 2 homeobox 3 (POU2F3) and yes-associated protein 1 (YAP1) [8].