ASCL1 and small cell lung carcinoma: Recent work proposed SCLC molecular subtypes (SCLC-A, SCLC-N, SCLC-P, and SCLC-Y) based on the differential expression of the key transcriptional regulators ASCL1, NEUROD1 (neurogenic differentiation factor 1), POU2F3 (POU class 2 homeobox 3), and YAP1 (yes-associated protein 1) (Fig. 2).