ASCL1 and small cell lung carcinoma: In addition to the work being conducted to explore targeted therapies in SCLC, there is extensive work being performed to further characterize these tumors based on the relative expression levels of key transcription factors, namely achaete-scute homolog 1 (ASCL1), neurogenic differentiation factor 1 (NEUROD1), yes-associated protein 1 (YAP1), and POU class 2 homeobox 3 (POU2F3) [74].