ASCL1 and small cell lung carcinoma: By inhibiting the Notch signaling pathway, INSM1 also plays a key role in NE differentiation, and thus its expression levels are low in non-NE SCLCs.43, 44, 45 NEUROD1, ASCL1, and INSM1 low-expressing or non-expressing SCLCs are classified either into SCLC-Y (YAP1) or SCLC-P (POU2F3) subtype, depending on their TF expression pattern.33