POU3F2 and small cell lung carcinoma: ASCL1 and NEUROD1, along with insulinoma-associated protein 1 (INSM1) and POU class 3 homeobox 2 (BRN2), are recognized as important master regulators for NE differentiation in SCLC (Rudin et al., 2019; Fujino et al., 2015; Ishii et al., 2013).