INSM1 and small cell lung carcinoma: ASCL1, insulinoma‐associated 1 (INSM1) zinc finger transcription factor, and BRN2 collaborate to form regulatory circuitry involved in neuroendocrine differentiation of SCLC (Borromeo et al., 2016; Fujino et al., 2015; Sakaeda et al., 2013).