Epigenetic modifiers describing different SCLC subtypes. Key SCLC studies described in the text help to define the SCLC subtypes specific epigenetically regulated genes (as aligned on the circumference of each subtype). The proposed SCLC nomenclature was followed by Rudin et al., [41]. ASCL1, achaete-scute homologue 1; NE, neuroendocrine; NeuroD1, neurogenic differentiation factor 1; POU2F3, POU class 2 homeobox 3; YAP1, yes-associated protein 1.