Second, multiple SCLC molecular subtypes arise from aneuroendocrine cells of origin, and resistance after chemotherapy causes MYC to activate Notch signaling to dedifferentiate neuroendocrine SCLC in a conserved trajectory from ASCL1+ to NEUROD1+ to the YAP1+ nonneuroendocrine subtype (Ireland et al. 2020). This evidence concerns the gene ASCL1 and small cell lung carcinoma.