ASCL1 and small cell lung carcinoma: As it has been widely accepted that SCLC derived from pulmonary NE cells in the lung expresses ASCL1, we included 54 normal neuroendocrine (normal NE) cells described by Vieira Braga, F.A., et al.32 As expected, normal-NE cells were located at the start of the SCLC-A branch, and an evolutionary trajectory from SCLC-A to other subtypes was indicated (Fig. 4c, e, Supplementary Fig. S4e).