ASCL1 and small cell lung carcinoma: However, investigators have recognized four major distinct subcategories of SCLC using unbiased RNA-sequencing: SCLC-A (it is characterized by transcription factors expressions such as high ASCL1, high DLL3, and protein Schlafen 11 expression), SCLC-P (it is characterized by transcription factors expressions such as high POU2F3 expression), SCLC-N (it is characterized by transcription factors expressions such as high expression of NEUROD1, high expression of somatostatin receptor 2), and SCLC-Y (it is characterized by YAP1 expression) (Sayed and Blais, 2021).