ASCL1 and small cell lung carcinoma: They identified 4 molecular subtypes called SCLC-A, SCLC-N, SCLC-Y and SCLC-P, according to the expression of transcription factors required for neuroendocrine (ASCL1 or NEUROD1) or non-neuroendocrine (YAP1 or POU2F3) differentiation.