The first three groups are characterized by activation of the ASCL1 (SCLC-A), NEUROD1 (SCLC-N), and POU2F3 (SCLC-P) genes, while the SCLC-I subtype is characterized by an inflamed gene signature with high expression of multiple immune genes, including significantly higher levels of genes indicating the presence of CD8-positive cytotoxic T cells (7). Here, ASCL1 is linked to small cell lung carcinoma.