At least one of the four key molecules is expressed in SCLC cells, and Rudin et al. proposed a new model to categorize SCLC subtypes based on the expression of the following molecules: ASCL1 (SCLC-A), NEUROD1 (SCLC-N), YAP1 (SCLC-Y), and POU2F3 (SCLC-P). The gene discussed is ASCL1; the disease is small cell lung carcinoma.