Some genes downregulated by both TTF1 and ASCL1 siRNAs were expressed in neuronal system, for example, LRRN4, SYTL3, TACR1, and TESC, suggesting that both TTF‐1 and ASCL1 were involved in the maintenance of neuroendocrine features in SCLC cells. Here, TTF1 is linked to small cell lung carcinoma.