ASCL1 and small cell lung carcinoma: DLL3, encoding a Notch pathway regulator and a promising clinical target in SCLC treatment, is upregulated in ASCL1-high SCLC tumors; in contrast, DLL3 expression is diminished in RB wild-type tumors and in SCLC tumors not expressing neuroendocrine markers [2, 3, 39].