NOTCH1 and small cell lung carcinoma: NOTCH1-ICD was present by immunoblotting in 24% (n = 10 of 42) of ASCL1+ SCLC cell lines (Supplemental Figure 12, A and B) and by IHC in a sample of ASCL1+ treatment–naive SCLC patient–derived xenografts with high, but not low, NOTCH1 expression (Figure 9A).