Similar to the SCLC tumors, low NE cell lines displayed significantly higher expression of APM genes compared to the NE cell lines (p = 0.003) (Supplementary Fig. 15B) and the level of NE differentiation correlated with the ssGSEA APM gene set score (R = −0.45, p < 0.001) (Supplementary Fig. 15C). This evidence concerns the gene ANPEP and small cell lung carcinoma.