ACE and small cell lung carcinoma: The KEGG pathway analysis showed that genes co-expressing with ACE genes were substantially enriched in 12, 5, 6 and 14 pathways at each time points, respectively (Additional file 1: Tables S5-S8) The intersectional co-expression genes mainly clustered into 7 pathways, including hepatitis C, small cell lung cancer, apoptosis, thyroid hormone signaling pathway, sphingolipid signaling pathway, AMPK signaling pathway, and PI3K-Akt signaling.