COL4A3 and carcinoid tumor: We also evaluated the expression data of CREB5, PTPRB and COL4A3 from Oncomine [9], indicating that CREB5, PTPRB and COL4A3 were significantly lower in carcinoid than normal lung tissues (Additional file 1: Figure S1), which was accordant to the results of the DASL and RNA-seq datasets.