Among the top 500 upregulated genes in tumor tissues, we selected CTHRC1, neural EGFL like 2 (NELL2), DLG associated protein 5 (DLGAP5), DEP domain containing 1 (DEPDC1), Zic family member 2 (ZIC2) and centrosomal protein 55 (CEP55) for this study (Additional file 3: Figure S1); these genes were also significantly upregulated in an independent gene expression profiling dataset [15]. Here, NELL2 is linked to neoplasm.