COL4A1 and glioblastoma: To explore the difference of these two pairs of factors, we first sorted out the 100 most frequently altered neighboring genes (co-expression in both GBM and LGG samples) for COL4A1-2 and COL4A3-4 by calculating the expression level (RNA Seq V2 RSEM) in the cBioPortal online database (GBM and LGG cohorts in TCGA, Firehose Legacy), and constructed the associated gene interaction networks for COL4A1-COL4A2 and COL4A3-COL4A4 (200 genes in each group).