COL4A1 and glioma: By visual inspection of the hierarchical clustering results, we identified two small subsets of the glial tumors that showed distinct patterns of the 103 TGFβ-responsive classifiers (Figure 3): one with higher expression of many molecules that were induced by TGFβ in vitro and were known as classical TGFβ downstream targets, including SERPINE1, FN1, THBS1, COL6A1, COL4A1, COL1A2, LTBP2, ITGB5 (Figure 3, highlighted in green, see Additional file 2 for the order of 103 probe sets), therefore represented strong TGFβ transcriptional response (right, 11 tumors).