In addition, the close association observed here between increased VEGFA and COL1A2, COL3A1 and COL1A1 expression in GBM, might also contribute to explain the effect of VEGFA on inducing collagenase expression and remodeling the tumor microenvironment in malignant astrocytomas (i.e. GBM). This evidence concerns the gene COL1A1 and astrocytoma (excluding glioblastoma).