MMP14 and glioblastoma: An ~2 kb MMP14 promoter fragment demonstrated specific activity in brain metastases-infiltrating myeloid cells as compared with the myeloid cells isolated from other tissues, and resulted in a specific delivery of therapeutic molecules to brain metastases.17 We here confirmed that MMP14 is also expressed in hematopoietic cells infiltrating syngeneic GBM (figure 3A), providing a rationale for using MMP14 promoter fragment to drive the expression of therapeutic genes in GBM models.