MMP9 and glioma: Finally, we found that MMP9 and MUC4, as well as EGFR and MUC4, co-localized in the microvasculature (Fig. 4), suggesting EGFR and MUC4, both expressed on the cell surface, could interact with, and trigger MMP9 expression. Given that this study supports the combined potential of MUC4 and MMP9 as biomarkers for diagnosis in glioma tissue, future studies underlying the detailed mechanistic underpinnings using in vitro assays and preclinical animal models is warranted.