Cancer is a devastating diagnosis since treatments to prevent a lethal outcome are limited. Tumor constitutes a complex tissue consisting of malignant cells and the tumor stroma that can be considered as the tumor-induced supportive tissue. Emerging studies have shown the importance of tumor stroma in tumor growth, invasion, and metastasis highlighting its potential as an attractive target for cancer therapy. While studying spinal cord injury-induced scarring, a new subpopulation of perivascular cells, named type A pericytes, has been discovered to be a major source of stromal scar tissue. Type A pericytes are embedded in the vascular wall but proliferate and leave blood vessels upon injury, differentiating into fibroblast-like cells that deposit extracellular matrix and form the stromal scar. Here, I propose to determine whether type A pericytes are a source of tumor stroma and whether blocking type A pericyte-derived stroma formation can influence cancer progression. I will also analyze pericyte heterogeneity to characterize stroma-forming pericytes compared to other pericyte subpopulations including tumor cell-derived pericytes and investigate the signaling mechanisms mediating their recruitment. By studying stroma formation in the glioblastoma mouse model, the proposed research intends to uncover common mechanisms of tumor stroma formation and identify new targets for therapy.