IDO1 and central nervous system cancer: Thus, while adding 1MT to TMZ treatment was completely ineffectual at enhancing survival in mice with glioblastoma (Additional file 1: Figure S3A), adding 1MT to TMZ selectively upregulated VCAM-1 on endothelial cells in vessels within the tumor, and this vascular activation was not found elsewhere in the brain.Because IDO-blockade had only provided synergistic prolongation of survival when it was combined with both chemotherapy and radiation, we next tested whether adding 1MT to TMZ + RT treatment altered the histological features of the glioma.