PTEN and brain neoplasm: MiRNA‐21 is strongly overexpressed in the malignant human brain and can boost cell proliferation through inhibiting programmed cell death protein 4 (PDCD 4) and phosphatase tensin homolog (PTEN) or by targeting several signaling pathways that induce cell apoptosis.[11, 12] High‐throughput screening studies have reported that miRNA‐21 plays a vital role in stimulating angiogenesis by targeting angiogenesis‐related genes.[9] Therefore, we studied the effect of antisense miRNA‐21 oligonucleotide (ATMO‐21) on the growth of blood vessels in the brain tumor microenvironment.