KLF2 and neoplasm: ECs in tumor peripheral tissue have a quiescence phenotype (cluster 1, Pe1), characterized by high expression of BBB enriched genes including SLC2A1 and KLF2. KLF2, a key transcription factor orchestrating a network of genes that promotes EC quiescence in response to flow (29), is one of the top 10 enriched genes in brain EC cluster.