CD200 and acute lymphoblastic leukemia: Many of the genes altered in ALL encode proteins with roles in key cellular pathways, including lymphoid development and differentiation (e.g., PAX5, IKZF1, EBF1, LEF1, and VPREB), cell-cycle regulation and tumor suppression [CDKN2A, CDKN2B (INK4/ARF), TP53, PTEN, and RB1], lymphoid signaling (BTLA, CD200, and TOX), transcription factors and transcriptional coregulators (ERG, TBL1XR1, and CREBBP), regulation of apoptosis (BTG1), and drug receptor (NR3C1) (10).