Unexpectedly, gene set enrichment analyses (GSEA) revealed that 76 repressed Pax5 target genes, identified in pro‐B cells (Appendix Fig S2A and Dataset EV2), were significantly enriched as upregulated genes in Pax5Jak2/+ B‐ALL tumors (Fig 2D), which is also exemplified by the expression of 5 representative genes in the respective pro‐B and B‐ALL cells (Fig 2E). Here, PAX5 is linked to acute lymphoblastic leukemia.