In the classical T-ALL subgroup, two observations stood out in addition to the predominance of Pten hits described above: (1) recurrent insertions in genes linked to late thymocyte development (Tcf12, Rpl5), consistent with the notion of classical T-ALLs arising from post-commitment DP cells, and (2) a large number of CISs affecting intergenic REs, especially among the top CISs (Figures 6J, S16D, and S16F), suggesting a so far unappreciated importance of subtle gene regulation, specifically in classical T-ALL. This evidence concerns the gene TCF12 and acute lymphoblastic leukemia.