FEN1 and acute lymphoblastic leukemia: Further supporting DNA damage induction as a critical mechanism of action of CD2066 in T-ALL cells, the treatment promoted the gene expression of different regulators of the DNA-repair machinery, including IER5, BAP1 and PCNA in KOPT-K1, IER5, FEN1 and PCNA in DND41 cells and IER5 and RNF8 in TALL1 cells (Figure 10d).