We applied the CBE system to introduce the T315I (ACT to ATT) mutation of the BCR::ABL1 fusion gene in a human Philadelphia chromosome-positive leukemia cell line and to introduce the T125M (ACG to ATG) mutation of the TP53 gene in a human B-cell precursor acute lymphoblastic leukemia (BCP-ALL) cell line. The gene discussed is BCR; the disease is leukemia.