SMARCA4 and leukemia: Given the high level of specificity of the association between SMARCA4 and the topoisomerase inhibitor class and prior knowledge of the relationship between SMARCA4 and topoisomerase II described above, we experimentally validated the association between SMARCA4 and the topoisomerase II inhibitors (etoposide and mitoxantrone) by overexpressing SMARCA4. The U937 leukemia cell line expressed high levels of SMARCA4 protein, while the KG1 leukemia cell line expressed very low levels of the protein, as analyzed by western blot (Fig. 7e, Supplementary Fig. 6) and flow cytometry (Fig. 7g).