To test this hypothesis, they conducted an analysis of the response of different leukemia types displaying a variety of mutations that cause a low level of one of the members of BRCA-HR pathway, which includes: BCR-ABL1-positive chronic myeloid leukemia (CML) cells in which BRCA1 is downregulated [62], PML-RAR-positive acute promyelocytic leukemia (APL) cells with downregulation of RAD51C (RAD51 paralog), and samples from leukemias which express low levels of BRCA1/2 due to unknown mechanisms. This evidence concerns the gene BRCA1 and acute promyelocytic leukemia.