HR and breast cancer: To examine the functional roles of KIFC2 in cells expressing WT or mutant p53, we knocked down endogenous p53 in WT p53–expressing MCF7 cells and then reexpressed Flag-KIFC2 alone or in combination with WT p53 or p53-mutant R175H (the mutation with the highest frequency in patients with HR+/HER2– BC in the TCGA and METABRIC data sets) (Supplemental Figure 6, B and C).