Furthermore, ELF3 knockdown in HCC1937 and SUM149PT cells, both of which are human breast cancer cell lines with BRCA1 mutations and allelic loss, also caused a significant decline in cell proliferation (Figure 4C and D, Figure 4—figure supplement 1B and C), suggesting that ELF3 is essential for BRCA1 mutant breast cancer cell survival. Here, BRCA1 is linked to breast cancer.