U2OS cells (American Type Culture Collection, ATCC) were maintained in McCoy’s 5A medium supplemented with 10% fetal bovine serum. MCF-10A cells (ATCC) were cultured in mammary epithelial growth medium containing insulin, hydrocortisone, epidermal growth factor, and bovine pituitary extract (Clonetics). EVSAT cells (Creative Bioarray, NY, USA) were cultured in MEM containing 10% fetal bovine serum. MDA-MB-436 cells (ATCC) were maintained in DMEM medium supplemented with 10% fetal bovine serum. PC3, DU145, ACHN, 786-0, H226, H522, OVCAR-3, OVCAR-8, and MCF7 cells were all obtained from ATCC and maintained according to ATCC instructions. BRCA1 (D-9) monoclonal and TTK polyclonal antibodies were purchased from Santa Cruz (SC-6954, 1:1000) and Cell Signaling (#3255, 1:1000), respectively. ZNF668 antibodies were generated as previously described41 (link). Uncropped scans of the most important western blots are listed as supplementary figures in Supplementary Figure 13. PI3K inhibitor LY-294002 and mTOR inhibitor rapamycin were purchased from Sigma. PARP inhibitors olaparib and rucaparib, HDAC inhibitor vorinostat and Hsp90 inhibitor AUY922 were from Selleckchem. TTK inhibitor AZ3146 was purchased from R&D Systems.