BRCA1 and breast cancer: In agreement with our findings, five out of six breast cancer cell lines bearing BRCA1 mutations showed a strong dependency on TSG101 (Fig 6I and Table EV3), while the sum of breast cancer cell lines was less sensitive to the loss of TSG101 (Fig 6I), indicating that loss of PARylation in the TSG101 knockout might cause synthetic lethality in these cells.