However, recent observations recognize a role for PARP1 also in the so-called “error-prone alt-EJ or microhomology-mediated end joining” (MMEJ) repair pathway of DNA DSBs, underscoring how HR-deficient ovarian and breast tumors display a compensatory increase in the Polθ/PARP1-mediated alt-EJ pathway that is strictly involved in their survival and proliferation [29,30,31]. Here, PARP1 is linked to breast neoplasm.