PARP1 and breast cancer: Apart from ovarian cancer, a latest phase II study (NCT02032823) has demonstrated that PARP inhibition is also an effective treatment for patients with metastatic breast cancer with gPALB2 (ORR, 82%) and sBRCA1/2 (ORR, 50%) mutations, significantly expanding the population of breast cancer patients who may benefit from PARPi, indicating that not only gBRCA1/2 mutation carriers, but also other mutations in homologous recombination-related genes may benefit from PARPi (Tung et al., 2020).