CRISPR screen identifies GATAD1 as a synthetic lethal target with CDK4/6 inhibitors in estrogen receptor-positive breast cancer.

Estrogen receptor-positive (ER+) breast cancer represents approximately two-thirds of all breast cancers and has a sustained risk of late disease recurrence. Combining cyclin-dependent kinase 4/6 (CDK4/6) inhibitors with anti-estrogen therapies significantly improves ER+ advanced breast cancer clinical outcomes. Despite promising clinical outcomes, intrinsic or acquired resistance to CDK4/6 inhibitors has limited their success. We used CRISPR to screen MCF-7 cells to explore the targets whose inhibition is synthetic lethal with CDK4/6 inhibitors in ER+ breast cancer cells. We found that GATA zinc finger domain containing 1 (GATAD1) is a new synthetic lethal target with CDK4/6 inhibitors in ER+ breast cancer cells. Mechanistically, GATAD1 promotes cell proliferation by transcriptionally inhibiting p21 in ER+ breast cancer cells. GATAD1 depletion decreased the phosphorylation of CDK2/4 and RB transcriptional corepressor 1 (RB1), inducing cell cycle arrest. P21 overexpression abolished the enhanced proliferation induced by GATAD1 overexpression. Our results identify GATAD1 as a therapeutic target in ER+ breast cancer, which is beneficial to provide a novel treatment strategy.