Zhiyong Ding

ZBP1 antagonizes MRE11-mediated DNA end resection and confers synthetic lethality to PARP inhibition in ovarian cancer

ZBP1, a classic pattern recognition receptor (PRR), has been implicated in regulating programmed cell death and the innate immune response. However, the role of ZBP1 in the nucleus remains largely undefined. Here, we found that nuclear ZBP1 localizes to the site of DNA double-stranded breaks (DSBs) following DNA damage and impairs homologous recombination (HR) repair through its interaction with MRE11. ZBP1 interacts with MRE11 through RHIM A and B domains and inhibits the enzymatic activity of MRE11, ultimately leading to the suppression of HR and DNA damage repair (DDR). These processes are initiated via ATM-mediated ZBP1 phosphorylation at S106. Consistent with these findings, in vitro and in vivo models both exhibit increased sensitivity to PARP inhibitor treatment following ZBP1 overexpression. Furthermore, in our neoadjuvant niraparib monotherapy study (NCT05407841) higher ZBP1 expression correlates with better response to PARP inhibition and prolonged PFS in high-grade serous ovarian cancer (HGSOC). This study describes a novel function of ZBP1 for regulating HR, which confers synthetic lethality to PARP inhibition in ovarian cancer. ZBP1 thus serves as a potential therapy target and biomarker of response to PARP inhibitors and potentially other therapeutic agents such as platin analogs that are synthetically lethal with defective HR.

Mitigating T cell DNA damage during PARP inhibitor treatment enhances antitumor efficacy

Poly(ADP-ribose) polymerase inhibitors (PARPis) are a class of agents targeting DNA damage repair that have become standard therapy for epithelial ovarian cancer (EOC) and multiple other solid tumors. In addition to targeting DNA damage repair, PARPis actively modulate antitumor immune responses, with efficacy being partially dependent on T cell activity. Here, we found that patient T cells sustain DNA damage during PARPi treatment, which reduces treatment efficacy. Leveraging paired pre- and posttreatment tumor samples from a clinical trial of patients with EOC treated with neoadjuvant niraparib as monotherapy, we showed that the PARPi caused DNA damage, slowed proliferation, and increased apoptosis in T cells, which we validated both in vitro and in mouse models. A genome-wide CRISPR (clustered regularly interspaced short palindromic repeats) knockout screen in primary human T cells identified PARP1 as the principal mediator of PARPi-induced T cell death. T cell–specific deletion of PARP1 or mutating Parp1 at its binding sites in transgenic mice led to reduced T cell DNA damage during PARPi treatment, resulting in improved efficacy of PARPis, alone or in combination with immune checkpoint inhibition. We then engineered PARPi-tolerant CAR T cells using cytosine base editing, which decreased PARPi-induced PARP1 trapping and led to reduced PARPi-induced DNA damage, resulting in superior antitumor efficacy in xenograft models compared with parental CAR T cells. This study highlights the relevance of PARPi-induced DNA damage to T cells and suggests opportunities to improve the efficacy of PARPis as monotherapy or in combination with immunotherapy.