Neoadjuvant PARPi or Chemotherapy in Ovarian Cancer Informs Targeting Effector Treg Cells for Homologous-Recombination-Deficient Tumors [bulk TCR-seq]

Homologous recombination deficiency (HRD) is prevalent in cancer, sensitizing tumor cells to PARP inhibition. However, the impact of HRD and related therapies on the tumor microenvironment (TME) remains elusive. Our study generates single-cell gene expression and T-cell receptor profiles, along with validatory multimodal datasets from > 100 high-grade serous ovarian cancer (HGSOC) samples, primarily from a phase II clinical trial (NCT04507841). Neoadjuvant monotherapy with the PARP inhibitor niraparib achieves impressive 62.5% and 73.6% response rates per RECIST v1.1 and GCIG CA125, respectively. We identify effector regulatory T cells (eTreg) as key responders to HRD and neoadjuvant therapies, co-occurring with other tumor-reactive T cells, particularly terminally exhausted CD8+ T cells (Tex). TME-wide interferon signaling correlates with cancer cells upregulating MHC-II and co-inhibitory ligands, potentially driving Treg and Tex fates. Depleting eTregs in HRD mouse models, with or without PARP inhibition, significantly suppresses tumor growth without observable toxicities, underscoring the potential of eTreg-focused therapeutics for HGSOC and other HRD-related tumors. Batch 1: Bulk TCR-seq of sorted CD4+ T cells from PBMC samples of ovarian cancer patients with paired scTCR-seq data of tumor samples. Batch 2: Bulk TCR-seq of sorted CD3+ T cells from patient-matched PBMC and tumor samples of ovarian cancer patients. Submitter states: Raw sequencing data have been deposited in the Genome Sequence Archive for Human at the National Genomics Data Center (https://ngdc.cncb.ac.cn/gsa-human) with accession number HRA007230, which will be provided for scientific research upon request complying with the law due to human patient privacy concerns.