Pikkusaari, S. | bioRxiv Science

bioRxiv2025

Proteome profiling reveals HES1-driven mitotic catastrophe in ovarian serous carcinoma

Ovarian high-grade serous cancer (HGSC) is an aggressive subtype of epithelial ovarian cancer. Here, we identify BX-912, a phosphoinositide-dependent kinase 1 (PDPK1) inhibitor, as a promising therapeutic agent for HGSC. BX-912 suppressed HGSC growth as a single agent and synergized with olaparib independently of BRCA status. Unexpectedly, BX-912 treatment induced multinucleation, a phenotype not observed with other PDPK1 inhibitors. Proteome Integral Solubility Alteration (PISA) profiling revealed the transcription factor HES1 as a functional target of BX-912. Structural modeling showed that BX-912 binds the Orange domain of HES1, while its WRPW motif mediates interactions with protein partners, including the AP2 endocytic protein complex, coordinating their nuclear accumulation that leads to a mitotic catastrophe. Furthermore, cell cycle analyses showed that BX-912 combined with olaparib synergistically enhanced DNA damage and G2-M arrest. Our study demonstrates the value of proteomics for revealing hidden drug activities. It also identifies potential inhibition strategies for HES1, which is commonly overexpressed in HGSC. Additionally, this study proposes a novel strategy of targeting consecutive cell cycle phases to enhance treatment efficacy in HGSC.

cancer biology↗

bioRxiv2024

Patient-derived functional immuno-oncology platform identifies responders to ATR inhibitor and immunotherapy combinations in ovarian cancer

Responses to single agent immunotherapies have remained modest in high-grade serous ovarian cancer (HGSC), suggesting the need for combination treatments. Identifying clinically effective immunotherapy combinations (IC) requires pre-clinical testing using models representing the patient-specific immune microenvironment. Here, we established a functional immuno-oncology platform for high-throughput and functional testing of IC using HGSC patient-derived immunocompetent cultures (iPDCs) established on patient-derived omentum gel matrix. We employed genomic and single-cell analysis to assess the intricate and functional characteristics of the iPDCs combined with tumor and immune cell-specific cytotoxic responses. Corroborating the clinical response to Poly (ADP-ribose) polymerase inhibitors (PARPi), iPDCs showed homologous recombination deficiency (HRD) - specific response to PARPi. Importantly, drug responses from iPDCs of chemotherapy and PARPi refractory patients corresponded with patient outcomes and aligned with distinct pathway activities from single-cell RNA sequencing analysis. Furthermore, iPDCs from HRD tumors showed response to anti-PD1 antibody as measured by decrease in tumor cells combined with augmented T cell activation. High-throughput drug testing followed by single cell-imaging from iPDCs revealed patient-specific responses to combination of ataxia telangiectasia and Rad3-related inhibitor (ATRi) with DNA damaging agents or immunotherapies. Integration of cytotoxic responses with immune cell states uncovered patient-specific immune activation with the combination of ATRi and a novel immunotherapy targeting Autotaxin (ATX), and this response was significantly associated with a tumor-cell replication stress biomarker in single-cell analysis of tCycIF highly multiplexed imaging. In conclusion, iPDCs provide a platform for high-throughput screening and functional testing of immuno-oncology agents for precision oncology in HGSC.

cancer biology↗