Abstract B060: Spatial landscape of cell cycle dynamics post-neoadjuvant chemotherapy in high-grade serous ovarian carcinoma
Authors: Junquera Ada , Liang Zhihan , Niemiec Iga , Launonen Inga-Maria , Luna-Alvarez Mariana , Salko Matilda , Vääriskoski Maija , Kahelin Essi , Haltia Ulla-Maija , Virtanen Anni , Färkkilä Anniina 
Published: March 2024

Introduction Neoadjuvant chemotherapy (NACT) has emerged as a well-established treatment modality for advanced-stage patients with high-grade serous carcinoma (HGSC). However, relapse and platinum resistance remain significant challenges, resulting in unfavorable long-term outcomes. The interplay between NACT and the tumor microenvironment (TME) is crucial for treatment response, yet its mechanisms are poorly understood. Methods We prospectively recruited &gt;300 newly-diagnosed patients to the Oncosys-OVA study. We performed BRCA1/2 mutational profiling and genomic scarring (ovaHRDscar) to annotate the HGSCs to distinct genomic groups. Detailed surgical and clinical data were collected to assess NACT responses, while histological examination using H&E staining annotated the morphological response patterns of HGSC. Tissue cyclic immunofluorescence (tCycIF) analysis was conducted on FFPE samples collected from the same cohort. We built and validated a tCycIF panel with antibodies targeting cell cycle-regulators and checkpoint inhibitors (Cyclin A, Cyclin D, p21, p27), proliferation (Ki-67, PCNA), and DNA damage markers (RAD51, γH2AX, p53), alongside other cell-type markers for tumor, stromal, lymphoid and myeloid populations. We used GeoMX spatial transcriptomics to capture spatially resolved and cell-population deconvoluted gene expression profiles within regions of interest from tCycIF spatial analyses. Results We employed tCycIF utilizing a validated custom-made antibody panel targeting up to 50 markers to characterize the cell populations in the TME, including their functional states, cell cycle profiles and DNA damage patterns. Via advanced image analysis, we revealed the spatial topographies of tumor-immune and stromal cells, cellular communities, and cell-cell interactions within the TME. Through the utilization of computational methods, we reconstructed the cell cycle dynamics and assessed the expression of markers in cells in pseudotime. Furthermore, by conducting a multivariate assessment of the proliferation markers, we were able to evaluate the spatial distribution of cells with distinct proliferative characteristics. To explore the transcriptome of these regions, we developed a pipeline that integrates tCycIF and GeoMx data, enabling the precise targeting of cell populations in adjacent slides. By examining the gene-expression signatures and enriched pathways within these regions, we uncovered molecular signatures associated with distinct morphological response patterns to NACT. These comprehensive analyses were integrated with the matching clinical, pathological, and genomic profiling information, leading to the identification of recurring cellular neighborhoods with potential therapeutic implications. Conclusions By integrating multi-omics and spatio-temporal analyses with clinicopathological features, we identified response-related patterns that could inform patient stratification and treatment selection. This study can potentially drive advancements in immuno-oncology and personalized therapeutic approaches for patients with HGSC.

Citation Format: Ada Junquera, Zhihan Liang, Iga Niemiec, Inga-Maria Launonen, Mariana Luna-Alvarez, Matilda Salko, Maija Vääriskoski, Essi Kahelin, Ulla-Maija Haltia, Anni Virtanen, Anniina Färkkilä. Spatial landscape of cell cycle dynamics post-neoadjuvant chemotherapy in high-grade serous ovarian carcinoma [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr B060.