Spatially Resolved Molecular Subtyping Uncovers Tumor Progression and Immune Evasion Mechanisms in High-grade Serous Ovarian Cancer

High-grade serous ovarian cancer (HGSOC) is a lethal malignancy characterized by profound intratumoral heterogeneity and immune evasion. Although previous research has identified 4 molecular subtypes of HGSOC, defining their spatial distribution across anatomic sites could help identify functional mediators of progression and immune evasion. In this study, we performed single-cell and spatial transcriptomic sequencing on 66 anatomically paired samples across 5 sites from 8 patients and conducted an integrated analysis on the generated datasets. Five distinct gene programs (GP) with specific spatial distributions and functional roles were identified: GP1 (differentiated-invasive), GP2 (differentiated-proliferative), GP3 (immunoreactive), GP4 (mesenchymal), and GP5 (proliferative). Interestingly, molecular subtypes exhibited dynamic spatial transitions that promote HGSOC progression. The differentiated-proliferative subtype dominated tumor cores, whereas the differentiated-invasive subtype localized to the invasive front driven by SDC4-expressing epithelial cells (c40) that were functionally validated to promote migration/invasion. Concurrently, immune evasion operated through distinct mechanisms. Differentiated-invasive and immunoreactive subtype co-localization established immunosuppression via the TNFα-SAA1/2-APOE signaling axis that recruits immunosuppressive myeloid cells across primary and metastatic sites, whereas fibroblast-derived collagen barriers were constructed at the interfaces between mesenchymal and immunoreactive subtypes in omental metastases along with dysregulated chemokines to exclude immune infiltration. This spatially resolved atlas directly links subtype spatial transitions to tumor progression and subtype co-localization to immune evasion, providing a mechanistic framework for targeting spatially organized tumor-immune interactions in HGSOC. SIGNIFICANCE: Spatially resolved transcriptomic analysis reveals tumor subtype transitions and niche-specific immune evasion mechanisms in ovarian cancer.