Characterizing intra- and intertumor heterogeneity in ovarian high-grade serous carcinoma subtypes using single-cell and spatial transcriptomics.

Ovarian high-grade serous carcinoma (HGSC) is an aggressive ovarian cancer with a heterogeneous tumor microenvironment (TME). Advances in single-cell RNA sequencing (scRNA-seq) and spatially-resolved transcriptomics have enabled the study of complex TME. This study explores connections between molecular subtypes described from bulk transcriptomes and spatial domains characterized by distinct gene expression in HGSC and their variability between patients. We quantify both intra- and intertumor heterogeneity across 2D space and identify differing spatial patterns of gene expression pertaining to immune pathways and vasculature development. Functional characterization of tumor spaces reveals potentially shared cell states across molecular subtypes, while correlation analysis underscores subtype-specific spatial anti-colocalization between spots exhibiting antigen-presenting functions and B cell-mediated immunity. Lastly, we perform spatially-aware cell-cell communication analysis on the spatial samples and identify a molecular subtype specific difference in total signaling activity and heterogeneity in Midkine signaling between the differentiated subtype. Our results suggest that generating multiple tissue slices per patient might be necessary to enable comprehensive characterization of HGSC spatial transcriptomes.