Introduction/Background Ovarian cancer is an aggressive disease characterized by extensive intraperitoneal dissemination. However, the mechanisms underlying the facilitation of metastasis within site-specific microenvironments remain unknown.

Methodology We analyzed approximately paired 60 whole genome- and bulk RNA-sequencing, ~ 150, 000 of single cells and two million spots of spatial transcriptomics (ST) data to profile site-specific microenvironment and cell-cell contact in situ. We conducted in vitro and in vivo experiments to confirm phenotypes and validate our hypothesis.

Results We unveiled a spatiotemporal landscape of ovarian cancer, elucidating the roles of metastatic units (MU), comprised of tripartite ensemble of MMP11+ myCAFs, epithelial cells and SPP1+ macrophages, in promoting tumor spread. In vitro and in vivo experiments indicated that MU could be targeted and disrupted by gene X and gene Y inhibition. We observed dynamic conversions on ST, with immune-activated cell neighborhoods in ovaries transitioning to stromal-like in metastases. Moreover, utilizing our newly designed STARLETS framework, we elucidated a Darwinian evolutionary process driven by hypoxia and immune selections occurring in the ovary while selected clone subsequently migrated to liver.

Conclusion Our results provided novel insights into the mechanisms of metastasis and offered a foundation for further investigations into the co-evolution of tumors and host systems, as well as treatments that target the interplay between malignant tumors and immune cells in ascites.

Disclosures The authors have no competing interests.