Tissue Factor expression is associated with B7-H4-mediated immune evasion in ovarian clear cell carcinoma and with response to tisotumab vedotin in preclinical models

Objective: Ovarian clear cell carcinoma (OCCC) characteristically overexpresses Tissue Factor (TF; F3 ), yet its biological significance and therapeutic implications remain unclear. We aimed to elucidate the impact of TF expression in OCCC and evaluate the antitumor efficacy of the anti-TF antibody-drug conjugate, tisotumab vedotin (TV), in vitro and in vivo models. Methods: We performed bulk RNA sequencing (RNA-seq) of 112 clinical OCCC cases to identify transcriptomic features of F3 -high tumors. We then applied single-nucleus RNA-seq (snRNA-seq) to three F3 -high and three F3 -low cases to characterize tumor biology at the single-cell level. Based on these transcriptomic results, we focused on immune-related pathways and immune-checkpoint molecules, with emphasis on VTCN1 (B7-H4). Immunohistochemistry for TF and B7-H4 was performed on 57 OCCC specimens. Finally, we assessed TV activity in patient-derived OCCC spheroids and xenografts. Results: F3 -high tumors exhibited lower immune scores with upregulation of MYC and cell cycle pathways, and suppression of inflammatory and immune pathways in bulk RNA-seq. Consistently, snRNA-seq showed similar trends in cancer cells, and immune fractions were significantly reduced in F3 -high tumors, indicating an immunologically “cold” state. Notably, the immune-checkpoint molecule VTCN1 was highly expressed in F3 -high tumors and positively correlated with F3 expression. Immunohistochemistry confirmed that B7-H4 was significantly overexpressed in TF-positive tumors, showing a positive correlation between TF and B7-H4 expression.TV activity correlated with TF abundance in vitro and induced marked growth inhibition in F3 -high xenografts; residual tumors showed decreased TF and B7-H4 expression. Conclusions: TF-high OCCC shows a distinct gene expression pattern, particularly an immunologically cold subtype with B7-H4-mediated immune evasion. TV demonstrates TF-dependent activity, supporting TF as a therapeutic target, and providing rationale for TV-based monotherapy or combinations with immunotherapy in OCCC.