Dose-dependent CXCR4 inhibition in ovarian cancer cellular models reveals a paradoxical response characterized by subtype-specific oncogenic suppression and stress-induced adaptive rebound.

BACKGROUND

The CXCL12/CXCR4 signaling axis drives ovarian cancer progression, metastasis, and chemoresistance, making it a key therapeutic target. However, the biological consequences of prolonged high-dose inhibition remain poorly characterized. This study investigated the dose-dependent molecular and functional effects of prolonged exposure to the selective CXCR4 antagonist USL311 in heterogeneous ovarian cancer models (ES2 and HAY cell lines).

METHODS

Cells were treated with 50, 75, or 100 µM USL311 for 72 h. Western blot, immunofluorescence, cytotoxicity, and wound-healing assays evaluated signaling cascades, protein expressions, and functional outcomes.

RESULTS

CXCR4 inhibition triggered highly discrete, lineage-specific molecular responses. ES2 cells exhibited a prominent biphasic pattern; 50 µM USL311 significantly suppressed CXCR4 and Cyclin D1 expression, but higher concentrations induced a paradoxical rebound expression driven by a HIF1α-dependent adaptive stress mechanism, despite p-AKT suppression and marked cytotoxicity. Conversely, HAY cells bypassed this cascade via a HIF1α-independent pathway, initiating a compensatory escape network marked by a structural rebound in p-AKT activation and significant upregulation of metastatic enzymes MMP2 and MMP9 under identical conditions.

CONCLUSION

CXCR4 inhibition induces highly complex, concentration- and cell-line-dependent biological responses. Moderate inhibition effectively suppressed oncogenic signaling pathways, whereas excessive inhibition triggered paradoxical compensatory responses that vary across ovarian cancer subtypes. These findings highlight the critical importance of therapeutic dose optimization and provide crucial mechanistic insights into the limitations of high-dose CXCR4-targeted therapy in ovarian cancer.