Distinct sFOLR1 and Cytokine Secretion Profiles Across Marker-Enriched OVCAR-3 Ovarian Cancer Cell Subpopulations: A Pilot Study

Background: Folate Receptor Alpha (FRα), encoded by the Folate Receptor 1 (FOLR1) gene, is expressed in many high-grade serous ovarian carcinomas, but the tumor-cell phenotypes contributing to soluble FOLR1 (sFOLR1) release remain unclear. This pilot study compared sFOLR1 and cytokine secretion across OVCAR-3 fractions enriched for CD133, EpCAM/CD326, CD90, and ABCG2/CD338. Methods: The parental OVCAR-3 culture was phenotyped by flow cytometry and separated into marker-positive and marker-negative fractions using CD133, EpCAM/CD326, and ABCG2/CD338 immunomagnetic selection. CD90-positive and corresponding negative fractions were isolated after indirect co-culture of OVCAR-3 cells with primary mesenchymal stromal cells. Paired fractions were cultured for 120 h, and sFOLR1, vascular endothelial growth factor (VEGF), interleukin (IL)-6, and IL-10 were measured at 24 h intervals. Results: sFOLR1 release varied markedly by time and phenotype. CD133-positive and CD326-positive fractions showed time-dependent increases; CD90-positive maintained low, comparatively stable concentrations; and CD338-positive declined from a high early value, while the corresponding negative fraction increased. In CD133-positive and CD326-positive fractions, sFOLR1 tracked with VEGF and/or IL-6, whereas CD90-positive and CD338-positive fractions showed distinct, partly uncoupled cytokine patterns. Conclusions: These exploratory associations in a single cell line support further investigation of sFOLR1 and cytokine profiles.