Elacridar Reverses P-gp-Mediated Drug Resistance in Ovarian Cancer Cells in 2D and 3D Culture Models

Multidrug resistance (MDR) remains a major obstacle in the treatment of ovarian cancer. MDR is often mediated by the overexpression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP). In this study, we evaluated the ability of elacridar, a dual P-gp and BCRP inhibitor, to overcome MDR in W1, an ovarian cancer cell line sensitive to Paclitaxel (PAC) and its PAC-resistant variants. Cells were cultured under both two-dimensional (2D) and three-dimensional (3D) conditions to account for differences in tumor-like microenvironments. The MDR1 gene and P-gp protein expression were determined for the analyzed model; P-gp activity was measured by flow-cytometry and fluorescent observation, with and without elacridar. The MTT tests were carried out to evaluate how elacridar, combined with chemotherapeutics, affects cell viability. Our results demonstrate that elacridar effectively inhibited transporter activity and increased cellular sensitivity to PAC and DOX. The inhibitory effect was observed in both 2D and 3D cultures, although the re-sensitization effect in 3D conditions was less pronounced, reflecting the complexity of tumor-specific resistance mechanisms. These findings highlight elacridar as a promising compound for reversing MDR in ovarian cancer and emphasize the importance of 3D models in preclinical drug evaluation. Further studies in advanced in vitro and in vivo models are required to assess the potential of elacridar better.