Combined Effect of Metformin and miR-145/miR-23b Co-Transfection on Proliferation and Progression in 2D and 3D Epithelial Ovarian Cancer Models

Epithelial ovarian cancer (EOC) remains a lethal malignancy requiring novel therapeutic strategies due to high recurrence and chemoresistance. This study evaluated the combined antitumor effect of metformin and the co-transfection of tumor-suppressor microRNAs miR-145 and miR-23b in A2780 and OV90 EOC cell lines using both 2D and 3D models. In monolayer cultures, our approach significantly reduced the expression of proliferation markers Ki-67 and c-MYC, and decreased cell migration and invasion in both cell lines compared to controls. In 3D spheroid models, the treatment reduced VEGF secretion and relative spheroid area in A2780 cells, significantly increasing cytotoxicity; however, OV90 spheroids exhibited marked resistance. Fluorescent miRNA tracking revealed that this resistance occurs despite successful intracellular delivery, indicating an intrinsic biological resistance conferred by the 3D microenvironment. Overall, these findings suggest that the combined administration of metformin and miRs effectively limits tumor progression, but also strongly underscore the importance of using complex 3D models to accurately evaluate therapeutic efficacy and intrinsic resistance mechanisms.