PLLA Porous Scaffold as a 3D Breast Cancer Model to Investigate Drug Resistance.

Multidrug resistance remains one of the major challenges in breast cancer research, often leading to treatment failure. To better understand this mechanism, sophisticated three-dimensional (3D) tumor models are necessary, as they offer several advantages over traditional bidimensional (2D) cultures. In this study, poly-l-lactic-acid porous scaffolds were produced using a thermally induced phase separation technique and employed as 3D models for breast cancer cell lines: MDA-MB-231, MCF-7, and its multidrug-resistant variant, MCF-7R. The MTS assay was used to compare growth inhibition following doxorubicin treatment in 2D and 3D. Remarkably, the IC₅₀ values increased in 3D cultures compared to 2D: MDA-MB-231 (445 vs. 54.5 ng/mL), MCF-7 (7.45 vs. 0.75 μg/mL), and MCF-7R (165 vs. 39 μg/mL). MCF-7R, which usually shows greater resistance in 2D, demonstrated even higher resistance in 3D. In fact, IC₅₀ was not reached within 3 days as with the other models, but only after 6 days. Cellular morphology also played a crucial role. When treated with concentrations higher than the IC₅₀, MDA-MB-231 cells lost their physiological 3D clustered structure, while MCF-7 and its resistant variant exhibited disrupted layers. All cell lines in 3D showed higher chemoresistance, suggesting a more biomimetic spatial architecture. Our work bridges the gap between monolayer and animal models, highlighting the potential of polymeric 3D scaffolds in breast cancer research.