Üç Boyutlu (3B) Ortamda Oluşturulan Meme Kanseri Sferoidlerinde Abemaciclibin Etkisinin Araştırılması

Abstract

Cancer remains one of the most prevalent and lethal diseases worldwide. Breast cancer—the most common malignancy in women—also ranks first in cancer-related mortality. Among its subtypes, triple-negative breast cancer (TNBC) stands out for its pronounced aggressiveness, metastatic potential, and poor prognosis. Inhibiting serine/threonine kinases has emerged as an innovative drug-development strategy; in this context, Abemaciclib, a selective cyclin-dependent kinase 4/6 (CDK-4/6) inhibitor, halts the cell cycle and can curb the uncontrolled proliferation of tumour cells. Because ethical constraints limit human studies and animal models do not fully recapitulate human physiology, three-dimensional (3D) cell-culture systems that better mimic tumour tissue are gaining importance. Spheroids—3D aggregates formed by self-organization of cells in a scaffold-free environment—are now widely used to elucidate oncogenic mechanisms and to improve drug screening. In this thesis, spheroids of the triple-negative breast cancer (TNBC) cell line MDA-MB-231 were generated using the 3D Petri Dish® method. The effects of Abemaciclib, a selective CDK-4/6 inhibitor, were then compared with those of the positive control Doxorubicin. Abemaciclib was applied at 10, 20 and 25 µM, while Doxorubicin was administered at 5, 10 and 20 µM, and the cytotoxic effects of the drugs against the cells were measured with 3-(4,5-dimethylthiazol-2-yl)-5-(3 carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Immunofluorescence staining for E-cadherin and filamentous actin (F-actin) was performed to assess changes in the cytoskeleton and cell–cell junctions. Finally, cellular death pathways were explored by analyzing the cell cycle via flow cytometry. The results showed that 3D spheroids exhibited greater resistance to Abemaciclib than conventional two-dimensional (2D) cultures. F-actin staining confirmed structural changes in the cytoskeleton and intercellular contacts, while E-cadherin expression was absent, reflecting the diminished expression of this junctional protein. Cell-cycle analysis revealed that Abemaciclib reduced uncontrolled proliferation of MDA-MB-231 cells by arresting them in both G0/G1 and G2/M phases in a dose-dependent manner. Overall, this study demonstrates that 3D cell-culture models provide a more realistic platform for evaluating drug responses in aggressive cancers such as TNBC and highlights Abemaciclib as a promising therapeutic candidate for TNBC.