A novel approach for transforming breast cancer stem cells into endothelial cells

Tumor vascular endothelial cells play a pivotal in the tumor microenvironment, influencing the proliferation, invasion, and metastasis of tumor progression. The present study investigated a novel method for inducing the transformation of breast cancer stem cells into endothelial cells, providing a cellular model investigating anti-angiogenic mechanisms in vitro. The breast cancer cell line MCF-7 was used, and the expression of CD133 was initially detected using flow cytometry. CD133⁺ breast cancer cells were purified using immunomagnetic bead sorting technology, yielding an MCF-7^CD133+ subpopulation. The proliferation ability of these cells was assessed using an MTT assay, while their microsphere formation ability was evaluated using a microsphere formation assay. Post-transformation in an optimized endothelial cell culture medium, expression of endothelial cell markers CD31 and CD105 were detected using flow cytometry. Endothelial cell tube formation assays and DiI-labeled acetylated low-density lipoprotein (DiI-Ac-LDL) assays were employed to analyze the endothelial cell function of the MCF-7^CD133+ cells. MDM2/CEN12 gene amplification was detected through fluorescence in situ hybridization (FISH). The MCF-7 breast cancer cell line exhibited 1.7±0.3% trace cells expressing the stem cell surface marker CD133. After anti-CD133 immunomagnetic bead sorting, MCF-7^CD133+ and MCF-7^CD133- subpopulation cells were obtained, with CD133 expression rates of 85.6±2.8 and 0.18±0.08%, respectively. MTT assay results demonstrated that, after 7 days, the proliferation rate of MCF-7^CD133+ cells was significantly higher compared with MCF-7^CD133- cells. MCF-7^CD133+ subpopulation cells displayed strong stem cell characteristics, growing in suspension in serum-free media and forming tumor cell spheres. In contrast, MCF-7^CD133- cells failed to form microspheres. After culturing cells in endothelial cell differentiation and maintenance media, the percentage of MCF-7^CD133+ cells before and after endothelial cell culture was 0.3±0.16 and 81.4±8.37% for CD31⁺ cells and 0.2±0.08 and 83.8±7.24% for CD105⁺ cells, respectively. Vascular-like structure formation and Ac-LDL phagocytosis with red fluorescence in the tube formation assays confirmed endothelial cell function in the MCF-7^CD133+ cells. FISH was used to verify MDM2/CEN12 gene amplification in the induced MCF-7^CD133+ cells, indicating tumor cell characteristics. The modified endothelial cell transformation medium effectively induced differentiated tumor stem cells to express vascular endothelial cell markers and exhibit endothelial functions, ideal for in vitro anti-angiogenesis research.