Unraveling the Interactions between Macrophages and Triple-Negative Breast Cancer Cells in a 3D Co-culture Model

Unraveling cell-cell interactions between cancer cells and macrophages in the tumor microenvironment (TME) of triple-negative breast cancer (TNBC) still remains challenging, especially in a standardized 3D culture system. This study used the TNBC cell line, MDA-MB-231, and polarized M1-like or M2-like macrophages derived from THP-1 monocytes to establish a 3D co-culture spheroid system. Drug efficacy, epithelial-mesenchymal transition, macrophage phenotypes, and RNA sequencing were performed. M2 macrophages increased the viability and proliferation rate of MDA-MB-231 cells in 3D spheroids, while both M1 and M2 macrophages reversed the chemo-resistance. Instead of maintaining their phenotypes, M1 and M2 macrophages lost some polarization in 3D co-cultured spheroids. An expected mesenchymal transition was found in 3D MDA-MB-231 cells. However, M1 and M2 macrophages induced a partial epithelial reversion in co-cultured spheroids. Deconvolution of bulk RNA sequencing verified the phenotypic transitions between M1 and M2 macrophages when 3D co-cultured with MDA-MB-231 cells. In conclusion, our findings suggest that a 3D co-culture system of polarized macrophages and TNBC cells can be useful in studying the dynamic cellular phenotype changes that occur in a heterogeneous environment.