Mesenchymal stem cell-macrophages influence cancer stemness and AKT1/YKL-39 expression in triple-negative breast cancer

Introduction: Triple-negative breast cancer (TNBC) has greater infiltration of tumor-associated macrophages (TAMs) than other breast-cancer subtypes. Mesenchymal stromal/stem cells (MSCs) have been shown to shape macrophage polarization, promoting the conversion of naïve M0 macrophages to an M1-like phenotype that restricts cancer-cell growth. However, reciprocal relationships between macrophages and cancer stem cells (CSCs) may promote the CSC niche and drive macrophages to transition toward an M2-like phenotype in the tumor microenvironment (TME). This study explores the effects of MSC-polarized macrophages (M0/MSCs) on CSCs and evaluates their role in TNBC progression. Methods: M0 macrophages derived from THP-1 cells were co-cultured with UC-MSCs for 72 h, then co-cultured with breast cancer stem cells (BCSCs) originating from MDA-MB-231 cells. Gene-expression profiles were assessed by qRT-PCR of total RNA extracted from each cell type, focusing on M1/M2 polarization and CSC markers. Subsequently, MDA-MB-231 and MCF-10A cells were cultured for 72 h in conditioned medium (CM) obtained from the CSC/M0-MSC co-culture. An MTT assay was used to measure cell viability, and the impact on breast-cancer-related genes was analyzed by qRT-PCR. Results: Co-culturing M0/MSCs with BCSCs (CSC/M0-MSCs) induced an M2-like macrophage phenotype, marked by elevated IRF4 and increased TNF-α expression. Conversely, SOX-2 and OCT-4 expression was reduced in BCSCs co-cultured with M0/MSCs. MDA-MB-231 cells exposed to co-culture-derived CM for 72 h showed a non-significant decrease in viability and down-regulation of AKT1 and YKL-39. Conclusion: Co-culturing M0/MSC macrophages with BCSCs elevated IRF4 and TNF-α in macrophages while reducing SOX-2 and OCT-4 in BCSCs. The elevation of TNF-α indicates M2-like polarization; however, its context-dependent effects on stemness warrant further investigation. In addition, CM from the CSC/M0-MSC co-culture modulated AKT1 and YKL-39 expression. These findings underscore the need to further elucidate MSC–macrophage–BCSC interactions to develop more effective therapies targeting the TNBC TME.