Breast Cancer Stem Cells Upregulate IRF6 in Stromal Fibroblasts to Induce Stromagenesis

• Published in: Cells (Basel, Switzerland) Vol. 13; no. 17; p. 1466
• Main Authors: Muralidharan, Harshini, Hansen, Thomas, Steinle, Anja, Schumacher, David, Stickeler, Elmar, Maurer, Jochen
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 31-08-2024
• Subjects: Animals; Antibiotics; BCSC niche; BCSC–fibroblast interaction; Breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; CAF; Cancer-Associated Fibroblasts - metabolism; Cancer-Associated Fibroblasts - pathology; Cell culture; Cell Line, Tumor; Coculture Techniques; Collagen (type I); Female; Fibroblasts; Fibroblasts - metabolism; Fibroblasts - pathology; Fibronectin; Fibrosis; Gene Expression Regulation, Neoplastic; Humans; Hypoxia; Interferon regulatory factor; Interferon Regulatory Factors - genetics; Interferon Regulatory Factors - metabolism; IRF6; Metastasis; Mice; Microenvironments; Neoplastic Stem Cells - metabolism; Neoplastic Stem Cells - pathology; Plasmids; Stem cells; Stromal Cells - metabolism; Stromal Cells - pathology; Triple Negative Breast Neoplasms - genetics; Triple Negative Breast Neoplasms - metabolism; Triple Negative Breast Neoplasms - pathology; triple-negative BCSC; Tumor Microenvironment; Up-Regulation - genetics; United Kingdom > UK; United States > US; Basel Switzerland; Switzerland; Germany; BCSC niche; triple-negative BCSC; CAF; fibrosis; IRF6; tumor stroma; BCSC–fibroblast interaction; stromagenesis
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells13171466

The microenvironment of a cancer stem cell (CSC) niche is often found in coexistence with cancer-associated fibroblasts (CAFs). Here, we show the first in-depth analysis of the interaction between primary triple-negative breast cancer stem cells (BCSCs) with fibroblasts. Using 2D co-culture models with specific seeding ratios, we identified stromal fibroblast aggregation at the BCSC cluster periphery, and, on closer observation, the aggregated fibroblasts was found to encircle BCSC clusters in nematic organization. In addition, collagen type I and fibronectin accumulation were also found at the BCSC-stromal periphery. MACE-Seq analysis of BCSC-encapsulating fibroblasts displayed the transformation of stromal fibroblasts to CAFs and the upregulation of fibrosis regulating genes of which the Interferon Regulatory Factor 6 (
) gene was identified. Loss of function experiments with the
gene decreased fibroblast encapsulation around BCSC clusters in 2D co-cultures. In BCSC xenografts, fibroblast IRF6 expression led to an increase in the stromal area and fibroblast density in tumors, in addition to a reduction in necrotic growth. Based on our findings, we propose that fibroblast IRF6 function is an important factor in the development of the stromal microenvironment and in sustaining the BCSC tumor niche.