Abstract
BACKGROUND: Adipose tissue is increasingly recognized as an important component of the tumor microenvironment of colorectal cancer (CRC) and actively contributes to the progression of the disease. Adipose stem cells (ASCs), one of its key constituents, can interact with cancer cells and contribute to tumorigenic processes. However, there is a poor understanding of the underlying basis of ASC-mediated support in the progression of CRC. METHODOLOGY: In this study, we employed direct and indirect co-culture models to investigate interactions between ASCs and colorectal cancer cells. The study was performed using human visceral ASCs (V-ASCs) and subcutaneous ASCs (S-ASCs), along with three colorectal cancer cell lines. The analyses primarily focused on the characteristics of CRC cell progression in 2D and 3D conditions. Cell proliferation and migration after indirect co-culture were assessed using video microscopy, XTT assay, wound healing, and spontaneous migration assay. Corresponding measurements for direct co-culture were performed using high-throughput confocal microscopy. Changes in the epithelial-mesenchymal transition (EMT) such as the phenotype and stemness features were evaluated by confocal microscopy imaging, while gene and protein expression were analyzed using qRT-PCR and Western blotting. Additional analyses were conducted using cells cultured in spheroid models with both indirect and direct cell-cell interaction to assess the spheroid formation capacity, phenotypic characteristics, and the ability of cells to migrate out of the spheroids. RESULTS: The results demonstrate that paracrine interaction with ASCs results in increased migration and proliferation of CRC cells accompanied by EMT-related transcriptional and phenotypic changes and reduced levels of stemness-associated molecules. Notably, direct contact with ASCs potentiated these effects, which suggests more aggressive behavior of the CRC cells. The spheroid assays showed increases in spheroid formation and dispersal capacity of CRC cells with ASCs present under direct co-culture conditions. The findings indicate that both S-ASCs and V-ASCs were associated with comparable changes in CRC cell behavior, despite originating from distinct fat depots. CONCLUSIONS: The results suggest a potential role of ASCs in modulating the plasticity of CRC cells and specific aspects of aggressive behavior, including increased growth and motility, as well as an association with loss of stemness features through distinct interactions that affect tumor progression. This study indicates that targeting physical interactions may be a relevant complement to strategies focused on paracrine signaling within the tumor microenvironment in the development of new therapeutic approaches.