Extracellular adenosine triphosphate upregulates S100A4 expression and promotes the migration and invasion of breast cancer cells via P2Y2/SOX9 signaling.

BACKGROUND: The tumor microenvironment (TME), composed of tumor cells, mesenchymal cells, and diverse extracellular molecules, plays a pivotal regulatory role in tumor initiation, malignant progression, and the development of anti-cancer therapeutic resistance. Extracellular adenosine triphosphate (ATP) is a critical bioactive signaling molecule in the TME. Previous studies from our group have confirmed that extracellular ATP is extensively involved in multiple malignant phenotypes of prostate cancer and breast cancer, including tumor cell migration, invasion, chemotherapeutic resistance, and the maintenance of cancer stem cell properties. In our prior work, we demonstrated that extracellular ATP acts on stromal fibroblasts in the breast cancer microenvironment to facilitate the formation of a pro-tumorigenic niche. However, the full molecular mechanism governing this regulatory axis remains incompletely elucidated. Here, we aim to uncover its underlying mechanism, thereby providing new insights for the development of breast cancer therapeutic strategies.

METHODS: In this study, primary breast cancer cells isolated from clinical breast cancer tissue specimens were used as the core research model. A series of experimental approaches were applied, including extracellular ATP stimulation assays, P2 receptor intervention, SOX9 gene loss-of-function manipulations, S100A4 expression detection at both transcriptional and translational levels, transwell invasion assays of primary breast cancer cells and fibroblasts, to evaluate the formation efficiency of cancer-associated fibroblasts (CAFs).

RESULTS: Our experimental results revealed that extracellular ATP can significantly upregulate the expression of S100A4 in primary breast cancer cells. In terms of mechanism, this regulatory effect is mediated by the P2 receptor-SOX9 signaling axis. Specifically, the binding of extracellular ATP to its membrane P2 receptors activates the downstream transcription factor SOX9, which further transcriptionally promotes the expression of target gene S100A4. Functional validation experiments confirmed that this signaling cascade subsequently enhances the migration and invasion capacities of breast cancer cells.

CONCLUSIONS: This study identified a novel regulatory pathway mediated by extracellular ATP in the breast cancer microenvironment; that is, the P2 receptor-SOX9-S100A4 signaling axis, which promotes the malignant progression of breast cancer and the remodeling of the tumor stroma. These findings not only expand the mechanistic understanding of extracellular ATP in the tumor-promoting microenvironment but also provide a potential new molecular for the targeted intervention of breast cancer metastatic progression and stromal therapy resistance.