|dc.description.abstracteng||Breast cancer cell invasion is the initial step of the invasion-metastatic cascade, and approximately 90 % of all cancer-related deaths are due to currently incurable cancer metastasis (1). Unique features of tumor microenvironment such as growth factors, cytokines, and extracellular matrix (ECM) composition modify tumor behavior and drive tumor progression (2). Matricellular protein, e.g. Cysteine- Rich Angiogenic Inducer 61 (CYR61), Connective Tissue Growth Factor (CTGF), exert their function by altering cell-ECM interactions, extracellular signaling, and were reported to facilitate angiogenesis, tumor initiation, invasion and progression (3-7).
The tumor microenvironment (TME) is crucial for tumor progression, drug delivery, therapy outcome, and drug efficacy. Identifying drivers that modify TME thereby supporting tumor initiation, invasion and progression would be of benefit to design new treatment options for metastatic breast cancer.
We aimed to identify molecular mechanisms underlying reduced breast cancer invasiveness due to reduced CYR61 expression. Using 2D transwell invasion and 3D spheroid invasion assays to evaluate the effect of CYR61 and downstream targets on the invasiveness of breast cancer cell. Furthermore, we wanted to shed light on the unique interaction between breast cancer cells and osteosarcoma cells. Combining this co-culture model with mass spectrometry–based secretome analysis, we identified potential extracellular secreted drivers of breast cancer invasion. Additionally, we wanted to identify molecular mechanisms underlying reduced breast cancer invasiveness due to reduced CTGF expression by assessing cell–ECM adhesion and proteolytic activity of breast cancer cells and identifying possible treatment options targeting CTGF.
Reduced CYR61 expression led to dephosphorylated ERK1/2 and lower S100A4 expression, thereby decreasing 3D spheroid invaded area growth. These results suggest that CYR61 and S100A4 are predictive markers and therapeutic targets for advanced breast cancer. Targeting CTGF, one potential driver of breast cancer bone-directed invasion, led to reduced proteolytic activity, decreased 2D transwell invasion and 3D spheroid invaded area growth, and increased cell-ECM invasion. Our results demonstrated a RhoA dependent- CTGF regulation, which can be impaired by GnRH agonist treatment.||de