Small Extracellular Vesicles Promote Stiffness-mediated Metastasis

Area of Science:

• Biomedical Engineering
• Cancer Biology
• Extracellular Matrix Biology

Background:

• Tissue stiffness is a critical prognostic factor in breast cancer.
• Tumor progression and metastatic dissemination are linked to the mechanical properties of the tumor microenvironment.

Purpose of the Study:

• To investigate how physiologic matrix stiffness influences the quantity, protein cargo, and function of small extracellular vesicles (EVs) produced by breast cancer cells.
• To determine the role of these EVs in cancer cell dissemination and the modulation of the tumor microenvironment.

Main Methods:

• Breast cancer cells were cultured on matrices mimicking normal (0.5 kPa) and tumor (25 kPa) stiffness.
• Small extracellular vesicles (EVs) were isolated and characterized for adhesion molecule presentation.
• EVs were tested for binding to extracellular matrix proteins and their homing ability in mice.
• A zebrafish xenograft model was used to assess EV-mediated cancer cell dissemination.
• Gene expression profiles of lung fibroblasts treated with EVs were analyzed.

Main Results:

• EVs from stiff matrices (stiff EVs) showed increased presentation of adhesion molecules (ITGα2β1, ITGα6β4, ITGα6β1, CD44) compared to EVs from soft matrices (soft EVs).
• Stiff EVs demonstrated enhanced binding to collagen IV and a 3-fold increase in organ homing ability in vivo.
• Stiff EVs promoted cancer cell dissemination in a zebrafish xenograft model.
• Exposure to stiff and soft EVs altered gene expression in lung fibroblasts, inducing a cancer-associated fibroblast phenotype.

Conclusions:

• Physiologic matrix stiffness significantly affects the quantity, cargo, and function of breast cancer-derived EVs.
• Stiff EVs play a role in promoting cancer cell dissemination and metastasis.
• EVs can modulate the phenotype of stromal cells, potentially contributing to a pro-tumorigenic microenvironment.