Three-Dimensional Matrix Stiffness Modulates Mechanosensitive and Phenotypic Alterations in Oral Squamous Cell Carcinoma Spheroids

Extracellular biophysical cues such as matrix stiffness are key stimuli tuning cell fate and affecting tumor progression in vivo. However, it remains unclear how spheroids in a 3D microenvironment perceive matrix mechanical stiffness stimuli and translate them into intracellular signals driving cancer. Mechanosensitive Piezo1 and TRPV4 ion channels, upregulated in many malignancies, are major transducers of such physical stimuli into biochemical responses. Most mechanotransduction studies probing the reception of changing stiffness cues by cells are, however, still limited to 2D culture systems or cell-extracellular matrix models which lack the major cell-cell interactions prevalent in 3D cancer tumors. Here, we engineered a 3D spheroid culture environment with varying mechanobiological properties to study the effect of static matrix stiffness stimuli on mechanosensitive and malignant phenotypes in oral squamous cell carcinoma spheroids. We find that spheroid growth is enhanced when cultured in stiff extracellular matrix. Using flow cytometry, we show that the expression of mechanoreceptor Piezo1 and stemness marker CD44 is upregulated in stiff matrix. We also report the upregulation of a selection of genes with associations to mechanoreception, ion channel transport, extracellular matrix organization, and tumorigenic phenotypes in stiff matrix spheroids. Together, our results indicate that cancer cells in 3D spheroids utilize mechanosensitive ion channels Piezo1 and TRPV4 to sense changes in static extracellular matrix stiffness and that stiffness drives pro-tumorigenic phenotypes in oral squamous cell carcinoma. Overall design: Cal27 spheroids were cultured in soft (3 mg/mL Matrigel) and stiff (12 mg/mL Matrigel) using the liquid overlay technique. Spheroids cultured in both conditions were harvested on day 14 and total RNA was isolated and sequenced.