Effect of substrate stiffness on the mechanical properties of cervical cancer cells

Cervical cancer microenvironment is involved in the regulation of the behavior, morphology, and mechanical properties of the cervical cancer cells. Integrins expressed on the cell membrane combine with the factors of the microenvironment to determine cervical cancer cells' properties. The mechanical properties of integrin-extracellular matrix (ECM) interactions are important for the mechanotransduction of cervical cancer cells. However, the quantified study on the adhesion force and binding probabilities between collagen and integrins on cervical cancer cells grown on different stiffness substrates have not been reported. Polyacrylamide (PA) gel was used as substrate to mimic the mechanical microenvironment of cancer cells. ImageJ software was used to measure the perimeter and area of the cells. SiHa cells were stained with FITC phalloidine to observe the cytoskeleton. Atomic force microscopy (AFM) was used to measure the cell mechanical properties. The perimeters of SiHa cells grown on different stiffness substrates were 63.4 ± 1.3, 102.8 ± 4.0, and 152.6 ± 4.1 μm, for soft, intermediate, and stiff substrates, respectively. These areas were 277.2 ± 13.3, 428.9 ± 26.0, and 1166.0 ± 63.2 μm2, for soft, intermediate, and stiff substrates, respectively. The Young's modulus of SiHa cells grown on stiff substrates (3.0 ± 0.02 kPa) was higher compared with those on soft substrates (0.6 ± 0.01 kPa) or intermediate substrates (bimodal distribution, 1.36 and 1.67 kPa). The adhesion force between the functionalized probe and SiHa cells grown on glass (55.65 ± 0.78 pN) was significantly greater than that on stiff (47.03 ± 0.85 pN), intermediate (34.07 ± 0.58 pN) and soft (27.94 ± 0.47 pN) substrates. The binding probabilities of the collagen-integrin of the four rigid substrates were significantly differed. The changes in substrate stiffness can obviously regulate SiHa cells' mechanical properties, such as the Young's modulus. The adhesion force and binding probabilities of SiHa cells both increased with increasing substrate strength.