Integrin α2β1 and DDR2 bind to collagen type XI. (A) Expression of collagen receptors on CAF. Expression of integrin α1 (ITGA1), integrin α2 (ITGA2), integrin α10 (ITGA10), integrin α11 (ITGA11), DDR1 and DDR2 was analyzed by qPCR in CAF extracted from NSCLC patient tissue (n = 12). (B) Integrin binding to collagen type XI. C2C12 cells or C2C12 cells expressing either integrin α1 (C2C12-α1), integrin α2 (C2C12-α2) or integrin α11 (C2C12-α11) were seeded on fibrillar collagen type I and collagen type XI for 40 min. Cells were stained with crystal violet and absorbance was read at 595 nm. BSA and fibronectin were used as negative and positive controls for cell adhesion, respectively. Statistics were performed using Mann–Whitney test (n = 6, mean ± SD). (C) Direct interaction of integrin α2β1 and collagen type XI was confirmed by solid phase assay. Recombinant integrin α2β1 at the concentration of 20 nM was incubated for 3 h on immobilized collagen type I or collagen type XI coating or on heat-denatured collagens as the control. Fibronectin coating was used as the negative control. (D) Solid phase binding assay was carried out on immobilized collagen type XI or fibronectin using a different concentration of recombinant integrin α2β1. The dissociation constant Kd has been determined by the Scatchard equation. (E) Direct interaction of DDR2 and collagen type XI was confirmed by solid phase assay. Recombinant DDR2-Fc at the concentration of 50 nM was incubated for 3 h on immobilized collagen type I or collagen type XI coating or on-heat denatured collagens as the control. Fibronectin coating was used as the negative control. (F) Solid phase binding assay was carried out on immobilized collagen type XI or fibronectin using a different concentration of recombinant DDR2-Fc. The dissociation constant Kd has been determined by the Scatchard equation. n.s.; not significant.