FN1 and breast cancer: Mechanistically, cell adhesion to BSP primarily occurs via its RGD sequence, which engages integrin receptors.148 This interaction is BSP-specific: recombinant human BSP-KAE fragments and fibronectin (FN)-derived GRGDSP fail to stimulate MDA-MB-231 adhesion.122 Notably, exogenous FN-derived GRGDS has no effect on MDA-MB-231 cell adhesion to human bone ECM, while fragments of recombinant human BSP significantly decrease breast cancer cell attachment to human ECM [2 μmol/L (≈2.4-134 μg/mL)], following 3 h,39 highlighting the unique role of BSP in cancer cell adhesion, particularly to bone.