FN1 and breast carcinoma: Bone is comprised of 95% collagen type I, with fibronectin and laminin present within the bone marrow ECM (Vituri et al, 2000) and laminin also a key component of the sinusoidal basement membrane (Gu et al, 2003), so the upregulation of integrins that bind to these ECM components may explain the fact that breast cancer cells predominately metastasise to bone (Powell et al, 1991).