Mammary extracellular matrix (ECM) isolated from tamoxifen-treated rats inhibits tumours in an orthotopic xenograft model. (a) MDA-MB-231 tumour cells mixed with tamoxifen ECM formed smaller tumours than when mixed with control ECM. n = 20 per group. (b) MDA-MB-231 tumour cells mixed with 20 μg/ml fibronectin had a trend towards larger tumour size, consistent with fibronectin contributing to larger tumour size observed with control ECM. n = 10 per group.