Mammary extracellular matrix (ECM) from tamoxifen-treated rats suppresses metastatic attributes of transformed mammary epithelial cells in comparison with ECM from control rats. (a) MCF-12A-Ras cell invasion through 8 μm transwell filter pores occluded with 200 μg/ml mammary ECM was suppressed in response to tamoxifen in comparison with control ECM. *p < 0.024. (b) Motility of MDA-MB-231 cells was inhibited in response to filters coated with 10 μg/ml tamoxifen ECM compared with control ECM. *p < 0.005. (c) Using mammary matrices as chemoattractant, MDA-MB-231 cells were less motile towards tamoxifen ECM. *p < 8.3E-5.