THBS1 and breast cancer: Of note, another member of the thrombospondin-encoding genes, THBS1 (alias TSP-1), was reported to be down-regulated in uterine fibroids (Behera et al., 2007) and TSP-1 production has been shown to be directly controlled by estrogens in estrogen receptor-positive breast cancer cells (Hyder et al., 2009), suggesting that TSP-1 may function in the estrogen receptor-positive UL cells as well.