Thrombospondin-1 (TSP-1), a multimodular Ca2+-binding trimeric matricellular glycoprotein, is secreted by a wide array of cells such as platelets, fibroblasts, macrophages, dendritic cells, vascular smooth muscle cells, keratinocytes, epithelial cells, endothelial cells, and several cancer cells [1–3]. The gene discussed is THBS1; the disease is cancer.