For example, cancer cell quiescence in the lung is mediated by thrombospondin 1 (TSP1) and bone morphogenetic protein 4 (BMP4), whereas in the bone marrow, TSP1, BMP7, transforming growth factor β2 (TGFβ2), and growth arrest-specific 6 (GAS6) induce and maintain quiescence [174,175]. Here, BMP4 is linked to cancer.