TGFB1 and cancer: A model for cancer metastasis proposes that it is initiated by EMT that is possibly spurred by TGFβ1-expressing macrophages, and in the destination niche, it is accomplished by a mesenchymal-to-epithelial transition that is facilitated by resident cells such as Ly6C+ myeloid progenitor, which have been shown to express extracellular matrix proteoglycan versican in metastatic lungs [148].