TGFB1 and neoplasm: The experimental shGREM1-MSCs-CM-induced anti-tumour stem cells effects seem to be controlled by the TGF-β/BMP4 (transforming growth factor-β/bone morphogenetic protein-4) signalling pathway, which was also associated with a decrease in TGF-β and Smad-2 and Smad-3 activity, and with an increase in BMP4, Smad-1, Smad-5 and Smad-8 expression.