IGF1 and myeloid sarcoma: The in vitro analysis has not only confirmed the function of IGF1R and TGFBR1 in the differentiation of Treg cells, but also raised the possibility that let-7i-mediated inhibition of TGFβ signalling and IGF1 signalling might account for the reduction of the Treg cell frequency in patients with MS, because let-7i was also shown to inhibit differentiation of Treg cells (Fig. 5c).