Stem cells have the property to induce the invasion of primary somatic cells through insulin-like growth factor I (IGF-I)- or II (IGF-II)-mediated activation of mechanistic target of rapamycin complex 1 (mTORC1). We propose downstream of mTORC1 stem cell-induced invasion is mediated by hypoxia-inducible factor 1-alpha (HIF-1α)-regulated matrix metalloproteinases. Human stem cells use this mechanism to induce invasion and thereby attract cells from the microenvironment in vivo. We have therefore identified a novel feature of human stem cells, which might contribute to the development of stem cell-derived tumours. Cell invasion is required for several physiological processes but it is unknown if stem cells induce invasiveness in other cells. Here, researchers in collaboration with R. Moriggl report in the journal Nature Communications that human stem cells secrete insulin-like growth factor, which in turn activates the mTORC1 pathway, initiating invasive behaviour and attracting other cells.
Host (mouse) cells of various origins display a migratory phenotype in response to mTORC1 activation and accumulate in the teratoma