LIF: a molecule with divergent actions on myeloid leukaemic cells and embryonic stem cells

We have previously characterized, purified and cloned a novel murine and human regulator [leukaemia inhibitory factor, LIF] which induces the differentiation of certain murine and human myeloid leukaemic cells. Recently we have shown that there are specific LIF receptors on murine embryonic stem [ES] and embryonal carcinoma [EC] cells and that purified recombinant LIF can substitute for feeder cells and crude sources of differentiation inhibiting activity [DIA] [such as BRL-cell-conditioned medium] in the maintenance of ES cells in a pluripotential state in vitro. Furthermore, ES cells maintained in culture in recombinant LIF for a prolonged period can give rise to germline chimaeric mice. Thus, based on a number of biochemical and biological similarities, it is likely that LIF and DIA are the same molecule. The identification of LIF as a molecule, necessary and sufficient for the maintenance of ES cells in culture, should have a profound impact on the use of these cells for genetic manipulations.