Expression of leukemia inhibitory factor is regulated in human mesenchymal cells

A protein variously termed leukemia inhibitory factor (LIF), differentiation-inducing factor, differentiation inhibitory activity or human interleukin for DA cells can control the differentiation and proliferation of hematopoietic cells as well as of several other cellular lineages. In order to further elucidate the spectrum of LIF-producing cells, we examined different cell types for the expression of LIF mRNA using Northern blot analysis. LIF mRNA was detected in activated normal human T-cells and in two T-cell lines but was undetectable in a B-lymphoid cell line, in both resting and activated normal human granulocytes and monocytes and in human myeloid cell lines K562 and HL-60. In human lung fibroblasts and in human umbilical vein endothelial cells, LIF was constitutively expressed and its accumulation was increased in a time-dependent manner following treatment with the phorbol ester TPA and in the presence of the two immediate response cytokines tumor necrosis factor (TNF)-alpha and interleukin (IL)-1-beta. We conclude that mRNA for LIF is not only expressed by T-cells but also in human mesenchymal cells. Expression of LIF transcripts in these cells is constitutive and can be significantly enhanced by phorbol ester, TNF-alpha and IL-1-beta.