Leukemia inhibitory factor (LIF) is a cytokine encoded by the LIF gene. LIF is an IL-6 class protein that inhibits cell differentiation, affecting cell growth. A decrease in LIF levels signals the cells to differentiate. In developing embryos, trophectoderm expresses LIF. LIF binds to LIF-receptor (LIFR), present throughout the embryonic inner cell mass. During the blastocyst stage, the inner cell mass produces embryonic stem cells, and if we remove these cells from the inner cell mass, the embryo loses its LIF source.
LIF is produced as a 202 amino acid precursor protein. Upon removing 22 amino acids post-translationally, it processes the precursor protein into a 20 kilodalton active form. LIF is a stable and compact helix bundle composed of four helices, helix A, helix B, helix C, and helix D. LIF binds to its receptor LIFR and forms a heterodimer with the signal-transducing subunit GP130. GP130 is common to all LIFR receptor families. The heterodimer-complex formed activates the JAK/STAT and MAPK cascades, which in turn activates several pluripotency factors including Nanog, Sox-2, and Oct-4.
Some of the LIF aliases are LIF IL-6 6 Family Cytokine 2 3 5, Leukemia Inhibitory Factor 2 3 4, Hilda 2 3 4, Differentiation Inhibitory Activity 2 3, Cholinergic Differentiation Factor 2 3, Differentiation-Stimulating Factor 3 4.
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LIF testing detects its levels in the samples and helps us understand the function of the leukemia inhibitory factor. We at NorthEast BioLabs use MSD, Luminex, and ELISA assays to detect LIF cytokine in your samples. Below is a detailed ELISA protocol.
We begin LIF cytokine testing with a pre-coated antibody microplate, add 100 μl of sample or standard in each well, and incubate it for 2 hrs at 37℃. The antibody is specific to LIF, therefore any LIF present in the sample gets bound to the immobilized antibody. We then remove all the liquid from the wells, add 100 μl of biotin-conjugated antibody in each well, and incubate it for 1 hr at 37℃. We then wash the wells and incubate them with 100 μl Avidin-conjugated HRP for 1 hr at 37℃. To eliminate any unbounded reagent, we wash the wells, introduce 90 μl of TMB substrate solution, and incubate it for 15-30 mins at 37℃. The addition of TMB substrate solution results in color development in the well. Lastly, we add 50 μl of stop solution to end the reaction and measure the color intensity at 450 nm.
This sandwich-based, enzyme immunoassay technique has a detection range of 9.375 pg/ml – 600 pg/ml and can detect a minimum dose of 2.34 pg/ml LIF cytokine. The assay is highly precise with an inter-assay precision of < 10% and intra-assay precision of < 8%.
LIF cytokine is a pleiotropic cytokine that chiefly regulates the differentiation of leukemic cells. LIF can stimulate protein synthesis of acute-phase in hepatocytes, induce terminal differentiation in leukemic cells, and aid myeloid leukemia cells for hematopoietic differentiation. LIF is involved in kidney development and extracellular matrix repair. Research in transgenic mice with over-expressing-LIF showed that the mice developed mesangial proliferative glomerulonephritis. Researchers also introduce LIF to stem cell cultures for reducing spontaneous differentiation of the cells.
To learn more about leukemia inhibitory factor function, explore the resources below.
https://www.genecards.org/cgi-bin/carddisp.pl?gene=LIF
https://www.uniprot.org/uniprot/P15018
https://www.sigmaaldrich.com/life-science/stem-cell-biology/leukemia-inhibitory-factor-protein.html
https://pubmed.ncbi.nlm.nih.gov/10704254/
https://www.rcsb.org/pdb/gene/LIF
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The primary function of the Leukemia Inhibitory Factor is to induce terminal differentiation in myeloid leukemic cells. This terminal differentiation prevents the continued growth of leukemic cells. LIF can also promote cell differentiation and growth in different target cells and influence neural development, inflammation, cachexia, bone metabolism, and embryogenesis. Research has shown that p53-regulated Leukemia Inhibitory Factor can facilitate implantation i.e., embryo adhering to the uterus wall, in mouse models, and soon we can use them in humans. Studies also suggest recombinant human-LIF can help increase the implantation rate in unexplained infertility cases.