Leukemia inhibitory factor, or LIF, is an

interleukin 6 Interleukin 6 (IL-6) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the ''IL6'' gene. In addition, osteoblasts secrete IL-6 to stimulate osteoclast formation. Smooth ...

class

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

that affects

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

growth by inhibiting differentiation. When LIF levels drop, the cells differentiate.

Function

LIF derives its name from its ability to induce the terminal differentiation of myeloid leukemic cells, thus preventing their continued growth. Other properties attributed to the cytokine include: the growth promotion and cell differentiation of different types of target cells, influence on

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

cachexia Cachexia () is a complex syndrome associated with an underlying illness, causing ongoing muscle loss that is not entirely reversed with nutritional supplementation. A range of diseases can cause cachexia, most commonly cancer, congestive heart ...

, neural development, embryogenesis and

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

p53 p53, also known as Tumor protein P53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory protein that is often mutated in human cancers. The p53 proteins (originally thought to be, and often s ...

regulated LIF has been shown to facilitate implantation in the mouse model and possibly in humans. It has been suggested that recombinant human LIF might help to improve the implantation rate in women with unexplained infertility.

Binding/activation

LIF binds to the specific LIF

receptor Receptor may refer to: * Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ...

( LIFR-α) which forms a heterodimer with a specific subunit common to all members of that family of receptors, the

GP130 Glycoprotein 130 (also known as gp130, IL6ST, IL6R-beta or CD130) is a transmembrane protein which is the founding member of the class of all cytokine receptors. It forms one subunit of the type I cytokine receptor within the IL-6 receptor famil ...

signal transducing subunit. This leads to activation of the

JAK Jak may refer to: Places * Ják, a village in Hungary People * Jak Alnwick (born 1993), English football goalkeeper * Jak Jones (born 1993), Welsh professional snooker player * Raymond Jackson ("JAK") (1927–1997), UK cartoonist * Jak Airport ( ...

STAT STAT, Stat. , or stat may refer to: * Stat (system call), a Unix system call that returns file attributes of an inode * ''Stat'' (TV series), an American sitcom that aired in 1991 * Stat (website), a health-oriented news website * STAT protein, a ...

(Janus kinase/ signal transducer and activator of

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

) and

MAPK A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of protein kinase that is specific to the amino acids serine and threonine (i.e., a serine/threonine-specific protein kinase). MAPKs are involved in directing cellular responses to ...

(

mitogen A mitogen is a small bioactive protein or peptide that induces a cell to begin cell division, or enhances the rate of division (mitosis). Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. The mechanism of action of a ...

activated

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

kinase) cascades.

Expression

LIF is normally expressed in the

trophectoderm The trophoblast (from Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the ...

of the developing embryo, with its receptor LIFR expressed throughout the inner cell mass. As embryonic stem cells are derived from the inner cell mass at the blastocyst stage, removing them from the inner cell mass also removes their source of LIF. Recombinant LIF has been produced in plants by InVitria.

Use in stem cell culture

LIF is often added to stem cell culture media as an alternative to feeder cell culture, due to the limitation that feeder cells present by only producing LIF on their cell surfaces. Feeder cells lacking the LIF

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

do not effectively support stem cells. LIF promotes self-renewal by recruiting signal transducer and activator of transcription 3 (

Stat3 Signal transducer and activator of transcription 3 (STAT3) is a transcription factor which in humans is encoded by the ''STAT3'' gene. It is a member of the STAT protein family. Function STAT3 is a member of the STAT protein family. In respons ...

). Stat3 is recruited to the activated LIF receptor and phosphorylated by

Janus kinase Janus kinase (JAK) is a family of intracellular, non-receptor tyrosine kinases that transduce cytokine-mediated signals via the JAK-STAT pathway. They were initially named "just another kinase" 1 and 2 (since they were just two of many discoveries ...

. It bears noting that LIF and Stat3 are not sufficient to inhibit stem cell differentiation, as cells will differentiate upon removal of serum. During the reversibility phase of differentiation from naive pluripotency, it is possible to revert cells back to naive pluripotency through the addition of LIF. Removal of LIF pushes stem cells toward differentiation, however genetic manipulation of embryonic stem cells allows for LIF independent growth, notably overexpression of the gene Nanog. LIF is typically added to stem cell culture medium to reduce spontaneous differentiation.

References

External links