About FLT3 Ligand:
FLT3 (Fms-related tyrosine kinase 3 ligands) is a protein which has been human encoded by the FLT3LG gene. It is a hematopoietic four helical bundle cytokine. FLT3 is structurally homologous to SCF (stem cell factor) and CSF-1 (colony stimulating factor 1). Along with other growth factors, FLT3 ligand stimulates the differentiation of blood cell progenitors.
Other members of the same family include Steel factor, which is also known as mast cell growth factor, stem cell factor, and kit ligand, and colony stimulating factor 1. Each of these proteins functions by connecting to and activating the unique tyrosine kinase receptors. It should be noted that expression of the FLT3 receptor is restricted to hematopoietic cells to the primitive progenitor cells. FLT3 ligand is similar to Steel factor as both proteins stimulate the proliferation of progenitor or stem cells. However, neither of these cells have more proliferative activity of their own, but each can connect with a vast range of colony stimulating factors, as well as interleukins to help stimulate the process of proliferation.
One huge difference between these two factors is the effect that they have on mast cells. Steel factor is able to stimulate mast cells, whereas FLT3 is not able to do so. While both of these proteins use early hematopoietic cells, activities suggest that they are not useless, with boing being needed for normal, healthy hematopoiesis. Due to this, there are various clinical settings where FLT3 ligand can prove rather useful.
FLT3 is a type of receptor tyrosine kinase (RTK) which is expressed by immature progenitor cells. The FLT3 ligand is a soluble protein (also known as a transmembrane) which is expressed by a range of cells, including hematopoietic and marrow stromal cells. In combination with various other growth factors, the ligand is able to stimulate proliferation and marrow stromal cells, in combination with other growth factors, the ligand is also able to stimulate proliferation and development of new stem cells, as well as myeloid and lymphoid progenitor cells, dendritic cells, and also, natural killer cells. When the receptor is activated, it leads to tyrosine phosphorylation of different key adaptor proteins, all of which are known to be part of the signal transduction pathways that play a key part in proliferation, cell survival, and other cellular processes in hematopoietic cells.
FLT3 is not only of interest in relation to physiological processes of hematopoietic cells but also in regard to pathological aspects, such as leukemogenesis and the diagnosis, prognosis and therapy for leukemia. By activating mutations of receptors, it has been recognized that FLT3 is the most common genetic abnormality in acute myeloid leukemia, occurring in around 30% of adult cases. Usually, leukemia patients with the FLT3 mutations tend to have a poorer prognosis than patients without it, which is why FLT3 is an important target for therapy, and one that is constantly being researched and trialed, in the hope that the research conducted will one day make the reality of beating leukemia a more likely one in human medicine.