TIGIT in Patients With Chronic Myeloid Leukemia

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Chronic myeloid leukemia (CML) is also known as chronic myelogenous leukemia. It's a type of cancer that starts in certain blood-forming cells of the bone marrow. In CML, a genetic change takes place in an early (immature) version of myeloid cells that make red blood cells, platelets, and most types...

Chronic myeloid leukemia (CML) is also known as chronic myelogenous leukemia. It's a type of cancer that starts in certain blood-forming cells of the bone marrow. In CML, a genetic change takes place in an early (immature) version of myeloid cells that make red blood cells, platelets, and most types of white blood cells (except lymphocytes). This change forms an abnormal gene called BCR-ABL, which turns the cell into a CML cell. The leukemia cells grow and divide, building up in the bone marrow and spilling over into the blood. In time, the cells can also settle in other parts of the body, including the spleen. CML is a fairly slow growing leukemia, but it can change into a fast-growing acute leukemia that's hard to treat. CML occurs mostly in adults, but very rarely it occurs in children, too. In general, their treatment is the same as for adults. Chronic myeloid leukemia (CML) is characterized by the expression of the BCR/ABL1 fusion gene and the presence of the Philadelphia chromosome (Ph). The product of this fusion gene is a protein with deregulated tyrosine kinase activity, resulting in a malignant clonal disorder of the hematopoietic stem cells in the bone marrow (BM) and the accumulation of immature myeloid cells in peripheral blood (PB). The use of tyrosine kinase inhibitors (TKIs) leads to a complete remission rate reaching 83%; however, mutation in the ABL kinase domain results in certain treatment failure. Furthermore, long-lasting side effects of treatment and the cost of TKIs remain a problem Therefore, the development of new TKI agents and combination therapies is urgently needed for CML patients . Natural killer (NK) cells serve an important role in eliminating malignant cells. The cytotoxic effects of NK cells were first identified against leukemia cells, and it is now hypothesized that they may have a critical role in leukemia therapy. The cellular functions of NK cells are mediated by their cell surface receptors, which recognize ligands on cancer cells. The role of NK cells is specifically regulated by the activating or inhibitory killer cell immunoglobulin like receptors (KIRs) on their surface, which bind to the human leukocyte antigen (HLA) class I ligands present on the target cells. There is an abundance of evidence that NK cells can exhibit potent antitumor activity against CML, However, disease-associated mechanisms often inhibit the proper functions of endogenous NK cells, leading to inadequate tumor control and risk for disease progression. As it is well known, the function of NK cells is precisely regulated by inhibitory and activating receptors. Recently, T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine -based inhibitory motif (ITIM domain) (TIGIT) has been identified as a novel NK inhibitory receptor that can lead to NK cell exhaustion and dysfunction. Targeting TIGIT is believed to restore 4 key function :Restoration of NK function, Depletion of T reg, Increase antigen-specific CD8 memory response and Induction of new antigen-specific CD8 T cells. TIGIT was first identified as an inhibitory receptor expressed by activated CD4 Tcells , tregs and NK cells. However , direct evidence supporting a clinical role for TIGIT in AML.

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