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Tyro 3 (Sky), Axl, and Mer receptors are members of the family of tyrosine kinases and Gas6 is their ligand molecule. In some types of cancer, upregulation of Axl/Gas6 indicated a worse prognosis, but an opposite situation was observed in renal “cell” carcinoma. This contradiction may suggest that Axl/Gas6 pathway varies depending on the type of cancer. The objective of this study is to investigate TAM receptors on surfaces of mononuclear cells in patients with B-Cell chronic lymphocytic leukemia (B-Cell-CLL).B-Cell-CLL patients (grade 0–1, according to the classification of RAI), who were not on a drug treatment, were recruited in this study (n= 20; 9 female, 11 male). Their ages were 44 to 74 (mean: 63), and the control group consisted of 13 healthy volunteers (5 female, 8 male), whose age range is 20–89 (mean: 36). Mononuclear cells were isolated by density gradient centrifugation, and then surface TAM receptors were detected by flow cytometry. Mononuclear cell were stained with the primary antibodies against Tyro3, Axl and Mer.The percentage of the surface TAM receptors on mononuclear cells from the patient group (25–75% interquartile range): Tyro 3= 25.50 (4.2– 45.62); Axl= 17/55 (5.57– 36.32), and Mer= 19.90 (1.92– 37.55). In the control group the following values were obtained: Tyro 3= 2.60 (1.35–3.25); Axl= 0.9 (0.4–2.6), and Mer= 2.50 (0.35–3.65). The percentage of three of them was significantly higher in the B-Cell-CLL group than those in the control group (P<0.01).In conclusion, this preliminary study showed that TAM receptors on surfaces of mononuclear cells are higher in patients with B-Cell-CLL patients than the control group. Gas6/TAM signaling may play a potential role in the pathogenesis of B Cell-CLL. Further studies are required to elucidate the actual role of Gas6/TAM signaling in B-Cell-CLL. Gas6/TAM signaling might be a new strategic goal for the treatment of B-Cell-CLL.No relevant conflicts of interest to declare.

Abstract 4588