Background: Expression of mRNA thrombopoietin receptor (MPL) is detected in various tissues, but peripheral blood cells mature thrombopoietin receptor found in the platelet and mononuclear cells only (http://www.genecards.org/). It has previously been shown MPL mRNA regulates mobilization of bone marrow stem cells (Xiao N. et al., Blood, 2015) and activation of Th2-lymphocytes (Takyar S. et al., J Exp Med, 2013). MPL mRNA expression in bone marrow is associated with the progression of AML (Wetzler M. et al., J Clin Oncol, 1997) and increase of it expression in bone marrow megakaryocytes in Ph- negative myeloproliferative neoplasm (MPN) more pronounced in patients with primary myelofibrosis (PMF) (Bock O. et al., J Pathol, 2004) has been described. MPL mRNA level in venous blood leukocytes in patients with hematologic malignancies is unknown. Aims: Evaluate the MPL mRNA expression in venous blood leukocytes in patients with certain hematologic malignancies Methods: Real-time PCR was performed to detect of MPL mRNA transcripts levels in white blood cells 21 healthy volunteers, 28 patients with chronic myeloid neoplasm (MPN: PMF - 2, PV- 21 and ET - 5), 27 patients with chronic lymphocytic leukemia (CLL), 48 patients with chronic myeloid leukemia (CML), 3 patients with acute lymphocytic leukemia (ALL) and 8 patients with acute myeloid leukemia (AML). Venous blood were collected in tube with RNAse inhibitor. Total RNA was isolated using "Ribo-zol-D" (Aplisens). 10 µg of total RNA were transcribed using "Reverta-L" (Aplisens). PCR was optimized for the thermocycler iQ5 (Bio-Rad) under following condition: 40 cycle of 95 C for 15 sec and 60 C for 60 sec, reaction mixture contained 1X KCl PCR buffer, 2 mM MgCl2, 400 uM dNTP, 300 uM forward and reverse primers, 200 uM probe and 1 unit Taq-polymerase. The results were calculated utilizing the delta Ct method in the software package of "R". The threshold cycles (Ct) MPL gene and housekeeping gene GAPD determined using Cy0 method. The results was normalization with GAPDH reference gene and are presented as median and quartiles (25% and 75%). Results: mRNA MPL expression level in leukocytes venous blood decreased among PMF (0.024, 0.03) > ET (0.013; 0.003-0.016) = PV (0.010; 0.007-0.018) > CML (0.002; 0.0008-0.005) > CLL (0.0005; 0.0002-0.0016) = AML (0.0021; 0.0006-0.0027) = ALL (0.0018; 0.0009-0.0027). MPL mRNA expression level was no correlated with any blood cells count. Summary and Conclusions: Our study support the hypothesis of the independence certain functions mRNA MPL and functions mature thrombopoetin receptor in blood cells. Measurement of mRNA MPL can used as an additional diagnostic marker for the differentiation of MPN and evaluate progress in hematologic malignancies. Figure Expression levels mRNA MPL gene in explored patients groups Figure. Expression levels mRNA MPL gene in explored patients groups Disclosures No relevant conflicts of interest to declare.