Background: The programmed death 1 (PD-1) receptor pathway is responsible for the negative regulation of both T and B lymphocytes upon activation of these cells. There is growing evidence that chronic lymphocytic leukemia (CLL) cells exploit the PD-1 ligand (PD-L1) to resist antitumor immune reactions and maintain their survival by shaping their own microenvironment. Methods: We used a quantitative RT-PCR method to analyze PD-L1 gene expression in bone marrow and peripheral blood mononuclear cells, representing the proliferation and accumulation compartments of CLL. Results: PD-L1 expression was found to be significantly higher in 112 CLL patients than in controls. Levels of PD-L1 expression in bone marrow and peripheral blood were comparable and showed a positive correlation. Furthermore, expression of PD-L1 strongly correlated with expression of PD-1 receptor in mononuclear cells from the same compartment, and was not affected by incubation with immunomodulatory drug thalidomide. Conclusion: PD-L1 expression is shared between CLL cells localized in distinct disease compartments, demonstrating that PD-1/PD-L1 a universal target for therapy.

In 103 hearts with various forms of cardiac muscle hypertrophy the following parameters were estimated: diameter, length, volume, density and number of myocytes, and density of myocyte nuclei. The values of all histometric parameters correlated well with left ventricular (LV) weight up to 350 g. In heavier hearts these parameters remained approximately of the same magnitude. The number of myocytes was significantly higher in hearts with LV weight above 250 g. The influence on LV weight of age, coronary artery diameters, degree of atherosclerosis, weight and percent of fibrous tissue was also evaluated. On the basis of a linear discriminant function, hearts were divided into three classes: (1) LV weight < or = 250 g (absence of hyperplasia, hypertrophy only); (2) LV weight 251-350 g (hypertrophy+signs of hyperplasia); (3) LV weight > 350 g (marked signs of hyperplasia). The percent of fibrosis increased proportionally to LV weight. Where LV weight was above 250 g there was a subsequent increase in the mean percent of fibrosis (approx. 26%). This phenomenon (plateau of percent fibrosis) is the result of an increased number of myocytes (myocyte hyperplasia). We suggest that, independent of aetiology, in all hearts above 350 g (patients with congestive heart failure) hyperplasia phenomenon exists.

Mutations of the nucleophosmin-1 (NPM1) gene in cytogenetically normal (CN) acute myeloid leukemia (AML) identify a group of patients with more favorable prognosis. NPM1 encodes three main alternatively spliced isoforms R1(B23.1), R2(B23.2), and R3(B23.3). The expression of splice variants R1, R2 and R3 were higher in AML patients compared to normal cells of healthy volunteers (HVs), although RNA-seq analysis revealed enhanced R2 expression also in less differentiated cells of HVs as well as in AML cells. The variant R2, which lacks exons 11 and 12 coding for the nucleolar localization domain, might behave similar to the mutant form of NPM1 (NPM1mut). In accordance, in CN-AML high R2 expression was associated with favorable impact on outcome. Moreover, functional studies showed nucleolar localization of the eGFP-NPM1 wildtype and cytoplasmic localization of the eGFP-NPM1 mut protein. While the eGFP-NPM1 R2 splice variant localized predominantly in the nucleoplasm, we also could detect cytoplasmic expression for the R2 variant. These results support a unique biological consequence of R2 overexpression and in part explain our clinical observation, where that high R2 variant expression was associated with a better prognosis in CN-AML patients.

Programmed death-1 (PD-1) is a negative receptor expressed on lymphocytes including malignant B cells in chronic lymphocytic leukemia (CLL). In this work, we found that patients with CLL had a higher expression of PD-1 transcript (PDCD1) than healthy volunteers (p < 0.0001). PDCD1 expression was comparable between CLL cells from accumulation (peripheral blood) and proliferation (bone marrow) disease compartments. In blood samples of patients with mutated IGHV genes PDCD1 expression was higher than with unmutated IGHV (p = 0.0299). We demonstrated that phosphorylation of SYK and LYN, key B-cell receptor signaling kinases, was independent of PD-1 expression in patients with CLL, while ZAP-70 phosphorylation in negative tyrosine residue 292 showed strong inverse correlation (r = - 0.8, p = 0.0019). No associations between five single nucleotide polymorphisms of PDCD1, their expressions and susceptibility to CLL were found. In conclusion, PD-1 might be an independent, universal marker of CLL cells and a part of their activated phenotype, and subsequently might modulate the function of ZAP-70.

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