Membrane and intracellular platelet-activating factor receptor expression in leukemic blasts of patients with acute myeloid and lymphoid leukemia

Overexpression of miR-17 predicts adverse prognosis and disease recurrence for acute myeloid leukemia

Background

The clinical significance of miR-17 in patients with acute myeloid leukemia (AML) remains unknown.

Methods

Real-time quantitative reverse transcription-polymerase chain reaction (qPCR) was performed to detect the miR-17 expression in 115 de novo AML patients, 31 patients at complete remission (CR) time, 8 patients at relapse time and 30 normal controls.

Results

MiR-17 was upregulated in de novo AML compared with normal controls. Patients with high expression of miR-17 had less CEBPA double mutation, less favorable ELN-risk and lower CR rate. The level of miR-17 was significantly decreased at CR phase and was returned to primary level even higher when in relapse phase. In addition, Cox regression analysis revealed that miR-17 expression retained independent prognostic significance for overall survival (OS). Moreover, the gene-expression profile analysis of miR-17 in AML obtained from TCGA database was involved in multiple biological functions and signal pathways. Among the differential expressed genes (DEGs), we identified FGL2, PLAUR, SLC2A3, GPR65, CTSS, TLR7, S1PR3, OGFRL1, LILRB1, IL17RA, SIGLEC10, SLAMF7, PLXDC2, HPSE, TCF7 and MYCL as potential direct targets of miR-17 according to in silico analysis.

Conclusions

High expression of miR-17 in de novo AML patients pointed to dismal clinical outcome and disease recurrence, which could serve as novel prognostic biomarker for AML patients.

Lipid mediators and human leukemic blasts

Some of the most potent inflammatory mediators share a lipid origin. They regulate a wide spectrum of cellular processes including cell proliferation and apoptosis. However, the precise roles and ways (if any) in which these compounds impact the growth and apoptosis of leukemic blasts remain incompletely resolved. In spite of this, significant advances have been recently made. Here we briefly review the current knowledge about the production of lipid mediators (prostaglandins, leukotrienes, platelet-activating factor) by leukemic blasts, the enzymatic activities (phospholipase A₂, cyclooxygenases, lipoxygenases) involved in their productions and their effects (through specific membrane bound receptors) on the growth, and apoptosis of leukemic blasts.

Platelet-activating factor changes in phospholipid extracts from the plasma, peripheral blood mononuclear cells and bone marrow mononuclear cells of patients with acute leukemia--a 31P MRS in vitro study

The aim of this investigation was to evaluate the changes in PAF concentrations in the plasma, PBMC and BMMC of patients with acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML). The plasma was from 23 healthy volunteers (HV) and 44 patients with AL (16 ALL, 28 AML). The PBMC were from 15 HV and 55 patients with AL (18 ALL, 37 AML), and the BMMC from 40 patients with AL (11 ALL, 29 AML). Methanol-chloroform phospholipid extraction from 60 x 10(6) cells (PBMC or BMMC) was performed according to a modified version of Folch's method. (31)P MRS data was obtained on an AMX 300 Bruker spectrometer (7.05 T). The PAF concentration in the plasma of the patients with ALL or AML was lower than that for the healthy volunteers. The PAF concentration in the plasma of the patients with ALL did not differ significantly from that of the patients with AML. In the case of both the PBMC and BMMC, the PAF concentration was significantly diminished in patients with ALL relative to the concentration for those with AML and for the healthy volunteers. No differences were observed in the PAF concentrations for the AML patients and the healthy volunteers.

Functional platelet-activating factor receptors in immature forms of leukemic blasts

Platelet-activating factor (PAF) is a phospholipid mediator with potent immunoregulatory activities on mature leukocytes. PAF modulates leukocyte cytosolic Ca2+ concentration ([Ca2+]i) through a Gq mediated pathway. We highlight, for the first time, Gq transcripts, PAF receptor (PAF-R) transcripts and protein in blast cells of acute myeloid (AML) and lymphoid (ALL) leukemia patients. PAF stimulated [Ca2+]i in leukemic blast cells; PAF effects being prevented by a specific PAF-R antagonist. In conclusion, functional PAF-R are present in blast cells of patients with acute leukemia; a result that could be of physiologic importance regarding the important effect of PAF on leukocytes maturation and functions.

Receptor for platelet-activating factor (PAF) is not detectable by flow cytometry on the surface of myeloid leukemic cells

Flow cytometry was applied to test for platelet-activating-factor receptor (PAF-R) presence on the membranes of acute myeloid leukemia (AML) cells. We have used six human AML cell lines and freshly taken density gradient separated blasts from the bone marrow of ten AML patients covering the majority of French-American-British (FAB) subtypes. Additionally, we have used one histiocytic lymphoma cell line and mature human granulocytes/monocytes as controls. Our results indicate lack of membrane PAF-R on AML of all FAB subtypes tested. This was particularly true for the more mature and differentiated subtypes M4 and M5, including monocytic cell elements, and the promyelocytic M3 AML. In contrast, membrane PAF-R could be easily detected in a histiocytic lymphoma cell line and mature granulocytes/monocytes from peripheral blood used as positive controls. In conclusion, this observation precludes the use of membrane PAF-R as an immunophenotypic marker for AML classification or detection of minimal residual disease.

Platelet-activating factor and normal or leukaemic haematopoiesis

Platelet-activating factor (PAF), a phospholipid mediator with a wide range of actions on mature leukocytes, acts directly during early human haematopoiesis by affecting the growth of haematopoietic progenitors and indirectly, by modulating cytokine synthesis by bone marrow stromal cells. At this time, its role during leukaemic diseases remains speculative. The lack of membrane PAF receptor (PAF-R) on leukaemic blasts suggest that this receptor represents a marker of mature cells and its membrane induction a consequence of cell maturation. While the couple PAF/PAF-R has been largely studied using B cell lines, few results are available using B cells of patients with haematopoietic malignancies casting some doubts concerning the potential role (if any) of this molecule during leukaemic diseases.