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The P2X7 nucleotide receptor is an adenosine 5′-triphosphate (ATP) -gated ion channel, which is widely expressed in cells of hematopoietic origin and functions as a non-selective cation channel permeable to Na+, Ca2+, etc upon stimulation. Here, we investigated P2X7 expression in 11 human hematopoietic cell lines, representing different lineages, as well as bone marrow mononuclear cells (BMMC) samples from 87 leukemia and 10 myelodysplastic syndrome (MDS) patients. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) and flow cytometry results showed that both P2X7 mRNA and protein were detected in eight cell lines with a non-lineage-specific manner. Samples from 69 leukemia and 9 MDS patients were P2X7 positive at mRNA level. Moreover, both positive rates and relative expression levels were significantly higher in acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myelogenous leukemia (CML), and MDS groups than that in normal donor group. The expression levels varied among AML subtypes with higher levels being observed in M4, M5, and M6 groups but not in M1 or M2 group. Furthermore, after one course of standard induction therapies, the remission rate in high P2X7 expression group was lower than that in either P2X7 negative group or low P2X7 expression group. Cytoplasmic free calcium increase was detected in five of eight P2X7+ cell lines as well as P2X7+ normal donor and patient samples tested, but not in three Epstein–Barr virus (EBV) positive cell lines (J6-1, Namalwa, and LCL-H) in Locke’s solution upon stimulation by extracellular ATP or the more potent and specific agonist, 2′,3′-O-(4-benzoyl)benzoyl-ATP (BzATP). The possible mechanisms causing the loss of P2X7 function were discussed. [Copyright &y& Elsevier]

The importance of IL-18, although clearly established in solid tumors, has not been fully elucidated in human hematopoietic neoplasms. Here we examined the mRNA and protein for IL-18 in eight human hematopoietic cell lines representing different lineages and neoplasms including leukemia, lymphoma and others. Our results revealed that IL-18 mRNA was expressed in these cells and that the corresponding protein was found in the cytoplasm. Seven of eight cell lines were also found to express two subunits of the IL-18 receptor (IL-18R) at varied levels. Furthermore, 29 out of 51 leukemia patients tested were observed to express IL-18R with 18/29 (62%) co-expression of both receptor and ligand. By blocking the IL-18 loop using specific antisense oligodeoxynucleotide (ASON) for IL-18 mRNA or anti-human IL-18R monoclonal antibody (McAbR), we were not able to demonstrate a marked inhibition on the most leukemic cell lines growth. Moreover, the potential proliferation in vitro of primary AML cells co-expressing IL-18 and its receptor was not significantly enhanced by recombinant human IL-18, suggesting that IL-18 is not apparently implicated in the proliferation of the leukemia cells via an autocrine loop. Additionally, we also found the effective modulating effect of M-CSF, IFN-α and TNF-α on IL-18R expression, implying an important in vivo effect of cytokines on IL-18-induced reaction. Moreover, the modulation of IL-18R expression was possibly irrelevant to IFN-γ secretion induced by these cytokines. [Copyright &y& Elsevier]