Isolation and amino acid sequence of a chemotactic protein, LECT/interleukin 8, from a human myeloid leukemia cell line, ML-1

Myb induced myeloid protein 1 (Mim-1) is an acetyltransferase

We have screened protein extracts from chicken blood cells for acetyltransferases. An in gel acetyltransferase assay revealed that a 32 kDa protein, which is more prevalent in whole blood when compared with erythrocyte cells, possessed an auto-acetylation activity. This protein was purified by a series of chromatographic steps, sequenced by Edman degradation and subsequently identified as Myb induced myeloid protein (Mim-1). Mim-1 has similarities to the conserved acetyltransferase motifs found in the GNAT superfamily of proteins and also contains three minimal GK acetylation motifs. These data identify Mim-1 as an acetyltransferase.

Antibody-directed superantigen-mediated T-cell killing of myeloid leukaemic cell line cells

Bacterial superantigens (SAgs) bound to MHC class II molecules on target cells are efficient activators of cytotoxic T cells expressing certain T cell receptor (TCR) Vbeta regions We described earlier that the specificity of the SAg Staphylococcus enterotoxin A (SEA) can be changed by introducing a D227A point mutation in the major MHC class II binding site and by genetically fusing the SEA mutant (SEAm) to protein A (PA). This SEAm-PA fusion protein can then be used to direct cytotoxic T cells to tumour cells coated with monoclonal antibodies (mAbs). In this communication, we tested the PA-SEAm fusion protein together with mAbs against the myeloid cell surface antigens CD13, CD15 and CD33. A SEA-reactive T cell line was used as effector cells against 10 different myeloid leukaemic cell lines. Optimal lysis of antigen positive leukaemic cells was obtained at a PA-SEAm concentration of 1 ng/ml and effector : target cell ratios of 15 : 1. No correlation between target cell sensitivity and the level of surface antigen expression could be seen. The 6 acute myeloid leukaemia (AML) cell lines tested appeared to be more sensitive than the 4 chronic myeloid leukaemia (CML) cell lines. The sensitivity of the AML cell line HL-60 could be improved further by stimulation with TNFalpha. This was accompanied by increased surface ICAM-1 expression whereas specific target molecule expression (CD13, CD33) was unchanged. This suggests that sensitivity to lysis is related to the leukaemic subtype and ICAM-1 expression but not to the tumour antigen density. Our results show that it is possible to direct cytotoxic T cells to myeloid leukaemia cells by using SAgs linked to mAbs, and encourage the construction and testing of a recombinant direct SAg-mAb fusion protein as a candidate drug for therapy of myeloid leukaemias.

Molecular cloning of human and bovine LECT2 having a neutrophil chemotactic activity and its specific expression in the liver

We previously reported the purification and amino acid sequence of a novel neutrophil chemotactic protein termed LECT2 (leukocyte cell-derived chemotaxin 2). In this paper we report molecular cloning of human and bovine LECT2 cDNAs based on the amino acid sequence of the purified protein. The deduced amino acid sequence of human LECT2 (hLECT2) shows an 86% identity to bovine LECT2 (bLECT2). The deduced primary structures of LECT2 were highly homologous to the repeated units of Mim-1 protein (myb induced myeloid protein-1). The mim-1 gene is one of the known myb target genes and is specifically expressed in normal and transformed immature granulocytes in the chicken. Northern blot analysis of normal human tissues demonstrated that the hLECT2 gene is specifically expressed in the adult and fetal livers. In addition, several human hepatoma cell lines also expressed LECT2 mRNA, suggesting that hepatic cells in the liver produce LECT2 protein.

Expression of a neutrophil chemotactic protein LECT2 in human hepatocytes revealed by immunochemical studies using polyclonal and monoclonal antibodies to a recombinant LECT2

A recombinant human neutrophil chemotactic protein LECT2 (rhLECT2) was purified as a 16-kDa protein from the culture fluids of stable transfectants derived from CHO cells (clone C1D8-1) and L929 cells (clone L2E4-1). The N-terminal amino acid sequence of the protein secreted by both clones were homologous to the previously described bovine LECT2. We produced polyclonal and monoclonal antibodies against rhLECT2 and investigated secretion of LECT2 protein in six human hepatoma cell lines, which express LECT2 mRNA, and in hepatocytes of normal human livers by a sandwich enzyme-linked immunosorbent assay and by immunostaining using the antibodies, respectively. We revealed that five of six hepatoma cell lines secreted LECT2 into culture fluids at concentrations of 30-135 ng/mg. We also demonstrated that the cytoplasm of human hepatocytes was diffusely stained, although periportal hepatocytes tended to be weakly and granularly stained by immunostaining. These results indicated that the novel protein was expressed in hepatocytes and suggested an important role of LECT2 in the cells in addition to the activation of neutrophils.

Purification and primary amino acid sequence of a novel neutrophil chemotactic factor LECT2

We purified a neutrophil chemotactic factor from a culture fluid of the PHA-activated human T-cell leukemia SKW-3 cells. The factor showed a 16-kDa basic protein by Tricin-SDS-polyacrylamide gel electorophoresis and analysis of amino acid composition. The primary amino acid sequence revealed that the chemotactic factor was significantly different from other known chemotactic factors, indicating a novel protein designated LECT2. The sequence revealed homology with the myb-induced myeloid protein-1 (Mim-1), which is expressed from gene in immature and normal granulocytes of chicken. Its biological function had not yet been identified. LECT2 and Mim-1 may be involved in the regulation of neutrophil functions in an as yet unidentified way.

Interleukins and colony stimulating factors in human myeloid leukemia cell lines

The present review has summarized the expression, production and effects of the human interleukins (IL) 1-11 and myelopoietic colony stimulating factors (CSF) in the established myeloid leukemia cell lines and in cells from patients with acute myeloid leukemia as well as the oncogene expression reported in these myeloid leukemia cell lines. The genetic dissection of leukemic myelopoiesis may provide new perspectives for the control of myeloid leukemias. Based on their expression of phenotypic markers (e.g., surface antigens, cytochemical staining, etc.), myeloid cell lines can be further subdivided into myelogenous, monocytic, erythroid and megakaryoblastic leukemia cell lines. Due to the close relationship of erythroid and megakaryoblastic progenitor cells and to the existence of a probably common precursor cell giving rise to these two different cell lineages, many megakaryoblastic cell lines express erythroid markers (e.g., expression of hemoglobin or glycophorin A) and conversely cell lines with a predominant erythroid profile might display megakaryoblastic features (e.g., platelets peroxidase or glycoproteins CD41, CD42b or CD61). The recent cloning of the specific cytokine: thrombopoietin (TPO) and its receptor generated a strong interest in these particular myeloid cell lines that are discussed in more detail in the present review. Both normal and leukemic megakaryocytopoiesis are stimulated by granulocyte-macrophage colony stimulating factor (GM-CSF), IL-3, GM-CSF/IL-3 fusion protein, IL-6, IL-11 and TPO but inhibited by IL-4, interferon-alpha (IFN-alpha) and IFN-gamma. Human megakaryoblastic leukemia cell lines have common biological features: high expression of the megakaryocytic specific antigen (CD41); high expression of early myeloid antigens (CD34, CD33 and CD13); constitutive expression of IL-6 and platelet-derived growth factor; a complex karyotype picture; expression of c-kit (the stem cell factor receptor); growth-dependency or -stimulation by IL-3 and/or GM-CSF; and in vivo tumorigenicity in mice associated with marked fibrosis. Whereas numerous chemical and biologic agents induce granulocytic and/or monocytic differentiation of myeloid leukemia cell lines, only a few agents including phorbol myristate acetate, vitamin D3, IFN-alpha, IL-6 and thrombin have been reported to induce megakaryocytic differentiation in the megakaryoblastic leukemia cells.

Molecular cloning and expression of canine interleukin 8 cDNA

Molecular cloning of canine interleukin-8 (IL-8) was performed to establish a basis for its investigation in the canine immune system. From a cDNA pool constructed from LPS-stimulated popliteal lymph node cells, canine IL-8 cDNA covering the whole coding region was amplified by polymerase chain reaction. The nucleotide sequence of a canine IL-8 clone, designated pcIL-8#38, was highly similar to those of human, rabbit and porcine IL-8, and comprised 353 bp with an open reading frame that encoded 101 amino acids. Analysis of the deduced amino acid sequence of insert DNA in pcIL-8#38 showed 76.5, 80.2, and 87.0% similarities with human, rabbit and porcine IL-8 proteins, respectively. Insert DNA of pcIL-8#38 was transferred to a mammalian expression vector, pcDL-SR alpha 296, and transfected into Cos7 cells. The supernatant of the transfectant had neutrophil chemotactic activity when it was examined by the neutrophil migration assay, suggesting that our cloned cDNA was biologically active. The cloned canine IL-8 cDNA will be useful for canine inflammatory disease and comparative immunology research.