Leukocyte differentiation antigens (LDAs) play important roles in the immune system, by serving as surface markers and participating in multiple biological activities, such as recognizing pathogens, mediating membrane signals, interacting with other cells or systems, and regulating cell differentiation and activation. Data mining is a powerful tool used to identify novel LDAs from whole genome. LRRC25 (leucine rich repeat-containing 25) was predicted to have a role in the function of myeloid cells by a large-scale "omics" data analysis. Further experimental validation showed that LRRC25 is highly expressed in primary myeloid cells, such as granulocytes and monocytes, and lowly/intermediately expressed in B cells, but not in T cells and almost all NK cells. It was down-regulated in multiple acute myeloid leukemia (AML) cell lines and bone marrow cells of AML patients and up-regulated after all-trans retinoic acid (ATRA)-mediated granulocytic differentiation in AML cell lines and acute promyelocytic leukemia (APL; AML-M3, FAB classification) cells. Localization analysis showed that LRRC25 is a type I transmembrane molecule. Although ectopic LRRC25 did not promote spontaneous differentiation of NB4 cells, knockdown of LRRC25 by siRNA or shRNA and knockout of LRRC25 by the CRISPR-Cas9 system attenuated ATRA-induced terminal granulocytic differentiation, and restoration of LRRC25 in knockout cells could rescue ATRA-induced granulocytic differentiation. Therefore, LRRC25, a potential leukocyte differentiation antigen, is a key regulator of ATRA-induced granulocytic differentiation.
Antigens, Differentiation ; immunology ; metabolism ; Cell Differentiation ; drug effects ; Cell Line, Tumor ; Granulocytes ; cytology ; drug effects ; immunology ; metabolism ; Humans ; Leukocytes ; cytology ; drug effects ; immunology ; metabolism ; Membrane Proteins ; antagonists & inhibitors ; immunology ; metabolism ; RNA, Small Interfering ; pharmacology ; Tretinoin ; pharmacology

Human 8-oxo-G-DNA glycosylase 1 (hOGG1) is a DNA glycosylase to cleave 8-oxo-7,8-dihydroguanine (8-oxo-G), a mutagenic DNA adduct formed by oxidant stresses. Here, we examined hOGG1 protein expression and repair activity to nick a DNA strand at the site of 8-oxo-G during differentiation of hematopoietic cells using HL-60 cells. Overall expression of hOGG1 protein was increased during granulocytic differentiation of HL-60 cells induced by DMSO and monocytic differentiation by vitamine D3. Greater level of hOGG1 protein was expressed in DMSO-treated cells. However, change in the DNA nicking activity was not in parallel with the change in hOGG1 protein expression, especially in PMA-treated cells. In PMA- treated cells, the level of hOGG1 protein was lowered, even though the DNA nicking activity was elevated, in a manner similar to the changes in serum- deprived HL-60 cells. These results indicate that hOGG1 expression change during differentiation of hematopoietic stem cells for adaptation to new environments. And the DNA cleaving activity may require additional factor(s) other than expressed hOGG1 protein, especially in apoptotic cell death.
Blotting, Western ; *Cell Differentiation ; Culture Media, Serum-Free/pharmacology ; DNA Glycosylases/*metabolism ; Enzyme Activation ; *Gene Expression Regulation, Enzymologic/drug effects ; Granulocytes/cytology/drug effects/metabolism ; HL-60 Cells ; Human ; Monocytes/cytology/drug effects/metabolism

A C6 beta-chemokine, CKbeta8-1, suppressed the colony formation of CD34 + cells of human cord blood (CB). Molecular mechanisms involved in CKbeta8-1-medicated suppression of colony formation of CD34 + cells are not known. To address this issue, the level of various G1/S cell cycle regulating proteins in CKbeta8-1-treated CD34 + cells were compared with those in untreated CD34 + cells. CKbeta8-1 did not significantly alter the expression of the G1/S cycle regulation proteins (cyclin D1, D3, and E), CDK inhibitor (p27and Rb), and other cell proliferation regulation protein (p53) in CB CD34 + cells. Here we describe an in vitro system in which CB CD34 + cells were committed to a multipotent progenitor lineage of colony forming units-granulocyte/macrophage (CFU-GM) by a simple combination of recombinant human (rh) GM-CSF and rhIL-3. In this culture system, we found that cyclin E protein appeared later and disappeared faster in the CKbeta8-1-treated cells than in the control cells during CFU-GM lineage development. These findings suggested that cyclin E may play a role in suppressing the colony formation of CFU-GM by CKbeta8-1.
Antigens, CD34/metabolism ; Cell Cycle Proteins/metabolism ; Cell Lineage ; Cells, Cultured ; Chemokines, CC/*pharmacology ; Cyclin E/*metabolism ; Fetal Blood/*cytology ; G1 Phase/drug effects ; Gene Expression Regulation/*drug effects ; Granulocytes/cytology/*drug effects/metabolism ; Growth Substances/pharmacology ; Humans ; Macrophages/cytology/*drug effects/metabolism ; Research Support, Non-U.S. Gov't ; Stem Cells/cytology/*drug effects/metabolism

OBJECTIVETo figure out the function of C/EBPalpha in the monocytic differentiation of HL60 cells induced by a new steroidal drug NSC67657.

METHODSThe differentiation of HL60 cells was induced by NSC67657, and the cell surface antigen CD14 expression was detected by flow cytometry. The gene and protein expressions of CCAAT enhancer binding protein alpha (C/EBPalpha) before and after the induction of cell differentiation were determined by RT-PCR and Western blot. Eukaryotic expressing vector pDsRed-ICAT was constructed and transfected into HL60 cells, and its expression was verified. The effect of C/EBPalpha overexpression in HL60 cells was assessed by MTT assay, Wright's staining and flow cytometry before and after NSC67657 transfection.

RESULTSHL60 cells could be induced into monocytes by 10 micromol/L ATRA within 5 days, and the coverage of CD14 positive cells reached 93.9% after 5 days of drug treatment. The eukaryotic expressing vector was successfully constructed, and over 90% positive clones were obtained after screening by G418 and electrotransfection. The results of proliferative analysis, chemical staining, ultrastructural observation, and CD11b detection confirmed that HL60 cells could be induced into granulocytic differentiation by overexpression of C/EBPalpha protein. Moreover, in the drug treatment group, transfected cells could not be induced into monocytic differentiation, and their granulocytic differentiation was also inhibited.

CONCLUSIONThe monocytic differentiation of HL60 cells induced by NSC67657 may not be via the regulation by C/EBPalpha protein-mediated signal transduction. However, the overexpression of CEBPalpha may inhibit the process of NSC67657-induced monocytic differentiation in HL60 cells.

CCAAT-Enhancer-Binding Protein-alpha ; genetics ; metabolism ; CD11b Antigen ; metabolism ; Cell Differentiation ; drug effects ; Genetic Vectors ; Granulocytes ; cytology ; HL-60 Cells ; Humans ; Lipopolysaccharide Receptors ; metabolism ; Mesylates ; pharmacology ; Monocytes ; cytology ; RNA, Messenger ; metabolism ; Recombinant Proteins ; genetics ; metabolism ; Signal Transduction ; Steroids ; pharmacology ; Transfection