Molecular genetic evidence for a differentiation-proliferation coupling during DMSO-induced myeloid maturation of HL-60 cells: role of the transcription elongation block in the c-myc gene

Studying Neutrophil Function in vitro: Cell Models and Environmental Factors

Neutrophils are the most abundant immune cell type in the blood and constitute the first line of defense against invading pathogens. Despite their important role in many diseases, they are challenging to study due to their short life span and the inability to cryopreserve or expand them in vitro. Thus, research into neutrophils has to rely on cells freshly isolated from peripheral blood of human donors, introducing donor-dependent variation in the experimental data. To counteract these problems, researchers tried to develop adequate cell models, such as cell lines. For those functional studies that cannot rely on cell models, a standardization of protocols regarding neutrophil purification and culturing could be a solution. In this review, we provide an overview of the most commonly used models for neutrophil function (HL-60, PLB-985, NB4, Kasumi-1 and induced pluripotent stem cells). In addition, we describe the effects of glucose concentration, pH, oxygen tension and temperature on neutrophil function.

Effects of DMSO on the Pluripotency of Cultured Mouse Embryonic Stem Cells (mESCs)

DMSO is a commonly used solvent in biological studies, as it is an amphipathic molecule soluble in both aqueous and organic media. For that reason, it is the vehicle of choice for several water-insoluble substances used in research. At the molecular and cellular level, DMSO is a hydrogen-bound disrupter, an intercellular electrical uncoupler, and a cryoprotectant, among other properties. Importantly, DMSO often has overlooked side effects. In stem cell research, the literature is scarce, but there are reports on the effect of DMSO in human embryoid body differentiation and on human pluripotent stem cell priming towards differentiation, via modulation of cell cycle. However, in mouse embryonic stem cell (mESC) culture, there is almost no available information. Taking into consideration the almost ubiquitous use of DMSO in experiments involving mESCs, we aimed to understand the effect of very low doses of DMSO (0.0001%-0.2%), usually used to introduce pharmacological inhibitors/modulators, in mESCs cultured in two different media (2i and FBS-based media). Our results show that in the E14Tg2a mESC line used in this study, even the smallest concentration of DMSO had minor effects on the total number of cells in serum-cultured mESCs. However, these effects could not be explained by alterations in cell cycle or apoptosis. Furthermore, DMSO did not affect pluripotency or differentiation potential. All things considered, and although control experiments should be carried out in each cell line that is used, it is reasonable to conclude that DMSO at the concentrations used here has a minimal effect on this particular mESC line.

Cellular adhesion gene SELP is associated with rheumatoid arthritis and displays differential allelic expression

In rheumatoid arthritis (RA), a key event is infiltration of inflammatory immune cells into the synovial lining, possibly aggravated by dysregulation of cellular adhesion molecules. Therefore, single nucleotide polymorphisms of 14 genes involved in cellular adhesion processes (CAST, ITGA4, ITGB1, ITGB2, PECAM1, PTEN, PTPN11, PTPRC, PXN, SELE, SELP, SRC, TYK2, and VCAM1) were analyzed for association with RA. Association analysis was performed consecutively in three European RA family sample groups (Nfamilies = 407). Additionally, we investigated differential allelic expression, a possible functional consequence of genetic variants. SELP (selectin P, CD62P) SNP-allele rs6136-T was associated with risk for RA in two RA family sample groups as well as in global analysis of all three groups (ptotal = 0.003). This allele was also expressed preferentially (p<10-6) with a two- fold average increase in regulated samples. Differential expression is supported by data from Genevar MuTHER (p1 = 0.004; p2 = 0.0177). Evidence for influence of rs6136 on transcription factor binding was also found in silico and in public datasets reporting in vitro data. In summary, we found SELP rs6136-T to be associated with RA and with increased expression of SELP mRNA. SELP is located on the surface of endothelial cells and crucial for recruitment, adhesion, and migration of inflammatory cells into the joint. Genetically determined increased SELP expression levels might thus be a novel additional risk factor for RA.

Insights into cancer metastasis from a clinicopathologic perspective: Epithelial-Mesenchymal Transition is not a necessary step

Epithelial-mesenchymal transition (EMT) has been implicated as the critical event initiating cancer invasion and metastasis. After disseminating through the circulation, the malignant cells have been proposed to undergo subsequent mesenchymal-epithelial transition (MET) to form secondary tumors. However, strong evidence from human tumor specimens for this paradigm is lacking. In carcinomas, cancers derived from epithelial tissues, epithelial morphology and gene expression are always retained to some degree. While mesenchymal transdifferentiation may be involved in the pathogenesis of carcinosarcomas, even in these neoplasms, as well as in germ cell tumors capable of multilineage differentiation, the mesenchymal phenotype does not facilitate metastatic progression. Indeed, most cancers invade and travel through lymphatic and blood vessels via cohesive epithelial migration, rather than going through the EMT-MET sequence. EMT gene expression is also consistently associated with high histologic grade and while the transcription factors, Snail, Slug and Twist have traditionally been thought of as inducers of EMT, under certain conditions, they also mediate dedifferentiation and maintenance of the stem cell state. In various malignancies, including basal-like breast cancer and colorectal cancer, the genetically unstable, undifferentiated phenotype predicts early metastatic spread and poor prognosis. This article discusses some of the controversies surrounding differentiation and metastasis from a clinicopathologic perspective and presents evidence that the epithelial phenotype is maintained throughout the process of cancer metastasis.

Differential allelic expression of IL13 and CSF2 genes associated with asthma

An important area of genetic research is the identification of functional mechanisms in polymorphisms associated with diseases. A highly relevant functional mechanism is the influence of polymorphisms on gene expression levels (differential allelic expression, DAE). The coding single nucleotide polymorphisms (SNPs) CSF2^rs25882 and IL13^rs20541 have been associated with asthma. In this work, we investigated whether the mRNA expression levels of CSF2 or IL13 were correlated with these SNPs. Samples were analyzed by mass spectrometry-based quantification of gene expression. Both SNPs influenced gene expression levels (CSF2^rs25882: p_overall = 0.008 and p_{DAE samples} = 0.00006; IL13^rs20541: p_overall = 0.059 and p_{DAE samples} = 0.036). For CSF2, the expression level was increased by 27.4% (95% CI: 18.5%–35.4%) in samples with significant DAE in the presence of one copy of risk variant CSF2^rs25882-T. The average expression level of IL13 was increased by 29.8% (95% CI: 3.1%–63.4%) in samples with significant DAE in the presence of one copy of risk variant IL13^rs20541-A. Enhanced expression of CSF2 could stimulate macrophages and neutrophils during inflammation and may be related to the etiology of asthma. For IL-13, higher expression could enhance the functional activity of the asthma-associated isoform. Overall, the analysis of DAE provides an efficient approach for identifying possible functional mechanisms that link disease-associated variants with altered gene expression levels.

Acyclic retinoid activates retinoic acid receptor β and induces transcriptional activation of p21CIP1 in HepG2 human hepatoma cells

Acyclic retinoid (ACR), a novel synthetic retinoid, has recently been demonstrated by us to inhibit the in vitro growth of human hepatoma cells, and this effect was associated with decreased expression of cell cycle-related molecules. These results, taken together with previous in vitro and clinical studies with ACR, suggest that this agent may be useful in the chemoprevention and therapy of hepatoma and possibly other human malignancies. In the present study, we further examined the molecular effects of ACR on the HepG2 human hepatoma cell line, focusing on the expression of nuclear retinoid receptors and the cell cycle inhibitor protein p21CIP1. Reverse transcription-PCR assays and Western blot analyses indicated that these cells express retinoic acid receptors (RARs) α, β, and γ, retinoid X receptors (RXRs) α and β, and peroxisome proliferator-activated receptors (PPAR) γ mRNA. Treatment with ACR caused a rapid induction within 3 h of RARβ mRNA and the related protein, but there was no significant change in the levels of the mRNA or proteins for RARs α and γ, RXRs α and β, and PPARγ. There was also a rapid increase in p21CIP1 mRNA and protein in HepG2 cells treated with ACR, and this induction occurred via a p53-independent mechanism. In transient transfection reporter assays, we cotransfected the retinoic acid response element-chloramphenicol acetyltransferase (CAT) reporter gene into HepG2 cells together with a RARβ expression vector. RARβ expression markedly stimulated CAT activity (up to about 4-fold) after the addition of ACR. However, CAT activity in the presence of ACR was only about 2-fold higher than that in the absence of ACR, when cells were cotransfected with RARs α and γ or RXRα. These findings suggest that the growth inhibitory effects of ACR are mediated at least in part through RARβ and that both RARβ and p21CIP1 play critical roles in the molecular mechanisms of growth inhibition induced by ACR.

IMPAN cells: a pancreatic model for differentiation into endocrine cells

It is currently believed that pancreatic progenitor or stem cells exist in the ductal cell population and that these cells have the ability to be grown and differentiated into endocrine cells for the treatment of diabetes. In this study, we have examined this potential in IMPAN (Immortalized Pancreatic) cells. These cells are derived from the adult H-2K(b)-tsA58 transgenic mouse. We observed an increased mRNA expression of insulin, proendocrine gene neurogenin 3, and beta-cell transcription factor Pdx1 when the cells were grown on bovine collagen I gels. The induction profile of these three genes was similar under the tested conditions. No glucagon or other endocrine-specific transcription factors were detectable. Application of GIP, GLP-1 derivative NN2211, and activin-A/betacellulin to IMPAN cells in normal culture did not lead to endocrine differentiation. In conclusion, it appears that the ability of IMPAN cells to mature to endocrine cells is limited.

Inhibitors of lipoxygenase metabolism exert synergistic effects with retinoic acid on differentiation of human leukemia HL-60 cells

The interaction between drugs suppressing the production of arachidonic acid metabolites and inducers of granulocytic differentiation, i.e., all-trans retinoic acid and dimethyl sulphoxide (DMSO) was investigated using the human myeloid leukemia HL-60 cell line. The experiments were designed as a complete factorial combination of treatments and used chemiluminescence as a marker of cell oxidative burst (level of differentiation). It was clearly demonstrated that two structurally different inhibitors of 5-lipoxygenase metabolism, i.e., 3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-di methyl propanoic acid (MK-886) and esculetin, significantly potentiated the HL-60 cell differentiation induced by retinoic acid or DMSO. Detailed mathematical evaluation of the results revealed the synergistic character of the interaction. The most significant effects were achieved with a combination of 5-lipoxygenase inhibitors and low doses of retinoic acid. These results were confirmed by analysis of cell morphology and expression of cell surface antigen CD11b after treatment of the cells with selected concentrations of agents. In contrast to those on differentiation, no additional effects of MK-886 or esculetin on cell proliferation (cell number and cell cycle parameters) and apoptosis were observed. An inhibitor of cyclooxygenases, indomethacin, affected neither cell proliferation nor differentiation of cells. The results implied that either modulation of 5-lipoxygenase metabolism or a certain type of imbalance in arachidonic acid metabolism could modulate the effects of retinoic acid or DMSO on myeloid cell differentiation.

C/EBPalpha regulation of the growth-arrest-associated gene gadd45

CCAAT/enhancer-binding protein alpha (C/EBPalpha) is expressed in postmitotic, differentiated adipocytes and is required for adipose conversion of 3T3-L1 cells in culture. Temporal misexpression of C/EBPalpha in undifferentiated adipoblasts leads to mitotic growth arrest. We report here that growth arrest- and DNA damage-inducible gene 45 (gadd45) is preferentially expressed in differentiated 3T3-L1 adipocytes similar to phenotype-associated genes. Furthermore, C/EBPalpha transactivates a reporter plasmid containing 1.5 kb of the gadd45 promoter region. The proto-oncogene myc, which inhibits adipocyte differentiation, abrogates C/EBPalpha activation of gadd45. gadd45 is known to be a target of the tumor suppressor p53 in a G1 checkpoint activated by DNA damage. Immunoprecipitation of radiolabeled proteins with conformation-specific antibodies revealed that wild-type p53 is expressed throughout 3T3-L1 adipocyte development, including the postmitotic period characterized by the accumulation of gadd45 and C/EBPalpha. A stable 3T3-L1 subline was engineered to express a dominant negative p53, human p53(143ala). The p53(143ala) subline differentiated to adipocytes and showed appropriate developmental expression of gadd45. These findings suggest that postmitotic growth arrest is coupled to adipocyte differentiation via C/EBPalpha stimulation of growth arrest-associated and phenotype-associated genes.

p145 expression during the cell cycle in HL-60 cell line and normal human lymphocytes: effects of camptothecin, vinblastine, cycloheximide, actinomycin D, retinoic acid and DMSO

Bivariate flow cytometric analysis of nucleolar antigen p145 was performed on quiescent and phytohemagglutinin-stimulated human lymphocytes and on a promyelocytic cell line (HL-60). Data were acquired on a FACScan flow cytometer and analyzed using LYSYS II. Quiescent lymphocytes did not express p145. PHA-stimulated proliferating lymphocytes expressed p145 maximally after 48 h, similarly to HL-60 cells in exponential growth. Antigen expression in G1 was notably heterogeneous in both cell types. The ratio of p145/DNA was highest in early S and decreased during mid and late S and remained low in G2M. p145 expression was lowest in M-phase cells treated for 6 h with vinblastine. Cycloheximide and actinomycin D had similar effects on p145 in HL-60 cells: expression of p145 gradually decreased from 1 to 6 h incubation in all phases of the cell cycle. Camptothecin did not decrease p145 expression and apoptotic cells from CAM-treated cultures still expressed p145. Retinoic acid and DMSO induced differentiation in HL-60 cells, and as this process progressed, p145 levels gradually fell until they approached isotype antibody control levels at 9 and 6 days, respectively. However, after 5 days treatment with 2 nM retinoic acid apoptotic cells appeared which still expressed p145. The data on drug treatment suggest that p145 exists in undifferentiated and proliferating cells and may not be a specific marker for malignancy, but may prove useful as a monitor of chemotherapeutic effects in cancer treatment.