Structural characterization of erythroid and megakaryocytic differentiation in Friend erythroleukemia cells

Expression of prion protein in mouse erythroid progenitors and differentiating murine erythroleukemia cells

Prion diseases have been observed to deregulate the transcription of erythroid genes, and prion protein knockout mice have demonstrated a diminished response to experimental anemia. To investigate the role of the cellular prion protein (PrP(C)) in erythropoiesis, we studied the protein's expression on mouse erythroid precursors in vivo and utilized an in vitro model of the erythroid differentiation of murine erythroleukemia cells (MEL) to evaluate the effect of silencing PrP(C) through RNA interference.The expression of PrP(C) and selected differentiation markers was analyzed by quantitative multicolor flow cytometry, western blot analysis and quantitative RT-PCR. The silencing of PrP(C) expression in MEL cells was achieved by expression of shRNAmir from an integrated retroviral vector genome. The initial upregulation of PrP(C) expression in differentiating erythroid precursors was detected both in vivo and in vitro, suggesting PrP(C)'s importance to the early stages of differentiation. The upregulation was highest on early erythroblasts (16200±3700 PrP(C) / cell) and was followed by the gradual decrease of PrP(C) level with the precursor's maturation reaching 470±230 PrP(C) / cell on most mature CD71(-)Ter119(+) small precursors. Interestingly, the downregulation of PrP(C) protein with maturation of MEL cells was not accompanied by the decrease of PrP mRNA. The stable expression of anti-Prnp shRNAmir in MEL cells led to the efficient (>80%) silencing of PrP(C) levels. Cell growth, viability, hemoglobin production and the transcription of selected differentiation markers were not affected by the downregulation of PrP(C).In conclusion, the regulation of PrP(C) expression in differentiating MEL cells mimics the pattern detected on mouse erythroid precursors in vivo. Decrease of PrP(C) protein expression during MEL cell maturation is not regulated on transcriptional level. The efficient silencing of PrP(C) levels, despite not affecting MEL cell differentiation, enables created MEL lines to be used for studies of PrP(C) cellular function.

P19INK4D links endomitotic arrest and megakaryocyte maturation and is regulated by AML-1

The molecular mechanisms that regulate megakaryocyte (MK) ploidization are poorly understood. Using MK differentiation from primary human CD34(+) cells, we observed that p19(INK4D) expression was increased both at the mRNA and protein levels during ploidization. p19(INK4D) knockdown led to a moderate increase (31.7% +/- 5%) in the mean ploidy of MKs suggesting a role of p19(INK4D) in the endomitotic arrest. This increase in ploidy was associated with a decrease in the more mature MK population (CD41(high)CD42(high)) at day 9 of culture, which was related to a delay in differentiation. Inversely, p19(INK4D) overexpression in CD34(+) cells resulted in a decrease in mean ploidy level associated with an increase in CD41 and CD42 expression in each ploidy class. Confirming these in vitro results, bone marrow MKs from p19(INK4D) KO mice exhibited an increase in mean ploidy level from 18.7N (+/- 0.58N) to 52.7N (+/- 12.3N). Chromatin immunoprecipitation assays performed in human MKs revealed that AML-1 binds in vivo the p19(INK4D) promoter. Moreover, AML-1 inhibition led to the p19(INK4D) down-regulation in human MKs. These results may explain the molecular link at the transcriptional level between the arrest of endomitosis and the acceleration of MK differentiation.

Spectral imaging perspective on cytomics

BACKGROUND

Cytomics involves the analysis of cellular morphology and molecular phenotypes, with reference to tissue architecture and to additional metadata. To this end, a variety of imaging and nonimaging technologies need to be integrated. Spectral imaging is proposed as a tool that can simplify and enrich the extraction of morphological and molecular information. Simple-to-use instrumentation is available that mounts on standard microscopes and can generate spectral image datasets with excellent spatial and spectral resolution; these can be exploited by sophisticated analysis tools.

METHODS

This report focuses on brightfield microscopy-based approaches. Cytological and histological samples were stained using nonspecific standard stains (Giemsa; hematoxylin and eosin (H&E)) or immunohistochemical (IHC) techniques employing three chromogens plus a hematoxylin counterstain. The samples were imaged using the Nuance system, a commercially available, liquid-crystal tunable-filter-based multispectral imaging platform. The resulting data sets were analyzed using spectral unmixing algorithms and/or learn-by-example classification tools.

RESULTS

Spectral unmixing of Giemsa-stained guinea-pig blood films readily classified the major blood elements. Machine-learning classifiers were also successful at the same task, as well in distinguishing normal from malignant regions in a colon-cancer example, and in delineating regions of inflammation in an H&E-stained kidney sample. In an example of a multiplexed ICH sample, brown, red, and blue chromogens were isolated into separate images without crosstalk or interference from the (also blue) hematoxylin counterstain.

CONCLUSION

Cytomics requires both accurate architectural segmentation as well as multiplexed molecular imaging to associate molecular phenotypes with relevant cellular and tissue compartments. Multispectral imaging can assist in both these tasks, and conveys new utility to brightfield-based microscopy approaches.

JAK-STAT signaling involved in phorbol 12-myristate 13-acetate- and dimethyl sulfoxide-induced 2'-5' oligoadenylate synthetase expression in human HL-60 leukemia cells

The JAK-STAT signal transduction cascade participates in various cellular processes, including immune response, cell replication, differentiation and oncogenesis. Here, we report that this cascade is induced in two human myeloid HL-60 leukemia cell variants by the granulocyte differentiation inducer dimethyl sulfoxide (DMSO) and macrophage differentiation inducer phorbol 12-myristate 13-acetate (PMA). DMSO and PMA also induced the expression and catalytic activity of 2'-5' oligoadenylate synthetase (2-5A synthetase), a known interferon (IFN) inducible enzyme. The HL-60 cell variants included HL-205, which is susceptible to DMSO- and PMA-induced differentiation, and HL-525, which is susceptible to DMSO- but not to PMA-induced differentiation. Treatment of HL-205 and HL-525 cells with DMSO and HL-205 cells with PMA-induced JAK1 phosphorylation, JAK1/STAT1 association, formation of STAT1-STAT2 heterodimers, and the binding of the active IFN stimulating growth factor 3 (ISGF3) to the IFN-stimulated response element (ISRE) fragment isolated from the 2-5A synthetase promoter. These events were either reduced or absent in the resistant HL-525 cells treated with PMA. Taken together, our data implicate the above signaling cascade in DMSO- and PMA-induced 2-5A synthetase expression and catalytic activity in the HL-60 cell system.

Feasibility study of the use of similarity maps in the evaluation of oncological dynamic positron emission tomography images

A preliminary study is presented on the potential role of similarity mapping (SM) in the evaluation of oncological dynamic 18F-fluorodeoxyglucose positron emission tomography studies, mainly in lesion localisation and detectability. Similarity maps were calculated using previously described (correlation coefficient (COR) and normalised correlation coefficient (NCOR)) and newly introduced similarity measures (sum of squares coefficient (SSQ), squared sum coefficient (SQS), sum of cubes coefficient (SC) and cubed sum coefficient (CS)). The results were evaluated using simulated and clinical data. The study revealed that the best-suited similarity measure for such applications was the CS similarity coefficient, which provided the best parametric images, delineating structures of interest and supporting the visual interpretation of data sets. It was shown that SM and standardised uptake value (SUV) images had comparable diagnostic performance, although SM was able to offer additional time-related information in a single image. For the case of colorectal recurrences (17 cases), the measured contrast values for the CS and SUV images were 2.36 +/- 0.47 and 4.12 +/- 0.42, respectively, whereas, for three cases of giant cell tumours, these values were 11.6 +/- 2.1 and 11.9 +/- 1.8, respectively.

Mechanisms involved in the induced differentiation of leukemia cells

Despite the remarkable progress achieved in the treatment of leukemias over the last several years, many problems (multidrug resistance [MDR], cellular heterogeneity, heterogeneous molecular abnormalities, karyotypic instability, and lack of selective action of antineoplastic agents) still remain. The recent progress in tumor molecular biology has revealed that leukemias are likely to arise from disruption of differentiation of early hematopoietic progenitors that fail to give birth to cell lineage restricted phenotypes. Evidence supporting such mechanisms has been derived from studying bone marrow leukemiogenesis and analyzing differentiation of leukemic cell lines in culture that serve as models of erythroleukemic (murine erythroleukemia [MEL] and human leukemia [K562] cells) and myeloid (human promyelocytic leukemia [HL-60] cells) cell maturation. This paper reviews the current concepts of differentiation, the chemical/pharmacological inducing agents developed thus far, and the mechanisms involved in initiation of leukemic cell differentiation. Emphasis was given on commitment and the cell lineage transcriptional factors as key regulators of terminal differentiation as well as on membrane-mediated events and signaling pathways involved in hematopoietic cell differentiation. The developmental program of MEL cells was presented in considerable depth. It is quite remarkable that the erythrocytic maturation of these cells is orchestrated into specific subprograms and gene expression patterns, suggesting that leukemic cell differentiation represents a highly coordinated set of events that lead to irreversible growth arrest and expression of cell lineage restricted phenotypes. In MEL and other leukemic cells, differentiation appears to be accompanied by differentiation-dependent apoptosis (DDA), an event that can be exploited chemotherapeutically. The mechanisms by which the chemical inducers promote differentiation of leukemic cells have been discussed.

Growth arrest and apoptosis of human hepatocellular carcinoma cells induced by hexamethylene bisacetamide

AIM: To investigate the cellular effects of hybrid polar compound hexamethylene bisacetamide (HMBA) on the growth and apoptosis of human hepatocellular carcinoma cells and to provide the molecular mechanism for potential application of HMBA in the treatment of liver cancer.

METHODS: Effects of HMBA on the growth of human hepatocellular carcinoma SMMC-7721 cells were assayed by MTT chronometry. Apoptosis induced by HMBA was detected by phase-contrast microscopy, flow cytometry, propidium iodide staining and immunocytochemical analysis.

RESULTS: The growth of SMMC-7721 cells was significantly inhibited by HMBA, and the growth inhibitory rate was 51.1%, 62.6%, 68.7% and 73.9% respectively after treatment with 5.0, 7.5, 10.0 and 12.5 mmol/L of HMBA. In the cells treated with 10 mmol/L of HMBA for 72 h, the population of cells at sub-G₁ phase significantly increased, and the apoptotic bodies and condensed nuclei were detected. Moreover, treatment of SMMC-7721 cells with 10 mmol/L of HMBA down-regulated the expression of Bcl-2 anti-apoptotic protein, while slightly up-regulated the level of pro-apoptotic protein Bax.

CONCLUSION: Treatment with 10.0 mmol/L of HMBA can significantly inhibit the growth and induce apoptosis of human hepatocellular carcinoma SMMC-7721 cells by decreasing the ratio of Bcl-2 to Bax.

Specificity of photosensitizer accumulation in undifferentiated versus differentiated colon carcinoma cells

The relationship between tumor cell differentiation and photosensitizer accumulation used in PDT is poorly defined. In the present work, specific cell differentiation of colon carcinoma CT26 cells induced by sodium butyrate was manifested by morphological changes, proliferation and protein expression and was correlated with the accumulation of endogenous and exogenous photosensitizes. Reduced accumulation of the endogenous protoporphyrin IX and the exogenous hypericin and MC540 was detected in differentiated cells. In contrast, a differentiation-dependent increase was measured with TPPS4, TMPyP, the pheophorbides (C5, C6, C12), HypS4 and helianthrone. In conclusion, PpIX, Hypericin and MC540 show specific binding and accumulation in poorly differentiated tumors, giving these tumors tissue-specific advantage in photo-diagnostic PDT applications.

Effects of tachyplesin on the regulation of cell cycle in human hepatocarcinoma SMMC-7721 cells

AIM

To investigate the effects of tachyplesin on the cell cycle regulation in human hepatcarcinoma cells.

METHODS

Effects of tachyplesin on the cell cycle in human hepatocarcinoma SMMC-7721 cells were assayed with flow cytometry. The protein levels of p53, p16, cyclin D1 and CDK4 were assayed by immunocytochemistry. The mRNA levels of p21(WAF1/CIP1) and c-myc genes were examined with in situ hybridization assay.

RESULTS

After tachyplesin treatment, the cell cycle arrested at G0/G1 phase, the protein levels of mutant p53, cyclin D1 and CDK4 and the mRNA level of c-myc gene were decreased, whereas the levels of p16 protein and p21(WAF1/CIP1) mRNA increased.

CONCLUSION

Tachyplesin might arrest the cell at G0/G1 phase by upregulating the levels of p16 protein and p21(WAF1/CIP1) mRNA and downregulating the levels of mutant p53, cyclin D1 and CDK4 proteins and c-myc mRNA, and induce the differentiation of human hepatocacinoma cells.