Tomáš Loja

Nestin expression in the cell lines derived from glioblastoma multiforme

BackgroundNestin is a protein belonging to class VI of intermediate filaments that is produced in stem/progenitor cells in the mammalian CNS during development and is consecutively replaced by other intermediate filament proteins (neurofilaments, GFAP). Down-regulated nestin may be re-expressed in the adult organism under certain pathological conditions (brain injury, ischemia, inflammation, neoplastic transformation). Our work focused on a detailed study of the nestin cytoskeleton in cell lines derived from glioblastoma multiforme, because re-expression of nestin together with down-regulation of GFAP has been previously reported in this type of brain tumor.MethodsTwo cell lines were derived from the tumor tissue of patients treated for glioblastoma multiforme. Nestin and other cytoskeletal proteins were visualized using imunocytochemical methods: indirect immunofluorescence and immunogold-labelling.ResultsUsing epifluorescence and confocal microscopy, we described the morphology of nestin-positive intermediate filaments in glioblastoma cells of both primary cultures and the derived cell lines, as well as the reorganization of nestin during mitosis. Our most important result came through transmission electron microscopy and provided clear evidence that nestin is present in the cell nucleus.ConclusionDetailed information concerning the pattern of the nestin cytoskeleton in glioblastoma cell lines and especially the demonstration of nestin in the nucleus represent an important background for further studies of nestin re-expression in relationship to tumor malignancy and invasive potential.

Nestin expression in osteosarcomas and derivation of nestin/CD133 positive osteosarcoma cell lines

BackgroundNestin was originally identified as a class VI intermediate filament protein that is expressed in stem cells and progenitor cells in the mammalian CNS during development. This protein is replaced in the adult organism by other intermediate filament proteins; however, nestin may be re-expressed under certain pathological conditions such as ischemia, inflammation, brain injury, and neoplastic transformation. Nestin has been detected in many kinds of tumors, especially in tumors derived from the CNS. Co-expression of nestin and the CD133 surface molecule is considered to be a marker for cancer stem cells in neurogenic tumors. Our work was aimed at a detailed study of nestin expression in osteosarcomas and osteosarcoma-derived cell lines.MethodsUsing immunodetection methods, we examined nestin in tumor tissue samples from 18 patients with osteosarcomas. We also successfully established permanent cell lines from the tumor tissue of 4 patients and immunodetection of nestin and CD133 was performed on these cell lines.ResultsNestin-positive tumor cells were immunohistochemically detected in all of the examined osteosarcomas, but the proportion of these cells that were positively stained as well as the intensity of staining varied. Nestin-positive cells were rarely observed in 2 tumor samples, and the remaining 16 tumor samples showed various nestin expression patterns ranging from very sporadic occurrence to an overwhelming proportion of cells with strong positive staining. Three of the established osteosarcoma cell lines were demonstrated to be nestin-positive, and only one cell line showed no expression of nestin; this finding corresponds with the rare occurrence of nestin-positive cells in the respective tumor sample. Moreover, three of these osteosarcoma cell lines were undoubtedly proven to be Nes+/CD133+.ConclusionOur results represent the first evidence of nestin expression in osteosarcomas and suggest the possible occurrence of cells with a stem-like phenotype in these tumors.

Analysis of nuclear nestin localization in cell lines derived from neurogenic tumors

Nestin is a class VI intermediate filament protein expressed in the cytoplasm of stem and progenitor cells in the mammalian CNS during development. In adults, nestin is present only in a small subset of cells and tissues, including the subventricular zone of the adult mammalian brain, where neurogenesis occurs. Nestin expression has also been detected under such pathological conditions as ischemia, inflammation, and brain injury, as well as in various types of human solid tumors and their corresponding cell lines. Furthermore, nestin was recently found in the nuclei of glioblastoma, neuroblastoma, and angiosarcoma cells and it was proved to interact directly with the nuclear DNA in neuroblastoma cells. Here, we perform the first study of the intracellular distribution of nestin in cell lines derived from neurogenic tumors. Using immunodetection methods, we examined nestin expression in tumor-derived cell lines obtained from 11 patients with neuroblastoma, medulloblastoma, or glioblastoma multiforme. Besides its standard cytoplasmic localization, nestin was present in the nuclei of two neuroblastoma cell lines and one medulloblastoma cell line. Nestin was only present in the nuclei of cells with diffuse cytoplasmic staining for this protein, and the proportion of cells positive for nestin in nuclei, as well as the intensity of staining, varied. The presence of nestin in the nuclei was confirmed by both transmission electron microscopy and Western blotting. Our results indicate that the presence of nestin in the nuclei of tumor cells is not very rare, especially under in vitro conditions.

Co-expression of cancer stem cell markers corresponds to a pro-tumorigenic expression profile in pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies. Its dismal prognosis is often attributed to the presence of cancer stem cells (CSCs) that have been identified in PDAC using various markers. However, the co-expression of all of these markers has not yet been evaluated. Furthermore, studies that compare the expression levels of CSC markers in PDAC tumor samples and in cell lines derived directly from those tumors are lacking. Here, we analyzed the expression of putative CSC markers—CD24, CD44, epithelial cell adhesion molecule (EpCAM), CD133, and nestin—by immunofluorescence, flow cytometry and quantitative PCR in 3 PDAC-derived cell lines and by immunohistochemistry in 3 corresponding tumor samples. We showed high expression of the examined CSC markers among all of the cell lines and tumor samples, with the exception of CD24 and CD44, which were enriched under in vitro conditions compared with tumor tissues. The proportions of cells positive for the remaining markers were comparable to those detected in the corresponding tumors. Co-expression analysis using flow cytometry revealed that CD24+/CD44+/EpCAM+/CD133+ cells represented a significant population of the cells (range, 43 to 72%) among the cell lines. The highest proportion of CD24+/CD44+/EpCAM+/CD133+ cells was detected in the cell line derived from the tumor of a patient with the shortest survival. Using gene expression profiling, we further identified the specific pro-tumorigenic expression profile of this cell line compared with the profiles of the other two cell lines. Together, CD24+/CD44+/EpCAM+/CD133+ cells are present in PDAC cell lines derived from primary tumors, and their increased proportion corresponds with a pro-tumorigenic gene expression profile.

Evaluation of the Stability of DNA i-Motifs in the Nuclei of Living Mammalian Cells

Abstract C‐rich DNA has the capacity to form a tetra‐stranded structure known as an i‐motif. The i‐motifs within genomic DNA have been proposed to contribute to the regulation of DNA transcription. However, direct experimental evidence for the existence of these structures in vivo has been missing. Whether i‐motif structures form in complex environment of living cells is not currently known. Herein, using state‐of‐the‐art in‐cell NMR spectroscopy, we evaluate the stabilities of i‐motif structures in the complex cellular environment. We show that i‐motifs formed from naturally occurring C‐rich sequences in the human genome are stable and persist in the nuclei of living human cells. Our data show that i‐motif stabilities in vivo are generally distinct from those in vitro. Our results are the first to interlink the stability of DNA i‐motifs in vitro with their stability in vivo and provide essential information for the design and development of i‐motif‐based DNA biosensors for intracellular applications.

Cancer stem cell markers in pediatric sarcomas: Sox2 is associated with tumorigenicity in immunodeficient mice

The three most frequent pediatric sarcomas, i.e., Ewing’s sarcoma, osteosarcoma, and rhabdomyosarcoma, were examined in this study: three cell lines derived from three primary tumor samples were analyzed from each of these tumor types. Detailed comparative analysis of the expression of three putative cancer stem cell markers related to sarcomas—ABCG2, CD133, and nestin—was performed on both primary tumor tissues and corresponding cell lines. The obtained results showed that the frequency of ABCG2-positive and CD133-positive cells was predominantly increased in the respective cell lines but that the high levels of nestin expression were reduced in both osteosarcomas and rhabdomyosarcomas under in vitro conditions. These findings suggest the selection advantage of cells expressing ABCG2 or CD133, but the functional tests in NOD/SCID gamma mice did not confirm the tumorigenic potential of cells harboring this phenotype. Subsequent analysis of the expression of common stem cell markers revealed an evident relationship between the expression of the transcription factor Sox2 and the tumorigenicity of the cell lines in immunodeficient mice: the Sox2 levels were highest in the two cell lines that were demonstrated as tumorigenic. Furthermore, Sox2-positive cells were found in the respective primary tumors and all xenograft tumors showed apparent accumulation of these cells. All of these findings support our conclusion that regardless of the expression of ABCG2, CD133 and nestin, only cells displaying increased Sox2 expression are directly involved in tumor initiation and growth; therefore, these cells fit the definition of the cancer stem cell phenotype.

Detecting minimal residual disease in patients with chronic lymphocytic leukemia using 8-color flow cytometry protocol in routine hematological practice.

Minimal residual disease (MRD) detection has become increasingly important for the assessment of therapy response in chronic lymphocytic leukemia (CLL). However, current MRD analysis methods, both molecular genetic and flow cytometric, are time‐consuming and require experienced laboratory staff.

Impaired mitophagy in Fanconi anemia is dependent on mitochondrial fission

Fanconi anemia (FA) is a rare genetic disorder associated with bone-marrow failure, genome instability and cancer predisposition. Recently, we and others have demonstrated dysfunctional mitochondria with morphological alterations in FA cells accompanied by high reactive oxygen species (ROS) levels. Mitochondrial morphology is regulated by continuous fusion and fission events and the misbalance between these two is often accompanied by autophagy. Here, we provide evidence of impaired autophagy in FA. We demonstrate that FA cells have increased number of autophagic (presumably mitophagic) events and accumulate dysfunctional mitochondria due to an impaired ability to degrade them. Moreover, mitochondrial fission accompanied by oxidative stress (OS) is a prerequisite condition for mitophagy in FA and blocking this pathway may release autophagic machinery to clear dysfunctional mitochondria.

Influence of pulsed electromagnetic and pulsed vector magnetic potential field on the growth of tumor cells

Abstract Aims and Background: Tumor diseases cause 20% of deaths in Europe and they are the second most common cause of death and morbidity after cardiovascular diseases. Thus, tumor cells are target of many therapeutic strategies and tumor research is focused on searching more efficient and specific drugs as well as new therapeutic approaches. One of the areas of tumor research is an issue of external fields. In our work, we tested influence of a pulsed electromagnetic field (PEMF) and a hypothetic field of the pulsed vector magnetic potential (PVMP) on the growth of tumor cells; and further the possible growth inhibition effect of the PVMP. Methods: Both unipolar and bipolar PEMF fields of 5 mT and PVMP fields of 0 mT at frequencies of 15 Hz, 125 Hz and 625 Hz were tested on cancer cell lines derived from various types of tumors: CEM/C2 (acute lymphoblastic leukemia), SU-DHL-4 (B-cell lymphoma), COLO-320DM (colorectal adenocarcinoma), MDA-BM-468 (breast adenocarcinoma), and ZR-75-1 (ductal carcinoma). Cell morphology was observed, proliferation activity using WST assay was measured and simultaneous proportion of live, early apoptotic and dead cells was detected using flow cytometry. Results: A PEMF of 125 Hz and 625 Hz for 24 h–48 h increased proliferation activity in the 2 types of cancer cell lines used, i.e. COLO-320DM and ZR-75-1. In contrast, any of employed methods did not confirm a significant inhibitory effect of hypothetic PVMP field on tumor cells.

Ability to downregulate the level of cyclin-dependent kinase inhibitor p27(Kip1) after DNA damage is retained in chronic lymphocytic leukemia cells with functional ATM/p53 signaling pathway.

The activity of the key DNA-damage response (DDR) kinases, ATR and ATM, is largely compromised in chronic lymphocytic leukemia (CLL) cells. While noncycling CLL cells lack ATR protein expression,[1] ATM is commonly targeted for inactivation by genetic abnormalities of the ATM gene.[2] It has been shown that checkpoint pathways, which operate in cycling somatic cells and target Cdk2 kinase activity, are to some extent activated in arrested CLL cells after DNA damage as well;[3] however, the impact of these pathways is questionable, as it could be hampered by predominantly cytoplasmic localization of Cdk2 in CLL cells.[4] Nevertheless, DDR plays a key role in sensitivity of CLL to chemotherapy. Another stress-response kinase, p38 MAP kinase (p38MAPK), was shown to promote CLL cells survival.[5] In multiple cell types, p38MAPK activates different cell cycle checkpoints (mainly through regulation of cyclindependent kinase (Cdk) inhibitors p21Cip1 and p27Kip1), and also ATM/ATR-dependent G2/M checkpoint signaling through MAPKAP kinase-2 activity.[6] While relationship between ATM/p53 and p21Cip1 expression in CLL was studied,[7] the association of ATM kinase activity with the levels of p27Kip1 after DNA damage has not been elucidated in CLL cells.