Hana Šváchová

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.

Myeloma stem cell concepts, heterogeneity and plasticity of multiple myeloma

Multiple myeloma (MM) is a haematological malignancy characterized by the accumulation of clonal plasma cells (PCs) in the bone marrow (BM). Although novel therapeutic strategies have prolonged survival of patients, the disease remains difficult to treat with a high risk of relapse. The failure of therapy is thought to be associated with a persistent population of the so‐called MM stem cells or myeloma initiating cells (MIC) that exhibit tumour‐initiating potential, self‐renewal and resistance to chemotherapy. However, the population responsible for the origin and sustainability of tumour mass has not been clearly characterized so far. This review summarizes current myeloma stem cell concepts and suggests that high phenotypic and intra‐clonal heterogeneity, together with plasticity potential of MM might be other contributing factors explaining discrepancies among particular concepts and contributing to the treatment failure.

Levels of angiogenic factors in patients with multiple myeloma correlate with treatment response

Angiogenesis plays a significant role in the pathogenesis of multiple myeloma (MM). We have measured concentrations of angiogenesis activators, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor, and hepatocyte growth factor (HGF), and inhibitors, including endostatin, thrombospondin-1 (TSP-1), and angiostatin in the peripheral and bone marrow blood of MM patients at diagnosis and after high-dose chemotherapy. We have analyzed 96 patients with secretory MM. Serial measurements of angiogenesis factors/inhibitors were analyzed in the plasma by subgroups based on the best treatment response. Concentrations of angiogenic factors were determined in the peripheral blood and bone marrow plasma. There were significant decreases of VEGF and HGF levels and a significant increase in TSP-1 concentrations in the bone marrow plasma of patients who achieved complete or very good partial response in contrast to those who had partial or no response. VEGF and HGF levels decrease but those of TSP-1 increase after successful treatment for MM, indicating a reduction in the rate of angiogenesis.

Stem cell marker nestin is expressed in plasma cells of multiple myeloma patients.

Nestin is considered to be a characteristic marker of multipotent proliferative precursors found in some embryonic and fetal tissues. Its expression might be a suitable diagnostic and prognostic indicator of malignancy and a potential marker of cancer stem cells in solid tumors. Unexpectedly, nestin protein was detected in mature CD138(+)CD38(+) plasma cells of multiple myeloma patients and statistical analysis confirmed significant differences between myeloma patients and control group without hematological malignancy. Our results represent the first evidence of nestin expression in multiple myeloma. Further studies are required to elucidate the role of this protein in multiple myeloma.

Bone marrow plasma cell separation - validation of separation algorithm

Monoclonal gammopathy is characterized by the presence of monoclonal immunoglobulin which is produced by a specifi c clone of terminally differentiated long-living plasma cells (PC) in the bone marrow. More detailed understanding of this clone at the genomic and proteomic level as well as its comparison with the population of normal PC is possible only after the clone is separated from other BM cells.

Nestin expression throughout multistep pathogenesis of multiple myeloma

The stem cell marker nestin (NES) is found in dividing cells of developing and regenerating tissues. Upon terminal differentiation, NES expression is diminished but may be re‐expressed following injury or in cancer. Surprisingly, we recently confirmed NES as a tumour‐specific marker for mature CD138+38+ plasma cells (PC) in multiple myeloma (MM). The present study analysed NES expression throughout the spectrum of MM developmental stages, starting with individuals with no haematological malignancy, through monoclonal gammopathy of undetermined significance (MGUS) and MM to plasma cell leukaemia (PCL) and MM cell lines. NES was analysed in bone marrow PC of 163 MM, four PCL and nine MGUS patients, 10 individuals with no haematological malignancy and 6 myeloma cell lines (OPM‐2, RPMI‐8226, MOLP‐8, U‐266, EJM, NCI‐H929) by flow cytometry and/or real‐time polymerase chain reaction or immunochemistry. We observed a tendency of increased NES expression in parallel with disease progression. NES was evaluated as a reliable marker for accurate discrimination between MM patients and the control group. High NES levels were strongly associated with the presence of 1q21 gain. For the first time, NES was demonstrated to predict worse response to conventional therapy/novel agents. These results suggest that NES might become a useful clinical parameter with an important role in MM pathogenesis.

Heterogeneity and Plasticity of Multiple Myeloma

Modern molecular and cytogenetic approaches have furthered progress in our understanding of MM biology and have led to the development of targeted therapy that has improved management of this incurable disease. Novel agents such as bortezomib, lenalidomide or thalidomide, have increased median survival rates and improved prospects for MM patients resistant to conventional therapy [1, 2]. Despite these therapeutic advances, MM remains a very difficult disease to treat still accompanied by the threat of repeated relapses with a fatal ending. These observations indicate that at least some of the MM cells are not targeted efficiently by current drug therapies. The existence of such persistent populations, called myeloma stem cells (MSC) or myeloma-initiating cells (MIC) has been suspected for more than two decades. However, the cells of origin remain elusive [3-9]. Timeline of growing knowledge about putative MSC is displayed in Figure 1. Discrepancies among myeloma stem cell concepts have arisen in parallel with the high phenotypic heterogeneity of clonal PCs that might be another factor contributing to the failure of therapies and identification of the population responsible for relapse. Myeloma PCs strongly depends on the supportive role of the bone marrow (BM) microenvironment (MEV) – it is a source of essential growth factors, supports survival and dissemination of pathological PCs [10-14]. Furthermore, hypoxic conditions of tumor microenvironments support tumor progression by inducing angiogenesis, maintaining the malignant phenotype and stimulating osteoclastogenesis [15-18]. There is growing evidence that signals from pathological microenvironments can (reversibly) alter the phenotype of PCs. Such plasticity of PCs might result in obvious heterogeneity of MM and generate inconsistencies among myeloma stem cell concepts.