Combination of SCF, IL-6, IL-3, and GM-CSF increases the mitotic index in short term bone marrow cultures from acute promyelocytic leukemia (APL) patients

Regulation of glioblastoma progression by cord blood stem cells is mediated by downregulation of cyclin D1

Background

The normal progression of the cell cycle requires sequential expression of cyclins. Rapid induction of cyclin D1 and its associated binding with cyclin-dependent kinases, in the presence or absence of mitogenic signals, often is considered a rate-limiting step during cell cycle progression through the G₁ phase.

Methodology/Principal Findings

In the present study, human umbilical cord blood stem cells (hUCBSC) in co-cultures with glioblastoma cells (U251 and 5310) not only induced G₀-G₁ phase arrest, but also reduced the number of cells at S and G₂-M phases of cell cycle. Cell cycle regulatory proteins showed decreased expression levels upon treatment with hUCBSC as revealed by Western and FACS analyses. Inhibition of cyclin D1 activity by hUCBSC treatment is sufficient to abolish the expression levels of Cdk 4, Cdk 6, cyclin B1, β-Catenin levels. Our immuno precipitation experiments present evidence that, treatment of glioma cells with hUCBSC leads to the arrest of cell-cycle progression through inactivation of both cyclin D1/Cdk 4 and cyclin D1/Cdk 6 complexes. It is observed that hUCBSC, when co-cultured with glioma cells, caused an increased G₀-G₁ phase despite the reduction of G₀-G₁ regulatory proteins cyclin D1 and Cdk 4. We found that this reduction of G₀-G₁ regulatory proteins, cyclin D1 and Cdk 4 may be in part compensated by the expression of cyclin E1, when co-cultured with hUCBSC. Co-localization experiments under in vivo conditions in nude mice brain xenografts with cyclin D1 and CD81 antibodies demonstrated, decreased expression of cyclin D1 in the presence of hUCBSC.

Conclusions/Significance

This paper elucidates a model to regulate glioma cell cycle progression in which hUCBSC acts to control cyclin D1 induction and in concert its partner kinases, Cdk 4 and Cdk 6 by mediating cell cycle arrest at G₀-G₁ phase.

Induction of apoptosis in glioma cells requires cell-to-cell contact with human umbilical cord blood stem cells

We have previously demonstrated the multipotent nature of human umbilical cord blood stem cells (hUCB). In this study, we have attempted to show the use of hUCB in glioma therapy. We used hUCB enriched in CD44 and CD133 cells for our studies and observed that glioma cells co-cultured with hUCB undergo apoptosis. To prove the role of cell-to-cell contact in the induction of apoptotic events, we used a modified 0.22 microm Boyden's chamber where the upper surface was used to culture glioma cells (SNB19 or U87) or xenografts (4910 or 5310) and the lower surface to culture hUCB. TUNEL assay was carried out to determine the degree of apoptotic induction and we observed that glioma or xenograft cells co-cultured with hUCB had a higher number of TUNEL-positive characteristics (63+/-6%) compared to the controls. Further, we co-cultured glioma cells labeled with lipophilic green fluorescent dye and hUCB labeled with lipophilic red fluorescent dye. FACS analysis of cells collected from the upper and lower surfaces revealed that glioma cells had taken up red fluorescent dye from the stem cells (70+/-3%) when compared to glioma cells co-cultured with fibroblast cells (15+/-4%). The apoptotic events in the glioma and xenograft cells co-cultured with hUCB were also confirmed by Western blot analysis for the cleavage of PARP and activation of caspase 8. In addition, elevated levels of CHK-2 levels and downregulation of MAP2K1 were observed in glioma cells co-cultured with hUCB indicating the DNA damage and decrease in cell survival. Nude mice, intracranially implanted with luciferase-expressing U87 cells followed by implantation of hUCB or human fibroblast cells showed retardation of intracranial tumors in hUCB-implanted mice. Taken together, these results demonstrate that hUCB have therapeutic potential with possible clinical implications.

Upregulation of PTEN in glioma cells by cord blood mesenchymal stem cells inhibits migration via downregulation of the PI3K/Akt pathway

Background

PTEN (phosphatase and tensin homologue deleted on chromosome ten) is a tumor suppressor gene implicated in a wide variety of human cancers, including glioblastoma. PTEN is a major negative regulator of the PI3K/Akt signaling pathway. Most human gliomas show high levels of activated Akt, whereas less than half of these tumors carry PTEN mutations or homozygous deletions. The unique ability of mesenchymal stem cells to track down tumor cells makes them as potential therapeutic agents. Based on this capability, new therapeutic approaches have been developed using mesenchymal stem cells to cure glioblastoma. However, molecular mechanisms of interactions between glioma cells and stem cells are still unknown.

Methodology/Principal Findings

In order to study the mechanisms by which migration of glioma cells can be inhibited by the upregulation of the PTEN gene, we studied two glioma cell lines (SNB19 and U251) and two glioma xenograft cell lines (4910 and 5310) alone and in co-culture with human umbilical cord blood-derived mesenchymal stem cells (hUCBSC). Co-cultures of glioma cells showed increased expression of PTEN as evaluated by immunofluorescence and immunoblotting assays. Upregulation of PTEN gene is correlated with the downregulation of many genes including Akt, JUN, MAPK14, PDK2, PI3K, PTK2, RAS and RAF1 as revealed by cDNA microarray analysis. These results have been confirmed by reverse-transcription based PCR analysis of PTEN and Akt genes. Upregulation of PTEN resulted in the inhibition of migration capability of glioma cells under in vitro conditions. Also, wound healing capability of glioma cells was significantly inhibited in co-culture with hUCBSC. Under in vivo conditions, intracranial tumor growth was inhibited by hUCBSC in nude mice. Further, hUCBSC upregulated PTEN and decreased the levels of XIAP and Akt, which are responsible for the inhibition of tumor growth in the mouse brain.

Conclusions/Significance

Our studies indicated that upregulation of PTEN by hUCBSC in glioma cells and in the nude mice tumors downregulated Akt and PI3K signaling pathway molecules. This resulted in the inhibition of migration as well as wound healing property of the glioma cells. Taken together, our results suggest hUCBSC as a therapeutic agent in treating malignant gliomas.

Cytotoxicity of human umbilical cord blood-derived mesenchymal stem cells against human malignant glioma cells

BACKGROUND

Mesenchymal stem cells (MSCs) represent a potential useful source for cell-based glioma therapies because these cells evidence both orthodox and unorthodox plasticity and also show tropism for cancer. In this study, the authors attempted to access the cytotoxicity of human umbilical cord blood (hUCB)-derived MSCs, with or without cytokine activations against malignant glioma cells.

MATERIALS AND METHODS

hUCB-derived MSCs were activated by interleukin-2, interleukin-15, granulocyte macrophage colony-stimulating factor, and combinations. The hUCB-derived MSCs and activated hUCB-derived MSCs were effector cells. The cytotoxicity of the unactivated hUCB-derived MSCs and activated hUCB-derived MSCs against the target cells (human malignant glioma cells) was estimated via visual survival cell assays and transwell inserts. Phenotypic changes occurring in these hUCB-derived MSCs before and after cytokine activation were determined via flow cytometry. The secreted proteins from these effector cells were estimated via enzyme-linked immunosorbent assays.

RESULTS

We noted a significant cytotoxicity of hUCB-derived MSCs against malignant glioma cells. In addition, the hUCB-derived MSCs activated with cytokines evidenced significantly higher cytotoxicity than that observed with unactivated hUCB-derived MSCs. Differentiated immune effectors cells from the hUCB-derived MSCs after cytokine activation were not shown to have increased in number. However, the activated hUCB-derived MSCs secreted more immune response-related proteins (interleukin 4, interferon-gamma) than did the unactivated hUCB-derived MSCs.

CONCLUSION

The data collected herein confirm for the first time that hUCB-derived MSCs, with or without activation, evidence significant cytotoxicity against human malignant glioma cells, and the immune response-related proteins secreted in this process may perform relevant functions.

Application of growth factor stimulants improves cytogenetic analysis of chronic myeloproliferative disorder patients without alteration to cell lineage or clonality

Conventional cytogenetic methods rely on culturing bone marrow aspirates to obtain suitable and sufficient mitotic figures for G-banded analysis. Samples from patients with chronic myeloproliferative disorders (CMPD) often have increased failure rates due to reduced growth and poor morphology, all of which hamper the conventional karyotyping investigation. The application of growth factor (GF) stimulants to bone marrow aspirates has been shown to yield significant increases in both the quality and quantity of bone marrow metaphases obtained in 53 CPMD patient samples. All cultures were stimulated using the conditioned supernatant from the human bladder carcinoma cell line 5637, which contains IL-3, IL-6, and G-CSF. Results were assessed qualitatively on G-banded preparations and quantitatively by mitotic index (MI = % dividing cells). To assess whether the application of GF stimulants leads to clonal selection, culture samples from 15 patients were analyzed by fluorescence in situ hybridization, which supported the theory that clonal selection remains unaltered in GF-stimulated cultures. In addition to this immunophenotyping of cells, we demonstrated the lineage of cells propagated under these conditions. Cell markers were chosen to characterize B-lymphoid, T-lymphoid, myeloid, and primitive cell types. Results indicated that T cells were maintained in culture and B-lymphoid markers remained negative. In the myeloid subset, there was an overall reduction in the pan-myeloid markers. We believe this represents the loss of terminally differentiated cells (e.g., neutrophils) in culture. Overall, the study clearly demonstrates that the application of GF stimulants does not alter clonality or cell lineage propagated in these samples and is therefore suitable for application in diagnostic cytogenetic laboratories.

Co expression of SCF and KIT in gastrointestinal stromal tumours (GISTs) suggests an autocrine/paracrine mechanism

KIT is a tyrosine kinase receptor expressed by several tumours, which has for specific ligand the stem cell factor (SCF). KIT is the main oncogene in gastrointestinal stromal tumours (GISTs), and gain-of-function KIT mutations are present in 70% of these tumours. The aim of the study was to measure and investigate the mechanisms of KIT activation in 80 KIT-positive GIST patients. KIT activation was quantified by detecting phosphotyrosine residues in Western blotting. SCF production was determined by reverse transcriptase-PCR, ELISA and/or immunohistochemistry. Primary cultures established from three GISTs were also analysed. The results show that KIT activation was detected in all cases, even in absence of KIT mutations. The fraction of activated KIT was not correlated with the mutational status of GISTs. Membrane and soluble isoforms of SCF mRNA were present in all GISTs analysed. Additionally, SCF was also detected in up to 93% of GISTs, and seen to be present within GIST cells. Likewise, the two SCF mRNA isoforms were found to be expressed in GIST-derived primary cultures. Thus, KIT activation in GISTs may in part result from the presence of SCF within the tumours.