Recombinant tumor necrosis factor alpha and interleukin 1 alpha increase expression of c-abl protooncogene mRNA in cultured human marrow stromal cells

Occurrence and modulation of therapeutic targets of Aurora kinase inhibition in pediatric acute leukemia cells

Acute lymphoblastic leukemia (ALL) is one of the most prevelant pediatric malignancies. Although cure rates have improved in recent decades, approximately one in five children relapse, and survival rates post-relapse remain low. Therefore, more effective and innovative therapeutic strategies are needed in order to improve the outcome in these children. Aurora kinases, a family of serine/threonine kinases essential for regulated mitosis, are overexpressed in many forms of cancer, and have been identified as potential targets for cancer therapeutics. Based on this premise, we evaluated the activity of the Aurora-A/B inhibitor AT9283 against pediatric leukemia cells. It was found that AT9283 significantly inhibited the growth and survival of cell lines derived from patients with pediatric leukemia. Specifically, AT9283 promoted Flt-3 dephosphorylation, inhibiting the activity of downstream effectors such as Erk and Mek. In addition, apoptotic markers were also identified, providing a panel of markers for biological correlative analysis for drug activity. Lastly, drug combination studies demonstrated the potential of several novel and conventional agents to synergize with AT9283, including apicidin, 17-allylamino-17-demethoxygeldanamycin (17-AAG) and doxorubicin. These data provide a rationale for further studies and the formulation of a clinical trial of AT9283 for the treatment of refractory pediatric ALL.

Murine Bone Marrow Stromal Cells Sustain In Vivo the Survival of Hematopoietic Stem Cells and the Granulopoietic Differentiation of More Mature Progenitors

The study of the human hematopoietic system would be facilitated by availability of a relevant animal model. Because the medullar microenvironment is made of different types of cells, interactions between hematopoietic cells and stromal cells are difficult to analyze in detail. As an approach for establishing an in vivo model to dissect these interactions, we grafted murine bone marrow fibroblastic cells (MS-5 cell line) with hematopoietic cells into the kidney capsule of syngenic mice. To identify the origin of cells present in the graft, we used green fluorescent protein-stable transfected MS-5 cells for the transplantation. To analyze the evolution of stromal cells and identify hematopoietic cells able to develop in these conditions, we performed morphology, histochemistry, and immunohistology on tissue sections at different times after transplantation. When injected alone, MS-5 cells differentiate into adipocytes. When injected with a bone marrow suspension or with isolated CD45+ cells (leukocytes), the stromal cells keep their fibroblastic morphology and their alkaline phosphatase expression and sustain granulopoiesis. When injected with hematopoietic stem cells called c-kit+ Sca-1+ Lin- suspension, clusters of hematopoietic cells are also observed: They do not present any granulopoietic activity and do not belong to B or T population nor to erythroid lineage. They are quiescent, induce bone marrow recovery and survival of lethally irradiated recipients, are able to form macroscopic colonies in the spleen, and are able to form very few colonies in vitro, suggesting that they are hematopoietic stem cells. In conclusion, our results show that reticular fibroblastic stromal cells MS-5 sustain the survival of stem cells and are not able to induce their differentiation. However, they can control differentiation, proliferation, and/or survival of hematopoietic cells engaged in myeloid lineage.

Identification of TopBP1 as a c-Abl-interacting Protein and a Repressor for c-Abl Expression

Expression of BCR-ABL is the leading cause of chronic myelogenous leukemia. In chronic myelogenous leukemia cells, c-Abl expression is silenced by promoter methylation. In addition, the level of c-Abl needs to be tightly and constantly regulated due to its cytotoxicity and its rapid degradation after activation. Yet the regulation of c-Abl expression remains unclear. In an effort to gain better understanding of c-Abl function, we performed a glutathione S-transferase-Abl pull-down screen and identified TopBP1, a topoisomerase IIbeta-binding protein that contains Brca1 C-terminal motifs and has been implicated in DNA damage response. Their physical interaction was verified by in vitro and in vivo assays with TopBP1 found as a substrate of Abl proteins. TopBP1 could repress the expression of c-Abl at both mRNA and protein levels. Reporter assays indicate that TopBP1 directly repressed the promoter activity of c-Abl. Furthermore, TopBP1 repressed expression of c-Abl through a novel mechanism that involved histone deacetylation and DNA methylation. This transcriptional repression was inhibited by c-Abl in a kinase-dependent manner. The dual antagonistic interplay between c-Abl and TopBP1 may also provide a mechanism for fine-tuning of c-Abl levels.

Downregulation of c-myc expression by tumor necrosis factor-alpha in combination with transforming growth factor-beta or interferon-gamma with concomitant inhibition of proliferation in human cell lines

The modulation of cell growth by tumor necrosis factor-alpha (TNF-alpha), or TNF-alpha in combination with transforming growth factor-beta (TGF-beta) or interferon-gamma (IFN-gamma) was investigated. TNF-alpha inhibited the proliferation of U937 cells, a monocytic leukemic cell line, and of NA cells that were established from oral squamous cell carcinoma. TNF-alpha showed a cytolytic effect on NA cells in the presence of actinomycin D. TNF-alpha in combination with TGF-beta and TNF-alpha combined with INF-gamma synergistically inhibited the cell proliferation of U937 and NA cells, respectively. TNF-alpha dose-dependently reduced c-myc mRNA expression of U937 and NA cells within 1 h. The combination of TNF-alpha and TGF-beta in U937 cells and that of TNF-alpha and IFN-gamma in NA cells cooperatively reduced the expression of c-myc mRNA. TNF-alpha had little or no effect on the half-life of c-myc mRNA, indicating that c-myc mRNA expression was reduced at transcriptional level. Cycloheximide did not mediate the inhibition of c-myc gene expression, suggesting that the TNF-alpha action was independent of de novo protein synthesis. These data suggest that the reduction of c-myc gene at transcriptional level by TNF-alpha or TNF-alpha in combination with TGF-beta or IFN-gamma plays a primary role in the inhibition of cell growth at an early stage.

Effect of IL-1 on experimental bone/bone-marrow metastases

Bone metastasis is a common event and a major cause of morbidity in cancer patients. The hematopoietic marrow of the bones, rather than the bone tissue per se, is the target organ in bone metastasis. In the bone marrow, IL-1 induces the release of hematopoietic growth factors that may affect tumor-cell growth. We treated groups of mice with rhuIL-1 alpha to examine its role in the establishment of experimental bone/bone-marrow metastasis. We found that injection of 2 micrograms of rhuIL-1 alpha 24 hr prior to, simultaneously with or 24 hr after the injection of 10(4) B16 melanoma cells into the left cardiac ventricle of mice resulted in a 2-fold increase in the average number of colonized bones per mouse. GM-CSF is produced by bone-marrow stromal cells in response to IL-1, and its receptor has been found on tumor cells, including melanoma cells. However, the administration of rmuGM-CSF to mice by either multiple injections or continuous infusion did not affect the number of colonized bones. Many of the biologic effects of IL-1 are mediated by prostaglandins. Treatment of mice with 100 micrograms of indomethacin, a potent inhibitor of prostaglandin synthesis, prior to the injection of rhuIL-1 alpha, prevented the increase in number of bone metastases. To determine whether constitutive productions of IL-1 and/or prostaglandins are involved in the pathogenesis of bone/bone marrow metastasis, we treated mice with antimouse IL-1 alpha neutralizing antibodies, rhuIRAP (an inhibitor of IL-1 activity) or indomethacin. We found no difference in the average number of colonized bones per mouse between treated and control mice. We conclude that exogenous administration of IL-1 enhances experimental bone/bone-marrow metastases, and that this phenomenon is mediated through prostaglandins. However, neither the constitutive production of IL-1 nor that of prostaglandins appear to play a role in the pathogenesis of bone/bone-marrow metastasis in our murine model system.

Tumor necrosis factor-induced proliferation of astrocytes from mature brain is associated with down-regulation of glial fibrillary acidic protein mRNA

Previous results from this laboratory have shown that tumor necrosis factor (TNF) is mitogenic for bovine astrocytes in chemically defined (CD) medium. The maximum mitogenic response was detected with 200 U/ml at 48 h. We have now extended these studies to assess the effect of TNF on message levels for the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. The results have shown that, whereas TNF had only a slight effect on vimentin mRNA, TNF induced a marked decrease to 4.3 +/- 2.0% of controls in GFAP mRNA which was both time and dose dependent. The lowest effective dose was 50 U/ml and the maximal effective dose was 200 U/ml. Kinetic analysis of this response demonstrated that a marked decrease in GFAP mRNA was present at 12 h and continued to decrease through 72 h. To determine the reversibility of the TNF effect, astrocyte cultures were exposed to 200 U/ml TNF for varying periods of time and then cultured in fresh CD medium. A 1-h pulse with TNF was sufficient to reduce GFAP mRNA levels when measured 24 h later. However, cultures incubated with 200 U/ml TNF for 48 h followed by incubation in CD medium without TNF for 7 days showed that GFAP mRNA levels had returned to 60% of the control values. Nuclear runoff assays showed that the effect of TNF on GFAP mRNA was at the posttranscriptional level. Polyacrylamide gel electrophoretic analysis of astrocyte cytoskeletal proteins demonstrated that GFAP levels were reduced after a 5-day incubation with 200 U/ml TNF whereas protein levels of vimentin and actin were not significantly changed.(ABSTRACT TRUNCATED AT 250 WORDS)

Transforming growth factor beta expression in human marrow stromal cells

The effects of hematopoietic cytokines on the expression of transforming growth factors (TGF beta) mRNA and the effect of TGF beta on cytokine and on a major extracellular matrix protein, collagen I, mRNA expression was studied in human marrow stromal cells. As with other cultured mesenchymal cells, stromal cells constitutively express TGF beta 1 but not TGF alpha mRNA. In simian virus 40 (SV40)-transformed stromal cells downregulation of TGF beta 1 expression was observed 2 hours after incubation with recombinant human (rh) tumor-necrosis factor alpha (TNF alpha) and 144 h after addition of rh granulocyte macrophage colony-stimulating factor (GM-CSF). Neither interleukin-1 (IL-1)beta nor IL-6 had an observable effect on TGF beta 1 mRNA expression. TGF beta upregulated collagen I mRNA expression. These data suggest that cytokines may influence TGF beta mRNA expression.