In vivo ribosomal RNA turnover is down-regulated in leukaemic cells in chronic lymphocytic leukaemia
; ; et al
in British Journal of Haematology (2010), 151Detailed reference viewed: 19 (7 ULg)
Valproate synergizes with purine nucleoside analogues to induce apoptosis of B-chronic lymphocytic leukaemia cells.
Bouzar, Amel ; Boxus, Mathieu ; et al
in British journal of haematology (2009), 144(1),Detailed reference viewed: 55 (12 ULg)
Measurement of ribosomal RNA turnover in vivo by use of deuterium-labeled glucose.
; ; et al
in Clinical Chemistry (2009), 55(10), 1824-33
BACKGROUND: Most methods for estimation of rates of RNA production are not applicable in human in vivo clinical studies. We describe here an approach for measuring ribosomal RNA turnover in vivo using [6 ... [more ▼]
BACKGROUND: Most methods for estimation of rates of RNA production are not applicable in human in vivo clinical studies. We describe here an approach for measuring ribosomal RNA turnover in vivo using [6,6-(2)H(2)]-glucose as a precursor for de novo RNA synthesis. Because this method involves neither radioactivity nor toxic metabolites, it is suitable for human studies. METHODS: For method development in vitro, a lymphocyte cell line (PM1) was cultured in the presence of [6,6-(2)H(2)]-glucose. RNA was extracted, hydrolyzed enzymatically to ribonucleosides, and derivatized to either the aldonitrile tetra-acetate or the pentafluoro triacetate derivative of the pentose before GC-MS. We identified optimum derivatization and analysis conditions and demonstrated quantitative incorporation of deuterium from glucose into RNA of dividing cells. RESULTS: Pilot clinical studies demonstrated the applicability of this approach to blood leukocytes and solid tissues. A patient with chronic lymphocytic leukemia received [6,6-(2)H(2)]-glucose (1 g/kg) orally in aliquots administered every 30 min for a period of 10 h. When we analyzed CD3(-) B cells that had been purified by gradient centrifugation and magnetic-bead adhesion, we observed deuterium enrichment, a finding consistent with a ribosomal RNA production rate of about 7%/day, despite the slow division rates observed in concurrent DNA-labeling analysis. Similarly, in 2 patients with malignant infiltration of lymph nodes, administration of [6,6-(2)H(2)]-glucose (by intravenous infusion for 24 h) before excision biopsy allowed estimation of DNA and RNA turnover in lymph node samples. CONCLUSIONS: Our study results demonstrate the proof-of-principle that deuterium-labeled glucose may be used to analyze RNA turnover, in addition to DNA production/cell proliferation, in clinical samples. [less ▲]Detailed reference viewed: 49 (5 ULg)
Reduction of B cell turnover in chronic lymphocytic leukaemia.
; ; et al
in British Journal of Haematology (2008), 143(2), 240-7
Whether chronic lymphocytic leukaemia (CLL) is a latent or a proliferating disease has been intensively debated. Whilst the dogma that CLL results from accumulation of dormant lymphocytes is supported by ... [more ▼]
Whether chronic lymphocytic leukaemia (CLL) is a latent or a proliferating disease has been intensively debated. Whilst the dogma that CLL results from accumulation of dormant lymphocytes is supported by the unresponsiveness of leukaemic cells to antigens and polyclonal activators, recent in vivo kinetic measurements indicate that B lymphocytes do divide at significant rates in CLL. However, an important and still unanswered question is whether CLL cells proliferate faster or slower compared with their normal counterparts. This report addressed directly this point and compared B-cell kinetics in CLL subjects and healthy controls, using a pulse-chase approach based on incorporation of deuterium from 6,6-(2)H(2)-glucose into DNA. We confirmed that B cells proliferated at significant levels in CLL but found that the proliferation rates were reduced compared with healthy subjects (mean 0.47 vs. 1.31%/d respectively, P = 0.007), equivalent to an extended doubling time of circulating B cells (147 d vs. 53 d). In conclusion, CLL B cells proliferate at reduced levels compared with healthy controls. CLL is thus characterized by an aberrant B-cell kinetics with a decrease in cell turnover, an observation that may impact on elaboration of efficient therapeutic strategies. [less ▲]Detailed reference viewed: 47 (12 ULg)
Valproic acid induces apoptosis in chronic lymphocytic leukemia cells through activation of the death receptor pathway and potentiates TRAIL response.
; Gillet, Nicolas ; et al
in Experimental hematology (2007), 35(10), 1527-37
OBJECTIVE: Chronic lymphocytic leukemia (CLL) cells develop chemoresistance over time associated with defects in apoptosis pathway. Novel treatment strategies are required to overcome resistance of cells ... [more ▼]
OBJECTIVE: Chronic lymphocytic leukemia (CLL) cells develop chemoresistance over time associated with defects in apoptosis pathway. Novel treatment strategies are required to overcome resistance of cells to commonly used agents. The effects of valproic acid (VPA), an antiepileptic drug with histone deacetylase inhibitory activity, on mononuclear cells isolated from 40 CLL patients were evaluated. METHODS: CLL cells were treated with increasing doses of VPA (0.5, 1, 2, and 5 mM). The mode of cytotoxic drug action was determined by annexin binding, DNA fragmentation, and caspase activation. RESULTS: Exposure of CLL cells to VPA resulted in dose-dependent cytotoxicity and apoptosis in the 40 CLL patients. VPA treatment induced apoptotic changes in CLL cells including phosphatidylserine externalization and DNA fragmentation. The mean apoptotic rates were similar between IgV(H) mutated and unmutated patients, the latter presenting a more aggressive clinical course. VPA induced apoptosis via the extrinsic pathway involving engagement of the caspase-8-dependent cascade. Although CLL cells are commonly resistant to death receptor-induced apoptosis, VPA significantly increased sensitivity of leukemic cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and led to downregulation of c-FLIP (L) expression. VPA caused no potentialization of TRAIL-induced apoptosis on normal B cells. In addition, VPA overcame the prosurvival effects of bone marrow stromal cells. CONCLUSION: These findings point out that the combination of TRAIL and VPA, at clinically relevant concentration, may be valuable in the treatment of CLL. [less ▲]Detailed reference viewed: 53 (4 ULg)
Valproate activates bovine leukemia virus gene expression, triggers apoptosis, and induces leukemia/lymphoma regression in vivo.
; Florins, Arnaud-Francois ; Gillet, Nicolas et al
in Proceedings of the National Academy of Sciences of the United States of America (2005), 102(29), 10309-14
Leukemogenic viruses like human T-lymphotropic virus and bovine leukemia virus (BLV) presumably persist in the host partly by latent integration of the provirus in a fraction of infected cells, leading to ... [more ▼]
Leukemogenic viruses like human T-lymphotropic virus and bovine leukemia virus (BLV) presumably persist in the host partly by latent integration of the provirus in a fraction of infected cells, leading to accumulative increase in the outgrowth of transformed cells. Furthermore, viral infection also correlates with a blockade of the apoptotic mechanisms concomitant with an apparent latency of the host cell. Conceptually, induction of viral or cellular gene expression could thus also be used as a therapeutic strategy against retroviral-associated leukemia. Here, we provide evidence that valproate, an inhibitor of deacetylases, activates BLV gene expression in transient transfection experiments and in short-term cultures of primary B-lymphocytes. In vivo, valproate injection into newly BLV-inoculated sheep did not abrogate primary infection. However, valproate treatment, in the absence of any other cytotoxic drug, was efficient for leukemia/lymphoma therapy in the sheep model leading to decreased lymphocyte numbers (respectively from 25.6, 35.7, and 46.5 x 10(3) cells per mm3 to 1.0, 10.6, and 24.3 x 10(3) cells per mm3 in three leukemic sheep) and tumor regression (from >700 cm3 to undetectable). The concept of a therapy that targets the expression of viral and cellular genes might be a promising treatment of adult T cell leukemia or tropical spastic paraparesis/human T-lymphotropic virus-associated myelopathy, diseases for which no satisfactory treatment exists so far. [less ▲]Detailed reference viewed: 85 (32 ULg)