Differential gene expression induction by TRAIL in B chronic lymphocytic leukemia (B-CLL) cells showing high versus low levels of Zap-70

Combination Treatment of p53-Null HL-60 cells with Histone Deacetylase Inhibitors and Chlorambucil Augments Apoptosis and Increases BCL6 and p21 Gene Expression

BACKGROUND

Treatment of hematological malignancies with conventional DNA-damaging drugs, such as chlorambucil (CLB), commonly results in p53-dependent chemo-resistance. Chromatin modifying agents, such as histone deacetylase inhibitors (HDACIs), sodium butyrate (NaBu) and trichostatin A (TSA), may reverse chemo-resistance by modulating the activity of chromatin remodeling enzymes and/or genes that control cell proliferation, differentiation and survival.

OBJECTIVE

This study examined the potential use of HDACIs and CLB combination therapies in an in vitro chemo-resistant leukemia model.

METHODS

The p53-null promyelocytic leukemia cell line, HL60, was used as an in vitro model of chemo-resistant leukemia. Drug cytotoxicity was determined by tetrazolium salt-based colorimetric assays and Annexin V/propidium iodide staining (flow cytometry). The level of mRNA expression of the chromatin modifying genes was measured by quantitative real-time PCR.

RESULTS

Micromolar concentrations of CLB combined with either NaBu or TSA triggered synergistic cytotoxic effects in HL-60 cells (p < 0.001). The effects of the combination treatments resulted in upregulated p21 gene expression (up to 59-fold; p<0.001) that preceded an increase in BCL6 gene expression (up to 20-fold; p < 0.001). Statistically significant but smaller magnitude changes (≤ 2-fold; p <0.05) were noted in the expression of other genes studied regardless of the treatment type.

CONCLUSION

The combination treatment of p53-null HL-60 cells with DNA-damaging agent CLB and HDACIs NaBu and TSA triggered additive to synergistic effects on apoptosis and upregulated BCL6 and p21 expression. These findings reveal BCL6 and p21 as potential targets of chemo-resistance for the development of anti-leukemic drugs.

The role of chemokines in B cell chronic lymphocytic leukaemia: pathophysiological aspects and clinical impact

Chemokines are centrally involved in leukocyte migration, homing and haematopoiesis. Besides these physiological aspects, their role in pathological processes especially with respect to solid tumour and haematological neoplasias is well established. In this context, the focus was set here on disclosing their contribution in B cell chronic lymphocytic leukaemia (B-CLL), which is regarded as the most characteristic low-grade lymphoma. Up to now, it has been demonstrated that several chemokines are involved in migration of B-CLL cells to lymph nodes, secondary lymphoid organs and bone marrow. Moreover, some chemokines are known to have an anti-apoptotic effect and thus contribute to the survival of B-CLL cells. By interfering with both of these aspects, new therapeutic targets for this yet incurable disease may be developed. Furthermore, a correlation can be drawn between the concentration of some chemokines in patients' serum, the expression of their respective receptors on B-CLL cells and well-established predictive clinical parameters. Consequently, further systematic investigation of the chemokine network may lead to the identification of new diagnostic and prognostic markers. This review focuses on the impact of chemokines and their receptors on B-CLL pathophysiology and points out potential implications for both treatment and diagnosis.

Resistance to TRAIL-induced apoptosis caused by constitutional phosphorylation of Akt and PTEN in acute lymphoblastic leukemia cells

OBJECTIVE

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor superfamily, which induces apoptosis in cancer cells but not in normal cells. Akt/protein kinase B, when phosphorylated to its active form, promotes cell survival and blocks apoptosis. The aim of this study was to investigate the role of Akt pathway in acquired TRAIL resistance of acute lymphoblastic leukemia cells.

MATERIALS AND METHODS

MB-IT and NALM-24 cells that developed resistance to TRAIL, i.e., TRAIL-resistant cells (MB-IT R and NALM-24 R) were established from TRAIL-sensitive acute lymphoblastic leukemia cell lines (MB-IT S and NALM-24 S), respectively, through application of TRAIL and repetitive limiting dilution. Apoptosis was measured by flow cytometry using propidium iodide/Annexin-V fluorescein isothiocyanate staining. TRAIL receptor cell surface expression of MB-IT and NALM-24 were analyzed by flow cytometry. Protein levels were analyzed by Western blot analysis.

RESULTS

The obtained resistant cell lines presented the same pattern of receptor expression as sensitive parent cells, and the internalization of DR5 after TRAIL treatment was similar. Caspase-8/3, FLIP, BID, XIAP were cleaved/downregulated in sensitive cells after treatment with TRAIL, but not in the resistant cells. We also observed that phosphoinositide-3-kinase (PI3K)/Akt pathway was constitutively active in resistant clones, and was not downregulated upon TRAIL treatment. Phosphate and tensin homologue deleted on chromosome 10 (PTEN) level was the same in both sensitive cells and resistant cells, but was quickly downregulated in sensitive cells after TRAIL treatment. Also, resistant cells expressed a high level of phosphorylated inactive form of PTEN than the sensitive cells. Expression levels of PH domain leucine-rich repeat protein phosphatase were slightly higher in sensitive than resistant cells. When resistant cells were treated with LY 294002 (a PI3K inhibitor), the expression level of phosphorylated Akt was distinctly downregulated, and there was induction of apoptosis when these cells were treated with a combination of TRAIL and LY 294002. When MB-IT-sensitive cells were treated with okadaic acid, a phosphatase inhibitor, TRAIL-induced apoptosis was significantly reduced.

CONCLUSION

These results suggest that cellular resistance to TRAIL could be developed through phosphorylation (activation) of Akt and phosphorylation (inactivation) of PTEN.

Stimulation of iNOS expression and apoptosis resistance in B-cell chronic lymphocytic leukemia (B-CLL) cells through engagement of Toll-like receptor 7 (TLR-7) and NF-kappaB activation

B-CLL cells are characterized by in vivo resistance to apoptosis due, in part, to the presence of an inducible nitric oxide synthase, iNOS, as the NO released plays anti-apoptotic role, notably by inhibiting caspases. The mechanisms leading to spontaneous expression of iNOS in these cells are presently unknown. The restricted use of some V(H) sub-groups and the sequences of the monoclonal immunoglobulins of the B-cell receptor expressed by the leukemia cells suggested that the latter have encountered specific auto-antigens and/or microbial derived antigens. Their binding to the BCR provides an activation signal resulting in enhanced survival, hence could be involved in the aetiology of the disease. At the interface of innate and cognate immunity, Toll-like receptors, TLR, recognize PAMPs (pathogen-associated molecular patterns) expressed by various bacteria and virus as well as some self-antigens. We thus hypothesized that TLR were involved in the early steps of B-CLL oncogenesis, notably apoptosis resistance through the induction of iNOS expression and the production of NO. Our results show that B-CLL cells express TLR-7 and TLR-9. Incubation of B-CLL cells with TLR-7 agonists effectively resulted in an increased resistance to apoptosis that was reverted with the NOS inhibitor L-NMMA. This resistance was associated with enhanced iNOS expression (protein and mRNA) and NO release, stimulation of NF-kappaB activation, phosphorylation of I kappaB alpha, all these events being suppressed with wedelolactone or Bay 11-7085, two inhibitors of I kappaB alpha phosphorylation. Our present data thus suggest that TLR-7 signaling stimulates apoptosis resistance, notably through an NF-kappaB-dependent activation of the NO pathway.

Tumor-necrosis-factor-related apoptosis-inducing ligand and the regulation of hematopoiesis

PURPOSE OF REVIEW

This review will focus on the emerging role of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/TRAIL-receptors in the pathophysiology of hematopoiesis and on the potential therapeutic applications of either recombinant TRAIL or anti-TRAIL-R1/-R2 agonistic antibodies for the treatment of hematological malignancies.

RECENT FINDINGS

While CD34 stem/progenitor cells do not express TRAIL-receptors and are protected from TRAIL-induced apoptosis, accumulating evidence points to a role for elevated expression/release of TRAIL at the bone marrow level in the pathophysiology of aplastic anemia, Fanconi anemia, and myelodysplastic syndromes. In-vitro data show promising synergistic effects of recombinant TRAIL in association with proteasome or histone deacetylase inhibitors, natural compounds or small molecules in the therapy of myeloid and lymphoid malignancies. Moreover, although both recombinant TRAIL and anti-TRAIL-R1/-R2 antibodies are well tolerated in vivo, anti-TRAIL-R1/-R2 agonistic antibodies show the potential advantage of avoiding the neutralizing activity of the soluble receptor osteoprotegerin.

SUMMARY

While a chronic pathological elevation of TRAIL at the bone marrow level might contribute to the impairment of normal hematopoiesis, the use of recombinant TRAIL and anti-TRAIL-R1/-R2 agonistic antibodies appears particularly promising for the treatment of hematological malignancies in particular, of multiple myeloma, especially if used in association with innovative therapeutic compounds.

Combined treatment of CpG-oligodeoxynucleotide with Nutlin-3 induces strong immune stimulation coupled to cytotoxicity in B-chronic lymphocytic leukemic (B-CLL) cells

We have investigated the effect of combined treatment with CpG-oligodeoxynucleotide (CpG-ODN) plus Nutlin-3, a small molecule inhibitor of the murine double minute 2/p53 interaction, on the immune activation, cell cycle progression, and apoptosis of peripheral blood B chronic lymphocytic leukemia (B-CLL) cells. CpG-ODN induced a robust up-regulation of immune activation markers (CD54, CD69, CD80, CD86, MHC-II) in Zap70high and Zap70low B-CLL samples. Although cotreatment of B-CLL cells with CpG-ODN + Nutlin-3 did not interfere with such immune activation, CpG-ODN potentiated the Nutlin-3-mediated induction of the death receptors CD95 and TRAIL receptor 2. Importantly, treatment with CpG-ODN did not interfere with the ability of Nutlin-3 to inhibit cell cycle progression and to induce apoptosis. Thus, a therapeutic regimen including CpG-ODN plus Nutlin-3 might have the advantage to preserve the immune activation of B-CLL cells while restraining the prosurvival/proliferative potential of CpG-ODN treatment.