The novel nuclear factor-kappaB inhibitor LC-1 is equipotent in poor prognostic subsets of chronic lymphocytic leukemia and shows strong synergy with fludarabine

Natural and Synthetic Lactones Possessing Antitumor Activities

Cancer is one of the leading causes of death globally, accounting for an estimated 8 million deaths each year. As a result, there have been urgent unmet medical needs to discover novel oncology drugs. Natural and synthetic lactones have a broad spectrum of biological uses including anti-tumor, anti-helminthic, anti-microbial, and anti-inflammatory activities. Particularly, several natural and synthetic lactones have emerged as anti-cancer agents over the past decades. In this review, we address natural and synthetic lactones focusing on their anti-tumor activities and synthetic routes. Moreover, we aim to highlight our journey towards chemical modification and biological evaluation of a resorcylic acid lactone, L-783277 (4). We anticipate that utilization of the natural and synthetic lactones as novel scaffolds would benefit the process of oncology drug discovery campaigns based on natural products.

Chemical modification of ovatodiolide revealed a promising amino-prodrug with improved pharmacokinetic profile

Stepwise modification of ovatodiolide revealed a prodrug, NMP-diepoxyovatodiolide, which can provide sustained release of an active compound, substantial metabolic stability and a unique accumulation profile in the liver. Besides, NMP-diepoxyovatodiolide demonstrated therapeutic benefits in an acute autoimmune hepatitis mouse model and a broad safety window. Therefore, NMP-diepoxyovatodiolide is a very promising candidate for further development of liver-related drugs.

Biological and clinical implications of BIRC3 mutations in chronic lymphocytic leukemia

BIRC3 is a recurrently mutated gene in chronic lymphocytic leukemia (CLL) but the functional implications of BIRC3 mutations are largely unexplored. Furthermore, little is known about the prognostic impact of BIRC3 mutations in CLL cohorts homogeneously treated with first-line fludarabine, cyclophosphamide, and rituximab (FCR). By immunoblotting analysis, we showed that the non-canonical nuclear factor-κB pathway is active in BIRC3-mutated cell lines and in primary CLL samples, as documented by the stabilization of MAP3K14 and by the nuclear localization of p52. In addition, BIRC3-mutated primary CLL cells are less sensitive to flu-darabine. In order to confirm in patients that BIRC3 mutations confer resistance to fludarabine-based chemoimmunotherapy, a retrospective multicenter cohort of 287 untreated patients receiving first-line FCR was analyzed by targeted next-generation sequencing of 24 recurrently mutated genes in CLL. By univariate analysis adjusted for multiple comparisons BIRC3 mutations identify a poor prognostic subgroup of patients in whom FCR treatment fails (median progression-free survival: 2.2 years, P<0.001) similar to cases harboring TP53 mutations (median progression-free survival: 2.6 years, P<0.0001). BIRC3 mutations maintained an independent association with an increased risk of progression with a hazard ratio of 2.8 (95% confidence interval 1.4-5.6, P=0.004) in multivariate analysis adjusted for TP53 mutation, 17p deletion and IGHV mutation status. If validated, BIRC3 mutations may be used as a new molecular predictor to select high-risk patients for novel frontline therapeutic approaches.

Chronic low dose ethanol induces an aggressive metastatic phenotype in TRAMP mice, which is counteracted by parthenolide

Despite advances in prostate cancer therapy, dissemination and growth of metastases results in shortened survival. Here we examined the potential anti-cancer effect of the NF-κB inhibitor parthenolide (PTL) and its water soluble analogue dimethylaminoparthenolide (DMAPT) on tumour progression and metastasis in the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model of prostate cancer. Six-week-old male TRAMP mice received PTL (40 mg/kg in 10% ethanol/saline), DMAPT (100 mg/kg in sterile water), or vehicle controls by oral gavage thrice weekly until palpable tumour formation. DMAPT treatment slowed normal tumour development in TRAMP mice, extending the time-to-palpable prostate tumour by 20%. PTL did not slow overall tumour development, while the ethanol/saline vehicle used to administer PTL unexpectedly induced an aggressive metastatic tumour phenotype. Chronic ethanol/saline vehicle upregulated expression of NF-κB, MMP2, integrin β1, collagen IV, and laminin, and induced vascular basement membrane degradation in primary prostate tumours, as well as increased metastatic spread to the lung and liver. All of these changes were largely prevented by co-administration with PTL. DMAPT (in water) reduced metastasis to below that of water-control. These data suggest that DMAPT has the potential to be used as a cancer preventive and anti-metastatic therapy for prostate cancer. Although low levels of ethanol consumption have not been shown to strongly correlate with prostate cancer epidemiology, these results would support a potential effect of chronic low dose ethanol on metastasis and the TRAMP model provides a useful system in which to further explore the mechanisms involved.

PARP1 expression, activity and ex vivo sensitivity to the PARP inhibitor, talazoparib (BMN 673), in chronic lymphocytic leukaemia

In chronic lymphocytic leukemia (CLL), mutation and loss of p53 and ATM abrogate DNA damage signalling and predict poorer response and shorter survival. We hypothesised that poly (ADP-ribose) polymerase (PARP) activity, which is crucial for repair of DNA breaks induced by oxidative stress or chemotherapy, may be an additional predictive biomarker and a target for therapy with PARP inhibitors.

We measured PARP activity in 109 patient-derived CLL samples, which varied widely (192 – 190052 pmol PAR/10⁶ cells) compared to that seen in healthy volunteer lymphocytes (2451 – 7519 pmol PAR/10⁶ cells). PARP activity was associated with PARP1 protein expression and endogenous PAR levels. PARP activity was not associated with p53 or ATM loss, Binet stage, IGHV mutational status or survival, but correlated with Bcl-2 and Rel A (an NF-kB subunit). Levels of 8-hydroxy-2′-deoxyguanosine in DNA (a marker of oxidative damage) were not associated with PAR levels or PARP activity. The potent PARP inhibitor, talazoparib (BMN 673), inhibited CD40L-stimulated proliferation of CLL cells at nM concentrations, independently of Binet stage or p53/ATM function.

PARP activity is highly variable in CLL and correlates with stress-induced proteins. Proliferating CLL cells (including those with p53 or ATM loss) are highly sensitive to the PARP inhibitor talazoparib.

Key Molecular Drivers of Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is an adult neoplastic disease of B cells characterized by variable clinical outcomes. Although some patients have an aggressive form of the disease and often encounter treatment failure and short survival, others have more stable disease with long-term survival and little or no need for theraphy. In the past decade, significant advances have been made in our understanding of the molecular drivers that affect the natural pathology of CLL. The present review describes what is known about these key molecules in the context of their role in tumor pathogenicity, prognosis, and therapy.

The NAE inhibitor pevonedistat interacts with the HDAC inhibitor belinostat to target AML cells by disrupting the DDR

Two classes of novel agents, NEDD8-activating enzyme (NAE) and histone deacetylase (HDAC) inhibitors, have shown single-agent activity in acute myelogenous leukemia (AML)/myelodysplastic syndrome (MDS). Here we examined mechanisms underlying interactions between the NAE inhibitor pevonedistat (MLN4924) and the approved HDAC inhibitor belinostat in AML/MDS cells. MLN4924/belinostat coadministration synergistically induced AML cell apoptosis with or without p53 deficiency or FLT3-internal tandem duplication (ITD), whereas p53 short hairpin RNA (shRNA) knockdown or enforced FLT3-ITD expression significantly sensitized cells to the regimen. MLN4924 blocked belinostat-induced antiapoptotic gene expression through nuclear factor-κB inactivation. Each agent upregulated Bim, and Bim knockdown significantly attenuated apoptosis. Microarrays revealed distinct DNA damage response (DDR) genetic profiles between individual vs combined MLN4924/belinostat exposure. Whereas belinostat abrogated the MLN4924-activated intra-S checkpoint through Chk1 and Wee1 inhibition/downregulation, cotreatment downregulated multiple homologous recombination and nonhomologous end-joining repair proteins, triggering robust double-stranded breaks, chromatin pulverization, and apoptosis. Consistently, Chk1 or Wee1 shRNA knockdown significantly sensitized AML cells to MLN4924. MLN4924/belinostat displayed activity against primary AML or MDS cells, including those carrying next-generation sequencing-defined poor-prognostic cancer hotspot mutations, and CD34(+)/CD38(-)/CD123(+) populations, but not normal CD34(+) progenitors. Finally, combined treatment markedly reduced tumor burden and significantly prolonged animal survival (P < .0001) in AML xenograft models with negligible toxicity, accompanied by pharmacodynamic effects observed in vitro. Collectively, these findings argue that MLN4924 and belinostat interact synergistically by reciprocally disabling the DDR in AML/MDS cells. This strategy warrants further consideration in AML/MDS, particularly in disease with unfavorable genetic aberrations.

Gene expression of INPP5F as an independent prognostic marker in fludarabine-based therapy of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease. Various disease-related and patient-related factors have been shown to influence the course of the disease. The aim of this study was to identify novel biomarkers of significant clinical relevance. Pretreatment CD19-separated lymphocytes (n=237; discovery set) and peripheral blood mononuclear cells (n=92; validation set) from the REACH trial, a randomized phase III trial in relapsed CLL comparing rituximab plus fludarabine plus cyclophosphamide with fludarabine plus cyclophosphamide alone, underwent gene expression profiling. By using Cox regression survival analysis on the discovery set, we identified inositol polyphosphate-5-phosphatase F (INPP5F) as a prognostic factor for progression-free survival (P<0.001; hazard ratio (HR), 1.63; 95% confidence interval (CI), 1.35-1.98) and overall survival (P<0.001; HR, 1.47; 95% CI, 1.18-1.84), regardless of adjusting for known prognostic factors. These findings were confirmed on the validation set, suggesting that INPP5F may serve as a novel, easy-to-assess future prognostic biomarker for fludarabine-based therapy in CLL.

Inhibitory effects of parthenolide on the activity of NF-κB in multiple myeloma via targeting TRAF6

This study examined the mechanism of the inhibitory effect of parthenolide (PTL) on the activity of NF-κB in multiple myeloma (MM). Human multiple myeloma cell line RPMI 8226 cells were treated with or without different concentrations of PTL for various time periods, and then MTT assay was used to detect cell proliferation. Cell cycle and apoptosis were flow cytometrically detected. The level of protein ubiquitination was determined by using immunoprecipitation. Western blotting was employed to measure the level of total protein ubiquitination, the expression of IκB-α in cell plasma and the content of p65 in nucleus. The content of p65 in nucleus before and after PTL treatment was also examined with immunofluorescence. Exposure of RPMI 8226 cells to PTL attenuated the level of ubiquitinated Nemo, increased the expression of IκB-α and reduced the level of p65 in nucleus, finally leading to the decrease of the activity of NF-κB. PTL inhibited cell proliferation, induced apoptosis and blocked cell cycle. Furthermore, the levels of ubiquitinated tumor necrosis factor receptor-associated factor 6 (TRAF6) and total proteins were decreased after PTL treatment. By using Autodock software package, we predicted that PTL could bind to TRAF6 directly and tightly. Taken together, our findings suggest that PTL inhibits the activation of NF-κB signaling pathway via directly binding with TRAF6, thereby suppressing MM cell proliferation and inducing apoptosis.

The role of inflammation in leukaemia

Acute leukaemias are a group of malignancies characterised by the invasion of the bone marrow by immature haematopoietic precursors and differentiation arrest at various maturation steps. Multiplicity of intrinsic and extrinsic factors influences the transformation and progression of leukaemia. The intrinsic factors encompass genetic alterations of cellular pathways leading to the activation of, among others, inflammatory pathways (such as nuclear factor kappa B). The extrinsic components include, among others, the inflammatory pathways activated by the bone marrow microenvironment and include chemokines, cytokines and adhesion molecules. In this chapter, we review the role of inflammatory processes in the transformation, survival and proliferation of leukaemias, particularly the role of nuclear factor kappa B and its downstream signalling in leukaemias and the novel therapeutic strategies that exploit potentially unique properties of inflammatory signalling that offer interesting options for future therapeutic interventions.

The pathogenesis of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of CD5(+)CD23(+) B cells in blood, marrow, and second lymphoid tissues. Gene-expression profiling and phenotypic studies suggest that CLL is probably derived from CD5(+) B cells similar to those found in the blood of healthy adults. Next-generation sequencing has revealed recurrent genetic lesions that are implicated in CLL pathogenesis and/or disease progression. The biology of CLL is entwined with its microenvironment, in which accessory cells can promote leukemia cell growth and/or survival. Recently, much attention has been focused on the CLL B cell receptor (BCR) and on chemokine receptors that enable CLL cells to home to lymphoid tissues and to establish the leukemia microenvironment. Agents that can interfere with BCR signaling or chemokine-receptor signaling, or that target surface antigens selectively expressed on CLL cells, promise to have significant therapeutic benefit in patients with this disease.

Molecular genetics of high-risk chronic lymphocytic leukemia

In an optimized management algorithm of chronic lymphocytic leukemia (CLL), the early identification of high-risk patients, ideally prior to treatment, is a prerequisite for designing strategies tailored at overcoming therapy resistance. TP53 abnormalities play a central role in our current understanding of the poor prognosis of high-risk CLL patients, but fail to explain the molecular basis of 50% of high-risk CLL. Next-generation sequencing studies have revealed several novel genetic alterations in high-risk CLL, including NOTCH1, SF3B1 and BIRC3 mutations. Alterations of these genes occur in 5-10% of CLL at diagnosis, show a prevalence that increases in the more advanced phases of the disease, and confer poor prognosis in consecutive CLL series.

Epigenetic upregulation of lncRNAs at 13q14.3 in leukemia is linked to the In Cis downregulation of a gene cluster that targets NF-kB

Non-coding RNAs are much more common than previously thought. However, for the vast majority of non-coding RNAs, the cellular function remains enigmatic. The two long non-coding RNA (lncRNA) genes DLEU1 and DLEU2 map to a critical region at chromosomal band 13q14.3 that is recurrently deleted in solid tumors and hematopoietic malignancies like chronic lymphocytic leukemia (CLL). While no point mutations have been found in the protein coding candidate genes at 13q14.3, they are deregulated in malignant cells, suggesting an epigenetic tumor suppressor mechanism. We therefore characterized the epigenetic makeup of 13q14.3 in CLL cells and found histone modifications by chromatin-immunoprecipitation (ChIP) that are associated with activated transcription and significant DNA-demethylation at the transcriptional start sites of DLEU1 and DLEU2 using 5 different semi-quantitative and quantitative methods (aPRIMES, BioCOBRA, MCIp, MassARRAY, and bisulfite sequencing). These epigenetic aberrations were correlated with transcriptional deregulation of the neighboring candidate tumor suppressor genes, suggesting a coregulation in cis of this gene cluster. We found that the 13q14.3 genes in addition to their previously known functions regulate NF-kB activity, which we could show after overexpression, siRNA-mediated knockdown, and dominant-negative mutant genes by using Western blots with previously undescribed antibodies, by a customized ELISA as well as by reporter assays. In addition, we performed an unbiased screen of 810 human miRNAs and identified the miR-15/16 family of genes at 13q14.3 as the strongest inducers of NF-kB activity. In summary, the tumor suppressor mechanism at 13q14.3 is a cluster of genes controlled by two lncRNA genes that are regulated by DNA-methylation and histone modifications and whose members all regulate NF-kB. Therefore, the tumor suppressor mechanism in 13q14.3 underlines the role both of epigenetic aberrations and of lncRNA genes in human tumorigenesis and is an example of colocalization of a functionally related gene cluster.

Histone deacetylase inhibitors and rational combination therapies

Histone deacetylase inhibitors (HDACIs) are epigenetically acting agents that modify chromatin structure and by extension, gene expression. However, they may influence the behavior and survival of transformed cells by diverse mechanisms, including promoting expression of death- or differentiation-inducing genes while downregulating the expression of prosurvival genes; acting directly to increase oxidative injury and DNA damage; acetylating and disrupting the function of multiple proteins, including DNA repair and chaperone proteins; and interfering with the function of corepressor complexes. Notably, HDACIs have been shown in preclinical studies to target transformed cells selectively, and these agents have been approved in the treatment of certain hematologic malignancies, for example, cutaneous T-cell lymphoma and peripheral T-cell lymphoma. However, attempts to extend the spectrum of HDACI activity to other malignancies, for example, solid tumors, have been challenging. This has led to the perception that HDACIs may have limited activity as single agents. Because of the pleiotropic actions of HDACIs, combinations with other antineoplastic drugs, particularly other targeted agents, represent a particularly promising avenue of investigation. It is likely that emerging insights into mechanism(s) of HDACI activity will allow optimization of this approach, and hopefully, will expand HDACI approvals to additional malignancies in the future.

Apoptosis deregulation in CLL

The description of apoptosis and the identification of the genes that regulate it have proved pivotal to our understanding of how cancer cells accumulate and ultimately cause morbidity and mortality. It has become increasingly clear that in CLL the balance between the pro- and anti-apoptotic members of the BCL2 family of apoptotic regulatory proteins is critical in the development and clinical progression of CLL. Furthermore, the apoptotic potential of the CLL cell determines chemotherapy sensitivity and ultimately progression-free and overall survival. The unravelling of the BCL2 story in CLL has led to the development of a whole new class of therapeutic agents-the BH3 mimetics-which are significantly more targeted than conventional chemo-immunotherapy and therefore promise potent clinical activity coupled with reduced toxicity.

The spectrum of genetic defects in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the Western world and shows a remarkable heterogeneity in the clinical course. Understand the genetic basis of CLL may help in clarifying the molecular bases of this clinical heterogeneity. Recurrent chromosomal aberrations at 13q14, 12q, 11q22–q23 and 17p13, and TP53 mutations are the first genetic lesions identified as drivers of the disease. While some of these lesions are associated with poor outcome (17p13 deletion, TP53 mutations and, to a lesser extent, 11q22–q23 deletion) others are linked to a favorable course (13q14 deletion as sole aberration). Recently, next generation sequencing has revealed additional recurrent alterations in CLL targeting the NOTCH1, SF3B1, and BIRC3 genes. NOTCH1, SF3B1, and BIRC3 lesions provide: I) new insights on the mechanisms of leukemogenesis, tumor progression and chemoresistance in this leukemia; II) new biomarkers for the identification of poor risk patients, having individually shown correlations with survival in CLL; and III) new therapeutic targets, especially in the setting of high risk disease. This review will summarize the most important genetic aberrations in CLL and how our improved knowledge of the genome of leukemic cells may translate into improved patients' management.

The Hsp90 inhibitor NVP-AUY922-AG inhibits NF-κB signaling, overcomes microenvironmental cytoprotection and is highly synergistic with fludarabine in primary CLL cells

Heat shock protein 90 (Hsp90) is a molecular chaperone required for the stability and function of multiple over-expressed signaling proteins that promote growth and survival in cancer cells. Chronic lymphocytic leukaemia (CLL) is characterized by increased expression of several Hsp90 client proteins making it a potentially susceptible to Hsp90 inhibition. In this study we showed that the novel Hsp90 inhibitor NVP-AUY922-AG was cytotoxic to primary CLL cells in vitro (LD₅₀=0.18μM±0.20). Importantly, its toxicity was preserved under cytoprotective co-culture conditions that rendered fludarabine ineffective. At the molecular level, NVP-AUY922-AG depleted the expression of multiple Hsp90 client proteins including Akt and activators of NF-κB, IKKα and IKKβ. Consistent with this inhibition profile, NVP-AUY922-AG resulted in decreased transcription of the NF-B target genes MCL1, CFLAR, BIRC5. In contrast, fludarabine significantly induced the transcription of MCL1 and BIRC5. Given the anti-apoptotic nature of these genes and the role they play in fludarabine resistance, we considered that the combination of NVP-AUY922-AG with fludarabine might resensitize CLL cells to the effects of fludarabine. In keeping with this hypothesis, the combination of NVP-AUY922-AG and fludarabine was highly synergistic (mean CI=0.110.06) and this synergy was enhanced in co-culture (mean CI=0.06±0.08). Furthermore, the combination maintained the decrease in MCL1, CFLAR and BIRC5 transcription suggesting that the ability of NVP-AUY922-AG to modulate expression of these genes may contribute to the efficacy of this drug under cytoprotective co-culture conditions and for its remarkable synergy with fludarabine. Taken together these findings indicate that Hsp90 inhibition is an attractive therapeutic strategy in CLL.

Targeting the microenvironment in chronic lymphocytic leukemia offers novel therapeutic options

Chronic lymphocytic leukemia (CLL) cells display features consistent with a defect in apoptosis and exhibit prolonged survival in vivo. Survival of these malignant cells is influenced by interactions with non-leukemic cells located in permissive niches in lymphoid organs. Leukemic cells subvert the normal architecture of the lymphoid organs, recruiting stromal cells, dendritic cells and T lymphocytes, all reported as playing active roles in the survival and proliferation of CLL. The same survival-promoting environment also rescues/protects leukemic cells from cytotoxic therapies, giving way to disease relapse. This review summarizes and discusses current knowledge about the intricate network of soluble and cell-bound signals regulating the life and death of CLL cells in different districts. At the same time, it seeks to hone in on which discrete molecular elements are best suited as targets for treating this still incurable disease.

Disruption of BIRC3 associates with fludarabine chemorefractoriness in TP53 wild-type chronic lymphocytic leukemia

The genetic lesions identified to date do not fully recapitulate the molecular pathogenesis of chronic lymphocytic leukemia (CLL) and do not entirely explain the development of severe complications such as chemorefractoriness. In the present study, BIRC3, a negative regulator of noncanonical NF-κB signaling, was investigated in different CLL clinical phases. BIRC3 lesions were absent in monoclonal B-cell lymphocytosis (0 of 63) and were rare in CLL at diagnosis (13 of 306, 4%). Conversely, BIRC3 disruption selectively affected 12 of 49 (24%) fludarabine-refractory CLL cases by inactivating mutations and/or gene deletions that distributed in a mutually exclusive fashion with TP53 abnormalities. In contrast to fludarabine-refractory CLL, progressive but fludarabine-sensitive patients were consistently devoid of BIRC3 abnormalities, suggesting that BIRC3 genetic lesions associate specifically with a chemorefractory phenotype. By actuarial analysis in newly diagnosed CLL (n = 306), BIRC3 disruption identified patients with a poor outcome similar to that associated with TP53 abnormalities and exerted a prognostic role that was independent of widely accepted clinical and genetic risk factors. Consistent with the role of BIRC3 as a negative regulator of NF-κB, biochemical studies revealed the presence of constitutive noncanonical NF-κB activation in fludarabine-refractory CLL patients harboring molecular lesions of BIRC3. These data identify BIRC3 disruption as a recurrent genetic lesion of high-risk CLL devoid of TP53 abnormalities.

Fluorinated amino-derivatives of the sesquiterpene lactone, parthenolide, as (19)f NMR probes in deuterium-free environments

The design, synthesis, and biological activity of fluorinated amino-derivatives of the sesquiterpene lactone, parthenolide, are described. A fluorinated aminoparthenolide analogue with biological activity similar to the parent natural product was discovered, and its X-ray structure was obtained. This lead compound was then studied using (19)F NMR in the presence and absence of glutathione to obtain additional mechanism of action data, and it was found that the aminoparthenolide eliminates amine faster in the presence of glutathione than in the absence of glutathione. The exact changes in concentrations of fluorinated compound and amine were quantified by a concentration-reference method using (19)F NMR; a major benefit of applying this strategy is that no deuterated solvents or internal standards are required to obtain accurate concentrations. These mechanistic data with glutathione may contribute to the conversion of the amino-derivative to parthenolide, the active pharmacological agent, in glutathione-rich cancer cells.

NF-κB mediates radio-sensitization by the PARP-1 inhibitor, AG-014699

The stress inducible transcription factor, NF-κB induces genes involved in proliferation and apoptosis. Aberrant NF-κB activity is common in cancer and contributes to therapeutic-resistance. Poly(ADP-ribose) polymerase-1 (PARP-1) is activated during DNA strand break repair and is a known transcriptional co-regulator. Here, we investigated the role of PARP-1 function during NF-κB activation using p65 siRNA, PARP siRNA or the potent PARP-1 inhibitor, AG-014699. Survival and apoptosis assays showed that NF-κB p65^−/− cells were more sensitive to ionizing radiation (IR) than p65^+/+ cells. Co-incubation with p65 siRNA, PARP siRNA or AG-014699 radio-sensitized p65^+/+, but not p65^−/− cells, demonstrating that PARP-1 mediates its effects on survival via NF-κB. Single strand break (SSB) repair kinetics, and the effect SSB repair inhibition by AG-014699 were similar in p65^+/+ and p65^−/− cells. Since preventing SSB repair did not radio-sensitize p65^−/− cells, we conclude that radio-sensitization by AG-014699 is due to downstream inhibition of NF-κB activation, and independent of SSB repair inhibition. PARP-1 catalytic activity was essential for IR-induced p65 DNA binding and NF-κB-dependent gene transcription, whereas for TNF-α treated cells, PARP-1 protein alone was sufficient. We hypothesize that this stimulus-dependent differential is mediated via stimulation of the Poly(ADP-ribose) polymer, which was induced following IR, not TNF-α. Targeting DNA-damage activated NF-κB using AG-014699 may therefore overcome toxicity observed with classical NF-κB inhibitors without compromising other vital inflammatory functions. These data highlight the potential of PARP-1 inhibitors to overcome NF-κB-mediated therapeutic resistance and widens the spectrum of cancers in which these agents may be utilized.

Personalizing treatment for chronic lymphocytic leukemia

Over the past few years, more effective therapies have emerged in the treatment of chronic lymphocytic leukemia (CLL); these are mainly combinations of immunotherapy with fludarabine-based regimens. Despite the higher response rates obtained with these more intensive treatments, they may not always be applicable. Patients with several comorbidities have an increased toxicity with these newer therapies. Effective tools to distinguish between fit and nonfit patients and new therapeutic approaches suitable for fragile patients with CLL are therefore necessary. Moreover, there is still a subset of patients who are refractory to standard fludarabine-based treatments who continue to have very poor survival. Efforts to understand the mechanisms of resistance to treatment in order to develop new therapeutic agents for those patients are mandatory. Finally, advances in the knowledge of the pathogenesis of CLL are promoting the emergence of drugs directed to new biological targets of this disease. Consequently, trials exploring the toxicity profile and efficacy of these new therapeutic agents, alone or in combination with standard treatments, are warranted.

Aberrantly activated anti-apoptotic signalling mechanisms in chronic lymphocytic leukaemia cells: clues to the identification of novel therapeutic targets

Chronic lymphocytic leukaemia (CLL) is the commonest haematological malignancy in the western world and is incurable by cytotoxic therapy. Considerable research effort has identified the signal transduction pathways in CLL cells that contribute to anti-apoptotic signalling. Some pathways are constitutively activated in CLL cells but upregulated in normal cells only when protein tyrosine kinases (PTKs) are activated by ligands. This review describes which PTKs are aberrantly activated in CLL cells and are potential targets for inhibition. Additional potential targets within pathways downstream of these PTKs include Mek/Erk, mTorc1, protein kinase C, PI-3 kinase/Akt, nuclear factor-κB and cyclin-dependent protein kinase. Numerous studies have identified chemical agents and antibodies that selectively kill CLL cells, irrespective of their genetic resistance to conventional chemotherapeutic agents, and which can overcome cytoprotective microenvironmental signalling. These studies have resulted in identification of novel therapies, some of which are currently undergoing clinical trials. In vitro and animal model studies and clinical trials could determine which inhibitors of which targets are the likely to be most effective and least toxic either singly or in combination.

The novel NF-κB inhibitor IMD-0354 induces apoptosis in chronic lymphocytic leukemia

Nuclear factor-κB (NF-κB) is an important regulator of cell survival and has been shown to be constitutively active in chronic lymphocytic leukemia (CLL) cells. Recently, a novel NF-κB inhibitor, IMD-0354 (N-(3, 5-bis-trifluoromethyl-phenyl)-5-chloro-2-hydroxy-benzamide), was shown to specifically inhibit the phosphorylation of IκBα by IkB kinases, thus preventing NF-κB release. In this study, we investigated if IMD-0354 can inhibit NF-κB activation and induce apoptosis in CLL cells in vitro. The rate of increase in apoptosis, drug sensitivity and DNA-binding activity of NF-κB were studied using Annexin V stainings, the fluorometric microculture cytotoxicity assay and electrophoretic mobility shift assay, respectively. Finally, the impact of IMD-0354 treatment on the expression of a set of apoptosis-related genes was investigated. The results clearly show that IMD-0354 induced apoptosis (mean 26%, range 8–48%) in CLL cells, independent of immunoglobulin heavy variable (IGHV) gene mutational status, and showed a dose-dependent cytotoxic effect. IMD-0354 treatment also significantly lowered the DNA-binding activity of NF-κB in CLL cells. In addition, we identified differences in expression levels of pro- and antiapoptotic genes following IMD-0354 treatment. In summary, our novel findings show that IMD-0354 can induce apoptosis in CLL cells, and thus merits further investigation as an anticancer agent in vivo.

Moving from prognostic to predictive factors in chronic lymphocytic leukaemia (CLL)

Many prognostic factors have been identified in chronic lymphocytic leukaemia (CLL). Based on the assessment of B cell receptor (BCR) structure and function, a subdivision into subtypes is possible (e.g., immunoglobulin heavy chain variable gene segment (IGHV) unmutated and mutated, V3-21 usage) with distinct biological and clinical characteristics. Recurrent genomic aberrations (i.e., 11q and 17p deletion) and gene mutations (i.e., TP53 and ATM) help to define biological and clinical subgroups. In addition, serum markers (e.g., thymidine kinase (TK) and beta2-microglobulin (beta2-MG)), cellular markers (e.g., CD38 and ZAP70) and clinical staging have an impact on outcome in CLL. The biological characterisation of CLL has not only led to progress in outcome prediction but also has begun to be translated into novel treatment strategies. Nonetheless, most factors associated with prognosis have not been thoroughly interrogated for their predictive value in the light of different therapeutic approaches. With a growing number of agents acting on specific biological targets and being used in different clinical situations, the future is likely to bring the identification of predictive factors in CLL.

c-Abl regulates Mcl-1 gene expression in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (CLL) is a malignancy characterized by clonal expansion of mature B cells that are resistant to apoptosis. This resistance to apoptosis partly results from Mcl-1 expression because high levels of this protein in CLL cells correlate with poor disease prognosis and resistance to chemotherapy. Thus, understanding the mechanism(s) regulating Mcl-1 expression in CLL cells may be useful in the development of new therapies for this incurable disease. In the present study, we show a strong relationship between c-Abl and Mcl-1 expression in CLL cells. We show that treatment of CLL cells with Abl-specific siRNA or with imatinib, to inhibit c-Abl activity, results in the down-regulation of Mcl-1 protein and mRNA. A major regulator of Mcl-1 gene expression is STAT3. Our data show that CLL cells expressing high levels of c-Abl also show elevated levels of phospho-STAT3, and that STAT3 phosphorylation in CLL cells is dependent on c-Abl activity. However, STAT3 phosphorylation by c-Abl requires activation of nuclear factor-κB, secretion of autocrine interleukin-6, and active protein kinase C. Taken together, our data demonstrate the mechanism involved in c-Abl regulation of Mcl-1 expression in CLL cells, and suggest that c-Abl inhibition has therapeutic application in the treatment of this disease.

Interaction with vascular endothelium enhances survival in primary chronic lymphocytic leukemia cells via NF-kappaB activation and de novo gene transcription

Chronic lymphocytic leukemia (CLL) cells rapidly undergo apoptosis in vitro, suggesting that the in vivo microenvironment provides crucial antiapoptotic signals. Overexpression of the antiapoptotic proteins Bcl-2 and Mcl-1 is a hallmark of CLL, and their expression is further enhanced in the lymphoid tissues. However, the high levels of Mcl-1 found in peripheral blood samples, coupled with its short half-life, led us to hypothesize that it must be actively maintained in the peripheral circulation. Coculture of CLL cells with human vascular endothelial cells significantly enhanced tumor cell survival, an effect that was not observed with normal B cells. This was associated with elevated levels of the antiapoptotic proteins Bcl-2, Mcl-1, and Bcl-X(L) and marked increased expression of CD38 and CD49d, both of which are associated with clinically aggressive disease. Because CD38, CD49d, and some Bcl-2 family genes are transcriptional targets for NF-κB, we assessed NF-κB activation following coculture with endothelial cells. DNA binding of the NF-κB subunit Rel A was significantly increased and strongly correlated with changes in transcription of CD38, CD49d, BCL2, MCL1, and BCLXL, effects that were reversed by a peptide inhibitor of Rel A. These effects were not observed following coculture with nonendothelial cell lines. Therefore, CLL cells receive specific survival signals following interaction with endothelial cells mediated through the activation of NF-κB and the induction of downstream target genes. This type of interaction in the peripheral vasculature may explain the constitutive NF-κB activation and the overexpression of Bcl-2 family proteins commonly seen in this disease.

The NF (Nuclear factor)-κB inhibitor parthenolide interacts with histone deacetylase inhibitors to induce MKK7/JNK1-dependent apoptosis in human acute myeloid leukaemia cells

Interactions between the nuclear factor (NF)-κB inhibitor parthenolide and the pan-histone deacetylase inhibitors (HDACIs) vorinostat and LBH589 were investigated in human acute myeloid leukaemia (AML) cells, including primary AML blasts. Co-administration of parthenolide blocked HDACI-mediated phosphorylation/activation of IKK and RelA/p65 in association with increased JNK1 activation in various AML cell types. These events were accompanied by an increase in apoptosis in multiple AML cell lines (e.g. U937, HL-60, NB4, MV-4-11, and MOLM-13). Significantly, parthenolide also increased HDACI-mediated cell death in haematopoietic cells transduced with the MLL-MLLT1 fusion gene, which exhibit certain leukaemia-initiating cell characteristics, as well as primary AML blasts. Exposure to parthenolide/HDACI regimens clearly inhibited the growth of AML-colony-forming units but was relatively sparing toward normal haematopoietic progenitors. Notably, blockade of c-Jun N-terminal kinase (JNK) signalling by either pharmacological inhibitors or genetic means (e.g. dominant-negative JNK1 or JNK1 shRNA) diminished parthenolide/HDACI-mediated lethality. Moreover, dominant-negative MKK7, but not dominant-negative MKK4/SEK1, blocked JNK1 activation and apoptosis induced by parthenolide/HDACI regimens. Together, these findings indicate that parthenolide potentiates HDACI lethality in human AML cells through a process involving NF-κB inhibition and subsequent MKK7-dependent activation of the SAPK/JNK pathway. They also raise the possibility that this strategy may target leukaemic progenitor cells.

17-DMAG targets the nuclear factor-kappaB family of proteins to induce apoptosis in chronic lymphocytic leukemia: clinical implications of HSP90 inhibition

The HSP90 client chaperone interaction stabilizes several important enzymes and antiapoptotic proteins, and pharmacologic inhibition of HSP90 results in rapid client protein degradation. Therefore, HSP90 inhibition is an attractive therapeutic approach when this protein is active, a phenotype commonly observed in transformed but not normal cells. However, preclinical studies with HSP90 inhibitors such as 17-AAG demonstrated depletion of only a subset of client proteins and very modest tumor cytotoxicity in chronic lymphocytic leukemia (CLL) cells. Herein, we describe another HSP90 inhibitor, 17-DMAG, which is cytotoxic to CLL but not normal lymphocytes. Treatment with 17-DMAG leads to depletion of the HSP90 client protein IKK, resulting in diminished NF-kappaB p50/p65 DNA binding, decreased NF-kappaB target gene transcription, and caspase-dependent apoptosis. Furthermore, treatment with 17-DMAG significantly decreased the white blood cell count and prolonged the survival in a TCL1-SCID transplant mouse model. The ability of 17-DMAG to function as an NF-kappaB inhibitor is of great interest clinically, as few currently available CLL drugs target this transcription factor. Therefore, the effect of 17-DMAG on NF-kappaB signaling pathways represents a novel therapy warranting further clinical pursuit in this and other B-cell lymphoproliferative disorders.

NF-kappaB as a therapeutic target in chronic lymphocytic leukemia

IMPORTANCE OF THE FIELD

NF-kappaB includes a family of transcription factors that play a critical role in the biology of normal lymphocytes and it is aberrantly activated in chronic lymphocytic leukemia (CLL) cells. Here, we review the role of constitutive NF-kappaB activation in CLL pathogenesis and its potential as a therapeutic target for CLL treatment.

AREAS COVERED IN THIS REVIEW

This review highlights the different strategies reported to inhibit NF-kappaB signaling in CLL cells. They include both IkappaB kinase inhibitors and several natural compounds that act at different steps of the pathway.

WHAT THE READER WILL GAIN

Targeting NF-kappaB leads to apoptosis of CLL cells, corroborating the role of NF-kappaB in the survival and clonal expansion of these tumoral cells. Moreover, several studies confirmed a synergistic effect between NF-kappaB inhibitors and other antitumoral agents and that inhibition of NF-kappaB could overcome the microenvironmental protection of CLL cells.

TAKE HOME MESSAGE

NF-kappaB is a relevant target in CLL and inhibitors of this prosurvival pathway, alone or in combination, represent a novel therapeutic strategy for the treatment of CLL patients.

New agents for AML and MDS

The heterogeneity of acute myeloid leukaemia (AML) and myelodysplastic syndromes (MDS) has led to a multiplicity of treatments, from cytotoxic agents to signal transduction modulators, cell-cycle inhibitors and epigenetic therapies. While some have shown promising initial results, the outlook for AML patients, particularly older and relapsed patients, as well as patients whose cells exhibit certain adverse chromosomal abnormalities or mutant oncoproteins, continues to be grim. Combination chemotherapy using new agents that act at a number of different levels may provide the greatest potential for successful future therapies. A select number of new agents, approaches and combinations are reviewed here.

NF-kappaB activation mediates resistance to IFN beta in MLL-rearranged acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) harboring the t(4;11) translocation is associated with a very poor prognosis; innovative treatment strategies are required to improve the current 5-year survival rate of 30-40%. Interferon beta (IFN beta) has shown promise in the treatment of both solid and hematologic malignancies, although the short half-life and toxicity associated with high doses have limited its clinical utility. To overcome these limitations, we investigated the effect of continuous, gene transfer-mediated delivery of IFN beta using adeno-associated virus (AAV)-mediated expression, on ALL cells with the t(4;11) translocation. We found that this method of IFN beta delivery resulted in complete remission of leukemia in a murine model. However, leukemic cells eventually became resistant to IFN beta and relapse was observed. Activation of NF-kappaB was identified as a mechanism for IFN beta resistance, and inhibition of NF-kappaB activity in resistant cells sensitized cells to IFN beta. IFN beta combined with agents that inhibit NF-kappaB could have therapeutic potential in the treatment of children with mixed lineage leukemia subtype ALL.

NF-kappaB as a prognostic marker and therapeutic target in chronic lymphocytic leukemia

Chronic lymphocytic leukemia is the most common adult leukemia and is currently incurable with conventional chemotherapeutic agents. Over the last few years, significant discoveries have been made regarding the biology that underpins this disease. These new insights have allowed us to develop more rational prognostic tools and identify promising novel therapeutic targets. In this review, we highlight the importance of both constitutive and inducible DNA binding of the transcription factor NF-kappaB in chronic lymphocytic leukemia. We describe the current knowledge regarding the activity and function of specific NF-kappaB subunits in this disease, and discuss the complex mechanisms that regulate NF-kappaB activation in vivo. In addition, we provide compelling evidence for the utility of the NF-kappaB subunit, Rel A, as a prognostic marker and as a therapeutic target in this disease, and we also describe how this protein may contribute to the drug resistance commonly encountered with this condition.

Inflammation and cancer: how friendly is the relationship for cancer patients?

Evidence has emerged in the last two decades that at the molecular level most chronic diseases, including cancer, are caused by a dysregulated inflammatory response. The identification of transcription factors such as NF-kappaB, AP-1 and STAT3 and their gene products such as tumor necrosis factor, interleukin-1, interleukin-6, chemokines, cyclooxygenase-2, 5 lipooxygenase, matrix metalloproteases, and vascular endothelial growth factor, adhesion molecules and others have provided the molecular basis for the role of inflammation in cancer. These inflammatory pathways are activated by tobacco, stress, dietary agents, obesity, alcohol, infectious agents, irradiation, and environmental stimuli, which together account for as much as 95% of all cancers. These pathways have been implicated in transformation, survival, proliferation, invasion, angiogenesis, metastasis, chemoresistance, and radioresistance of cancer, so much so that survival and proliferation of most types of cancer stem cells themselves appear to be dependent on the activation of these inflammatory pathways. Most of this evidence, however, is from preclinical studies. Whether these pathways have any role in prevention, progression, diagnosis, prognosis, recurrence or treatment of cancer in patients, is the topic of discussion of this review. We present evidence that inhibitors of inflammatory biomarkers may have a role in both prevention and treatment of cancer.

Aminoparthenolides as novel anti-leukemic agents: Discovery of the NF-kappaB inhibitor, DMAPT (LC-1)

A series of aminoparthenolide analogs (6-37) were synthesized and evaluated for their anti-leukemic activity. Eight compounds exhibited good anti-leukemic activity with LD(50)'s in the low microM range (1.5-3.0microM). Compounds 16, 24 and 30 were the most potent compounds in the series, causing greater than 90% cell death at 10microM concentration against primary AML cells in culture, with LD(50) values of 1.7, 1.8 and 1.6microM.