Leukemic target susceptibility to natural killer cytotoxicity: relationship with BCR-ABL expression

NK cells sense tumors, course of disease and treatments: Consequences for NK-based therapies

The recent findings on NK activation indicate that these cells are important antitumor effectors. NK cells participate in the graft-vs.-leukemia effect to control the relapse in leukemic patients transplanted with allogeneic hematopoietic stem cells. In various tumors, correlation between NK cell infiltrates and prognosis were reported. However, tumor-infiltrating NK cells are yet poorly characterized. We here summarize our results and the recent studies of the literature on tumor-infiltrating NK cells, and discuss the impact of these novel insights into NK cell responses against tumors for the design of NK cell-based therapies.

Targeting Oncogenic Nuclear Factor Kappa B Signaling with Redox-Active Agents for Cancer Treatment

SIGNIFICANCE

Nuclear factor kappa B (NF-κB) signaling is essential under physiologically relevant conditions. However, aberrant activation of this pathway plays a pertinent role in tumorigenesis and contributes to resistance. Recent Advances: The importance of the NF-κB pathway means that its targeting must be specific to avoid side effects. For many currently used therapeutics and those under development, the ability to generate reactive oxygen species (ROS) is a promising strategy.

CRITICAL ISSUES

As cancer cells exhibit greater ROS levels than their normal counterparts, they are more sensitive to additional ROS, which may be a potential therapeutic niche. It is known that ROS are involved in (i) the activation of NF-κB signaling, when in sublethal amounts; and (ii) high levels induce cytotoxicity resulting in apoptosis. Indeed, ROS-induced cytotoxicity is valuable for its capabilities in killing cancer cells, but establishing the potency of ROS for effective inhibition of NF-κB signaling is necessary. Indeed, some cancer treatments, currently used, activate NF-κB and may stimulate oncogenesis and confer resistance.

FUTURE DIRECTIONS

Thus, combinatorial approaches using ROS-generating agents alongside conventional therapeutics may prove an effective tactic to reduce NF-κB activity to kill cancer cells. One strategy is the use of thiosemicarbazones, which form redox-active metal complexes that generate high ROS levels to deliver potent antitumor activity. These agents also upregulate the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), which functions as an NF-κB signaling inhibitor. It is proposed that targeting NF-κB signaling may proffer a new therapeutic niche to improve the efficacy of anticancer regimens.

The BCR-ABL/NF-κB signal transduction network: a long lasting relationship in Philadelphia positive Leukemias

The Nuclear Factor-kappa B (NF-κB) family of transcription factors plays a key role in cancer pathogenesis due to the ability to promote cellular proliferation and survival, to induce resistance to chemotherapy and to mediate invasion and metastasis. NF-κB is recruited through different mechanisms involving either canonical (RelA/p50) or non-canonical pathways (RelB/p50 or RelB/p52), which transduce the signals originated from growth-factors, cytokines, oncogenic stress and DNA damage, bacterial and viral products or other stimuli. The pharmacological inhibition of the NF-κB pathway has clearly been associated with significant clinical activity in different cancers. Almost 20 years ago, NF-κB was described as an essential modulator of BCR-ABL signaling in Chronic Myeloid Leukemia and Philadelphia-positive Acute Lymphoblastic Leukemia. This review summarizes the role of NF-κB in BCR-ABL-mediated leukemogenesis and provides new insights on the long lasting BCR-ABL/NF-κB connection.

N-Myc-Interacting Protein Negatively Regulates TNF-α-Induced NF-κB Transcriptional Activity by Sequestering NF-κB/p65 in the Cytoplasm

NF-κB is a major regulator of gene transcription involved in immune, inflammation, apoptosis and stress responses. However, the regulation of NF-κB is not completely understood. Here, we report that the N-Myc and STATs Interactor (NMI), an IFN-inducible protein, is an important negative regulator of NF-κB activity. We found that NMI negatively regulates TNF-α-induced IL-6 and IL-1β production in HeLa cells. Overexpression of NMI inhibits NF-κB transcriptional activity, in contrast, depletion of NMI by shRNA increases NF-κB transcriptional activity. Mechanistically, NMI associates with NF-κB/p65 and inhibits NF-κB/p65 nuclear translocation and thereby negatively regulates NF-κB/p65 transcriptional activity. Taken together, our results demonstrate that NMI modulates the NF-κB signaling pathway by sequestering NF-κB/p65 in the cytoplasm, resulting in reduced IL-6 and IL-1β production after TNF-α stimulation. Treatment with IFNα in the presence of NMI leads to increased apoptosis in tumor cells. These findings reveal a novel mechanism by which NMI regulates NF-κB activity.

Multidrug-resistant cancer cells and cancer stem cells hijack cellular systems to circumvent systemic therapies, can natural products reverse this?

Chemotherapy is one of the most effective and broadly used approaches for cancer management and many modern regimes can eliminate the bulk of the cancer cells. However, recurrence and metastasis still remain a major obstacle leading to the failure of systemic cancer treatments. Therefore, to improve the long-term eradication of cancer, the cellular and molecular pathways that provide targets which play crucial roles in drug resistance should be identified and characterised. Multidrug resistance (MDR) and the existence of tumor-initiating cells, also referred to as cancer stem cells (CSCs), are two major contributors to the failure of chemotherapy. MDR describes cancer cells that become resistant to structurally and functionally unrelated anti-cancer agents. CSCs are a small population of cells within cancer cells with the capacity of self-renewal, tumor metastasis, and cell differentiation. CSCs are also believed to be associated with chemoresistance. Thus, MDR and CSCs are the greatest challenges for cancer chemotherapy. A significant effort has been made to identify agents that specifically target MDR cells and CSCs. Consequently, some agents derived from nature have been developed with a view that they may overcome MDR and/or target CSCs. In this review, natural products-targeting MDR cancer cells and CSCs are summarized and clustered by their targets in different signaling pathways.

Methods of ex vivo expansion of human cord blood cells: challenges, successes and clinical implications

More than 40,000 unrelated cord blood transplantations (UCBT) have been performed worldwide as treatment for patients with malignant or non-malignant life threatening hematologic disorders. However, low absolute numbers of hematopoietic stem and progenitor cells (HSPCs) within a single cord blood unit has remained a limiting factor for this transplantation modality, particularly in adult recipients. Further, because UCB contains low numbers of mostly naïve T cells, immune recovery after UCBT is slow, predisposing patients to severe infections. Other causes of UCBT failure has included graft-versus-host disease (GVHD) and relapse of the underlying disease. In this article, we first review the current landscape of cord blood engineering aimed at improving engraftment. This includes approaches of UCB-HSPCs expansion and methods aimed at improving UCB-HSCPs homing. We then discuss recent approaches of cord blood engineering developed to prevent infection [generation of multivirus-specific cytotoxic T cells (VSTs) from UCB], relapse [transduction of UCB-T cells with tumor-specific chimeric receptor antigens (CARs)] and GVHD (expansion of regulatory T cells from UCB). Although many of these techniques of UCB engineering remain currently technically challenging and expensive, they are likely to revolutionize the field of UCBT in the next decades.

Possible molecular targets for therapeutic applications of caffeic acid phenethyl ester in inflammation and cancer

Of the various derivatives of caffeic acid, caffeic acid phenethyl ester (CAPE) is a hydrophobic, bioactive polyphenolic ester obtained from propolis extract. The objective in writing this review article was to summarize all published studies on therapeutics of CAPE in inflammation and cancer to extract direction for future research. The possible molecular targets for the action of CAPE, include various transcription factors such as nuclear factor-κB, tissue necrosis factor-α, interleukin-6, cyclooxygenase-2, Nrf2, inducible nitric oxide synthase, nuclear factor of activated T cells, hypoxia-inducible factor-1α, and signal transducers and activators of transcription. Based on the valuable data on its therapeutics in inflammation and cancer, clinical studies of CAPE should also be conducted to explore its toxicities, if any.

Modeling BCR/ABL-driven malignancies in the mouse

In this chapter, we describe model systems to study leukemia driven by the Abelson oncogene. In people, the Abelson oncogene results from the chromosomal translocation t(9;22)(q34;q11) that is found in more than 90 % of all human chronic myeloid leukemia (CML) patients and in 20-25 % of patients suffering from acute lymphoid leukemia (ALL). This translocation is also called Philadelphia chromosome and encodes the BCR/ABL oncogene, a constitutive active tyrosine kinase. BCR/ABL renders hematopoietic cells independent from exogenous growth-stimulatory signals by continuously engaging signaling pathways including JAK-STAT signaling and the MAPK pathway. The enforced expression of BCR/ABL suffices to transform hematopoietic cells which made it to one of the best studied model systems in the field. Here we present methods to study BCR/ABL-triggered leukemia and solid lymphoid tumor formation.

Differential and opposing effects of imatinib on LPS- and ventilator-induced lung injury

Endothelial dysfunction underlies the pathophysiology of vascular disorders such as acute lung injury (ALI) syndromes. Recent work has identified the Abl family kinases (c-Abl and Arg) as important regulators of endothelial cell (EC) barrier function and suggests that their inhibition by currently available pharmaceutical agents such as imatinib may be EC protective. Here we describe novel and differential effects of imatinib in regulating lung pathophysiology in two clinically relevant experimental models of ALI. Imatinib attenuates endotoxin (LPS)-induced vascular leak and lung inflammation in mice but exacerbates these features in a mouse model of ventilator-induced lung injury (VILI). We next explored these discrepant observations in vitro through investigation of the roles for Abl kinases in cultured lung EC. Imatinib attenuates LPS-induced lung EC permeability, restores VE-cadherin junctions, and reduces inflammation by suppressing VCAM-1 expression and inflammatory cytokine (IL-8 and IL-6) secretion. Conversely, in EC exposed to pathological 18% cyclic stretch (CS) (in vitro model of VILI), imatinib decreases VE-cadherin expression, disrupts cell-cell junctions, and increases IL-8 levels. Downregulation of c-Abl expression with siRNA attenuates LPS-induced VCAM-1 expression, whereas specific reduction of Arg reduces VE-cadherin expression in 18% CS-challenged ECs to mimic the imatinib effects. In summary, imatinib exhibits pulmonary barrier-protective and anti-inflammatory effects in LPS-injured mice and lung EC; however, imatinib exacerbates VILI as well as dysfunction in 18% CS-EC. These findings identify the Abl family kinases as important modulators of EC function and potential therapeutic targets in lung injury syndromes.

Loss of STAT3 in Lymphoma Relaxes NK Cell-Mediated Tumor Surveillance

The transcription factors and proto-oncogenes STAT3 and STAT5 are highly activated in hematological malignancies and represent promising therapeutic targets. Whereas the importance of STAT5 as tumor promoter is beyond doubt, the role of STAT3 in hematological cancers is less well understood. Both, enforced as well as attenuated expression of STAT3 were reported in hematopoietic malignancies. Recent evidence implicates STAT3 as key player for tumor immune surveillance as it both mediates the production of and response to inflammatory cytokines. Here we investigated the effects of STAT3 deletion in a BCR/ABL-induced lymphoma model, which is tightly controlled by natural killer (NK) cells in vivo. Upon STAT3 deletion tumor growth is significantly enhanced when compared to STAT3-expressing controls. The increased tumor size upon loss of STAT3 was accompanied by reduced NK cell infiltration and decreased levels of the cytokine IFN-γ and the chemokine RANTES. Upon transplantation into NK cell-deficient mice differences in lymphoma size were abolished indicating that STAT3 expression in the tumor cells controls NK cell-dependent tumor surveillance. Our findings indicate that STAT3 inhibition in lymphoma patients will impair NK cell-mediated tumor surveillance, which needs to be taken into account when testing STAT3 inhibitors in preclinical or clinical trials.

Iron chelation in the treatment of cancer: a new role for deferasirox?

Iron plays a crucial role in a number of metabolic pathways including oxygen transport, DNA synthesis, and ATP generation. Although insufficient systemic iron can result in physical impairment, excess iron has also been implicated in a number of diseases including ischemic heart disease, diabetes, and cancer. Iron chelators are agents which bind iron and facilitate its excretion. Experimental iron chelators have demonstrated potent anti-neoplastic properties in a number of cancers in vitro. These agents have yet to be translated into clinical practice, however, largely due to the significant side effects encountered in pre-clinical models. A number of licensed chelators, however, are currently in clinical use for the treatment of iron overload associated with certain non-neoplastic diseases. Deferasirox is one such agent and the drug has shown significant anti-tumor effects in a number of in vitro and in vivo studies. Deferasirox is orally administered and has demonstrated a good side effect profile in clinical practice to date. It represents an attractive agent to take forward into clinical trials of iron chelators as anti-cancer agents.

Novel immune modulators used in hematology: impact on NK cells

There is a wide range of important pharmaceuticals used in treatment of cancer. Besides their known effects on tumor cells, there is growing evidence for modulation of the immune system. Immunomodulatory drugs (IMiDs^®) play an important role in the treatment of patients with multiple myeloma or myelodysplastic syndrome and have already demonstrated antitumor, anti-angiogenic, and immunostimulating effects, in particular on natural killer (NK) cells. Tyrosine kinase inhibitors are directly targeting different kinases and are known to regulate effector NK cells and expression of NKG2D ligands (NKG2DLs) on tumor cells. Demethylating agents, histone deacetylases, and proteasome inhibitors interfere with the epigenetic regulation and protein degradation of malignant cells. There are first hints that these drugs also sensitize tumor cells to chemotherapy, radiation, and NK cell-mediated cytotoxicity by enhanced expression of TRAIL and NKG2DLs. However, these pharmaceuticals may also impair NK cell function in a dose- and time-dependent manner. In summary, this review provides an update on the effects of different novel molecules on the immune system focusing NK cells.

NK cells are dysfunctional in human chronic myelogenous leukemia before and on imatinib treatment and in BCR-ABL-positive mice

Although BCR-ABL+ stem cells in chronic myeloid leukemia (CML) resist elimination by targeted pharmacotherapy in most patients, immunological graft-versus-leukemia effects can cure the disease. Besides cytotoxic T cells, natural killer (NK) cells may have a role in immune control of CML. Here, we explored the functionality of NK cells in CML patients and in a transgenic inducible BCR-ABL mouse model. Compared with controls, NK-cell proportions among lymphocytes were decreased at diagnosis of CML and did not recover during imatinib-induced remission for 10-34 months. Functional experiments revealed limited in vitro expansion of NK cells from CML patients and a reduced degranulation response to K562 target cells both at diagnosis and during imatinib therapy. Consistent with the results in human CML, relative numbers of NK1.1+ NK cells were reduced following induction of BCR-ABL expression in mice, and the defects persisted after BCR-ABL reversion. Moreover, target-induced degranulation by expanded BCR-ABL+ NK cells was compromised. We conclude that CML is associated with quantitative and functional defects within the NK-cell compartment, which is reproduced by induced BCR-ABL expression in mice. Further work will aim at identifying the mechanisms of NK-cell deficiency in CML and at developing strategies to exploit NK cells for immunotherapy.

Toll-like receptors and their role in carcinogenesis and anti-tumor treatment

Toll-like receptors (TLRs) have been described as major components of the innate immune system, recognizing the conserved molecular structures found in the large groups of pathogens called pathogen-associated molecular patterns (PAMPs). TLR expression is ubiquitous, from epithelial to immunocompetent cells. TLR ligation triggers several adapter proteins and downstream kinases, leading to the induction of key pro-inflammatory mediators but also anti-inflammatory and anti-tumor cytokines. The result of this activation goes beyond innate immunity to shape the adaptive responses against pathogens and tumor cells, and maintains host homeostasis via cell debris utilization. TLRs have already become potent targets in infectious disease treatment and vaccine therapy and in neoplastic disease treatment, due to their ability to enhance antigen presentation. However, some studies show the dual effect of TLR stimulation on malignant cells: they can be proapoptotic or promote survival under different conditions. It is therefore crucial to design further studies assessing the biology of these receptors in normal and transformed cells. The established role of TLRs in human disease therapy is based on TLR7 and TLR4 agonists, respectively for the novel treatment of some types of skin cancer and for the anti-hepatitis B virus vaccine. Some clinical trials involving TLR agonists as potent enhancers of the anti-tumor response in solid tumors have begun.

Aberrant constitutive activation of nuclear factor kappaB in glioblastoma multiforme drives invasive phenotype

Several recent studies have shown that aberrant constitutive activation of nuclear factor kappaB (NF-kappaB) is present in a variety of cancers including gliomas. NF-kappaB is known to play important roles in the physiological regulation of diverse cellular processes such as inflammation, growth and immunity. In contrast, aberrant activation of this latent transcription factor promotes cancer cell migration, invasion and resistance to chemotherapy. Here we show by electro-mobility shift assay (EMSA) and immuno-staining that constitutive NF-kappaB activation is present in various malignant glioma cell lines as well as in primary cultures derived from tumor tissue. This activation was not serum dependent and it led to high IL-8 gene transcription and protein production. Over-expression of an I-kappaB super-repressor (I-kappaB SR) transgene completely blocked constitutive NF-kappaB activation, nuclear localization and transcription of some but not all NF-kappaB regulated genes indicating that NF-kappaB signaling in glioma cells is I-kappaB dependent. Surprisingly, over-expression of IkappaBSR did not have any effect on the transcription levels of anti-apoptotic genes in these glioma cultures and cell lines. Down-regulation of NF-kappaB activation reduced invasion of glioma cells through matrigel. Collectively these data suggest that aberrant constitutive activation of NF-kappaB in glioblastoma cells promotes their invasive phenotype. Interruption of this aberrant NF-kappaB activity may help reduce the spread of this infiltrative tumor.

Inflammation, cancer and chemoresistance: taking advantage of the toll-like receptor signaling pathway

The association between chronic inflammation and cancer has long been observed. Furthermore, NF-kappaB activation and the subsequent production of cytokines, chemokines, growth factors, and antiapoptotic proteins has been found to be involved in cancer progression and chemoresistance. However, the signals inducing NF-kappaB in cancer cells are still not well understood. Here, we reviewed the association between chronic inflammation and cancer, the role of NF-kappaB and its inhibitors as potential anticancer drugs, and Toll-like receptors as possible signal initiators for NF-kappaB activation and inflammation-induced carcinogenesis and chemoresistance. Furthermore, we propose that, the stimulation of Toll-like receptors by microbial components and/or endogenous ligands may represent the initial signal promoting a proinflammatory environment that will enhance tumor growth and chemoresistance.

Targeting GSK-3: a promising approach for cancer therapy?

Glycogen synthase kinase (GSK)-3 has emerged as one of the most attractive therapeutic targets for the treatment of multiple neurological diseases, including Alzheimer's, stroke and bipolar disorders, as well as noninsulin-dependent diabetes mellitus and inflammation. Although the prominent role of GSK-3 in the adenomatous polyposis coli (APC)-beta-catenin destruction complex implies that inhibition of GSK-3 could possibly lead to tumor promotion through the activation of beta-catenin, several recent studies have shed new light on the activity of GSK-3 in cancer and provide insight into the molecular mechanisms by which it regulates tumor cell proliferation and survival of multiple human malignancies. In fact, GSK-3beta is a critical regulator of nuclear factor (NF)kappaB nuclear activity, suggesting that inhibition of GSK-3beta could be effective in the treatment of a wide variety of tumors with constitutively active NFkappaB. Herein, the authors will discuss the current understanding of the role of GSK-3 in human cancer and its potential as a therapeutic target.

Chronic myeloid leukemia and allogeneic natural killer cells: a surprising dialogue

Chronic myeloid leukemia (CML) is a clonal multilineage myeloproliferative disease of stem cell origin characterized by the presence of the Bcr/Abl oncoprotein, a constitutively active tyrosine kinase. The actual treatment of CML patients in chronic phase is the specific abl kinase inhibitor imatinib mesylate that induces 90% of cytogenetic responses in early-phase patients. However, resistance in long-term treated patients occurs and the allogeneic stem cell transplantation remains the only curative treatment in resistant patients. Despite recent reports outlining the role of allogeneic natural killer (NK) cells as potent antileukemic effectors, the mechanisms controlling the leukemic target recognition and lysis by activated NK cells have not been well identified. The authors' experimental data obtained on appropriate cellular models identify diverse mechanisms that could explain the increased NK-cell susceptibility of Bcr/Abl targets to NK-mediated lysis. They further delineate unexpected effects of the inhibition of the tyrosine kinase activity on the cross-talk between NK and CML leukemic cells. The consequences of such discoveries are discussed in the context of combined treatments with antikinases as well as adoptive cellular therapy approaches in myeloid leukemia patients.

BCR/ABL oncogene directly controls MHC class I chain-related molecule A expression in chronic myelogenous leukemia

MHC class I chain-related molecules (MIC) participate in immune surveillance of cancer through engagement of the NKG2D-activating receptor on NK and T cells. Decreased NKG2D expression and function upon chronic exposure to NKG2D ligands and/or soluble forms of MIC (sMIC) may participate in immune escape. In chronic myeloid leukemia, a malignancy caused by the BCR/ABL fusion oncoprotein, we showed cell surface expression of MICA on leukemic, but not healthy, donor hemopoietic CD34+ cells. At diagnosis, chronic myeloid leukemia patients had abnormally high serum levels of sMICA and weak NKG2D expression on NK and CD8+ T cells, which were restored by imatinib mesylate (IM) therapy. In the BCR/ABL+ cell line K562, IM decreased both surface MICA/B expression and NKG2D-mediated lysis by NK cells. Silencing BCR/ABL gene expression directly evidenced its role in the control of MICA expression. IM did not affect MICA mRNA levels, but decreased MICA protein production and release. Sucrose density gradient fractionation of K562 cytoplasmic extracts treated with IM showed a shift in the distribution of MICA mRNA from the polysomal toward the monosomal fractions, consistent with decreased translation. Among the major pathways activated by BCR/ABL that regulate translation, PI3K and mammalian target of rapamycin were shown to control MICA expression. These data provide evidence for direct control of MICA expression by an oncogene in human malignancy and indicate that posttranscriptional mechanisms may participate in the regulation of MICA expression.

Cytokines, NF-kappaB, microenvironment, intestinal inflammation and cancer

Inflammation and cancer have been viewed as closely linked for many years. This link is not merely a loose association but causative. In colorectal cancer (CRC), chronic inflammation as observed in inflammatory bowel (IBD) disease is a key predisposing factor and IBD-associated CRC comprises five percent of all CRCs. Although the molecular mechanisms linking IBD with CRC are not well understood, recent results obtained in preclinical models point to the transcription factor NF-kappaB as a central player. On the one hand, NF-kappaB regulates the expression of various cytokines and modulates the inflammatory processes in IBD. On the other, NF-kappaB stimulates the proliferation of tumor cells and enhances their survival through the regulation of anti-apoptotic genes. Furthermore, it has been clearly established that most carcinogens and tumor promoters activate NF-kappaB, while chemopreventive agents generally suppress this transcription factor. Actually, several lines of evidence suggest that activation of NF-kappaB may cause cancer. These include the finding that NF-kappaB genes can be oncogenes, and that this transcription factor controls apoptosis, cell-cycle progression and proliferation, and possibly also cell differentiation.

The Decreased Susceptibility of Bcr/Abl Targets to NK Cell-Mediated Lysis in Response to Imatinib Mesylate Involves Modulation of NKG2D Ligands, GM1 Expression, and Synapse Formation

Chronic myeloid leukemia is a clonal multilineage myeloproliferative disease of stem cell origin characterized by the presence of the Bcr/Abl oncoprotein, a constitutively active tyrosine kinase. In previous studies, we have provided evidence that Bcr/Abl overexpression in leukemic cells increased their susceptibility to NK-mediated lysis by different mechanisms. In the present study, using UT-7/9 cells, a high level Bcr/Abl transfectant of UT-7 cells, we show that the treatment of Bcr/Abl target by imatinib mesylate (IM), a specific Abl tyrosine kinase inhibitor, hampers the formation of the NK/target immunological synapse. The main effect of IM involves an induction of surface GM1 ganglioside on Bcr/Abl transfectants that prevents the redistribution of MHC-related Ag molecules in lipid rafts upon interaction with NK cells. IM also affects cell surface glycosylation of targets, as assessed by binding of specific lectins resulting in the subsequent modulation of their binding to lectin type NK receptor, particularly NKG2D. In addition, we demonstrate that the tyrosine kinase activity repression results in a decrease of MHC-related Ags-A/B and UL-16-binding protein expression on Bcr/Abl transfectants UT-7/9. We show that NKG2D controls the NK-mediated lysis of UT-7/9 cells, and IM treatment inhibits this activating pathway. Taken together, our results show that the high expression of Bcr/Abl in leukemic cells controls the expression of NKG2D receptor ligands and membrane GM1 via a tyrosine kinase-dependent mechanism and that the modulation of these molecules by IM interferes with NK cell recognition and cytolysis of the transfectants.

Cytokines, NF-kappaB, microenvironment, intestinal inflammation and cancer

Inflammation and cancer have been viewed as closely linked for many years. This link is not merely a loose association but causative. In colorectal cancer (CRC), chronic inflammation as observed in inflammatory bowel (IBD) disease is a key predisposing factor and IBD-associated CRC comprises five percent of all CRCs. Although the molecular mechanisms linking IBD with CRC are not well understood, recent results obtained in preclinical models point to the transcription factor NF-kappaB as a central player. On the one hand, NF-kappaB regulates the expression of various cytokines and modulates the inflammatory processes in IBD. On the other, NF-kappaB stimulates the proliferation of tumor cells and enhances their survival through the regulation of anti-apoptotic genes. Furthermore, it has been clearly established that most carcinogens and tumor promoters activate NF-kappaB, while chemopreventive agents generally suppress this transcription factor. Actually, several lines of evidence suggest that activation of NF-kappaB may cause cancer. These include the finding that NF-kappaB genes can be oncogenes, and that this transcription factor controls apoptosis, cell-cycle progression and proliferation, and possibly also cell differentiation.

BCR/ABL Promotes Dendritic Cell–Mediated Natural Killer Cell Activation

BCR/ABL fusion gene, encoding a paradigmatic tyrosine kinase involved in chronic myelogenous leukemia (CML), can modulate the expression of genes involved in natural killer (NK) cell target recognition. Recent reports outline the role of allogeneic antileukemic NK effectors in the graft-versus-leukemia effect but the regulation of NK cell activation in the setting of graft-versus-leukemia effect remains unknown. Here we show that dendritic cells derived from monocytes of CML patients are selectively endowed with NK cell stimulatory capacity in vitro. We further show, using a gene transfer approach in mouse bone marrow progenitors, that ABL/ABL is necessary to promote dendritic cell–mediated NK cell activation. The dendritic cell/NK cell cross-talk in ABL/ABL-induced CML seems unique because JunB or IFN consensus sequence binding protein loss of functions, associated with other myeloproliferative disorders, do not promote dendritic cell–mediated NK cell activation. NK cell activation by leukemic dendritic cells involves NKG2D activating receptors and is blocked by imatinib mesylate. Indeed, ABL/ABL translocation enhances the expression levels of the NKG2D ligands on dendritic cells, which is counteracted by imatinib mesylate. Altogether, the clonal ABL/ABL dendritic cells display the unique and selective ability to activate NK cells and may participate in the NK cell control of CML. This study also highlights the deleterious role of imatinib mesylate at the dendritic cell level for NK cell activation.

Altered IFNγ Signaling and Preserved Susceptibility to Activated Natural Killer Cell–Mediated Lysis of BCR/ABL Targets

Previous studies have shown that BCR/ABL oncogene, the molecular counterpart of the Ph1 chromosome, could represent a privileged target to natural killer (NK) cells. In the present study, we showed that activated peripheral NK cells killed high-level BCR/ABL transfectant UT-7/9 derived from the pluripotent hematopoietic cell line UT-7 with a high efficiency. To further define the mechanisms controlling BCR/ABL target susceptibility to NK-mediated lysis, we studied the effect of IFNgamma, a key cytokine secreted by activated NK cells, on the lysis of these targets. Treatment of UT-7, UT-7/neo, and low BCR/ABL transfectant UT-7/E8 cells with IFNgamma resulted in a dramatic induction of human leukocyte antigen class I (HLA-I) molecules and subsequently in their reduced susceptibility to NK-mediated cytolysis likely as a consequence of inhibitory NK receptors engagement. In contrast, such treatment neither affected HLA-I expression on transfectants expressing high level of BCR/ABL (UT-7/9) nor modulated their lysis by NK cells. Our data further show that the high-level BCR/ABL in UT-7/9 cells display an altered IFNgamma signaling, as evidenced by a decrease in IFN regulatory factor-1 (IRF-1) and signal transducers and activators of transcription (STAT) 1 induction and activation in response to IFNgamma, whereas this pathway is normal in UT-7 and UT-7/E8 cells. A decreased HLA-I induction and nuclear phospho-STAT1 nuclear translocation were also observed in blasts from most chronic myelogenous leukemia patients in response to IFNgamma. These results outline the crucial role of IFNgamma in the control of target cell susceptibility to lysis by activated NK cells and indicate that the altered response to IFNgamma in BCR/ABL targets may preserve these cells from the cytokine-induced negative regulatory effect on their susceptibility to NK-mediated lysis.

TYK2 is a key regulator of the surveillance of B lymphoid tumors

Aberrant activation of the JAK-STAT pathway has been implicated in tumor formation; for example, constitutive activation of JAK2 kinase or the enforced expression of STAT5 induces leukemia in mice. We show here that the Janus kinase TYK2 serves an opposite function. Mice deficient in TYK2 developed Abelson-induced B lymphoid leukemia/lymphoma as well as TEL-JAK2-induced T lymphoid leukemia with a higher incidence and shortened latency compared with WT controls. The cell-autonomous properties of Abelson murine leukemia virus-transformed (A-MuLV-transformed) TYK2(-/-) cells were unaltered, but the high susceptibility of TYK2(-/-) mice resulted from an impaired tumor surveillance, and accordingly, TYK2(-/-) A-MuLV-induced lymphomas were easily rejected after transplantation into WT hosts. The increased rate of leukemia/lymphoma formation was linked to a decreased in vitro cytotoxic capacity of TYK2(-/-) NK and NKT cells toward tumor-derived cells. RAG2/TYK2 double-knockout mice succumbed to A-MuLV-induced leukemia/lymphoma faster than RAG2(-/-)TYK2(+/-) mice. This defines NK cells as key players in tumor surveillance in Abelson-induced malignancies. Our observations provide compelling evidence that TYK2 is an important regulator of lymphoid tumor surveillance.

TYK2 is a key regulator of the surveillance of B lymphoid tumors

Aberrant activation of the JAK-STAT pathway has been implicated in tumor formation; for example, constitutive activation of JAK2 kinase or the enforced expression of STAT5 induces leukemia in mice. We show here that the Janus kinase TYK2 serves an opposite function. Mice deficient in TYK2 developed Abelson-induced B lymphoid leukemia/lymphoma as well as TEL-JAK2-induced T lymphoid leukemia with a higher incidence and shortened latency compared with WT controls. The cell-autonomous properties of Abelson murine leukemia virus-transformed (A-MuLV-transformed) TYK2(-/-) cells were unaltered, but the high susceptibility of TYK2(-/-) mice resulted from an impaired tumor surveillance, and accordingly, TYK2(-/-) A-MuLV-induced lymphomas were easily rejected after transplantation into WT hosts. The increased rate of leukemia/lymphoma formation was linked to a decreased in vitro cytotoxic capacity of TYK2(-/-) NK and NKT cells toward tumor-derived cells. RAG2/TYK2 double-knockout mice succumbed to A-MuLV-induced leukemia/lymphoma faster than RAG2(-/-)TYK2(+/-) mice. This defines NK cells as key players in tumor surveillance in Abelson-induced malignancies. Our observations provide compelling evidence that TYK2 is an important regulator of lymphoid tumor surveillance.

BCR/ABL-mediated downregulation of genes implicated in cell adhesion and motility leads to impaired migration toward CCR7 ligands CCL19 and CCL21 in primary BCR/ABL-positive cells

The mechanism underlying p210(BCR/ABL) oncoprotein-mediated transformation in chronic myelogenous leukemia (CML) is not fully understood. We hypothesized that p210(BCR/ABL) suppresses expression of genes which may explain at least some of the pathogenetic features of CML. A subtractive cDNA library was created between BCR/ABL-enhanced-green-fluorescent-protein (GFP)-transduced umbilical cord blood (UCB) CD34+ cells and GFP-transduced UCB CD34+ cells to identify genes whose expression is downregulated by p210(BCR/ABL). At least 100 genes were identified. We have confirmed for eight of these genes that expression was suppressed by quantitative real-time-RT-PCR (Q-RT-PCR) of additional p210(BCR/ABL)-transduced CD34+ UCB cells as well as primary early chronic phase (CP) bone marrow (BM) CML CD34+ cells. Imatinib mesylate reversed downregulation of some genes, to approximately normal levels. Several of the genes are implicated in cell adhesion and motility, including L-selectin, intercellular adhesion molecule-1 (ICAM-1), and the chemokine receptor, CCR7, consistent with the known defect in adhesion and migration of CML cells. Compared with GFP UCB or normal (NL) BM CD34+ cells, p210 UCB and CML CD34+ cells migrated poorly towards the CCR7 ligands, CCL19 and CCL21, suggesting a possible role for CCR7 in the abnormal migratory behavior of CML CD34+ cells.

Nuclear factor-kappaB: a friend or a foe in cancer?

Nuclear transcription factor NF-kappaB, initially discovered as a factor in the nucleus of B cells that binds to the enhancer of the kappa light chain of immunoglobulin, has since been shown to be expressed ubiquitously in the cytoplasm of all cell types, conserved from Drosophila to man. It translocates to the nucleus only when activated, where it regulates the expression of over 200 genes that control the immune system, growth, and inflammation. The dysregulation of NF-kappaB can mediate a wide variety of diseases including cancer. Whether NF-kappaB activation is beneficial or harmful for cancer is controversial. The development of novel therapeutics targeting NF-kappaB requires full understanding of its role in pathology and physiology. The current review is an attempt to describe two sides of the NF-kappaB coin; viz, as a friend and as a foe.

Immunity to chronic myelogenous leukemia

Given the high rate of cytogenetic responses to imatinib mesylate in chronic myelogenous leukemia (CML), logical future treatment strategies will include combinations of tyrosine kinase inhibitors and immunotherapies such as vaccines. Increased understanding of highly specific immune responses will lead to novel and improved immunotherapy strategies for CML patients. Such advances can be expected to revolutionize the field much in the same way that imatinib mesylate and other targeted small molecules have revolutionized our conception of traditional chemotherapy. This article begins with a brief discussion of why CML may represent a model disease for immunotherapy-based strategies. Laboratory evidence of the immunoresponsiveness of CML is discussed and used to highlight the principles for understanding tumor immunity. Finally,the authors discuss how advances in the understanding of the molecular and cellular nature of immunity are being translated into new therapeutic strategies for the treatment of CML.

Nuclear factor-kappaB: the enemy within

Numerous lines of investigation suggest that nuclear factor NF-kappaB, a proinflammatory transcription factor, could promote tumorigenesis. Various inflammatory agents, carcinogens, tumor promoters, and the tumor microenvironment activate NF-kappaB. NF-kappaB proteins themselves and proteins regulated by it have been linked to cellular transformation, proliferation, apoptosis suppression, invasion, angiogenesis, and metastasis. Constitutively activated NF-kappaB is common in wide variety of tumors. Furthermore, there exists genetic evidence that NF-kappaB mediates tumorigenesis. Thus, suppression of NF-kappaB activation should be effective in the prevention and treatment of cancer.

Allogeneic hematopoietic cell transplantation as treatment for hematological malignancies: a review

Allogeneic hematopoietic cell transplantation (HCT) was originally developed as a form of rescue from high-dose chemoradiotherapy, which is given both to eradicate malignancy and provide sufficient immunosuppression for allogeneic engraftment. The first attempts of allogeneic HCT in humans met with little success. However, a better understanding of the complexities of the human leukocyte antigen (HLA) system has allowed selecting compatible sibling donors, and the development of postgrafting immunosuppressive regimens has helped prevent serious graft-versus-host disease, thereby changing the role of allogeneic HCT from a desperate therapeutic maneuver to a curative treatment modality for many patients with malignant hematological diseases. In addition, the establishment of large registries of HLA-typed volunteers has permitted finding suitable unrelated donors for many patients without family donors. Further advances in the immunogenetics of HLA, especially typing by molecular techniques, have improved results after unrelated HCT, which have begun resembling those obtained with HLA-identical sibling grafts, at least in young patients. Important advances have also been made in the prevention and treatment of infectious complications and in other areas of supportive care. Since the late seventies, it has been recognized that allogeneic immunocompetent cells transplanted with the stem cells, or arising from them, mediated therapeutic anti-tumor effects independent of the action of the high-dose therapy, termed graft-versus-tumor (GVT) effects. This has prompted the recent development of non-myeloablative conditioning regimens for allogeneic HCT that have opened the way to include elderly patients and those with comorbid conditions. Remaining challenges include further advances in the prevention and treatment of both severe graft-versus-host disease and infections. Also, progress in adoptive transfer of T cells with relative tumor specificity and disease-targeted therapy with agents such as Imatinib, Rituximab or radiolabeled monoclonal antibodies would make allogeneic HCT even more effective.

Natural killer cell-triggering receptors in patients with acute leukaemia

Human natural killer (NK) cells are potent effectors involved in destruction of virus infected cells and tumours. Their cytolytic function is regulated by surface receptors that either inhibit or increase the NK-mediated cytotoxicity. Under physiological conditions, NK cells recognize major histocompatibility complex (MHC)-class I molecules through surface receptors delivering signals that inhibit NK cells function. Nonetheless, the "missing self hypothesis", i.e. the release of an inhibitory signal by the interaction between HLA I-specific inhibitory receptors and their ligands, is not sufficient to entirely explain the regulation of NK cytotoxicity. Activating and co-receptors also play a central role in NK cell activation. In the haematology field, several lines of evidence suggest that NKs participate to the anti-leukaemia immune response: (1) leukaemic cells have down-regulated HLA-class I molecule expression and putative allele loss, (2) several reports have indicated an inverse relationship between NK cell number or activity and prognosis in acute leukaemia, (3) NK-cell activity dependent immunodeficiency syndromes are associated with an increased frequency of lymphoid haematological malignancies, (4) recent data support a role for NK cells in the graft-versus-leukaemia effect observed in allogeneic bone marrow transplantation. All these data raise several questions. How NK cells kill leukaemic targets, and how can leukaemia escape from innate immunity surveillance? What are the therapeutic possibilities to manipulate NK receptor-ligand interaction in order to increase leukaemia cell destruction? The responses to these questions will contribute to immunotherapy advancements in leukaemia and more generally in cancer.

NK cells: innate immunity against hematological malignancies?

Recent advances in the treatment of malignant haemopathies enable increased remission and cure rates, however, many patients relapse and finally die. Although specific immunity mediated by cytolytic T-lymphocytes might have an anti-cancer role, tumours escape from T-cell-based immune surveillance using various mechanisms, such as downregulation, mutation or loss of HLA class I molecules. As a consequence, these transformed cells could become targets for natural killer (NK) cells, whose cytotoxic capabilities are not blocked by HLA class I molecule engagement by specific inhibitory receptors. Novel developments in NK-cell research, particularly the identification of the role of non-HLA-restricted activating receptors (and in some cases of their ligands), have recently enabled us to reconsider NK-cell interactions with haematological malignant cells.

Analysis of the natural killer mediated immune response in metastatic renal cell carcinoma patients

Metastatic renal cell carcinomas (MRCC) are considered as immunogeneic tumors on the basis of the clinical responses observed in patients treated by IL-2. However, renal cell carcinoma patients are also characterized by alterations of the immune response that may compromise the immunotherapeutic approaches. In our study, we have studied the phenotype and the functional capacities of peripheral NK cells in a panel of neprectomized metastatic renal cell carcinoma patients. NK cells were harvested by negative immunoselection from fresh peripheral blood samples. In most of MRCC patients analysed (23/28), the expression of NCR (NKp46 and NKp30) was similar to that of donors. Lytic capacities by activated immunoselected NK cells from MRCC patients assessed against K562 and 3 renal tumor cell lines were in the range of that observed in NK cells from normal donors. HLA-I- renal tumor cells UOK23 were killed with a good efficiency, whereas HLA-I renal tumor cells were more resistant. Although LFA-1/ICAM-1 interaction potentiates RCC cell lysis, HLA-I/NKR interaction clearly decreased RCC cell susceptibility to NK cells. In addition, proliferation of NK cells from MRCC patients in response to cytokines was altered.

T-cell reconstitution after unmanipulated, CD8-depleted or CD34-selected nonmyeloablative peripheral blood stem-cell transplantation

BACKGROUND

We have previously shown that CD8 depletion or CD34 selection of peripheral blood stem cells (PBSC) reduced the incidence of acute graft-versus-host disease (GvHD) after nonmyeloablative stem-cell transplantation (NMSCT). In this study, we analyze the effect of CD8 depletion or CD34 selection of the graft on early T-cell reconstitution.

METHODS

Nonmyeloablative conditioning regimen consisted in 2 Gy total-body irradiation (TBI) alone, 2 Gy TBI and fludarabine, or cyclophosphamide and fludarabine. Patients 1 to 18 received unmanipulated PBSC, patients 19 to 29 CD8-depleted PBSC, and patients 30 to 35 CD34-selected PBSC.

RESULTS

T-cell counts, and particularly CD4+ and CD4CD45RA+ counts, remained low the first 6 months after nonmyeloablative stem-cell transplantation (NMSCT) in all patients. CD34 selection (P<0.0001) but not CD8 depletion of PBSC significantly decreased T-cell chimerism. Donor T-cell count was similar in unmanipulated compared with CD8-depleted PBSC recipients but was significantly lower in CD34-selected PBSC recipients (P=0.0012). T cells of recipient origin remained stable over time in unmanipulated and CD8-depleted PBSC patients but expanded in some CD34-selected PBSC recipients between day 28 and 100 after transplant. Moreover, whereas CD8 depletion only decreased CD8+ counts (P<0.047), CD34 selection reduced CD3+(P<0.001), CD8+(P<0.016), CD4+ (P<0.001), and CD4+CD45RA+ (P<0.001) cell counts. T-cell repertoire was restricted in all patients on day 100 after hematopoietic stem-cell transplantation but was even more limited after CD34 selection (P=0.002).

CONCLUSIONS

Despite of the persistence of a significant number of T cells of recipient origin, T-cell counts were low the first 6 months after NMSCT. Moreover, contrary with CD8 depletion of the graft that only affects CD8+ lymphocyte counts, CD34 selection dramatically decreased both CD8 and CD4 counts.

Hematopoietic cell transplantation: five decades of progress

During the past 50 years, the role of allogeneic hematopoietic cell transplantation (HCT) has changed from a desperate therapeutic maneuver plagued by apparently insurmountable complications to a curative treatment modality for thousands of patients with hematologic diseases. Now, cure rates following human leukocyte antigen (HLA) allogeneic HCT with matched siblings exceed 85% for some otherwise lethal diseases, such as chronic myeloid leukemia, aplastic anemia, or thalassemia. In addition, the recent development of non-myeloablative conditioning and stem cell transplantation has opened the way to include elderly patients with a wide variety of hematologic malignancies. Further progress in adoptive transfer of T cell populations with relative tumor specificity would make the transplant procedure more effective and would extend the use of allogeneic HCT for treatment of non-hematopoietic malignancies.

New approaches in the immunotherapy of haematological malignancies

Advances in the management of haematological malignancies have allowed to obtain improved remission rates. Nonetheless, relapses impair these results and justify the search for novel therapeutic strategies. Clinical data demonstrate that the immune system plays an important role in the control of haematological malignancies. An increased frequency of haematological malignancies is observed in immunodeficiency states. Reversal of the immunosuppression is sometimes sufficient to induce tumour regression (withdrawal of cyclosporine in post-transplant lymphoproliferations, highly active anti-retroviral treatment in human immunodeficiency virus related Kaposi's disease). Another line of evidence for the involvement of the immune system in the anti-tumour response comes from the observation of spontaneous anti-tumour responses that parallel the occurrence of paraneoplastic immune-mediated syndromes. Finally, the efficiency of allogeneic transplantation in the haematological field has been clearly demonstrated to depend on the immune-mediated graft vs. leukaemia effect. Nonetheless, tumours develop in immune competent patients because of various tumour escape mechanisms, such as loss of human leucocyte antigen class I antigens, absence of target recognition by deficient adhesion/co-stimulatory molecule expression, tumour cell counterattack against immune effectors, direct (contact-dependent) or indirect (cytokine-mediated) impairment of T-lymphocyte activation. Novel immunotherapy approaches are now orientated in a convergent direction, i.e. the reversal of immune escape mechanisms either via the correction of deficient phases of the immune response or by the amplification of physiological mechanisms.