The Src/ABL kinase inhibitor dasatinib (BMS-354825) inhibits function of normal human T-lymphocytes in vitro

The tyrosine kinase inhibitor dasatinib reduces lung inflammation and remodelling in experimental allergic asthma

BACKGROUND AND PURPOSE

Asthma is characterized by chronic lung inflammation and airway hyperresponsiveness. Despite recent advances in understanding of its pathophysiology, asthma remains a major public health problem, and new therapeutic strategies are urgently needed. In this context, we sought to ascertain whether treatment with the TK inhibitor dasatinib might repair inflammatory and remodelling processes, thus improving lung function, in a murine model of asthma.

EXPERIMENTAL APPROACH

Animals were sensitized and subsequently challenged, with ovalbumin (OVA) or saline. Twenty-four hours after the last challenge, animals were treated with dasatinib, dexamethasone, or saline, every 12 h for 7 consecutive days. Twenty-four hours after the last treatment, the animals were killed, and data were collected. Lung structure and remodelling were evaluated by morphometric analysis, immunohistochemistry, and transmission electron microscopy of lung sections. Inflammation was assessed by cytometric analysis and ELISA, and lung function was evaluated by invasive whole-body plethysmography.

KEY RESULTS

In OVA mice, dasatinib, and dexamethasone led to significant reductions in airway hyperresponsiveness. Dasatinib was also able to attenuate alveolar collapse, contraction index, and collagen fibre deposition, as well as increasing elastic fibre content, in OVA mice. Concerning the inflammatory process, dasatinib reduced inflammatory cell influx to the airway and lung-draining mediastinal lymph nodes, without inducing the thymic atrophy promoted by dexamethasone.

CONCLUSIONS AND IMPLICATIONS

In this model of allergic asthma, dasatinib effectively blunted the inflammatory and remodelling processes in asthmatic lungs, enhancing airway repair and thus improving lung mechanics.

Dasatinib inhibits HIV-1 replication through the interference of SAMHD1 phosphorylation in CD4+ T cells

Massive activation of infected CD4+ T cells during acute HIV-1 infection leads to reservoir seeding and T-cell destruction. During T-cell activation, the antiviral effect of the innate factor SAMHD1 is neutralized through phosphorylation at T592, allowing HIV-1 infection. Dasatinib, a tyrosine kinase inhibitor currently used for treating chronic myeloid leukemia, has been described to control HIV-1 replication through its negative effect on T-cell proliferation and viral entry. We demonstrate that Dasatinib can actually interfere with SAMHD1 phosphorylation in human peripheral blood lymphocytes, preserving its antiviral activity against HIV-1. Dasatinib prevented SAMHD1 phosphorylation in vitro and ex vivo, impairing HIV-1 reverse transcription and proviral integration. This was the major mechanism of action because the presence of Vpx, which degrades SAMHD1, in HIV-1 virions impeded the inhibitory effect of Dasatinib on HIV-1 replication. In fact, infection with VSV-pseudotyped HIV-1 virions and fusion of BlaM-Vpr-containing HIV-1 viruses with activated PBMCs in the presence of Dasatinib suggested that Dasatinib was not acting at fusion level. Finally, PBMCs from patients on chronic treatment with Dasatinib showed a lower level of SAMHD1 phosphorylation in response to activating stimuli and low susceptibility to HIV-1 infection ex vivo. Consequently, Dasatinib is a compound currently used in clinic that preserves the antiviral function of SAMHD1. Using Dasatinib as adjuvant of antiretroviral therapy during early primary HIV-1 infection would contribute to reduce viral replication and spread, prevent reservoir seeding, and preserve CD4 counts and CTL responses. These events would create a more favorable virologic and immunologic environment for future interventional studies aiming at HIV-1 eradication.

Pretransplantation use of the second-generation tyrosine kinase inhibitors has no negative impact on the HCT outcome

Introduction

Allogeneic hematopoietic cell transplantation (HCT) was a standard therapy in chronic phase (CP) chronic myeloid leukemia (CML). As a result of the effective therapy with tyrosine kinase inhibitors (TKI), HCT was shifted to defined clinical situations. We present the results of observational prospective analysis of 28 CML patients undergoing HCT after exposure to, at least, two lines of TKI (including dasatinib and/or nilotinib), with respect to response, overall survival (OS), treatment toxicity, graft versus host disease (GVHD), and progression/relapse incidence.

Results

All the patients but one engrafted with median time 19 days. OS for patients in CP1 and CP2/accelerated phase (AcP) were 92.9 and 85.7 %, respectively. Six patients allotransplanted in blast crisis (BC) CML died early after HCT.

Eighteen patients achieved deep molecular remission (MR^4.5 or MR^4.0). Relapse incidence was 29.6 %. Median time to progression (TTP) differs significantly depending on the CML phase prior to HCT, the best response achieved after HCT and development of chronic GvHD.

NRM yielded the values 7.1, 12.5, and 50 % in CP1, CP2/AcP, and BC, respectively. Fatal outcome, due to veno-occlusive disease (VOD), was observed in two (7 %) patients. In five (17.9 %) patients, mild or moderate VOD was observed with no negative impact of preceding therapy with TKI2. Acute GvHD was diagnosed in 25.9 % of patients, while chronic GvHD developed in 42.9 % of individuals.

Conclusion

Pretransplantation therapy with TKI2 in CP CML is safe and reasonable. In BC, the optimal approach before HCT is to reduce the leukemic burden and achieve subsequent CP.

An immunosuppressive antibody-drug conjugate

We have developed a novel antibody-drug conjugate (ADC) that can selectively deliver the Lck inhibitor dasatinib to human T lymphocytes. This ADC is based on a humanized antibody that selectively binds with high affinity to CXCR4, an antigen that is selectively expressed on hematopoietic cells. The resulting dasatinib-antibody conjugate suppresses T-cell-receptor (TCR)-mediated T-cell activation and cytokine expression with low nM EC50 and has minimal effects on cell viability. This ADC may lead to a new class of selective immunosuppressive drugs with improved safety and extend the ADC strategy to the targeted delivery of kinase inhibitors for indications beyond oncology.

Immune consequences of kinase inhibitors in development, undergoing clinical trials and in current use in melanoma treatment

Metastatic malignant melanoma is a frequently fatal cancer. In recent years substantial therapeutic progress has occurred with the development of targeted kinase inhibitors and immunotherapeutics. Targeted therapies often result in rapid clinical benefit however responses are seldom durable. Immune therapies can result in durable disease control but responses may not be immediate. Optimal cancer therapy requires both rapid and durable cancer control and this can likely best be achieved by combining targeted therapies with immunotherapeutics. To achieve this, a detailed understanding of the immune consequences of the various kinase inhibitors, in development, clinical trial and currently used to treat melanoma is required.

Dasatinib promotes Th1-type responses in granzyme B expressing T-cells

Tyrosine kinase inhibitors (TKIs) have dramatically improved the outcome of chronic myeloid leukemia (CML). Besides inhibiting target kinases in leukemic cells, 2nd generation TKI dasatinib also inhibits off-targets in immune effector cells resulting in atypical immune responses in some patients. Dasatinib has been described to increase the proportion of late effector memory T-cells, however, to date no follow-up studies have been performed in first-line patients. In this study, we explored the functional properties of T-cells using primary samples from CML patients (n = 28) on TKI therapy. Granzyme B (GrB) was used as a marker for late phase antigen experienced CD4+ and CD8+ T-cells. Dasatinib treatment increased the numbers of both GrB expressing memory CD4+ and CD8+ T-cells when compared with healthy controls. Functionally, the GrB+CD4+ T-cells were highly active and differentiated into Th1-type T-cells capable of producing IFN-γ, which is important for tumor control. Similar kind of increase was not observed during imatinib or nilotinib therapy. These data support the dual mode of action of dasatinib: potent BCR-ABL1 inhibition in leukemic cells is accompanied by the enhancement of cellular immunity, which may have implications in the long-term control of leukemia.

SEA antagonizes the imatinib-meditated inhibitory effects on T cell activation via the TCR signaling pathway

The BCR-ABL kinase inhibitor imatinib is highly effective in the treatment of chronic myeloid leukemia (CML). However, long-term imatinib treatment induces immunosuppression, which is mainly due to T cell dysfunction. Imatinib can reduce TCR-triggered T cell activation by inhibiting the phosphorylation of tyrosine kinases such as Lck, ZAP70, LAT, and PLCγ1 early in the TCR signaling pathway. The purpose of this study was to investigate whether the superantigen SEA, a potent T cell stimulator, can block the immunosuppressive effects of imatinib on T cells. Our data show that the exposure of primary human T cells and Jurkat cells to SEA for 24 h leads to the upregulation of the Lck and ZAP70 proteins in a dose-dependent manner. T cells treated with SEA prior to TCR binding had increased the tyrosine phosphorylation of Lck, ZAP70, and PLCγ1. Pretreatment with SEA prevents the inhibitory effects of imatinib on TCR signaling, which leads to T cell proliferation and IL-2 production. It is conceivable that SEA antagonizes the imatinib-mediated inhibition of T cell activation and proliferation through the TCR signaling pathway.

The tyrosine kinase inhibitor Dasatinib blocks in-vitro HIV-1 production by primary CD4+ T cells from HIV-1 infected patients

HIV reservoirs persistence despite antiretroviral therapy (ART) might be related to persistent immune activation and residual HIV production, requiring further therapeutic strategies. We demonstrated that the tyrosine kinase inhibitor (TKI) Dasatinib, used for chronic myeloid leukaemia, significantly blocks in vitro HIV1 production by 3.4 logs in HIV1-infected primary CD4 T lymphocytes, by inhibiting cell activation and proliferation, without cell toxicity. This molecule deserves to be investigated further for HIV cure strategies to hinder persistent immune activation and residual viral production.

Large granular lymphocytosis during dasatinib therapy

Dasatinib is a second generation tyrosine kinase inhibitor (TKI) approved for clinical use in patients with imatinib-resistant chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL). Large granular lymphocytes (LGLs) are medium to large cells with eccentric nuclei and abundant cytoplasm with coarse azurophilic granules. LGL lymphocytosis is caused by a proliferation of cytotoxic (CD8+) T cells and/or NK cells. In a proportion of CML and Ph(+) ALL patients, there is a significant expansion of LGLs during dasatinib therapy. LGL lymphocytosis is seen in some cases with fevers, colitis, and pleural effusions (PE), suggesting an aberrant immune response mediated by these LGLs. LGLs may participate in the elimination of the residual leukemic cells, and LGL clonal expansion is associated with excellent, long-lasting therapy responses in dasatinib-treated patients. For a more comprehensive analysis, we analyzed the morphologic, phenotypic, clinical, and functional features of the LGL subsets amplified in vivo during dasatinib therapy.

Dasatinib, large granular lymphocytosis, and pleural effusion: useful or adverse effect?

Dasatinib is a second generation tyrosine kinase inhibitor approved for clinical use in first line and imatinib-resistant chronic myeloid leukemia and Philadelphia positive (Ph+) acute lymphoblastic leukemia. In addition to BCR-ABL1, dasatinib inhibits TEC kinases and SRC family kinases and is more potent than imatinib in the treatment of Ph+ leukemias. In the last 3 years, increases in cytotoxic T and natural-killer cells in peripheral blood samples have been reported in cases treated by dasatinib. The awareness of the clonal expansion of large granular lymphocytes and beneficial effect of these clonal cells increased the interest to dasatinib in cases receiving this drug. Clonal expansion of large granular lymphocytes is an important effect of dasatinib therapy, shown to be an off-target phenomenon associated with pleural effusion and better clinical response. The benefit of dasatinib-induced lymphocytosis and its underlying mechanism of this are important points for clinicians working in hematology and oncology.

Src-kinase inhibitors sensitize human cells of myeloid origin to Toll-like-receptor-induced interleukin 12 synthesis

Src-kinase inhibitors hold great potential as targeted therapy against malignant cells. However, such inhibitors may also affect nonmalignant cells and cause pronounced off-target effects. We investigated the role of the dual kinase inhibitor dasatinib on human myeloid cells. Dasatinib is clinically used for the treatment of bcr/abl⁺ leukemias because it blocks the mutated tyrosine kinase abl. To understand its effect on the development of antigen-specific T-cell responses, we assessed antigen-specific priming of human, naïve T cells. In surprising contrast to the direct inhibition of T-cell activation by dasatinib, pretreatment of maturing dendritic cells (DCs) with dasatinib strongly enhanced their stimulatory activity. This effect strictly depended on the activating DC stimulus and led to enhanced interleukin 12 (IL-12) production and T-cell responses of higher functional avidity. Src-kinase inhibitors, and not conventional tyrosine kinase inhibitors, increased IL-12 production in several cell types of myeloid origin, such as monocytes and classical or nonclassical DCs. Interestingly, only human cells, but not mouse or macaques DCs, were affected. These data highlight the potential immunostimulatory capacity of a group of novel drugs, src-kinase inhibitors, thereby opening new opportunities for chemoimmunotherapy. These data also provide evidence for a regulatory role of src kinases in the activation of myeloid cells.

Tyrosine kinase inhibitors impair B-cell immune responses in CML through off-target inhibition of kinases important for cell signaling

Tyrosine kinase inhibitors (TKIs) have significant off-target multikinase inhibitory effects. We aimed to study the impact of TKIs on the in vivo B-cell response to vaccination. Cellular and humoral responses to influenza and pneumococcal vaccines were evaluated in 51 chronic phase chronic myeloid leukemia (CML) patients on imatinib, or second-line dasatinib and nilotinib, and 24 controls. Following vaccination, CML patients on TKI had significant impairment of IgM humoral response to pneumococcus compared with controls (IgM titer 79.0 vs 200 U/mL, P = .0006), associated with significantly lower frequencies of peripheral blood IgM memory B cells. To elucidate whether CML itself or treatment with TKI was responsible for the impaired humoral response, we assessed memory B-cell subsets in paired samples collected before and after imatinib therapy. Treatment with imatinib was associated with significant reductions in IgM memory B cells. In vitro coincubation of B cells with plasma from CML patients on TKI or with imatinib, dasatinib, or nilotinib induced significant and dose-dependent inhibition of Bruton's tyrosine kinase and indirectly its downstream substrate, phospholipase-C-γ2, both important in B-cell signaling and survival. These data indicate that TKIs, through off-target inhibition of kinases important in B-cell signaling, reduce memory B-cell frequencies and induce significant impairment of B-cell responses in CML.

Rapid mobilization of cytotoxic lymphocytes induced by dasatinib therapy

Tyrosine kinase inhibitors (TKIs) have potent effects on malignant cells, and they also target kinases in normal cells, which may have therapeutic implications. Using a collection of 55 leukemia patients treated with TKI therapy (chronic myeloid leukemia, n=47; acute lymphoblastic leukemia, n=8), we found that dasatinib, a second-generation broad-spectrum TKI, induced a rapid, dose-dependent and substantial mobilization of non-leukemic lymphocytes and monocytes in blood peaking 1-2 h after an oral intake and the blood counts closely mirrored drug plasma concentration. A preferential mobilization was observed for natural killer (NK), NK T, B and γδ+ T cells. Mobilization was coupled with a more effective transmigration of leukocytes through an endothelial cell layer and improved cytotoxicity of NK cells. Platelet numbers decreased markedly after the drug intake in a proportion of patients. Similar effects on blood cell dynamics and function were not observed with any other TKI (imatinib, nilotinib and bosutinib). Thus, dasatinib induces a unique, rapid mobilization and activation of cytotoxic, extravasation-competent lymphocytes, which may not only enhance antileukemia immune responses but can also be causally related to the side-effect profile of the drug (pleural effusions, thrombocytopenia).

Direct effect of dasatinib on proliferation and cytotoxicity of natural killer cells in in vitro study

Lymphocytosis predominantly due to natural killer (NK) cells has been reported in nearly a half of chronic myelogenous leukemia (CML) patients who were being treated with dasatinib. Besides, dasatinib-treated patients with lymphocytosis have a better prognosis than patients without lymphocytosis. In order to elucidate the effects of dasatinib on the proliferation of lymphocyte subset, dasatinib was added to the culture of peripheral blood mononuclear cells with IL-2 (lymphokine-activated killer culture) or a low dose of IL-2 with zoledronate (γδ T-cell culture). In both culture conditions, NK cells were increased in both percentage and absolute number in the culture with dasatinib compared with control culture without dasatinib. The increase of NK cells was dose dependent of dasatinib in the range of 2-25 nM. NK cell cytotoxicity of cultured cells with dasatinib was demonstrated to be superior to control cells without dasatinib in cytotoxicity assay using EGFP-transfected K562 cells as target cells. The present study suggested that lymphocytosis in dasatinib-treated CML patients is at least partly associated with a direct effect of dasatinib to stimulate the proliferation of NK cells. Favourable prognosis in patients with dasatinib-induced lymphocytosis might be associated with the effects of dasatinib to potentiate NK cytotoxicity in vivo.

The role of natural killer cells in chronic myeloid leukemia

Chronic myeloid leukemia is a neoplasia resulting from a translocation between chromosomes 9 and 22 producing the BCR-ABL hybrid known as the Philadelphia chromosome (Ph). In chronic myeloid leukemia a proliferation of malignant myeloid cells occurs in the bone marrow due to excessive tyrosine kinase activity. In order to maintain homeostasis, natural killer cells, by means of receptors, identify the major histocompatibility complex on the surface of tumor cells and subsequently induce apoptosis. The NKG2D receptor in the natural killer cells recognizes the transmembrane proteins related to major histocompatibility complex class I chain-related genes A and B (MICA and MICB), and it is by the interaction between NKG2D and MICA that natural killer cells exert cytotoxic activity against chronic myeloid leukemia tumor cells. However, in the case of chronic exposure of the NKG2D receptor, the MICA ligand releases soluble proteins called sMICA from the tumor cell surface, which negatively modulate NKG2D and enable the tumor cells to avoid lysis mediated by the natural killer cells. Blocking the formation of sMICA may be an important antitumor strategy. Treatment using tyrosine kinase inhibitors induces modulation of NKG2DL expression, which could favor the activity of the natural killer cells. However this mechanism has not been fully described in chronic myeloid leukemia. In the present study, we analyze the role of natural killer cells to reduce proliferation and in the cellular death of tumor cells in chronic myeloid leukemia.

Biological therapy and the immune system in patients with chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of hematopoietic stem cells that has been recognized as a disease responsive to immunotherapy. Despite the huge success of the tyrosine kinase inhibitors (TKIs), CML remains for the most part incurable, probably due to treatment resistance of leukemic stem cells, which are responsible for rapid disease relapse after discontinuation of therapy. Only allogeneic stem cell transplantation enables disease eradication. In addition to the Bcr-Abl1 oncoprotein, TKIs also inhibit off-target kinases (e.g. c-kit, Src, Tec), some of them having physiological functions in immune responses. In vitro studies have implied immunomodulatory effects of TKIs and interferon-alpha (IFN-α), but comprehensive information from in vivo analyses is missing. This review summarizes the recent advances in the field of immunology of CML, including basic information about leukemia-associated antigens and peptide vaccines, that could lead to the incorporation of TKIs and IFN-α in future therapeutic, potentially curative, interventions for CML.

Drug-interaction studies evaluating T-cell proliferation reveal distinct activity of dasatinib and imatinib in combination with cyclosporine A

Development of small molecule tyrosine kinase inhibitors for the treatment of chronic myeloid leukemia has been astonishingly successful; however, their off-target effects have generated both challenges and opportunities for extending their clinical application. Dasatinib and imatinib are two of the most commonly used tyrosine kinase inhibitors and both have been shown to impact T-cell function. Due to this activity, their use as potential immune suppressants has been proposed. In this report, we investigated drug interactions with cyclosporine A in suppressing T-cell proliferation. Dasatinib and imatinib were titrated against varying concentrations of cyclosporine in the cultures and T-cell proliferation assessed by 5-6-carboxyfluorescein diacetate, succinimidyl ester dye dilution. These proliferation data were then used to determine the combination index to evaluate additive, synergistic, or antagonistic interactions between the drugs. This analysis uncovered a number of different drug interactions affecting T-cell proliferation. Cyclosporine had an additive or synergistic effect on T-cell proliferation when combined with dasatinib and imatinib for 3 of the 4 methods of stimulating T-cell proliferation. However, when T cells were stimulated with anti-CD3 and anti-CD28 antibodies, this interaction was found to be strongly antagonistic at low dasatinib concentrations. In contrast, this strong antagonism was not observed when imatinib was used in combination with cyclosporine A. This study suggests drug interactions affecting T cells may need to be carefully taken into account when using tyrosine kinase inhibitors. Furthermore, the technique to evaluate drug interactions is novel, and applicable to study any interaction affecting proliferation.

The secret ally: immunostimulation by anticancer drugs

It has recently become clear that the tumour microenvironment, and in particular the immune system, has a crucial role in modulating tumour progression and response to therapy. Indicators of an ongoing immune response, such as the composition of the intratumoural immune infiltrate, as well as polymorphisms in genes encoding immune modulators, have been correlated with therapeutic outcome. Moreover, several anticancer agents--including classical chemotherapeutics and targeted compounds--stimulate tumour-specific immune responses either by inducing the immunogenic death of tumour cells or by engaging immune effector mechanisms. Here, we discuss the molecular and cellular circuitries whereby cytotoxic agents can activate the immune system against cancer, and their therapeutic implications.

Tyrosine kinases in inflammatory dermatologic disease

Tyrosine kinases (TKs) are enzymes that catalyze the phosphorylation of tyrosine residues on protein substrates. They are key components of signaling pathways that drive an array of cellular responses including proliferation, differentiation, migration, and survival. Specific TKs have recently been identified as critical to the pathogenesis of several autoimmune and inflammatory diseases. Small-molecule inhibitors of TKs are emerging as a novel class of therapy that may provide benefit in certain patient subsets. In this review, we highlight TK signaling implicated in inflammatory dermatologic diseases, evaluate strategies aimed at inhibiting these aberrant signaling pathways, and discuss prospects for future drug development.

Retrospective multicenter study on the development of peripheral lymphocytosis following second-line dasatinib therapy for chronic myeloid leukemia

The current retrospective study investigated the incidence of lymphocytosis following second-line dasatinib therapy in chronic myeloid leukemia (CML) and analyzed the clinical factors predictive of the development of lymphocytosis, as well as association with treatment outcomes. Fifty CML patients who failed imatinib treatment and received dasatinib were included from nine centers in the Republic of Korea. The cumulative incidence of lymphocytosis was assessed, and cytogenetic and molecular response, treatment failure, loss of response, progression to advanced disease, and survival were evaluated and analyzed according to the development of lymphocytosis. After a median of 17 months of dasatinib therapy, 23 patients (46%) developed lymphocytosis (median onset 4 months). No clinical predictive factor for the development of lymphocytosis was found. The group presenting lymphocytosis showed a higher complete cytogenetic response (CCyR; 78.3 vs. 29.6%, P = 0.001) and major molecular response (MMR; 52.2 vs. 14.8%, P = 0.005), in comparison to the group without presenting lymphocytosis. The development of lymphocytosis after dasatinib was identified as a favorable independent marker for predicting a CCyR (P = 0.002) or MMR (P = 0.003). Further study is necessary to identify which subset of lymphocytes was expanded and to reveal the exact mechanism by which dasatinib induces lymphocyte expansion.

A molecular and functional analysis of large granular lymphocyte expansions in patients with chronic myelogenous leukemia treated with tyrosine kinase inhibitors

Tyrosine kinase inhibitor (TKI) therapy has become the standard treatment for chronic myelogenous leukemia (CML). Off-target kinase inhibition has been implicated in the appearance of unique adverse effects, such as colitis and pleural effusions. In addition, some patients present oligoclonal expansions of large granular lymphocytes (LGLs). We sought to further investigate this phenomenon in 64 patients treated with five different TKIs. Clonal expansions of cytotoxic T lymphocytes (CTLs) were identified in all TKI-treated patient groups, but only in dasatinib-treated patients were these expansions characterized as LGLs. Survival factors known to be important in LGL leukemia (interleukin-15 [IL-15] transpresentation, plasma platelet-derived growth factor [PDGF]-BB levels, nuclear factor-κB [NF-κB] and T-bet activation) were found to be associated with TKI-induced LGL expansions. Interestingly, patients with LGL expansions had increased cytotoxicity against non-transformed endothelial cells, which may play a role in observed autoimmune-like side effects. Our results indicate that patients with CML treated with TKIs can develop T cell expansions, which can in certain cases be related to some adverse effects.

Immunoprofiling of patients with chronic myeloid leukemia at diagnosis and during tyrosine kinase inhibitor therapy

Tyrosine kinase inhibitors (TKIs) are the current standard treatment in chronic myeloid leukemia (CML). In addition to the BCR-ABL target oncoprotein, they also inhibit off-target kinases (e.g. c-KIT, TEC, SRC), some of which have physiological functions in immune responses. In vitro studies have implied immunosuppressive effects of TKI treatment. As comprehensive in vivo data are missing, we aimed at analyzing the detailed immunoprofile of patients with CML at diagnosis and during therapy. We collected 88 peripheral blood (PB) and 73 bone marrow (BM) samples from 54 patients with CML at diagnosis, during imatinib and dasatinib therapies. Leukocytes and lymphocyte subclasses were analyzed with an extensive flow cytometry panel including markers for activation, differentiation and memory status. At diagnosis, a lower proportion of B cells and dendritic cells and an increased amount of NKT-like cells were detected in the BM. During imatinib therapy, all these changes normalized and the immunoprofile resembled healthy controls. However, dasatinib patients were clearly divided into two distinct groups: one similar to healthy controls and the other showing immunoactivation characterized by significant elevations of CD8+, NK- and NKT-like cells in PB. T cells of the latter group strongly expressed CD57+, HLA-DR and CD45RO and had low CD62L antigen levels characteristic of late memory cytotoxic lymphocytes. Our results indicate that while both TKIs show immunosuppressive effects in vitro, they have a significant and differential effect on the numbers and proportions of immune effector cells in vivo. In particular, in a distinct subgroup of dasatinib-treated patients, immune reactivity is markedly enhanced warranting careful follow-up.

Functional protein network activation mapping reveals new potential molecular drug targets for poor prognosis pediatric BCP-ALL

BACKGROUND

In spite of leukemia therapy improvements obtained over the last decades, therapy is not yet effective in all cases. Current approaches in Acute Lymphoblastic Leukemia (ALL) research focus on identifying new molecular targets to improve outcome for patients with a dismal prognosis. In this light phosphoproteomics seems to hold great promise for the identification of proteins suitable for targeted therapy.

METHODOLOGY/PRINCIPAL FINDINGS

We employed Reverse Phase Protein Microarrays to identify aberrantly activated proteins in 118 pediatric B-cell precursor (BCP)-ALL patients. Signal transduction pathways were assayed for activation/expression status of 92 key signalling proteins. We observed an increased activation/expression of several pathways involved in cell proliferation in poor clinical prognosis patients. MLL-rearranged tumours revealed BCL-2 hyperphosphorylation through AMPK activation, which indicates that AMPK could provide a functional role in inhibiting apoptosis in MLL-rearranged patients, and could be considered as a new potential therapeutic target. Second, in patients with poor clinical response to prednisone we observed the up-modulation of LCK activity with respect to patients with good response. This tyrosine-kinase can be down-modulated with clinically used inhibitors, thus modulating LCK activity could be considered for further studies as a new additional therapy for prednisone-resistant patients. Further we also found an association between high levels of CYCLIN E and relapse incidence. Moreover, CYCLIN E is more expressed in early relapsed patients, who usually show an unfavourable prognosis.

CONCLUSIONS/SIGNIFICANCE

We conclude that functional protein pathway activation mapping revealed specific deranged signalling networks in BCP-ALL that could be potentially modulated to produce a better clinical outcome for patients resistant to standard-of-care therapies.

Poor cytokine-induced phosphorylation in chronic myeloid leukemia patients at diagnosis is effectively reversed by tyrosine kinase inhibitor therapy

OBJECTIVE

In chronic myeloid leukemia (CML), uncontrolled tyrosine kinase activity of the BCR-ABL1 oncoprotein results in aberrant signaling pathways and increased cell proliferation. Acquired immune tolerance to leukemic antigens further enables tumor cell expansion. Tyrosine kinase inhibitor (TKI) therapy interferes with the immunoregulatory system by targeting off-target kinases both in malignant and nonmalignant cells. The aim of this study was to analyze the immune cell function by phosphoprotein profiling in CML patients.

MATERIALS AND METHODS

Blood samples from diagnostic phase and TKI-treated patients were analyzed by multicolor phosphoprotein flow cytometry enabling measurements at the single-cell level. Both unstimulated baseline activation status and cytokine-induced responses were evaluated.

RESULTS

In diagnostic-phase and imatinib-treated patients, the baseline phosphoprotein activation status was similar to healthy controls. In dasatinib-treated patients, basal phosphoprotein levels were slightly decreased; in particular, the signal transduction and activator of transcription protein 3 pathway was affected in both myeloid and lymphoid cells. The activation responses to various cytokines, granulocyte-macrophage colony-stimulating factor in particular were significantly suppressed in untreated CML patients. During imatinib and dasatinib therapy, the aberrantly suppressed phosphorylation responses were normalized.

CONCLUSIONS

Cytokine responses are hampered in untreated CML patients, which may have an effect on various immunological processes in vivo. Interestingly, during TKI treatment, phosphorylation responses were normal, suggesting that TKI treatment does not alter the reactivity of healthy immune effector cells. However, dasatinib treatment was associated with diminished basal activation of the immunosuppressive signal transduction and activator of transcription protein 3 signaling pathway, which could have clinical significance in reversing the lymphocyte anergy against tumor cells.

Do we have to kill the last CML cell?

Previous experience in the treatment of chronic myeloid leukaemia (CML) has shown that the achievement of clinical, morphological and cytogenetic remission does not indicate eradication of the disease. A complete molecular response (CMR; no detectable BCR-ABL mRNA) represents a deeper level of response, but even CMR is not a guarantee of elimination of the leukaemia, because the significance of CMR is determined by the detection limit of the assay that is used. Two studies of imatinib cessation in CMR are underway, cumulatively involving over 100 patients. The current estimated rate of stable CMR after stopping imatinib is approximately 40%, but the duration of follow-up is relatively short. The factors that determine relapse risk are yet to be identified. The intrinsic capacity of any residual leukaemia [corrected] cells to proliferate following the withdrawal of treatment may be important, but there may also be a role for immunological suppression of the leukaemia [corrected] clone. No currently available test can formally prove that the leukaemic clone is eradicated. Here we discuss the sensitive measurement of minimal residual disease, and speculate on the biology of BCR-ABL-positive cells that may persist after effective therapy of CML.

Mono/oligoclonal T and NK cells are common in chronic myeloid leukemia patients at diagnosis and expand during dasatinib therapy

In a proportion of patients with chronic myeloid leukemia (CML) being treated with dasatinib, we recently observed large granular lymphocyte (LGL) expansions carrying clonal T-cell receptor (TCR) γ/δ gene rearrangements. To assess the prevalence and role of clonal lymphocytes in CML, we collected samples from patients (n = 34) at the time of diagnosis and during imatinib and dasatinib therapies and analyzed lymphocyte clonality with a sensitive polymerase chain reaction–based method of TCR γ and δ genes. Surprisingly, at CML diagnosis, 15 of 18 patients (83%) had a sizeable clonal, BCR-ABL1 negative lymphocyte population, which was uncommon in healthy persons (1 of 12; 8%). The same clone persisted at low levels in most imatinib-treated patients. In contrast, in a distinct population of dasatinib-treated patients, the diagnostic phase clone markedly expanded, resulting in absolute lymphocytosis in blood. Most patients with LGL expansions (90%) had TCR δ rearrangements, which were uncommon in patients without an LGL expansion (10%). The TCR δ clones were confined to γδ+ T- or natural killer–cell compartments and the TCR γ clones to CD4+/CD8+ αβ+ fractions. The functional importance of clonal lymphocytes as a part of leukemia immune surveillance and the putative anergy-reversing role of dasatinib require further evaluation.

The occurrence and management of fluid retention associated with TKI therapy in CML, with a focus on dasatinib

Tyrosine kinase inhibitors (TKIs) like dasatinib and nilotinib are indicated as second-line treatment for chronic myeloid leukemia resistant or intolerant to the current first-line TKI imatinib. These are agents are well tolerated, but potent and as such should be monitored for potentially serious side-effects like fluid retention and pleural effusions. Here we present key clinical trial data and safety considerations for all FDA approved TKIs in context for effective management of fluid retention and pleural effusions. Altering the dasatinib regimen from 70 mg twice daily to 100 mg daily reduces the risk of pleural effusion for patients taking dasatinib. Should pleural effusion develop, dasatinib should be interrupted until the condition resolves. Patients with a history of pleural effusion risk factors should be monitored closely while taking dasatinib. Patients receiving imatinib and nilotinib are not without risk of fluid retention. All patients should also be educated to recognize and report key symptoms of fluid retention or pleural effusion. Pleural effusions are generally managed by dose interruption/reduction and other supportive measures in patients with chronic myeloid leukemia receiving dasatinib therapy.

Tyrosine kinases as targets for the treatment of rheumatoid arthritis

As critical regulators of numerous cell signaling pathways, tyrosine kinases are implicated in the pathogenesis of several diseases, including rheumatoid arthritis (RA). In the absence of disease, synoviocytes produce factors that provide nutrition and lubrication for the surrounding cartilage tissue; few cellular infiltrates are seen in the synovium. In RA, however, macrophages, neutrophils, T cells and B cells infiltrate the synovium and produce cytokines, chemokines and degradative enzymes that promote inflammation and joint destruction. In addition, the synovial lining expands owing to the proliferation of synoviocytes and infiltration of inflammatory cells to form a pannus, which invades the surrounding bone and cartilage. Many of these cell responses are regulated by tyrosine kinases that operate in specific signaling pathways, and inhibition of a number of these kinases might be expected to provide benefit in RA.

The biological basis for immunotherapy in patients with chronic myelogenous leukemia

BACKGROUND

Chronic myelogenous leukemia (CML) has long been recognized as an entity responsive to immunotherapeutic interventions. Despite the success of the tyrosine kinase inhibitors (TKIs) in this disease, CML remains incurable. Only allogeneic bone marrow transplantation can provide long-term eradication of CML.

METHODS

This review summarizes the recent advances in the field of immunology in CML, specifically in tumor antigen discovery, that have been incorporated into the design of new clinical trials.

RESULTS

Multiple vaccine approaches are currently under clinical investigation. Recent laboratory and clinical data also point to a unique interaction of TKIs with the immune system.

CONCLUSIONS

A better understanding of these interactions combined with advances in the field of immunotherapy will likely lead to incorporation of TKIs in future therapeutic interventions to develop a cure for this disease.

Clonal expansion of T/NK-cells during tyrosine kinase inhibitor dasatinib therapy

Dasatinib, a broad-spectrum tyrosine kinase inhibitor (TKI), predominantly targets BCR-ABL and SRC oncoproteins and also inhibits off-target kinases, which may result in unexpected drug responses. We identified 22 patients with marked lymphoproliferation in blood while on dasatinib therapy. Clonality and immunophenotype were analyzed and related clinical information was collected. An abrupt lymphocytosis (peak count range 4-20 x 10(9)/l) with large granular lymphocyte (LGL) morphology was observed after a median of 3 months from the start of therapy and it persisted throughout the therapy. Fifteen patients had a cytotoxic T-cell and seven patients had an NK-cell phenotype. All T-cell expansions were clonal. Adverse effects, such as colitis and pleuritis, were common (18 of 22 patients) and were preceded by LGL lymphocytosis. Accumulation of identical cytotoxic T cells was also detected in pleural effusion and colon biopsy samples. Responses to dasatinib were good and included complete, unexpectedly long-lasting remissions in patients with advanced leukemia. In a phase II clinical study on 46 Philadelphia chromosome-positive acute lymphoblastic leukemia, patients with lymphocytosis had superior survival compared with patients without lymphocytosis. By inhibiting immunoregulatory kinases, dasatinib may induce a reversible state of aberrant immune reactivity associated with good clinical responses and a distinct adverse effect profile.

Targeted treatment of imatinib-resistant chronic myeloid leukemia: Focus on dasatinib

The efficacy of imatinib in chronic myeloid leukemia has been remarkable, but the development of resistance and the persistence of minimal residual disease have dampened the initial enthusiasm for this much heralded 'magic bullet'. Much progress has been made in elucidating the mechanisms which underlie imatinib resistance. The most common cause of such drug resistance is the selection of leukemic clones with point mutations in the Abl kinase domain leading to amino acid substitutions which prevent the appropriate binding of the drug. Other mechanisms include genomic amplification of BCR-ABL and modulation of drug efflux or influx transporters. Dasatinib is a multi-target kinase inhibitor which has increased potency and is able to inhibit most Bcr-Abl mutant cell lines. Clinical trials of dasatinib in imatinib-resistant and -intolerant chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoid leukemia have shown that it is effective and well tolerated. In this review, we will discuss the pre-clinical development of dasatinib, the clinical trial data demonstrating its efficacy and tolerability and highlight certain aspects of its toxicity profile and mechanisms of resistance.

Dasatinib inhibits recombinant viral antigen-specific murine CD4+ and CD8+ T-cell responses and NK-cell cytolytic activity in vitro and in vivo

OBJECTIVE

Dasatinib (BMS-354825) is a small molecule Src/Abl tyrosine kinase inhibitor approved for the treatment of chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia. Members of the Src family of kinases are involved in the induction of innate and adaptive immunity. The purpose of this study was to evaluate the inhibitory action of dasatinib on antigen-specific CD8(+) and CD4(+) T-cell function, as well as natural killer (NK) cell cytotoxicity.

MATERIALS AND METHODS

To assess dasatinib-mediated inhibition of antigen-specific T-cell proliferation, transgenic CD4(+) and CD8(+) T cells specific for ovalbumin were utilized. Endogenous CD4(+) and CD8(+) T-cell responses were determined following immunization of dasatinib-treated or control mice with a nonreplicating recombinant virus. Clearance of the RMA-S cells, a major histocompatibility complex (MHC) class I-deficient thymoma sensitive to NK-cell lysis, was analyzed in mice undergoing dasatinib treatment.

RESULTS

Dasatinib inhibited antigen-specific proliferation of murine CD4(+) and CD8(+) transgenic T cells in vitro and in vivo. Endogenous antigen-specific helper T-cell recall responses and induction of T-cell-mediated cytotoxicity following immunization with a nonreplicating recombinant virus were also inhibited. So to was the ability of NK cells to eliminate MHC class I-deficient cells in vivo.

CONCLUSIONS

These findings suggest that dasatinib has the potential to modulate the host immune response at clinical doses and highlights scope for off target applications, e.g., therapeutic immunosuppression in the context of autoimmune pathogenesis and allogeneic tissue transplantation.

Immunomodulatory effects of imatinib and second-generation tyrosine kinase inhibitors on T cells and dendritic cells: an update

The discovery of new drugs has occasionally led to a better understanding of biologic processes and unforeseen therapeutic applications. One such example is the new group of tyrosine kinase inhibitors, exemplified by the Bcr-Abl inhibitor imatinib (Glivec). In the last 10 years, these so-called 'small molecules' have started to enter the clinic with the promise of cancer treatments targeted at the underlying molecular changes that are responsible for specific malignant phenotypes. The aim of these small molecules has been to avoid the side-effects of systemic chemotherapies and the high morbidity/mortality risks associated with hematopoietic stem cell transplantation. Concurrently, however, increasing evidence has emerged to indicate that these drugs exert profound immunomodulatory effects on T cells and antigen-presenting cells, such as dendritic cells, which play major roles in immune tumor surveillance and the outcome of hematopoietic stem cell transplantation. Targeted tyrosine kinase inhibitor therapy may thus control cancer cell growth both directly and indirectly by changing the immunologic microenvironment. Furthermore, such molecules might help to unravel the complexities of the human immune system and could find therapeutic application in conditions as diverse as autoimmune diseases and certain infectious processes. In this brief review, we discuss recent developments in this fast evolving field.