Imatinib mesylate selectively impairs expansion of memory cytotoxic T cells without affecting the control of primary viral infections

Estrogenized HSA induced high-affinity autoantibodies in breast cancer - Novel biomarker for early detection

Objective

Breast cancer (BC) is the second most prevalent cancer worldwide. Estrogen has been increasingly recognized as a major contributor to the development of BC, playing a more critical role than previously understood. Estrogen derived nucleic acid and protein adducts have been shown to play significant roles in BC development and progression. However, the alterations in molecular mechanism(s) and immune pathways arising as a result of estrogenization still remain elusive.

Patients and methods

4-hydroxyestradiol (4-OHE2) was used for adduct formation with protein human serum albumin (HSA) (4-OHE2-HSA). The affinity of antibodies for 4-OHE2-HSA was evaluated in breast cancer patients. Immunoassays (direct binding ELISA, inhibition ELISA, and quantitative precipitin titration assay) were used to assess autoantibodies against estrogenized HSA in BC patients (n = 85) and healthy controls (n = 45).

Results

Estrogenization of HSA altered both its structure and function and compromised its interactions with various HSA-binding proteins. BC patients demonstrated high-affinity antibodies against 4-OHE2-HSA as compared to HSA (p < 0.05). Additionally, cytokines Interleukin (IL)-1, IL-6 and tumor necrosis factor-alpha (TNF-α) were significantly elevated in BC patients as compared to the control group. Several factors, such as chemotherapy, estrogen receptors (ERs), and combination of surgery and chemotherapy, influenced the production of antibodies in cancer patients. The affinity constant for estrogenized HSA was 1.31 × 10-7 M, while for HSA and 4-OHE2, it was 1.68 × 10-6 M and 1.36 × 10-6 M, respectively.

Conclusions

Estrogenized HSA is highly immunogenic, resulting in functional alterations. High affinity antibodies were detected in BC patients against 4-OHE2-HSA. Consequently, 4-OHE2-HSA may serve as a novel molecular target for potential cancer therapeutics. Furthermore, autoantibodies against 4-OHE2-HSA could serve as a potential biomarker for early detection of BC.

Tyrosine Kinase Inhibitors Do Not Promote a Decrease in SARS-CoV-2 Anti-Spike IgG after BNT162b2 Vaccination in Chronic Myeloid Leukemia: A Prospective Observational Study

We performed a prospective observational study of chronic myeloid leukemia (CML) patients after anti-SARS-CoV-2 BNT162b2 vaccination (VC). In total, 32 CML patients with tyrosine kinase inhibitor (TKI) therapy, 10 CML patients with treatment-free remission, and 16 healthy subjects participated in the study. From April 2021 to September 2021, all cases (median age = 58 years) were vaccinated twice. Immunoglobulin G for SARS-CoV-2 spike protein (S-IgG) was measured at three timepoints (before the first VC, 1−5 weeks after the second VC (T1), and approximately 6 months after the second VC (T2)). S-IgG was not observed before the first VC in any participant. At T1, all cases had acquired S-IgG. There were no significant differences in S-IgG levels among groups. A paired sample comparison of median S-IgG titers between T1 and T2 in all groups showed a significant reduction in T2 S-IgG titers. There were no significant differences in S-IgG levels among groups. When all patients were analyzed, those aged ≥58 years had significantly lower S-IgG levels than those aged <58 years at T1. The BNT162b2 vaccine was highly effective in CML patients with or without TKIs, and S-IgG levels were as persistent as those in healthy individuals.

The INVENT COVID trial: a structured protocol for a randomized controlled trial investigating the efficacy and safety of intravenous imatinib mesylate (Impentri®) in subjects with acute respiratory distress syndrome induced by COVID-19

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has led to a disruptive increase in the number of intensive care unit (ICU) admissions with acute respiratory distress syndrome (ARDS). ARDS is a severe, life-threatening medical condition characterized by widespread inflammation and vascular leak in the lungs. Although there is no proven therapy to reduce pulmonary vascular leak in ARDS, recent studies demonstrated that the tyrosine kinase inhibitor imatinib reinforces the endothelial barrier and prevents vascular leak in inflammatory conditions, while leaving the immune response intact.

METHODS

This is a randomized, double-blind, parallel-group, placebo-controlled, multicenter clinical trial of intravenous (IV) imatinib mesylate in 90 mechanically ventilated subjects with COVID-19-induced ARDS. Subjects are 18 years or older, admitted to the ICU for mechanical ventilation, meeting the Berlin criteria for moderate-severe ARDS with a positive polymerase chain reaction test for SARS-CoV2. Participants will be randomized in a 1:1 ratio to either imatinib (as mesylate) 200 mg bis in die (b.i.d.) or placebo IV infusion for 7 days, or until ICU discharge or death. The primary study outcome is the change in Extravascular Lung Water Index (EVLWi) between day 1 and day 4. Secondary outcome parameters include changes in oxygenation and ventilation parameters, duration of invasive mechanical ventilation, number of ventilator-free days during the 28-day study period, length of ICU stay, and mortality during 28 days after randomization. Additional secondary parameters include safety, tolerability, and pharmacokinetics.

DISCUSSION

The current study aims to investigate the efficacy and safety of IV imatinib in mechanically ventilated subjects with COVID-19-related ARDS. We hypothesize that imatinib decreases pulmonary edema, as measured by extravascular lung water using a PiCCO catheter. The reduction in pulmonary edema may reverse hypoxemic respiratory failure and hasten recovery. As pulmonary edema is an important contributor to ARDS, we further hypothesize that imatinib reduces disease severity, reflected by a reduction in 28-day mortality, duration of mechanical ventilation, and ICU length of stay.

TRIAL STATUS

Protocol version and date: V3.1, 16 April 2021. Recruitment started on 09 March 2021. Estimated recruitment period of approximately 40 weeks.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04794088 . Registered on 11 March 2021.

Imatinib Mesylate Exerted Antitumor Effect by Promoting Infiltration of Effector T Cells in Tumor

Imatinib mesylate is a potent tyrosine kinase inhibitor that may induce immunological effects, such as inhibition of immune suppressive cells; but, how it modulates the immune system remains to be completely elucidated. In this study, we showed that cell proliferation of CT26 colon cancer and Lewis lung carcinoma (3LL) lung cancer cells was not inhibited by imatinib in vitro, although its administration significantly suppressed the growth of CT26, but not 3LL, subcutaneous tumors, and prolonged survival in CT26 tumor-bearing mice. Further, we examined the expression of immune cell-related molecules in the tumors to elucidate the differences in imatinib-mediated antitumor effects between CT26 and 3LL tumors. The nCounter assay showed that the expression of CD8 and CD8⁺ T cell-recruiting chemokine genes was significantly elevated in imatinib-treated CT26 tumors than that in control tumors; however, the gene expression remained unchanged in imatinib-treated or control 3LL tumors. Furthermore, frequency of interferon-γ⁺ (IFN-γ⁺) CD8⁺ T cells was increased in imatinib-treated CT26 tumors than control tumors, indicating induction of antitumor immunity by imatinib. The analysis indicates that imatinib promotes infiltration of effector T cells in tumors by upregulating expression of cytokines that recruit CD8⁺ T cells in the tumor microenvironment, which may lead to a strong antitumor effect.

Hepatitis B Virus Reactivation in Gastrointestinal Stromal Tumor Patients Treated With Imatinib

Purpose

Hepatitis B virus reactivation (HBVr) in patients with gastrointestinal stromal tumors (GISTs) have not been sufficiently characterized. This study aimed to review the possible mechanism of HBVr induced by imatinib and explore appropriate measures for patient management and monitoring.

Methods

The clinical data of GIST patients who experienced HBVr due to treatment with imatinib at Xiangya Hospital (Changsha, Hunan, China) were retrospectively analyzed. A literature review was also conducted.

Results

Five cases were analyzed, including 3 cases in this study. The average age of the patients was 61.8 y, with male preponderance (4 of 5 vs. 1 of 5). These patients received imatinib as adjuvant treatment (n=4) or as neoadjuvant treatment (n=1). Primary tumors were mostly located in the stomach (n=4) or rectum (n=1). High (n=3) or intermediate (n=1) recurrence risk was categorized using the postoperative pathological results (n=4). Imatinib was then started at 400 (n=4) or 200 mg (n=1) daily. Patients first reported abnormal liver function during the 2^th (n=1),6^th (n=3), or 10^th (n=1) month of treatment with imatinib. Some patients (n=4) discontinued imatinib following HBVr; notably, 1 month after discontinuation, 1 patient experienced HBVr. Antivirals (entecavir n=4, tenofovir n=1), artificial extracorporeal liver support (n=1), and liver transplant (n=1) were effective approaches to treating HBVr. Most patients (n=3) showed favorable progress, 1 patient underwent treatment, and 1 patient died due to severe liver failure induced by HBVr.

Conclusions

Although HBVr is a rare complication (6.12%), HBV screening should be conducted before starting treatment with imatinib in GIST patients. Prophylactic therapy for hepatitis B surface antigen positive patients, prompt antiviral treatment and cessation of imatinib are also necessary.

Case reports of chronic myeloid leukemia and tuberculosis: Is imatinib the link between the two?

Current standard of care for treatment of CML is based on tyrosine kinase inhibitors (TKI's). Imatinib is most frequently used first line tyrosine kinase inhibitor. Various side effects of TKI's are known, but some may still be unknown. We are reporting three cases of CML who developed tuberculosis while on treatment with imatinib or dasatinib. Two cases developed CNS tuberculosis and other one was tubercular pleural effusion. These cases indicate that imatinib and other TKI's probably interfere with immunological functions and predispose patients for tuberculosis.

Occurrence of lymphoplasmacytic lymphoma in a chronic myeloid leukemia patient following long-term treatment with tyrosine kinase inhibitors: A case report

INTRODUCTION

After tyrosine kinase inhibitors (TKIs) targeting BCR-ABL1 were introduced for the treatment of chronic myeloid leukemia, clinical outcomes have improved dramatically. However, together with the increase in the survival rate, a more frequent occurrence of secondary malignancies has been observed as well. TKIs have been demonstrated to be a risk factor of malignancies such as non-Hodgkin lymphoma, prostate cancer, and skin cancer. However, lymphoplasmacytic lymphoma (LPL) has never been reported as a secondary malignancy after TKI treatment in chronic myeloid leukemia (CML).

PATIENT CONCERNS

An 81-year-old male patient diagnosed with CML and treated with TKIs for a long period (15 years) was admitted due to a chief complaint of abdominal pain. A large abdominal mass was detected by imaging that included computed tomography.

DIAGNOSIS

LPL was confirmed from biopsies after ultrasonography and sigmoidoscopy. Serum IgM level was increased and M protein and monoclonal gammopathy, IgM_kappa light chain type were detected.

INTERVENTIONS

The patient received six cycles of R-CHOP chemotherapy.

OUTCOMES

After chemotherapy, he showed response. The sizes of the abdominal mass and lymph nodes decreased; moreover, serum M protein and IgM levels decreased, as well.

CONCLUSION

Herein, for the first time, we describe a patient who developed LPL as a secondary malignancy after administration of TKIs for the treatment of CML. Our observations indicate the importance of awareness of this secondary malignancy that can develop in CML patients treated with TKIs.

Vaccination With Live Attenuated Vaccines in Four Children With Chronic Myeloid Leukemia While on Imatinib Treatment

Chronic myeloid leukemia (CML) in childhood and adolescence is a rare malignancy that can successfully be treated with the tyrosine kinase inhibitor (TKI) imatinib. According to the current experience, treatment is necessary for years and, in the majority of cases, a lifelong approach is required to control the malignant disease. To what extent imatinib causes immunosuppression in different age cohorts is a controversial discussion. According to general medical recommendations, live vaccines are contraindicated in individuals treated with imatinib. However, a recent increase in the number of globally reported cases of measles has been observed and continues to rise. Due to the high contagiousness of the virus, near-perfect vaccination coverage (herd immunity of 93 to 95%) is required to effectively protect against measles resurgence-a scenario that is not realistic in many countries. When four teenagers with CML (median age 13 years, range 12-15) who were enrolled into pediatric trial CML-paed II while on imatinib treatment (median treatment duration 36 months, range 11-84) were identified without protective measles and/or varicella titers, we carefully balanced the risks of a live vaccination under immunosuppressive TKI medication against the benefit of being protected. The patients underwent live vaccination with the live attenuated vaccines M-M-RVAX Pro® and Varivax® simultaneously (Patient #1), Priorix® and Varilix® consecutively (Patient #2), and Priorix® (Patients #3 and #4). While the first three patients were vaccinated while receiving TKI therapy, treatment with imatinib was interrupted in patient #4 for 1 week prior and 2 weeks after vaccination. Patients #1 and #3 reacted with stable long-term seroconversion. In Patient #2, serum titer conversion against measles and varicella could not be demonstrated and thus revaccination with Priorix® and Varilix® was performed 3 years later. However, protective titers did not develop or were lost again. Patient #4 also lost protective titers against measles when assessed 10 months after vaccination, but revaccination resulted in stable seroprotective titers over 12 months after the last vaccination during ongoing imatinib treatment. We conclude that in all patients, the safety of live vaccines could be documented, as no acute or late adverse events were observed. However, in line with observations that memory B-cells are lost under exposure to imatinib, revaccination may become necessary (two out of four patients in this small series lost their seroprotection). Considering that the number of cases is very small, we also suggest some criteria for decision-making regarding live vaccinations of CML patients treated with imatinib.

TNIK signaling imprints CD8+ T cell memory formation early after priming

Co-stimulatory signals, cytokines and transcription factors regulate the balance between effector and memory cell differentiation during T cell activation. Here, we analyse the role of the TRAF2-/NCK-interacting kinase (TNIK), a signaling molecule downstream of the tumor necrosis factor superfamily receptors such as CD27, in the regulation of CD8⁺ T cell fate during acute infection with lymphocytic choriomeningitis virus. Priming of CD8⁺ T cells induces a TNIK-dependent nuclear translocation of β-catenin with consecutive Wnt pathway activation. TNIK-deficiency during T cell activation results in enhanced differentiation towards effector cells, glycolysis and apoptosis. TNIK signaling enriches for memory precursors by favouring symmetric over asymmetric cell division. This enlarges the pool of memory CD8⁺ T cells and increases their capacity to expand after re-infection in serial re-transplantation experiments. These findings reveal that TNIK is an important regulator of effector and memory T cell differentiation and induces a population of stem cell-like memory T cells.

Coordinate expression of multiple factors play critical roles in the regulation between effector and memory CD8⁺ T cell differentiation. Here the authors show upon acute viral infection TNIK is critically required as a regulator of effector and memory T cell differentiation.

B lymphocytes protect islet β cells in diabetes prone NOD mice treated with imatinib

Imatinib (Gleevec) reverses type 1 diabetes (T1D) in NOD mice and is currently in clinical trials in individuals with recent-onset disease. While research has demonstrated that imatinib protects islet β cells from the harmful effects of ER stress, the role the immune system plays in its reversal of T1D has been less well understood, and specific cellular immune targets have not been identified. In this study, we demonstrate that B lymphocytes, an immune subset that normally drives diabetes pathology, are unexpectedly required for reversal of hyperglycemia in NOD mice treated with imatinib. In the presence of B lymphocytes, reversal was linked to an increase in serum insulin concentration, but not an increase in islet β cell mass or proliferation. However, improved β cell function was reflected by a partial recovery of MafA transcription factor expression, a sensitive marker of islet β cell stress that is important to adult β cell function. Imatinib treatment was found to increase the antioxidant capacity of B lymphocytes, improving reactive oxygen species (ROS) handling in NOD islets. This study reveals a novel mechanism through which imatinib enables B lymphocytes to orchestrate functional recovery of T1D β cells.

Immunological effects of nilotinib prophylaxis after allogeneic stem cell transplantation in patients with advanced chronic myeloid leukemia or philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic stem cell transplantation remains the standard treatment for resistant advanced chronic myeloid leukemia and Philadelphia chromosome–positive acute lymphoblastic leukemia. Relapse is the major cause of treatment failure in both diseases. Post-allo-SCT administration of TKIs could potentially reduce relapse rates, but concerns regarding their effect on immune reconstitution have been raised. We aimed to assess immune functions of 12 advanced CML and Ph+ ALL patients who received post-allo-SCT nilotinib. Lymphocyte subpopulations and their functional activities including T-cell response to mitogens, NK cytotoxic activity and thymic function, determined by quantification of the T cell receptor (TCR) excision circles (TREC) and TCR repertoire, were evaluated at several time points, including pre-nilotib-post-allo-SCT, and up to 365 days on nilotinib treatment. NK cells were the first to recover post allo-SCT. Concomitant to nilotinib administration, total lymphocyte counts and subpopulations gradually increased. CD8 T cells were rapidly reconstituted and continued to increase until day 180 post SCT, while CD4 T cells counts were low until 180−270 days post nilotinib treatment. T-cell response to mitogenic stimulation was not inhibited by nilotinib administration. Thymic activity, measured by TREC copies and surface membrane expression of 24 different TCR Vβ families, was evident in all patients at the end of follow-up after allo-SCT and nilotinib treatment. Finally, nilotinib did not inhibit NK cytotoxic activity. In conclusion, administration of nilotinib post allo-SCT, in attempt to reduce relapse rates or progression of Ph+ ALL and CML, did not jeopardize immune reconstitution or function following transplantation.

Evaluation of Cell-Mediated Immune Function Using the Cytotoxic T-Lymphocyte Assay

Evaluation of cell-mediated immunity (CMI) is a significant component in any assessment designed to predict the full range of potential immunotoxic risk underlying health risks. Among measures of CMI, the cytotoxic T-lymphocyte (CTL) response is recognized as perhaps the most relevant functional measure that reflects cell-mediated acquired immune defense against viral infections and cancer. The CTL response against T-dependent antigens requires the cooperation of at least three different major categories of immune cells. These include professional antigen-presenting cells (e.g., dendritic cells), CD4⁺ T helper lymphocytes, and CD8⁺ T effector lymphocytes. It is also among the few functional responses dependent on and, hence, capable of evaluating effective antigen presentation via both class I and class II molecules of the major histocompatibility complex (MHC). For this reason, the CTL assay is an excellent candidate for evaluation of potential immunotoxicity. This chapter provides an example of a mouse CTL assay against influenza virus that has been utilized for this purpose.

Increase of T and B cells and altered BACH2 expression patterns in bone marrow trephines of imatinib-treated patients with chronic myelogenous leukaemia

The effect of imatinib on T and B cells in patients with chronic myelogenous leukaemia (CML) is not well understood. An upregulation of the transcription factor Broad-complex-Tramtrack-Bric-a-Brac and Cap‘n’collar 1 bZip transcription factor 2 (BACH2), which is involved in the development and differentiation of B cells, was demonstrated in a CML cell line treated with imatinib. The present study retrospectively analysed the expression and distribution of cluster of differentiation (CD)3, CD20 and BACH2 (per 1,000 cells), as well as the co-expression of CD20 and BACH2, using immunohistochemistry in serial bone marrow trephines obtained from 14 CML patients treated with imatinib in comparison to 17 patients with newly diagnosed CML and 6 control trephines. Bone marrow trephines of CML patients in remission under imatinib therapy exhibited significantly higher numbers of CD3 and CD20 infiltrates (partly ordered in aggregates) compared with patients with newly diagnosed CML and control individuals. Similarly, nuclear expression of BACH2 in granulopoietic cells was increased in CML patients treated with imatinib, which may represent the histological correlate of the positive treatment effect. Furthermore, since BACH2 is involved in B cell development, its altered expression patterns by imatinib may be one explanation for high B cell numbers, as revealed by CD20/BACH2 (nuclear)-positive cells. As the present data are preliminary, future prospective studies are required to assess the prognostic and predictive role of BACH2 in patients with CML under targeted therapy.

[Guidelines for vaccination of immunocompromised individuals]

Immunosuppression of various origins is associated with an increased risk of infection; therefore the prevention of infectious diseases by vaccination is especially important in immunocompromised patients. However, the response to vaccinations is often reduced in these risk groups and the application of live vaccines is contraindicated during immunosuppression.In the following expert statement, recommendations for vaccination were created on the basis of current evidence and theoretical/immunological considerations. A first, general part elaborates on efficacy and safety of vaccinations during immunosuppression, modes of action of immunosuppressive medications and recommended time intervals between immunosuppressive treatments and vaccinations. A core piece of this part is a graduation of immunosuppression into three stages, i. e. no relevant immunosuppression, mild to moderate and severe immunosuppression and the assignment of various medications (including biologicals) to one of those stages; this is followed by an overview of possible and necessary vaccinations in each of those stages.The second part gives detailed vaccination guidelines for common diseases and therapies associated with immunosuppression. Primary immune deficiencies, chronic kidney disease, diabetes mellitus, solid and hematological tumors, hematopoetic stem cell transplantation, transplantation of solid organs, aspenia, rheumatological-, gastroenterologic-, dermatologic-, neurologic diseases, biologicals during pregnancy and HIV infection are dealt with.These vaccination guidelines, compiled for the first time in Austria, aim to be of practical help for physicians to facilitate and improve vaccination coverage in immunocompromised patients and their household members and contact persons.

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.

Tuberculous and non-tuberculous granulomatous lymphadenitis in patients receiving imatinib mesylate (glivec) for metastatic gastrointestinal stromal tumor

Background

Imatinib mesylate (IM) is the standard treatment for BCR-ABL-positive chronic myelogenous leukemia (CML) and is the first-line adjuvant and palliative treatment for metastatic and inoperable gastrointestinal stromal tumor (GIST). IM is not known to be associated with an increased risk for development of granulomatous diseases.

Methods

We describe our experience with 2 patients (42 and 62 years of age) who developed granulomatous disease during IM treatment for metastatic GIST.

Results

Mean duration of IM treatment was 12 (range 8–16) months. Enlarged lymph nodes with increased metabolism on FDG-PET-CT examination were detected and resected. Affected sites were supraclavicular (1) and subcarinal/mediastinal (1) lymph nodes. Histological examination revealed caseating and non-caseating granulomas suggestive of tuberculosis and sarcoidosis, respectively. Mycobacterium tuberculosis was detected by PCR in lymph nodes of 1 patient who was then successfully treated by anti-tuberculous agents. The other patient had negative sputum test for acid-fast bacilli and PCR-DNA-analysis was negative for M. tuberculosis and other mycobacteria. He received no anti-tuberculous therapy and had no evidence of progressive lymphadenopathy or new lung lesions during follow-up.

Conclusion

Our observations underline the necessity to obtain biopsy material from enlarged or metabolically active lymph nodes developing during IM treatment for timely diagnosis and appropriate treatment of these rare complications. Follow-up without treatment is safe for patients without detectable microorganisms by sputum examination and PCR.

Cytotoxic T cells induce proliferation of chronic myeloid leukemia stem cells by secreting interferon-γ

Chronic myeloid leukemia (CML) is a clonal myeloproliferative neoplasia arising from the oncogenic break point cluster region/Abelson murine leukemia viral oncogene homolog 1 translocation in hematopoietic stem cells (HSCs), resulting in a leukemia stem cell (LSC). Curing CML depends on the eradication of LSCs. Unfortunately, LSCs are resistant to current treatment strategies. The host's immune system is thought to contribute to disease control, and several immunotherapy strategies are under investigation. However, the interaction of the immune system with LSCs is poorly defined. In the present study, we use a murine CML model to show that LSCs express major histocompatibility complex (MHC) and co-stimulatory molecules and are recognized and killed by leukemia-specific CD8(+) effector CTLs in vitro. In contrast, therapeutic infusions of effector CTLs into CML mice in vivo failed to eradicate LSCs but, paradoxically, increased LSC numbers. LSC proliferation and differentiation was induced by CTL-secreted IFN-γ. Effector CTLs were only able to eliminate LSCs in a situation with minimal leukemia load where CTL-secreted IFN-γ levels were low. In addition, IFN-γ increased proliferation and colony formation of CD34(+) stem/progenitor cells from CML patients in vitro. Our study reveals a novel mechanism by which the immune system contributes to leukemia progression and may be important to improve T cell-based immunotherapy against leukemia.

Abelson tyrosine kinase controls phagosomal acidification required for killing of Mycobacterium tuberculosis in human macrophages

The mechanisms that regulate the acidification of intracellular compartments are key to host defense against pathogens. In this paper, we demonstrate that Abl tyrosine kinase, a master switch for cell growth and trafficking of intracellular organelles, controls the acidification of lysosomes in human macrophages. Pharmacological inhibition by imatinib and gene silencing of Abelson (Abl) tyrosine kinase reduced the lysosomal pH in human macrophages by increasing the transcription and expression of the proton pumping enzyme vacuolar-type H(+)-adenosine triphosphatase. Because lysosomal acidification is required for antimicrobial activity against intracellular bacteria, we determined the effect of imatinib on the growth of the major human pathogen Mycobacterium tuberculosis. Imatinib limited the multiplication of M. tuberculosis, and growth restriction was dependent on acidification of the mycobacterial compartment. The effects of imatinib were also active in vivo because circulating monocytes from imatinib-treated leukemia patients were more acidic than monocytes from control donors. Importantly, sera from imatinib-treated patients triggered acidification and growth restriction of M. tuberculosis in macrophages. In summary, our results identify the control of phagosomal acidification as a novel function of Abl tyrosine kinase and provide evidence that the regulation occurs on the level of the vacuolar-type H(+)-adenosine triphosphatase. Given the efficacy of imatinib in a mouse model of tuberculosis and our finding that orally administered imatinib increased the ability of human serum to trigger growth reduction of intracellular M. tuberculosis, clinical evaluation of imatinib as a complementary therapy of tuberculosis, in particular multidrug or extremely drug-resistant disease, is warranted.

Imatinib-sensitive tyrosine kinases regulate mycobacterial pathogenesis and represent therapeutic targets against tuberculosis

The lengthy course of treatment with currently used antimycobacterial drugs and the resulting emergence of drug-resistant strains have intensified the need for alternative therapies against Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis. We show that Mtb and Mycobacterium marinum use ABL and related tyrosine kinases for entry and intracellular survival in macrophages. In mice, the ABL family tyrosine kinase inhibitor, imatinib (Gleevec), when administered prophylactically or therapeutically, reduced both the number of granulomatous lesions and bacterial load in infected organs and was also effective against a rifampicin-resistant strain. Further, when coadministered with current first-line drugs, rifampicin or rifabutin, imatinib acted synergistically. These data implicate host tyrosine kinases in entry and intracellular survival of mycobacteria and suggest that imatinib may have therapeutic efficacy against Mtb. Because imatinib targets host, it is less likely to engender resistance compared to conventional antibiotics and may decrease the development of resistance against coadministered drugs.

Sunitinib inhibits the phosphorylation of platelet-derived growth factor receptor β in the skin of mice with scleroderma-like features and prevents the development of the disease

OBJECTIVE

Systemic sclerosis (SSc) is characterized by fibrosis of the skin and visceral organs, vascular dysfunction, and immunologic dysregulation. Platelet-derived growth factors (PDGFs) have been implicated in the development of fibrosis and dysregulation of vascular function. We investigated the effects of sunitinib and sorafenib, two tyrosine kinase inhibitors that interfere with PDGF signaling, in a mouse model of diffuse SSc.

METHODS

SSc was induced in BALB/c mice by subcutaneous injections of HOCl daily for 6 weeks. Mice were randomized to treatment with sunitinib, sorafenib, or vehicle. The levels of native and phosphorylated PDGF receptor β (PDGFRβ) and vascular endothelial growth factor receptor (VEGFR) in the skin were assessed by Western blot and immunohistochemical analyses. Skin and lung fibrosis were evaluated by histologic and biochemical methods. Autoantibodies were detected by enzyme-linked immunosorbent assay, and spleen cell populations were analyzed by flow cytometry.

RESULTS

Phosphorylation of PDGFRβ and VEGFR was higher in fibrotic skin from HOCl-injected mice with SSc than from PBS-injected mice. Injections of HOCl induced cutaneous and lung fibrosis, increased the proliferation rate of fibroblasts in areas of fibrotic skin, increased splenic B cell and T cell counts, and increased anti-DNA topoisomerase I autoantibody levels in BALB/c mice. All of these features were reduced by sunitinib but not by sorafenib. Sunitinib significantly reduced the phosphorylation of both PDGF and VEGF receptors.

CONCLUSION

Inhibition of the hyperactivated PDGF and VEGF pathways by sunitinib prevented the development of fibrosis in HOCl-induced murine SSc and may represent a new SSc treatment for testing in clinical trials.

Antigens in chronic myeloid leukemia: implications for vaccine development

Treatment with imatinib mesylate and other tyrosine kinase inhibitors (TKI) revolutionized the therapy of chronic myeloid leukemia (CML). However, it alone does not cure this disease. Moreover, some patients develop resistance or adverse effects to this therapy. As successful treatment of a portion of CML patients by hematopoietic stem cell transplantation (HSCT) suggests the importance of immune mechanisms in the elimination of leukemic cells, including leukemia stem cells, TKI administration or HSCT might be combined with vaccination to cure CML patients. However, antigens implicated in the immune responses have not yet been sufficiently identified. Therefore, in this report, we compiled and characterized a list of 165 antigens associated with CML (CML-Ag165) and analyzed the expression of the corresponding genes in CML phases, subpopulations of leukemic cells, and CML-derived cell lines using available datasets from microarray transcriptional-profiling studies. From the CML-Ag165 list, we selected antigens most suitable for vaccine development and evaluated their appropriate characteristics.

Novel treatment concepts for graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) are potentially lethal complications after stem cell transplantation (SCT). Steroids are the appropriate first-line treatment for both. However, if patients do not adequately benefit from steroid therapy, mortality is high and standardized treatment algorithms are lacking. This is mainly because of limited data from prospective, randomized clinical trials. In addition, most of the available treatment options only induce clinical benefits in a limited proportion of patients. Thus, there is an urgent clinical need to develop more potent immunosuppressive treatment strategies for patients suffering from acute or chronic steroid-refractory GVHD while maintaining the graft versus tumor effect to avoid a potential rise in relapse-related mortality. The increasing knowledge about host- as well as donor-derived variables favoring GVHD development and the increasing armamentarium of immune-modulatory agents entering preclinical and clinical research will probably allow more effective treatment of GVHD in the future. This review describes novel developments in the treatment of steroid-refractory GVHD, with a special focus on the rationale behind promising pharmacologic compounds or up-coming cellular therapies.

Small-molecule protein kinase inhibitors and their effects on the immune system: implications for cancer treatment

Oncogenic signaling pathways have emerged as key targets for the development of small-molecule inhibitors, with several protein kinase inhibitors already in clinical use for cancer patients. In addition to their role in tumorigenesis, many of the molecules and signaling pathways targeted by these inhibitors are also important in the signaling and interaction of immune cells, such as T cells and dendritic cells. Not surprisingly, there is increasing evidence that many of these inhibitors can have a substantial impact on immune function, both stimulating and downregulating an immune response. In order to illustrate the important role of signaling molecule inhibition in the modulation of immune function, we will discuss the exemplary pathways MAPK, AKT-PI3K-mTOR and VEGF-VEGFR, as well as selected small-molecule inhibitors, whose impact on immune cells has been studied more extensively.

Immunocompetent cell functions in Ph+ acute lymphoblastic leukemia patients on prolonged Imatinib maintenance treatment

Imatinib mesylate (Imatinib) is a potent inhibitor of defined tyrosine kinases and is effectively used for the treatment of malignancies characterized by the constitutive activation of these tyrosine kinases, such as Philadelphia chromosome-positive (Ph(+)) leukemias and gastrointestinal stromal tumors. Suppressive as well as stimulating effects of this drug on T lymphocytes or dendritic cells (DC), which play a major role in immune tumor surveillance, have been reported. For this reason, we questioned whether Imatinib could also affect the phenotypic and functional properties of these subpopulations in Ph(+) acute lymphoblastic leukemia (ALL) patients on prolonged Imatinib maintenance treatment. Circulating T lymphocytes and NK cells from Imatinib-treated Ph(+) ALL patients showed a subset distribution comparable to that of healthy donors. In addition, T-cell immunomodulant cytokine production (IFN-γ, TNF-α) and proliferative responses were not impaired. A normal monocyte-derived DC differentiation and apoptotic body loading capacity was also observed in the majority of Imatinib-treated patients. In contrast, an impairment in the DC intracellular production of IL-12 was recorded, although this was not observed when normal DC were exposed in vitro to Imatinib. Finally, in vivo Imatinib treatment did not affect the T-lymphocyte proliferation and IFN-γ production induced by leukemic apoptotic body-loaded DC, underling the potential capability of these cells to generate a specific immune response against tumoral antigens. Taken together, these findings provide evidence that immunotherapeutic approaches aimed at controlling residual disease in Ph(+) ALL patients in hematologic remission are not jeopardized by the long-term administration of Imatinib.

Chronic myelogenous leukemia maintains specific CD8(+) T cells through IL-7 signaling

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease of hematopoietic stem cells. The disease progresses after several years from an initial chronic phase to a blast phase. Leukemia-specific T cells are regularly detected in CML patients and may be involved in the immunological control of the disease. Here, we analyzed the role of leukemia-specific CD8(+) T cells in CML disease control and the mechanism that maintains CD8(+) T-cell immunosurveillance in a retroviral-induced murine CML model. To study antigen-specific immune responses, the glycoprotein of the lymphocytic choriomeningitis virus was used as model leukemia antigen. Leukemia-specific CTL activity was detectable in vivo in CML mice and depletion of CD8(+) T cells rapidly led to disease progression. CML-specific CTL were characterized by the expression of the IL-7 receptor α-chain. In addition, leukemia cells produced IL-7 that was crucial for the maintenance of leukemia-specific CTL and for disease control. Therefore, CML cells maintain the specific CD8(+) T-cell-mediated immune control by IL-7 secretion. This results in prolonged control of disease and probably contributes to the characteristic chronic phase of the disease.

Changes of immunological profiles in patients with chronic myeloid leukemia in the course of treatment

In the previous paper of ours we compared, prior to start any treatment, a number of immunological parameters in 24 chronic myeloid leukemia patients with the same number of healthy subjects matched by age and sex. We found significant differences in the levels of immunoglobulins, the C4 component of complement, the C-reactive protein, interleukin 6, the composition of lymphocyte population and the production of some cytokines by stimulated CD3+ cells. Eleven of these patients were followed longitudinally. After treatment with hydroxyurea, interferon alpha, imatinib mesylate and dasatinib, or various combinations thereof, hematological remission was achieved in all patients and complete cytogenetic remission in nine of them. There was a nearly general tendency towards normalization of the abnormalities observed in the patients at their enrollment.

Repeated vaccination is required to optimize seroprotection against H1N1 in the immunocompromised host

BACKGROUND

In 2009 the declaration by the World Health Organization of a global pandemic of influenza-H1N1 virus led to a vaccination campaign to ensure protection for immunocompromised patients. The goal of this study was to determine the efficacy of the 2009 H1N1 vaccine in patients with hematologic malignancies.

DESIGN AND METHODS

We evaluated humoral and cellular immune responses to 2009 H1N1 vaccine in 97 adults with hematologic malignancies and compared these responses with those in 25 adult controls. Patients received two injections of vaccine 21 days apart and the controls received one dose. Antibody titers were measured using a hemagglutination-inhibition assay on days 0, 21 and 49 after injection of the first dose. Cellular immune responses to H1N1 were determined on days 0 and 49.

RESULTS

By day 21 post-vaccination, protective antibody titers of 1:32 or more were seen in 100% of controls compared to 39% of patients with B-cell malignancies (P<0.001), 46% of allogeneic stem cell transplant recipients (P<0.001) and 85% of patients with chronic myeloid leukemia (P=0.086). After a second dose, seroprotection rates increased to 68%, (P=0.008), 73%, (P=0.031), and 95% (P=0.5) in patients with B-cell malignancies, after allogeneic stem cell transplantation and with chronic myeloid leukemia, respectively. On the other hand, T-cell responses to H1N1 vaccine were not significantly different between patients and controls.

CONCLUSIONS

These data demonstrate the efficacy of H1N1 vaccine in most patients with hematologic malignancies and support the recommendation for the administration of two doses of vaccine in immunocompromised patients. These results may contribute towards the development of evidence-based guidelines for influenza vaccination in such patients in the future.

Anti-inflammatory M2 type macrophages characterize metastasized and tyrosine kinase inhibitor-treated gastrointestinal stromal tumors

We have made a detailed inventory of the immune infiltrate of gastrointestinal stromal tumors (GISTs), which originate from mesenchymal cells in the intestinal tract. These sarcomas are heavily infiltrated with macrophages and T cells, while immune cells of other lineages were much less abundant. Dissecting the functional subtypes of T cells with multicolor fluorescent microscopy revealed substantial populations of cytotoxic T cells, helper T cells and FoxP3(+) regulatory T cells. The balance of cytotoxic T cells and FoxP3(+) T cells was toward immune suppression. Analysis of the macrophage population also showed a dominance of anti-inflammatory cells, as the M2 type scavenger receptor CD163 was abundantly present. Other subsets of macrophages (CD14(+)CD163(-)) were occasionally detected. M2 type CD163(+) macrophages were associated with the number of infiltrating FoxP3(+) regulatory T cells and twice as many macrophages were found in metastatic GIST compared to primary lesions. Most metastatic GISTs had been treated with the tyrosine kinase inhibitors imatinib and sunitinib, but the high macrophage infiltrate was not related to this treatment. However, imatinib and sunitinib did induce secretion of anti-inflammatory IL-10 in macrophage cultures, indicating that treatment with these inhibitors might contribute to an immune suppressive microenvironment in GIST. Overall, our data reveal a picture of GIST as an active site of tumor-immune interaction in which suppressive mechanisms overrule potential antitumor responses. Tyrosine kinase inhibitors might promote this negative balance.

Targeting immune suppressing myeloid-derived suppressor cells in oncology

Emerging data suggests that host immune cells with a suppressive phenotype represent a significant hurdle to successful therapy for metastatic cancer. Among the suppressor cells, T regulatory cells (Treg) and myeloid-derived suppressor cells (MDSC) are significantly increased in hosts with advanced malignancies. MDSC mediate the suppression of the tumor antigen-specific T cell response through the induction of T cell anergy and the development of Treg in tumor-bearing mice. These results provide robust evidence of an in vivo immunoregulatory function of MDSC in the establishment of tumor antigen-specific tolerance and the development of Treg in tumor-bearing hosts. To achieve effective anti-tumor immunity, tumor-induced immunosuppression must be reversed. Our preliminary results indicate that c-kit ligand (stem cell factor) expressed by tumor cells may be required for MDSC accumulation in tumor-bearing mice, and that blocking the c-kit ligand/c-kit receptor interaction can prevent the development of Treg and reverse immune tolerance induced by MDSC. Since c-kit can be readily inhibited by several small molecule inhibitors including imatinib, sunitinib and dasatinib, targeting immune suppressing cells can be readily accomplished in the clinic.

The effect of imatinib on cytomegalovirus reactivation in hematopoietic cell transplantation

In vitro studies have shown possible antiviral effects of tyrosine kinase inhibitors. In a retrospective study, we show that use of the tyrosine kinase inhibitor imatinib does not appear to reduce cytomegalovirus reactivation during the first 100 days after transplantation in a cohort of hematopoietic cell transplant recipients.

The cytotoxic T lymphocyte assay for evaluating cell-mediated immune function

Evaluation of cell-mediated immunity (CMI) is a significant component in any assessment designed to predict the full range of potential immunotoxic risk underlying health risks. Among measures of CMI, the cytotoxic T Lymphocyte (CTL) response is recognized as perhaps the most relevant functional measure that reflects cell-mediated acquired immune defense against viral infections and cancer. The CTL response against T-dependent antigens requires the cooperation of at least three different major categories of immune cells. These include professional antigen presenting cells (e.g., dendritic cells), CD4(+) T helper lymphocytes, and CD8(+) T effector lymphocytes. It is also among the few functional responses dependent on and, hence, capable of evaluating effective antigen presentation via both class I and class II molecules of the major histocompatibility complex (MHC). For this reason the CTL assay is an excellent candidate for evaluation of potential immunotoxicity. This chapter provides an example of a mouse CTL assay against influenza virus that has been utilized for this purpose.

Strategies to modulate immune responses: a new frontier for gene therapy

The success of gene therapy strategies to cure disease relies on the control of unwanted immune responses to transgene products, genetically modified cells and/or to the vector. Effective treatment of an established immune response is much harder to achieve than prevention of a response before it has had a chance to develop. However, preventive strategies are not always effective in avoiding immune responses, thus the use of drugs to induce immunosuppression (IS) is required. The growing discovery of novel drugs provides a conceptual shift from using generalized, moderately intensive immunosuppressive regimens towards a refined approach to attain the optimal balance of naive cells, effector cells, memory cells, and regulatory cells, harnessing the natural tolerance mechanisms of the body. We review several strategies based on transient IS coupled with gene therapy for sustained immune tolerance induction to the therapeutic transgene.

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.

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.

Defective homing and impaired induction of cytotoxic T cells by BCR/ABL-expressing dendritic cells

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease arising from a hematopoietic stem cell expressing the BCR/ABL fusion protein. Leukemic and dendritic cells (DCs) develop from the same transformed hematopoietic progenitors. How BCR/ABL interferes with the immunoregulatory function of DCs in vivo is unknown. We analyzed the function of BCR/ABL-expressing DCs in a retroviral-induced murine CML model using the glycoprotein of lymphocytic choriomeningitis virus as a model leukemia antigen. BCR/ABL-expressing DCs were found in bone marrow, thymus, spleen, lymph nodes, and blood of CML mice. They were characterized by a low maturation status and induced only limited expansion of naive and memory cytotoxic T lymphocytes (CTLs). In addition, immunization with in vitro–generated BCR/ABL-expressing DCs induced lower frequencies of specific CTLs than immunization with control DCs. BCR/ABL-expressing DCs preferentially homed to the thymus, whereas only few BCR/ABL-expressing DCs reached the spleen. Our results indicate that BCR/ABL-expressing DCs do not efficiently induce CML-specific T-cell responses resulting from low DC maturation and impaired homing to secondary lymphoid organs. In addition, BCR/ABL-expressing DCs in the thymus may contribute to CML-specific tolerance induction of specific CTLs.

Programmed death 1 signaling on chronic myeloid leukemia-specific T cells results in T-cell exhaustion and disease progression

Chronic myeloid leukemia (CML) is a malignant myeloproliferative disease with a characteristic chronic phase (cp) of several years before progression to blast crisis (bc). The immune system may contribute to disease control in CML. We analyzed leukemia-specific immune responses in cpCML and bcCML in a retroviral-induced murine CML model. In the presence of cpCML and bcCML expressing the glycoprotein of lymphocytic choriomeningitis virus as a model leukemia antigen, leukemia-specific cytotoxic T lymphocytes (CTLs) became exhausted. They maintained only limited cytotoxic activity, and did not produce interferon-gamma or tumor necrosis factor-alpha or expand after restimulation. CML-specific CTLs were characterized by high expression of programmed death 1 (PD-1), whereas CML cells expressed PD-ligand 1 (PD-L1). Blocking the PD-1/PD-L1 interaction by generating bcCML in PD-1-deficient mice or by repetitive administration of alphaPD-L1 antibody prolonged survival. In addition, we found that PD-1 is up-regulated on CD8(+) T cells from CML patients. Taken together, our results suggest that blocking the PD-1/PD-L1 interaction may restore the function of CML-specific CTLs and may represent a novel therapeutic approach for CML.

[Imatinib]

The progress in molecular targeting therapy includes two tides, namely, small molecule compounds and large molecule biological agents. Although the latter prevails in the field of clinical immunology, the former attracts more and more attention in these few years. Most of molecular targeting small compounds are the inhibitors of tyrosine kinases, including pioneering imatinib which inhibits the receptor for platelet-derived growth factor (PDGF), c-Abl, etc. The therapeutic concentrations of imatinib almost completely abrogated the morphological alteration and proliferation of fibroblastic cells induced by PDGF stimulation in 3-dimensional culture system in vitro. Indeed, imatinib has been shown to be effective in various animal disease models for arthritis, interstitial pneumonia, glomerulonephritis, and pulmonary hypertension. Furthermore, its efficacy in patients with systemic sclerosis has been recently reported from several institutes. Since established treatments had not been found for fibrotic lesion before, imatinib, a dual inhibitor of both transforming growth factor beta-, and PDGF-signaling, is likely to be a potent drug against fibrosis. Its efficacy and safety in fibrotic and immune-mediated diseases, such as systemic sclerosis, are currently under investigation throughout the world.

Imatinib mesylate inhibits CD4+ CD25+ regulatory T cell activity and enhances active immunotherapy against BCR-ABL- tumors

Imatinib mesylate (Gleevec, STI571), a selective inhibitor of a restricted number of tyrosine kinases, has been effectively used for the treatment of Philadelphia chromosome-positive leukemias and gastrointestinal stromal tumors. Imatinib may also directly influence immune cells. Suppressive as well as stimulating effects of this drug on CD4(+) and CD8(+) T lymphocytes or dendritic cells have been reported. In the current study, we have investigated the influence of imatinib mesylate on CD4(+)CD25(+)FoxP3(+) regulatory T cells (Treg), a critical population of lymphocytes that contributes to peripheral tolerance. Used at concentrations achieved clinically, imatinib impaired Treg immunosuppressive function and FoxP3 expression but not production of IL-10 and TGF-beta in vitro. Imatinib significantly reduced the activation of the transcription factors STAT3 and STAT5 in Treg. Analysis of Treg TCR-induced signaling cascade indicated that imatinib inhibited phosphorylation of ZAP70 and LAT. Substantiating these observations, imatinib treatment of mice decreased Treg frequency and impaired their immunosuppressive function in vivo. Furthermore, imatinib mesylate significantly enhanced antitumor immune responses to dendritic cell-based immunization against an imatinib-resistant BCR-ABL negative lymphoma. The clinical applications of imatinib mesylate might thus be expanded with its use as a potent immunomodulatory agent targeting Treg in cancer immunotherapy.

Natural killer or natural killer/T cell lineage large granular lymphocytosis associated with dasatinib therapy for Philadelphia chromosome positive leukemia

Dasatinib, a dual tyrosine kinase inhibitor, is known to modulate or suppress T-cell activation and proliferation. We report a series of 8 patients who developed chronic peripheral lymphocytosis, identified as natural killer cells or natural killer/T-cells based on their large granular lymphocyte morphologies and CD16(+), CD56(+), CD3(-) or CD3(+) immunophenotypic profiles, out of 18 patients receiving dasatinib therapy. All cases that developed large granular lymphocyte lymphocytosis achieved optimal molecular response (8/8 in large granular lymphocyte(+) patients vs. 3/10 in large granular lymphocyte(-) patients, p=0.002). A (51)Cr release assay demonstrated that natural killer cell cytotoxicity has been enhanced in a case of large granular lymphocyte lymphocytosis compared to normal healthy donors, and that natural killer cell cytotoxicity in dasatinib-responders was superior to that in non-responders. In summary, the present study suggests that natural killer or natural killer/T cell lineage large granular lymphocyte lymphocytosis develops in association with dasatinib therapy and that large granular lymphocyte might have a therapeutic effect on Ph(+) leukemic cells.

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.

Tyrosine kinase inhibitors reverse type 1 diabetes in nonobese diabetic mice

The recent development of small-molecule tyrosine kinase (TK) inhibitors offers increasing opportunities for the treatment of autoimmune diseases. In this study, we investigated the potential of this new class of drugs to treat and cure type 1 diabetes (T1D) in the NOD mouse. Treatment of prediabetic and new onset diabetic mice with imatinib (Gleevec) prevented and reversed T1D. Similar results were observed with sunitinib (Sutent), an additional approved multikinase inhibitor, suggesting that the primary target of imatinib, c-Abl, was not essential in blocking disease in this model. Additional studies with another TK inhibitor, PLX647 (targeting c-Kit and c-Fms) or an anti-c-Kit mAb showed only marginal efficacy whereas a soluble form of platelet-derived growth factor receptor (PDGFR), PDGFRbetaIg, rapidly reversed diabetes. These findings strongly suggest that inhibition of PDGFR is critical to reverse diabetes and highlight a crucial role of inflammation in the development of T1D. These conclusions were supported by the finding that the adaptive immune system was not significantly affected by imatinib treatment. Finally, and most significantly, imatinib treatment led to durable remission after discontinuation of therapy at 10 weeks in a majority of mice. Thus, long-term efficacy and tolerance is likely to depend on inhibiting a combination of tyrosine kinases supporting the use of selective kinase inhibitors as a new, potentially very attractive approach for the treatment of T1D.

Systemic cancer therapy: evolution over the last 60 years

The 1940s marked the beginning of an era of important discoveries that contributed to modern concepts underlying the current practice of cancer chemotherapy, such as the log kill hypothesis reported by Skipper, the Norton-Simon hypothesis, and the Goldie-Coldman hypothesis. The early success of nitrogen mustards and antifolates in the treatment of hematologic malignancies paved the way for drug discovery platforms, which resulted in the generation of more drugs that nonetheless predominantly are genotoxic. The turn of the new millennium marked a new phase in the evolution of cancer chemotherapy. Scientific progress in the preceding 60 years elucidated the important ideas behind tumor microenvironment and 'targeted' therapy that had their inception in the late 19th century. Breakthroughs in molecular biology have paved the way for the development of novel agents that modulate the dysregulated molecular pathways implicated in carcinogenesis. The key approaches and evidence pertinent to the clinical development of these novel agents are presented in this review.