Imatinib impairs CD8+ T lymphocytes specifically directed against the leukemia-associated antigen RHAMM/CD168 in vitro

Leukapheresis guidance and best practices for optimal chimeric antigen receptor T-cell manufacturing

Chimeric antigen receptor (CAR) T-cell therapy is an individualized immunotherapy that genetically reprograms a patient's T cells to target and eliminate cancer cells. Tisagenlecleucel is a US Food and Drug Administration-approved CD19-directed CAR T-cell therapy for patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia and r/r diffuse large B-cell lymphoma. Manufacturing CAR T cells is an intricate process that begins with leukapheresis to obtain T cells from the patient's peripheral blood. An optimal leukapheresis product is essential to the success of CAR T-cell therapy; therefore, understanding factors that may affect the quality or T-cell content is imperative. CAR T-cell therapy requires detailed organization throughout the entire multistep process, including appropriate training of a multidisciplinary team in leukapheresis collection, cell processing, timing and coordination with manufacturing and administration to achieve suitable patient care. Consideration of logistical parameters, including leukapheresis timing, location and patient availability, when clinically evaluating the patient and the trajectory of their disease progression must be reflected in the overall collection strategy. Challenges of obtaining optimal leukapheresis product for CAR T-cell manufacturing include vascular access for smaller patients, achieving sufficient T-cell yield, eliminating contaminating cell types in the leukapheresis product, determining appropriate washout periods for medication and managing adverse events at collection. In this review, the authors provide recommendations on navigating CAR T-cell therapy and leukapheresis based on experience and data from tisagenlecleucel manufacturing in clinical trials and the real-world setting.

Improving outcomes in chronic myeloid leukemia through harnessing the immunological landscape

The quest for treatment-free remission (TFR) and deep molecular response (DMR) in chronic myeloid leukemia (CML) has been profoundly impacted by tyrosine kinase inhibitors (TKIs). Immunologic surveillance of residual leukemic cells is hypothesized to be one of the critical factors in successful TFR, with self-renewing leukemic stem cells implicated in relapse. Immunological characterization in CML may help to develop novel immunotherapies that specifically target residual leukemic cells upon TKI discontinuation to improve TFR rates. This review focuses on immune dysfunction in newly diagnosed CML patients, and the role that TKIs and other therapies have in restoring immune surveillance. Immune dysfunction and immunosurveillance in CML points towards several emerging areas in the key goals of DMR and TFR, including: (1) Aspects of innate immune system, in particular natural killer cells and the newly emerging target plasmacytoid dendritic cells. (2) The adaptive immune system, with promise shown in regard to leukemia-associated antigen vaccine-induced CD8 cytotoxic T-cells (CTL) responses, increased CTL expansion, and immune checkpoint inhibitors. (3) Immune suppressive myeloid-derived suppressor cells and T regulatory cells that are reduced in DMR and TFR. (4) Immunomodulator mesenchymal stromal cells that critically contribute to leukomogenesis through immunosuppressive properties and TKI- resistance. Therapeutic strategies that leverage existing immunological approaches include donor lymphocyte infusions, that continue to be used, often in combination with TKIs, in patients relapsing following allogeneic stem cell transplant. Furthermore, previous standards-of-care, including interferon-α, hold promise in attaining TFR in the post-TKI era. A deeper understanding of the immunological landscape in CML is therefore vital for both the development of novel and the repurposing of older therapies to improve TFR outcomes.

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.

Immune responses to WT1 in patients with AML or MDS after chemotherapy and allogeneic stem cell transplantation

Wilms' tumor gene 1 (WT1) is overexpressed in leukemia and WT1-derived CD8(+) T-cell epitopes for immunotherapies targeting WT1 have been defined. Here, we analyzed expression of WT1 in 226 peripheral blood and bone marrow samples from patients with acute myeloid leukemia or myelodysplastic syndrome (AML/MDS) before and after allogeneic stem cell transplantation (SCT). Transcripts were assessed by quantitative polymerase chain reaction, and WT1-specific CD8+ cytotoxic T cells (CTL) were monitored by tetramer staining and enzyme-linked immunospot (ELISPOT) assays. Reduction of WT1 levels correlated with a longer survival (p < 0.01). Increment of WT1 transcripts eventually resulted in relapse and subsequent death of the patients. In patients with longer survival and continuous complete remission (cCR) after SCT, higher and enduring frequencies of WT1-specific CTL than in patients developing a relapse were detected. These cells were effector T cells secreting interferon gamma and granzyme B. In summary, WT1 is a suitable marker for the detection of minimal residual disease after SCT or chemotherapy. A rising WT1 signal correlated with a dismal prognosis of the patients. WT1-specific CD8(+) T cells might contribute to the maintenance of a cCR. Targeting WT-1 by peptide/protein vaccination as well as adoptive transfer of genetically modified T cells are future options in the individualized therapy for AML/MDS patients.

Donor lymphocyte infusion after allogeneic hematopoietic stem cell transplantation

Donor lymphocyte infusion, a rescue therapy after hematopoietic stem cell transplantation, has been increasingly adopted, as modalities of stem cell transplantation have widened. First described as donor lymphocyte transfusion or cell therapy, it consists of infusion of donor lymphocytes, collected in steady state or after growth factor enhancement. As in literature the most used name is donor lymphocyte infusion, we'll adopt it here. Its most striking efficacy is observed in patients with chronic myelogenous leukemia, who relapsed after allogeneic stem cells transplantation. However, graft-versus-host disease, its main complication, may still hamper its feasibility.

T-cell immune suppression in patients with hematologic malignancies: clinical implications

SUMMARY 

The reversion of immune suppression and restoration of T-cell function against leukemia remains a significant clinical challenge. However, the advent of improved antileukemia-specific T-cell induction and the generation of gene-modified T cells has extended cellular immunotherapy to hematological malignancies. Numerous immunotherapeutic protocols have been developed aiming to enhance antileukemia T-cell immune function, eliminate leukemic cells and prevent relapse. By contrast, abnormal expression of CTLA-4 and PD1/PD-L1 plays a critical role in effector T-cell responses and increases Treg suppressive activity in patients with tumors; therefore, blocking CTLA-4, PD1 and PD-L1 is a novel approach for immunotherapy.

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.

Proliferation inhibition and apoptosis induction of imatinib-resistant chronic myeloid leukemia cells via PPP2R5C down-regulation

Despite the success of imatinib and other tyrosine kinase inhibitors (TKIs), chronic myeloid leukemia (CML) remains largely incurable, and a number of CML patients die due to Abl mutation-related drug resistance and blast crisis. The aim of this study was to evaluate proliferation inhibition and apoptosis induction by down-regulating PPP2R5C gene expression in the imatinib-sensitive and imatinib-resistant CML cell lines K562, K562R (imatinib resistant without an Abl gene mutation), 32D-Bcr-Abl WT (imatinib-sensitive murine CML cell line with a wild type Abl gene) and 32D-Bcr-Abl T315I (imatinib resistant with a T315I Abl gene mutation) and primary cells from CML patients by RNA interference. PPP2R5C siRNAs numbered 799 and 991 were obtained by chemosynthesis. Non-silencing siRNA scrambled control (SC)-treated, mock-transfected, and untreated cells were used as controls. The PPP2R5C mRNA and protein expression levels in treated CML cells were analyzed by quantitative real-time PCR and Western blotting, and in vitro cell proliferation was assayed with the cell counting kit-8 method. The morphology and percentage of apoptosis were revealed by Hoechst 33258 staining and flow cytometry (FCM). The results demonstrated that both siRNAs had the best silencing results after nucleofection in all four cell lines and primary cells. A reduction in PPP2R5C mRNA and protein levels was observed in the treated cells. The proliferation rate of the PPP2R5C-siRNA-treated CML cell lines was significantly decreased at 72 h, and apoptosis was significantly increased. Significantly higher proliferation inhibition and apoptosis induction were found in K562R cells treated with PPP2R5C-siRNA799 than K562 cells. In conclusion, the suppression of PPP2R5C by RNA interference could inhibit proliferation and effectively induce apoptosis in CML cells that were either imatinib sensitive or resistant. Down-regulating PPP2R5C gene expression might be considered as a new therapeutic target strategy for CML, particularly for imatinib-resistant CML.

New insights into antigen specific immunotherapy for chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a stem cell disease in which BCR/ABL plays an important role as an oncoprotein and a molecular and immunogenic target. Despite the success of targeted therapy using tyrosine kinase inhibitors (TKIs), CML remains largely incurable, most likely due to the treatment resistance of leukemic stem cells. Several immunotherapies have been developed for CML in different stages and relapse after allogeneic stem cell transplantation. In the this review, several specific immunotherapeutic approaches for CML, including vaccination and adoptive cellular immunotherapy, are discussed along with results from clinical trials, and the value of such immunotherapies in the era of imatinib and leukemia-associated antigens (LAAs), which are capable of inducing specific T cell responses and are appropriate target structures for the immunological targeting of CML cells, are also summarized.

TCR-transgenic lymphocytes specific for HMMR/Rhamm limit tumor outgrowth in vivo

The hyaluronan-mediated motility receptor (HMMR/Rhamm) is overexpressed in numerous tumor types, including acute lymphoid leukemia and acute myeloid leukemia (AML). Several studies have reported the existence of T-cell responses directed against HMMR in AML patients that are linked to better clinical outcome. Therefore, we explored the use of HMMR-specific TCRs for transgenic expression in lymphocytes and their in vivo impact on HMMR(+) solid tumors and disseminated leukemia. We obtained TCRs via an in vitro priming approach in combination with CD137-mediated enrichment. Recipient lymphocytes expressing transgenic TCR revealed the specific tumor recognition pattern seen with the original T cells. Adoptive transfer experiments using a humanized xenograft mouse model resulted in significantly retarded solid tumor outgrowth, which was enhanced using IL-15-conditioned, TCR-transgenic effector memory cells. These cells also showed an increased potency to retard the outgrowth of disseminated AML, and this was further improved using CD8-enriched effector memory cells. To define a safe clinical setting for HMMR-TCR gene therapy, we analyzed transgenic T-cell recognition of hematopoietic stem cells (HSCs) and found on-target killing of HLA-A2(+) HSCs. Our findings clearly limit the use of HMMR-TCR therapy to MHC- mismatched HSC transplantation, in which HLA-A2 differences can be used to restrict recognition to patient HSCs and leukemia.

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.

Donor lymphocyte infusion following allogeneic hematopoietic stem cell transplantation

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (SCT) is the treatment of choice for many malignant hematological disorders. Following recent improvements in non-relapse-related mortality rates, relapse has become the commonest cause of treatment failure. Infusion of donor lymphocytes can potentially enhance immune-mediated antitumor activity and offers a salvage option for some patients. This paper reviews the current literature on the efficacy of this therapeutic strategy.

AREAS COVERED

The biology of adoptive cellular therapy with allogeneic immune cells to treat relapse across a spectrum of diseases in both the full intensity and reduced intensity hematopoietic SCT settings is explored. The review discusses the current limitations of the approach and reviews several new experimental strategies which aim to segregate the desired graft-versus-tumor effect from the deleterious effects of more widespread graft-versus-host reactivity.

EXPERT OPINION

Durable responses to DLI have been noted in chronic myeloid leukemia and responses have also been described in acute leukemia, multiple myeloma and chronic lymphoproliferative disorders. The new challenge in transplantation is to optimize DLI therapy in order to further improve patient outcomes.

Effects of nilotinib on regulatory T cells: the dose matters

BACKGROUND

Nilotinib is a tyrosine kinase inhibitor with high target specificity. Here, we characterized the effects of nilotinib for the first time on CD4+CD25+ regulatory T cells (Tregs) which regulate anti-tumor/leukemia immune responses.

DESIGN AND METHODS

Carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2-deoxy -uridine (BrdU) were used to assess the proliferation and cell cycle distribution of Tregs. The expression of the transcription factor forkhead box P3 (FoxP3) and the glucocorticoid-induced tumor necrosis factor receptor (GITR) were measured by flow cytometry. Western blotting analysis was used to detect the effects of nilotinib on the signal transduction cascade of T-cell receptor (TCR) in Tregs.

RESULTS

Nilotinib inhibited the proliferation and suppressive capacity of Tregs in a dose-dependent manner. However, the production of cytokines secreted by Tregs and CD4+CD25- T cells was only inhibited at high concentrations of nilotinib exceeding the mean therapeutic serum concentrations of the drug in patients. Only high doses of nilotinib arrested both Tregs and CD4+CD25- T cells in the G0/G1 phase and down-regulated the expression of FoxP3 and GITR. In western blotting analysis, nilotinib did not show significant inhibitory effects on TCR signaling events in Tregs and CD4+CD25- T cells.

CONCLUSIONS

These findings indicate that nilotinib does not hamper the function of Tregs at clinical relevant doses, while long-term administration of nilotinib still needs to be investigated.

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.

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.

Dasatinib inhibits the proliferation and function of CD4+CD25+ regulatory T cells

CD4+CD25+ regulatory T cells (Tregs) can influence various immune responses. Little is known about the effects of the Abl/Src kinase inhibitor dasatinib on Tregs which regulate anti-tumor/leukaemia immune responses. The present study demonstrated that dasatinib inhibited proliferation of Tregs and CD4+CD25- T cells in a dose-dependent manner, which was associated with the decreased production of corresponding cytokines. Treatment of Tregs with dasatinib inhibited the suppressive capacity of Tregs. The mechanisms of this inhibition included arrest of cells in the G0/G1 phase of cell cycle, down-regulation of the transcription factor forkhead box P3, glucocorticoid-induced tumour necrosis factor receptor and the cytotoxic T lymphocyte associated protein 4 as well as inhibition of signaling events through Src and nuclear factor kappaB. Dasatinib showed an inhibitory effect on the proliferation and function of both Tregs and CD4+CD25- T cells at therapeutically relevant concentrations of the drug. Clinical administration of dasatinib might influence not only the graft-versus-leukaemia effect but also the graft-versus-host-disease in patients receiving dasatinib after allogeneic stem cell transplantation and/or donor lymphocytes infusion as the function of both Tregs and effector T cells are hampered in a similar way by dasatinib.

Profound inhibition of antigen-specific T-cell effector functions by dasatinib

PURPOSE

The dual BCR-ABL/SRC kinase inhibitor dasatinib entered the clinic for the treatment of chronic myeloid leukemia and Ph+ acute lymphoblastic leukemia. Because SRC kinases are known to play an important role in physiologic T-cell activation, we analyzed the immunobiological effects of dasatinib on T-cell function. The effect of dasatinib on multiple T-cell effector functions was examined at clinically relevant doses (1-100 nmol/L); the promiscuous tyrosine kinase inhibitor staurosporine was used as a comparator.

EXPERIMENTAL DESIGN

Purified human CD3+ cells and virus-specific CD8+ T cells from healthy blood donors were studied directly ex vivo; antigen-specific effects were confirmed in defined T-cell clones. Functional outcomes included cytokine production (interleukin-2, IFN gamma, and tumor necrosis factor alpha), degranulation (CD107a/b mobilization), activation (CD69 up-regulation), proliferation (carboxyfluorescein diacetate succinimidyl ester dilution), apoptosis/necrosis induction, and signal transduction.

RESULTS

Both dasatinib and staurosporine inhibited T-cell activation, proliferation, cytokine production, and degranulation in a dose-dependent manner. Mechanistically, this was mediated by the blockade of early signal transduction events and was not due to loss of T-cell viability. Overall, CD4+ T cells seemed to be more sensitive to these effects than CD8+ T cells, and naïve T cells more sensitive than memory T-cell subsets. The inhibitory effects of dasatinib were so profound that all T-cell effector functions were shut down at therapeutically relevant concentrations.

CONCLUSION

These findings indicate that caution is warranted with use of this drug in the clinical setting and provide a rationale to explore the potential of dasatinib as an immunosuppressant in the fields of transplantation and T-cell-driven autoimmune diseases.

Nilotinib hampers the proliferation and function of CD8+ T lymphocytes through inhibition of T cell receptor signalling

The novel selective BCR-ABL Breakpoint cluster region – Abelson murine leukemia viral oncogene homolog 1 (BCR-AML) inhibitor nilotinib (AMN107) is a tyrosine kinase inhibitor that is more potent against leukaemia cells in vitro than imatinib. As nilotinib might be used in the context of allogeneic stem cell transplantation where CD8⁺ T lymphocytes play a pivotal role in the graft-versus-leukaemia (GVL) effect, we investigated effects of nilotinib on this lymphocyte subpopulation. Nilotinib inhibits phytohemagglutinin (PHA)-induced proliferation of CD8⁺T lymphocytes in vitro at therapeutically relevant concentrations (0.5–4 μM). The inhibition of CD8⁺ T lymphocytes specific for leukaemia or viral antigens through nilotinib was associated with a reduced expansion of antigen peptide specific CD8⁺ T lymphocytes and with a decreased release of interferon—γ and granzyme B by these cells as analysed by flow cytometry and enzyme-linked immunospot (ELISPOT) assays. The inhibitory effect caused by nilotinib was two times stronger than by imatinib. These effects were mediated through the inhibition of the phosphorylation of ZAP-70, Lck and ERK 1/2 and the NF-κβ signalling transduction pathway. Taken together, we observed a strong suppressive impact of nilotinib on the CD8⁺ T lymphocyte function which should be considered carefully in the framework of allogeneic stem cell transplantation or other T cell based immunotherapies.