Cellular immune therapy for chronic lymphocytic leukemia

Introduction of Z-GP scaffold into procarbazine reduces spermatoxicity and myelosuppression

Incorporation of carbobenzoxy-glycylprolyl (Z-GP) to either α or β position of the hydrazine moiety in procarbazine (Pcb) has been carried on in 5-steps process. The overall yield was 32.7%. The new entity Z-GP-Pcb was confirmed targeting to fibroblast activation protein-α (FAPα). Z-GP-Pcb may be hydrolyzed by either isolated rhFAPα or tumor homogenate. It was shown far less cytotoxicity against NCI-H460 cell line than Pcb. Z-GP-Pcb was displayed the potency to reduce spermatoxcity in H22-bearing mice. The mechanism may be ascribed to the blockade of dehydrogenation by α-glycerolphosphate dehydrogenase. This candidate was further proved equal antitumor activity to Pcb. However, the introduction of Z-GP scaffold decreased myelosuppression. All the evidences support that Z-GP-Pcb is a better antitumor agent than Pcb.

Mono- and dual-targeting triplebodies activate natural killer cells and have anti-tumor activity in vitro and in vivo against chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia that affects B lymphocytes in adults. Natural killer (NK) cells in CLL patients are intrinsically potent but display poor in situ effector functions. NKG2D is an activating receptor found on NK and CD8⁺ T cells and plays a role in immunosurveillance of CLL. In this study, we developed mono- and dual-targeting triplebodies utilizing a natural ligand for human NKG2D receptor (ULBP2) to retarget NK cells against tumor cells. Triplebodies in both formats showed better ability to induce NK-cell-dependent killing of target cells compared to bispecific counterparts. A mono-targeting triplebody ULBP2-aCD19-aCD19 successfully triggered NK cell effector functions against CLL cell line MEC1 and primary tumor cells in allogenic and autologous settings. Additionally, a dual-targeting triplebody ULBP2-aCD19-aCD33 specific for two distinct tumor-associated antigens was developed to target antigen loss variants, such as mixed lineage leukemia (MLL). Of note, this triplebody exhibited cytotoxic activity against CD19/CD33 double positive cells and retained its binding features even in the absence of one of the tumor antigens. Further, ULBP2-aCD19-aCD19 showed significant in vivo activity in immune-deficient (NSG) mouse model transplanted with CLL cell line as target cells and human immune cells as an effector population providing a proof-of-principle for this therapeutic concept.

(89)Zr-Oxine Complex PET Cell Imaging in Monitoring Cell-based Therapies

PURPOSE

To develop a clinically translatable method of cell labeling with zirconium 89 ((89)Zr) and oxine to track cells with positron emission tomography (PET) in mouse models of cell-based therapy.

MATERIALS AND METHODS

This study was approved by the institutional animal care committee. (89)Zr-oxine complex was synthesized in an aqueous solution. Cell labeling conditions were optimized by using EL4 mouse lymphoma cells, and labeling efficiency was examined by using dendritic cells (DCs) (n = 4), naïve (n = 3) and activated (n = 3) cytotoxic T cells (CTLs), and natural killer (NK) (n = 4), bone marrow (n = 4), and EL4 (n = 4) cells. The effect of (89)Zr labeling on cell survival, proliferation, and function were evaluated by using DCs (n = 3) and CTLs (n = 3). Labeled DCs (444-555 kBq/[5 × 10(6)] cells, n = 5) and CTLs (185 kBq/[5 × 10(6)] cells, n = 3) transferred to mice were tracked with microPET/CT. In a melanoma immunotherapy model, tumor targeting and cytotoxic function of labeled CTLs were evaluated with imaging (248.5 kBq/[7.7 × 10(6)] cells, n = 4) and by measuring the tumor size (n = 6). Two-way analysis of variance was used to compare labeling conditions, the Wilcoxon test was used to assess cell survival and proliferation, and Holm-Sidak multiple tests were used to assess tumor growth and perform biodistribution analyses.

RESULTS

(89)Zr-oxine complex was synthesized at a mean yield of 97.3% ± 2.8 (standard deviation). It readily labeled cells at room temperature or 4°C in phosphate-buffered saline (labeling efficiency range, 13.0%-43.9%) and was stably retained (83.5% ± 1.8 retention on day 5 in DCs). Labeling did not affect the viability of DCs and CTLs when compared with nonlabeled control mice (P > .05), nor did it affect functionality. (89)Zr-oxine complex enabled extended cell tracking for 7 days. Labeled tumor-specific CTLs accumulated in the tumor (4.6% on day 7) and induced tumor regression (P < .05 on day 7).

CONCLUSION

We have developed a (89)Zr-oxine complex cell tracking technique for use with PET that is applicable to a broad range of cell types and could be a valuable tool with which to evaluate various cell-based therapies.

Paradigm shifts in the management of poor-risk chronic lymphocytic leukemia

With the growing complexity of treatment options for chronic lymphocytic leukemia (CLL) and variables that influence the underlying biology of this disease, providing allogeneic stem cell transplant (alloSCT) to appropriate candidates poses a challenge for transplant physicians. Novel small molecule inhibitors hold unprecedented promise for poor-risk subgroups, which will likely alter decision-making and referral patterns for transplant. In this review, we analyze what is known and may still remain true about indications for transplant based on outcomes reported in the literature recently and over the last decade.

B cell receptor pathway in chronic lymphocytic leukemia: specific role of CC-292

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia. The current treatment paradigm involves the use of chemoimmunotherapy, when patients develop an indication for therapy. With this strategy, a majority of patients will obtain a remission, though cure remains elusive. While treatable, the majority of CLL patients will die of complications of their disease. Recent advances in the understanding of the importance of the B cell receptor (BCR) pathway in CLL have led to the development of a number of agents targeting this pathway. In this review, we discuss recent developments in the targeting of the BCR pathway, with a focus on CC-292. CC-292 covalently binds to Bruton's tyrosine kinase, a key mediator of BCR signaling, and has demonstrated preclinical and clinical activity in CLL, with acceptable tolerability. Based on the success of CC-292 and other inhibitors of the BCR pathway, these agents are being investigated in combination with standard therapy, with the hope that they will increase the depth and length of response, without significant toxicity.

CMV-specific CD8+ T-cell function is not impaired in chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), CD8(+) T cells exhibit features of exhaustion and impaired functionality. Yet, reactivations of latent viruses such as cytomegalovirus (CMV) are uncommon in untreated CLL, suggesting that antiviral responses are uncompromised. We analyzed phenotypical and functional characteristics of CMV-specific CD8(+) T cells in CLL patients in comparison with age-matched healthy controls (HCs). Despite increased expression of the inhibitory receptors PD1, CD160, and CD244 on total CD8(+) T cells in CLL, expression levels of these markers were decreased on CMV-tetramer(+)CD8(+) T cells. Second, cytokine production upon stimulation with both phorbol 12-myristate 13-acetate/ionomycin and CMV-peptide-loaded antigen-presenting cells was intact in CMV-tetramer(+)CD8(+) T cells. Third, CMV-tetramer(+)CD8(+) T cells of CLL patients and HCs were equally effective in killing CMV-peptide-loaded target cells. Finally, quantitative imaging flow cytometry revealed that the proportion of CD8(+) T cells forming immunologic synapses with CMV-peptide-loaded B cells was intact. In conclusion, despite evidence for global T-cell dysfunction in CLL, we show here that CLL-derived CMV-specific CD8(+) T cells display lower expression of exhaustion markers and are functionally intact. These data indicate that the changes in the T-cell compartment in CLL may be more heterogeneous than presently assumed.

Distinctive patterns of naïve/memory subset distribution and cytokine expression in CD4 T lymphocytes in ZAP-70 B-chronic lymphocytic patients

BACKGROUND

ZAP-70 upregulation in B chronic lymphocytic leukemia (B-CLL) cells is a recognized marker of poor prognosis in these patients; the biological basis of this differential clinical outcome nonetheless remains unknown. ZAP-70 overexpression is considered a surrogate marker of a B-CLL cell subset. To test whether the differential biological characteristics of these patients also include the T helper population, we studied naïve, non-terminated memory (NTEM), terminated memory (TEM) and central memory (CM) cells, and cytokine expression by CD4 T lymphocytes from ZAP-70(+) and ZAP-70(-) B-CLL patients.

METHODS

Expression of CD3, CD8, CD45RA, CD27, and CD28 antigens and intracytoplasmic cytokine production (IFNγ, IL-2, IL-4, IL-10, and TNFα) were assessed simultaneously by nine-color flow-cytometry in peripheral blood lymphocytes from B-CLL patients. B cell ZAP-70 expression in B-CLL cells was also analyzed by flow cytometry.

RESULTS

Compared to ZAP-70(-) B-CLL patients, ZAP-70(+) B-CLL patients showed 1) significant reduction in the naïve T helper subset and expansion of NTEM and TEM subsets, 2) a decrease in the percentage of activated CD4 T lymphocytes expressing IFNγ, TNFα, and IL-2, and 3) an increase in the percentage of CD4 T lymphocytes expressing IL-4 or IL-10.

CONCLUSIONS

In conclusion, in early stage B-CLL patients, ZAP-70 upregulation is associated with distinct patterns of activation/differentiation stage subset distribution and of cytokine expression in CD4 T lymphocytes.

A combination of cytokines rescues highly purified leukemic CLL B-cells from spontaneous apoptosis in vitro

B-chronic lymphocytic leukemia (B-CLL), the most common human leukemia, is characterized by predominantly non-dividing malignant mature CD5+ B lymphocytes with an apoptosis defect. Various microenvironmental stimuli confer a growth advantage on these leukemic cells and extend their survival in vivo. Nevertheless, when cultured in vitro, CLL B-cells rapidly die from apoptosis. Certain cytokines may extend the survival capacity of CLL B-cells in vitro and individual anti-apoptotic effects of several cytokines have been reported. The potential cumulative effect of such cytokines has not been studied. We therefore investigated the effects on CLL B-cells survival in vitro of humoral factors, polyclonal lymphocyte activators and a combination of cytokines known for their anti-apoptotic effects. Purified CLL B-cells were cultured in the presence or absence of various soluble molecules and the leukemic cell response was assessed in terms of viability. Apoptotic cell death was detected by flow cytometry using annexinV and 7-amino-actinomycin. The survival of CLL B-cells in vitro was highly variable. When tested separately, cytokines (IL-2, -6, -10, -12, -15, -21, BAFF and APRIL) improved CLL B cell survival moderately; in combination, they significantly enhanced survival of these cells, even up to 7 days of culture. We also report that humoral factors from autologous serum are important for survival of these malignant cells. Our findings support the concept that the CLL microenvironment is critical and suggest that soluble factors may contribute directly to the prolonged survival of CLL B-cells. Therefore, the combination of cytokines we describe as providing strong resistance to apoptosis in vitro might be used to improve the treatment of CLL.

CpG oligodeoxynucleotide induces apoptosis and cell cycle arrest in A20 lymphoma cells via TLR9-mediated pathways

Recent studies have suggested that the anti-cancer activity of CpG-oligodeoxynucleotides (CpG-ODNs) is owing to their immunomodulatory effects in tumor-bearing host. The purpose of this study is to investigate the directly cytotoxic activity of KSK-CpG, a novel CpG-ODN with an alternative CpG motif, against A20 and EL4 lymphoma cells in comparison with previously used murine CpG motif (1826-CpG). To evaluate the potential cytotoxic effects of KSK-CpG on lymphoma cells, cell viability assay, confocal microscopy, flow cytometry, DNA fragmentation, Western blotting, and reverse transcription-polymerase chain reaction (RT-PCR) analysis were used. We found that KSK-CpG induced direct cytotoxicity in A20 lymphoma cells, but not in EL4 lymphoma cells, at least in part via TLR9-mediated pathways. Apoptotic cell death was demonstrated to play an important role in CpG-ODNs-induced cytotoxicity. In addition, both mitochondrial membrane potential decrease and G1-phase arrest were involved in KSK-CpG-induced apoptosis in A20 cells. The activities of apoptotic molecules such as caspase-3, PARP, and Bax were increased, but the activation of p27 Kip1 and ERK were decreased in KSK-CpG-treated A20 cells. Furthermore, autocrine IFN-γ partially contributed to apoptotic cell death in KSK-CpG-treated A20 cells. Collectively, our findings suggest that KSK-CpG induces apoptotic cell death in A20 lymphoma cells at least in part by inducing G1-phase arrest and autocrine IFN-γ via increasing TLR9 expression, without the need for immune system of tumor-bearing host. This new understanding supports the development of TLR9-targeted therapy with CpG-ODN as a direct therapeutic agent for treating B lymphoma.

Generation of functional CLL-specific cord blood CTL using CD40-ligated CLL APC

Though remissions have been observed following allo-HSCT for the treatment of CLL, many CLL patients are ineligible for transplant due to the lack of HLA-compatible donors. The use of umbilical cord blood (UCB) permits transplantation of many patients who lack HLA-compatible donors due to reduced requirements for stringent HLA matching between graft and recipient; however, disease relapse remains a concern with this modality. The generation of CLL-specific CTL from UCB T-cells, primed and expanded against the leukemic clone, might enhance the GVL effect and improve outcomes with UCB transplantation. Here we report the generation of functional, CLL-specific CTL using CD40-ligated CLL cells to prime partially-HLA matched UCB T-cells. Functionality and specificity were demonstrated by immune synapse assay, IFN-γ ELISpot, multi-parametric intracellular cytokine flow cytometry, and ⁵¹Cr release assay. The use of patient-specific, non-CLL controls demonstrated the generation of both alloantigen and CLL-specific responses. Subsequently, we developed a clinically-applicable procedure permitting separation of alloreactive CTL from leukemia-specific CTL. Leukemia-specific CTL were able to mediate in vivo killing of CLL in humanized mice without concurrent or subsequent development of xenoGVHD. Our results demonstrate that generation of CLL-specific effectors from UCB is feasible and practical, and the results support further exploration of this strategy as a treatment modality for CLL.

Functional invariant natural killer T-cell and CD1d axis in chronic lymphocytic leukemia: implications for immunotherapy

Invariant natural killer T cells recognize glycolipid antigens such as α-galactosylceramide presented by CD1d. In preclinical models of B-cell malignancies, α-galactosylceramide is an adjuvant to tumor vaccination, enhancing tumor-specific T-cell responses and prolonging survival. However, numerical and functional invariant natural killer T-cell defects exist in patients with some cancers. Our aim was to assess this axis in patients with chronic lymphocytic leukemia. The numbers of circulating invariant natural killer T cells and the expression of CD1d on antigen-presenting cells were evaluated in patients with chronic lymphocytic leukemia and age-matched controls. Cytokine profile and in vitro proliferative capacity were determined. Patient- and control-derived invariant natural killer T-cell lines were generated and characterized, and allogeneic and autologous responses to α-galactosylce-ramide-treated leukemia cells were assessed. Absolute numbers and phenotype of invariant natural killer T cells were normal in patients with untreated chronic lymphocytic leukemia, and cytokine profile and proliferative capacity were intact. Chemotherapy-treated patients had reduced numbers of invariant natural killer T cells and myeloid dendritic cells, but α-galactosylceramide-induced proliferation was preserved. Invariant natural killer T-cell lines from patients lysed CD1d-expressing targets. Irradiated α-galactosylceramide-treated leukemic cells elicited allogeneic and autologous invariant natural killer T-cell proliferation, and α-galactosylceramide treatment led to increased proliferation of conventional T cells in response to tumor. In conclusion, the invariant natural killer T-cell and CD1d axis is fundamentally intact in patients with early-stage chronic lymphocytic leukemia and, despite reduced circulating numbers, function is retained in fludarabine-treated patients. Immunotherapies exploiting the adjuvant effect of α-galactosylceramide may be feasible.

CD40 stimulation sensitizes CLL cells to lysosomal cell death induction by type II anti-CD20 mAb GA101

Sensitivity of chronic lymphocytic leukemia (CLL) cells to anti-CD20 mAbs is low and, therefore, the efficacy of monotherapy with current anti-CD20 mAbs is limited. At present, it is not known whether sensitivity of CLL cells to CD20 mAbs is modulated by microenvironmental stimuli. We have shown previously that in vitro CD40 stimulation of peripheral blood-derived CLL cells results in resistance to cytotoxic drugs. In the present study, we show that, in contrast, CD40 stimulation sensitizes CLL cells to the recently described novel type II anti-CD20 mAb GA101. Cell death occurred without cross-linking of GA101 and involved a lysosome-dependent mechanism. Combining GA101 with various cytotoxic drugs resulted in additive cell death, not only in CD40-stimulated CLL cells, but also in p53-dysfunctional CLL cells. Our findings indicate that GA101 has efficacy against chemoresistant CLL, and provide a rationale for combining cytotoxic drugs with anti-CD20 mAbs.

Study of fibromodulin gene expression in B-cell chronic lymphocytic leukemia

BACKGROUND AND OBJECTIVES

It has become evident that fibromodulin and other members of the proteoglycan family are not only involved in collagen fibrillogenesis and cell adhesion but they also contribute to modulation of cytokine activity, suppression of tumor growth, and prevention of apoptosis. Fibromodulin has been characterized as one of the tumor associated antigens (TAA) in B cell chronic lymphocytic leukemia (B-CLL) with the potential to elicit specific antitumor response and it is considered as good candidate for immunotherapy.

AIM OF WORK

to study the expression of fibromodulin at the gene level of B-cell chronic lymphocytic leukemia patients, in comparison to normal controls and to asses its role in the pathophysiology of CLL.

PATIENTS AND METHODS

Fibromodulin gene expression was tested by one step reverse transcription-polymerase chain reaction (RT-PCR) in peripheral blood mononuclear cells of 30 patients with B-CLL as well as in 20 age and sex matched healthy volunteers.

RESULTS

In this study, fibromodulin gene was expressed in 46.7% of patients with B-CLL which was significantly different from the control age and sex matched healthy volunteers in which none of them showed peripheral blood mononuclear cells positivity for fibromodulin gene expression (0%) (p-value =0.006). We also found significant associations between higher fibomodulin gene expression and some risk factors in the studied CLL cases such as hepatomegaly, lower haemoglobin level, lower RBCs count, lower platelet count and borderline significant associations with other risk factors as lymphadenopathy and splenomegaly.

CONCLUSION

Our results suggest that fibromodulin can be used as a target for therapeutic intervention and it may play a role in the pathophysiology of CLL.

A novel tumor antigen derived from enhanced degradation of bax protein in human cancers

Cancer cells frequently exhibit defects in apoptosis, which contribute to increased survival and chemotherapeutic resistance. For example, genetic mutations or abnormal proteasomal degradation can reduce expression of Bax which limits apoptosis. In cancers where abnormal proteasomal degradation of Bax occurs, we hypothesized that Bax peptides that bind to human leukocyte antigen (HLA) class I molecules would be generated for presentation to CD8(+) T cells. To test this hypothesis, we generated T cells against pooled Bax peptides, using the blood of healthy human donors. Although T-cell responses were of low frequency (0.15%), a CD8(+) T-cell clone (KSIVB17) was isolated that optimally recognized Bax(136-144) peptide (IMGWTLDFL) presented by HLA-A*0201. KSIVB17 was able to recognize and kill a variety of HLA-matched cancer cells including primary tumor cells from chronic lymphocytic leukemia (CLL). No reactivity was seen against HLA-matched, nontransformed cells such as PHA blasts and skin fibroblasts. Furthermore, KSIVB17 reactivity corresponded with the proteasomal degradation patterns of Bax protein observed in cancer cells. Taken together, our findings suggest a new concept for tumor antigens based on regulatory proteins that are ubiquitously expressed in normal cells, but that have abnormally enhanced degradation in cancer cells. Bax degradation products offer candidate immune antigens in cancers such as CLL in which increased Bax degradation correlates with poor clinical prognosis.

The microenvironment differentially impairs passive and active immunotherapy in chronic lymphocytic leukaemia - CXCR4 antagonists as potential adjuvants for monoclonal antibodies

Direct contact with stromal cells protects chronic lymphocytic leukaemia (CLL) B cells from chemotherapy-induced apoptosis in vitro. Blockade of CXCR4 signalling antagonizes stroma-mediated interactions and restores CLL chemosensitivity. In vivo, administration of CXCR4 antagonists effectively mobilizes haematopoietic progenitor cells. Therefore, combinations of CXCR4 blockade and cytoreductive treatment with selective activity on CLL cells may avoid potential haematotoxicity. Hence, we tested CXCR4 antagonists in the context of passive and active immunotherapeutic approaches. We evaluated how efficiently rituximab, alemtuzumab and cytotoxic T cells killed CLL cells cocultured with stromal cells in the presence and absence of a CXCR4 antagonist. Stromal cell contact attenuated rituximab- and alemtuzumab-induced complement-dependent cytotoxicity of CLL cells. Addition of CXCR4 antagonists abrogated the protective effect of stroma. In contrast, stromal cells did not impair antibody-dependent cell-mediated cytotoxicity and cytotoxicity induced by activated T cells. Destruction of microtubules in CLL target cells restored the protective effect of stroma coculture for CLL cells during Natural Killer cell attack by preventing mitochondrial relocalization towards the immunological synapse. Our data identify the combination of CXCR4 antagonists with passive - but not active - immunotherapy as a promising potential treatment concept in CLL.

Current and emerging treatments for chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia in Europe and North America. The disease is characterized by proliferation and accumulation of small CD5+ B cells in blood, lymph nodes, spleen, liver and bone marrow. The natural clinical course of CLL is highly variable, and chemotherapy is usually not indicated in early and stable disease. However, patients with progressive and more advanced CLL require treatment. For many years, chlorambucil with or without corticosteroids was used in previously untreated patients with CLL. More recently, purine nucleoside analogues (PNAs) [fludarabine, cladribine and pentostatin] have been included in treatment approaches for this disease, and chlorambucil is no longer the leading standard everywhere. Currently, this drug is rather recommended for the treatment of older, unfit patients with co-morbidities, especially in European countries. Significantly higher overall response (OR) and complete response (CR) rates in patients treated initially with PNAs than in those treated with chlorambucil or cyclophosphamide-based combination regimens have been confirmed in randomized, prospective, multicentre trials. Moreover, PNAs administered in combination with cyclophosphamide produce higher response rates, including CR and molecular CR, compared with PNA as monotherapy. Recent reports suggest that the administration of monoclonal antibodies (mAbs) can significantly improve the course of CLL. At present, two mAbs have the most important clinical value in patients with CLL. The first is rituximab, a human mouse antibody that targets CD20 antigens, and the second is alemtuzumab, a humanized form of a rat antibody active against CD52. Several recent reports suggest that in patients with CLL, rituximab combined with a PNA can increase the OR and CR rates compared with PNA or rituximab alone, with acceptable toxicity. In randomized trials, the combination of rituximab with fludarabine and cyclophosphamide (FC-R regimen) demonstrated higher rates of OR, CR and progression-free survival in patients with previously untreated and relapsed or refractory CLL than fludarabine plus cyclophosphamide (FC regimen). Several reports have confirmed significant activity with alemtuzumab in relapsed or refractory CLL, as well as in previously untreated patients. Recently, several new agents have been investigated and have shown promise in treating patients with CLL. These treatments include new mAbs, agents targeting the antiapoptotic bcl-2 family of proteins and receptors involved in mediating survival signals from the microenvironment, antisense oligonucleotides and other agents. The most promising are new mAbs directed against the CD20 molecule, lumiliximab and anti-CD40 mAbs. Oblimersen, alvocidib (flavopiridol) and lenalidomide are also being evaluated both in preclinical studies and in early clinical trials. In recent years, a significant improvement in haematopoietic stem cell transplantation (HSCT) procedures in patients with high-risk CLL has been observed. However, the exact role of HSCT, autologous or allogeneic, in the standard management of CLL patients is still undefined.

Toll-like receptor 9 signaling by CpG-B oligodeoxynucleotides induces an apoptotic pathway in human chronic lymphocytic leukemia B cells

Chronic lymphocytic leukemia (CLL) is the most prevalent human leukemia and is characterized by the progressive accumulation of long-lived malignant B cells. Here we show that human B-CLL cells selectively express high levels of Toll-like receptor 9 (TLR9) mRNA and proteins. Treating B-CLL cells with TLR9 agonists, type B CpG oligodeoxynucleotides (CpG-B ODNs), induces significant morphologic and phenotypic activation, altered cytokine production, reversal of signal transducer, and activator of transcription 1 (STAT1) phosphorylation state, followed by profound apoptosis of B-CLL cells that is CpG-B ODN treatment time- and dose-dependent. TLR9-CpG ODN ligation-induced apoptosis of B-CLL cells is confirmed by viable cell counts, annexin V/propidium iodide and tetramethyl-rhodamine ethylester staining, Western blots of the activation, and cleaved caspases and poly (ADP-ribose) polymerase. Triggering TLR9 by CpG-B ODN leads to nuclear factor-kappaB-dependent production of autocrine interleukin-10, which activates JAK/STAT pathway-dependent tyrosine phosphorylation of STAT1 proteins and thereby provokes an apoptosis pathway in B-CLL cells. Treating B-CLL cells in vitro or in vivo with CpG-B ODN reduces the number of leukemia cells that engraft in NOD-scid mice. These findings provide new understanding of CpG ODN-mediated antitumor effects and support for the development of TLR9-targeted therapy for human CLL.

Construction and preclinical evaluation of an anti-CD19 chimeric antigen receptor

T cells can be engineered to express the genes of chimeric antigen receptors (CARs) that recognize tumor-associated antigens. We constructed and compared 2 CARs that contained a single chain variable region moiety that recognized CD19. One CAR contained the signaling moiety of the 4-1BB molecule and the other did not. We selected the CAR that did not contain the 4-1BB moiety for further preclinical development. We demonstrated that gammaretroviruses encoding this receptor could transduce human T cells. Anti-CD19-CAR-transduced CD8+ and CD4+ T cells produced interferon-gamma and interleukin-2 specifically in response to CD19+ target cells. The transduced T cells specifically killed primary chronic lymphocytic leukemia (CLL) cells. We transduced T cells from CLL patients that had been previously treated with chemotherapy. We induced these T cells to proliferate sufficiently to provide enough cells for clinical adoptive T cell transfer with a protocol consisting of an initial stimulation with an anti-CD3 monoclonal antibody (OKT3) before transduction followed by a second OKT3 stimulation 7 days after transduction. This protocol was successfully adapted for use in CLL patients with high peripheral blood leukemia cell counts by depleting CD19+ cells before the initial OKT3 stimulation. In preparation for a clinical trial that will enroll patients with advanced B cell malignancies, we generated a producer cell clone that produces retroviruses encoding the anti-CD19 CAR, and we produced sufficient retroviral supernatant for the proposed clinical trial under good manufacturing practice conditions.

E(mu)-TCL1 mice represent a model for immunotherapeutic reversal of chronic lymphocytic leukemia-induced T-cell dysfunction

Preclinical animal models have largely ignored the immune-suppressive mechanisms that are important in human cancers. The identification and use of such models should allow better predictions of successful human responses to immunotherapy. As a model for changes induced in nonmalignant cells by cancer, we examined T-cell function in the chronic lymphocytic leukemia (CLL) Emu-TCL1 transgenic mouse model. With development of leukemia, Emu-TCL1 transgenic mice developed functional T-cell defects and alteration of gene and protein expression closely resembling changes seen in CLL human patients. Furthermore, infusion of CLL cells into young Emu-TCL1 mice induced defects comparable to those seen in mice with developed leukemia, demonstrating a causal relationship between leukemia and the T-cell defects. Altered pathways involved genes regulating actin remodeling, and T cells exhibited dysfunctional immunological synapse formation and T-cell signaling, which was reversed by the immunomodulatory drug lenalidomide. These results further demonstrate the utility of this animal model of CLL and define a versatile model to investigate both the molecular mechanisms of cancer-induced immune suppression and immunotherapeutic repair strategies.

Adoptive T-cell immunotherapy of chronic lymphocytic leukaemia

Immunotherapy for B-cell chronic lymphocytic leukaemia (B-CLL) and other haematological malignancies may consist of passive antibody, active immunization or adoptive T-cell transfer. This chapter will focus on T-lymphocyte immunotherapy; an approach supported by earlier observations that the beneficial effects of allogeneic stem cell transplantation depend, in part, on the graft-versus-leukaemia effects mediated by these cells. One promising strategy consists of the genetic manipulation of effector T lymphocytes to express tumour-specific T-cell receptors or chimeric antigen receptors directed against surface antigens on the B-CLL cells. This methodology is now being integrated with the concept that tumour recurrence may be due to the persistence of a reservoir of more primitive and chemoresistant tumour cells, dubbed 'cancer stem cells', with self-renewal capacity. Identification and characterization of these cancer stem cells in B-CLL is crucial for the development of new anti-tumour agents, and for the identification of target antigens for cellular immunotherapy. This chapter will describe how immunotherapy may be directed to a more primitive side population of B-CLL cells.

Treatment of B-cell chronic lymphocytic leukemia with nonchemotherapeutic agents: experience with single-agent and combination therapy

Recent advances in purine analog-based combination chemotherapy and chemoimmunotherapy have significantly improved response rates and progression-free survival in patients with B-cell chronic lymphocytic leukemia (CLL). However, there are clinical scenarios in which purine analog-based treatment may not be appropriate, either because of the risk of toxicity in patients with comorbidity or because purine analog-based therapies are unlikely to achieve satisfactory responses. Novel, nonchemotherapeutic treatment regimens are becoming increasingly important in these patients, as well as in patients in whom combination chemotherapy-based treatment has failed or resulted in relapse. Nonchemotherapeutic agents include monoclonal antibodies, glucocorticoids, immunomodulatory drugs, drugs with specific intracellular molecular targets, vaccines and cellular immunotherapies. These agents use diverse mechanisms of action that may complement each other, therefore providing a scientific rationale to investigate combinations of these agents in the treatment of CLL. In this review, we will discuss current knowledge of available nonchemotherapeutic agents, available clinical experience with their use alone and in combination and how these approaches may affect outcomes in patients with CLL.

Antisera induced by infusions of autologous Ad-CD154-leukemia B cells identify ROR1 as an oncofetal antigen and receptor for Wnt5a

We examined the sera of six patients before and after i.v. infusions of autologous chronic lymphocytic leukemia (CLL) cells transduced ex vivo with an adenovirus encoding CD154 (Ad-CD154). Five patients made high-titer antibodies against adenovirus and three made IgG reactive with a leukemia-associated surface antigen, which we identified as ROR1. Anti-ROR1 antibodies were not detected in the sera of untreated patients. We generated anti-ROR1 mAbs and found they reacted specifically with the CLL cells of all patients, but not with nonleukemic leukocytes, a wide variety of normal adult tissues, or blood mononuclear cells, including CD5(+) B cells of healthy adults. ROR1 could bind Wnt5a, which induced activation of NF-kappaB when coexpressed with ROR1 in HEK293 cells and enhanced the survival of CLL cells in vitro, an effect that could be neutralized by posttreatment anti-ROR1 antisera. We conclude that patients with CLL can break immune tolerance to ROR1, which is an oncofetal surface antigen and survival-signaling receptor in this neoplastic disease.