Immunotherapy for non-Hodgkin's lymphoma: monoclonal antibodies and vaccines

Innovative virtual screening of PD-L1 inhibitors: the synergy of molecular similarity, neural networks and GNINA docking

Aims: Immune checkpoint inhibitors targeting PD-L1 are crucial in cancer research for preventing cancer cells from evading the immune system.Materials & methods: This study developed a screening model combining ANN, molecular similarity, and GNINA 1.0 docking to target PD-L1. A database of 2044 substances was compiled from patents.Results: For molecular similarity, the AVALON emerged as the most effective fingerprint, demonstrating an AUC-ROC of 0.963. The ANN model outperformed the Random Forest and Support Vector Classifier in cross-validation and external validation, achieving an average precision of 0.851 and an F1 score of 0.790. GNINA 1.0 was validated through redocking and retrospective control, achieving an AUC of 0.975.Conclusions: From 15235 DrugBank compounds, 22 candidates were shortlisted. Among which (3S)-1-(4-acetylphenyl)-5-oxopyrrolidine-3-carboxylic acid emerged as the most promising.

METTL3-mediated m6A methylation of C1qA regulates the Rituximab resistance of diffuse large B-cell lymphoma cells

Rituximab has been incorporated into the standard treatment regimen for diffuse large B-cell lymphoma (DLBCL), and induces the death of tumor cells via complement-dependent cytotoxicity (CDC). Unfortunately, the resistance of DLBCL cells to Rituximab limits its clinical usefulness. It remains unclear whether the complement system is related to Rituximab resistance in DLBCL. A Rituximab-resistant DLBCL cell line (Farage/R) was generated under the stress of Rituximab. Constituent proteins of the complement system in wild-type Farage cells (Farage/S) and Farage/R cells were analyzed by qPCR, western blotting, and immunofluorescence. In vitro and in vivo knockdown and overexpression studies confirmed that the complement 1Q subcomponent A chain (C1qA) was a regulator of Rituximab resistance. Finally, the mechanism by which C1qA is regulated by m6A methylation was explored. The reader and writer were identified by pull-down studies and RIP-qPCR. Activity of the complement system in Farage/R cells was suppressed. C1qA expression was reduced in Farage/R cells due to post-transcriptional regulation. Furthermore, in vitro and in vivo results showed that C1qA knockdown in Farage/S cells decreased their sensitivity to Rituximab, and C1qA overexpression in Farage/R cells attenuated the Rituximab resistance of those cells. Moreover, METTL3 and YTHDF2 were proven to be the reader and writer for m6A methylation of C1qA, respectively. Knockdown of METTL3 or YTHDF2 in Farage/R cells up-regulated C1qA expression and reduced their resistance to Rituximab. In summary, the aberrant downregulation of C1qA was related to Rituximab resistance in DLBCL cells, and C1qA was found to be regulated by METTL3- and YTHDF2-mediated m6A methylation. Enhancing the response of the complement system via regulation of C1qA might be an effective strategy for inhibiting Rituximab resistance in DLBCL.

Present status and future trends in molecular imaging of lymphocytes

Immune system is emerging as a crucial protagonist in a huge variety of oncologic and non-oncologic conditions including response to vaccines and viral infections (such as SARS-CoV-2). The increasing knowledge of molecular biology underlying these diseases allowed the identification of specific targets and the possibility to use tailored therapies against them. Immunotherapies and vaccines are, indeed, more and more used nowadays for treating infections, cancer and autoimmune diseases and, therefore, there is the need to identify, quantify and monitor immune cell trafficking before and after treatment. This approach will provide crucial information for therapy decision-making. Imaging of B and T-lymphocytes trafficking by using tailored radiopharmaceuticals proved to be a successful nuclear medicine tool. In this review, we will provide an overview of the state of art and future trends for "in vivo" imaging of lymphocyte trafficking and homing by mean of specific receptor-tailored radiopharmaceuticals.

Herbal NF-κB Inhibitors Sensitize Rituximab-Resistant B Lymphoma Cells to Complement-Mediated Cytolysis

Background

Drug resistance remains a serious challenge to rituximab therapy in B-NHL (B cell non-Hodgkin’s lymphoma). CDC (complement-dependent cytotoxicity) has been proposed as a major antitumor mechanism of rituximab, and direct abrogation of CD59 function partially restores rituximab sensitivity with high efficacy. However, universal blockade of CD59 may have deleterious effects on normal cells. Sp1 regulates constitutive CD59 expression, whereas NF-κB and CREB regulate inducible CD59 expression.

Methods

Immunohistochemistry (IHC) assay was used to detect the expression levels of CD59 and other related molecules. Quantitative Real-time PCR (RT-PCR) analysis was used to explore the levels of transcripts in the original and resistant cells. We chose LY8 cells to test the effects of NF-κB and CBP/p300 inhibition on CD59 expression using flow cytometry (FACS). Immunoblotting analysis was employed to detect the effects of curcumin and POH. The in vitro and in vivo experiments were used to evaluate the toxicity and combined inhibitory effect on tumor cells of curcumin and POH.

Results

We demonstrated that herbal (curcumin and perillyl alcohol) blockade of NF-κB specifically suppresses the expression of inducible CD59 but not CD20, thus sensitizing resistant cells to rituximab-mediated CDC. Moreover, activation of NF-κB and CREB is highly correlated with CD59 expression in B-NHL tissues.

Conclusions

Our findings suggest the potential of CD59 expression as a predictor of therapeutic efficacy of NF-κB inhibitors in clinical application as well as the rationality of a NF-κB inhibitor-rituximab regimen in B-NHL therapy.

In vivo Imaging Technologies to Monitor the Immune System

The past two decades have brought impressive advancements in immune modulation, particularly with the advent of both cancer immunotherapy and biologic therapeutics for inflammatory conditions. However, the dynamic nature of the immune response often complicates the assessment of therapeutic outcomes. Innovative imaging technologies are designed to bridge this gap and allow non-invasive visualization of immune cell presence and/or function in real time. A variety of anatomical and molecular imaging modalities have been applied for this purpose, with each option providing specific advantages and drawbacks. Anatomical methods including magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound provide sharp tissue resolution, which can be further enhanced with contrast agents, including super paramagnetic ions (for MRI) or nanobubbles (for ultrasound). Conjugation of the contrast material to an antibody allows for specific targeting of a cell population or protein of interest. Protein platforms including antibodies, cytokines, and receptor ligands are also popular choices as molecular imaging agents for positron emission tomography (PET), single-photon emission computerized tomography (SPECT), scintigraphy, and optical imaging. These tracers are tagged with either a radioisotope or fluorescent molecule for detection of the target. During the design process for immune-monitoring imaging tracers, it is important to consider any potential downstream physiologic impact. Antibodies may deplete the target cell population, trigger or inhibit receptor signaling, or neutralize the normal function(s) of soluble proteins. Alternatively, the use of cytokines or other ligands as tracers may stimulate their respective signaling pathways, even in low concentrations. As in vivo immune imaging is still in its infancy, this review aims to describe the modalities and immunologic targets that have thus far been explored, with the goal of promoting and guiding the future development and application of novel imaging technologies.

Economic evaluation of therapeutic cancer vaccines and immunotherapy: a systematic review

Cancer immunotherapy is a rapidly growing field in oncology. One attractive feature of cancer immunotherapy is the purported combination of minimal toxicity and durable responses. However such treatments are often very expensive. Given the wide-spread concern over rising health care costs, it is important for all stakeholders to be well-informed on the cost and cost-effectiveness of cancer immunotherapies. We performed a comprehensive literature review of cost and cost-effectiveness research on therapeutic cancer vaccines and monoclonal antibodies, to better understand the economic impacts of these treatments. We summarized our literature searches into three tables by types of papers: systematic review of economic studies of a specific agent, cost and cost-effectiveness analysis. Our review showed that out of the sixteen immunotherapy agents approved, nine had relevant published economic studies. Five out of the nine studied immunotherapy agents had been covered in systematic reviews. Among those, only one (rituximab for non-Hodgkin lymphoma) was found to be cost-effective. Of the four immunotherapy drugs not covered in systematic reviews (alemtuzumab, ipilimumab, sipuleucel-T, ofatumumab), high incremental cost-effectiveness ratio (ICER) was reported for each. Many immunotherapies have not had economic evaluations, and those that have been studied show high ICERs or frank lack of cost-effectiveness. One major hurdle in improving the cost-effectiveness of cancer immunotherapies is to identify predictive biomarkers for selecting appropriate patients as recipients of these expensive therapies. We discuss the implications surrounding the economic factors involved in cancer immunotherapies and suggest that further research on cost and cost-effectiveness of newer cancer vaccines and immunotherapies are warranted as this is a rapidly growing field with many new drugs on the horizon.

Obinutuzumab in hematologic malignancies: lessons learned to date

The routine use of anti-CD20 monoclonal antibodies (mAbs) has improved patient outcomes in CD20-positive non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Despite the clinical success achieved with rituximab, relapses are still common with further improvements in anti-CD20 mAb efficacy required. Many novel anti-CD20 antibodies are in development, but obinutuzumab is currently the only type II glycoengineered anti-CD20 mAb in clinical testing. Obinutuzumab has increased antibody-dependent cell-mediated cytotoxicity, reduced complement-dependent cytotoxicity and enhanced direct non-apoptotic cell death. In preclinical models, obinutuzumab induced superior tumor remission compared with rituximab at the equivalent dose levels, and was active in rituximab-refractory tumors. Obinutuzumab exhibits encouraging efficacy as monotherapy in NHL, and combined with chemotherapy in relapsed/refractory NHL and treatment-naïve symptomatic CLL. In a recent randomized, phase III trial in patients with untreated comorbid CLL, overall response rate was significantly greater (78% vs. 65%, P<0.0001) and median progression-free survival was significantly prolonged (26.7 vs. 15.2months, P<0.0001) for obinutuzumab plus chlorambucil vs. rituximab plus chlorambucil. Obinutuzumab is a type II anti-CD20 antibody that utilizes distinct mechanisms of action relative to type I antibodies like rituximab and has led to significant clinical improvement over rituximab in a phase III trial in CLL. Further trials are ongoing to determine whether such improvements in outcome will be seen in CD20-positive B-cell malignancies.

Obinutuzumab (GA101) for the treatment of chronic lymphocytic leukemia and other B-cell non-hodgkin's lymphomas: a glycoengineered type II CD20 antibody

Obinutuzumab (GA101) is a humanized, monoclonal type II CD20 antibody modified by glycoengineering. The glycoengineered Fc portion enhances the binding affinity to the FcγRIII receptor on immune effector cells, resulting in increased antibody-dependent cellular cytotoxicity and phagocytosis. In addition, the type II antibody binding characteristics of obinutuzumab to CD20 lead to an efficient induction of direct non-apoptotic cell death. Preclinical data demonstrated more efficient B-cell depletion in whole blood and superior antitumor activity in xenograft models of obinutuzumab as compared to the type I CD20 antibody rituximab. In previously untreated patients with chronic lymphocytic leukemia (CLL) and comorbidities, obinutuzumab plus chlorambucil increased response rates and prolonged progression-free survival compared with rituximab plus chlorambucil. Obinutuzumab had an acceptable and manageable safety profile, with infusion-related reactions during the first infusion as the most common adverse event. Further phase I/II clinical trials have also shown promising activity in other CD20-positive B-cell non-Hodgkin's lymphomas (NHL). Therefore, several clinical studies are planned or ongoing to investigate obinutuzumab with different combination partners in both untreated and relapsed/refractory patients with different B-cell NHL entities, which in addition to CLL include diffuse large B-cell lymphoma and follicular lymphoma. © 2015 S. Karger GmbH, Freiburg.

Optimization of anti-CD20 humanized antibody hu8E4 by site-directed mutation based on epitope analysis

Despite the effectiveness of the anti-CD20 chimeric antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. Hu8E4 is an anti-CD20 humanized antibody which exhibits markedly higher antitumor activity compared with rituximab. Previous studies have indicated that rituximab and almost all known anti-CD20 murine mAbs recognize the A170/P172 motif within the large extracellular loop of CD20. In this study, we demonstrated that hu8E4 also recognized the A170/P172 motif, suggesting that the epitopes recognized by rituximab and hu8E4 are very similar. Based on this, three single mutations (D57E, Y102K and Y102T) at the heavy chain variable region that can improve the affinity of rituximab were transferred to hu8E4. The results showed that D57E and Y102T but not Y102K successfully enhanced the binding of hu8E4 to CD20. Out of these hu8E4 mutants, hu8E4D57E exhibited the highest affinity. The in vitro and in vivo antitumor activity of hu8E4D57E was further investigated. Our data indicated that hu8E4D57E was as effective as hu8E4 in mediating CDC and inducing apoptosis in B-lymphoma cells, but it was more potent in ADCC than hu8E4. Importantly, hu8E4D57E was shown to be significantly more effective than Hu8E4 in prolonging the survival of SCID mice bearing disseminated B-lymphoma cells, suggesting that it might be a promising therapeutic agent for B-cell lymphomas. Moreover, this study also suggests that the mutations that can improve the affinity of rituximab may be transferred to other anti-CD20 murine mAbs to enhance their binding to CD20.

Update on obinutuzumab in the treatment of B-cell malignancies

INTRODUCTION

The anti-CD20 mAb rituximab has revolutionized the treatment of B-cell malignancies, improving outcome for patients. Despite these improvements, the majority of patients still relapse and become refractory to rituximab. Further efforts to improve anti-CD20 mAb efficacy have recently focused on obinutuzumab /GA101, a novel anti-CD20 mAb glycoengineered to display enhanced Fc-mediated effector mechanisms and induce direct cell death.

AREAS COVERED

We provide an overview of the current insights into the mechanisms of action of obinutuzumab focusing on how structural modifications and differences to rituximab led to designation of obinutuzumab as a type II antibody. We summarize data from preclinical studies and recent clinical trials including the Phase III trial in chronic lymphocytic leukemia (CLL), which led to FDA approval in November 2013.

EXPERT OPINION

Clinical data are now emerging confirming the promise of the initial preclinical data that demonstrated superior efficacy of obinutuzumab over rituximab at similar dosing. The emerging randomized Phase III data from older comorbid patients with previously untreated CLL demonstrated significant improvements in molecular remission rates and median progression-free survival of obinutuzumab plus chlorambucil versus rituximab plus chlorambucil. This emerging data provide reasons to be optimistic that outcomes for patients with B-cell malignancies can be further improved with obinutuzumab.

Inhibition of STAT3 activity re-activates anti-tumor immunity but fails to restore the immunogenicity of tumor cells in a B-cell lymphoma model

A large number of patients with advanced lymphoma become refractory or relapse after initial treatment due to the persistence of minimal residual disease. Ideal immunotherapy strategy for eradicating the minimal residual disease of lymphoma and preventing the tendency to relapse need to be developed. Here, we use a mice model mimicked the disease entities of aggressive B-cell lymphoma dynamically to analyze the host anti-lymphoma immunity during the progression of lymphoma. We have shown that STAT3 activity was gradually enhanced in host immune effector cells with the progression of lymphoma. Inhibition of the STAT3 activity with a small molecule inhibitor was able to effectively enhance the function of both host innate and adaptive immunity, and thereby delayed the progression of lymphoma. Despite the therapeutic benefits were achieved by using of the STAT3 inhibitor, disrupting of STAT3 pathway did not prevent the eventual development of lymphoma due to the presence of point mutation of β2M, which controls immune recognition by T cells. Our findings highlight the complexity of the mechanism of immune evasion; therefore a detailed analysis of genes involved in the immune recognition process should be essential before an elegant immunotherapy strategy could be conducted.

A novel engineered anti-CD20 tracer enables early time PET imaging in a humanized transgenic mouse model of B-cell non-Hodgkins lymphoma

PURPOSE

The aim of this article was to evaluate the use of a novel engineered anti-CD20 protein based on the 10 kDa human fibronectin type 3 domain (FN3) and subsequently compare with (64)Cu-rituximab for positron emission tomography (PET) imaging of CD20.

EXPERIMENTAL DESIGN

The engineered FN3(CD20) and FN3(WT) were produced in Escherichia coli cells at 2 to 5 mg/L, conjugated to DOTA, labeled with (64)Cu, and used for PET imaging of huCD20 expression in B cells. Humanized transgenic mice and subcutaneously xenografted mice each received intravenous (64)Cu-FN3(CD20) or FN3(WT) (3.7 MBq/4 μg Do-FN3 in 200 μL PBS). Control group received a blocking dose (50-fold excess) of unconjugated FN3(CD20) two hours before radiotracer injection. PET imaging was carried out at 1 to 24 hours postinjections.

RESULTS

In vitro assay demonstrated FN3 binds CD20 with 20 nmol/L affinity on CD20-expressing cells. (64)Cu-FN3(CD20) showed clear, high-contrast visualization of huCD20-expressing B cells in the spleen of transgenic mice as early as 1 hour postinjection [38 ± 3% injected dose (ID)/g] and exhibited a spleen-to-blood ratio of 13 by 4 hours. This is higher uptake (P = 0.04) and 10-fold greater signal-to-background (P = 0.04) than the (64)Cu-rituximab antibody radiotracer. Tumor uptake (16.8 ± 1.6 vs. 5.6 ± 1.4%ID/g) and tumor:background ratios were superior for FN3CD20 relative to rituximab in xenograft studies as well.

CONCLUSIONS

The (64)Cu-Do-FN3(CD20) radiotracer represents a novel small, high-affinity binder for imaging human CD20, which may be well suited for B-cell non-Hodgkin's lymphoma imaging in patients at early time points.

Non-Hodgkin's B-cell lymphoma: advances in molecular strategies targeting drug resistance

Non-Hodgkin's lymphoma (NHL) is a heterogeneous class of cancers displaying a diverse range of biological phenotypes, clinical behaviours and prognoses. Standard treatments for B-cell NHL are anthracycline-based combinatorial chemotherapy regimens composed of cyclophosphamide, doxorubicin, vincristine and prednisolone. Even though complete response rates of 40-50% with chemotherapy can be attained, a substantial proportion of patients relapse, resulting in 3-year overall survival rates of about 30%. Relapsed lymphomas are refractory to subsequent treatments with the initial chemotherapy regimen and can exhibit cross-resistance to a wide variety of anticancer drugs. The emergence of acquired chemoresistance thus poses a challenge in the clinic preventing the successful treatment and cure of disseminated B-cell lymphomas. Gene-expression analyses have increased our understanding of the molecular basis of chemotherapy resistance and identified rational targets for drug interventions to prevent and treat relapsed/refractory diffuse large B-cell lymphoma. Acquisition of drug resistance in lymphoma is in part driven by the inherent genetic heterogeneity and instability of the tumour cells. Due to the genetic heterogeneity of B-cell NHL, many different pathways leading to drug resistance have been identified. Successful treatment of chemoresistant NHL will thus require the rational design of combinatorial drugs targeting multiple pathways specific to different subtypes of B-cell NHL as well as the development of personalized approaches to address patient-to-patient genetic heterogeneity. This review highlights the new insights into the molecular basis of chemorefractory B-cell NHL that are facilitating the rational design of novel strategies to overcome drug resistance.

Preclinical studies of targeted therapies for CD20-positive B lymphoid malignancies by Ofatumumab conjugated with auristatin

Utilization of antibodies to deliver highly potent cytotoxic agents to corresponding antigen-overexpressed tumor cells is a clinically validated therapeutic strategy. Ofatumumab (OFA, trade name Arzerra) is a fully human CD20-specific antibody that is active against CD20-positive B-cell lymphoma/chronic lymphocytic leukemia cells. In order to further enhance the anticancer effect of OFA, anti-CD20 OFA has been conjugated with highly cytotoxic monomethyl auristatin E (MMAE) through a cathepsin-B-cleavable valine-citrulline (vc) dipeptide linkage to form OFA-vcMMAE and the anti-tumor activity of OFA-vcMMAE against CD20-positive B lymphoma cells are then evaluated in vitro and in vivo. As a result, conjugation of OFA with MMAE has kept the initial effector functional activities of OFA such as binding affinity, complement-dependent cytotoxicity (CDC) as well as antibody-dependent cell-mediated cytotoxicity (ADCC). In addition, the conjugation of MMAE significantly improved the cytotoxic activity of OFA against CD20-positive cells (i.e., Raji, Daudi and WIL2-S cells) but not against CD20-negative K562 cells. On the other hand, OFA-vcMMAE was modulated from the CD20-positive cell surface and then entered the lysosomes by receptor-mediated endocytosis, underwent proteolytic degradation and released active drug MMAE to induce apoptotic cell death through a caspase-3-like protease-dependent pathway. Surprisingly, OFA-vcMMAE completely inhibited the growth of CD20-positive Daudi and Ramos lymphoma xenografts in vivo, and exhibited greater anti-tumor activity than unconjugated OFA, suggesting that the anti-tumor activity of anti-CD20 antibody can be enhanced by conjugation with MMAE. In the near future, this new approach might be used as a clinical treatment of CD20-positive B lymphoid malignancies.

A glycoengineered anti-CD19 antibody with potent antibody-dependent cellular cytotoxicity activity in vitro and lymphoma growth inhibition in vivo

Human cluster of differentiation (CD) antigen 19 is a B cell-specific surface antigen and an attractive target for therapeutic monoclonal antibody (mAb) approaches to treat malignancies of B cell origin. MEDI-551 is an affinity-optimized and afucosylated CD19 mAb with enhanced antibody-dependent cellular cytotoxicity (ADCC). The results from in vitro ADCC assays with Natural Killer cells as effector cells, demonstrate that MEDI-551 is effective at lower mAb doses than rituximab with multiple cell lines as well as primary chronic lymphocytic leukaemia and acute lymphoblastic leukaemia samples. Targeting CD19 with MEDI-551 was also effective in several severe combined immunodeficiency lymphoma models. Furthermore, the combination of MEDI-551 with rituximab resulted in prolonged suppression of tumour growth, demonstrating that therapeutic mAbs with overlapping effector function can be combined for greater tumour growth inhibition. Together, the data demonstrate that MEDI-551 has potent antitumour activity in preclinical models of B cell malignancies. The results also suggest that the combination of the ADCC-enhanced CD19 mAb with an anti-CD20 mAb could be a novel approach for the treatment of B cell lymphomas.

Development of rituximab-resistant B-NHL clones: an in vitro model for studying tumor resistance to monoclonal antibody-mediated immunotherapy

Therapeutic strategies for cancer include chemotherapy, immunotherapy, and radiation. Such therapies result in significant short-term clinical responses; however, relapses and recurrences occur with no treatments. Targeted therapies using monoclonal antibodies have improved responses with minimal toxicities. For instance, Rituximab (chimeric anti-CD20 monoclonal antibody) was the first FDA-approved monoclonal antibody for the treatment of patients with non-Hodgkin's lymphoma (NHL). The clinical response was significantly improved when used in combination with chemotherapy. However, a subset of patients does not respond or becomes resistant to further treatment. Rituximab-resistant (RR) clones were used as a model to address the potential mechanisms of resistance. In this chapter, we discuss the underlying molecular mechanisms by which rituximab signals the cells and modifies several intracellular survival/antiapoptotic pathways, leading to its chemo/immunosensitizing activities. RR clones were developed to mimic in vivo resistance observed in patients. In comparison with the sensitive parental cells, the RR clones are refractory to rituximab-mediated cell signaling and chemosensitization. Noteworthy, interference with the hyperactivated survival/antiapoptotic pathways in the RR clones with various pharmacological inhibitors mimicked rituximab effects in the parental cells. The development of RR clones provides a paradigm for studying resistance by other anticancer monoclonal antibodies in various tumor models.

Preclinical studies on the mechanism of action and the anti-lymphoma activity of the novel anti-CD20 antibody GA101

GA101 is a novel glycoengineered Type II CD20 monoclonal antibody. When compared with rituximab, it mediates less complement-dependent cytotoxicity (CDC). As expected for a Type II antibody, GA101 appears not to act through CDC and is more potent than the Type I antibody rituximab in inducing cell death via nonclassical induction of apoptosis cytotoxicity, with more direct cytotoxicity and more antibody-dependent cell-mediated cytotoxicity. We evaluated the antitumor activity of GA101 against the human-transformed follicular lymphoma RL model in vivo in severe combined immunodeficient mice (SCID) mice. GA101 induced stronger inhibition of tumor growth than rituximab. Combination of GA101 with cyclophosphamide in vivo confirmed the superiority of GA101 over rituximab. Neutralizing the complement system with cobra venom factor partially impaired the antitumor activity of rituximab, but had no impact on the efficacy of GA101. In vitro GA101 more potently induced cell death of RL cells than rituximab. The expression of a limited number of genes was found to be induced by both antibodies after exposure in vitro. Among these, early growth response 1 and activation transcription factor 3 were confirmed to be increased at the protein level, suggesting a possible role of these proteins in the apoptotic signalling of anti-CD20 antibodies. These data imply that GA101 is superior to rituximab not only as a single agent, but also in combination with chemotherapy. These data suggest the presence of novel signalization pathways activated after exposure to anti-CD20 antibodies.

Stem cell transplantation for indolent lymphoma and chronic lymphocytic leukemia

The indolent lymphomas, including chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) remain incurable with standard therapy. Autologous hematopoietic stem cell transplantation (HSCT) is feasible and has low treatment-related mortality in follicular lymphoma, but there are questions relating to optimal timing of the procedure, conditioning regimen, and late effects. Myeloablative allogeneic HSCT is associated with high treatment-related morbidity and mortality, few late relapses, but is applicable to only a small number of patients. The major focus of HSCT in these lymphomas has been with reduced-intensity conditioning (RIC) allogeneic HSCT, which is applicable to the age distribution of these diseases and which exploits the graft-versus-lymphoma effect in these diseases. Steps to further decrease the morbidity and mortality of the RIC HSCT and in particular to reduce the incidence of chronic extensive graft-versus-host disease (GVHD) while maintaining tumor control remain the major focus. Many potential treatments are available for indolent lymphomas and CLL, and appropriate patient selection and the timing of HSCT remain controversial. The use of HSCT must always be weighed against the risk of the underlying disease, particularly in a setting where improvements in treatment are leading to improved outcome.

Imaging and therapy with rituximab anti-CD20 immunotherapy in an animal model of central nervous system lymphoma

PURPOSE

To evaluate the effect of rituximab monoclonal antibody (mAb) on MRI tumor volumetrics and efficacy in a rat model of central nervous system (CNS) lymphoma when delivery to the brain was optimized with osmotic blood-brain barrier disruption (BBBD).

EXPERIMENTAL DESIGN

Female nude rats with intracerebral MC116 human B-cell lymphoma xenografts underwent baseline MRI and were randomized into 5 groups (n = 6 per group): (i) BBBD saline control; (ii) methotrexate with BBBD; (iii) rituximab with BBBD; (iv) rituximab and methotrexate with BBBD; and (v) intravenous rituximab. Tumor volumes were assessed by MRI at 1 week, and rats were followed for survival.

RESULTS

BBBD increased delivery of yttrium-90-radiolabeled mAb in the model of CNS lymphoma. Control rats showed 201 ± 102% increase in tumor volume on MRI 1 week after entering the study and median 14-day survival (range: 6-33). Tumor growth on MRI was slowed in the methotrexate treatment group, but survival time (median: 7 days; range: 5-12) was not different from controls. Among 17 evaluable rats treated with rituximab, 10 showed decreased tumor volume on MRI. All rituximab groups had increased survival compared with control, with a combined median of 43 days (range: 20-60, P < 0.001). There were no differences by route of delivery or combination with methotrexate.

CONCLUSIONS

Rituximab was effective at decreasing tumor volume and improving survival in a model of CNS lymphoma and was not affected by combination with methotrexate or by BBBD. We suggest that rituximab warrants further study in human primary CNS lymphoma.

Gene-modified T lymphocytes in the setting of hematopoietic cell transplantation: potential benefits and possible risks

INTRODUCTION

Allogeneic hematopoietic cell transplantation (HCT) is a consolidated treatment for several hematologic malignancies. Donor T lymphocytes can mediate a graft versus tumor (GVT) effect and control opportunistic infections but can also cause severe graft versus host disease (GVHD). Gene-transfer strategies are appealing tools to modulate T cell functions when infused after HCT.

AREAS COVERED

The current and potential future applications of T cell gene-transfer approaches to HCT. This review is not limited to GVHD control but covers the issues of GVT and immune reconstitution. Clinical data are used to discuss more general issues, perspectives and concerns common to gene-modification of T cells. An overview of the results and limitations emerging from clinical trials with herpes simplex virus-thymidine kinase (HSV-TK) engineered lymphocytes is provided. The review provides perspectives on additional gene-transfer strategies, currently at preclinical level or that have just entered clinical trials, to increase the efficacy and safety of HCT.

EXPERT OPINION

Gene-transfer can positively interfere with T cell functions after HCT. TK-lymphocytes have proven effective in controlling GVHD while retaining an acceptable GVT effect. Strategies exploiting new suicide molecules or engineered T cell receptors (TCRs) should be further explored to address current limitations with TK-lymphocytes and augment the efficacy and specificity of GVT and antiviral activity.

B-cell depletion in vitro and in vivo with an afucosylated anti-CD19 antibody

The pan B-cell surface antigen CD19 is an attractive target for therapeutic monoclonal antibody (mAb) approaches. We have generated a new afucosylated anti-human (hu)CD19 mAb, MEDI-551, with increased affinity to human FcγRIIIA and mouse FcγRIV and enhanced antibody-dependent cellular cytotoxicity (ADCC). During in vitro ADCC assays with B-cell lines, MEDI-551 is effective at much lower mAb concentrations than the fucosylated parental mAb anti-CD19-2. Furthermore, the afucosylated CD19 mAb MEDI-551 depleted B cells from normal donor peripheral blood mononuclear cell samples in an autologous ADCC assay, as well as blood and tissue B cells in human CD19/CD20 double transgenic (Tg) mice at lower concentrations than that of the positive control mAb rituximab. In huCD19/CD20 Tg mice, both macrophage-mediated phagocytosis and complement-dependent cytotoxicity contribute to depletion with rituximab; MEDI-551 did not require complement for maximal B-cell depletion. Furthermore, extended B-cell depletion from the blood and spleen was achieved with MEDI-551, which is probably explained by bone marrow B-cell depletion in huCD19/CD20 Tg mice relative to the control mAb rituximab. In summary, MEDI-551 has potent B-cell-depleting activity in vitro and in vivo and may be a promising new approach for the treatment of B-cell malignancies and autoimmune diseases.

Novel anti-CD20 antibody TGLA with enhanced antibody-dependent cell-mediated cytotoxicity mediates potent anti-lymphoma activity

Rituximab is the first anti-cancer antibody approved by the FDA for the treatment of B-cell lymphoma. However, its efficacy remains variable and often modest. Some patients are initially unresponsive to rituximab or later develop resistance to it, and require alternative therapies. Rituximab activity has been thought to involve antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and apoptosis. Present studies suggest that the patients unresponsive to rituximab may be helped with other CD20 antibodies with enhanced activities. In this study, we characterized a novel anti-CD20 chimeric antibody, TGLA, which binds to various B-cell lines specially and shares an epitope with rituximab. TGLA shows equal activities with rituximab, such as CDC, cell growth arrest and so on. Interestingly, TGLA also shows significant ADCC activity. Immunotherapeutic studies further show that TGLA is far more effective in delaying tumor growth than rituximab. These findings suggest that the ADCC-enhanced anti-CD20 antibody TGLA might be an alternative therapeutic agent for B-cell lymphoma.

Lymphoma endothelium preferentially expresses Tim-3 and facilitates the progression of lymphoma by mediating immune evasion

Angiogenesis is increasingly recognized as an important prognosticator associated with the progression of lymphoma and as an attractive target for novel modalities. We report a previously unrecognized mechanism by which lymphoma endothelium facilitates the growth and dissemination of lymphoma by interacting with circulated T cells and suppresses the activation of CD4⁺ T cells. Global gene expression profiles of microdissected endothelium from lymphoma and reactive lymph nodes revealed that T cell immunoglobulin and mucin domain–containing molecule 3 (Tim-3) was preferentially expressed in lymphoma-derived endothelial cells (ECs). Clinically, the level of Tim-3 in B cell lymphoma endothelium was closely correlated to both dissemination and poor prognosis. In vitro, Tim-3⁺ ECs modulated T cell response to lymphoma surrogate antigens by suppressing activation of CD4⁺ T lymphocytes through the activation of the interleukin-6–STAT3 pathway, inhibiting Th1 polarization, and providing protective immunity. In a lymphoma mouse model, Tim-3–expressing ECs promoted the onset, growth, and dissemination of lymphoma by inhibiting activation of CD4⁺ T cells and Th1 polarization. Our findings strongly argue that the lymphoma endothelium is not only a vessel system but also a functional barrier facilitating the establishment of lymphoma immune tolerance. These findings highlight a novel molecular mechanism that is a potential target for enhancing the efficacy of tumor immunotherapy and controlling metastatic diseases.

Targeted delivery of interferon-alpha via fusion to anti-CD20 results in potent antitumor activity against B-cell lymphoma

The anti-CD20 antibody rituximab has substantially improved outcomes in patients with B-cell non-Hodgkin lymphomas. However, many patients are not cured by rituximab-based therapies, and overcoming de novo or acquired rituximab resistance remains an important challenge to successful treatment of B-cell malignancies. Interferon-alpha (IFNalpha) has potent immunostimulatory properties and antiproliferative effects against some B-cell cancers, but its clinical utility is limited by systemic toxicity. To improve the efficacy of CD20-targeted therapy, we constructed fusion proteins consisting of anti-CD20 and murine or human IFNalpha. Fusion proteins had reduced IFNalpha activity in vitro compared with native IFNalpha, but CD20 targeting permitted efficient antiproliferative and proapoptotic effects against an aggressive rituximab-insensitive human CD20(+) murine lymphoma (38C13-huCD20) and a human B-cell lymphoma (Daudi). In vivo efficacy was demonstrated against established 38C13-huCD20 grown in syngeneic immunocompetent mice and large, established Daudi xenografts grown in nude mice. Optimal tumor eradication required CD20 targeting, with 87% of mice cured of rituximab-insensitive tumors. Gene knockdown studies revealed that tumor eradication required expression of type I IFN receptors on the tumor cell surface. Targeting type I IFNs to sites of B-cell lymphoma by fusion to anti-CD20 antibodies represents a potentially useful strategy for treatment of B-cell malignancies.

Severe idiopathic erythroblastic synartesis: successful treatment with the anti-CD20 monoclonal antibody rituximab

Erythroblastic synartesis is a very rare disorder, considered to be caused by autoimmune mechanisms, leading to aggregation of erythroid precursor cells in the bone marrow and subsequently to acquired dyserythropoiesis with severe, transfusion-dependent anemia. An association with lymphoproliferative or autoimmune diseases has been reported or strongly suggested in all six published cases. Here, we report a young patient with severe idiopathic erythroblastic synartesis without an underlying disease, who was successfully treated with rituximab, an anti-CD20 monoclonal antibody. The patient received rituximab at a dose of 375 mg/m(2) once weekly for 4 wk after failure of both immunosuppressive therapies with corticosteroids and intravenous immunoglobulins. At a follow-up of 30 months after treatment, the patient is still in continuous complete remission without any further treatment, suggesting that rituximab may induce prolonged remissions and eventually cure in this rare disease.

Characterization of a humanized anti-CD20 antibody with potent antitumor activity against B-cell lymphoma

Despite the effectiveness of the anti-CD20 chimeric antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. In this study, a humanized anti-CD20 antibody, hu8E4, was generated by complementarity-determining region grafting method. Hu8E4 was as effective as rituximab in mediating antibody-dependent cellular cytotoxicity and inducing apoptosis in B-lymphoma cells, but it exhibited much more potent complement-dependent cytotoxicity than rituximab. Immunotherapeutic studies showed that hu8E4 was significantly more effective than rituximab in prolonging the survival of severe combined immunodeficient mice bearing human B-cell lymphomas, suggesting that it might be a promising therapeutic agent for B-cell lymphomas.

Intratumoral but not systemic delivery of CpG oligodeoxynucleotide augments the efficacy of anti-CD20 monoclonal antibody therapy against B cell lymphoma

The anti-CD20 monoclonal antibody rituximab (Rituxan) has become a mainstay in the treatment of B cell non-Hodgkin lymphomas. The mechanisms of action for rituximab include antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity, and apoptosis induction. Combination of anti-CD20 antibodies with immunostimulatory agents may improve their efficacy via enhancement of one or more of these mechanisms. Toll-like receptor 9 agonist CpG oligodeoxynucleotides administered systemically have been studied in clinical trials with and without rituximab. However, recent data suggest that intratumoral (IT) delivery of CpG has advantages in the treatment of tumors. Using a syngeneic murine B cell lymphoma line expressing human CD20, we found that IT, but not systemically administered CpG significantly improved the efficacy of rituximab against 7-day established tumors. Rituximab plus IT CpG could eradicate tumors from 42% of mice, whereas systemically administered CpG, with or without rituximab, did not achieve tumor eradication. Both natural killer cells and complement participated in the cure of tumors by rituximab plus IT CpG, apparently by increasing tumor cell sensitivity to complement and ADCC lysis, and by augmenting the cytotoxicity of ADCC effectors. No role for T cells in mediating tumor eradication was demonstrated in this model. These results suggest that previous clinical trials in B cell lymphoma combining systemic administration of CpG with rituximab may have employed suboptimal routes of CpG delivery. Future trials combining IT CpG with anti-CD20 antibodies or the antibody-mediated targeting of CpG directly to the sites of B cell lymphoma may thus be warranted.

Adoptive T-cell therapy for B-cell malignancies

The success of allogeneic hematopoietic cell transplantation (HCT) for B-cell malignancies is evidence that these tumors can be eliminated by T lymphocytes. This has encouraged the development of specific adoptive T-cell therapy, both for augmenting the anti-tumor effect of HCT and for patients not undergoing HCT. T cells that are capable of recognizing antigens expressed on malignant B cells may be recruited from the endogenous repertoire or engineered to express tumor-targeting receptors. Critical insights into the qualities of T cells that enable their persistence and function in vivo have been derived, and obstacles to effective T-cell-mediated tumor eradication are being elucidated. These advances provide the tools to translate adoptive T-cell transfer into reliable clinical therapies.

Follicular lymphoma cells induce T-cell immunologic synapse dysfunction that can be repaired with lenalidomide: implications for the tumor microenvironment and immunotherapy

An important hallmark of cancer progression is the ability of tumor cells to evade immune recognition. Understanding the relationship between neoplastic cells and the immune microenvironment should facilitate the design of improved immunotherapies. Here we identify impaired T-cell immunologic synapse formation as an active immunosuppressive mechanism in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). We found a significant reduction in formation of the F-actin immune synapse in tumor-infiltrating T cells (P < .01) from lymphoma patients compared with age-matched healthy donor cells. Peripheral blood T cells exhibited this defect only in patients with leukemic-phase disease. Moreover, we demonstrate that this T-cell defect is induced after short-term tumor cell contact. After 24-hour coculture with FL cells, previously healthy T cells showed suppressed recruitment of critical signaling proteins to the synapse. We further demonstrate repair of this defect after treatment of both FL cells and T cells with the immunomodulatory drug lenalidomide. Tissue microarray analysis identified reduced expression of the T-cell synapse signature proteins, including the cytolytic effector molecule Rab27A associated with poor prognosis, in addition to reduced T-cell numbers and activity with disease transformation. Our results highlight the importance of identifying biomarkers and immunotherapeutic treatments for repairing T-cell responses in lymphoma.

Therapeutic effect of CD137 immunomodulation in lymphoma and its enhancement by Treg depletion

Despite the success of passive immunotherapy with monoclonal antibodies (mAbs), many lymphoma patients eventually relapse. Induction of an adaptive immune response may elicit active and long-lasting antitumor immunity, thereby preventing or delaying recurrence. Immunomodulating mAbs directed against immune cell targets can be used to enhance the immune response to achieve efficient antitumor immunity. Anti-CD137 agonistic mAb has demonstrated antitumor efficacy in various tumor models and has now entered clinical trials for the treatment of solid tumors. Here, we investigate the therapeutic potential of anti-CD137 mAb in lymphoma. We found that human primary lymphoma tumors are infiltrated with CD137+ T cells. We therefore hypothesized that lymphoma would be susceptible to treatment with anti-CD137 agonistic mAb. Using a mouse model, we demonstrate that anti-CD137 therapy has potent antilymphoma activity in vivo. The antitumor effect of anti-CD137 therapy was mediated by both natural killer (NK) and CD8 T cells and induced long-lasting immunity. Moreover, the antitumor activity of anti-CD137 mAb could be further enhanced by depletion of regulatory T cell (T(regs)). These results support the evaluation of anti-CD137 therapy in clinical trials for patients with lymphoma.

In vitro end points for the assessment of cellular immune response-modulating drugs

BACKGROUND

The concept of immunotoxicology and the development of a battery of immune-function assays to screen potential immunotoxic compounds have been increasingly used in the past. Immunotoxic outcome generally seems appropriate to evaluate the risk in drug development. Improving this approach is possible, by using methods now available, to study the effect of a chemical compound on the immune system.

OBJECTIVE

The goal of this review is to provide an overview of the current and recent methodologies for testing the immunological effect and immunotoxic risks in drug candidates.

METHODS

The methodological details here discussed include a synthetic description of the immunocompetent cells in cell-mediated immunity and the choice of the most appropriate assay (bioassays, immunoassays, molecular biology techniques, flow cytometry).

CONCLUSION

This review offers an assessment of in vitro models to study the toxic impact of (bio)pharmaceuticals on cellular immune system and aid drug scientists in understanding the significance and the methods to approach immunotoxicology.

Potent antitumor activity of the anti-CD19 auristatin antibody drug conjugate hBU12-vcMMAE against rituximab-sensitive and -resistant lymphomas

Despite major advances in the treatment of non-Hodgkin lymphoma (NHL), including the use of chemotherapeutic agents and the anti-CD20 antibody rituximab, the majority of patients eventually relapse, and salvage treatments with non-cross-resistant compounds are needed to further improve patient survival. Here, we evaluated the antitumor effects of the microtubule destabilizing agent monomethyl auristatin E (MMAE) conjugated to the humanized anti-CD19 antibody hBU12 via a protease-sensitive valine-citrulline (vc) dipeptide linker. hBU12-vcMMAE induced potent tumor cell killing against rituximab-sensitive and -resistant NHL cell lines. CD19 can form heterodimers with CD21, and high levels of CD21 were reported to interfere negatively with the activity of CD19-targeted therapeutics. However, we observed comparable internalization, intracellular trafficking, and drug release in CD21(low) and CD21(high), rituximab-sensitive and -refractory lymphomas treated with hBU12-vcMMAE. Furthermore, high rates of durable regressions in mice implanted with these tumors were observed, suggesting that both rituximab resistance and CD21 expression levels do not impact on the activity of hBU12-vcMMAE. Combined, our data suggest that hBU12-vcMMAE may represent a promising addition to the treatment options for rituximab refractory NHL and other hematologic malignancies, including acute lymphoblastic leukemia.

Durable complete responses from therapy with combined epratuzumab and rituximab: final results from an international multicenter, phase 2 study in recurrent, indolent, non-Hodgkin lymphoma

BACKGROUND

In this international, multicenter trial, the authors evaluated rituximab (anti-CD20) plus epratuzumab (anti-CD22) in patients with postchemotherapy relapsed/refractory, indolent non-Hodgkin lymphoma (NHL), including long-term efficacy.

METHODS

Forty-nine patients with follicular NHL (FL) (N = 41) or small lymphocytic lymphoma (SLL) (N = 7) received intravenous epratuzumab 360 mg/m2 and then intravenous rituximab 375 mg/m2 weekly x4. The regimen was tolerated well.

RESULTS

Twenty-two of 41 patients with FL (54%) had an objective response (OR), including 10 (24%) complete responses (CR) (CR/unconfirmed CR [CRu]), whereas 4 of 7 patients with SLL (57%) had ORs, including 3 (43%) with CR/CRu. Rituximab-naive patients (N = 34) had an OR rate of 50% (26% CR/CRu rate), whereas patients who previously responded to rituximab (N = 14) had an OR rate of 64% (29% CR/CRu rate). An OR rate of 85% was observed in patients with FL who had Follicular Lymphoma International Prognostic Index (FLIPI) risk scores of 0 or 1 (N = 13), whereas 28 patients with intermediate or high-risk FLIPI scores (> or =2) had an OR rate of 39% (18% CR/CRu rate). In patients with FL, the median response duration was 13.4 months, and that duration increased to 29.1 months for 10 patients who had a CR/CRu, including 4 patients who had durable responses with remissions that continued for >4 years. In patients with SLL, the median response duration was 20 months, including 1 patient who had a response that continued for >3 years.

CONCLUSIONS

The combination of epratuzumab and rituximab induced durable responses in patients with recurrent, indolent NHL.

Targeting cytochrome P450 CYP1B1 with a therapeutic cancer vaccine

The role that the immune system plays in limiting tumor formation and growth is becoming increasingly clear and passive immunotherapeutic approaches, such as the use of monoclonal antibodies, are now being successfully applied in clinical practice. Active immunization against tumors, however, has not yet been shown to have the same level of clinical efficacy. Two important reasons for this lack of efficacy have to do with the antigens being targeted, as well as the immunization approaches that have been tested. This review will highlight some of the requirements thought to be important for the successful development of an active immunization approach, with a focus on the ongoing development efforts for a novel agent targeting the cytochrome P450 family member, CYP1B1.

T-cell modulation combined with intratumoral CpG cures lymphoma in a mouse model without the need for chemotherapy

We have previously shown that intratumoral injection of CpG oligodeoxynucleotide plus systemic chemotherapy can induce a T-cell immune response against lymphoma and serve as a therapeutic vaccine to cure tumors in a murine model. Here, we demonstrate that antibody-mediated modulation of T cells increases the efficacy of CpG vaccination, thereby eliminating the need for chemotherapy. T-cell modulation was accomplished by targeting both effector and regulatory T-cell populations using systemic administration of monoclonal antibodies against OX40, CTLA4, GITR, and folate receptor 4 (FR4). Each of these antibodies enhanced the effect of intratumoral CpG. Some pairwise combinations of these antibodies potentiated T-cell modulation and further enhanced the efficacy of CpG vaccination. Specifically, the combination of anti-OX40 and anti-CTLA4 which enhance activation and block cell-intrinsic negative regulatory circuits in T cells, respectively, was especially potent. When combined with intratumoral CpG, it induced antitumor CD4 and CD8 T-cell immunity, cured large and systemic lymphoma tumors without chemotherapy, and provided long-lasting immunity against tumor rechallenge. Our results show that the combination of intratumoral CpG and immunomodulatory T-cell antibodies has promise for therapeutic vaccination against lymphoma. These reagents are becoming available for human clinical trials.

Enhanced anti-tumor immunity generated by Rituximab-coated tumor cell vaccine

Rituximab is a chimeric monoclonal antibody against CD20, and has been used to treat malignant tumors derived from B cell. We designed a tumor cell vaccine modified by Rituximab, and evaluated anti-tumor effect in human CD20 gene transfected mice tumor model in vivo, and in human CTLs induction by mixed lymphocyte tumor cell culture in vitro. The results demonstrated that the Rituximab-coated tumor cell vaccine had a significant therapeutic effect against tumor pulmonary metastasis formation. Antibody depletion experiments showed CD8+ T Cells were essential for the anti-tumor effect but not NK cells. Capture rate of tumor cells by DCs, which were detected by flow cytometry, was increased by adding Rituximab. The tumor specific cytolysis could be induced by Rituximab-coated tumor cell in human in vitro assay. This therapeutic strategy provides a simple way to potentialize CTLs function to combat cancer and may promote more clinical consideration in immunotherapy for tumors. Rituximab-coated tumor cell vaccine also expanded the clinical Rituximab applications.

Expression of a CD20-specific chimeric antigen receptor enhances cytotoxic activity of NK cells and overcomes NK-resistance of lymphoma and leukemia cells

Despite the clinical success of CD20-specific antibody rituximab, malignancies of B-cell origin continue to present a major clinical challenge, in part due to an inability of the antibody to activate antibody-dependent cell-mediated cytotoxicity (ADCC) in some patients, and development of resistance in others. Expression of chimeric antigen receptors in effector cells operative in ADCC might allow to bypass insufficient activation via FcgammaRIII and other resistance mechanisms that limit natural killer (NK)-cell activity. Here we have generated genetically modified NK cells carrying a chimeric antigen receptor that consists of a CD20-specific scFv antibody fragment, via a flexible hinge region connected to the CD3zeta chain as a signaling moiety. As effector cells we employed continuously growing, clinically applicable human NK-92 cells. While activity of the retargeted NK-92 against CD20-negative targets remained unchanged, the gene modified NK cells displayed markedly enhanced cytotoxicity toward NK-sensitive CD20 expressing cells. Importantly, in contrast to parental NK-92, CD20-specific NK cells efficiently lysed CD20 expressing but otherwise NK-resistant established and primary lymphoma and leukemia cells, demonstrating that this strategy can overcome NK-cell resistance and might be suitable for the development of effective cell-based therapeutics for the treatment of B-cell malignancies.

BiovaxID idiotype vaccination: active immunotherapy for follicular lymphoma

Although advanced-stage follicular lymphoma (FL) has been considered incurable with standard therapy, novel strategies that utilize immunotherapy provide opportunities for prolonging disease-free survival. While passive immunotherapy with antibodies targeting the CD20 antigen on B cells has been the most widely applied lymphoma immunotherapy, active immunization with vaccines derived from the immunoglobulin idiotype present on the surface of FL provides an opportunity to induce specific humoral and cellular immune responses to the tumor, and have been demonstrated to produce significant benefits in prolonging disease-free survival. Promoting the benefits of all forms of immunotherapy will likely depend upon improving complete remission rates with initial treatment. BiovaxID, a patient-specific idiotype vaccine, has demonstrated durable remissions when administered to FL patients in first complete remission along with keyhole limpet hemocyanin and granulocyte-macrophage colony-stimulating factor, and is now undergoing evaluation in a pivotal Phase III clinical trial.

Lymphoma immunotherapy with CpG oligodeoxynucleotides requires TLR9 either in the host or in the tumor itself

Established widely metastatic tumor was cured in a transplanted mouse B cell lymphoma model, by the combination of chemotherapy plus intratumoral injection of oligodeoxynucleotides containing unmethylated C-G motifs (CpG). This therapeutic effect required that the CpG be injected directly into the tumor and was dependent on CD8 T cells. Although the efficacy of CpG oligodeoxynucleotides has been thought to depend on the expression of TLR9, we unexpectedly found that tumor rejection did not require host expression of TLR9. By using a TLR9-deficient tumor and a TLR9KO host, we demonstrate that TLR9 expression either by the host or the tumor is required. These results indicate that activation of Ag presentation by cells within the tumor via TLR9 stimulation can be an effective form of immunotherapy. This study forms the basis of an ongoing clinical trial in patients with lymphoma.

Overview of early response assessment in lymphoma with FDG-PET

Early assessment of response to chemotherapy with fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) is becoming a routine part of management in patients with Hodgkin lymphoma (HL) and histologically aggressive non-Hodgkin lymphoma (NHL). Changes in FDG uptake can occur soon after the initiation of therapy and they precede changes in tumour volume. Recent studies in uniform populations of aggressive lymphomas (predominantly diffuse large B cell lymphomas) and HL have clarified the value of early response assessment with PET. These trials show that PET imaging after 2-3 chemotherapy cycles is far superior to CT-based imaging in predicting progression-free survival and can be at least as reliable as definitive response assessment at the end of therapy. This information is of great potential value to patients, but oncologists should be cautious in the use of early PET response in determining choice of therapy until some critical questions are answered. These include: When is the best time to use PET for response assessment? What is the best methodology, visual or quantitative? (For HL at least, visual reading appears superior to an SUV-based assessment). Can early responders be cured with less intensive therapy? Will survival be better for patients treated more intensively because they have a poor interim metabolic response? In the future, early PET will be crucial in developing response-adapted therapy but without further carefully designed clinical trials, oncologists will remain uncertain how best to use this new information.

PKC zeta mTOR pathway: a new target for rituximab therapy in follicular lymphoma

Previous studies have documented that, in malignant B cells, rituximab elicits a complex and not yet totally understood signaling network contributing to its antitumor effect. In this context, we investigated the role of protein kinase C zeta (PKCzeta), an atypical PKC isoform, in the cellular response to rituximab. We found that follicular lymphoma cells displayed an increase in PKCzeta expression and activity levels, compared with nonmalignant B cells, and that this enzyme was a critical regulator of the classical MAPK module by stimulating Raf-1 kinase activity. PKCzeta appeared to be a significant contributor of abnormal mTOR regulation in follicular lymphoma cells through a MAPK-dependent mechanism. Rituximab was found to inhibit the PKCzeta/MAPK/mTOR module in these cells but not in other B-cell lymphomas. Importantly, the expression of a constitutively active form of PKCzeta resulted in an efficient protection of these cells toward rituximab. Altogether, our study describes a new regulatory component of mTOR pathway in follicular cell lymphoma and demonstrates that PKCzeta is a target for rituximab. Therefore, PKCzeta could represent an important parameter for rituximab efficacy and a promising target for future targeted therapy in follicular lymphoma.