Rebuilding Human Leukocyte Antigen Class II–Restricted Minor Histocompatibility Antigen Specificity in Recall Antigen-Specific T Cells by Adoptive T Cell Receptor Transfer: Implications for Adoptive Immunotherapy

Preclinical evaluation of the CD38-targeting engineered toxin body MT-0169 against multiple myeloma

Despite significant progress in the treatment of multiple myeloma (MM), relapsed/refractory patients urgently require more effective therapies. We here describe the discovery, mechanism of action, and preclinical anti-MM activity of engineered toxin body MT-0169, a next-generation immunotoxin comprising a CD38-specific antibody fragment linked to a de-immunized Shiga-like toxin A subunit (SLTA) payload. We show that specific binding of MT-0169 to CD38 on MM cell lines triggers rapid internalization of SLTA, causing cell death via irreversible ribosome inhibition, protein synthesis blockade, and caspase 3/7 activation. In co-culture experiments, bone marrow mesenchymal stromal cells did not induce drug resistance against MT-0169. In the preclinical setting, MT-0169 effectively lysed primary MM cells from newly diagnosed and heavily pretreated MM patients, including those refractory to daratumumab, with minimal toxicity against nonmalignant hematopoietic cells. MM cell lysis showed a significant correlation with their CD38 expression levels but not with cytogenetic risk, tumor load, or number of prior lines of therapy. Finally, MT-0169 showed efficient in vivo anti-MM activity in various mouse xenograft models, including one in which MM cells are grown in a humanized bone marrow-like niche. These findings support clinical investigation of MT-0169 in relapsed/refractory MM patients, including those refractory to CD38-targeting immunotherapies.

Bone Marrow Mesenchymal Stromal Cells Can Render Multiple Myeloma Cells Resistant to Cytotoxic Machinery of CAR T Cells through Inhibition of Apoptosis

PURPOSE

The microenvironment of multiple myeloma (MM) can critically impair therapy outcome, including immunotherapies. In this context, we have earlier demonstrated that bone marrow mesenchymal stromal cells (BMMSC) protect MM cells against the lytic machinery of MM-reactive cytotoxic T cells (CTL) and daratumumab-redirected natural killer (NK) cells through the upregulation of antiapoptotic proteins Survivin and Mcl-1 in MM cells. Here, we investigated the significance of this mode of immune escape on T cells engineered to express chimeric antigen receptors (CAR T cells).

EXPERIMENTAL DESIGN

We tested the cytolytic ability of a panel of 10 BCMA-, CD38-, and CD138-specific CAR T cells with different affinities against a model MM cell line and against patient-derived MM cells in the presence versus absence of BMMSCs.

RESULTS

Although BMMSCs hardly protected MM cells from lysis by high-affinity, strongly lytic BCMA- and CD38-CAR T cells, they significantly protected against lower affinity, moderately lytic BCMA-, CD38-, and CD138-specific CAR T cells in a cell-cell contact-dependent manner. Overall, there was a remarkable inverse correlation between the protective ability of BMMSCs and the lytic activity of all CAR T cells, which was dependent on CAR affinity and type of costimulation. Furthermore, BMMSC-mediated resistance against CAR T cells was effectively modulated by FL118, an inhibitor of antiapoptotic proteins Survivin, Mcl-1, and XIAP.

CONCLUSIONS

These results extend our findings on the negative impact of the microenvironment against immunotherapies and suggest that outcome of CAR T cell or conventional CTL therapies could benefit from inhibition of antiapoptotic proteins upregulated in MM cells through BMMSC interactions.

Healthy cells functionally present TAP-independent SSR1 peptides: implications for selection of clinically relevant antigens

Tumors with an impaired transporter associated with antigen processing (TAP) present several endoplasmic reticulum-derived self-antigens on HLA class I (HLA-I) which are absent on healthy cells. Selection of such TAP-independent antigens for T cell-based immunotherapy should include analysis of their expression on healthy cells to prevent therapy-induced adverse toxicities. However, it is unknown how the absence of clinically relevant antigens on healthy cells needs to be validated. Here, we monitored TAP-independent antigen presentation on various healthy cells after establishing a T cell tool recognizing a TAP-independent signal sequence receptor 1-derived antigen. We found that most but not all healthy cells present this antigen under normal and inflammatory conditions, indicating that TAP-independent antigen presentation is a variable phenomenon. Our data emphasize the necessity of extensive testing of a wide variety of healthy cell types to define clinically relevant TAP-independent antigens that can be safely targeted by immunotherapy.

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The ER-resident SSR1 holds an antigenic peptide that is processed independently of TAP

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TAP-independent peptide presentation is functional in healthy cell types

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TAP-independent SSR1-derived antigen presentation varies between healthy cells

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This exposes safety and efficacy risks of clinical TAP-independent peptide targeting

Identification of minor histocompatibility antigens based on the 1000 Genomes Project

Minor histocompatibility antigens are highly immunogeneic polymorphic peptides playing crucial roles in the clinical outcome of HLA-identical allogeneic stem cell transplantation. Although the introduction of genome-wide association-based strategies significantly has accelerated the identification of minor histocompatibility antigens over the past years, more efficient, rapid and robust identification techniques are required for a better understanding of the immunobiology of minor histocompatibility antigens and for their optimal clinical application in the treatment of hematologic malignancies. To develop a strategy that can overcome the drawbacks of all earlier strategies, we now integrated our previously developed genetic correlation analysis methodology with the comprehensive genomic databases from the 1000 Genomes Project. We show that the data set of the 1000 Genomes Project is suitable to identify all of the previously known minor histocompatibility antigens. Moreover, we demonstrate the power of this novel approach by the identification of the new HLA-DP4 restricted minor histocompatibility antigen UTDP4-1, which despite extensive efforts could not be identified using any of the previously developed biochemical, molecular biological or genetic strategies. The 1000 Genomes Project-based identification of minor histocompatibility antigens thus represents a very convenient and robust method for the identification of new targets for cancer therapy after allogeneic stem cell transplantation.

Towards effective and safe immunotherapy after allogeneic stem cell transplantation: identification of hematopoietic-specific minor histocompatibility antigen UTA2-1

Donor T cells directed at hematopoietic system-specific minor histocompatibility antigens (mHags) are considered important cellular tools to induce therapeutic graft-versus-tumor (GvT) effects with low risk of graft-versus-host disease after allogeneic stem cell transplantation. To enable the clinical evaluation of the concept of mHag-based immunotherapy and subsequent broad implementation, the identification of more hematopoietic mHags with broad applicability is imperative. Here we describe novel mHag UTA2-1 with ideal characteristics for this purpose. We identified this antigen using genome-wide zygosity-genotype correlation analysis of a mHag-specific CD8⁺ cytotoxic T lymphocyte (CTL) clone derived from a multiple myeloma patient who achieved a long-lasting complete remission after donor lymphocyte infusion from an human leukocyte antigen (HLA)-matched sibling. UTA2-1 is a polymorphic peptide presented by the common HLA molecule HLA-A*02:01, which is encoded by the bi-allelic hematopoietic-specific gene C12orf35. Tetramer analyses demonstrated an expansion of UTA2-1-directed T cells in patient blood samples after several donor T-cell infusions that mediated clinical GvT responses. More importantly, UTA2-1-specific CTL effectively lysed mHag⁺ hematopoietic cells, including patient myeloma cells, without affecting non-hematopoietic cells. Thus, with the capacity to induce relevant immunotherapeutic CTLs, it's HLA-A*02 restriction and equally balanced phenotype frequency, UTA2-1 is a highly valuable mHag to facilitate clinical application of mHag-based immunotherapy.

Cancer testis antigens in newly diagnosed and relapse multiple myeloma: prognostic markers and potential targets for immunotherapy

BACKGROUND

In multiple myeloma, expression of cancer testis antigens may provide prognostic markers and potential targets for immunotherapy. Expression at relapse has not yet been evaluated for a large panel of cancer testis antigens which can be classified by varying expression in normal tissue: restricted to testis, expressed in testis and brain and not restricted but selectively expressed in testis.

DESIGN AND METHODS

Evaluation of cancer testis antigen expression was made in newly diagnosed multiple myeloma cases (HOVON-65/GMMG-HD4 trial; n = 320) and in relapse cases (APEX, SUMMIT, CREST trials; n = 264). Presence of expression using Affymetrix GeneChips was determined for 123 cancer testis antigens. Of these 87 had a frequency of more than 5% in the newly diagnosed and relapsed patients, and were evaluated in detail.

RESULTS

Tissue restriction was known for 58 out of 87 cancer testis antigens. A significantly lower frequency of presence calls in the relapsed compared to newly diagnosed cases was found for 3 out of 13 testis restricted genes, 2 out of 7 testis/brain restricted genes, and 17 out of 38 testis selective genes. MAGEC1, MAGEB2 and SSX1 were the most frequent testis-restricted cancer testis antigens in both data sets. Multivariate analysis demonstrated that presence of MAGEA6 and CDCA1 were clearly associated with shorter progression free survival, and presence of MAGEA9 with shorter overall survival in the set of newly diagnosed cases. In the set of relapse cases, presence of CTAG2 was associated with shorter progression free survival and presence of SSX1 with shorter overall survival.

CONCLUSIONS

Relapsed multiple myeloma reveals extensive cancer testis antigen expression. Cancer testis antigens are confirmed as useful prognostic markers in newly diagnosed multiple myeloma patients and in relapsed multiple myeloma patients. The HOVON-65/GMMG-HD4 trial is registered under Dutch trial register n. NTR-213. CREST, SUMMIT and APEX trials were registered under ns. M34100-024, M34100-025 and NCT00049478/NCT00048230, respectively.

Expression of a functional CCR2 receptor enhances tumor localization and tumor eradication by retargeted human T cells expressing a mesothelin-specific chimeric antibody receptor

PURPOSE

Adoptive T-cell immunotherapy with tumor infiltrating lymphocytes or genetically-modified T cells has yielded dramatic results in some cancers. However, T cells need to traffic properly into tumors to adequately exert therapeutic effects.

EXPERIMENTAL DESIGN

The chemokine CCL2 was highly secreted by malignant pleural mesotheliomas (MPM; a planned tumor target), but the corresponding chemokine receptor (CCR2) was minimally expressed on activated human T cells transduced with a chimeric antibody receptor (CAR) directed to the MPM tumor antigen mesothelin (mesoCAR T cells). The chemokine receptor CCR2b was thus transduced into mesoCAR T cells using a lentiviral vector, and the modified T cells were used to treat established mesothelin-expressing tumors.

RESULTS

CCR2b transduction led to CCL2-induced calcium flux and increased transmigration, as well as augmentation of in vitro T-cell killing ability. A single intravenous injection of 20 million mesoCAR + CCR2b T cells into immunodeficient mice bearing large, established tumors (without any adjunct therapy) resulted in a 12.5-fold increase in T-cell tumor infiltration by day 5 compared with mesoCAR T cells. This was associated with significantly increased antitumor activity.

CONCLUSIONS

CAR T cells bearing a functional chemokine receptor can overcome the inadequate tumor localization that limits conventional CAR targeting strategies and can significantly improve antitumor efficacy in vivo.

Towards effective immunotherapy of myeloma: enhanced elimination of myeloma cells by combination of lenalidomide with the human CD38 monoclonal antibody daratumumab

BACKGROUND

In our efforts to develop novel effective treatment regimens for multiple myeloma we evaluated the potential benefits of combining the immunomodulatory drug lenalidomide with daratumumab. Daratumumab is a novel human CD38 monoclonal antibody which kills CD38+ multiple myeloma cells via antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity and apoptosis.

DESIGN AND METHODS

To explore the effect of lenalidomide combined with daratumumab, we first carried out standard antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity assays in which the CD38+ multiple myeloma cell line UM-9 and primary multiple myeloma cells isolated from patients were used as target cells. We also tested the effect of lenalidomide on daratumumab-dependent cell-mediated-cytotoxicity and complement-dependent cytotoxicity of multiple myeloma cells directly in the bone marrow mononuclear cells of multiple myeloma patients. Finally, we determined the daratumumab-dependent cell-mediated cytotoxicity using peripheral blood mononuclear cells of multiple myeloma patients receiving lenalidomide treatment.

RESULTS

Daratumumab-dependent cell-mediated cytotoxicity of purified primary multiple myeloma cells, as well as of the UM-9 cell line, was significantly augmented by lenalidomide pre-treatment of the effector cells derived from peripheral blood mononuclear cells from healthy individuals. More importantly, we demonstrated a clear synergy between lenalidomide and daratumumab-induced antibody-dependent cell-mediated cytotoxicity directly in the bone marrow mononuclear cells of multiple myeloma patients, indicating that lenalidomide can also potentiate the daratumumab-dependent lysis of myeloma cells by activating the autologous effector cells within the natural environment of malignant cells. Finally, daratumumab-dependent cell-mediated cytotoxicity was significantly up-regulated in peripheral blood mononuclear cells derived from 3 multiple myeloma patients during lenalidomide treatment.

CONCLUSIONS

Our results indicate that powerful and complementary effects may be achieved by combining lenalidomide and daratumumab in the clinical management of multiple myeloma.

Eradication of medullary multiple myeloma by CD4+ cytotoxic human T lymphocytes directed at a single minor histocompatibility antigen

PURPOSE

The essential role of CD4(+) T cells as helpers of anticancer immunity is indisputable. Little is known, however, about their capacity to serve as effector cells in cancer treatment. Therefore, we explored the efficacy of immunotherapy with sole CD4(+) cytotoxic human T cells directed at a hematopoietic-restricted minor histocompatibility antigen (mHag).

EXPERIMENTAL DESIGN

In macrophage-depleted Rag2(-/-)γc(-/-) mice, which were also devoid of T, B, and natural killer cells, mHag-specific native T cells or tetanus toxoid (TT)-specific T cells transduced with the mHag-specific T-cell receptor (TCR) were injected to treat full-blown mHag(+) human multiple myeloma tumors.

RESULTS

mHag-specific antitumor responses were achieved after injection of native or mHag-TCR-transduced T cells. Although the therapy completely eradicated the primary tumors in the bone marrow, it failed to control extramedullary relapses, even after repeated T-cell injections. Detailed analyses ruled out mHag or MHC downregulation as mechanisms of extramedullary tumor escape. Impaired T-cell survival in vivo or defective homing to the tumor site were also ruled out as mechanisms behind extramedullary relapses, because injections of TT-loaded antigen presenting cells could facilitate homing of long-term surviving T cells to s.c. tumor sites. Moreover, intratumoral treatment of extramedullary tumors with 3AB11 was also ineffective.

CONCLUSIONS

Taken together, these results for the first time show the feasibility of immunotherapy of primary bone marrow tumors with sole CD4(+) human T cells directed to a tumor-associated mHag. Extramedullary relapses, probably due to microenvironment-dependent inhibitory mechanisms, remain a challenging issue towards effective cellular immunotherapy of hematologic malignancies.

Regulation of Treg functionality by acetylation-mediated Foxp3 protein stabilization

Regulatory T cells (Tregs) are a specific subset of lymphocytes that are critical for the maintenance of self-tolerance. Expression levels of the transcription factor Foxp3 have been causally associated with Treg differentiation and function. Recent studies show that Foxp3 can also be transiently expressed in effector T cells; however, stable Foxp3 expression is required for development of a functional Treg suppressor phenotype. Here, we demonstrate that Foxp3 is acetylated, and this can be reciprocally regulated by the histone acetyltransferase p300 and the histone deacetylase SIRT1. Hyperacetylation of Foxp3 prevented polyubiquitination and proteasomal degradation, therefore dramatically increasing stable Foxp3 protein levels. Moreover, using mouse splenocytes, human peripheral blood mononuclear cells, T cell clones, and skin-derived T cells, we demonstrate that treatment with histone deacetylase inhibitors resulted in significantly increased numbers of functional Treg cells. Taken together, our data demonstrate that modulation of the acetylation state of Foxp3 provides a novel molecular mechanism for assuring rapid temporal control of Foxp3 levels in T cells, thereby regulating Treg numbers and functionality. Manipulating Foxp3 acetylation levels could therefore provide a new therapeutic strategy to control inappropriate (auto)immune responses.

Correlation of high-resolution X-ray micro-computed tomography with bioluminescence imaging of multiple myeloma growth in a xenograft mouse model

Multiple myeloma (MM) is an incurable B-cell neoplasia in which progressive skeletal lesions are a characteristic feature. Earlier we established an animal model for human MM in the immune-deficient RAG2(-/-)gammac(-/-) mouse, in which the growth of luciferase-transduced MM cells was visualized using noninvasive bioluminescence imaging (BLI). This model appeared well suited to study disease progression and response to therapy by identifying the location of various foci of MM tumor growth scattered throughout the skeleton and at subsequent time points the quantitative assessment of the tumor load by using BLI. We report here on the corresponding high-resolution X-ray micro-computed tomographic (micro-CT) analysis to study skeletal defects in the mice with full-blown MM. Several anatomical derangements were observed, including abnormalities in geometry and morphology, asymmetrical bone structures, decreased overall density in the remaining bone, loss of trabecular bone mass, destruction of the inner microarchitecture, as well as cortical perforations. Using the combination of BLI, micro-CT imaging, and immune-histopathological techniques, we found a high correlation between the micro-CT-identified lesions, exact tumor location, and infiltration leading to structural lesions and local bone deformation. This confirms that this animal model strongly resembles human MM and has the potential for studying the biology of MM growth and for preclinical testing of novel therapies for MM and for repair of MM-induced bone lesions.

Immunotherapy in acute leukemia

Recent advances in immunotherapy of cancer may represent a successful example in translational research, in which progress in knowledge and technology in immunology has led to new strategies of immunotherapy, and even past failures in many clinical trials have led to a better understanding of basic cancer immunobiology. This article reviews the latest concepts in antitumor immunology and its application in the treatment of cancer, with particular focus on acute leukemia.

Toward targeting B cell cancers with CD4+ CTLs: identification of a CD19-encoded minor histocompatibility antigen using a novel genome-wide analysis

Some minor histocompatibility antigens (mHags) are expressed exclusively on patient hematopoietic and malignant cells, and this unique set of antigens enables specific targeting of hematological malignancies after human histocompatability leucocyte antigen (HLA)-matched allogeneic stem cell transplantation (allo-SCT). We report the first hematopoietic mHag presented by HLA class II (HLA-DQA1*05/B1*02) molecules to CD4(+) T cells. This antigen is encoded by a single-nucleotide polymorphism (SNP) in the B cell lineage-specific CD19 gene, which is an important target antigen for immunotherapy of most B cell malignancies. The CD19(L)-encoded antigen was identified using a novel and powerful genetic strategy in which zygosity-genotype correlation scanning was used as the key step for fine mapping the genetic locus defined by pairwise linkage analysis. This strategy was also applicable for genome-wide identification of a wide range of mHags. CD19(L)-specific CD4(+) T cells provided antigen-specific help for maturation of dendritic cells and for expansion of CD8(+) mHag-specific T cells. They also lysed CD19(L)-positive malignant cells, illustrating the potential therapeutic advantages of targeting this novel CD19(L)-derived HLA class II-restricted mHag. The currently available immunotherapy strategies enable the exploitation of these therapeutic effects within and beyond allo-SCT settings.

Cytotoxic human CD4(+) T cells

The induction of adaptive immune responses critically depends on helper signals provided by CD4(+) T cells. These signals not only license antigen presenting cells (APC) to activate naïve CD8(+) T cells leading to the formation of vast numbers of cytotoxic T lymphocytes but also support the differentiation of B cells into immunoglobulin-secreting plasma cells. Next to these helper functions, a subpopulation of CD4(+) T cells can also directly function as effector cells by executing cytotoxicity in a peptide-specific and MHC class II-restricted manner. Cytotoxic CD4(+) T cells may function in combating pathogens but additionally their presence has been associated with autoimmune disease and vascular damage. On the contrary, the induction of cytotoxic CD4(+) T cells may be a future target for vaccine strategies.

Adoptive cellular immunotherapy for childhood malignancies

Clinical trials have established that T cells have the ability to prevent and treat pathogens and tumors. This is perhaps best exemplified by engraftment of allogeneic T cells in the context of hematopoietic stem-cell transplantation (HSCT), which for over the last 50 years remains one of the best and most robust examples of cell-based therapies for the treatment of hematologic malignancies. Yet, the approach to infuse T cells for treatment of cancer, in general, and pediatric tumors, in particular, generally remains on the sidelines of cancer therapy. This review outlines the current state-of-the-art and provides a rationale for undertaking adoptive immunotherapy trials with emphasis on childhood malignancies.