WT1-specific T cell receptor gene therapy: improving TCR function in transduced T cells

Combining CRISPR-Cas9 and TCR exchange to generate a safe and efficient cord blood-derived T cell product for pediatric relapsed AML

BACKGROUND

Hematopoietic cell transplantation (HCT) is an effective treatment for pediatric patients with high-risk, refractory, or relapsed acute myeloid leukemia (AML). However, a large proportion of transplanted patients eventually die due to relapse. To improve overall survival, we propose a combined strategy based on cord blood (CB)-HCT with the application of AML-specific T cell receptor (TCR)-engineered T cell therapy derived from the same CB graft.

METHODS

We produced CB-CD8+ T cells expressing a recombinant TCR (rTCR) against Wilms tumor 1 (WT1) while lacking endogenous TCR (eTCR) expression to avoid mispairing and competition. CRISPR-Cas9 multiplexing was used to target the constant region of the endogenous TCRα (TRAC) and TCRβ (TRBC) chains. Next, an optimized method for lentiviral transduction was used to introduce recombinant WT1-TCR. The cytotoxic and migration capacity of the product was evaluated in coculture assays for both cell lines and primary pediatric AML blasts.

RESULTS

The gene editing and transduction procedures achieved high efficiency, with up to 95% of cells lacking eTCR and over 70% of T cells expressing rWT1-TCR. WT1-TCR-engineered T cells lacking the expression of their eTCR (eTCR-/- WT1-TCR) showed increased cell surface expression of the rTCR and production of cytotoxic cytokines, such as granzyme A and B, perforin, interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα), on antigen recognition when compared with WT1-TCR-engineered T cells still expressing their eTCR (eTCR+/+ WT1-TCR). CRISPR-Cas9 editing did not affect immunophenotypic characteristics or T cell activation and did not induce increased expression of inhibitory molecules. eTCR-/- WT1-TCR CD8+ CB-T cells showed effective migratory and killing capacity in cocultures with neoplastic cell lines and primary AML blasts, but did not show toxicity toward healthy cells.

CONCLUSIONS

In summary, we show the feasibility of developing a potent CB-derived CD8+ T cell product targeting WT1, providing an option for post-transplant allogeneic immune cell therapy or as an off-the-shelf product, to prevent relapse and improve the clinical outcome of children with AML.

Lymph Node-Targeted Vaccine Boosting of TCR T-cell Therapy Enhances Antitumor Function and Eradicates Solid Tumors

T-cell receptor (TCR)-modified T-cell therapies have shown promise against solid tumors, but overall therapeutic benefits have been modest due in part to suboptimal T-cell persistence and activation in vivo, alongside potential tumor antigen escape. In this study, we demonstrate an approach to enhance the in vivo persistence and function of TCR T cells through combination with Amphiphile (AMP) vaccination including cognate TCR T peptides. AMP modification improves lymph node targeting of conjugated tumor immunogens and adjuvants, thereby coordinating a robust T cell-activating endogenous immune response. AMP vaccine combination with TCR T-cell therapy led to complete eradication and durable responses against established murine solid tumors refractory to TCR T-cell monotherapy. Enhanced antitumor efficacy was correlated with simultaneous in vivo invigoration of adoptively transferred TCR T cells and in situ expansion of the endogenous antitumor T-cell repertoire. Long-term protection against tumor recurrence in AMP-vaccinated mice was associated with antigen spreading to additional tumor-associated antigens not targeted by vaccination. AMP vaccination further correlated with pro-inflammatory lymph node transcriptional reprogramming and increased antigen presenting-cell maturation, resulting in TCR T-cell expansion and functional enhancement in lymph nodes and solid tumor parenchyma without lymphodepletion. In vitro evaluation of AMP peptides with matched human TCR T cells targeting NY-ESO-1, mutant KRAS, and HPV16 E7 illustrated the clinical potential of AMP vaccination to enhance human TCR T-cell proliferation, activation, and antitumor activity. Taken together, these studies provide rationale and evidence to support clinical evaluation of combining AMP vaccination with TCR T-cell therapies to augment antitumor activity.

Antigen-Specific TCR-T Cells for Acute Myeloid Leukemia: State of the Art and Challenges

The cytogenetic abnormalities and molecular mutations involved in acute myeloid leukemia (AML) lead to unique treatment challenges. Although adoptive T-cell therapies (ACT) such as chimeric antigen receptor (CAR) T-cell therapy have shown promising results in the treatment of leukemias, especially B-cell malignancies, the optimal target surface antigen has yet to be discovered for AML. Alternatively, T-cell receptor (TCR)-redirected T cells can target intracellular antigens presented by HLA molecules, allowing the exploration of a broader territory of new therapeutic targets. Immunotherapy using adoptive transfer of WT1 antigen-specific TCR-T cells, for example, has had positive clinical successes in patients with AML. Nevertheless, AML can escape from immune system elimination by producing immunosuppressive factors or releasing several cytokines. This review presents recent advances of antigen-specific TCR-T cells in treating AML and discusses their challenges and future directions in clinical applications.

Integrative genomic analysis of a novel small nucleolar RNAs prognostic signature in patients with acute myelocytic leukemia

This study mainly used The Cancer Genome Atlas (TCGA) RNA sequencing dataset to screen prognostic snoRNAs of acute myeloid leukemia (AML), and used for the construction of prognostic snoRNAs signature for AML. A total of 130 AML patients with RNA sequencing dataset were used for prognostic snoRNAs screenning. SnoRNAs co-expressed genes and differentially expressed genes (DEGs) were used for functional annotation, as well as gene set enrichment analysis (GSEA). Connectivity Map (CMap) also used for potential targeted drugs screening. Through genome-wide screening, we identified 30 snoRNAs that were significantly associated with the prognosis of AML. Then we used the step function to screen a prognostic signature composed of 14 snoRNAs (SNORD72, SNORD38, U3, SNORA73B, SNORD79, SNORA73, SNORD12B, SNORA74, SNORD116-12, SNORA65, SNORA14, snoU13, SNORA75, SNORA31), which can significantly divide AML patients into high- and low-risk groups. Through GSEA, snoRNAs co-expressed genes and DEGs functional enrichment analysis, we screened a large number of potential functional mechanisms of this prognostic signature in AML, such as phosphatidylinositol 3-kinase-Akt, Wnt, epithelial to mesenchymal transition, T cell receptors, NF-kappa B, mTOR and other classic cancer-related signaling pathways. In the subsequent targeted drug screening using CMap, we also identified six drugs that can be used for AML targeted therapy, they were alimemazine, MG-262, fluoxetine, quipazine, naltrexone and oxybenzone. In conclusion, our current study was constructed an AML prognostic signature based on the 14 prognostic snoRNAs, which may serve as a novel prognostic biomarker for AML.

Expression Levels of the CA9, WT1, and PRAME Genes and Genotyping-Associated Antigens for the Diagnosis and Prognosis of Colorectal Cancer

Background Colorectal cancer (CRC) is the third most prevalent type of cancer worldwide, and is one of the major health problems in Asia, Africa, Europe, and America. The tumor antigens recently are of interesting indicators as diagnostic and prognostic tools. The aim of the present study is to detect the expression levels of carbonic anhydrase IX (CA9), the Wilms tumor gene (WT1), and the preferentially expressed antigen in melanoma (PRAME) in the peripheral blood of CRC patients in comparison with healthy controls.

Methods A prospective case-control study of CRC patients was conducted. We included 25 newly-diagnosed CRC eligible patients and obtained peripheral blood samples of them as well as 10 blood samples from the control group. All samples were then submitted to deoxyribonucleic acid (DNA) extraction and a molecular study through real-time polymerase chain reaction (PCR).

Results The CRC group consisted of 15 (60%) female and 10 (40%) male patients with a mean age of 50.52 ± 9.8 years, while the control group included 4 (40%) female and 6 (60%) male patients with a mean age of 47.7 ± 7.9 years. The CRC group, 24 (96%) of patient samples were CA9-positive with strong statistically significant differences (p < 0.00001; sensitivity: 96%; specificity: 90%). Regarding the WT1 gene, there were 11 (44%) positive samples in the CRC group, with no statistically significant differences (p = 0.055; sensitivity: 44%; specificity: 90%). The PRAME gene was positive in 9 (36%) samples in the CRC group, with no statistically significant differences (p = 0.357; sensitivity: 36%; specificity: 80%. Among CA9 (24 patients; 96%) of patients with CRC expressed positive results, in WT1 11(91.6%) CRC patients expressed gene, and in PRAME gene, 9 patients with CRC (81.8%) expressed positive results.

Conclusion Overexpression of the CA9 gene in CRC of high sensitivity and specificity to be used as a tool to discriminate CRC from benign associate with high accuracy compare to WT1 and PRAME genes.

Immunotherapy Advances for Epithelial Ovarian Cancer

Simple Summary

The overall five-year survival rate in epithelial ovarian cancer is 44% and has only marginally improved in the past two decades. Despite an initial response to standard treatment consisting of chemotherapy and surgical removal of tumor, the lesions invariably recur, and patients ultimately die of chemotherapy resistant disease. New treatment modalities are needed in order to improve the prognosis of women diagnosed with ovarian cancer. One such modality is immunotherapy, which aims to boost the capacity of the patient’s immune system to recognize and attack the tumor cells. We performed a retrospective study to identify some of the most promising immune therapies for epithelial ovarian cancer. Special emphasis was given to immuno-oncology clinical trials.

Abstract

New treatment modalities are needed in order to improve the prognosis of women diagnosed with epithelial ovarian cancer (EOC), the most aggressive gynecologic cancer type. Most ovarian tumors are infiltrated by immune effector cells, providing the rationale for targeted approaches that boost the existing or trigger new anti-tumor immune mechanisms. The field of immuno-oncology has experienced remarkable progress in recent years, although the results seen with single agent immunotherapies in several categories of solid tumors have yet to extend to ovarian cancer. The challenge remains to determine what treatment combinations are most suitable for this disease and which patients are likely to benefit and to identify how immunotherapy should be incorporated into EOC standard of care. We review here some of the most promising immune therapies for EOC and focus on those currently tested in clinical trials.

MMP-7 derived peptides with MHC class-I binding motifs from canine mammary tumor tissue elicit strong antigen-specific T-cell responses in BALB/c mice

Matrix Metalloproteinases (MMPs)-induced altered proteolysis of extracellular matrix proteins and basement membrane holds the key for tumor progression and metastasis. Matrix metalloproteinases-7 (Matrilysin), the smallest member of the MMP family also performs quite alike; thus serves as a potential candidate for anti-tumor immunotherapy. Conversely, being an endogenous tumor-associated antigen (TAA), targeting MMP-7 for immunization is challenging. But MMP-7-based xenovaccine can surmount the obstacle of poor immunogenicity and immunological tolerance, often encountered in TAA-based conventional vaccine for anti-tumor immunotherapy. This paves the way for investigating the potential of MMP-7-derived major histocompatibility complex (MHC)-binding peptides to elicit precise epitope-specific T-cell responses towards their possible inclusion in anti-tumor vaccine formulations. Perhaps it also ushers the path of achieving multiple epitope-based broad and universal cellular immunity. In current experiment, an immunoinformatics approach has been employed to identify the putative canine matrix matelloproteinases-7 (cMMP-7)-derived peptides with MHC class-I-binding motifs which can elicit potent antigen-specific immune responses in BALB/c mice. Immunization with the cMMP-7 DNA vaccine induced a strong CD8⁺ cytotoxic T lymphocytes (CTLs) and Th1- type response, with high level of gamma interferon (IFN-γ) production in BALB/c mice. The two identified putative MHC-I-binding nonameric peptides (Peptide_32-40 and Peptide_175-183) from cMMP-7 induced significant lymphocyte proliferation along with the production of IFN-γ from CD8⁺ T-cells in mice immunized with cMMP-7 DNA vaccine. The current observation has depicted the immunogenic potential of the two cMMP-7-derived nonapeptides for their possible exploitation in xenovaccine-mediated anti-tumor immunotherapy in mouse model.

Optimization of T-cell Receptor-Modified T Cells for Cancer Therapy

T-cell receptor (TCR)-modified T-cell gene therapy can target a variety of extracellular and intracellular tumor-associated antigens, yet has had little clinical success. A potential explanation for limited antitumor efficacy is a lack of T-cell activation in vivo We postulated that expression of proinflammatory cytokines in TCR-modified T cells would activate T cells and enhance antitumor efficacy. We demonstrate that expression of interleukin 18 (IL18) in tumor-directed TCR-modified T cells provides a superior proinflammatory signal than expression of interleukin 12 (IL12). Tumor-targeted T cells secreting IL18 promote persistent and functional effector T cells and a proinflammatory tumor microenvironment. Together, these effects augmented overall survival of mice in the pmel-1 syngeneic tumor model. When combined with sublethal irradiation, IL18-secreting pmel-1 T cells were able to eradicate tumors, whereas IL12-secreting pmel-1 T cells caused toxicity in mice through excessive cytokine secretion. In another xenograft tumor model, IL18 secretion enhanced the persistence and antitumor efficacy of NY-ESO-1-reactive TCR-modified human T cells as well as overall survival of tumor-bearing mice. These results demonstrate a rationale for optimizing the efficacy of TCR-modified T-cell cancer therapy through expression of IL18.See related commentary by Wijewarnasuriya et al., p. 732.

Emerging CRISPR/Cas9 applications for T-cell gene editing

Gene editing tools are being rapidly developed, accelerating many areas of cell and gene therapy research. Each successive gene editing technology promises increased efficacy, improved specificity, reduced manufacturing cost and design complexity; all of which are currently epitomised by the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (Cas9) platform. Since its conceptualisation, CRISPR-based gene editing has been applied to existing methodologies and has further allowed the exploration of novel avenues of research. Implementation of CRISPR/Cas9 has been instrumental to recent progress in the treatment of cancer, primary immunodeficiency, and infectious diseases. To this end, T-cell therapies have attempted to harness and redirect antigen recognition function, and through gene editing, broaden T-cell targeting capabilities and enhance their potency. The purpose of this review is to provide insights into emerging applications of CRISPR/Cas9 in T-cell therapies, to briefly address concerns surrounding CRISPR-mediated indel formation, and to introduce CRISPR/Cas9 base editing technologies that hold vast potential for future research and clinical translation.

T cell receptor-engineered T cells for leukemia immunotherapy

At present, refractory and relapse are major issues for leukemia therapy and a major cause of allogeneic hematopoietic stem cell transplant failure. Over the last decade, many studies have demonstrated that adoptive cancer antigen-specific T cell therapy is an effective option for leukemia therapy. Recently, T cell immunotherapy studies have mainly focused on chimeric antigen receptor- and T cell receptor-engineered T cells. Clinical trials involving chimeric antigen receptor-engineered T cells have been a major breakthrough and became a novel therapy for leukemia. As another potential therapy for leukemia, clinical application of TCR-engineered T cells remains in its infancy. This article presents a review of the current status of anti-leukemia immunotherapy using leukemia antigen-specific TCR-engineered T cells.

WT1 peptide vaccine in Montanide in contrast to poly ICLC, is able to induce WT1-specific immune response with TCR clonal enrichment in myeloid leukemia

Background

The optimal strategy for vaccination to induce CD8⁺ T cell responses against WT1 is not known.

Methods

A pilot randomized study in HLA-A02⁺ patients to receive vaccination with WT1 in Montanide or in poly ICLC, a TLR3 agonist, to explore the novel immune adjuvant was conducted. Seven patients were randomized. Four patients received WT1 in Montanide, and three with WT1 in poly ICLC. Five patients were in morphologic remission and two had residual morphologic disease at the study entry.

Results

All patients finished the induction phase without any major toxicity except mild transient local injection reaction. One patient on the Montanide arm developed aseptic ulceration at two vaccine sites which healed without antibiotics. Three of 4 patients on the Montanide arm had a decreased expression of WT1 after WT1 vaccination, and two of them demonstrated generation of WT1-specific cytotoxic CD8⁺ T cell responses with biased TCR beta chain enrichment. In contrast, no obvious WT1-specific immune responses were detected in two patients on the poly ICLC arm, nor was there clonal enrichment by TCR alpha/beta sequencing; however, these patients did also have decreased WT1 expression and remained in remission several years after the initiation of treatment.

Conclusions

WT1 peptide vaccine with Montanide as an adjuvant induces detectable WT1-specific CD8⁺ T cell responses with clonal TCR enrichment, which may be capable of controlling leukemia recurrence in the setting of minimal residual disease. Poly ICLC may induce anti-leukemic activity in the absence of detectable WT1 specific CD8⁺ T cell responses.

Trial registration NCT01842139, 7/3/2012 retrospectively registered; https://clinicaltrials.gov/ct2/show/NCT01842139.

Advances in immunotherapy for pediatric acute myeloid leukemia

INTRODUCTION

Achieving better disease control in patients diagnosed with acute myeloid leukemia (AML) has proven challenging. Overall survival has been impacted by addressing treatment related mortality with focused supportive care measures. Despite this improvement, it remains difficult to induce durable leukemia remissions despite aggressive chemotherapeutic regimens. The addition of hematopoietic stem cell transplants (HSCT) has allowed further treatment intensification and provided the benefit of graft-versus-leukemia (GVL) effect. However, HSCT carries the risk of transplant related morbidities, particularly GVHD, and anti-tumor responsiveness is still suboptimal. Thus, there is a need for alternate therapies. Immunotherapy has the potential to address this need. Areas covered: Expert opinion: The elusiveness of an ideal surface antigen target together with an immunosuppressive leukemic microenvironment add to the already difficult challenge in developing AML-targeted immunotherapies. Though many hurdles remain, recent translational discovery and progressive clinical advances anticipate exciting future developments.

AREAS COVERED

This review highlights promises and challenges to immune-based therapies for AML. It aims to summarize immunotherapeutic strategies trialed in AML patients to date, inclusive of: antibodies, vaccines, and cellular therapy. It emphasizes those being used in the pediatric population, but also includes adult clinical trials and translational science that may ultimately extend to pediatric patients.

Graft-versus-Leukemia Effect Following Hematopoietic Stem Cell Transplantation for Leukemia

The success of hematopoietic stem cell transplantation (HSCT) lies with the ability of the engrafting immune system to remove residual leukemia cells via a graft-versus-leukemia effect (GvL), caused either spontaneously post-HSCT or via donor lymphocyte infusion. GvL effects can also be initiated by allogenic mismatched natural killer cells, antigen-specific T cells, and activated dendritic cells of leukemic origin. The history and further application of this GvL effect and the main mechanisms will be discussed and reviewed in this chapter.

Enumeration of WT1-specific CD8+ T cells for clinical application using an MHC Streptamer based no-wash single-platform flow-cytometric assay

The advent of novel strategies to generate leukemia-associated-antigen (LAA)-specific T cells for adoptive immunotherapies creates a demand for standardized good laboratory practice (GLP)-compliant enumeration assays to provide a secure clinical environment-whether it is to identify potential donors, define therapeutic doses for transplantation, or monitor clinical success. Here, we introduce a no-wash assay based on single-platform cell enumeration and Streptamer staining to determine the Wilms' tumor antigen 1 (WT1)-specific T cell immunity in clinical samples. We analyzed the performance of the WT1-specific MHC Streptamers in direct comparison to CMV- and EBV-specific MHC Streptamer staining by spiking antigen-specific T cells in PBMCs. The accuracy of the assay was high for all performed experiments with a mean recovery of 94% and a linear regression of 0.988. Differences were apparent regarding the limit of detection/quantification (LOD/LOQ). While results obtained for WT1 yielded an LOD/LOQ of 0.08 ± 0.04% and 0.11 ± 0.06% (1.33 ± 0.32 cells/µl and 1.9 ± 0.14 cells/µl), the overall LOD/LOQ was notably lower and accounted to 0.02 ± 0.02% and 0.05 ± 0.03% (0.60 ± 0.03 cells/µl and 1.27 ± 0.58 cells/µl). Subsequent screening of 22 healthy individuals revealed significantly higher values for WT1 (0.04 ± 0.02% and 1.5 ± 0.9 cells/µl) than for the irrelevant HIV pol (0.016 ± 0.01% and 0.5 ± 0.4 cells/µl). In contrast, no increased frequencies were observed for WT1-specific T cells compared to HIV-specific T cells using a classical wash-protocol. These findings strongly suggest the use of no-wash single-platform assays in combination with MHC Streptamer staining for the detection of low affinity LAA-specific T cells due to its high accuracy and sensitivity. © 2017 International Society for Advancement of Cytometry.

The Role of the Immune System in Ovarian Cancer and Implications on Therapy

Ovarian cancer is the leading cause of death from gynecologic malignancy in the United States. While the treatment options have improved with conventional cytotoxic chemotherapy and advanced surgical techniques, disease recurrence is common and fatal in nearly all cases. Current evidence suggests that the immune system and its ability to recognize and eliminate microscopic disease is paramount in preventing recurrence. The goal of immunotherapy is to balance the activation of the immune system against cancer while preventing the potential for tremendous toxicity elicited by immune modulation. In this paper we will review the role of immune system in disease pathogenesis and different immunotherapies available for the treatment of ovarian cancer as well as current ongoing studies and potential future directions.

Directed T-cell therapies for leukemia and lymphoma after hematopoietic stem cell transplant: beyond chimeric antigen receptors

This review focuses on the recent advances utilizing adoptive T-cell immunotherapies for patients after hematopoietic stem cell transplant using T cells after autologous transplant to treat the highest risk patients. The particular emphasis is the use of T cells to treat leukemias and lymphomas with gene transfer and nongene transfer approaches to direct specificity to tumor associated antigens. In this review, we will highlight how these novel therapeutics can be successfully used to prevent or treat high-risk patients who relapse after hematopoietic stem cell transplant.

Past, present and future targets for immunotherapy in ovarian cancer

Ovarian cancer is the leading cause of death from gynecologic malignancy in the US. Treatments have improved with conventional cytotoxic chemotherapy and advanced surgical techniques but disease recurrence is common and fatal in nearly all cases. Current evidence suggests that the immune system and its ability to recognize and eliminate microscopic disease is paramount in preventing recurrence. Ovarian cancer immunotherapy is targeting tumors through active, passive and adoptive approaches. The goal of immunotherapy is to balance the activation of the immune system against cancer while preventing the potential for tremendous toxicity elicited by immune modulation. In this paper we will review the different immunotherapies available for ovarian cancer as well as current ongoing studies and potential future directions.

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

SUMMARY 

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

Immunotherapy in acute myeloid leukemia

Treatment of acute myeloid leukemia (AML) with current chemotherapy regimens is still disappointing, with overall survival rates of ≤40% at 5 years. It is now well established that AML cells can evade the immune system through multiple mechanisms, including the expression of the enzyme indoleamine 2,3 dioxygenase. Immunotherapeutic strategies, including both active, such as vaccination with leukemia-associated antigens, and passive, such as adoptive transfer of allogeneic natural killer cells, may overcome leukemia escape and lead to improved cure. Allogeneic hemopoeitic stem cell transplantation, the most effective treatment of AML, is the best known model of immunotherapy. Following transplant, recipient AML cells are eradicated by donor immune cells through the graft-versus-leukemia (GVL) effect. However, GVL is clinically associated with graft-versus-host disease, the major cause of mortality after transplant. GVL is mediated by donor T cells recognizing either leukemia-associated antigens or minor as well as major histocompatibility antigens. Several innovative strategies have been devised to generate leukemia reactive T cells so as to increase GVL responses with no or little graft-versus-host disease.

Highlights of the third International Conference on Immunotherapy in Pediatric Oncology

The third International Conference on Immunotherapy in Pediatric Oncology was held in Frankfurt/Main, Germany, October 1-2, 2012. Major topics of the conference included (i) cellular therapies using antigen-specific and gene-modified T cells for targeting leukemia and pediatric solid tumors; (ii) overcoming hurdles and barriers with regard to immunogenicity, immune escape, and the role of tumor microenvironment; (iii) vaccine strategies and antigen presentation; (iv) haploidentical transplantation and innate immunity; (v) the role of immune cells in allogeneic transplantation; and (vi) current antibody/immunoconjugate approaches for the treatment of pediatric malignancies. During the past decade, major advances have been made in improving the efficacy of these modalities and regulatory hurdles have been taken. Nevertheless, there is still a long way to go to fully exploit the potential of immunotherapeutic strategies to improve the cure of children and adolescents with malignancies. This and future meetings will support new collaborations and insights for further translational and clinical immunotherapy studies.

Tumor-associated antigens in breast cancer

The targets for the immune system are antigens present on cancer cells; however, many are not cancer-specific and may also be found on normal tissues. These antigens are often products of mutated cellular genes, aberrantly expressed normal genes, or genes encoding viral proteins. Vaccines constitute an active and specific immunotherapy designed to stimulate the intrinsic antitumor immune response by presenting tumor-associated antigens expressed on normal tissues that are overexpressed on tumor cells.

BAALC and WT1 expressions from diagnosis to hematopoietic stem cell transplantation: consecutive monitoring in adult patients with core-binding-factor-positive AML

No consecutive analysis of BAALC and WT1 expressions associated with core-binding factor AML (CBF-AML) from diagnosis to hematopoietic stem cell transplantation (HSCT) has yet been reported. We investigated BAALC and WT1 expressions using a method of real-time quantitative polymerase chain reaction (RQ-PCR) at diagnosis, after induction chemotherapy, at pre-HSCT, and at post-HSCT period in 45 consecutive patients [t(8,21) (n = 28), inv(16) (n = 17)], who received HSCT as a post-remission treatment. BAALC and WT1 RQ-PCR decrement ratio (DR) was also calculated at post-induction chemotherapy, at pre-HSCT, and at post-HSCT compared with the diagnostic level. Higher BAALC expression at diagnosis showed significantly inferior OS (P = 0.031), EFS (P = 0.011), and higher CIR (P = 0.002) rates. At post-HSCT, both higher BAALC and WT1 expressions showed significantly inferior OS (P = 0.005, 0.016), EFS (P = 0.002, 0.006), and higher CIR (P = 0.001, 0.003) rates. A subgroup of t(8;21) showing higher BAALC and WT1 expressions at post-HSCT were also associated with inferior OS (P = 0.018, 0.015) and higher CIR rates (P = 0.019, 0.011). While BAALC DR showed no significant results on outcomes, WT1 DR more than 2-log at post-HSCT showed significantly lower CIR rate (P = 0.028). This study showed that higher post-HSCT BAALC and WT1 expressions in patients with CBF-AML may be good markers of minimal residual disease for the prediction of survival and relapse after HSCT.

Novel cellular therapies for leukemia: CAR-modified T cells targeted to the CD19 antigen

The ability of immune-competent donor T cells to mediate a beneficial graft-versus-leukemia (GVL) effect was first identified in the setting of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematologic malignancies. Unfortunately, with the exception of chronic myelogenous leukemia and EBV-induced lymphoproliferative disease, allo-HSCT GVL lacks the potency to significantly affect disease progression or recurrence in most other hematologic malignancies. The inadequacy of a GVL effect using past approaches is particularly evident in patients with lymphoid malignancies. However, with the advent of improved gene transfer technology, genetically modified tumor-specific immune effectors have extended cellular immunotherapy to lymphoid malignancies. One promising strategy entails the introduction of genes encoding artificial receptors called chimeric antigen receptors (CARs), which redirect the specificity and function of immune effectors. CAR-modified T cells targeted to the B cell-specific CD19 antigen have demonstrated promising results in multiple early clinical trials, supporting further investigation in patients with B-cell cancers. However, disparities in clinical trial design and CAR structure have complicated the discovery of the optimal application of this technology. Recent preclinical studies support additional genetic modifications of CAR-modified T cells to achieve optimal clinical efficacy using this novel adoptive cellular therapy.

Cord blood T cells retain early differentiation phenotype suitable for immunotherapy after TCR gene transfer to confer EBV specificity

Adoptive T cell therapy can be effective for Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease and melanoma. Transducing high-affinity TCR genes into T lymphocytes is an emerging method to improve potency and specificity of tumor-specific T cells. However, both methods necessitate in vitro lymphocyte proliferation, generating highly differentiated effector cells that display reduced survival and antitumor efficacy postinfusion. TCR-transduction of naive lymphocytes isolated from peripheral blood is reported to provide superior in vivo survival and function. We utilized cord blood (CB) lymphocytes, which comprise mainly naive cells, for transducing EBV-specific TCR. Comparable TCR expression was achieved in adult and CB cells, but the latter expressed an earlier differentiation profile. Further antigen-driven stimulation skewed adult lymphocytes to a late differentiation phenotype associated with immune exhaustion. In contrast, CB T cells retained a less differentiated phenotype after antigen stimulation, remaining CD57-negative but were still capable of antigen-specific polyfunctional cytokine expression and cytotoxicity in response to EBV antigen. CB T cells also retained longer telomeres and in general possessed higher telomerase activity indicative of greater proliferative potential. CB lymphocytes therefore have qualities indicating prolonged survival and effector function favorable to immunotherapy, especially in settings where donor lymphocytes are unavailable such as in solid organ and CB transplantation.

New insights into antigen specific immunotherapy for chronic myeloid leukemia

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

Novel cellular therapies for leukemia: CAR-modified T cells targeted to the CD19 antigen

The ability of immune-competent donor T cells to mediate a beneficial graft-versus-leukemia (GVL) effect was first identified in the setting of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematologic malignancies. Unfortunately, with the exception of chronic myelogenous leukemia and EBV-induced lymphoproliferative disease, allo-HSCT GVL lacks the potency to significantly affect disease progression or recurrence in most other hematologic malignancies. The inadequacy of a GVL effect using past approaches is particularly evident in patients with lymphoid malignancies. However, with the advent of improved gene transfer technology, genetically modified tumor-specific immune effectors have extended cellular immunotherapy to lymphoid malignancies. One promising strategy entails the introduction of genes encoding artificial receptors called chimeric antigen receptors (CARs), which redirect the specificity and function of immune effectors. CAR-modified T cells targeted to the B cell–specific CD19 antigen have demonstrated promising results in multiple early clinical trials, supporting further investigation in patients with B-cell cancers. However, disparities in clinical trial design and CAR structure have complicated the discovery of the optimal application of this technology. Recent preclinical studies support additional genetic modifications of CAR-modified T cells to achieve optimal clinical efficacy using this novel adoptive cellular therapy.

Potential target antigens for a universal vaccine in epithelial ovarian cancer

The prognosis of epithelial ovarian cancer (EOC), the primary cause of death from gynaecological malignancies, has only modestly improved over the last decades. Immunotherapeutic treatment using a cocktail of antigens has been proposed as a "universal" vaccine strategy. We determined the expression of tumor antigens in the context of MHC class I expression in 270 primary tumor samples using tissue microarray. Expression of tumor antigens p53, SP17, survivin, WT1, and NY-ESO-1 was observed in 120 (48.0%), 173 (68.9%), 208 (90.0%), 129 (56.3%), and 27 (11.0%) of 270 tumor specimens, respectively. In 93.2% of EOC, at least one of the investigated tumor antigens was (over)expressed. Expression of MHC class I was observed in 78.1% of EOC. In 3 out 4 primary tumors, (over)expression of a tumor antigen combined with MHC class I was observed. These results indicate that a multiepitope vaccine, comprising these antigens, could serve as a universal therapeutic vaccine for the vast majority of ovarian cancer patients.

Combination of intensive chemotherapy and anticancer vaccines in the treatment of human malignancies: the hematological experience

In vitro studies have demonstrated that cancer-specific T cell cytotoxicity can be induced both ex vivo and in vivo, but this therapeutic strategy should probably be used as an integrated part of a cancer treatment regimen. Initial chemotherapy should be administered to reduce the cancer cell burden and disease-induced immune defects. This could be followed by autologous stem cell transplantation that is a safe procedure including both high-dose disease-directed chemotherapy and the possibility for ex vivo enrichment of the immunocompetent graft cells. The most intensive conventional chemotherapy and stem cell transplantation are used especially in the treatment of aggressive hematologic malignancies; both strategies induce T cell defects that may last for several months but cancer-specific T cell reactivity is maintained after both procedures. Enhancement of anticancer T cell cytotoxicity is possible but posttransplant vaccination therapy should probably be combined with optimalisation of immunoregulatory networks. Such combinatory regimens should be suitable for patients with aggressive hematological malignancies and probably also for other cancer patients.

Immunotherapy prospects for acute myeloid leukaemia

While chemotherapy is successful at inducing remission of acute myeloid leukaemia (AML), the disease has a high probability of relapse. Strategies to prevent relapse involve consolidation chemotherapy, stem cell transplantation and immunotherapy. Evidence for immunosurveillance of AML and susceptibility of leukaemia cells to both T cell and natural killer (NK) cell attack and justifies the application of immune strategies to control residual AML persisting after remission induction. Immune therapy for AML includes allogeneic stem cell transplantation, adoptive transfer of allogeneic or autologous T cells or NK cells, vaccination with leukaemia cells, dendritic cells, cell lysates, peptides and DNA vaccines and treatment with cytokines, antibodies and immunomodulatory agents. Here we describe what is known about the immunological features of AML at presentation and in remission, the current status of immunotherapy and strategies combining treatment approaches with a view to achieving leukaemia cure.

Real-time quantitative polymerase chain reaction detection of minimal residual disease by standardized WT1 assay to enhance risk stratification in acute myeloid leukemia: a European LeukemiaNet study

PURPOSE

Risk stratification in acute myeloid leukemia (AML) is currently based on pretreatment characteristics. It remains to be established whether relapse risk can be better predicted through assessment of minimal residual disease (MRD). One proposed marker is the Wilms tumor gene WT1, which is overexpressed in most patients with AML, thus providing a putative target for immunotherapy, although in the absence of a standardized assay, its utility for MRD monitoring remains controversial.

PATIENTS AND METHODS

Nine published and in-house real-time quantitative polymerase chain reaction WT1 assays were systematically evaluated within the European LeukemiaNet; the best-performing assay was applied to diagnostic AML samples (n = 620), follow-up samples from 129 patients treated with intensive combination chemotherapy, and 204 normal peripheral blood (PB) and bone marrow (BM) controls.

RESULTS

Considering relative levels of expression detected in normal PB and BM, WT1 was sufficiently overexpressed to discriminate > or = 2-log reduction in transcripts in 46% and 13% of AML patients, according to the respective follow-up sample source. In this informative group, greater WT1 transcript reduction after induction predicted reduced relapse risk (hazard ratio, 0.54 per log reduction; 95% CI, 0.36 to 0.83; P = .004) that remained significant when adjusted for age, WBC count, and cytogenetics. Failure to reduce WT1 transcripts below the threshold limits defined in normal controls by the end of consolidation also predicted increased relapse risk (P = .004).

CONCLUSION

Application of a standardized WT1 assay provides independent prognostic information in AML, lending support to incorporation of early assessment of MRD to develop more robust risk scores, to enhance risk stratification, and to identify patients who may benefit from allogeneic transplantation.

Immunotherapy of acute myeloid leukemia: current approaches

Following standard therapy that consists of chemotherapy with or without stem cell transplantation, both relapsed and refractory disease shorten the survival of acute myeloid leukemia (AML) patients. Therefore, additional treatment options are urgently needed, especially to fight residual AML cells. The identification of leukemia-associated antigens and the observation that administration of allogeneic T cells can mediate a graft-versus-leukemia effect paved the way to the development of active and passive immunotherapy strategies, respectively. The aim of these strategies is the eradication of AML cells by the immune system. In this review, an overview is provided of both active and passive immunotherapy strategies that are under investigation or in use for the treatment of AML. For each strategy, a critical view on the state of the art is given and future perspectives are discussed.

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.

WT1 peptide vaccine for the treatment of cancer

Wilms' tumor gene WT1 is expressed in various kinds of cancers. Human WT1-specific cytotoxic T lymphocytes (CTLs) were generated, and mice immunized with WT1 peptide rejected challenges by WT1-expressing cancer cells without auto-aggression to normal organs. Furthermore, WT1 antibodies and WT1-specific CTLs were detected in cancer patients, indicating that WT1 protein was immunogenic. These findings provided us with the rationale for cancer immunotherapy targeting WT1. Clinical trials of WT1 peptide vaccination for cancer patients were started, and WT1 vaccination-related immunological responses and clinical responses, including reduction of leukemic cells, reduction of M-protein amount in myeloma, and shrinkage of solid cancer, were observed. Valuable information about immune responses against tumor antigens can be obtained by the analysis of samples from the vaccinated patients, which should lead to further improvement of cancer vaccine.

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.