Adoptive T-cell therapy of B-cell malignancies: Conventional and physiological chimeric antigen receptors

CAR-T cell therapy: a game-changer in cancer treatment and beyond

In recent years, cancer has become one of the primary causes of mortality, approximately 10 million deaths worldwide each year. The most advanced, chimeric antigen receptor (CAR) T cell immunotherapy has turned out as a promising treatment for cancer. CAR-T cell therapy involves the genetic modification of T cells obtained from the patient's blood, and infusion back to the patients. CAR-T cell immunotherapy has led to a significant improvement in the remission rates of hematological cancers. CAR-T cell therapy presently limited to hematological cancers, there are ongoing efforts to develop additional CAR constructs such as bispecific CAR, tandem CAR, inhibitory CAR, combined antigens, CRISPR gene-editing, and nanoparticle delivery. With these advancements, CAR-T cell therapy holds promise concerning potential to improve upon traditional cancer treatments such as chemotherapy and radiation while reducing associated toxicities. This review covers recent advances and advantages of CAR-T cell immunotherapy.

Programmable and multi-targeted CARs: a new breakthrough in cancer CAR-T cell therapy

CAR-T cell therapy, as a novel immunotherapy approach, has indicated successful results in the treatment of hematological malignancies; however, distinct results have been achieved regarding solid tumors. Tumor immunosuppressive microenvironment has been identified as the most critical barrier in CAR-T cell therapy of solid tumors. Developing novel strategies to augment the safety and efficacy of CAR-T cells could be useful to overcome the solid tumor hurdles. Similar to other cancer treatments, CAR-T cell therapy can cause some side effects, which can disturb the healthy tissues. In the current review, we will discuss the practical breakthroughs in CAR-T cell therapy using the multi-targeted and programmable CARs instead of conventional types. These superior types of CAR-T cells have been developed to increase the function and safety of T cells in a controllable manner, which would diminish the incidence of relevant side effects. Moreover, we will describe the capability of these powerful CARs in targeting multiple tumor antigens, redirecting the CAR-T cells to specific target cells, incrementing the safety of CARs, and other advantages that lead to promising outcomes in cancer CAR-T cell therapy.

From mono- to bivalent: improving theranostic properties of target modules for redirection of UniCAR T cells against EGFR-expressing tumor cells in vitro and in vivo

CAR-modified T cells show impressive results in clinical trials. However, cytokine release syndrome and "on-target, off-tumor" reactions represent most concerning side effects. To improve the safety of CAR-T cell therapy, we established a switchable CAR platform termed UniCAR system consisting of two components: UniCAR-modified T cells and tumor-specific target modules (TM). For treatment of EGFR+ epithelial tumors, we recently described a monovalent nanobody-based α-EGFR TM, either expressed in bacteria or eukaryotic cells. In spite of the identical primary sequence the eukaryotic TM showed a reduced killing capability and affinity. Here we describe a novel bivalent α-EGFR-EGFR TM. As expected, the avidity of the bivalent TM is higher than that of its monovalent counterpart. Binding of neither the monovalent α-EGFR TM nor the bivalent α-EGFR-EGFR TM to EGFR effected the EGF-mediated signaling. While the monovalent α-EGFR TM could only mediate the killing of tumor cells expressing high levels of EGFR, the bivalent α-EGFR-EGFR TM could redirect UniCAR T cells to tumor cells expressing low levels of EGFR. According to PET experiments in vivo, the increased avidity of the bivalent α-EGFR-EGFR TM improves the enrichment at the tumor site and its use for PET imaging.

Current strategies to improve the safety of chimeric antigen receptor (CAR) modified T cells

Adoptive immunotherapy adopting chimeric antigen receptor (CAR) modified T cells has arisen attention as a hard-hitting therapy for numerous cancers. CARs are genetically engineered receptors that could stimulate tumor cytotoxicity once binding to the specific tumor epitopes. In spite of current noteworthy achievements in hematologic malignancies, the safety problems have aroused public awareness. In this review, we will focus on recent potential strategies to improve the security of CAR modified T cells.

Strategies to genetically engineer T cells for cancer immunotherapy

Immunotherapy is one of the most promising and innovative approaches to treat cancer, viral infections, and other immune-modulated diseases. Adoptive immunotherapy using gene-modified T cells is an exciting and rapidly evolving field. Exploiting knowledge of basic T cell biology and immune cell receptor function has fostered innovative approaches to modify immune cell function. Highly translatable clinical technologies have been developed to redirect T cell specificity by introducing designed receptors. The ability to engineer T cells to manifest desired phenotypes and functions is now a thrilling reality. In this review, we focus on outlining different varieties of genetically engineered T cells, their respective advantages and disadvantages as tools for immunotherapy, and their promise and drawbacks in the clinic.

Potential therapeutic strategy for gastric cancer peritoneal metastasis by NKG2D ligands-specific T cells

Purpose

Despite advancements in its treatment, gastric cancer continues to be one of the leading causes of cancer deaths worldwide. Adoptive transfer of chimeric antigen receptor-modified T cells is a promising antitumor therapy for many cancers. The purpose of this study was to construct a chimeric receptor linking the extracellular domain of NKG2D to the CD28 and CD3zeta chain intracellular domains to target gastric cancers that expressed NKG2D ligands.

Methods

Expression of NKG2D ligands including MICA, MICB, and ULBP1–3 in a gastric cancer cell line and primary gastric cancer cells from ascites samples were analyzed using flow cytometry. Co-culture experiments were performed by incubating chNKG2D T cells with gastric cancer cell lines and with primary human gastric cancer cells isolated from ascites and by measuring cytokine and chemokine release and cytotoxicity.

Results

Gastric cancer cell lines and ascites-derived primary human gastric cancer cells expressed high levels of MICA, MICB, and ULBP2. ChNKG2D T cells secreted proinflammatory cytokines and chemokines when cultured with these cancer cells. In addition, chNKG2D T cells lysed gastric cancer cell lines and the ascites-derived primary human gastric cancer cells.

Conclusion

These data indicate that treatment with chNKG2D-expressing T cells is a potential immunotherapy for gastric cancer with peritoneal metastasis.

A current review of folate receptor alpha as a potential tumor target in non-small-cell lung cancer

Lung cancer remains the leading common cause of cancer-related death, with non-small-cell lung cancer (NSCLC) accounting for 80% of all cases. To date, platinum-based doublet chemotherapy is the cornerstone of first-line therapy. However, these agents have limited use in patients who have relapsed and have metastatic disease. Therefore, novel strategies are required to improve the clinical outcome. Folate receptor alpha (FRA) is overexpressed in the majority of NSCLC, particularly in lung adenocarcinomas. FRA is largely absent from normal tissue, making it an attractive therapeutic target. In this review, we discuss FRA expression in NSCLC, conjugated FRA agents, monoclonal antibody, and FRA-specific T-cell-based therapeutic strategies aiming to improve the cure rate of FRA-expressing NSCLC.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.

Immunology of chronic myeloid leukemia: current concepts and future goals

Although chronic myeloid leukemia is a rare malignancy, it has developed into a model system for the study of a variety of aspects of cancer biology and immunology. The introduction of tyrosine kinase inhibitors has resulted in a significant prolongation of the survival rates of chronic myeloid leukemia patients but has not resulted in a cure. There is a growing conviction that this aim can be achieved through immunotherapy. For this concept to be successful, a considerable increase in the present understanding of chronic myeloid leukemia immunology is required. The authors attempt to review and evaluate the current findings that demonstrate a number of immunological aberrations in patients prior to the start of any therapy and their normalization after achieving remission. They also discuss the recent clinical trials with experimental therapeutic vaccines and then present their own strategy on how to address the problem.

Chimeric antigen receptor for adoptive immunotherapy of cancer: latest research and future prospects

Chimeric antigen receptors (CARs) are recombinant receptors that combine the specificity of an antigen-specific antibody with the T-cell’s activating functions. Initial clinical trials of genetically engineered CAR T cells have significantly raised the profile of T cell therapy, and great efforts have been made to improve this approach. In this review, we provide a structural overview of the development of CAR technology and highlight areas that require further refinement. We also discuss critical issues related to CAR therapy, including the optimization of CAR T cells, the route of administration, CAR toxicity and the blocking of inhibitory molecules.

Beyond chemotherapy and targeted therapy: adoptive cellular therapy in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is an intractable disease for which effective treatment approaches are urgently needed. The ability to induce antigen-specific immune responses in patients with lung cancer has led to the development of immunotherapy as a novel concept for the treatment of NSCLC. Adoptive cellular therapy (ACT) represents an important advancement in cancer immunotherapy with the utilization of tumor infiltrating lymphocytes, cytokine-induced killer cells, natural killer cells and γδ T cells. In this study, we review recent advances in ACT for NSCLC in clinical trials and provide a perspective on the improvement in ACT and potential therapeutic approaches using engineered T cell therapy for NSCLC.

Construction and evaluation of a novel humanized HER2-specific chimeric receptor

Introduction

The human epidermal growth factor receptor 2 (HER2) represents one of the most studied tumor-associated antigens (TAAs) for cancer immunotherapy. The monoclonal antibody (mAb) trastuzumab has improved the outcomes of patients with HER2+ breast cancer. However, a large number of HER2+ tumors are not responsive to, or become resistant to, trastuzumab-based therapy, and thus more effective therapies targeting HER2 are needed.

Methods

HER2-specific T cells were generated by the transfer of genes that encode chimeric antigen receptor (CAR). Using a multistep overlap extension PCR method, we constructed a novel, humanized HER2 CAR-containing, chA21 single-chain variable fragment (scFv) region of antigen-specific mAb and T-cell intracellular signaling chains made up of CD28 and CD3ζ. An interferon γ and interleukin 2 enzyme-linked immunosorbent assay and a chromium-51 release assay were used to evaluate the antitumor immune response of CAR T cells in coculture with tumor cells. Furthermore, SKBR3 tumor–bearing nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice were treated with HER2 CAR T cells to evaluate antitumor activity. Human CD3+ T cell accumulation in tumor xenograft was detected by immunohistochemistry.

Results

chA21-28z CAR was successfully constructed, and both CD4+ and CD8+ T cells were transduced. The expanded HER2 CAR T cells expressed a central memory phenotype and specifically reacted against HER2+ tumor cell lines. Furthermore, the SKBR3 tumor xenograft model revealed that HER2 CAR T cells significantly inhibited tumor growth in vivo. Immunohistochemical analysis showed robust accumulation of human CD3+ T cells in regressing SKBR3 lesions.

Conclusions

The results of this study show that novel chA21 scFv-based, HER2-specific CAR T cells not only recognized and killed HER2+ breast and ovarian cancer cells ex vivo but also induced regression of experimental breast cancer in vivo. Our data support further exploration of the HER2 CAR T-cell therapy for HER2-expressing cancers.

A new class of bispecific antibodies to redirect T cells for cancer immunotherapy

Various constructs of bispecific antibodies (bsAbs) to redirect effector T cells for the targeted killing of tumor cells have shown considerable promise in both preclinical and clinical studies. The single-chain variable fragment (scFv)-based formats, including bispecific T-cell engager (BiTE) and dual-affinity re-targeting (DART), which provide monovalent binding to both CD3 on T cells and to the target antigen on tumor cells, can exhibit rapid blood clearance and neurological toxicity due to their small size (~55 kDa). Herein, we describe the generation, by the modular DOCK-AND-LOCK™) (DNL™) method, of novel T-cell redirecting bispecific antibodies, each comprising a monovalent anti-CD3 scFv covalently conjugated to a stabilized dimer of different anti-tumor Fabs. The potential advantages of this design include bivalent binding to tumor cells, a larger size (~130 kDa) to preclude renal clearance and penetration of the blood-brain barrier, and potent T-cell mediated cytotoxicity. These prototypes were purified to near homogeneity, and representative constructs were shown to provoke the formation of immunological synapses between T cells and their target tumor cells in vitro, resulting in T-cell activation and proliferation, as well as potent T-cell mediated anti-tumor activity. In addition, in vivo studies in NOD/SCID mice bearing Raji Burkitt lymphoma or Capan-1 pancreatic carcinoma indicated statistically significant inhibition of tumor growth compared with untreated controls.

Cytokine release syndrome in cancer immunotherapy with chimeric antigen receptor engineered T cells

Adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells is a promising therapy for cancers. However, the safety of this approach is concerned. Cytokine release syndrome (CRS) is a common but lethal complication of CAR-T cell therapy. The development of CRS correlates with CAR structures, tumor type and burden, and patients' genetic polymorphisms. CRS related adverse events may be reduced by designing safer CARs and CAR-T cells and following strict dose-escalation scheme. Timely and effective cytokine-directed treatment with corticosteroid and various cytokine antagonists is important to avoid CRS associated death.

Trial Watch: Adoptive cell transfer for anticancer immunotherapy

Adoptive cell transfer (ACT) represents a prominent form of immunotherapy against malignant diseases. ACT is conceptually distinct from dendritic cell-based approaches (which de facto constitute cellular vaccines) and allogeneic transplantation (which can be employed for the therapy of hematopoietic tumors) as it involves the isolation of autologous lymphocytes exhibiting antitumor activity, their expansion/activation ex vivo and their reintroduction into the patient. Re-infusion is most often performed in the context of lymphodepleting regimens (to minimize immunosuppression by host cells) and combined with immunostimulatory interventions, such as the administration of Toll-like receptor agonists. Autologous cells that are suitable for ACT protocols can be isolated from tumor-infiltrating lymphocytes or generated by engineering their circulating counterparts for the expression of transgenic tumor-specific T-cell receptors. Importantly, lymphocytes can be genetically modified prior to re-infusion for increasing their persistence in vivo, boosting antitumor responses and minimizing side effects. Moreover, recent data indicate that exhausted antitumor T lymphocytes may be rejuvenated in vitro by exposing them to specific cytokine cocktails, a strategy that might considerably improve the clinical success of ACT. Following up the Trial Watch that we published on this topic in the third issue of OncoImmunology (May 2012), here we summarize the latest developments in ACT-related research, covering both high-impact studies that have been published during the last 13 months and clinical trials that have been initiated in the same period to assess the antineoplastic profile of this form of cellular immunotherapy.

Improving the efficacy and safety of engineered T cell therapy for cancer

Adoptive T-cell therapy (ACT) using tumor-infiltrating lymphocytes (TILs) is a powerful immunotherapeutics approach against metastatic melanoma. The success of TIL therapy has led to novel strategies for redirecting normal T cells to recognize tumor-associated antigens (TAAs) by genetically engineering tumor antigen-specific T cell receptors (TCRs) or chimeric antigen receptor (CAR) genes. In this manner, large numbers of antigen-specific T cells can be rapidly generated compared with the longer term expansion of TILs. Great efforts have been made to improve these approaches. Initial clinical studies have demonstrated that genetically engineered T cells can mediate tumor regression in vivo. In this review, we discuss the development of TCR and CAR gene-engineered T cells and the safety concerns surrounding the use of these T cells in patients. We highlight the importance of judicious selection of TAAs for modified T cell therapy and propose solutions for potential "on-target, off-organ" toxicity.