Engineering tumor stromal mechanics for improved T cell therapy

Adoptive cellular therapies (ACT), including the engineered T cell receptor (TCR) therapy and chimeric antigen receptor (CAR) T Cell Therapy, are currently at the forefront of cancer immunotherapy. However, their efficacy for the treatment of solid tumors has not been confirmed. The fibrotic stroma surrounding the solid tumor has been suggested as the main barrier in the disarmament and suppression of the engineered T cells. In this review, we will discuss the recent findings on the mechanism of T cell suppression by the tumor stroma with a special emphasis on the effect of stromal mechanics. We will also discuss the engineering approaches used to dissect the mechanism of the T cell suppression by the stromal mechanical factors. Finally, we will provide a future outlook on the strategies to improve the efficacy of T cell therapy through altering the tumor stromal fibrosis.     

Directing CAR T cells towards the tumor vasculature for the treatment of solid tumors

For successful application of chimeric antigen receptor (CAR) T cell therapy in solid tumors, major hurdles have to be overcome. CAR T cells have to cross the vascular barrier, which is hampered by the anergic state of the tumor vasculature, characterized by suppressed levels of leukocyte adhesion molecules on the endothelium. Additional immunosuppressive mechanisms in the solid tumor microenvironment can affect infiltration, activity and persistence of CAR T cells. Redirecting CAR T cells towards the tumor vasculature poses a possible solution, as molecular targets of tumor endothelial cells can be directly engaged from within the blood.In this review, we discuss recent advances in CAR T cell therapy against solid tumors, with a focus on targeting the tumor vasculature. Furthermore, we discuss opportunities to overcome challenges and barriers through engineering of CAR T cells to enhance trafficking, safety and efficacy.     

Phase 1 clinical trial demonstrated that MUC1 positive metastatic seminal vesicle cancer can be effectively eradicated by modified Anti-MUC1 chimeric antigen receptor transduced T cells

Recent progress in chimeric antigen receptor-modified T-cell(CAR-T cell) technology in cancer therapy is extremely promising, especially in the treatment of patients with B-cell acute lymphoblastic leukemia. In contrast, due to the hostile immunosuppressive microenvironment of a solid tumor, CAR T-cell accessibility and survival continue to pose a considerable challenge, which leads to their limited therapeutic efficacy. In this study, we constructed two anti-MUC1 CAR-T cell lines. One set of CAR-T cells contained SM3 single chain variable fragment(sc Fv) sequence specifically targeting the MUC1 antigen and co-expressing interleukin(IL) 12(named SM3-CAR). The other CAR-T cell line carried the SM3 sc Fv sequence modified to improve its binding to MUC1 antigen(named p SM3-CAR) but did not co-express IL-12. When those two types of CAR-T cells were injected intratumorally into two independent metastatic lesions of the same MUC1+ seminal vesicle cancer patient as part of an interventional treatment strategy, the initial results indicated no side-effects of the MUC1 targeting CAR-T cell approach, and patient serum cytokines responses were positive. Further evaluation showed that p SM3-CAR effectively caused tumor necrosis, providing new options for improved CAR-T therapy in solid tumors.     

Micro-hydrogel injectables that deliver effective CAR-T immunotherapy against 3D solid tumor spheroids

Chimeric antigen receptor (CAR-) T cells are revolutionizing cancer treatment, as a direct result of their clinical impact on the treatment of hematological malignancies. However for solid tumors, CAR-T cell therapeutic efficacy remains limited, primarily due to the complex immunosuppressive tumor microenvironment, inefficient access to tumor cells and poor persistence of the killer cells. In this in vitro study, an injectable, gelatin-based micro-hydrogel system that can encapsulate and deliver effective CAR-T therapy is investigated. CAR-T cells targeting TAG-72, encapsulated in these microgels possessed high viability (> 87%) after 7 days, equivalent to those grown under normal expansion conditions, with retention of the T cell phenotype and functionality. Microgel recovered CAR-T cells demonstrated potent on-target cytotoxicity against human ovarian cancer in vitro and on three-dimensional tumor spheroids, by completely eliminating tumor cells. The gelatin-based micro-hydrogels have the potential to serve as carrier systems to augment CAR-T immunotherapeutic treatment of solid tumors.     

嵌合抗原受体巨噬细胞免疫疗法及其在实体瘤治疗中的应用

嵌合抗原受体T细胞（chimeric antigen receptor T-cell,CAR-T）疗法在血液肿瘤中取得了显著成功,但在实体瘤的治疗中收效甚微。相比之下,固有免疫细胞在癌症中的临床应用还没有得到广泛开发。巨噬细胞是肿瘤微环境中主要的固有免疫细胞并具有较强的吞噬和浸润能力,最近研究发现嵌合抗原受体巨噬细胞（chimeric antigen receptor macrophage,CAR-M）免疫疗法在多种实体瘤中发挥重要的抗肿瘤效应。本文总结了近年来CAR-M治疗肿瘤的相关研究,旨在探究其对实体瘤的潜在治疗价值,为其未来的临床应用提供参考。     

CAR T targets and microenvironmental barriers of osteosarcoma

Osteosarcoma (OS) is one of the most common malignancies in children and adolescents. Multimodal chemotherapy and aggressive surgical resection have improved the prognosis of patients with osteosarcoma. However, the prognosis of OS patients with unresectable advanced tumors, distant metastasis or chemotherapy is still poor. Chimeric antigen receptor (CAR) T cells have achieved remarkable success in the treatment of hematologic malignancies, injecting new vitality into the field of adoptive cell therapy. However, the efficacy in solid tumors has been largely limited. The reason for the poor curative effect of solid tumors is mainly the heterogeneity of solid tumor antigen, immune escape, tumor microenvironment barrier, resistance of immunosuppressive cells and inhibitory factors, which lead to the obstruction of CAR T cell infiltration and the aggravation of failure. Potential antigenic targets for osteosarcoma CAR T cell therapy are under continuous exploration. Some of the antigenic targets, such as anti-HER2-CAR T cells, have achieved good results in preclinical studies, and some of them have entered clinical studies and achieved certain clinical effects. In this review, we discuss the research progress of potential antigen targets and osteosarcoma microenvironment of CAR T cells in the treatment of osteosarcoma.     

A Novel Ex Vivo Isolation and Expansion Procedure for Chimeric Antigen Receptor Engrafted Human T Cells

Genetically engineered T lymphocytes are a promising option for cancer therapy. Prior to adoptive transfer they have to be expanded in vitro to reach therapeutically sufficient numbers. So far, no universal method exists for selective in vitro expansion of engineered T lymphocytes. In order to overcome this problem and for proof of concept we incorporated a novel unique peptide sequence of ten amino acids as epitope (E-Tag) into the binding domains of two novel chimeric antigen receptors (ECARs) directed against either prostate stem cell antigen (PSCA) for the treatment of prostate cancer (PCa) or CD33 for the treatment of acute myeloide leukemia (AML). The epitope tag then was utilized for expanding ECAR engrafted T cells by triggering the modified T cells via a monoclonal antibody directed against the E-Tag (Emab). Moreover, the E-Tag served as an efficient selection epitope for immunomagnetic isolation of modified T cells to high purity. ECAR engrafted T cells were fully functional and mediated profound anti-tumor effects in the respective models of PCa or AML both in vitro and in vivo. The method can be integrated straightforward into clinical protocols to improve therapeutic efficiency of tumor treatment with CAR modified T lymphocytes.     

Effective Therapeutic Approach for Head and Neck Cancer by an Engineered Minibody Targeting the EGFR Receptor

Cetuximab, a chimeric monoclonal antibody developed for targeting the Epidermal Growth Factor Receptor (EGFR), has been intensively used to treat cancer patients with metastatic colorectal cancer and head and neck cancer. Intact immunoglobulin G (IgG) antibody like cetuximab, however, has some limitations such as high production cost and low penetration rate from vasculature into solid tumor mass due to its large size. In attempt to overcome these limitations, we engineered cetuximab to create single chain variable fragments (scFv-CH3; Minibody) that were expressed in bacterial system. Among three engineered minibodies, we found that MI061 minibody, which is composed of the variable heavy (V_H) and light (V_L) region joined by an 18-residue peptide linker, displays higher solubility and better extraction properties from bacterial lysate. In addition, we validated that purified MI061 significantly interferes ligand binding to EGFR and blocks EGFR''s phosphorylation. By using a protein microarray composed of 16,368 unique human proteins covering around 2,400 plasma membrane associated proteins such as receptors and channels, we also demonstrated that MI061 only recognizes the EGFR but not other proteins as compared with cetuximab. These results indicated that engineered MI061 retains both binding specificity and affinity of cetuximab for EGFR. Although it had relatively short half-life in serum, it was shown to be highly significant anti-tumor effect by inhibiting ERK pathway in A431 xenograft model. Taken together, our present study provides compelling evidence that engineered minibody is more effective and promising agent for in vivo targeting of solid tumors.     

The Engineered Thymidylate Kinase (TMPK)/AZT Enzyme-Prodrug Axis Offers Efficient Bystander Cell Killing for Suicide Gene Therapy of Cancer

We previously described a novel suicide (or ‘cell fate control’) gene therapy enzyme/prodrug system based on an engineered variant of human thymidylate kinase (TMPK) that potentiates azidothymidine (AZT) activation. Delivery of a suicide gene sequence into tumors by lentiviral transduction embodies a cancer gene therapy that could employ bystander cell killing as a mechanism driving significant tumor regression in vivo. Here we present evidence of a significant bystander cell killing in vitro and in vivo mediated by the TMPK/AZT suicide gene axis that is reliant on the formation of functional gap-junctional intercellular communications (GJICs). Potentiation of AZT activation by the engineered TMPK expressed in the human prostate cancer cell line, PC-3, resulted in effective bystander killing of PC-3 cells lacking TMPK expression – an effect that could be blocked by the GJIC inhibitor, carbenoxolone. Although GJICs are mainly formed by connexins, a new family of GJIC molecules designated pannexins has been recently identified. PC-3 cells expressed both connexin43 (Cx43) and Pannexin1 (Panx1), but Panx1 expression predominated at the plasma membrane, whereas Cx43 expression was primarily localized to the cytosol. The contribution of bystander effects to the reduction of solid tumor xenografts established by the PC-3 cell line was evaluated in an animal model. We demonstrate the contribution of bystander cell killing to tumor regression in a xenograft model relying on the delivery of expression of the TMPK suicide gene into tumors via direct intratumoral injection of recombinant therapeutic lentivirus. Taken together, our data underscore that the TMPK/AZT enzyme-prodrug axis can be effectively utilized in suicide gene therapy of solid tumors, wherein significant tumor regression can be achieved via bystander effects mediated by GJICs.     

Ephrin receptor A10 monoclonal antibodies and the derived chimeric antigen receptor T cells exert an antitumor response in mouse models of triple-negative breast cancer

Expression of the receptor tyrosine kinase ephrin receptor A10 (EphA10), which is undetectable in most normal tissues except for the male testis, has been shown to correlate with tumor progression and poor prognosis in several malignancies, including triple-negative breast cancer (TNBC). Therefore, EphA10 could be a potential therapeutic target, likely with minimal adverse effects. However, no effective clinical drugs against EphA10 are currently available. Here, we report high expression levels of EphA10 in tumor regions of breast, lung, and ovarian cancers as well as in immunosuppressive myeloid cells in the tumor microenvironment. Furthermore, we developed anti-EphA10 monoclonal antibodies (mAbs) that specifically recognize cell surface EphA10, but not other EphA family isoforms, and target tumor regions precisely in vivo with no apparent accumulation in other organs. In syngeneic TNBC mouse models, we found that anti-EphA10 mAb clone #4 enhanced tumor regression, therapeutic response rate, and T cell–mediated antitumor immunity. Notably, the chimeric antigen receptor T cells derived from clone #4 significantly inhibited TNBC cell viability in vitro and tumor growth in vivo. Together, our findings suggest that targeting EphA10 via EphA10 mAbs and EphA10-specific chimeric antigen receptor–T cell therapy may represent a promising strategy for patients with EphA10-positive tumors.     

Hurdles of CAR-T cell-based cancer immunotherapy directed against solid tumors

Recent reports on the impressive efficacy of chimeric antigen receptor (CAR)-modified T cells against hematologic malignancies have inspired oncologists to extend these efforts for the treatment of solid tumors. Clinical trials of CAR-T-based cancer immunotherapy for solid tumors showed that the efficacies are not as remarkable as in the case of hematologic malignancies. There are several challenges that researchers must face when treating solid cancers with CAR-T cells, these include choosing an ideal target, promoting efficient trafficking and infiltration, overcoming the immunosuppressive microenvironment, and avoiding associated toxicity. In this review, we discuss the obstacles imposed by solid tumors on CAR-T cell-based immunotherapy and strategies adopted to improve the therapeutic potential of this approach. Continued investigations are necessary to improve therapeutic outcomes and decrease the adverse effects of CAR-T cell therapy in patients with solid malignancies in the future.     

Using the allergic immune system to target cancer: activity of IgE antibodies specific for human CD20 and MUC1

Monoclonal antibodies are widely used in the treatment of many B cell lymphomas and certain solid tumors. All currently approved therapeutic monoclonal antibodies are of the immunoglobulin G (IgG) isotype. We hypothesized that tumor-specific monoclonal antibodies of the IgE isotype may serve as effective cancer therapeutics. To test this hypothesis, we produced mouse?Chuman chimeric IgE antibodies specific for the human B cell antigen CD20 and the epithelial antigen MUC1. We demonstrate here that anti-hCD20 IgE antibodies have in vitro cytotoxic activity when used with purified allergic effector cells derived from umbilical cord blood. At an effector-tumor ratio of 2:1, mast cells and tumor-specific IgE induced a 2.5-fold increase in tumor cell death, as compared to control IgE. Similar results were observed when eosinophils were used as effector cells. In an in vivo murine model of breast carcinoma, administration of anti-hMUC1 IgE reduced the growth of MUC1⁺ tumors by 25?C30?% in hFc??RI transgenic mice. In contrast, local production of IgE and cytokines chemotactic for macrophages, eosinophils and mast cells led to complete tumor eradication. These results suggest that allergic effector cells activated by IgE and cell surface antigens have the capacity to induce tumor cell death in vitro and in vivo. The use of chimeric antibodies and hFc??RI transgenic mice will greatly enhance investigations in the nascent field of allergo-oncology.     

免疫检查点程序性细胞死亡蛋白配体-1翻译后修饰及其在免疫治疗中的应用前景

免疫检查点程序性细胞死亡蛋白配体-1(programmed cell death 1 ligand 1,PD-L1)是一种主要表达于肿瘤细胞表面的免疫抑制性分子,其可与T淋巴细胞表面的程序性细胞死亡蛋白-1(programmed cell death protein 1,PD-1)结合,抑制T淋巴细胞的激活,发挥免疫抑...     

嵌合抗原受体T细胞介绍及抗肿瘤临床应用

过继性细胞免疫治疗（adoptive cellular immunotherapy,ACI）是目前较为有效的恶性肿瘤的治疗方法之一。随着技术的日趋成熟,已在多种实体瘤和血液肿瘤的t临床治疗中取得较好疗效。其中,嵌合抗原受体（chimeric antigen receptor,CAR）T细胞技术是近年来发展非常迅速的一种细胞治疗技术。通过基因改造技术,效应T细胞的靶向性、杀伤活性和持久性均较常规应用的免疫细胞高,并可克服肿瘤局部免疫抑制微环境和打破宿主免疫耐受状态。目前,CAR的信号域已从第一代的单一信号分子发展为包含CD28、4—1BB等共刺激分子的多信号结构域（第二、三代）,临床应用广泛。但是,该技术也存在脱靶效应、插入突变等临床应用风险。该文将就CAR—T细胞技术在恶性肿瘤免疫治疗中的应用及可能存在的问题作一综述。     

Induced pluripotent stem cell-derived engineered T cells,natural killer cells,macrophages, and dendritic cells in immunotherapy

T cells, natural killer (NK) cells, macrophages (Macs), and dendritic cells (DCs) are among the most common sources for immune-cell-based therapies for cancer. Antitumor activity can be enhanced in induced pluripotent stem cell (iPSC)-derived immune cells by using iPSCs as a platform for stable genetic modifications that impact immuno-activating or -suppressive signaling pathways, such as transducing a chimeric antigen receptor (CAR) or deletion of immunosuppressive checkpoint molecules. This review outlines the utility of four iPSC-derived immune-cell-based therapies, highlight the latest progress and future trends in the genome-editing strategies designed to improve efficacy, safety, and universality, and provides perspectives that compare different contexts in which each of these iPSC-derived immune cell types can be most effectively used.     

Anti-Tumoral Effect of the Mitochondrial Target Domain of Noxa Delivered by an Engineered Salmonella typhimurium

Bacterial cancer therapy relies on the fact that several bacterial species are capable of targeting tumor tissue and that bacteria can be genetically engineered to selectively deliver therapeutic proteins of interest to the targeted tumors. However, the challenge of bacterial cancer therapy is the release of the therapeutic proteins from the bacteria and entry of the proteins into tumor cells. This study employed an attenuated Salmonella typhimurium to selectively deliver the mitochondrial targeting domain of Noxa (MTD) as a potential therapeutic cargo protein, and examined its anti-cancer effect. To release MTD from the bacteria, a novel bacterial lysis system of phage origin was deployed. To facilitate the entry of MTD into the tumor cells, the MTD was fused to DS4.3, a novel cell-penetrating peptide (CPP) derived from a voltage-gated potassium channel (K_v2.1). The gene encoding DS4.3-MTD and the phage lysis genes were placed under the control of P_BAD, a promoter activated by L-arabinose. We demonstrated that DS4.3-MTD chimeric molecules expressed by the Salmonellae were anti-tumoral in cultured tumor cells and in mice with CT26 colon carcinoma.     

Generation of Metal-Binding Staphylococci through Surface Display of Combinatorially Engineered Cellulose-Binding Domains

Ni²⁺-binding staphylococci were generated through surface display of combinatorially engineered variants of a fungal cellulose-binding domain (CBD) from Trichoderma reesei cellulase Cel7A. Novel CBD variants were generated by combinatorial protein engineering through the randomization of 11 amino acid positions, and eight potentially Ni²⁺-binding CBDs were selected by phage display technology. These new variants were subsequently genetically introduced into chimeric surface proteins for surface display on Staphylococcus carnosus cells. The expressed chimeric proteins were shown to be properly targeted to the cell wall of S. carnosus cells, since full-length proteins could be extracted and affinity purified. Surface accessibility for the chimeric proteins was demonstrated, and furthermore, the engineered CBDs, now devoid of cellulose-binding capacity, were shown to be functional with regard to metal binding, since the recombinant staphylococci had gained Ni²⁺-binding capacity. Potential environmental applications for such tailor-made metal-binding bacteria as bioadsorbents in biofilters or biosensors are discussed.     

Zoledronic acid modulates antitumoral responses of prostate cancer-tumor associated macrophages

Macrophages are considered a key component of the immunosuppressive environment present in solid tumors, where they support tumor growth through the production of pro-angiogenic factors and active suppression of effector immune responses. Zoledronic acid (ZA), an aminobisphosphonate clinically approved for treatment of symptomatic skeletal events, has recently been shown to have immunomodulatory properties that can be exploited in cancer immunotherapy. Here, we utilize an in vitro model of prostate cancer cell-macrophage interaction to dissect the effect of ZA, on the function of prostate cancer tumor-associated macrophages (PC-TAM). We show that prostate cancer cells recruit macrophages, which in turn express a variety of proangiogenic and immunosuppressive mediators. ZA selectively suppressed the expression of MMP-9 by PC-TAM, whereas the expression of other mediators was not limited. PC-TAM treated with ZA, on the other hand, could effectively drive the proliferation of activated Tgammadelta lymphocytes, which lysed bisphosphonate-pulsed prostate cancer cells. Moreover, ZA boosted the production of type-1 cytokines by PC-TAM in response to immunomodulators such as IL-12 and polyI:C, which are known to polarize macrophages towards an anti-tumoral M1 phenotype. Overall, we provide evidence that ZA shifts the balance of PC-TAM from a tumor promoting to a tumor-eliminating phenotype and also suggest a potential use of this pharmacological agent as an immunotherapeutic adjuvant.     

Therapeutic effects on experimental metastatic tumor-bearing mice by vaccination with GM-CSF gene-modified and tumor antigen-pulsed macrophages

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Time to abandon CAR-T monotherapy for solid tumors

In recent decades, chimeric antigen receptor T (CAR-T) cell therapy has achieved dramatic success in patients with hematological malignancies. However, CAR-T cell therapy failed to effectively treat solid tumors as a monotherapy. By summarizing the challenges of CAR-T cell monotherapy for solid tumors and analyzing the underlying mechanisms of combinatorial strategies to counteract these hurdles, we found that complementary therapeutics are needed to improve the scant and transient responses of CAR-T cell monotherapy in solid tumors. Further data, especially data from multicenter clinical trials regarding efficacy, toxicity, and predictive biomarkers are required before the CAR-T combination therapy can be translated into clinical settings.