T-cell receptor and chimeric antigen receptor in solid cancers: current landscape, preclinical data and insight into future developments

Advanced Strategies of CAR-T Cell Therapy in Solid Tumors and Hematological Malignancies

Chimeric antigen receptor T-cells, known as CAR-T cells, represent a promising breakthrough in the realm of adoptive cell therapy. These T-cells are genetically engineered to carry chimeric antigen receptors that specifically target tumors. They have achieved notable success in the treatment of blood-related cancers, breathing new life into this field of medical research. However, numerous obstacles limit chimeric antigen receptors T-cell therapy's efficacy, such as it cannot survive in the body long. It is prone to fatigue and exhaustion, leading to difficult tumor elimination and repeated recurrence, affecting solid tumors and hematological malignancies. The challenges posed by solid tumors, especially in the context of the complex solid-tumor microenvironment, require specific strategies. This review outlines recent advancements in improving chimeric antigen receptors T-cell therapy by focusing on the chimeric antigen receptors protein, modifying T-cells, and optimizing the interaction between T-cells and other components within the tumor microenvironment. This article aims to provide an extensive summary of the latest discoveries regarding CAR-T cell therapy, encompassing its application across various types of human cancers. Moreover, it will delve into the obstacles that have emerged in recent times, offering insights into the challenges faced by this innovative approach. Finally, it highlights novel therapeutic options in treating hematological and solid malignancies with chimeric antigen receptors T-cell therapies.

Extensive functional comparisons between chimeric antigen receptors and T cell receptors highlight fundamental similarities

Though TCRs have been subject to limited engineering in the context of therapeutic design and optimization, they are used largely as found in nature. On the other hand, CARs are artificial, composed of different segments of proteins that function in the immune system. This characteristic raises the possibility of altered response to immune regulatory stimuli. Here we describe a large-scale, systematic comparison of CARs and TCRs across 5 different pMHC targets, with a total of 19 constructs examined in vitro. These functional measurements include CAR- and TCR-mediated activation, proliferation, and cytotoxicity in both acute and chronic settings. Surprisingly, we find no consistent difference between CARs and TCRs as receptor classes with respect to their relative sensitivity to major regulators of T cell activation: PD-L1, CD80/86 and IL-2. Though TCRs often emerge from human blood directly as potent, selective receptors, CARs must be heavily optimized to attain these properties for pMHC targets. Nonetheless, when iteratively improved and compared head to head in functional tests, CARs appear remarkably similar to TCRs with respect to immune modulation.

Novel strategies for immuno-oncology breakthroughs with cell therapy

Cell therapy has evolved rapidly in the past several years with more than 250 clinical trials ongoing around the world. While more indications of cellular therapy with chimeric antigen receptor - engineered T cells (CAR-T) are approved for hematologic malignancies, new concepts and strategies of cellular therapy for solid tumors are emerging and are discussed. These developments include better selections of targets by shifting from tumor-associated antigens to personalized tumor-specific neoantigens, an enhancement of T cell trafficking by breaking the stromal barriers, and a rejuvenation of exhausted T cells by targeting immunosuppressive mechanisms in the tumor microenvironment (TME). Despite significant remaining challenges, we believe that cell therapy will once again lead and revolutionize cancer immunotherapy before long because of the maturation of technologies in T cell engineering, target selection and T cell delivery. This review highlighted the recent progresses reported at the 2020 China Immuno-Oncology Workshop co-organized by the Chinese American Hematologist and Oncologist Network (CAHON), the China National Medical Product Administration (NMPA), and Tsinghua University.

Delivery of adoptive cell therapy in the context of the health-care system in the UK: challenges for clinical sites

Advanced Therapy Medicinal Products (ATMPs) comprise novel cell, tissue and gene therapies and offer the potential of durable remissions for diseases where there is a high unmet clinical need. Once considered a niche area of academic research, ATMPs now represent one of the fastest-growing areas of clinical development. The field has seen a rapid expansion of academic and commercial entities successfully translating ATMP research into the clinic. This is reflected in projection that the global gene and cell therapy market will be worth US $11.96 billion by 2025. However, these treatments are complex to deliver and frequently do not fit naturally into established healthcare systems. In the United Kingdom (UK) there has been a long-standing interest in ATMP research and, in order to meet the ambition to act as an international hub of activity for delivery of ATMPs, a collaborative network of Advanced Therapy Treatment Centres (ATTCs) has been established. This review explores the challenges of delivery in the clinical setting, focussing on one form of ATMP, Adoptive Cell Therapy (ACT). We describe the strategy being implemented in the UK to optimise the roll-out of these exciting new therapies.

Decreased cytotoxic T cells and TCR clonality in organ transplant recipients with squamous cell carcinoma

T-cell landscape differences between cutaneous squamous cell carcinoma (cSCC) tumors in immune competent (SCC in IC) and immunocompromised organ transplant recipients (TSCC in OTR) are unclear. We developed an analytical method to define tumor infiltrating lymphocyte (TIL) phenotype in cSCC from immune competent and immune suppressed patients using single-cell TCR sequencing and gene expression data. TSCC exhibits reduced proportions of cytotoxic and naïve TILs and similar numbers of regulatory TILs. Fewer, more heterogeneous TCR clonotypes are observed in TIL from OTR. Most TCR sequences for top ten clonotypes correspond to known antigens, while 24% correspond to putative neoantigens. OTR show increased cSCC events over 12 months possibly due to reduced cytotoxic T-cells. Our novel method of barcoding CD8+ T-cells is the first providing gene expression and TCR sequences in cSCC. Knowledge regarding putative antigens recognized by TCRs with phenotypic function of T-cells bearing those TCRs could facilitate personalized cSCC treatments.

The Role of Antigen Spreading in the Efficacy of Immunotherapies

The introduction and the unexpected efficacy of checkpoint inhibitors (CPI) and more recently of chimeric antigen receptor T cells (CAR T-cells) in the treatment of malignant diseases boosted the efforts in the development and clinical application of immunotherapeutic approaches. However, the definition of predictive factors associated with clinical responses as well as the identification of underlying mechanisms that promote the therapeutic efficacy remain to be determined. Starting from the first immunotherapeutic trials, it became evident that vaccine-induced tumor-specific T cells or the adoptive transfer of ex vivo-expanded T lymphocytes can recognize and eliminate malignant cells leading to long-lasting remissions in some patients. In addition, a phenomenon called epitope spreading, which was observed in responding patients, seemed to increase the efficiency possibly representing an important predictive factor. This review will focus on experimental and clinical evidence for the induction of epitope spreading and its role in the maintenance of an efficient antitumor immune response in cancer immunotherapy.

Trial watch: chemotherapy-induced immunogenic cell death in immuno-oncology

The term ‘immunogenic cell death’ (ICD) denotes an immunologically unique type of regulated cell death that enables, rather than suppresses, T cell-driven immune responses that are specific for antigens derived from the dying cells. The ability of ICD to elicit adaptive immunity heavily relies on the immunogenicity of dying cells, implying that such cells must encode and present antigens not covered by central tolerance (antigenicity), and deliver immunostimulatory molecules such as damage-associated molecular patterns and cytokines (adjuvanticity). Moreover, the host immune system must be equipped to detect the antigenicity and adjuvanticity of dying cells. As cancer (but not normal) cells express several antigens not covered by central tolerance, they can be driven into ICD by some therapeutic agents, including (but not limited to) chemotherapeutics of the anthracycline family, oxaliplatin and bortezomib, as well as radiation therapy. In this Trial Watch, we describe current trends in the preclinical and clinical development of ICD-eliciting chemotherapy as partner for immunotherapy, with a focus on trials assessing efficacy in the context of immunomonitoring.