Challenges of CRISPR-based Gene Editing in Primary T Cells

Adaptive T cell immunotherapy holds great promise for the successful treatment of leukemia as well as other types of cancers. More recently, it was also shown to be an effective treatment option for chronic virus infections in immunosuppressed patients. Autologous or allogeneic T cells used for immunotherapy are usually genetically modified to express novel T cell or chimeric antigen receptors. The production of such cells was significantly simplified with the CRISPR/Cas system allowing deletion or insertion of novel genes at specific locations within the genome. In this review, we describe recent methodological breakthroughs important for the conduction of these genetic modifications, summarize crucial points to be considered when conducting such experiments, and highlight the potential pitfalls of these approaches.

Engineering Macrophages via Nanotechnology and Genetic Manipulation for Cancer Therapy

Macrophages play critical roles in tumor progression. In the tumor microenvironment, macrophages display highly diverse phenotypes and may perform antitumorigenic or protumorigenic functions in a context-dependent manner. Recent studies have shown that macrophages can be engineered to transport drug nanoparticles (NPs) to tumor sites in a targeted manner, thereby exerting significant anticancer effects. In addition, macrophages engineered to express chimeric antigen receptors (CARs) were shown to actively migrate to tumor sites and eliminate tumor cells through phagocytosis. Importantly, after reaching tumor sites, these engineered macrophages can significantly change the otherwise immune-suppressive tumor microenvironment and thereby enhance T cell-mediated anticancer immune responses. In this review, we first introduce the multifaceted activities of macrophages and the principles of nanotechnology in cancer therapy and then elaborate on macrophage engineering via nanotechnology or genetic approaches and discuss the effects, mechanisms, and limitations of such engineered macrophages, with a focus on using live macrophages as carriers to actively deliver NP drugs to tumor sites. Several new directions in macrophage engineering are reviewed, such as transporting NP drugs through macrophage cell membranes or extracellular vesicles, reprogramming tumor-associated macrophages (TAMs) by nanotechnology, and engineering macrophages with CARs. Finally, we discuss the possibility of combining engineered macrophages and other treatments to improve outcomes in cancer therapy.

Prospects for Development of Induced Pluripotent Stem Cell-Derived CAR-Targeted Immunotherapies

Technologies required to generate induced pluripotent stem cells (iPSC) were first described 15 years ago, providing a strong impetus to the field of regenerative medicine. In parallel, immunotherapy has finally emerged as a clinically meaningful modality of cancer therapy. In particular, impressive efficacy has been achieved in patients with selected haematological malignancies using ex vivo expanded autologous T cells engineered to express chimeric antigen receptors (CARs). While solid tumours account for over 90% of human cancer, they currently are largely refractory to this therapeutic approach. Nonetheless, given the considerable innovation taking place worldwide in the CAR field, it is likely that effective solutions for common solid tumours will emerge in the near future. Such a development will create significant new challenges in the scalable delivery of these complex, costly and individualised therapies. CAR-engineered immune cell products that originate from iPSCs offer the potential to generate unlimited numbers of homogeneous, standardised cell products in which multiple defined gene modification events have been introduced to ensure safety, potency and reproducibility. Here, we review some of the emerging strategies in use to engineer CAR-expressing iPSC-derived drug products.

NK Cells Armed with Chimeric Antigen Receptors (CAR): Roadblocks to Successful Development

In recent years, cell-based immunotherapies have demonstrated promising results in the treatment of cancer. Chimeric antigen receptors (CARs) arm effector cells with a weapon for targeting tumor antigens, licensing engineered cells to recognize and kill cancer cells. The quality of the CAR-antigen interaction strongly depends on the selected tumor antigen and its expression density on cancer cells. CD19 CAR-engineered T cells approved by the Food and Drug Administration have been most frequently applied in the treatment of hematological malignancies. Clinical challenges in their application primarily include cytokine release syndrome, neurological symptoms, severe inflammatory responses, and/or other off-target effects most likely mediated by cytotoxic T cells. As a consequence, there remains a significant medical need for more potent technology platforms leveraging cell-based approaches with enhanced safety profiles. A promising population that has been advanced is the natural killer (NK) cell, which can also be engineered with CARs. NK cells which belong to the innate arm of the immune system recognize and kill virally infected cells as well as (stressed) cancer cells in a major histocompatibility complex I independent manner. NK cells play an important role in the host’s immune defense against cancer due to their specialized lytic mechanisms which include death receptor (i.e., Fas)/death receptor ligand (i.e., Fas ligand) and granzyme B/perforin-mediated apoptosis, and antibody-dependent cellular cytotoxicity, as well as their immunoregulatory potential via cytokine/chemokine release. To develop and implement a highly effective CAR NK cell-based therapy with low side effects, the following three principles which are specifically addressed in this review have to be considered: unique target selection, well-designed CAR, and optimized gene delivery.

Adoptive Chimeric Antigen Receptor T Cell (CAR-T) and Treg Cell-Based Immunotherapies: Frontier Therapeutic Aspects in Cancers

Based on this point that some cancers do not appropriately respond to conventional therapy, and there is the possibility of relapse, immunotherapy is currently under investigation. Cancer immunotherapies are widely recognized as transformational for several cancers and enable to move to the front-line therapy with few side effects. One of its new branches is treatment with T-cells that have been changed their receptor. The research on these cells is generally according to the design of a receptor against a specific tumor antigen. Also, manipulation of regulatory T-cell (Tregs), as the barriers to proper immune responses in the tumor microenvironment, will promote Tregs-targeted therapeutic opportunities and improve the efficacy of the current cancer treatment, such as radiation and chemotherapy. This review attempts to show novel insights into the roles of Tregs in cancer which can be considered a promising anticancer therapeutic strategy for targeting them and approaches for the generation of tumor antigen-specific T lymphocytes (AST) using chimeric antigen receptors.

Inefficient exploitation of accessory receptors reduces the sensitivity of chimeric antigen receptors.

Chimeric antigen receptors (CARs) can re-direct T cells to target abnormal cells but their activity is limited by a profound defect in antigen sensitivity, the source of which remains unclear. Here, we show that CARs have a > 100-fold lower antigen sensitivity compared to the TCR when antigen is presented on antigen-presenting-cells, but nearly identical sensitivity when antigen is presented as purified protein in isolation. Given that the TCR uses other, accessory, receptors to achieve high sensitivity, we screened prominent accessory receptors by presenting their purified ligands together with antigen. We found that ligating the adhesion receptor CD2 or LFA-1 improved antigen sensitivity for the TCR by > 100-fold, whereas for CARs the improvement was < 10-fold. We reproduced these findings using target cells where the CD2 and/or LFA-1 interaction were abrogated. Sensitivity can be partially restored by fusing the CAR variable domains to the TCR CD3ϵ subunit (also known as a TRuC) and fully restored when exchanging the TCRαβ variable domains for those of the CAR (also known as a STAR). Our study localises the defect in CAR sensitivity to inefficient use of accessory receptors and suggests approaches to increase sensitivity.

Therapeutic Applications of Engineered Chimeric Antigen Receptors-T cell for Cancer Therapy

Findings of new targeted treatments with adequate safety evaluations is essential for better cancer cures and mortality rates. Immunotherapy holds promise for patients with relapsed disease, with the ability to elicit long-term remissions. Emerging promising clinical results in B-cell malignancy using gene-altered T-lymphocytes uttering chimeric antigen receptors have sparked a lot of interest. This treatment could open the path for a major difference in the way we treat tumors that are resistant or recurring. Genetically altered T cells used to produce tumor-specific chimeric antigen receptors are resurrected field of adoptive cell therapy by demonstrating remarkable success in the treatment of malignant tumors. Because of the molecular complexity of chimeric antigen receptors -T cells, a variety of engineering approaches to improve safety and effectiveness are necessary to realize larger therapeutic uses. In this study, we investigate at new strategies for enhancing chimeric antigen receptors-T cell therapy by altering chimeric antigen receptors proteins, T lymphocytes, and their relations with other solid tumor microenvironment (TME) aspects.