CRISPR/Cas9-mediated PD-1 disruption enhances human mesothelin-targeted CAR T cell effector functions

CAR-T therapy: Prospects in targeting cancer stem cells

Cancer stem cells (CSCs), a group of tumour cells with stem cell characteristics, have the ability of self-renewal, multi-lineage differentiation and tumour formation. Since CSCs are resistant to conventional radiotherapy and chemotherapy, their existence may be one of the root causes of cancer treatment failure and tumour progression. The elimination of CSCs may be effective for eventual tumour eradication. Because of the good therapeutic effects without major histocompatibility complex (MHC) restriction and the unique characteristics of CSCs, chimeric antigen receptor T-cell (CAR-T) therapy is expected to be an important method to eliminate CSCs. In this review, we have discussed the feasibility of CSCs-targeted CAR-T therapy for cancer treatment, summarized current research and clinical trials of targeting CSCs with CAR-T cells and forecasted the challenges and future direction from the perspectives of toxicity, persistence and potency, trafficking, infiltration, immunosuppressive tumour microenvironment, and tumour heterogeneity.

Endoglin-Aptamer-Functionalized Liposome-Equipped PD-1-Silenced T Cells Enhance Antitumoral Immunotherapeutic Effects

Background

The broader application of adoptive cell therapy (ACT) in cancer immunotherapies (particularly for solid tumors) has always been limited by the immunosuppressive tumor microenvironment (TME) and the insufficient targetability of effector T cells, resulting in unsatisfied therapeutic outcome. Here, we designed a new strategy by using aptamer-based immunoliposomes to modify PD-1-silencing T cells, which were activated by dendritic cell (DC)/tumor fusion cells (FCs) to improve the antitumor potency of cytotoxic T lymphocytes (CTLs/CD8⁺ T cells).

Methods

PD-1 gene was knocked out from CD8⁺ T cells using CRISPR/Cas9 system to liberate T cell activity from immunosuppression. The PD-1⁻ T cells were stimulated with DC/tumor FCs, followed by further functional modification of tumor-specific nanoliposomes (hEnd-Apt/CD3-Lipo) to generate FC/PD-1⁻ CTLs. The activation and proliferation and specificity of the modified FC/PD-1⁻ CTLs were measured. The antitumor activity of these CTLs against HepG2-tumors was evaluated in xenograft NOD/SCID mice, and the antitumor mechanism was investigated based on tissue immunohistochemistry and serum ELISA.

Results

Our results indicated that the modification of hEnd-Apt/CD3-Lipo nanocomposites on the FC/PD-1⁻ CTLs had a more substantial synergetic effect in inhibiting tumor growth and prolonging animal survival, rather than other control liposomes. Furthermore, the hEnd-Apt/CD3-Lipo-modified FC/PD-1⁻ CTLs showed a stronger antitumor outcome in the tumor-bearing mouse model, through the mechanisms of suppressing tumor cell proliferation, promoting tumor apoptosis, reducing angiogenesis but increasing the infiltration of the FC/PD-1⁻ CTLs in the tumor tissue, as well as upregulating the systemic levels of IFN-γ, IL-2, TNF-α and IL-6 cytokines, by comparison of the control settings.

Conclusion

In sum, our investigation suggests an enhancement of antitumor effect by the surface modification of endoglin-targeting nanoliposomes upon DC/tumor FC-activated PD-1⁻ CTLs, therefore, provides a new tumoral endoglin-targeted approach as a promising strategy to reduce immunosuppression of tumor microenvironment and improve the immunotherapeutic outcome of anticancer ACT.

Insight into next-generation CAR therapeutics: designing CAR T cells to improve clinical outcomes

Chimeric antigen receptor (CAR) T cell therapy has shown considerable promise for hematologic malignancies, leading to the US Food and Drug Administration approval of two CAR T cell-based therapies for the treatment of B cell acute lymphoblastic leukemia and large B cell lymphoma. Despite success in hematologic malignancies, the treatment landscape of CAR T cell therapy for solid tumors has been limited. There are unique challenges in the development of novel CAR T cell therapies to improve both safety and efficacy. Improved understanding of the immunosuppressive tumor microenvironment and resistance mechanisms has led to encouraging approaches to mitigating these obstacles. This Review will characterize challenges with current CAR T designs for hematologic malignancies and solid tumors and emphasize preclinical and clinical strategies to overcome them with novel CAR T cell therapies.

Chimeric Antigen Receptor-Engineered Natural Killer (CAR NK) Cells in Cancer Treatment; Recent Advances and Future Prospects

Natural Killer (NK) cells are critical members of the innate immunity lymphocytes and have a critical role in host defense against malignant cells. Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR) redirects the specificity of the immune cell against a target-specific antigen. ACT has recently created an outstanding opportunity for cancer treatment. Unlike CAR-armored T cells which hadnsome shortcomings as the CAR-receiving construct, Major histocompatibility complex (MHC)-independency, shorter lifespan, the potential to produce an off-the-shelf immune product, and potent anti-tumor properties of the NK cells has introduced NK cells as a potent alternative target for expression of CAR. Here, we aim to provide an updated overview on the current improvements in CAR NK design and immunobiology and describe the potential of CAR-modified NK cells as an alternative “off-the-shelf” carrier of CAR. We also provide lists for the sources of NK cells in the process of CAR NK cell production, different methods for transduction of the CAR genetic sequence to NK cells, the differences between CAR T and CAR NK, and CAR NK-targeted tumor antigens in current studies. Additionally, we provide data on recently published preclinical and clinical studies of CAR NK therapy and a list of finished and ongoing clinical trials. For achieving CAR NK products with higher efficacy and safety, we discuss current challenges in transduction and expansion of CAR NK cells, CAR NK therapy side effects, and challenges that limit the optimal efficacy of CAR NK cells and recommend possible solutions to enhance the persistence, function, safety, and efficacy of CAR NK cells with a special focus on solid tumors.

"Built-in" PD-1 blocker to rescue NK-92 activity from PD-L1-mediated tumor escape mechanisms

Success of adoptive cell therapy mainly depends on the ability of immune cells to persist and function optimally in the immunosuppressive tumor microenvironment. Although present at the cancer site, immune cells become exhausted and/or inhibited, due to the presence of inhibitory receptors such as PD-L1 on malignant cells. Novel genetic strategies to manipulate the PD1/PD-L1 axis comprise (i) PD-1 reversion where the receptor intracellular domain is replaced with an activating unit, (ii) the use of anti-PD-L1 CAR or (iii) the disruption of the PD-1 gene. We here present an alternative strategy to equip therapeutic cells with a truncated PD-1 (tPD-1) to abrogate PD-1/PD-L1 inhibition. We show that engagement of tPD-1 with PD-L1-positive tumor unleashes NK-92 activity in vitro. Furthermore, this binding was sufficiently strong to induce killing of targets otherwise not recognized by NK-92, thus increasing the range of targets. In vivo treatment with NK-92 tPD-1 cells led to reduced tumor growth and improved survival. Importantly, tPD-1 did not interfere with tumor recognition in PD-L1 negative conditions. Thus, tPD-1 represents a straightforward method for improving antitumor immunity and revealing new targets through PD-L1 positivity.

Increased antitumor efficacy of PD-1-deficient melanoma-specific human lymphocytes

Background

Genome editing offers unique perspectives for optimizing the functional properties of T cells for adoptive cell transfer purposes. So far, PDCD1 editing has been successfully tested mainly in chimeric antigen receptor T (CAR-T) cells and human primary T cells. Nonetheless, for patients with solid tumors, the adoptive transfer of effector memory T cells specific for tumor antigens remains a relevant option, and the use of high avidity T cells deficient for programmed cell death-1 (PD-1) expression is susceptible to improve the therapeutic benefit of these treatments.

Methods

Here we used the transfection of CAS9/sgRNA ribonucleoproteic complexes to edit PDCD1 gene in human effector memory CD8⁺ T cells specific for the melanoma antigen Melan-A. We cloned edited T cell populations and validated PDCD1 editing through sequencing and cytometry in each T cell clone, together with T-cell receptor (TCR) chain’s sequencing. We also performed whole transcriptomic analyses on wild-type (WT) and edited T cell clones. Finally, we documented in vitro and in vivo through adoptive transfer in NOD scid gamma (NSG) mice, the antitumor properties of WT and PD-1KO T cell clones, expressing the same TCR.

Results

Here we demonstrated the feasibility to edit PDCD1 gene in human effector memory melanoma-specific T lymphocytes. We showed that PD-1 expression was dramatically reduced or totally absent on PDCD1-edited T cell clones. Extensive characterization of a panel of T cell clones expressing the same TCR and exhibiting similar functional avidity demonstrated superior antitumor reactivity against a PD-L1 expressing melanoma cell line. Transcriptomic analysis revealed a downregulation of genes involved in proliferation and DNA replication in PD-1-deficient T cell clones, whereas genes involved in metabolism and cell signaling were upregulated. Finally, we documented the superior ability of PD-1-deficient T cells to significantly delay the growth of a PD-L1 expressing human melanoma tumor in an NSG mouse model.

Conclusion

The use of such lymphocytes for adoptive cell transfer purposes, associated with other approaches modulating the tumor microenvironment, would be a promising alternative to improve immunotherapy efficacy in solid tumors.

A deep insight into CRISPR/Cas9 application in CAR-T cell-based tumor immunotherapies

To date, two chimeric antigen receptors (CAR)-T cell products from autologous T cells have been approved by The United States Food and Drug Administration (FDA). The case-by-case autologous T cell generation setting is largely considered as a pivotal restraining cause for its large-scale clinical use because of the costly and prolonged manufacturing procedure. Further, activated CAR-T cells mainly express immune checkpoint molecules, including CTLA4, PD1, LAG3, abrogating CAR-T anti-tumor activity. In addition, CAR-T cell therapy potently results in some toxicity, such as cytokine releases syndrome (CRS). Therefore, the development of the universal allogeneic T cells with higher anti-tumor effects is of paramount importance. Thus, genome-editing technologies, in particular, clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 are currently being used to establish "off-the-shelf" CAR-T cells with robust resistance to immune cell-suppressive molecules. In fact, that simultaneous ablation of PD-1, T cell receptor alpha constant (TRAC or TCR), and also β-2 microglobulin (B2M) by CRISPR-Cas9 technique can support the manufacture of universal CAR-T cells with robust resistance to PD-L1. . Indeed, the ablation of β2M or TARC can severely hinder swift elimination of allogeneic T cells those express foreign HLA-I molecules, and thereby enables the generation of CAR-T cells from allogeneic healthy donors T cells with higher persistence in vivo. Herein, we will deliver a brief overview of the CAR-T cell application in the context of tumor immunotherapy. More importantly, we will discuss recent finding concerning the application of genome editing technologies for preparing universal CAR-T cells or cells that can effectively counter tumor escape, with a special focus on CRISPR-Cas9 technology.

Strengthening the CAR-T cell therapeutic application using CRISPR/Cas9 technology

Adoptive cell immunotherapy with chimeric antigen receptor T (CAR-T) cell has brought a revolutionary means of treatment for aggressive diseases such as hematologic malignancies and solid tumors. Over the last decade, the United States Food and Drug Administration (FDA) approved five types of CAR-T cell therapies for hematologic malignancies, including Idecabtagene vicleucel (Abecma), Lisocabtagene maraleucel (Breyanzi), Brexucabtagene autoleucel (Tecartus), Tisagenlecleucel (Kymriah), and Axicabtagene ciloleucel (Yescarta). Despite outstanding results gained from different clinical trials, CAR-T cell therapy is not free from side effects and toxicities, and needs careful investigations and improvements. Gene-editing technology, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system, has emerged as a promising tool to address some of the CAR-T therapy hurdles. Using CRISPR/Cas9 technology, CAR expression as well as other cellular pathways can be modified in various ways to enhance CAR-T cells antitumor function and persistence in immunosuppressive tumor microenvironment. CRISPR/Cas9 technology can also be used to decrease CAR-T cell toxicities and side effects. Hereby, we discussed the practical challenges and hurdles related to the accuracy, efficiency, efficacy, safety, and delivery of CRISPR/Cas9 technology to the genetically engineered-T cells. Combining of these two state-of-the-art technologies, CRISPR/Cas9 and CAR-T cells, the field of oncology has an extraordinary opportunity to enter a new era of immunotherapy, which offers novel therapeutic options for different types of tumors.

Making Potent CAR T Cells Using Genetic Engineering and Synergistic Agents

Immunotherapies are emerging as powerful weapons for the treatment of malignancies. Chimeric antigen receptor (CAR)-engineered T cells have shown dramatic clinical results in patients with hematological malignancies. However, it is still challenging for CAR T cell therapy to be successful in several types of blood cancer and most solid tumors. Many attempts have been made to enhance the efficacy of CAR T cell therapy by modifying the CAR construct using combination agents, such as compounds, antibodies, or radiation. At present, technology to improve CAR T cell therapy is rapidly developing. In this review, we particularly emphasize the most recent studies utilizing genetic engineering and synergistic agents to improve CAR T cell therapy.

Recent Progress on Immunotherapy for Breast Cancer: Tumor Microenvironment, Nanotechnology and More

Immunotherapy is a major emerging treatment for breast cancer (BC). However, not all breast cancer patients derive benefit from immunotherapy. Predictive biomarkers of immunotherapy, such as tumor mutation burden and tumor-infiltrating lymphocytes, are promising to stratify the patients with BC and optimize the therapeutic effect. Various targets of the immune response pathway have also been explored to expand the modalities of immunotherapy. The use of nanotechnology for the imaging of predictive biomarkers and the combination with other therapeutic modalities presents a number of advantages for the immunotherapy of BC. In this review, we summary the emerging therapeutic modalities of immunotherapy, present prominent examples of immunotherapy in BC, and discuss the future opportunity of nanotechnology in the immunotherapy of BC.

Targeted delivery of CRISPR-Cas9 and transgenes enables complex immune cell engineering

As genome engineering advances cell-based therapies, a versatile approach to introducing both CRISPR-Cas9 ribonucleoproteins (RNPs) and therapeutic transgenes into specific cells would be transformative. Autologous T cells expressing a chimeric antigen receptor (CAR) manufactured by viral transduction are approved to treat multiple blood cancers, but additional genetic modifications to alter cell programs will likely be required to treat solid tumors and for allogeneic cellular therapies. We have developed a one-step strategy using engineered lentiviral particles to introduce Cas9 RNPs and a CAR transgene into primary human T cells without electroporation. Furthermore, programming particle tropism allows us to target a specific cell type within a mixed cell population. As a proof-of-concept, we show that HIV-1 envelope targeted particles to edit CD4⁺ cells while sparing co-cultured CD8⁺ cells. This adaptable approach to immune cell engineering ex vivo provides a strategy applicable to the genetic modification of targeted somatic cells in vivo.

Enhancing CAR-T cell efficacy in solid tumors by targeting the tumor microenvironment

Chimeric antigen receptor (CAR)-T cell therapy has achieved successful outcomes against hematological malignancies and provided a new impetus for treating solid tumors. However, the efficacy of CAR-T cells for solid tumors remains unsatisfactory. The tumor microenvironment has an important role in interfering with and inhibiting the effector function of immune cells, among which upregulated inhibitory checkpoint receptors, soluble suppressive cytokines, altered chemokine expression profiles, aberrant vasculature, complicated stromal composition, hypoxia and abnormal tumor metabolism are major immunosuppressive mechanisms. In this review, we summarize the inhibitory factors that affect the function of CAR-T cells in tumor microenvironment and discuss approaches to improve CAR-T cell efficacy for solid tumor treatment by targeting those barriers.

ShRNA-mediated silencing of PD-1 augments the efficacy of chimeric antigen receptor T cells on subcutaneous prostate and leukemia xenograft

Chimeric antigen receptor T cells (CAR-T) immunotherapy has shown promising clinical results in the treatment of leukemia and lymphoma, but the effectiveness is limited for solid tumors. The PD-1/PD-L1 pathway is a key immunosuppressive mechanism for cancer cells to avoid eradication by CAR-T cells. In this study, the shRNA (short hair RNA) gene-silencing technique was used to construct the third-generation of CAR-T cells with PD-1 silencing which targeted CD19 antigen (CD19/△PD-1 CAR-T) and prostate stem cell antigen (PSCA/△PD-1 CAR-T), thereby blocking the PD-1/PD-L1 pathway in treatment of lymphoma and prostate subcutaneous xenograft and enhancing the anti-tumor effect of CAR-T cells. The cell experiments showed that PD-1 silencing in CAR-T cells effectively blocked the PD-1 / PD-L1 pathway. When the ratio of effector to target cell is 8:1, △PD-1 CAR-T cells exhibited higher killing ability and cytokine releasing ability than normal CAR-T cells did. The subcutaneous tumor models were constructed using human chronic myelogenous leukemia cells expressing CD19 (K562-CD19) and human prostate cancer cells expressing PSCA (PC3-PSCA), and treated with CD19/△PD-1 CAR-T and PSCA/△PD-1 CAR-T cells, respectively. The tumor volumes significantly reduced within one week, indicating the good tumor growth inhibitory effect of △PD-1 CAR-T cells. Mice injected with △PD-1 CAR-T cells showed a significantly prolonged survival time compared to those with normal CAR-T cells. This study proved that shRNA-mediated PD-1 silencing technology is an effective strategy for blocking the PD-1/PD-L1 immunosuppression pathway and enhancing the therapeutic effect of CAR-T cells on subcutaneous xenograft. SUMMARY: The effect of CAR-T in treating solid tumors has not been as successful as that in hematological malignancies. The key immunosuppressive mechanism is the expression of PD-1/PD-L1. We used gene silencing technique mediated by shRNA (short hair RNA) to block the PD-1/PD-L1 pathway in lymphoma and prostate tumors, thus enhancing the anti-tumor effect of CAR-T cells on subcutaneous xenograft.

Delivery technologies for T cell gene editing: Applications in cancer immunotherapy

While initial approaches to adoptive T cell therapy relied on the identification and expansion of rare tumour-reactive T cells, genetic engineering has transformed cancer immunotherapy by enabling the modification of primary T cells to increase their therapeutic potential. Specifically, gene editing technologies have been utilized to create T cell populations with improved responses to antigens, lower rates of exhaustion, and potential for use in allogeneic applications. In this review, we provide an overview of T cell therapy gene editing strategies and the delivery technologies utilized to genetically engineer T cells. We also discuss recent investigations and clinical trials that have utilized gene editing to enhance the efficacy of T cells and broaden the application of cancer immunotherapies.

CAR-T in Cancer Treatment: Develop in Self-Optimization, Win-Win in Cooperation

Simple Summary

Chimeric antigen receptor (CAR)-T cell therapy has exhibited good application prospects in the treatment of hematologic malignancies. However, there are still many unsolved problems, such as the limited antitumor effect of CAR-T on solid tumors and the potential risk of CAR-T therapy in clinical applications. In order to meet these challenges, more and more solutions are proposed. Therefore, in this review, we have discussed the recent breakthroughs in CAR-T therapy for cancer treatment, with an emphasis on the potentially effective CAR-T modifications and combined strategies.

Abstract

Despite remarkable achievements in the treatment of hematologic malignancies, chimeric antigen receptor (CAR)-T cell therapy still faces many obstacles. The limited antitumor activity and persistence of infused CAR-T cells, especially in solid tumors, are the main limiting factors for CAR-T therapy. Moreover, clinical security and accessibility are important unmet needs for the application of CAR-T therapy. In view of these challenges, many potentially effective solutions have been proposed and confirmed. Both the independent and combined strategies of CAR-T therapy have exhibited good application prospects. Thus, in this review, we have discussed the cutting-edge breakthroughs in CAR-T therapy for cancer treatment, with the aim of providing a reference for addressing the current challenges.

CRISPR/Cas9 based genome editing for targeted transcriptional control in triple-negative breast cancer

Breast cancer (BC) is the most common type of cancer in women at the global level and the highest mortality rate has been observed with triple-negative breast cancer (TNBC). Accumulation of genetic lesions an aberrant gene expression and protein degradation are considered to underlie the onset of tumorigenesis and metastasis. Therefore, the challenge to identify the genes and molecules that could be potentially used as potent biomarkers for personalized medicine against TNBC with minimal or no associated side effects. Discovery of the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) arrangement and an increasing repertoire of its new variants has provided a much-needed fillip towards editing TNBC genomes. In this review, we discuss the CRISPR/Cas9 genome editing, CRISPR Technology for diagnosis of (Triple-negative breast cancer) TNBC, Drug Resistance, and potential applications of CRISPR/Cas9 and its variants in deciphering or engineering intricate molecular and epigenetic mechanisms associated with TNBC. Furthermore, we have also explored the TNBC and CRISPR/Cas9 genome editing potential for repairing, genetic modifications in TNBC.

Programmed cell death protein-1 inhibitor combined with chimeric antigen receptor T cells in the treatment of relapsed refractory non-Hodgkin lymphoma: A case report

BACKGROUND

Chimeric antigen receptor T cell (CART) therapy has benefited many refractory lymphoma patients, but some patients experience poor effects. Previous studies have shown that programmed cell death protein-1 (PD-1) inhibitors can improve and prolong the therapeutic effect of CAR-T cell treatment.

CASE SUMMARY

A 61-year-old male presented with 15-d history of diarrhea and lower-limb edema. A large mass was detected in the pelvis, and pathology indicated non-Hodgkin diffuse large B-cell lymphoma. After three cycles of the R-CHOP chemotherapeutic regimen, the patient showed three subcutaneous nodules under the left armpit and both sides of the cervical spine. Pathological examination of the nodules indicated DLBCL again. The patient was diagnosed with relapsed and refractory diffuse large B-cell lymphoma. We recommended CAR-T cell treatment. Before treatment, the patient’s T cell function and expression of immune detection points were tested. Expression of PD-1 was obviously increased (52.7%) on cluster of differentiation (CD)3+ T cells. The PD-1 inhibitor (3 mg/kg) was infused prior to lymphodepleting chemotherapy with fludarabine and cyclophosphamide. CAR-CD19 T cells of 3 × 10⁶/kg and CAR-CD22 T cells 1 × 10⁶/kg were infused, respectively. The therapeutic effect was significant, and the deoxyribonucleic acid copy numbers of CAR-CD19 T cells and CAR-CD22 T cells were stable. Presently, the patient has been disease-free for more than 12 mo.

CONCLUSION

This case suggests that the combination of PD-1 inhibitors and CAR-T cells improved therapeutic efficacy in B-cell lymphoma.

Arming Immune Cells for Battle: A Brief Journey through the Advancements of T and NK Cell Immunotherapy

Simple Summary

This review is intended to provide an overview on the history and recent advances of T cell and natural killer (NK) cell-based immunotherapy. While the thymus was discovered as the origin of T cells in the 1960s, and NK cells were first described in 1975, the clinical application of adoptive cell therapies (ACT) only began in the early 1980s with the first lymphokine activated killer (LAK) cell product for the treatment of cancer patients. Over the past decades, further immunotherapies have been developed, including ACT using cytokine-induced killer (CIK) cells, products based on the NK cell line NK-92 as well as specific T and NK cell preparations. Recent advances have successfully improved the effectiveness of T, NK, CIK or NK-92 cells towards tumor-targeting antigens generated by genetic engineering of the immune cells. Herein, we summarize the promising development of ACT over the past decades in the fight against cancer.

Abstract

The promising development of adoptive immunotherapy over the last four decades has revealed numerous therapeutic approaches in which dedicated immune cells are modified and administered to eliminate malignant cells. Starting in the early 1980s, lymphokine activated killer (LAK) cells were the first ex vivo generated NK cell-enriched products utilized for adoptive immunotherapy. Over the past decades, various immunotherapies have been developed, including cytokine-induced killer (CIK) cells, as a peripheral blood mononuclear cells (PBMCs)-based therapeutic product, the adoptive transfer of specific T and NK cell products, and the NK cell line NK-92. In addition to allogeneic NK cells, NK-92 cell products represent a possible “off-the-shelf” therapeutic concept. Recent approaches have successfully enhanced the specificity and cytotoxicity of T, NK, CIK or NK-92 cells towards tumor-specific or associated target antigens generated by genetic engineering of the immune cells, e.g., to express a chimeric antigen receptor (CAR). Here, we will look into the history and recent developments of T and NK cell-based immunotherapy.

Engineering Metabolism of Chimeric Antigen Receptor (CAR) Cells for Developing Efficient Immunotherapies

Chimeric antigen receptor (CAR) T cell-based therapies have shown tremendous advancement in clinical and pre-clinical studies for the treatment of hematological malignancies, such as the refractory of pre-B cell acute lymphoblastic leukemia (B-ALL), chronic lymphocytic leukemia (CLL), and large B cell lymphoma (LBCL). However, CAR T cell therapy for solid tumors has not been successful clinically. Although, some research efforts, such as combining CARs with immune checkpoint inhibitor-based therapy, have been used to expand the application of CAR T cells for the treatment of solid tumors. Importantly, further understanding of the coordination of nutrient and energy supplies needed for CAR T cell expansion and function, especially in the tumor microenvironment (TME), is greatly needed. In addition to CAR T cells, there is great interest in utilizing other types of CAR immune cells, such as CAR NK and CAR macrophages that can infiltrate solid tumors. However, the metabolic competition in the TME between cancer cells and immune cells remains a challenge. Bioengineering technologies, such as metabolic engineering, can make a substantial contribution when developing CAR cells to have an ability to overcome nutrient-paucity in the solid TME. This review introduces technologies that have been used to generate metabolically fit CAR-immune cells as a treatment for hematological malignancies and solid tumors, and briefly discusses the challenges to treat solid tumors with CAR-immune cells.

Applications of CRISPR Genome Editing to Advance the Next Generation of Adoptive Cell Therapies for Cancer

Adoptive cell therapy (ACT) for cancer shows tremendous potential; however, several challenges preclude its widespread use. These include poor T-cell function in hostile tumor microenvironments, a lack of tumor-specific target antigens, and the high cost and poor scalability of cell therapy manufacturing. Creative genome-editing strategies are beginning to emerge to address each of these limitations, which has initiated the next generation of cell therapy products now entering clinical trials. CRISPR is at the forefront of this revolution, offering a simple and versatile platform for genetic engineering. This review provides a comprehensive overview of CRISPR applications that have advanced ACT. SIGNIFICANCE: The clinical impact of ACT for cancer can be expanded by implementing specific genetic modifications that enhance the potency, safety, and scalability of cellular products. Here we provide a detailed description of such genetic modifications, highlighting avenues to enhance the therapeutic efficacy and accessibility of ACT for cancer. Furthermore, we review high-throughput CRISPR genetic screens that have unveiled novel targets for cell therapy enhancement.

Using CRISPR to enhance T cell effector function for therapeutic applications

T cells are critical to fight pathogenic microbes and combat malignantly transformed cells in the fight against cancer. To exert their effector function, T cells produce effector molecules, such as the pro-inflammatory cytokines IFN-γ, TNF-α and IL-2. Tumors possess many inhibitory mechanisms that dampen T cell effector function, limiting the secretion of cytotoxic molecules. As a result, the control and elimination of tumors is impaired. Through recent advances in genomic editing, T cells can now be successfully modified via CRISPR/Cas9 technology. For instance, engaging (post-)transcriptional mechanisms to enhance T cell cytokine production, the retargeting of T cell antigen specificity or rendering T cells refractive to inhibitory receptor signaling can augment T cell effector function. Therefore, CRISPR/Cas9-mediated genome editing might provide novel strategies for cancer immunotherapy. Recently, the first-in-patient clinical trial was successfully performed with CRISPR/Cas9-modified human T cell therapy. In this review, a brief overview of currently available techniques is provided, and recent advances in T cell genomic engineering for the enhancement of T cell effector function for therapeutic purposes are discussed.

Emerging Immunotherapies against Novel Molecular Targets in Breast Cancer

Immunotherapy is a highly emerging form of breast cancer therapy that enables clinicians to target cancers with specific receptor expression profiles. Two popular immunotherapeutic approaches involve chimeric antigen receptor-T cells (CAR-T) and bispecific antibodies (BsAb). Briefly mentioned in this review as well is the mRNA vaccine technology recently popularized by the COVID-19 vaccine. These forms of immunotherapy can highly select for the tumor target of interest to generate specific tumor lysis. Along with improvements in CAR-T, bispecific antibody engineering, and therapeutic administration, much research has been done on novel molecular targets that can especially be useful for triple-negative breast cancer (TNBC) immunotherapy. Combining emerging immunotherapeutics with tumor marker discovery sets the stage for highly targeted immunotherapy to be the future of cancer treatments. This review highlights the principles of CAR-T and BsAb therapy, improvements in CAR and BsAb engineering, and recently identified human breast cancer markers in the context of in vitro or in vivo CAR-T or BsAb treatment.

CD19 CAR-T expressing PD-1/CD28 chimeric switch receptor as a salvage therapy for DLBCL patients treated with different CD19-directed CAR T-cell therapies

CD19-targeted chimeric antigen receptor T (CAR T) cell therapy is a promising option to treat relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). However, the majority of CAR T-treated patients will eventually progress and require salvage treatment, for which there is no current standard. In this study, we analyzed data from 6 patients with R/R DLBCL who experienced progression following CD19-CAR T therapy, and then received CD19-specific CAR T cells that express a PD-1/CD28 chimeric switch-receptor (CD19-PD-1/CD28-CAR T) as salvage therapy at our institution. After the second infusion of CAR T cells, 3 of 6 patients achieved complete remissions and the duration of the response of responsive patients ranged from 8 to 25 months. One patient showed a stable disease. In contrast, 2/6 patients died on 60 days because of progression disease. Importantly, no severe neurologic toxicity or cytokine release syndrome was observed. These data suggest that CD19-PD-1/CD28-CAR-T cells, a novel anti-CD19 CAR-T cell therapy, elicit a potent and durable anticancer response, and can be used in the post-CD19-CAR T failure setting.

Anti-Mesothelin CAR T cell therapy for malignant mesothelioma

Malignant mesothelioma (MM) is a treatment-resistant tumor originating in the mesothelial lining of the pleura or the abdominal cavity with very limited treatment options. More effective therapeutic approaches are urgently needed to improve the poor prognosis of MM patients. Chimeric Antigen Receptor (CAR) T cell therapy has emerged as a novel potential treatment for this incurable solid tumor. The tumor-associated antigen mesothelin (MSLN) is an attractive target for cell therapy in MM, as this antigen is expressed at high levels in the diseased pleura or peritoneum in the majority of MM patients and not (or very modestly) present in healthy tissues. Clinical trials using anti-MSLN CAR T cells in MM have shown that this potential therapeutic is relatively safe. However, efficacy remains modest, likely due to the MM tumor microenvironment (TME), which creates strong immunosuppressive conditions and thus reduces anti-MSLN CAR T cell tumor infiltration, efficacy and persistence. Various approaches to overcome these challenges are reviewed here. They include local (intratumoral) delivery of anti-MSLN CAR T cells, improved CAR design and co-stimulation, and measures to avoid T cell exhaustion. Combination therapies with checkpoint inhibitors as well as oncolytic viruses are also discussed. Preclinical studies have confirmed that increased efficacy of anti-MSLN CAR T cells is within reach and offer hope that this form of cellular immunotherapy may soon improve the prognosis of MM patients.

αPD-1-mesoCAR-T cells partially inhibit the growth of advanced/refractory ovarian cancer in a patient along with daily apatinib

Epithelial ovarian cancer (EOC) is the leading cause of death among gynecological malignancies in China. In particular, advanced/refractory ovarian cancer lacks effective targeted therapies due to the immunosuppressive and proangiogenic tumor microenvironment. Mesothelin (MSLN) has been found to be highly expressive in most EOC. Targeting MSLN by antibodies or chimeric antigen receptor-modified T (CAR-T) cells and immune checkpoint blockades as well as apatinib, an anti-angiogenic drug, have been used in patients with refractory ovarian cancer. Apatinib was reported to promote the infiltration of CD8⁺ T cells in lung cancer. However, the combination therapy of CAR-T secreting anti-PD-1 antibody with apatinib in EOC has not been reported.

CASE PRESENTATION

Here we report a case of refractory EOC in a patient who had relapsed after multiline chemotherapy. The patient received autologous T cells that contained sequences encoding single-chain variable fragments specific for MSLN and full-length antibody for PD-1 (αPD-1). The modified T cells were called αPD-1-mesoCAR-T cells. After infusion, the copy number and PD-1 antibody secretion of the CAR-T cells were increased in the blood. By application of multimodality tumor tracking, MRI of the liver showed shrinkage of metastatic nodules from average diameter of 71.3-39.1 mm at month 2. The patient achieved partial response and survived more than 17 months. IL-6 levels in the patient fluctuated from the baseline to 2-4-folds after treatment, but side effects were mild with only grade 1 hypertension and fatigue.

CONCLUSION

αPD-1-mesoCAR-T cell therapy combined with apatinib demonstrates a potential therapeutic effect on advanced refractory ovarian cancer.

TRIAL REGISTRATION NUMBER

NCT03615313.

Enhanced anti-tumor efficacy of IL-7/CCL19-producing human CAR-T cells in orthotopic and patient-derived xenograft tumor models

Chimeric antigen receptor (CAR)-T cell therapy has impressive efficacy in hematological malignancies, but its application in solid tumors remains a challenge. Multiple hurdles associated with the biological and immunological features of solid tumors currently limit the application of CAR-T cells in the treatment of solid tumors. Using syngeneic mouse models, we recently reported that CAR-T cells engineered to concomitantly produce interleukin (IL)-7 and chemokine (C-C motif) ligand 19 (CCL19)-induced potent anti-tumor efficacy against solid tumors through an improved ability of migration and proliferation even in an immunosuppressive tumor microenvironment. In this study, for a preclinical evaluation preceding clinical application, we further explored the potential of IL-7/CCL19-producing human CAR-T cells using models that mimic the clinical features of solid tumors. Human anti-mesothelin CAR-T cells producing human IL-7/CCL19 achieved complete eradication of orthotopic pre-established malignant mesothelioma and prevented a relapse of tumors with downregulated antigen expression. Moreover, mice with patient-derived xenograft of mesothelin-positive pancreatic cancers exhibited significant inhibition of tumor growth and prolonged survival following treatment with IL-7/CCL19-producing CAR-T cells, compared to treatment with conventional CAR-T cells. Transfer of IL-7/CCL19-producing CAR-T cells resulted in an increase in not only CAR-T cells but also non-CAR-T cells within the tumor tissues and downregulated the expression of exhaustion markers, including PD-1 and TIGIT, on the T cells. Taken together, our current study elucidated the exceptional anti-tumor efficacy of IL-7/CCL19-producing human CAR-T cells and their potential for clinical application in the treatment of patients with solid tumors.

Genome editing of immune cells using CRISPR/Cas9

The ability to read, write, and edit genomic information in living organisms can have a profound impact on research, health, economic, and environmental issues. The CRISPR/Cas system, recently discovered as an adaptive immune system in prokaryotes, has revolutionized the ease and throughput of genome editing in mammalian cells and has proved itself indispensable to the engineering of immune cells and identification of novel immune mechanisms. In this review, we summarize the CRISPR/Cas9 system and the history of its discovery and optimization. We then focus on engineering T cells and other types of immune cells, with emphasis on therapeutic applications. Last, we describe the different modifications of Cas9 and their recent applications in the genome-wide screening of immune cells.

Establishment of a cell processing laboratory to support hematopoietic stem cell transplantation and chimeric antigen receptor (CAR)-T cell therapy

Cell processing laboratories are an important part of cancer treatment centers. Cell processing laboratories began by supporting hematopoietic stem cell (HSC) transplantation programs. These laboratories adapted closed bag systems, centrifuges, sterile connecting devices and other equipment used in transfusion services/blood banks to remove red blood cells and plasma from marrow and peripheral blood stem cells products. The success of cellular cancer immunotherapies such as Chimeric Antigen Receptor (CAR) T-cells has increased the importance of cell processing laboratories. Since many of the diseases successfully treated by CAR T-cell therapy are also treated by HSC transplantation and since HSC transplantation teams are well suited to manage patients treated with CAR T-cells, many cell processing laboratories have begun to produce CAR T-cells. The methods that have been used to process HSCs have been modified for T-cell enrichment, culture, stimulation, transduction and expansion for CAR T-cell production. While processing laboratories are well suited to manufacture CAR T-cells and other cellular therapies, producing these therapies is challenging. The manufacture of cellular therapies requires specialized facilities which are costly to build and maintain. The supplies and reagents, especially vectors, can also be expensive. Finally, highly skilled staff are required. The use of automated equipment for cell production may reduce labor requirements and the cost of facilities. The steps used to produce CAR T-cells are reviewed, as well as various strategies for establishing a laboratory to manufacture these cells.

CAR-T cells for Colorectal Cancer: Target-selection and strategies for improved activity and safety

Chimeric antigen receptor-T (CAR-T) cell immunotherapy is a novel method that is genetically engineered to recruit T cells against malignant disease. Administration of CAR-T cells has led to progress in hematological malignancies, and it has been proposed for solid tumors like colorectal cancer (CRC) for years. However, this method was not living up to expectations for the intrinsic challenges posed to CAR-T cells by solid tumors, which mainly due to the lacking of tumor-restricted antigens and adverse effects following treatment. New approaches are proposed to overcome the multiple challenges to alleviate the difficult situation of CAR-T cells in CRC, including engineering T cells with immune-activating molecules, regional administration of T cell, bispecific T cell engager, and combinatorial target-antigen recognition. In this review, we sum up the current stage of knowledge about target-selection, adverse events like on/off-tumor toxicity, the preclinical and clinical studies of CAR-T therapy, and the characteristics of strategies applied in CRC.

Tumor-tagging by oncolytic viruses: A novel strategy for CAR-T therapy against solid tumors

Chimeric antigen receptor (CAR) T cell therapy is one of the most promising immunotherapies in the past decade. It brings hope for cure to patients with previously refractory hematological malignancies. However, when translating this strategy into non-hematologic malignancies, the antitumor activity from multiple clinical studies seemed to be subtle or transient. The less satisfying efficacy in solid tumors might at least due to antigen heterogeneity, suboptimal CAR-T cell trafficking and tumor immunosuppressive environment. Here, we will review the updating strategies to challenge the therapeutic impediments of CAR-T therapy in non-hematologic malignancies. We mainly focus on the combination with oncolytic viruses (OV), the born allies for CAR-T cells. In addition to previously reported OVs-arming strategy, we discuss recently proposed tumor-tagging concept by OVs as CAR-T targets, as well as the possible improvements. Overall, tumor-tagging strategy by OVs combination with CAR-T would be a novel and promising solution for the heterogeneity and immunosuppressive microenvironment of solid tumors.

Fourth-generation chimeric antigen receptor T cells targeting folate receptor alpha antigen expressed on breast cancer cells for adoptive T cell therapy

PURPOSE

Treatment of breast cancer (BC) by standard methods is effective in the early stage, but ineffective in the advanced stage of disease. To develop an adoptive T cell therapy for advanced and severe BC, we generated fourth-generation chimeric antigen receptor (CAR) T cells targeting folate receptor alpha antigen (FRα) expressed on BC cells, and preclinically evaluated their anti-BC activities.

METHODS

The fourth-generation FRα-CAR T cells containing extracellular FRα-specific single-chain variable fragment (scFv) and three intracellular costimulatory domains (CD28, 4-1BB, and CD27) linked to CD3ζ were generated using a lentiviral system, and then were evaluated for their anti-BC activities in two-dimensional and three-dimensional (spheroid) cultures.

RESULTS

When our fourth-generation FRα-CAR T cells were cocultured with FRα-expressing MDA-MB-231 BC cell line at an effector to target ratio of 20:1, these CAR T cells specifically lysed 88.7 ± 10.6% of the target cells. Interestingly, the cytotoxic lysis of FRα-CAR T cells was more pronounced in target cells with higher surface FRα expression. This specific cytotoxicity of the CAR T cells was not observed when cocultured with FRα-negative MCF10A normal breast-like cell line at the same ratio (34.3 ± 4.7%). When they were cocultured with MDA-MD-231 spheroid, the FRα-CAR T cells exhibited antitumor activity marked with spheroid size reduction and breakage.

CONCLUSION

This proof-of-concept study thus shows the feasibility of using these fourth-generation FRα-CAR T cells for adoptive T cell therapy in BC.

Genome editing of immune cells using CRISPR/Cas9

The ability to read, write, and edit genomic information in living organisms can have a profound impact on research, health, economic, and environmental issues. The CRISPR/Cas system, recently discovered as an adaptive immune system in prokaryotes, has revolutionized the ease and throughput of genome editing in mammalian cells and has proved itself indispensable to the engineering of immune cells and identification of novel immune mechanisms. In this review, we summarize the CRISPR/ Cas9 system and the history of its discovery and optimization. We then focus on engineering T cells and other types of immune cells, with emphasis on therapeutic applications. Last, we describe the different modifications of Cas9 and their recent applications in the genome-wide screening of immune cells. [BMB Reports 2021; 54(1): 59-69].

PD-1 silencing improves anti-tumor activities of human mesothelin-targeted CAR T cells

Chimeric antigen receptor T (CAR T) cell therapy is a new pillar in cancer therapeutics, and has been successfully used for the treatment of cancers, including acute lymphoblastic leukemia and solid cancers. Following immune attack, many tumors upregulate inhibitory ligands which bind to inhibitory receptors on T cells. For example, the interaction between programmed cell death protein 1 (PD-1) on activated T cells and its ligands (widely known as PD-L1) on a target tumor limits the efficacy of CAR T cells therapy against poorly responding tumors. Here, we use mesothelin (MSLN)-expressing human ovarian cancer cells (SKOV3) and human colon cancer cells (HCT116) to investigate whether PD-1-mediated T cell exhaustion affects the anti-tumor activity of MSLN-targeted CAR T cells. We utilized cell-intrinsic PD-1-targeting shRNA overexpression strategy, resulting in a significant PD-1 silencing in CAR T cells. The reduction of PD-1 expression on T cell surface strongly augmented CAR T cell cytokine production and cytotoxicity towards PD-L1-expressing cancer cells in vitro. This study indicates the enhanced anti-tumor efficacy of PD-1-silencing MSLN-targeted CAR T cells against several cancers and suggests the potential of other specific gene silencing on the immune checkpoints to enhance the CAR T cell therapies against human tumors.

Modified nanoscale metal organic framework-based nanoplatforms in photodynamic therapy and further applications

Photodynamic therapy (PDT) has emerged as a modality in cancer treatment because it is less invasive and highly selective compared with conventional chemotherapy and radiation therapy. Nanoscale metal organic frameworks (nMOFs) have exhibited great potential for use in constructing nanoplatforms for improved PDT because of their unique structural advantages such as large surface areas, high porosities, tunable compositions and various other modifications. The large majority of current nMOF-based systems employ specific modifying groups to overcome the deficiencies previously observed when using older nMOFs in PDT. In this review, we summarize modifications to these systems such as enhancing singlet oxygen generation by introducing photoactive agents, alleviating tumor hypoxia and engineering active targeting abilities. The applications of MOF-based nanoparticles in synergistic cancer therapies that include PDT, as well as in theranostics are also discussed. Finally, we discuss some of the challenges faced in this field and the future prospects for the use of nMOFs in PDT.

Improving Cancer Immunotherapy with CRISPR-Based Technology

The rapidly evolving field of immunotherapy has attracted great attention in the field of cancer research and already revolutionized the clinical practice standard for treating cancer. Genetically engineered T cells expressing either T cell receptors or chimeric antigen receptors represent novel treatment modalities and are considered powerful weapons to fight cancer. The immune checkpoint blockade, which harnesses the negative control signaling behind the anti-tumor immune response with therapeutic antibodies by blocking cytotoxic T lymphocyte-associated protein 4 or the programmed cell death 1 pathways are another mainstream direction for cancer immunotherapy. In addition to cytotoxic T cells, other immune cell types such as nature killer cells and macrophages also possess the ability to eradicate cancer cells, which may serve as the basis to develop novel cancer immunotherapies. The advent of cutting-edge genome editing technology, especially clustered regularly interspaced palindromic repeats (CRISPR)-based tools, has greatly expedited many biomedical research areas, including cancer immunology and immunotherapy. In this review, the contribution of current CRISPR techniques to basic and translational cancer immunology research is discussed, and the future for cancer immunotherapy in the age of CRISPR is predicted.

Progress and challenges in CRISPR-mediated therapeutic genome editing for monogenic diseases

There are an estimated 10 000 monogenic diseases affecting tens of millions of individuals worldwide. The application of CRISPR/Cas genome editing tools to treat monogenic diseases is an emerging strategy with the potential to generate personalized treatment approaches for these patients. CRISPR/Cas-based systems are programmable and sequence-specific genome editing tools with the capacity to generate base pair resolution manipulations to DNA or RNA. The complexity of genomic insults resulting in heritable disease requires patient-specific genome editing strategies with consideration of DNA repair pathways, and CRISPR/Cas systems of different types, species, and those with additional enzymatic capacity and/or delivery methods. In this review we aim to discuss broad and multifaceted therapeutic applications of CRISPR/Cas gene editing systems including in harnessing of homology directed repair, non-homologous end joining, microhomology-mediated end joining, and base editing to permanently correct diverse monogenic diseases.

Hereditary diffuse gastric cancer therapeutic roadmap: current and novel approaches in a nutshell

Hereditary diffuse gastric cancer (HDGC) is a rare malignancy characterized by autosomal dominant inheritance of pathological variants of the CDH1 gene encoding E-cadherin, which is involved in cell–cell adhesion, maintenance of epithelial architecture, tumor suppression, and regulation of intracellular signaling pathways. Late-stage recognition of HDGC is typically associated with a poor clinical outcome due to its metastatic potential and risk of lobular breast cancer (LBC) development. The American College of Gastroenterology issued guidelines to evaluate HDGC, test for CDH1 genetic variants, and recommend prophylactic gastrectomy for carriers of CDH1 mutations. If surgery is not pursued, endoscopy is a surveillance alternative, although it carries a limited ability to detect malignant foci. As part of clinical research efforts, novel endoscopy advances are currently studied, and a center of excellence for HDGC was created for a comprehensive multidisciplinary team approach. Within this review, we cover current conventional treatment modalities such as gastrectomy and chemotherapy, as the mainstay treatments, in addition to Pembrolizumab, an immune checkpoint inhibitor, as the last therapeutic resort. We also shed light on novel and promising approaches with emphasis on immunotherapy to treat HDGC. We further break down the therapeutic paradigms to utilize molecular tools, antibodies against checkpoint inhibitors, TGF-β and tyrosine kinase inhibitors, cell-based adoptive therapies, and oncolytic viral therapies. We aim to expand the understanding on how to modulate the tumor microenvironment to tip the balance towards an anti-tumor phenotype, prevent metastasis of the primary disease, and potentially alter the therapeutic landscape for HDGC.

Mesothelin-targeted CAR-T cell therapy for solid tumors

Introduction: Mesothelin (MSLN) is a tumor differentiation antigen normally restricted to the body's mesothelial surfaces, but significantly overexpressed in a broad range of solid tumors. For this reason, MSLN has emerged as an important target for the development of novel immunotherapies. This review focuses on anti-MSLN chimeric antigen receptor (CAR) T cell immunotherapy approaches.Areas covered: A brief overview of MSLN as a therapeutic target and existing anti-MSLN antibody-based drugs and vaccines is provided. A detailed account of anti-MSLN CAR-T cell approaches utilized in preclinical models is presented. Finally, a comprehensive summary of currently ongoing and completed anti-MSLN CAR-T cell clinical trials is discussed.Expert opinion: Initial trials using anti-MSLN CAR-T cells have been safe, but efficacy has been limited. Employing regional routes of delivery, introducing novel modifications leading to enhanced tumor infiltration and persistence, and improved safety profiles and combining anti-MSLN CAR-T cells with standard therapies, could render them more efficacious in the treatment of solid malignancies.

Mutation of PD-1 immune receptor tyrosine-based switch motif (ITSM) enhances the antitumor activity of cytotoxic T cells

BACKGROUND

Programmed cell death protein 1 (PD-1), as an immune checkpoint cell membrane receptor, negatively regulates T cell activation via its immune receptor, the tyrosine-based switch motif (ITSM). The purpose of this research was to evaluate the antitumor activity T cells with the ITSM mutation of PD-1 on non-small cell lung cancer (NSCLC) in vitro and in vivo.

METHODS

In this study, the tyrosine of ITSM in cytotoxic T cells was mutated using the adenine base editor (ABE)-xCas9 system to evaluate its effect on the antitumor activity of T cells against NSCLC.

RESULTS

Results showed that the PD-1-deficient T cells enhanced the death of the cocultured NSCLC cells compared with the normal T cells and saline solution. PD-1-deficient T cells also changed the interleukin 2(IL-2), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) secretion of T cells compared with those of the normal T cells. The effectiveness of ITSM mutation in enhancing the antitumor activity of PD-1-deficient T cells was verified in vivo by using a mouse xenograft model. The xenografted mice treated with PD-1-deficient T cells demonstrated repressed tumor growth of the NSCLC cells compared with those treated with normal T cells and saline solution.

CONCLUSIONS

The mutation of ITSM in cytotoxic T cell via the ABE-xCas9 system can significantly enhance the antitumor activity of T cells.

SJI 2020 special issue: A catalogue of Ovarian Cancer targets for CAR therapy

Ovarian Cancer (OC) is currently difficult to cure, mainly due to its late detection and the advanced state of the disease at the time of diagnosis. Therefore, conventional treatments such as debulking surgery and combination chemotherapy are rarely able to control progression of the tumour, and relapses are frequent. Alternative therapies are currently being evaluated, including immunotherapy and advanced T cell-based therapy. In the present review, we will focus on a description of those Chimeric Antigen Receptors (CARs) that have been validated in the laboratory or are being tested in the clinic. Numerous target antigens have been defined due to the identification of OC biomarkers, and many are being used as CAR targets. We provide an exhaustive list of these constructs and their current status. Despite being innovative and efficient, the OC-specific CARs face a barrier to their clinical efficacy: the tumour microenvironment (TME). Indeed, effector cells expressing CARs have been shown to be severely inhibited, rendering the CAR T cells useless once at the tumour site. Herein, we give a thorough description of the highly immunosuppressive OC TME and present recent studies and innovations that have enabled CAR T cells to counteract this negative environment and to destroy tumours.

Lentiviral delivery of combinatorial CAR/CRISPRi circuit into human primary T cells is enhanced by TBK1/IKKɛ complex inhibitor BX795

Background

Adoptive transfer of engineered immune cells is a promising strategy for cancer treatment. However, low transduction efficiency particularly when large payload lentiviral vectors are used on primary T cells is a limitation for the development of cell therapy platforms that include multiple constructs bearing long DNA sequences. RB-340-1 is a new CAR T cell that combines two strategies in one product through a CRISPR interference (CRISPRi) circuit. Because multiple regulatory components are included in the circuit, RB-340-1 production needs delivery of two lentiviral vectors into human primary T cells, both containing long DNA sequences. To improve lentiviral transduction efficiency, we looked for inhibitors of receptors involved in antiviral response. BX795 is a pharmacological inhibitor of the TBK1/IKKɛ complex, which has been reported to augment lentiviral transduction of human NK cells and some cell lines, but it has not been tested with human primary T cells. The purpose of this study was to test if BX795 treatment promotes large payload RB-340-1 lentiviral transduction of human primary T cells.

Methods

To make the detection of gene delivery more convenient, we constructed another set of RB-340-1 constructs containing fluorescent labels named RB-340-1F. We incorporated BX795 treatment into the human primary T cell transduction procedure that was optimized for RB-340-1F. We tested BX795 with T cells collected from multiple donors, and detected the effect of BX795 on T cell transduction, phenotype, cell growth and cell function.

Results

We found that BX795 promotes RB-340-1F lentiviral transduction of human primary T cells, without dramatic change in cell growth and T cell functions. Meanwhile, BX795 treatment increased CD8+ T cell ratios in transduced T cells.

Conclusions

These results indicate that BX795 treatment is effective, and might be a safe approach to promote RB-340-1F lentiviral transduction of human primary T cells. This approach might also be helpful for other T cell therapy products that need delivery of complicated platform via large payload lentiviral vectors.

CAR T Cell Therapy for Solid Tumors: Bright Future or Dark Reality?

Chimeric antigen receptor (CAR) T cell therapy has garnered significant excitement due to its success for hematological malignancies in clinical studies leading to the US Food and Drug Administration (FDA) approval of three CD19-targeted CAR T cell products. In contrast, the clinical experience with CAR T cell therapy for solid tumors and brain tumors has been less encouraging, with only a few patients achieving complete responses. Clinical and preclinical studies have identified multiple "roadblocks," including (1) a limited array of targetable antigens and heterogeneous antigen expression, (2) limited T cell fitness and survival before reaching tumor sites, (3) an inability of T cells to efficiently traffic to tumor sites and penetrate physical barriers, and (4) an immunosuppressive tumor microenvironment. Herein, we review these challenges and discuss strategies that investigators have taken to improve the effector function of CAR T cells for the adoptive immunotherapy of solid tumors.

CRISPR-Cas, a robust gene-editing technology in the era of modern cancer immunotherapy

Cancer immunotherapy has been emerged as a promising strategy for treatment of a broad spectrum of malignancies ranging from hematological to solid tumors. One of the principal approaches of cancer immunotherapy is transfer of natural or engineered tumor-specific T-cells into patients, a so called "adoptive cell transfer", or ACT, process. Construction of allogeneic T-cells is dependent on the employment of a gene-editing tool to modify donor-extracted T-cells and prepare them to specifically act against tumor cells with enhanced function and durability and least side-effects. In this context, CRISPR technology can be used to produce universal T-cells, equipped with recombinant T cell receptor (TCR) or chimeric antigen receptor (CAR), through multiplex genome engineering using Cas nucleases. The robust potential of CRISPR-Cas in preparing the building blocks of ACT immunotherapy has broaden the application of such therapies and some of them have gotten FDA approvals. Here, we have collected the last investigations in the field of immuno-oncology conducted in partnership with CRISPR technology. In addition, studies that have addressed the challenges in the path of CRISPR-mediated cancer immunotherapy, as well as pre-treatment applications of CRISPR-Cas have been mentioned in detail.

Ready for Repair? Gene Editing Enters the Clinic for the Treatment of Human Disease

We present an overview of clinical trials involving gene editing using clustered interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9), transcription activator-like effector nucleases (TALENs), or zinc finger nucleases (ZFNs) and discuss the underlying mechanisms. In cancer immunotherapy, gene editing is applied ex vivo in T cells, transgenic T cell receptor (tTCR)-T cells, or chimeric antigen receptor (CAR)-T cells to improve adoptive cell therapy for multiple cancer types. This involves knockouts of immune checkpoint regulators such as PD-1, components of the endogenous TCR and histocompatibility leukocyte antigen (HLA) complex to generate universal allogeneic CAR-T cells, and CD7 to prevent self-destruction in adoptive cell therapy. In cervix carcinoma caused by human papillomavirus (HPV), E6 and E7 genes are disrupted using topically applied gene editing machinery. In HIV infection, the CCR5 co-receptor is disrupted ex vivo to generate HIV-resistant T cells, CAR-T cells, or hematopoietic stem cells. In β-thalassemia and sickle cell disease, hematopoietic stem cells are engineered ex vivo to induce the production of fetal hemoglobin. AAV-mediated in vivo gene editing is applied to exploit the liver for systemic production of therapeutic proteins in hemophilia and mucopolysaccharidoses, and in the eye to restore splicing of the CEP920 gene in Leber's congenital amaurosis. Close consideration of safety aspects and education of stakeholders will be essential for a successful implementation of gene editing technology in the clinic.

TCR Redirected T Cells for Cancer Treatment: Achievements, Hurdles, and Goals

Adoptive T cell therapy (ACT) is a rapidly evolving therapeutic approach designed to harness T cell specificity and function to fight diseases. Based on the evidence that T lymphocytes can mediate a potent anti-tumor response, initially ACT solely relied on the isolation, in vitro expansion, and infusion of tumor-infiltrating or circulating tumor-specific T cells. Although effective in a subset of cases, in the first ACT clinical trials several patients experienced disease progression, in some cases after temporary disease control. This evidence prompted researchers to improve ACT products by taking advantage of the continuously evolving gene engineering field and by improving manufacturing protocols, to enable the generation of effective and long-term persisting tumor-specific T cell products. Despite recent advances, several challenges, including prioritization of antigen targets, identification, and optimization of tumor-specific T cell receptors, in the development of tools enabling T cells to counteract the immunosuppressive tumor microenvironment, still need to be faced. This review aims at summarizing the major achievements, hurdles and possible solutions designed to improve the ACT efficacy and safety profile in the context of liquid and solid tumors.

Insights Into the Role of Mesothelin as a Diagnostic and Therapeutic Target in Ovarian Carcinoma

Ovarian malignancies remain the leading cause of death in female gynecological tumors. More than 70% of patients are diagnosed with advanced stage with extensive metastatic lesions in abdominal cavity due to lack of symptoms in early stage and sensitive diagnostic approaches. Mesothelin (MSLN), a glycosylphosphatidylinositol-anchored membrane glycoprotein, participates in cell adhesion, tumor progression, metastasis, and drug resistance. Despite this, the mechanism is still poorly understood. The differential expression pattern of MSLN in normal and cancer tissues makes it a promising target for diagnosis and therapeutic applications. Several clinical trials are underway to evaluate the safety and efficacy of MSLN-targeted drugs, including CAR T cells, immunotoxin, antibody-drug conjugates, and vaccine. This review is aimed to briefly discuss the characteristics of MSLN and the latest progress in MSLN targeting therapies.